Isolation, expression and purification of the hydantoin hydrolysing enzymes of agrobacterium tumefaciens
- Authors: Clark, Sally-Ann
- Date: 2003
- Subjects: Agrobacterium tumefaciens , Amino acids Hydantoin Enzymes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4140 , http://hdl.handle.net/10962/d1016233
- Description: The production of enantiomerically pure amino acids is of industrial importance as they are used in the synthesis of a number of pharmaceuticals, insecticides and herbicides and biologically active peptides and hormones. A number of microorganisms have been identified which possess hydantoin hydrolysing enzymes that stereoselectively convert racemic hydantoins into anantiomerically pure amino acids. Consequently these microorganisms and their enzymes are sought after as biocatalysts for the production of amino acids. The isolation of novel hydantoin hydrolising enzymes with unique or improved biocatalytic characteristics is of importance for the development of potential biocatalysts to be used in the production of enantiomerically pure amino acids. The genes encoding an N-carbamoyl-amino acid amidohydrolase, an enzyme involved in the hydrolysis of hydantoin, was isolated by screening a genomic DNA library of Agrobacterium tumefacience RU-AE01. Nucleotide sequence analysis of the region upstream of this gene revealed a fragment of a gene encoding the hydantoinase enzyme. I this study, a DNA probe consisting of the gene encoding the N-carbamoyl amino acid amidohydrolase, on a large enough fragment of the genomic DNA library which would allow for the simultaneous isolation the hydantoinase gene located upstream. Recombinant expression of the genes encoding hydantoin hydrolysing enzymes has been used to facilitate the production and purification of these enzymes for their use as biocatalysts. Two genes (ncaR1 and ncaR2) encoding different N-carbamoyl-amino acid amidohydrolases with distinct nucleotide and deduced amino acid sequences were isolated from the genome of A, tumefaciens RU-OR. In this study, the heterologous expression of ncaR1 and ncaR2 was explored. Investigation into the optimisation of the heterologous expression of ncaR1 showed that reducing the growth temperature of the recombinant E. coli producing NcaR1 resulted in a two-fold increase in N-carbamoyl-amino acid amidohydrolase activity and solubility. Furthermore, NcaR1 was produced with a C-terminal 6xHis tag, but NcaR1-6xHis did not possess N-carbamoyl amino acid amidohydrolase activity. Furthermore, purification of NcaR-6xHis under native conditions using affinity chromatography performed, and used for the production of antibodies.
- Full Text:
- Date Issued: 2003
- Authors: Clark, Sally-Ann
- Date: 2003
- Subjects: Agrobacterium tumefaciens , Amino acids Hydantoin Enzymes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4140 , http://hdl.handle.net/10962/d1016233
- Description: The production of enantiomerically pure amino acids is of industrial importance as they are used in the synthesis of a number of pharmaceuticals, insecticides and herbicides and biologically active peptides and hormones. A number of microorganisms have been identified which possess hydantoin hydrolysing enzymes that stereoselectively convert racemic hydantoins into anantiomerically pure amino acids. Consequently these microorganisms and their enzymes are sought after as biocatalysts for the production of amino acids. The isolation of novel hydantoin hydrolising enzymes with unique or improved biocatalytic characteristics is of importance for the development of potential biocatalysts to be used in the production of enantiomerically pure amino acids. The genes encoding an N-carbamoyl-amino acid amidohydrolase, an enzyme involved in the hydrolysis of hydantoin, was isolated by screening a genomic DNA library of Agrobacterium tumefacience RU-AE01. Nucleotide sequence analysis of the region upstream of this gene revealed a fragment of a gene encoding the hydantoinase enzyme. I this study, a DNA probe consisting of the gene encoding the N-carbamoyl amino acid amidohydrolase, on a large enough fragment of the genomic DNA library which would allow for the simultaneous isolation the hydantoinase gene located upstream. Recombinant expression of the genes encoding hydantoin hydrolysing enzymes has been used to facilitate the production and purification of these enzymes for their use as biocatalysts. Two genes (ncaR1 and ncaR2) encoding different N-carbamoyl-amino acid amidohydrolases with distinct nucleotide and deduced amino acid sequences were isolated from the genome of A, tumefaciens RU-OR. In this study, the heterologous expression of ncaR1 and ncaR2 was explored. Investigation into the optimisation of the heterologous expression of ncaR1 showed that reducing the growth temperature of the recombinant E. coli producing NcaR1 resulted in a two-fold increase in N-carbamoyl-amino acid amidohydrolase activity and solubility. Furthermore, NcaR1 was produced with a C-terminal 6xHis tag, but NcaR1-6xHis did not possess N-carbamoyl amino acid amidohydrolase activity. Furthermore, purification of NcaR-6xHis under native conditions using affinity chromatography performed, and used for the production of antibodies.
- Full Text:
- Date Issued: 2003
Jane Austen re-visited a feminist evaluation of the longevity and relevance of the Austen Oeuvre
- Authors: Kollmann, Elizabeth
- Date: 2003
- Subjects: Austen, Jane, 1775-1817 -- Criticism and interpretation , Feminist literary criticism
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:10994 , http://hdl.handle.net/10948/299 , Austen, Jane, 1775-1817 -- Criticism and interpretation , Feminist literary criticism
- Description: Although many might consider Jane Austen to be outdated and clichéd, her work retains an undying appeal. During the last decade the English-speaking world has experienced an Austen renaissance as it has been treated to a number of film and television adaptations of her work, including Pride and Prejudice, Emma, Mansfield Park and Sense and Sensibility. Film critics such as Bill De Lapp (1996) and Sherry Dean (1996) have commented on the phenomenal response these productions received and have been amazed by Austen’s ability to compete with current movie scripts. The reasons for viewers and readers enjoying and identifying with Austen’s fiction are numerous. Readers of varying persuasions have different agendas and hence different views and interpretations of Austen. This thesis follows a gynocritical approach and applies a feminist point of view when reading and discussing Austen. Austen’s novels - Pride and Prejudice, Mansfield Park, Emma, Northanger Abbey, Sense and Sensibility, and Persuasion – are re-read and reevaluated from a feminist perspective in order to call attention to Austen’s awareness of women’s second-class position in her society. Women’s experiences in Austen’s time are compared to women’s experiences in society today in order to illustrate, in some way, the tremendous progress the feminist movement has made. In addition, by examining what Austen reveals about the material reality of women in her time, it is possible to explore the legacy that modern women have inherited. Literary critics such as André Brink (1998), Claudia Johnson (1988), and Gilbert and Gubar (1979) believe Austen to create feminist awareness in her novels. There are critics, however, who do not view Austen as necessarily feminist in her writing. Nancy Armstrong writes in Desire and Domestic Fiction (1987) that Austen’s objective is not a critique of the Abstract iv old order but rather a redefinition of wealth and status. In Culture and Imperialism (1993) Edward Said implicates Austen in the rationale for imperial expansion, while Barbara Seeber argues in “The Schooling of Marianne Dashwood” (1999) that Austen’s texts should be understood as dialogic. Others, such as Patricia Beer (1974), believe Austen’s fiction primarily to be about marriage since all her novels end with matrimony. My own reading of Austen takes into consideration her social milieu and patriarchal inheritance. It argues that Austen writes within the framework of patriarchy (for example by marrying off her heroines) possibly because she is aware that in order to survive as a woman (writer) in a male-favouring world and in a publishing world dominated by men, her critique needs to be covert. If read from a feminist perspective, Austen’s fiction draws our attention to issues such as women’s (lack of) education, the effects of not being given access to knowledge, marriage as a patriarchal institution of entrapment, and women’s identity. Her fiction reveals the effects of educating women for a life of domesticity, and illustrates that such an education is biased, leaving women powerless and without any means of self-protection in a male-dominated world. Although contemporary women in the Western world mostly enjoy equal education opportunities to men, they suffer the consequences of a legacy which denied them access to a proper education. Feminist writers such as Flis Henwood (2000) show that contemporary women believe certain areas of expertise belong to men exclusively. Others such as Linda Nochlin (1994) reveal that because women did not have access to higher education for so many years, they failed to produce great women artists like Chaucer or Cézanne. Austen’s fiction also exposes the economic and social system (of which education constitutes a major part) for enforcing marriage and for enfeebling women. In addition, it illustrates some of the realities and pitfalls of marriage. While Austen only subtly refers to Abstract v women’s disempowerment within marriage, contemporary feminist scholars such as Germaine Greer (1999) and Arnot, Araújo, Deliyanni, and Ivinson (2000) explicitly warn women that marriage is a patriarchal institution of entrapment and that it often leaves women feeling unfulfilled. The issue of marriage as a patriarchal institution has been thought important and has been addressed by feminists because it contributes to women’s powerlessness. Feminist scholars today find it imperative to expose all forms of power in order to eradicate women’s subordination. bell hooks comments in Feminist Theory: From Margin to Center (2000) on the importance of revealing unfair power relations in order to eliminate oppression of any kind. Austen does not necessarily express the wish to eradicate forms of power or oppression in her novels. Yet, if we read her work from a feminist point of view, we are made aware of the social construction of power. From her fiction we can infer that male power is enshrined in the very structure of society, and this makes us aware of women’s lack of power in her time. Austen’s novels, however, are not merely novels of powerlessness but of empowerment. By creating rounded women characters and by giving them the power to judge, to refuse and to write, Austen challenges the stereotyped view of woman as either overpowering monster or weak and fragile angel. In addition, her novels seem to question women’s inherited identity and to suggest that qualities such as emotionality and mothering are not natural aspects of being a woman. Because she suggests ways in which women might empower themselves, albeit within patriarchal parameters, one could argue that she contributes, in a small way, to the transformation of existing power relations and to the eradication of women’s servile position in society.
