title: Effect of oxidative treatment on the secondary structure of decoloured bloodmeal

authors: Hicks, Talia

abstract: Bloodmeal can be decoloured using peracetic acid resulting in a material with a pale-yellow colour which only needs sodium dodecyl sulphate, water and triethylene glycol to extrude into a semi-transparent bioplastic. Fourier-transform infrared (FTIR) spectroscopy using Synchrotron light was used to investigate the effect of peracetic acid treatment at various concentrations on the spatial distribution of secondary structures within particles of bloodmeal. Oxidation caused aggregation of helical structures into sheets and acetic acid suppressed sheet formation. Decolouring with peracetic acid led to particles with a higher degree of disorder at the outer edges and higher proportions of ordered structures at the core, consistent with the expected diffusion controlled heterogeneous phase decolouring reaction. The degradation of stabilizing intra- and intermolecular interactions and the presence of acetate ions results in increased chain mobility and greater amorphous content in the material, as evidenced by reduction in Tg and greater enthalpy of relaxation with increasing PAA concentration.

text: Effect of oxidative treatment on the secondary structure of decoloured bloodmeal Bloodmeal can be decoloured using peracetic acid resulting in a material with a pale-yellow colour which only needs sodium dodecyl sulphate, water and triethylene glycol to extrude into a semi-transparent bioplastic. Fourier-transform infrared (FTIR) spectroscopy using Synchrotron light was used to investigate the effect of peracetic acid treatment at various concentrations on the spatial distribution of secondary structures within particles of bloodmeal. Oxidation caused aggregation of helical structures into sheets and acetic acid suppressed sheet formation. Decolouring with peracetic acid led to particles with a higher degree of disorder at the outer edges and higher proportions of ordered structures at the core, consistent with the expected diffusion controlled heterogeneous phase decolouring reaction. The degradation of stabilizing intra- and intermolecular interactions and the presence of acetate ions results in increased chain mobility and greater amorphous content in the material, as evidenced by reduction in Tg and greater enthalpy of relaxation with increasing PAA concentration.

year: 2014

title: Structure and Function of AmtR in Mycobacterium smegmatis: Implications for Post-Transcriptional Regulation of Urea Metabolism through a Small Antisense RNA

authors: Petridis, Michael

subjects: Science & Technology

abstract: Soil-dwelling bacteria of the phylum actinomycetes generally harbor either GlnR or AmtR as a global regulator of nitrogen metabolism. Mycobacterium smegmatis harbors both of these canonical regulators; GlnR regulates the expression of key genes involved in nitrogen metabolism, while the function and signal transduction pathway of AmtR in M. smegmatis remains largely unknown. Here, we report the structure and function of the M. smegmatis AmtR and describe the role of AmtR in the regulation of nitrogen metabolism in response to nitrogen availability. To determine the function of AmtR in M. smegmatis, we performed genome-wide expression profiling comparing the wild-type versus an ΔamtR mutant and identified significant changes in the expression of 11 genes, including an operon involved in urea degradation. An AmtR consensus-binding motif (CTGTC-N4-GACAG) was identified in the promoter region of this operon, and ligand-independent, high-affinity AmtR binding was validated by both electrophoretic mobility shift assays and surface plasmon resonance measurements. We confirmed the transcription of a cis-encoded small RNA complementary to the gene encoding AmtR under nitrogen excess, and we propose a post-transcriptional regulatory mechanism for AmtR. The three-dimensional X-ray structure of AmtR at 2.0 Å revealed an overall TetR-like dimeric structure, and the alignment of the M. smegmatis AmtR and Corynebacterium glutamicum AmtR regulatory domains showed poor structural conservation, providing a potential explanation for the lack of M.smegmatisAmtRinteractionwith the adenylylated PII protein. Taken together, our data suggest an AmtR (repressor)/GlnR (activator) competitive binding mechanism for transcriptional regulation of urea metabolism that is controlled by a cis-encoded small antisense RNA.

