title: Enzymic approach to eurythermalism of Alvinella pompejana and its Episymbionts

authors: Lee, Charles Kai-Wu

subjects: biology

abstract: The equilibrium model, which describes the influence of temperature on enzyme activity, has been established as a valid and useful tool for characterizing enzyme eurythermalism and thermophily. By introducing Keq, a temperature-dependent equilibrium constant for the interconversion between Eact, the active form of enzyme, and Einact, a reversibly inactive form of enzyme, the equilibrium model currently provides the most complete description of the enzyme-temperature relationship; its derived parameters are intrinsic and apparently universal and, being derived under reaction conditions, potentially have physiological significance. One of these parameters, Teq, correlates with host growth temperature better than enzyme stability does. The vent-dwelling annelid Alvinella pompejana has been reported as an extremely eurythermal organism, and the symbiotic complex microbial community associated with its dorsal surface is likely to experience similar environmental thermal conditions. The A. pompejana episymbiont community, predominantly composed of epsilonproteobacteria, has been analyzed metagenomically, enabling direct retrieval of genes coding for enzymes suitable for equilibrium model applications. Two such genes, coding for isopropylmalate dehydrogenase and glutamate dehydrogenase, have been isolated from the A. pompejana episymbionts, heterologously expressed, and shown by reverse transcription-quantitative PCR to be actively expressed. The equilibrium model parameters of characterized expression products suggested that enzyme eurythermalism constitutes part of the thermal adaptation strategy employed by the episymbionts. Moreover, the enzymes' thermal characteristics correspond to their predicted physiological roles and the abundance and expression of the corresponding genes. This paper demonstrates the use of the equilibrium model as part of a top-down metagenomic approach to studying temperature adaptation of uncultured organisms.

text: Enzymic approach to eurythermalism of Alvinella pompejana and its Episymbionts The equilibrium model, which describes the influence of temperature on enzyme activity, has been established as a valid and useful tool for characterizing enzyme eurythermalism and thermophily. By introducing Keq, a temperature-dependent equilibrium constant for the interconversion between Eact, the active form of enzyme, and Einact, a reversibly inactive form of enzyme, the equilibrium model currently provides the most complete description of the enzyme-temperature relationship; its derived parameters are intrinsic and apparently universal and, being derived under reaction conditions, potentially have physiological significance. One of these parameters, Teq, correlates with host growth temperature better than enzyme stability does. The vent-dwelling annelid Alvinella pompejana has been reported as an extremely eurythermal organism, and the symbiotic complex microbial community associated with its dorsal surface is likely to experience similar environmental thermal conditions. The A. pompejana episymbiont community, predominantly composed of epsilonproteobacteria, has been analyzed metagenomically, enabling direct retrieval of genes coding for enzymes suitable for equilibrium model applications. Two such genes, coding for isopropylmalate dehydrogenase and glutamate dehydrogenase, have been isolated from the A. pompejana episymbionts, heterologously expressed, and shown by reverse transcription-quantitative PCR to be actively expressed. The equilibrium model parameters of characterized expression products suggested that enzyme eurythermalism constitutes part of the thermal adaptation strategy employed by the episymbionts. Moreover, the enzymes' thermal characteristics correspond to their predicted physiological roles and the abundance and expression of the corresponding genes. This paper demonstrates the use of the equilibrium model as part of a top-down metagenomic approach to studying temperature adaptation of uncultured organisms.

year: 2007

title: A low-toxicity method for the separation of lanosterol and dihydrolanosterol from commercial mixtures

authors: Kavtaradze, Levan K.

subjects: lanosterol

abstract: We describe an inexpensive, low-toxicity and high-yielding method for the production of pure lanosterol and dihydrolanosterol from the commercially available mixture. Optimum conditions are presented for the one-pot production of the intermediate 24,25 vicinal diol of lanosterol acetate (via either epoxidation or hydroxyhalogenation) which is readily separated from the unreacted dihydrolanosterol acetate. The lanosterol diol can then be converted to pure (>97%) lanosterol. Hypophosphorous acid was used for both the conversion of the epoxide to the diol, and as a catalyst for the hydroxyhalogenation by N-halosuccinimides of the olefinic bond.