- Full Text:
- Date Issued: 2003
- Authors: Kollmann, Elizabeth
- Date: 2003
- Subjects: Austen, Jane, 1775-1817 -- Criticism and interpretation , Feminist literary criticism
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:10994 , http://hdl.handle.net/10948/299 , Austen, Jane, 1775-1817 -- Criticism and interpretation , Feminist literary criticism
- Description: Although many might consider Jane Austen to be outdated and clichéd, her work retains an undying appeal. During the last decade the English-speaking world has experienced an Austen renaissance as it has been treated to a number of film and television adaptations of her work, including Pride and Prejudice, Emma, Mansfield Park and Sense and Sensibility. Film critics such as Bill De Lapp (1996) and Sherry Dean (1996) have commented on the phenomenal response these productions received and have been amazed by Austen’s ability to compete with current movie scripts. The reasons for viewers and readers enjoying and identifying with Austen’s fiction are numerous. Readers of varying persuasions have different agendas and hence different views and interpretations of Austen. This thesis follows a gynocritical approach and applies a feminist point of view when reading and discussing Austen. Austen’s novels - Pride and Prejudice, Mansfield Park, Emma, Northanger Abbey, Sense and Sensibility, and Persuasion – are re-read and reevaluated from a feminist perspective in order to call attention to Austen’s awareness of women’s second-class position in her society. Women’s experiences in Austen’s time are compared to women’s experiences in society today in order to illustrate, in some way, the tremendous progress the feminist movement has made. In addition, by examining what Austen reveals about the material reality of women in her time, it is possible to explore the legacy that modern women have inherited. Literary critics such as André Brink (1998), Claudia Johnson (1988), and Gilbert and Gubar (1979) believe Austen to create feminist awareness in her novels. There are critics, however, who do not view Austen as necessarily feminist in her writing. Nancy Armstrong writes in Desire and Domestic Fiction (1987) that Austen’s objective is not a critique of the Abstract iv old order but rather a redefinition of wealth and status. In Culture and Imperialism (1993) Edward Said implicates Austen in the rationale for imperial expansion, while Barbara Seeber argues in “The Schooling of Marianne Dashwood” (1999) that Austen’s texts should be understood as dialogic. Others, such as Patricia Beer (1974), believe Austen’s fiction primarily to be about marriage since all her novels end with matrimony. My own reading of Austen takes into consideration her social milieu and patriarchal inheritance. It argues that Austen writes within the framework of patriarchy (for example by marrying off her heroines) possibly because she is aware that in order to survive as a woman (writer) in a male-favouring world and in a publishing world dominated by men, her critique needs to be covert. If read from a feminist perspective, Austen’s fiction draws our attention to issues such as women’s (lack of) education, the effects of not being given access to knowledge, marriage as a patriarchal institution of entrapment, and women’s identity. Her fiction reveals the effects of educating women for a life of domesticity, and illustrates that such an education is biased, leaving women powerless and without any means of self-protection in a male-dominated world. Although contemporary women in the Western world mostly enjoy equal education opportunities to men, they suffer the consequences of a legacy which denied them access to a proper education. Feminist writers such as Flis Henwood (2000) show that contemporary women believe certain areas of expertise belong to men exclusively. Others such as Linda Nochlin (1994) reveal that because women did not have access to higher education for so many years, they failed to produce great women artists like Chaucer or Cézanne. Austen’s fiction also exposes the economic and social system (of which education constitutes a major part) for enforcing marriage and for enfeebling women. In addition, it illustrates some of the realities and pitfalls of marriage. While Austen only subtly refers to Abstract v women’s disempowerment within marriage, contemporary feminist scholars such as Germaine Greer (1999) and Arnot, Araújo, Deliyanni, and Ivinson (2000) explicitly warn women that marriage is a patriarchal institution of entrapment and that it often leaves women feeling unfulfilled. The issue of marriage as a patriarchal institution has been thought important and has been addressed by feminists because it contributes to women’s powerlessness. Feminist scholars today find it imperative to expose all forms of power in order to eradicate women’s subordination. bell hooks comments in Feminist Theory: From Margin to Center (2000) on the importance of revealing unfair power relations in order to eliminate oppression of any kind. Austen does not necessarily express the wish to eradicate forms of power or oppression in her novels. Yet, if we read her work from a feminist point of view, we are made aware of the social construction of power. From her fiction we can infer that male power is enshrined in the very structure of society, and this makes us aware of women’s lack of power in her time. Austen’s novels, however, are not merely novels of powerlessness but of empowerment. By creating rounded women characters and by giving them the power to judge, to refuse and to write, Austen challenges the stereotyped view of woman as either overpowering monster or weak and fragile angel. In addition, her novels seem to question women’s inherited identity and to suggest that qualities such as emotionality and mothering are not natural aspects of being a woman. Because she suggests ways in which women might empower themselves, albeit within patriarchal parameters, one could argue that she contributes, in a small way, to the transformation of existing power relations and to the eradication of women’s servile position in society.
- Full Text:
- Date Issued: 2003
Judicial enforcement of socio-economic rights under the 1996 constitution : realising the vision of social justice
- Authors: Ngcukaitobi, T
- Date: 2003
- Subjects: South Africa. Constitution , South Africa. Bill of Rights , Civil rights -- South Africa , Human rights -- South Africa , South Africa -- Politics and government -- 1994- , South Africa -- Economic conditions -- 1991- , South Africa -- Social conditions -- 1994-
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:3689 , http://hdl.handle.net/10962/d1003204 , South Africa. Constitution , South Africa. Bill of Rights , Civil rights -- South Africa , Human rights -- South Africa , South Africa -- Politics and government -- 1994- , South Africa -- Economic conditions -- 1991- , South Africa -- Social conditions -- 1994-
- Description: Few legal developments in South Africa and elsewhere in the world in recent times have excited such controversy as the legal recognition of social and economic rights. South Africa has created a special place for itself in world affairs for being one of the countries that recognise socio-economic rights in a justiciable Bill of Rights. Partly this is in response to the appalling levels of poverty prevalent in the country which could potentially destabilise the new democracy. Improvement of the quality of life of every citizen is a crucial step in consolidating the constitutional democracy. The question that will face any court in giving effect to socio-economic rights is: how are these rights to be judicially enforced in a given context? The crux of this thesis lies in the resolution of this question. Firstly this thesis traces the philosophical foundations to the legal recognition of socio-economic rights. It is stated that the recognition of these rights in a justiciable bill of rights requires a conceptually sound understanding of the nature of obligations that these rights place on the state. It is emphasised that it is imperative that access to justice be facilitated to poor and vulnerable members of society for the realisation of the constitutional goal of addressing inequality. Particular concern and priority should in this context be given to women, children and the disabled. The study explores various judicial remedies and makes suggestions on new and innovative constitutional mechanisms for judicial enforcement of these rights. It is concluded that there is an important role to be played by civil society in giving meaningful effect to socio-economic rights.
- Full Text:
- Date Issued: 2003
- Authors: Ngcukaitobi, T
- Date: 2003
- Subjects: South Africa. Constitution , South Africa. Bill of Rights , Civil rights -- South Africa , Human rights -- South Africa , South Africa -- Politics and government -- 1994- , South Africa -- Economic conditions -- 1991- , South Africa -- Social conditions -- 1994-
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:3689 , http://hdl.handle.net/10962/d1003204 , South Africa. Constitution , South Africa. Bill of Rights , Civil rights -- South Africa , Human rights -- South Africa , South Africa -- Politics and government -- 1994- , South Africa -- Economic conditions -- 1991- , South Africa -- Social conditions -- 1994-
- Description: Few legal developments in South Africa and elsewhere in the world in recent times have excited such controversy as the legal recognition of social and economic rights. South Africa has created a special place for itself in world affairs for being one of the countries that recognise socio-economic rights in a justiciable Bill of Rights. Partly this is in response to the appalling levels of poverty prevalent in the country which could potentially destabilise the new democracy. Improvement of the quality of life of every citizen is a crucial step in consolidating the constitutional democracy. The question that will face any court in giving effect to socio-economic rights is: how are these rights to be judicially enforced in a given context? The crux of this thesis lies in the resolution of this question. Firstly this thesis traces the philosophical foundations to the legal recognition of socio-economic rights. It is stated that the recognition of these rights in a justiciable bill of rights requires a conceptually sound understanding of the nature of obligations that these rights place on the state. It is emphasised that it is imperative that access to justice be facilitated to poor and vulnerable members of society for the realisation of the constitutional goal of addressing inequality. Particular concern and priority should in this context be given to women, children and the disabled. The study explores various judicial remedies and makes suggestions on new and innovative constitutional mechanisms for judicial enforcement of these rights. It is concluded that there is an important role to be played by civil society in giving meaningful effect to socio-economic rights.
- Full Text:
- Date Issued: 2003
King Henry VI 3, John D. Cox and Eric Rasmussen eds.: book review
- Authors: Birkinshaw, Catherine
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457698 , vital:75671 , https://hdl.handle.net/10520/EJC48011
- Description: This edition of 3 Henry VI includes a newly edited modernised version of the 1623 Folio text and a reduced photographic facsimile of the Octavo version of the play, called The true Tragedie of Richard Duke of Yorke, and the death of good King Henrie the Sixt, and published in 1595.
- Full Text:
- Date Issued: 2003
- Authors: Birkinshaw, Catherine
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457698 , vital:75671 , https://hdl.handle.net/10520/EJC48011
- Description: This edition of 3 Henry VI includes a newly edited modernised version of the 1623 Folio text and a reduced photographic facsimile of the Octavo version of the play, called The true Tragedie of Richard Duke of Yorke, and the death of good King Henrie the Sixt, and published in 1595.
- Full Text:
- Date Issued: 2003
Labour law implications of organisational restructuring
- Authors: Grootboom, Linda Henry
- Date: 2003
- Subjects: Labor laws and legislation -- South Africa , Organizational change -- South Africa
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:11041 , http://hdl.handle.net/10948/303 , Labor laws and legislation -- South Africa , Organizational change -- South Africa
- Description: It is beyond debate that each job lost due to restructuring means a lost taxpayer, and hence lost tax revenue, more poverty and increased crime. South Africa and the world at the large have to deal with this problem head – on in view of the acute need to better the lives of people and encourage investment. Technological advancement should be embraced and used to benefit people and stimulate economies, and that is further challenge in its own right. In Chapter 8 of the White Paper on Transformation of the Public Service dated 15 November 1995 (hereinafter, the White Paper), it is said that: “The Government of National Unity has embarked upon a concerted and comprehensive programme of administrative restructuring and rationalisation (my emphasis) with the object of: (a) Creating a unified and integrated service. (b) Creating a leaner and more cost-effective service.” Various strategies are listed in the White Paper, and the fundamental approach advocated is to right size, adjust remuneration structures, retrench and contract – out services.
- Full Text:
- Date Issued: 2003
- Authors: Grootboom, Linda Henry
- Date: 2003
- Subjects: Labor laws and legislation -- South Africa , Organizational change -- South Africa
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:11041 , http://hdl.handle.net/10948/303 , Labor laws and legislation -- South Africa , Organizational change -- South Africa
- Description: It is beyond debate that each job lost due to restructuring means a lost taxpayer, and hence lost tax revenue, more poverty and increased crime. South Africa and the world at the large have to deal with this problem head – on in view of the acute need to better the lives of people and encourage investment. Technological advancement should be embraced and used to benefit people and stimulate economies, and that is further challenge in its own right. In Chapter 8 of the White Paper on Transformation of the Public Service dated 15 November 1995 (hereinafter, the White Paper), it is said that: “The Government of National Unity has embarked upon a concerted and comprehensive programme of administrative restructuring and rationalisation (my emphasis) with the object of: (a) Creating a unified and integrated service. (b) Creating a leaner and more cost-effective service.” Various strategies are listed in the White Paper, and the fundamental approach advocated is to right size, adjust remuneration structures, retrench and contract – out services.