text: Structure and Function of AmtR in Mycobacterium smegmatis: Implications for Post-Transcriptional Regulation of Urea Metabolism through a Small Antisense RNA Soil-dwelling bacteria of the phylum actinomycetes generally harbor either GlnR or AmtR as a global regulator of nitrogen metabolism. Mycobacterium smegmatis harbors both of these canonical regulators; GlnR regulates the expression of key genes involved in nitrogen metabolism, while the function and signal transduction pathway of AmtR in M. smegmatis remains largely unknown. Here, we report the structure and function of the M. smegmatis AmtR and describe the role of AmtR in the regulation of nitrogen metabolism in response to nitrogen availability. To determine the function of AmtR in M. smegmatis, we performed genome-wide expression profiling comparing the wild-type versus an ΔamtR mutant and identified significant changes in the expression of 11 genes, including an operon involved in urea degradation. An AmtR consensus-binding motif (CTGTC-N4-GACAG) was identified in the promoter region of this operon, and ligand-independent, high-affinity AmtR binding was validated by both electrophoretic mobility shift assays and surface plasmon resonance measurements. We confirmed the transcription of a cis-encoded small RNA complementary to the gene encoding AmtR under nitrogen excess, and we propose a post-transcriptional regulatory mechanism for AmtR. The three-dimensional X-ray structure of AmtR at 2.0 Å revealed an overall TetR-like dimeric structure, and the alignment of the M. smegmatis AmtR and Corynebacterium glutamicum AmtR regulatory domains showed poor structural conservation, providing a potential explanation for the lack of M.smegmatisAmtRinteractionwith the adenylylated PII protein. Taken together, our data suggest an AmtR (repressor)/GlnR (activator) competitive binding mechanism for transcriptional regulation of urea metabolism that is controlled by a cis-encoded small antisense RNA.

year: 2016-10-23

title: Mentoring and teaching in academic settings:  Professional and cultural identities from one Pākehā’s perspective

authors: Middleton, Sue

subjects: biculturalism

abstract: When invited to respond to the paper on “Mentoring Māori in a Pākehā framework” by Hook, Waaka and Raumati (2007), I hesitated. Mentoring was not a term I had previously used in my professional thinking or academic writing: unlike Barbara Grant (Ratima & Grant, 2007), I had not been involved in formal mentoring programmes or immersed myself in the mentoring literature. As a Pākehā, I was not qualified to evaluate the authors’ definition of a Māori framework. At first glance, the target paper’s focus seemed to be on mentoring in commercial, rather than academic workplaces. My experience had been as a teacher, the last 30 years having been in a university School of Education. I was persuaded to undertake this commentary on the grounds that academic work involves nurturing, advising and supporting younger or less experienced colleagues, as well as students – tasks identified as mentoring in the Hook et al. paper. The following comments are informed by my everyday practices as teacher, thesis supervisor and researcher, and by my former management roles as an assistant dean of graduate studies and head of department. My angle of vision and conceptual resources are those of a (Pākehā and feminist) sociologist of education.

text: Mentoring and teaching in academic settings:  Professional and cultural identities from one Pākehā’s perspective When invited to respond to the paper on “Mentoring Māori in a Pākehā framework” by Hook, Waaka and Raumati (2007), I hesitated. Mentoring was not a term I had previously used in my professional thinking or academic writing: unlike Barbara Grant (Ratima & Grant, 2007), I had not been involved in formal mentoring programmes or immersed myself in the mentoring literature. As a Pākehā, I was not qualified to evaluate the authors’ definition of a Māori framework. At first glance, the target paper’s focus seemed to be on mentoring in commercial, rather than academic workplaces. My experience had been as a teacher, the last 30 years having been in a university School of Education. I was persuaded to undertake this commentary on the grounds that academic work involves nurturing, advising and supporting younger or less experienced colleagues, as well as students – tasks identified as mentoring in the Hook et al. paper. The following comments are informed by my everyday practices as teacher, thesis supervisor and researcher, and by my former management roles as an assistant dean of graduate studies and head of department. My angle of vision and conceptual resources are those of a (Pākehā and feminist) sociologist of education.

year: 2007-12