text: A low-toxicity method for the separation of lanosterol and dihydrolanosterol from commercial mixtures We describe an inexpensive, low-toxicity and high-yielding method for the production of pure lanosterol and dihydrolanosterol from the commercially available mixture. Optimum conditions are presented for the one-pot production of the intermediate 24,25 vicinal diol of lanosterol acetate (via either epoxidation or hydroxyhalogenation) which is readily separated from the unreacted dihydrolanosterol acetate. The lanosterol diol can then be converted to pure (>97%) lanosterol. Hypophosphorous acid was used for both the conversion of the epoxide to the diol, and as a catalyst for the hydroxyhalogenation by N-halosuccinimides of the olefinic bond.

year: 2004-09-01

title: Relational and culturally responsive supervision of doctoral students working in Māori contexts: Inspirations from the Kingitanga

authors: Glynn, Ted

subjects: Relational and culturally responsive supervision

abstract: There is much to celebrate in the greatly increased number of Māori and non-Māori students in New Zealand tertiary institutions undertaking doctoral research on issues of importance to Māori.
However, in honouring their commitments to the Treaty of Waitangi, tertiary institutions need to ensure that Māori doctoral students and their Māori communities maintain their right to define their own research questions, research paradigms and methodologies. As supervisors of doctoral research students investigating issues of significance to Māori people, it is essential that we learn to position ourselves as visitors in someone else’s cultural space, as partners in the Treaty of Waitangi, and as co-constructors of knowledge and research methodology rather than as experts and gatekeepers (Berryman, SooHoo, & Nevin, 2013; Glynn, 2012).

This paper was occasioned by an invitation from the organisers of the annual Kingitanga Day cultural and educational programme at the University of Waikato. The Kingitanga movement has much to teach us about how to frame and conduct research that responds to long-standing injustices that have marginalised Māori people. The Kingitanga has inspired us through the resistance, resilience, agency and humility of its leaders in asserting their right to define the effects of historic and contemporary injustices, and the right to define their own responses to these injustices.

In this paper, we explore some of the relational and culturally responsive understandings we have arrived at from supervising the research of four doctoral candidates in Education (two Māori and two non-Māori). This research has been designed to promote the success and wellbeing of Māori students in mainstream schools, addressing historic and ongoing injustices experienced by Māori students and their whānau and communities.

text: Relational and culturally responsive supervision of doctoral students working in Māori contexts: Inspirations from the Kingitanga There is much to celebrate in the greatly increased number of Māori and non-Māori students in New Zealand tertiary institutions undertaking doctoral research on issues of importance to Māori.
However, in honouring their commitments to the Treaty of Waitangi, tertiary institutions need to ensure that Māori doctoral students and their Māori communities maintain their right to define their own research questions, research paradigms and methodologies. As supervisors of doctoral research students investigating issues of significance to Māori people, it is essential that we learn to position ourselves as visitors in someone else’s cultural space, as partners in the Treaty of Waitangi, and as co-constructors of knowledge and research methodology rather than as experts and gatekeepers (Berryman, SooHoo, & Nevin, 2013; Glynn, 2012).

This paper was occasioned by an invitation from the organisers of the annual Kingitanga Day cultural and educational programme at the University of Waikato. The Kingitanga movement has much to teach us about how to frame and conduct research that responds to long-standing injustices that have marginalised Māori people. The Kingitanga has inspired us through the resistance, resilience, agency and humility of its leaders in asserting their right to define the effects of historic and contemporary injustices, and the right to define their own responses to these injustices.

In this paper, we explore some of the relational and culturally responsive understandings we have arrived at from supervising the research of four doctoral candidates in Education (two Māori and two non-Māori). This research has been designed to promote the success and wellbeing of Māori students in mainstream schools, addressing historic and ongoing injustices experienced by Māori students and their whānau and communities.

year: 2015