- Full Text:
- Date Issued: 2003
Language and value : the place of evaluation in linguistic theory
- Authors: Kilpert, Diana Mary
- Date: 2003
- Subjects: Linguistics -- Philosophy Systemic grammar Discourse analysis English language -- Standardization Linguistic analysis (Linguistics) Functionalism (Linguistics) Halliday, M. A. K. (Michael Alexander Kirkwood), 1925- Chomsky, Noam Labov, William Pinker, Steven, 1954- Harris, Roy, 1931-
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2353 , http://hdl.handle.net/10962/d1002635
- Description: It is a central claim of modern linguistic theory that linguists do not prescribe, but describe language as it is, without pronouncing on correctness or judging one variety better than another. This attempt to exclude evaluation is motivated by a desire to be ' politically correct', which hinders objective analysis of language, and by an ill-advised imitation of the natural sciences, which obstructs the discipline's progress towards becoming a science in its own right. It involves linguists, as users of a valued variety, in self-deception and disingenuousness, distances them from the concerns of the ordinary language user, and betrays a failure to understand the involvement of social values in language, the nature of language itself, and the limits of linguistic science. On a wider scale, linguistics reflects society's devaluing and mechanisation of language. Despite growing concern expressed in the literature, and the incoherence that becomes apparent when linguists attempt to address social problems using a theory that regards language as an autonomous object, newcomers to the discipline continue to be taught that anti-prescriptivism is the natural corollary of a scientific approach to language. This thesis suggests that the way out of these difficulties is to rethink the meaning of ' theory' in linguistics. If we take the reflexivity of language seriously, building on M.A.K. Halliday's notion of 'linguistics as metaphor', we are reminded that a linguistic theory is made of language. Metalanguage must use the experiential and interpersonal meaning-making resources of everyday language. It follows that a linguistic theory cannot escape being evaluative, because evaluation is an inherent part of interpersonal meaning. If we fail to notice our own metalinguistic evaluation, this is because language disguises its evaluative meanings, or perhaps we are just not used to thinking of them as part of the grammar. To achieve clarity about the involvement of value in language, we need to turn our metalanguage back on itself - 'using the grammar to think with about the grammar' . Some ways of doing this are demonstrated here, turning the resources of systemic functional linguistics on linguists' own language. The circularity of this process should be seen not as a drawback but as a salutary reminder that linguistics is an interpretive rather than a discovery process. This knowledge should help us revalue language and make a place for evaluation in linguistic theory, paving the way for a socially responsible and productive linguistics.
- Full Text:
- Date Issued: 2003
- Authors: Kilpert, Diana Mary
- Date: 2003
- Subjects: Linguistics -- Philosophy Systemic grammar Discourse analysis English language -- Standardization Linguistic analysis (Linguistics) Functionalism (Linguistics) Halliday, M. A. K. (Michael Alexander Kirkwood), 1925- Chomsky, Noam Labov, William Pinker, Steven, 1954- Harris, Roy, 1931-
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2353 , http://hdl.handle.net/10962/d1002635
- Description: It is a central claim of modern linguistic theory that linguists do not prescribe, but describe language as it is, without pronouncing on correctness or judging one variety better than another. This attempt to exclude evaluation is motivated by a desire to be ' politically correct', which hinders objective analysis of language, and by an ill-advised imitation of the natural sciences, which obstructs the discipline's progress towards becoming a science in its own right. It involves linguists, as users of a valued variety, in self-deception and disingenuousness, distances them from the concerns of the ordinary language user, and betrays a failure to understand the involvement of social values in language, the nature of language itself, and the limits of linguistic science. On a wider scale, linguistics reflects society's devaluing and mechanisation of language. Despite growing concern expressed in the literature, and the incoherence that becomes apparent when linguists attempt to address social problems using a theory that regards language as an autonomous object, newcomers to the discipline continue to be taught that anti-prescriptivism is the natural corollary of a scientific approach to language. This thesis suggests that the way out of these difficulties is to rethink the meaning of ' theory' in linguistics. If we take the reflexivity of language seriously, building on M.A.K. Halliday's notion of 'linguistics as metaphor', we are reminded that a linguistic theory is made of language. Metalanguage must use the experiential and interpersonal meaning-making resources of everyday language. It follows that a linguistic theory cannot escape being evaluative, because evaluation is an inherent part of interpersonal meaning. If we fail to notice our own metalinguistic evaluation, this is because language disguises its evaluative meanings, or perhaps we are just not used to thinking of them as part of the grammar. To achieve clarity about the involvement of value in language, we need to turn our metalanguage back on itself - 'using the grammar to think with about the grammar' . Some ways of doing this are demonstrated here, turning the resources of systemic functional linguistics on linguists' own language. The circularity of this process should be seen not as a drawback but as a salutary reminder that linguistics is an interpretive rather than a discovery process. This knowledge should help us revalue language and make a place for evaluation in linguistic theory, paving the way for a socially responsible and productive linguistics.
- Full Text:
- Date Issued: 2003
Life history traits of Bathyclarias nyasensis (Siluroidei) in Lake Malawi
- Authors: Kaunda, E , Hecht, Thomas
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/446918 , vital:74570 , https://doi.org/10.1080/15627020.2003.11657193
- Description: Life history traits, including age, growth, reproduction and diet of Bathyclarias nyasensis from Lake Malawi were studied between December 1996 and November 1998. Owing to reabsorption of pectoral spines with increasing fish size, and the relatively low number of spines that could be aged reliably, only otoliths were used to age fish. The maximum age for B. nyasensis was estimated at 14 years. There was no difference in growth rate between males and females.
- Full Text:
- Date Issued: 2003
- Authors: Kaunda, E , Hecht, Thomas
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/446918 , vital:74570 , https://doi.org/10.1080/15627020.2003.11657193
- Description: Life history traits, including age, growth, reproduction and diet of Bathyclarias nyasensis from Lake Malawi were studied between December 1996 and November 1998. Owing to reabsorption of pectoral spines with increasing fish size, and the relatively low number of spines that could be aged reliably, only otoliths were used to age fish. The maximum age for B. nyasensis was estimated at 14 years. There was no difference in growth rate between males and females.
- Full Text:
- Date Issued: 2003
Locating the institution of traditional leadership within the institutional framework of South Africa's new democracy
- Authors: Mashele, Hlukanisa Prince
- Date: 2003
- Subjects: Tribal government -- South Africa , Political leadership -- South Africa , South Africa -- Politics and government -- 1994-
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2858 , http://hdl.handle.net/10962/d1007512 , Tribal government -- South Africa , Political leadership -- South Africa , South Africa -- Politics and government -- 1994-
- Description: This study looks into the role of the institution of traditional leadership in post-apartheid South Africa. It seeks to critically engage the debate on how to locate the institution within the new politico-constitutional framework. This is done with the main objective of proposing an altemative to the current state of affairs vis-à-vis traditional leadership and governance in South Africa. In order to clear the ground, the study first deals with the important question of democracy in relation to the institution of traditional leadership. In this regard, the study unearthed that the institution of traditional leadership is fundamentally undemocratic in character, as it is largely based on heredity and devoid of principles of democracy such as equality, accountability, etc. In order to put matters into perspective the study also delves into the history of the institution of traditional leadership with the aim of getting to the role that traditional leaders played in various epochs of South Africa's political development. This investigation reveals that the denting of the integrity of the institution of traditional leadership began with the advent of colonialism and worsened by successive apartheid regimes. It is at these stages of development that the institution was subordinated to a higher authority that sought to use the institution as an instrument of domination and oppression of the black majority. Considering this role, it would seem that the place that the space that the institution occupies in the post-apartheid South African governance framework is a compromise. The institution plays an advisory role at all levels of government - with their houses in both national and provincial legislatures, whilst traditional leaders sit as ex-officio members on local councils. However, traditional leaders fiercely contest this position as, in their view, this limits their powers. The main argument of this study is that for traditional leaders to be given an advisory role in the current and future governance framework of the country is a step in the right direction, as that serves to insulate the institution from active politics. For that reason, the study recommends that the institution of traditional leadership should occupy a cultural space in society - meaning that it should be responsible for the preservation of African customs and culture. This, therefore, means that the institution is better-placed to advise government on cultural and customary aspects of development. Whilst playing this role, the institution of traditional leadership should also -be brought into line with democratic ways of governance.
- Full Text:
- Date Issued: 2003
- Authors: Mashele, Hlukanisa Prince
- Date: 2003
- Subjects: Tribal government -- South Africa , Political leadership -- South Africa , South Africa -- Politics and government -- 1994-
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2858 , http://hdl.handle.net/10962/d1007512 , Tribal government -- South Africa , Political leadership -- South Africa , South Africa -- Politics and government -- 1994-
- Description: This study looks into the role of the institution of traditional leadership in post-apartheid South Africa. It seeks to critically engage the debate on how to locate the institution within the new politico-constitutional framework. This is done with the main objective of proposing an altemative to the current state of affairs vis-à-vis traditional leadership and governance in South Africa. In order to clear the ground, the study first deals with the important question of democracy in relation to the institution of traditional leadership. In this regard, the study unearthed that the institution of traditional leadership is fundamentally undemocratic in character, as it is largely based on heredity and devoid of principles of democracy such as equality, accountability, etc. In order to put matters into perspective the study also delves into the history of the institution of traditional leadership with the aim of getting to the role that traditional leaders played in various epochs of South Africa's political development. This investigation reveals that the denting of the integrity of the institution of traditional leadership began with the advent of colonialism and worsened by successive apartheid regimes. It is at these stages of development that the institution was subordinated to a higher authority that sought to use the institution as an instrument of domination and oppression of the black majority. Considering this role, it would seem that the place that the space that the institution occupies in the post-apartheid South African governance framework is a compromise. The institution plays an advisory role at all levels of government - with their houses in both national and provincial legislatures, whilst traditional leaders sit as ex-officio members on local councils. However, traditional leaders fiercely contest this position as, in their view, this limits their powers. The main argument of this study is that for traditional leaders to be given an advisory role in the current and future governance framework of the country is a step in the right direction, as that serves to insulate the institution from active politics. For that reason, the study recommends that the institution of traditional leadership should occupy a cultural space in society - meaning that it should be responsible for the preservation of African customs and culture. This, therefore, means that the institution is better-placed to advise government on cultural and customary aspects of development. Whilst playing this role, the institution of traditional leadership should also -be brought into line with democratic ways of governance.
- Full Text:
- Date Issued: 2003
Lorine Niedecker Collected Works. Ed. Jenny Penberthy. University of California Press, 2002
- Authors: Wessels, Paul
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , poem
- Identifier: http://hdl.handle.net/10962/464663 , vital:76534 , ISBN 0028-4459 , https://journals.co.za/doi/epdf/10.10520/AJA00284459_604
- Description: New Coin is one of South Africa's most established and influential poetry journals. It publishes poetry, and poetry-related reviews, commentary and interviews. New Coin places a particular emphasis on evolving forms and experimental use of the English language in poetry in the South African context. In this sense it has traced the most exciting trends and currents in contemporary poetry in South Africa for a decade of more. The journal is published twice a year in June and December by the Institute for the Study of English in Africa (ISEA), Rhodes University.
- Full Text:
- Date Issued: 2003
- Authors: Wessels, Paul
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , poem
- Identifier: http://hdl.handle.net/10962/464663 , vital:76534 , ISBN 0028-4459 , https://journals.co.za/doi/epdf/10.10520/AJA00284459_604
- Description: New Coin is one of South Africa's most established and influential poetry journals. It publishes poetry, and poetry-related reviews, commentary and interviews. New Coin places a particular emphasis on evolving forms and experimental use of the English language in poetry in the South African context. In this sense it has traced the most exciting trends and currents in contemporary poetry in South Africa for a decade of more. The journal is published twice a year in June and December by the Institute for the Study of English in Africa (ISEA), Rhodes University.
- Full Text:
- Date Issued: 2003
Marketing fresh venison in the Eastern Cape Province using a niche marketing strategy
- Authors: Bull, Gregory Simon
- Date: 2003
- Subjects: Market segmentation , Venison -- Marketing , Meat industry and trade -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MTech (Marketing)
- Identifier: vital:10765 , http://hdl.handle.net/10948/136 , Market segmentation , Venison -- Marketing , Meat industry and trade -- South Africa -- Eastern Cape
- Description: There is a need in the Eastern Cape Province to expand the market for fresh venison. This need is due in part to fluctuations in the export market and fragmentation of consumption in the food industry, which has led to an increased demand for specialised and customised products. A suitable method for addressing these issues and successfully marketing fresh venison in the Eastern Cape Province was required, and based on the findings of this study, niche marketing was found to be a possible marketing method to explore. This study evaluated how a strategy of niche marketing could be used to market fresh venison within the Eastern Cape Province. By analysing this main problem the research attempted to identify and understand the challenges of marketing fresh venison to the final consumer in the Eastern Cape Province and to determine whether niche marketing would be a viable option when taking into account venison’s unique characteristics. Niche marketing was characterised and discussed in the light of other marketing approaches and the most important elements of a successful niche marketing strategy were highlighted. The information resulting from scrutiny of all of these sub-problems was then used to address the challenge of marketing fresh venison to the final consumer. In-depth interviews were deemed most suitable for this study based on the nature of the topic and the depth of expertise of qualified personnel in the Eastern Cape Province fresh venison industry. Consequently, four interviews were conducted with experts in the field. Using the niche marketing concept and the strategy that drives it, namely differentiation, possible niche markets were identified. A strategy of multiple niching was adopted to address the differentiation opportunities available, based on the relevant specialist roles of fresh venison. These differentiation opportunities in turn lead to competitive advantage. Possible niche target markets identified and analysed included the tourist market, travellers (foreign and local) by air and sea, the organic aware market and the pet food market. Branding was found to be an integral element for the niche marketing of venison and is also discussed. The main problems hindering fresh venison marketing in the Eastern Cape Province were found to be consumers’ lack of knowledge of venison, cultural differences and consumer preferences, lack of a formal infrastructure and control, and a lack of accurate data. These challenges need to be addressed before fresh venison can be successfully marketed in the Eastern Cape Province. Research needs to be conducted on the venison industry and formal supply chains and control channels need to be implemented before a quality product in substantial and consistent quantities can be successfully marketed to the final consumer. Consumers and industry personnel must be educated about venison and its merits, and fresh venison must initially target white tablecloth restaurants and specialised delicatessens, where service is as important as the product itself.
- Full Text:
- Date Issued: 2003
- Authors: Bull, Gregory Simon
- Date: 2003
- Subjects: Market segmentation , Venison -- Marketing , Meat industry and trade -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MTech (Marketing)
- Identifier: vital:10765 , http://hdl.handle.net/10948/136 , Market segmentation , Venison -- Marketing , Meat industry and trade -- South Africa -- Eastern Cape
- Description: There is a need in the Eastern Cape Province to expand the market for fresh venison. This need is due in part to fluctuations in the export market and fragmentation of consumption in the food industry, which has led to an increased demand for specialised and customised products. A suitable method for addressing these issues and successfully marketing fresh venison in the Eastern Cape Province was required, and based on the findings of this study, niche marketing was found to be a possible marketing method to explore. This study evaluated how a strategy of niche marketing could be used to market fresh venison within the Eastern Cape Province. By analysing this main problem the research attempted to identify and understand the challenges of marketing fresh venison to the final consumer in the Eastern Cape Province and to determine whether niche marketing would be a viable option when taking into account venison’s unique characteristics. Niche marketing was characterised and discussed in the light of other marketing approaches and the most important elements of a successful niche marketing strategy were highlighted. The information resulting from scrutiny of all of these sub-problems was then used to address the challenge of marketing fresh venison to the final consumer. In-depth interviews were deemed most suitable for this study based on the nature of the topic and the depth of expertise of qualified personnel in the Eastern Cape Province fresh venison industry. Consequently, four interviews were conducted with experts in the field. Using the niche marketing concept and the strategy that drives it, namely differentiation, possible niche markets were identified. A strategy of multiple niching was adopted to address the differentiation opportunities available, based on the relevant specialist roles of fresh venison. These differentiation opportunities in turn lead to competitive advantage. Possible niche target markets identified and analysed included the tourist market, travellers (foreign and local) by air and sea, the organic aware market and the pet food market. Branding was found to be an integral element for the niche marketing of venison and is also discussed. The main problems hindering fresh venison marketing in the Eastern Cape Province were found to be consumers’ lack of knowledge of venison, cultural differences and consumer preferences, lack of a formal infrastructure and control, and a lack of accurate data. These challenges need to be addressed before fresh venison can be successfully marketed in the Eastern Cape Province. Research needs to be conducted on the venison industry and formal supply chains and control channels need to be implemented before a quality product in substantial and consistent quantities can be successfully marketed to the final consumer. Consumers and industry personnel must be educated about venison and its merits, and fresh venison must initially target white tablecloth restaurants and specialised delicatessens, where service is as important as the product itself.
- Full Text:
- Date Issued: 2003
Media and parliament in the Third Republic: a study of newspaper coverage of parliament by the Times of Zambia and the Post from January to November 2001
- Authors: Djokotoe-Gliguie, Edem K
- Date: 2003
- Subjects: Newspapers -- Zambia Mass media -- Political aspects -- Zambia Zambia -- Politics and government
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3515 , http://hdl.handle.net/10962/d1007796
- Description: The press is credited with playing a central role in the consolidation of democracy by informing citizens, engaging them in the process of public decision making and governance and stimulating wide and inclusive debate on public matters. In emergent democracies like Zambia, the extent of the media's role as a public sphere, not to mention its impact, is not known. The study set out to investigate the extent of the press' public sphere role, particularly how Zambian newspapers report Parliament and how such coverage informs public opinion. It found that though the press covers Parliament, the nature of coverage does not empower newspaper readers with the kind of context, background and interpretation they would otherwise need to engage in public discourses on matters that affect them from an informed perspective. In the main, the role of the press in informing citizens is not fully realised, not only because uninformative character of coverage, but partly because of low literacy levels and the limited reach of local newspapers. It was against this background that the study recommended ways in which the Zambian press could re-focus its approach to parliamentary news coverage to make it more informational and more inclined towards playing a public sphere role, at least to the newspaper-reading public. Making parliamentary coverage an integrated newsroom function was the main recommendation. It provided the basis for suggesting a practical editorial option for the coverage of the legislature that accommodates the integration of context, background and interpretation into parliamentary news.
- Full Text:
- Date Issued: 2003
- Authors: Djokotoe-Gliguie, Edem K
- Date: 2003
- Subjects: Newspapers -- Zambia Mass media -- Political aspects -- Zambia Zambia -- Politics and government
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3515 , http://hdl.handle.net/10962/d1007796
- Description: The press is credited with playing a central role in the consolidation of democracy by informing citizens, engaging them in the process of public decision making and governance and stimulating wide and inclusive debate on public matters. In emergent democracies like Zambia, the extent of the media's role as a public sphere, not to mention its impact, is not known. The study set out to investigate the extent of the press' public sphere role, particularly how Zambian newspapers report Parliament and how such coverage informs public opinion. It found that though the press covers Parliament, the nature of coverage does not empower newspaper readers with the kind of context, background and interpretation they would otherwise need to engage in public discourses on matters that affect them from an informed perspective. In the main, the role of the press in informing citizens is not fully realised, not only because uninformative character of coverage, but partly because of low literacy levels and the limited reach of local newspapers. It was against this background that the study recommended ways in which the Zambian press could re-focus its approach to parliamentary news coverage to make it more informational and more inclined towards playing a public sphere role, at least to the newspaper-reading public. Making parliamentary coverage an integrated newsroom function was the main recommendation. It provided the basis for suggesting a practical editorial option for the coverage of the legislature that accommodates the integration of context, background and interpretation into parliamentary news.
- Full Text:
- Date Issued: 2003
Mesozooplankton community structure and grazing impact in the polar frontal zone of the Southern Ocean
- Authors: Bernard, Kim Sarah
- Date: 2003
- Subjects: Zooplankton -- Antarctic Ocean , Copepoda -- Feeding and feeds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5731 , http://hdl.handle.net/10962/d1005417 , Zooplankton -- Antarctic Ocean , Copepoda -- Feeding and feeds
- Description: Mesozooplankton community structure and grazing impact in the Polar Frontal Zone (PFZ) of the Southern Ocean were investigated during two cruises of the South African National Antarctic Programme (SANAP), the Marion Offshore Ecosystem Variability Study I & II (MOEVS). During the first cruise (MOEVS I), a meso-scale oceanographic grid survey was conducted in the upstream region of the Prince Edward Islands (PEI) in austral autumn (April) 2001. Mesozooplankton samples, collected using a Bongo net (fitted with 200 and 300µm mesh nets) at depths between 200 and 300 m, were separated into three size fractions: 200-500 µm; 500-1000 µm; 1000-2000 µm by reverse filtration. Total surface (depth <5 m) chlorophyll-a (chl-a) concentration (measured fluorometrically) during the study ranged between 0.11 and 0.34 µg 1^(-1) and was always dominated by picophytoplankton (<2.0 µm). Total mesozooplankton abundance and biomass during the survey ranged between 49 and 1512 ind. m^(-3) and between 0.7 and 25 mg Dwt. m^(-3), respectively. Throughout the survey, the 200-500 µm class numerically dominated the mesozooplankton community, comprising an average of ~ 69% (SD = ± 12.3%). The dominant species in the 200-500 µm size fraction were the copepods Oithona similis, Calanus simillimus and Metridia lucens and the pteropod, Limacina retroversa. However, in terms of biomass, the 1000-2000 µm group was predominant, with dry weight values constituting an average of ~ 66% (SD = ± 10.2%). Biomass was dominated by carnivorous zooplankton, particularly the euphausiids, Euphausia vallentini and Thysanoessa vicina and the chaetognaths, Sagitta gazellae and Eukrohnia hamata. Three distinct groupings of stations were identified by multivariate analysis. The different station groupings identified reflect changes in the relative contributions of the rather than different species assemblages. During the second cruise (MOEVS II), conducted in April 2002 (austral autumn), mesozooplankton community structure and grazing impact were investigated at 13 stations in the west Indian sector of the PFZ. Total integrated chl-a biomass ranged between 11.17 and 28.34 mg chl-a m^(-2) and was always dominated by nano- and picophytoplankton (<20 µm). Throughout the study, small copepods, mainly Oithona similis and Ctenocalanus vanus, numerically dominated the mesozooplankton community comprising up to 85% (range 30 to 85%) of the total abundance. Grazing activity of the four most abundant copepods (O. similis, C. vanus, Calanus simillimus and Clausocalanus spp.), which comprised up to 93% of total mesozooplankton abundance, was investigated using the gut fluorescent technique. Results of gut fluorescence analyses indicated that C. simillimus, Clausocalanus spp. and Ctenocalanus vanus exhibited diel variability in gut pigments, with maximum values at various stages of the night. In contrast, O. similis did not demonstrate diel variation in gut pigment contents. Ingestion rates of the four copepods ranged from 23.23 to 1462.02 ng (pigm.) ind^(-1) day^(-1), depending on the species. The combined grazing impact of the four copepods, ranged between 1 and 36% of the phytoplankton standing stock per day, with the highest daily impact (~ 35.86%) occurring at stations in the vicinity of the Antarctic Polar Front. Among the copepods, O. similis and C. vanus were generally the most important consumers of phytoplankton biomass; together they were responsible for up to 89% (range 15 to 89%) of the total daily grazing impact. Carbon specific ingestion rates of the copepods varied between 42 and 320% body carbon per day, depending on the species. The study highlights the importance of small copepods in terms of both their significant contribution to total mesozooplankton numbers and their grazing impact on the phytoplankton standing stocks in the PFZ during austral autumn.
- Full Text:
- Date Issued: 2003
- Authors: Bernard, Kim Sarah
- Date: 2003
- Subjects: Zooplankton -- Antarctic Ocean , Copepoda -- Feeding and feeds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5731 , http://hdl.handle.net/10962/d1005417 , Zooplankton -- Antarctic Ocean , Copepoda -- Feeding and feeds
- Description: Mesozooplankton community structure and grazing impact in the Polar Frontal Zone (PFZ) of the Southern Ocean were investigated during two cruises of the South African National Antarctic Programme (SANAP), the Marion Offshore Ecosystem Variability Study I & II (MOEVS). During the first cruise (MOEVS I), a meso-scale oceanographic grid survey was conducted in the upstream region of the Prince Edward Islands (PEI) in austral autumn (April) 2001. Mesozooplankton samples, collected using a Bongo net (fitted with 200 and 300µm mesh nets) at depths between 200 and 300 m, were separated into three size fractions: 200-500 µm; 500-1000 µm; 1000-2000 µm by reverse filtration. Total surface (depth <5 m) chlorophyll-a (chl-a) concentration (measured fluorometrically) during the study ranged between 0.11 and 0.34 µg 1^(-1) and was always dominated by picophytoplankton (<2.0 µm). Total mesozooplankton abundance and biomass during the survey ranged between 49 and 1512 ind. m^(-3) and between 0.7 and 25 mg Dwt. m^(-3), respectively. Throughout the survey, the 200-500 µm class numerically dominated the mesozooplankton community, comprising an average of ~ 69% (SD = ± 12.3%). The dominant species in the 200-500 µm size fraction were the copepods Oithona similis, Calanus simillimus and Metridia lucens and the pteropod, Limacina retroversa. However, in terms of biomass, the 1000-2000 µm group was predominant, with dry weight values constituting an average of ~ 66% (SD = ± 10.2%). Biomass was dominated by carnivorous zooplankton, particularly the euphausiids, Euphausia vallentini and Thysanoessa vicina and the chaetognaths, Sagitta gazellae and Eukrohnia hamata. Three distinct groupings of stations were identified by multivariate analysis. The different station groupings identified reflect changes in the relative contributions of the rather than different species assemblages. During the second cruise (MOEVS II), conducted in April 2002 (austral autumn), mesozooplankton community structure and grazing impact were investigated at 13 stations in the west Indian sector of the PFZ. Total integrated chl-a biomass ranged between 11.17 and 28.34 mg chl-a m^(-2) and was always dominated by nano- and picophytoplankton (<20 µm). Throughout the study, small copepods, mainly Oithona similis and Ctenocalanus vanus, numerically dominated the mesozooplankton community comprising up to 85% (range 30 to 85%) of the total abundance. Grazing activity of the four most abundant copepods (O. similis, C. vanus, Calanus simillimus and Clausocalanus spp.), which comprised up to 93% of total mesozooplankton abundance, was investigated using the gut fluorescent technique. Results of gut fluorescence analyses indicated that C. simillimus, Clausocalanus spp. and Ctenocalanus vanus exhibited diel variability in gut pigments, with maximum values at various stages of the night. In contrast, O. similis did not demonstrate diel variation in gut pigment contents. Ingestion rates of the four copepods ranged from 23.23 to 1462.02 ng (pigm.) ind^(-1) day^(-1), depending on the species. The combined grazing impact of the four copepods, ranged between 1 and 36% of the phytoplankton standing stock per day, with the highest daily impact (~ 35.86%) occurring at stations in the vicinity of the Antarctic Polar Front. Among the copepods, O. similis and C. vanus were generally the most important consumers of phytoplankton biomass; together they were responsible for up to 89% (range 15 to 89%) of the total daily grazing impact. Carbon specific ingestion rates of the copepods varied between 42 and 320% body carbon per day, depending on the species. The study highlights the importance of small copepods in terms of both their significant contribution to total mesozooplankton numbers and their grazing impact on the phytoplankton standing stocks in the PFZ during austral autumn.
- Full Text:
- Date Issued: 2003
Metal interactions with neural substrates and their role in neurodegeneration
- Authors: Lack, Barbara Anne
- Date: 2003
- Subjects: Nervous system -- Degeneration Neurotoxicology Chemical reactions Metals -- Physiological effect Melatonin -- Physiological effect
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4391 , http://hdl.handle.net/10962/d1005709
- Description: "Life" may be characterized as a controlled stationary flow equilibrium, maintained by energy consuming chemical reactions. The physiological functioning of these life systems include at least 28 of the elements isolated on the periodic table thus far, most of which are metals. However, as with Paracelsus Principle: "The dose makes the poison", there exists a definite link between metal levels, essential and toxic, and the onset of neurodegenerative diseases. The economic costs of brain dysfunction are enormous, but this pales in comparison to the staggering emotional toll on the victims themselves and their families. In an attempt to improve the understanding of the causes of neurodegeneration, this study focuses on one potential aspect: the possible link between metals and neurotransmitter homeostasis utilising a variety of electronanalytical techniques. Adsorptive cathodic stripping voltammetry was employed to investigate the binding affinities and complex formation of melatonin and its precursor serotonin with calcium, potassium, sodium, lithium and aluminium. The results showed that all the metals studied formed complexes with both pineal indoleamines. However, the stability and affmity of the ligands toward the various metals varied greatly. The study suggests a further role for melatonin, that of metalloregulator and possible metal detoxifier in the brain, the in vivo studies which followed will further substantiate this notion. This research additionally focused on the cholinergic system, in particular acetylcholine complex formation studies with mercury, lead, cadmium, copper and zinc using the adsorptive cathodic stripping voltammetry method. The formation and characterisation of a solid mercury-acetylcholine complex lent further strength to the in situ electrochemical complex formation observed. The results showed the preference of acetylcholine for environmentally toxic heavy metals (such as Cd²⁺) over those divalent cations that occur naturally in the body. The possible metalloregulatory role melatonin played in the three brain regIOns: cerebellum, cortex and corpus striatum of male Wistar rats was studied as an in vivo extension of the earlier in vitro studies. Anodic stripping voltammetry was employed to detect metal levels present. The results showed that daily injections of melatonin was responsible for significantly decreasing copper(I), cadmium(II) and lead(II) levels in various regions of the rat brain of those animals that had undergone a pinealectomy in comparison to the saline injected group having undergone the same treatment. Histological and electrochemical stripping techniques were applied to investigate the implications of high A1³⁺ levels in the brain regions, particularly the hippocampus. Melatonin showed signs of promise in indirect symptom alleviation and by significantly decreasing A1³⁺ levels in rats that had been dosed with melatonin prior to A1³⁺ treatments in comparison with the control groups. Finally a preliminary study outlining a method for the production of a calcium selective microelectrode was undertaken. Further work is still needed to optimise the microelectrode production as well as its possible applications. However, whilst the overall conclusions of this entire multidisciplinary study may indeed only be in effect one piece of a very large puzzle on neurodegenerative diseases, this piece will no doubt serve as a building block for further ideas and work in this field.
- Full Text:
- Date Issued: 2003
- Authors: Lack, Barbara Anne
- Date: 2003
- Subjects: Nervous system -- Degeneration Neurotoxicology Chemical reactions Metals -- Physiological effect Melatonin -- Physiological effect
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4391 , http://hdl.handle.net/10962/d1005709
- Description: "Life" may be characterized as a controlled stationary flow equilibrium, maintained by energy consuming chemical reactions. The physiological functioning of these life systems include at least 28 of the elements isolated on the periodic table thus far, most of which are metals. However, as with Paracelsus Principle: "The dose makes the poison", there exists a definite link between metal levels, essential and toxic, and the onset of neurodegenerative diseases. The economic costs of brain dysfunction are enormous, but this pales in comparison to the staggering emotional toll on the victims themselves and their families. In an attempt to improve the understanding of the causes of neurodegeneration, this study focuses on one potential aspect: the possible link between metals and neurotransmitter homeostasis utilising a variety of electronanalytical techniques. Adsorptive cathodic stripping voltammetry was employed to investigate the binding affinities and complex formation of melatonin and its precursor serotonin with calcium, potassium, sodium, lithium and aluminium. The results showed that all the metals studied formed complexes with both pineal indoleamines. However, the stability and affmity of the ligands toward the various metals varied greatly. The study suggests a further role for melatonin, that of metalloregulator and possible metal detoxifier in the brain, the in vivo studies which followed will further substantiate this notion. This research additionally focused on the cholinergic system, in particular acetylcholine complex formation studies with mercury, lead, cadmium, copper and zinc using the adsorptive cathodic stripping voltammetry method. The formation and characterisation of a solid mercury-acetylcholine complex lent further strength to the in situ electrochemical complex formation observed. The results showed the preference of acetylcholine for environmentally toxic heavy metals (such as Cd²⁺) over those divalent cations that occur naturally in the body. The possible metalloregulatory role melatonin played in the three brain regIOns: cerebellum, cortex and corpus striatum of male Wistar rats was studied as an in vivo extension of the earlier in vitro studies. Anodic stripping voltammetry was employed to detect metal levels present. The results showed that daily injections of melatonin was responsible for significantly decreasing copper(I), cadmium(II) and lead(II) levels in various regions of the rat brain of those animals that had undergone a pinealectomy in comparison to the saline injected group having undergone the same treatment. Histological and electrochemical stripping techniques were applied to investigate the implications of high A1³⁺ levels in the brain regions, particularly the hippocampus. Melatonin showed signs of promise in indirect symptom alleviation and by significantly decreasing A1³⁺ levels in rats that had been dosed with melatonin prior to A1³⁺ treatments in comparison with the control groups. Finally a preliminary study outlining a method for the production of a calcium selective microelectrode was undertaken. Further work is still needed to optimise the microelectrode production as well as its possible applications. However, whilst the overall conclusions of this entire multidisciplinary study may indeed only be in effect one piece of a very large puzzle on neurodegenerative diseases, this piece will no doubt serve as a building block for further ideas and work in this field.
- Full Text:
- Date Issued: 2003
Metallophthalocyanine derivatives as catalysts for the detection of sulphur dioxide, cyanide, nitrite and amino acids
- Authors: Thamae, Mamothibe Amelia
- Date: 2003
- Subjects: Cyanides Nitric oxide Electrochemistry Nitrites Suplhur dioxide Amino acids
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4295 , http://hdl.handle.net/10962/d1004542
- Description: Electrocatalytic reduction and oxidation of nitrite using cobalt phthalocyanine derivatives was studied. The detection limit of 1 x 10⁻¹° mol dm⁻³ was achieved when these molecules were employed as catalysts for nitrite detection. The mechanisms for nitrite catalysis were proposed. The position of the peripheral substituents on cobalt porphyrazines (related to cobalt phthalocyanines) affected the catalytic activity of these complexes. The highest activity for nitrite reduction was observed on the cobalt(II) 2,3-tetramethyltetrapyridinoporphyrazine ([CoTm-2,3-tppa]⁴⁺), with cobalt phthalocyanine showing the lowest activity, and the cobalt(II) 3,4- tetramethyltetrapyridinoporphyrazine ([CoTm-3,4-tppa]⁴⁺), showing intermediate behaviour. A mixture of a negatively charged cobalt(II) tetrasulfophthalocyanine ([Co¹¹TSPc]⁴⁻) and a positively charged [CoTm-3,4-tppa]⁴⁺ showed better activity for nitrite reduction than did the individual components. Cobalt porphyrazines lowered the potentials for nitrite reduction in that peaking was observed, as opposed to cobalt phthalocyanine, where only the increase in currents was observed without peaking. Using the cobalt phthalocyanine derivatives, nitrite can be reduced to ammonia with high current efficiency. A glassy carbon electrode modified with [Co¹¹TSPc]⁴⁻ was employed for the determination of nitrite. Nitrate had an insignificant effect on nitrite oxidation on these modified electrodes. Electrocatalytic determination of S0₂ was studied as a function of pH at a glassy carbon electrode modified with iron(II) tetrasulfophthalocaynine. It was found that depending on pH, S0₂.xH₂0, HS0₃⁻ and/or SO₃²⁻ are the main compounds in solution and that these compounds behave differently at the electrode surface. Detection limits ranging from 4.0 ± 0.1 x 10⁻⁵ to 7.5 ± 0.1 x 10⁻⁵ mol dm⁻³ depending on pH were observed. Similar results were obtained when cobalt(II) tetrasulfophthalocaynine was employed for S0₂ catalysis under the same experimental conditions. Cysteine and histidine determination using oxidation currents was performed on glassy carbon electrodes modified with [CoTm-3,4-tppa]⁴⁺ (represented as [CoTm-3,4-tppa]⁴⁺-GCE) in pH 7 Tris buffer. The detection limit of 1.0 x 10⁻⁵ mol dm⁻³ for cysteine and 2.24 x 10⁻⁷ mol dm⁻³ for histidine were obtained. Cyanide can be detected down to 1 x 10⁻¹¹ mol dm⁻³ using [CoTm-3,4-tppa]⁴⁺-GCE in pH 10.8 buffer. Cyanide and S0₂ coordinate to the [CoTSPc]⁴⁻ species. The coordination is accompanied by oxidation of the central Co(II) metal, forming a [Co¹¹¹CoTSPc]³⁻ species. The rate constants for cyanide coordination to the [Co¹¹TSPc]⁴⁻ complex are larger than those reported for the coordination of cyanide to FePc and RuPc complexes in non-aqueous media. Autoreduction of [Co¹¹Tmtppa]⁴⁺ occurred in the presence of either histidine or cysteine, with the formation of metal reduced species, [Co¹Tmtppa(-2)]³⁺. Nitric oxide and nitrite coordinate to the [Co¹¹Tmtppa]⁴⁺ species, without auto-reduction of this species, which was observed for cysteine or histidine. The use of [Co¹¹TSPc]⁴ resulted in improved rate of interaction with nitrite when compared to the [Co¹¹Tmtppa]⁴⁺ species.
- Full Text:
- Date Issued: 2003
- Authors: Thamae, Mamothibe Amelia
- Date: 2003
- Subjects: Cyanides Nitric oxide Electrochemistry Nitrites Suplhur dioxide Amino acids
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4295 , http://hdl.handle.net/10962/d1004542
- Description: Electrocatalytic reduction and oxidation of nitrite using cobalt phthalocyanine derivatives was studied. The detection limit of 1 x 10⁻¹° mol dm⁻³ was achieved when these molecules were employed as catalysts for nitrite detection. The mechanisms for nitrite catalysis were proposed. The position of the peripheral substituents on cobalt porphyrazines (related to cobalt phthalocyanines) affected the catalytic activity of these complexes. The highest activity for nitrite reduction was observed on the cobalt(II) 2,3-tetramethyltetrapyridinoporphyrazine ([CoTm-2,3-tppa]⁴⁺), with cobalt phthalocyanine showing the lowest activity, and the cobalt(II) 3,4- tetramethyltetrapyridinoporphyrazine ([CoTm-3,4-tppa]⁴⁺), showing intermediate behaviour. A mixture of a negatively charged cobalt(II) tetrasulfophthalocyanine ([Co¹¹TSPc]⁴⁻) and a positively charged [CoTm-3,4-tppa]⁴⁺ showed better activity for nitrite reduction than did the individual components. Cobalt porphyrazines lowered the potentials for nitrite reduction in that peaking was observed, as opposed to cobalt phthalocyanine, where only the increase in currents was observed without peaking. Using the cobalt phthalocyanine derivatives, nitrite can be reduced to ammonia with high current efficiency. A glassy carbon electrode modified with [Co¹¹TSPc]⁴⁻ was employed for the determination of nitrite. Nitrate had an insignificant effect on nitrite oxidation on these modified electrodes. Electrocatalytic determination of S0₂ was studied as a function of pH at a glassy carbon electrode modified with iron(II) tetrasulfophthalocaynine. It was found that depending on pH, S0₂.xH₂0, HS0₃⁻ and/or SO₃²⁻ are the main compounds in solution and that these compounds behave differently at the electrode surface. Detection limits ranging from 4.0 ± 0.1 x 10⁻⁵ to 7.5 ± 0.1 x 10⁻⁵ mol dm⁻³ depending on pH were observed. Similar results were obtained when cobalt(II) tetrasulfophthalocaynine was employed for S0₂ catalysis under the same experimental conditions. Cysteine and histidine determination using oxidation currents was performed on glassy carbon electrodes modified with [CoTm-3,4-tppa]⁴⁺ (represented as [CoTm-3,4-tppa]⁴⁺-GCE) in pH 7 Tris buffer. The detection limit of 1.0 x 10⁻⁵ mol dm⁻³ for cysteine and 2.24 x 10⁻⁷ mol dm⁻³ for histidine were obtained. Cyanide can be detected down to 1 x 10⁻¹¹ mol dm⁻³ using [CoTm-3,4-tppa]⁴⁺-GCE in pH 10.8 buffer. Cyanide and S0₂ coordinate to the [CoTSPc]⁴⁻ species. The coordination is accompanied by oxidation of the central Co(II) metal, forming a [Co¹¹¹CoTSPc]³⁻ species. The rate constants for cyanide coordination to the [Co¹¹TSPc]⁴⁻ complex are larger than those reported for the coordination of cyanide to FePc and RuPc complexes in non-aqueous media. Autoreduction of [Co¹¹Tmtppa]⁴⁺ occurred in the presence of either histidine or cysteine, with the formation of metal reduced species, [Co¹Tmtppa(-2)]³⁺. Nitric oxide and nitrite coordinate to the [Co¹¹Tmtppa]⁴⁺ species, without auto-reduction of this species, which was observed for cysteine or histidine. The use of [Co¹¹TSPc]⁴ resulted in improved rate of interaction with nitrite when compared to the [Co¹¹Tmtppa]⁴⁺ species.
- Full Text:
- Date Issued: 2003
Metallophthalocyanines as photocatalysts for transformation of chlorophenols and self-assembled monolayers for electrochemical detection of thiols and cyanides
- Authors: Ozoemena, Kenneth Ikechukwu
- Date: 2003
- Subjects: Electrochemistry Cyanides Thiols Chlorophenols Photocatalysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4089 , http://hdl.handle.net/10962/d1007709
- Description: Photochemical properties of sulphonated phthalocyanine complexes of aluminium, zinc, tin and silicon, and octa-carboxyphthalocyanine complexes of aluminium and zinc have been investigated. These water-soluble metallophthalocyanine (MPc) complexes, especially the sulphonated aluminium and zinc phthalocyanines, were found to be good photosensitisers for the transformation of the toxic mono-, tri- and penta-chlorophenols in aqueous solutions. The efficiency of MPc sensitiser towards photo-transformation of chlorophenols depends on its effectiveness to generate singlet oxygen as well as its photostability. Octa-substituted thiol-derivatised phthalocyanine complexes of cobalt, iron and zinc were synthesized and their spectral and electrochemical properties investigated. The photochemical properties ofthe zinc phthalocyanine complexes in non-aqueous solutions were comparable to those in literature. Ultrathin films of the octasubstituted thiol-derivatised phthalocyanine complexes of cobalt, iron and zinc were, for the first time, immobilized onto gold electrodes using the self-assembling technique. Surface electrochemistry indicates that the ultrathin films are surface-confined self-assembled monolayer (SAM) species. Gold electrodes modified with the redox-active SAMs of cobalt and iron phthalocyanine complexes proved to be potential electrochemical sensors for the detection of thiols (L-cysteine, homocysteine and penicillamine) and thiocyanate in aqueous solutions (pH 4). The limits of detection for the thiols and thiocyanate were in the range of ∼ 10⁻⁷ and 10⁻⁶ mol dm⁻³, respectively. The modification process was reproducible and the modified electrodes showed good stability and, if stored in pH 4 buffer solutions, could be used for the analysis of thiols and thiocyanate for about a month without the need for recalibration. Etching of gold marred electrochemical detection of cyanide with the MPc-SAM-modified gold electrodes. Interestingly, however, kinetic and equilibria studies revealed strong interaction of octabutylthiophthalocyaninatoiron (II), FeOBTPc, with cyanide in both DMF and DMSO solutions.
- Full Text:
- Date Issued: 2003
- Authors: Ozoemena, Kenneth Ikechukwu
- Date: 2003
- Subjects: Electrochemistry Cyanides Thiols Chlorophenols Photocatalysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4089 , http://hdl.handle.net/10962/d1007709
- Description: Photochemical properties of sulphonated phthalocyanine complexes of aluminium, zinc, tin and silicon, and octa-carboxyphthalocyanine complexes of aluminium and zinc have been investigated. These water-soluble metallophthalocyanine (MPc) complexes, especially the sulphonated aluminium and zinc phthalocyanines, were found to be good photosensitisers for the transformation of the toxic mono-, tri- and penta-chlorophenols in aqueous solutions. The efficiency of MPc sensitiser towards photo-transformation of chlorophenols depends on its effectiveness to generate singlet oxygen as well as its photostability. Octa-substituted thiol-derivatised phthalocyanine complexes of cobalt, iron and zinc were synthesized and their spectral and electrochemical properties investigated. The photochemical properties ofthe zinc phthalocyanine complexes in non-aqueous solutions were comparable to those in literature. Ultrathin films of the octasubstituted thiol-derivatised phthalocyanine complexes of cobalt, iron and zinc were, for the first time, immobilized onto gold electrodes using the self-assembling technique. Surface electrochemistry indicates that the ultrathin films are surface-confined self-assembled monolayer (SAM) species. Gold electrodes modified with the redox-active SAMs of cobalt and iron phthalocyanine complexes proved to be potential electrochemical sensors for the detection of thiols (L-cysteine, homocysteine and penicillamine) and thiocyanate in aqueous solutions (pH 4). The limits of detection for the thiols and thiocyanate were in the range of ∼ 10⁻⁷ and 10⁻⁶ mol dm⁻³, respectively. The modification process was reproducible and the modified electrodes showed good stability and, if stored in pH 4 buffer solutions, could be used for the analysis of thiols and thiocyanate for about a month without the need for recalibration. Etching of gold marred electrochemical detection of cyanide with the MPc-SAM-modified gold electrodes. Interestingly, however, kinetic and equilibria studies revealed strong interaction of octabutylthiophthalocyaninatoiron (II), FeOBTPc, with cyanide in both DMF and DMSO solutions.
- Full Text:
- Date Issued: 2003
Molecular characterization of the tetratricopeptide repeat-mediated interactions of murine stress-inducible protein 1 with major heat shock proteins
- Authors: Odunuga, Odutayo Odutola
- Date: 2003
- Subjects: Plants -- Effect of stress on Proteins -- Purification Electrophoresis Heat shock proteins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4091 , http://hdl.handle.net/10962/d1007724
- Description: Murine stress-inducible protein 1 (mSTI1) is a co-chaperone that is homologous with the human heat shock protein 70 (Hsp70)/heat shock protein 90 (Hsp90)-organizing protein (Hop). The two proteins are homologues of the highly conserved stress-inducible protein 1 (STI1) family of co-chaperones. The STI1 proteins interact directly and simultaneously at some stage, with Hsp70 and Hsp90 in the formation of the hetero-multi-chaperone complexes that facilitate the folding of signal transducing kinases and functional maturation of steroid hormone receptors. The interactions of mSTI1 with both Hsp70 and Hsp90 is mediated by a versatile structural protein-protein interaction motif, the tetratricopeptide repeat (TPR). The TPR motif is a degenerate 34-amino acid sequence a-helical structural motif found in a significant number of functionally unrelated proteins. This study was aimed at characterizing the structural and functional determinants in the TPR domains of mSTI1 responsible for binding to and discriminating between Hsp70 and Hsp90. Guided by data from Hop's crystal structures and amino acid sequence alignment analyses, various biochemical techniques were used to both qualitatively and quantitatively characterize the contacts necessary for the N-terminal TPR domain (TPR1) of mSTI1 to bind to the C-terminal EEVD motif of heat shock cognate protein 70 (Hsc70) and to discriminate between Hsc70 and Hsp90. Substitutions in the first TPR motif of Lys⁸ or Asn¹² did not affect binding of mSTI1 to Hsc70, while double substitution of these residues abrogated binding. A substitution in the second TPR motif of Asn⁴³ lowered but did not abrogate binding. Similarly, a deletion in the second TPR motif coupled with a substitution of Lys⁸ or Asn¹² reduced but did not abrogate binding. Steady state fluorescence and circular dichroism spectroscopies revealed that the double substitution of Lys⁸ and Asn¹² resulted in perturbations of inter-domain interactions in mSTl1. Together these results suggest that mSTI1-Hsc70 interaction requires a network of electrostatic interactions not only between charged residues in the TPR1 domain of mSTI1 and the EEVD motif of Hsc70, but also outside the TPR1 domain. It is proposed that the electrostatic interactions in the first TPR motif collectively made by Lys⁸ and Asn¹² define part of the minimum interactions required for successful mSTI1-Hsc70 interaction. In the first central TPR domain (TPR1A), single substitution of Lys³°¹ was sufficient to abrogate the mSTI1-Hsp90 interaction. Using a truncated derivative of mSTI1 incapable of binding to Hsp90, residues predicted by crystallographic data to determine Hsp70 binding specificity were substituted in the TPR1 domain. The modified protein had reduced binding to Hsc70, but showed significant binding capacity for Hsp90. In contrast, topologically equivalent substitutions on a truncated derivative of mSTI1 incapable of binding to Hsc70 did not confer Hsc70 specificity on the TPR2A domain. These data suggest that binding of Hsc70 to the TPR1 domain is more specific than binding of Hsp90 to the TPR2A domain. In addition, residues C-terminal of helix A in the second TPR motif of mSTI1 were shown to be important in determining specific binding to Hsc70. Binding assays using surface plasmon resonance spectroscopy showed that the affinities of binding of mSTI1 to Hsc70 and Hsp90 were 2 μM and 1.5 μM respectively. Preliminary in vivo studies revealed differences in the dynamics of binding of endogenous and exogenous recombinant mSTI1 with Hsc70 and Hsp90. The outcome of this study poses serious implications for the mechanisms of mSTI1 interactions with Hsc70 and Hsp90 in the cell.
- Full Text:
- Date Issued: 2003
- Authors: Odunuga, Odutayo Odutola
- Date: 2003
- Subjects: Plants -- Effect of stress on Proteins -- Purification Electrophoresis Heat shock proteins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4091 , http://hdl.handle.net/10962/d1007724
- Description: Murine stress-inducible protein 1 (mSTI1) is a co-chaperone that is homologous with the human heat shock protein 70 (Hsp70)/heat shock protein 90 (Hsp90)-organizing protein (Hop). The two proteins are homologues of the highly conserved stress-inducible protein 1 (STI1) family of co-chaperones. The STI1 proteins interact directly and simultaneously at some stage, with Hsp70 and Hsp90 in the formation of the hetero-multi-chaperone complexes that facilitate the folding of signal transducing kinases and functional maturation of steroid hormone receptors. The interactions of mSTI1 with both Hsp70 and Hsp90 is mediated by a versatile structural protein-protein interaction motif, the tetratricopeptide repeat (TPR). The TPR motif is a degenerate 34-amino acid sequence a-helical structural motif found in a significant number of functionally unrelated proteins. This study was aimed at characterizing the structural and functional determinants in the TPR domains of mSTI1 responsible for binding to and discriminating between Hsp70 and Hsp90. Guided by data from Hop's crystal structures and amino acid sequence alignment analyses, various biochemical techniques were used to both qualitatively and quantitatively characterize the contacts necessary for the N-terminal TPR domain (TPR1) of mSTI1 to bind to the C-terminal EEVD motif of heat shock cognate protein 70 (Hsc70) and to discriminate between Hsc70 and Hsp90. Substitutions in the first TPR motif of Lys⁸ or Asn¹² did not affect binding of mSTI1 to Hsc70, while double substitution of these residues abrogated binding. A substitution in the second TPR motif of Asn⁴³ lowered but did not abrogate binding. Similarly, a deletion in the second TPR motif coupled with a substitution of Lys⁸ or Asn¹² reduced but did not abrogate binding. Steady state fluorescence and circular dichroism spectroscopies revealed that the double substitution of Lys⁸ and Asn¹² resulted in perturbations of inter-domain interactions in mSTl1. Together these results suggest that mSTI1-Hsc70 interaction requires a network of electrostatic interactions not only between charged residues in the TPR1 domain of mSTI1 and the EEVD motif of Hsc70, but also outside the TPR1 domain. It is proposed that the electrostatic interactions in the first TPR motif collectively made by Lys⁸ and Asn¹² define part of the minimum interactions required for successful mSTI1-Hsc70 interaction. In the first central TPR domain (TPR1A), single substitution of Lys³°¹ was sufficient to abrogate the mSTI1-Hsp90 interaction. Using a truncated derivative of mSTI1 incapable of binding to Hsp90, residues predicted by crystallographic data to determine Hsp70 binding specificity were substituted in the TPR1 domain. The modified protein had reduced binding to Hsc70, but showed significant binding capacity for Hsp90. In contrast, topologically equivalent substitutions on a truncated derivative of mSTI1 incapable of binding to Hsc70 did not confer Hsc70 specificity on the TPR2A domain. These data suggest that binding of Hsc70 to the TPR1 domain is more specific than binding of Hsp90 to the TPR2A domain. In addition, residues C-terminal of helix A in the second TPR motif of mSTI1 were shown to be important in determining specific binding to Hsc70. Binding assays using surface plasmon resonance spectroscopy showed that the affinities of binding of mSTI1 to Hsc70 and Hsp90 were 2 μM and 1.5 μM respectively. Preliminary in vivo studies revealed differences in the dynamics of binding of endogenous and exogenous recombinant mSTI1 with Hsc70 and Hsp90. The outcome of this study poses serious implications for the mechanisms of mSTI1 interactions with Hsc70 and Hsp90 in the cell.
- Full Text:
- Date Issued: 2003
Molecular identification of some forensically important blowflies of southern Africa and Australia
- Harvey, M L, Mansell, M W, Villet, Martin H, Dadour, I R
- Authors: Harvey, M L , Mansell, M W , Villet, Martin H , Dadour, I R
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6953 , http://hdl.handle.net/10962/d1011986
- Description: One major aspect of research in forensic entomology is the investigation of molecular techniques for the accurate identification of insects. Studies to date have addressed the corpse fauna of many geographical regions, but generally neglected the southern African calliphorid species. In this study, forensically significant calliphorids from South Africa, Swaziland, Botswana and Zimbabwe and Australia were sequenced over an 1167 base pair region of the COI gene. Phylogenetic analysis was performed to examine the ability of the region to resolve species identities and taxonomic relationships between species. Analyses by neighbour-joining, maximum parsimony and maximum likelihood methods all showed the potential of this region to provide the necessary species-level identifications for application to post-mortem interval (PMI) estimation; however, higher level taxonomic relationships did vary according to method of analysis. Intraspecific variation was also considered in relation to determining suitable maximum levels of variation to be expected during analysis. Individuals of some species in the study represented populations from both South Africa and the east coast of Australia, yet maximum intraspecific variation over this gene region was calculated at 0.8%, with minimum interspecific variation at 3%, indicating distinct ranges of variation to be expected at intra- and interspecific levels. This region therefore appears to provide southern African forensic entomologists with a new technique for providing accurate identification for application to estimation of PMI.
- Full Text:
- Date Issued: 2003
- Authors: Harvey, M L , Mansell, M W , Villet, Martin H , Dadour, I R
- Date: 2003
- Language: English
- Type: text , Article
- Identifier: vital:6953 , http://hdl.handle.net/10962/d1011986
- Description: One major aspect of research in forensic entomology is the investigation of molecular techniques for the accurate identification of insects. Studies to date have addressed the corpse fauna of many geographical regions, but generally neglected the southern African calliphorid species. In this study, forensically significant calliphorids from South Africa, Swaziland, Botswana and Zimbabwe and Australia were sequenced over an 1167 base pair region of the COI gene. Phylogenetic analysis was performed to examine the ability of the region to resolve species identities and taxonomic relationships between species. Analyses by neighbour-joining, maximum parsimony and maximum likelihood methods all showed the potential of this region to provide the necessary species-level identifications for application to post-mortem interval (PMI) estimation; however, higher level taxonomic relationships did vary according to method of analysis. Intraspecific variation was also considered in relation to determining suitable maximum levels of variation to be expected during analysis. Individuals of some species in the study represented populations from both South Africa and the east coast of Australia, yet maximum intraspecific variation over this gene region was calculated at 0.8%, with minimum interspecific variation at 3%, indicating distinct ranges of variation to be expected at intra- and interspecific levels. This region therefore appears to provide southern African forensic entomologists with a new technique for providing accurate identification for application to estimation of PMI.
- Full Text:
- Date Issued: 2003
Morphometrics and reproduction of Terebrasabella heterouncinata (Polychaeta:Sabellidae), infesting abalone (Haliotis midae) from different culture environments
- Authors: Gray, Michael
- Date: 2003
- Subjects: Polychaeta , Sabellidae , Abalones -- Physiology , Abalones -- Nutrition , Abalone culture
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5384 , http://hdl.handle.net/10962/d1018231
- Description: In the late 1980's abalone culturalists noticed reduced growth rate and shell deformities in some abalone stocks. These problems were the result of infestations by a shell boring polychaete, Terebrasabella heterouncinata. Under intensive abalone culture conditions the level of infestation can reach epidemic proportions and there are often severe consequences for the host abalone. Heavy sabellid infestation levels have placed the economic viability of several South African farms under threat. This study formed part of an ongoing project that is aimed at investigating the basic biology of Terebrasabella heterouncinata. The majority of abalone farmers in South Africa feed their abalone either naturally occurring kelp (Ecklonia maxima) or the formulated abalone feed, Abfeed. Farmers have suggested that the use of Abfeed is associated with higher sabellid infestation levels and changing the abalone diet from Abfeed to kelp helps reduce sabellid infestation. Speculation has arisen indicating that older, slower growing abalone are more susceptible to sabellid infestation. The effect of host abalone diet history and their growth on sabellid settlement success, morphometries and reproduction was quantified. To better understand the plasticity of the expression of life history traits the variability of morphometric and reproductive characteristics was compared between different farm environments. And more...
- Full Text:
- Date Issued: 2003
- Authors: Gray, Michael
- Date: 2003
- Subjects: Polychaeta , Sabellidae , Abalones -- Physiology , Abalones -- Nutrition , Abalone culture
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5384 , http://hdl.handle.net/10962/d1018231
- Description: In the late 1980's abalone culturalists noticed reduced growth rate and shell deformities in some abalone stocks. These problems were the result of infestations by a shell boring polychaete, Terebrasabella heterouncinata. Under intensive abalone culture conditions the level of infestation can reach epidemic proportions and there are often severe consequences for the host abalone. Heavy sabellid infestation levels have placed the economic viability of several South African farms under threat. This study formed part of an ongoing project that is aimed at investigating the basic biology of Terebrasabella heterouncinata. The majority of abalone farmers in South Africa feed their abalone either naturally occurring kelp (Ecklonia maxima) or the formulated abalone feed, Abfeed. Farmers have suggested that the use of Abfeed is associated with higher sabellid infestation levels and changing the abalone diet from Abfeed to kelp helps reduce sabellid infestation. Speculation has arisen indicating that older, slower growing abalone are more susceptible to sabellid infestation. The effect of host abalone diet history and their growth on sabellid settlement success, morphometries and reproduction was quantified. To better understand the plasticity of the expression of life history traits the variability of morphometric and reproductive characteristics was compared between different farm environments. And more...
- Full Text:
- Date Issued: 2003
Multivariate morphometric analysis and behaviour of honeybees (Apis Mellifera L.) in the southern regions of Ethiopia
- Authors: Amssalu, Argaw Bezabeh
- Date: 2003
- Subjects: Honeybee -- Ethiopia -- Behavior Honeybee -- Ethiopia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5616 , http://hdl.handle.net/10962/d1003130
- Description: Morphometric and behavioural characteristics of honeybees, Apis mellifera were analysed using multivariate and bivariate statistical methods to characterise honeybees of southern Ethiopian region. A total of 33800 morphometric character measurements were taken from 2600 individual worker honeybees of 130 honeybee colonies collected at 26 sampling localities with an average inter-locality distance of 89km to determine the occurrence of morphoclusters. 117 experienced farmer beekeepers and beekeeping experts were interviewed on pre-tested questionnaire to investigate the behavioural characteristics of these honeybees in their respective areas. Morphometric characters associated with pigmentation and body size exhibited a higher discriminant power while forewing venation angles (B4, N23 and 026) lack discriminatory power to segregate honeybees in the southern Ethiopian region. Principal components and discriminant analyses using the most discriminatory morphological characters delineated four statistically distinct morphoclusters in the southern Ethiopian region: the smallest and yellow honeybees, A. m. woyi-gambella which are different from all African honeybees, occur in the western and southern lowlands; the small and yellowiest honeybees, Apis mellifera jemenitica in the eastern escarpment; the largest and darkest honeybees, Apis mellifera bandasii in the central and eastern highlands; and dark honeybees, Apis mellifera scutellata in the wet tropical forests. High intracolonial and intercolonial variances within and between the boundaries of the honeybee groups were detected. The former suggests areas of ecological instability, while the latter areas of transitional or natural hybridisation zones. These areas are characterised by transitional ecological zones having intermediate climate and physiography. Even though honeybees of the southern Ethiopian region are generally dark and small, they show a high tendency to reproductive swarming, migration and aggressiveness, great variation in pigmentation, size and behaviour were observed both within and between the groups. A. m. jemenitica honeybees have a high propensity to migration and less a tendency for reproductive swarming. A. m. bandasii and A. m. scutellata have a high inclination to reproductive swarming and the former has a lesser and the later intermediate propensity to migration. A. m. woyi-gambella honeybees have intermediate swarming and migration tendencies. These results revealed that reproductive swarming and migration are higher in resource-rich and resource-poor areas respectively. Honey plants of the central highlands of Ethiopia are predominantly herbaceous in nature and mainly grow on open and cultivated lands. The bulk of pollen collected came comparatively from few genera. Strong correlation was observed between the intensities of flowering and rainfall. Reproductive swarming and migration occur during high and low intensity of flowering respectively.
- Full Text:
- Date Issued: 2003
- Authors: Amssalu, Argaw Bezabeh
- Date: 2003
- Subjects: Honeybee -- Ethiopia -- Behavior Honeybee -- Ethiopia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5616 , http://hdl.handle.net/10962/d1003130
- Description: Morphometric and behavioural characteristics of honeybees, Apis mellifera were analysed using multivariate and bivariate statistical methods to characterise honeybees of southern Ethiopian region. A total of 33800 morphometric character measurements were taken from 2600 individual worker honeybees of 130 honeybee colonies collected at 26 sampling localities with an average inter-locality distance of 89km to determine the occurrence of morphoclusters. 117 experienced farmer beekeepers and beekeeping experts were interviewed on pre-tested questionnaire to investigate the behavioural characteristics of these honeybees in their respective areas. Morphometric characters associated with pigmentation and body size exhibited a higher discriminant power while forewing venation angles (B4, N23 and 026) lack discriminatory power to segregate honeybees in the southern Ethiopian region. Principal components and discriminant analyses using the most discriminatory morphological characters delineated four statistically distinct morphoclusters in the southern Ethiopian region: the smallest and yellow honeybees, A. m. woyi-gambella which are different from all African honeybees, occur in the western and southern lowlands; the small and yellowiest honeybees, Apis mellifera jemenitica in the eastern escarpment; the largest and darkest honeybees, Apis mellifera bandasii in the central and eastern highlands; and dark honeybees, Apis mellifera scutellata in the wet tropical forests. High intracolonial and intercolonial variances within and between the boundaries of the honeybee groups were detected. The former suggests areas of ecological instability, while the latter areas of transitional or natural hybridisation zones. These areas are characterised by transitional ecological zones having intermediate climate and physiography. Even though honeybees of the southern Ethiopian region are generally dark and small, they show a high tendency to reproductive swarming, migration and aggressiveness, great variation in pigmentation, size and behaviour were observed both within and between the groups. A. m. jemenitica honeybees have a high propensity to migration and less a tendency for reproductive swarming. A. m. bandasii and A. m. scutellata have a high inclination to reproductive swarming and the former has a lesser and the later intermediate propensity to migration. A. m. woyi-gambella honeybees have intermediate swarming and migration tendencies. These results revealed that reproductive swarming and migration are higher in resource-rich and resource-poor areas respectively. Honey plants of the central highlands of Ethiopia are predominantly herbaceous in nature and mainly grow on open and cultivated lands. The bulk of pollen collected came comparatively from few genera. Strong correlation was observed between the intensities of flowering and rainfall. Reproductive swarming and migration occur during high and low intensity of flowering respectively.
- Full Text:
- Date Issued: 2003
Mythic and theoretic aspects of the concept of 'the unconscious' in popular and psychological discourse
- Authors: Edwards, David J A
- Date: 2003
- Language: English
- Type: Article
- Identifier: vital:6227 , http://hdl.handle.net/10962/d1007777
- Description: From the introduction: In Greek mythology, Typhon was the youngest son of Gaea (the Earth) and Tartarus (the underworld). Typhon was not a beautiful baby. He was a grisly monster with a hundred dragons' heads. He was one of the Titans, a group of powerful and dangerous creatures who rebelled against Zeus, the King of the Gods. The rebellion was crushed and Typhon was imprisoned under Mount Etna, the volcano in Sicily which was active in classical times and remains active today. It was said that when Typhon raged, the earth shook and Etna erupted. Many such tales from mythology from all over world seem to dramatize aspects of our relationship with potent forces of which we have little understanding and over which we have little control. Many of these forces are less concrete than the forces of nature. They arise from our apprehension of our existential predicaments, our interpersonal vulnerability and the intensity of our own psychological pain. In many contemporary discourses this territory is referred to more neutrally as ‘the unconscious;’ but the unconscious will always elude our attempts to capture it in words.
- Full Text:
- Date Issued: 2003
- Authors: Edwards, David J A
- Date: 2003
- Language: English
- Type: Article
- Identifier: vital:6227 , http://hdl.handle.net/10962/d1007777
- Description: From the introduction: In Greek mythology, Typhon was the youngest son of Gaea (the Earth) and Tartarus (the underworld). Typhon was not a beautiful baby. He was a grisly monster with a hundred dragons' heads. He was one of the Titans, a group of powerful and dangerous creatures who rebelled against Zeus, the King of the Gods. The rebellion was crushed and Typhon was imprisoned under Mount Etna, the volcano in Sicily which was active in classical times and remains active today. It was said that when Typhon raged, the earth shook and Etna erupted. Many such tales from mythology from all over world seem to dramatize aspects of our relationship with potent forces of which we have little understanding and over which we have little control. Many of these forces are less concrete than the forces of nature. They arise from our apprehension of our existential predicaments, our interpersonal vulnerability and the intensity of our own psychological pain. In many contemporary discourses this territory is referred to more neutrally as ‘the unconscious;’ but the unconscious will always elude our attempts to capture it in words.
- Full Text:
- Date Issued: 2003