title: Structural analysis of the GH43 enzyme Xsa43E from Butyrivibrio proteoclasticus

authors: Till, Marisa

subjects: Butyrivibrio proteoclasticus

abstract: The rumen of dairy cattle can be thought of as a large, stable fermentation vat and as such it houses a large and diverse community of microorganisms. The bacterium Butyrivibrio proteoclasticus is a representative of a significant component of this microbial community. It is a xylan-degrading organism whose genome encodes a large number of open reading frames annotated as fibre-degrading enzymes. This suite of enzymes is essential for the organism to utilize the plant material within the rumen as a fuel source, facilitating its survival in this competitive environment. Xsa43E, a GH43 enzyme from B. proteoclasticus, has been structurally and functionally characterized. Here, the structure of selenomethionine-derived Xsa43E determined to 1.3 Å resolution using single-wavelength anomalous diffraction is reported. Xsa43E possesses the characteristic five-bladed β-propeller domain seen in all GH43 enzymes. GH43 enzymes can have a range of functions, and the functional characterization of Xsa43E shows it to be an arabinofuranosidase capable of cleaving arabinose side chains from short segments of xylan. Full functional and structural characterization of xylan-degrading enzymes will aid in creating an enzyme cocktail that can be used to completely degrade plant material into simple sugars. These molecules have a range of applications as starting materials for many industrial processes, including renewable alternatives to fossil fuels.

text: Structural analysis of the GH43 enzyme Xsa43E from Butyrivibrio proteoclasticus The rumen of dairy cattle can be thought of as a large, stable fermentation vat and as such it houses a large and diverse community of microorganisms. The bacterium Butyrivibrio proteoclasticus is a representative of a significant component of this microbial community. It is a xylan-degrading organism whose genome encodes a large number of open reading frames annotated as fibre-degrading enzymes. This suite of enzymes is essential for the organism to utilize the plant material within the rumen as a fuel source, facilitating its survival in this competitive environment. Xsa43E, a GH43 enzyme from B. proteoclasticus, has been structurally and functionally characterized. Here, the structure of selenomethionine-derived Xsa43E determined to 1.3 Å resolution using single-wavelength anomalous diffraction is reported. Xsa43E possesses the characteristic five-bladed β-propeller domain seen in all GH43 enzymes. GH43 enzymes can have a range of functions, and the functional characterization of Xsa43E shows it to be an arabinofuranosidase capable of cleaving arabinose side chains from short segments of xylan. Full functional and structural characterization of xylan-degrading enzymes will aid in creating an enzyme cocktail that can be used to completely degrade plant material into simple sugars. These molecules have a range of applications as starting materials for many industrial processes, including renewable alternatives to fossil fuels.

year: 2014-08-29

title: The Effects of Food Deprivation on Memory Performance

authors: Kerewaro, Jacob Louis

abstract: Previous research has noted that pigeon weights fluctuate over a calendar year with birds being heavier during the winter than the summer months. Given that food deprivation can be a motivator of behaviour, it is possible that the fluctuations in animals’ weights might impact performance in operant research, for example accuracy in a DMTS memory task. The effects of two different amounts of food deprivation on roosters performance in a delayed matching-to-sample (DMTS) procedure was measured. There were two conditions 75% and 95% ad libitum free feeding body weight. I attempted to assess whether a lower body weight produces more correct responses in a DMTS procedure. The results indicated that the roosters performed better when less food deprived. The last 10 sessions and the last 400 trials of both conditions was used to describe the memory performance and accuracy. There was a significant difference in the slope of the forgetting function when comparing the two conditions for the last 10 sessions, with no significant differences in the intercept. For the last 400 trials there was no significant difference for the slope or intercept when comparing the two conditions. A ceiling effect was seen to occur with some of the birds. The results from some of the roosters suggest that improved performance might occur due to exposure to the task. More accurate remembering occurred when the roosters changed from one condition to the other condition, suggesting that repeated exposure to the task increased memory performance and accuracy.

text: The Effects of Food Deprivation on Memory Performance Previous research has noted that pigeon weights fluctuate over a calendar year with birds being heavier during the winter than the summer months. Given that food deprivation can be a motivator of behaviour, it is possible that the fluctuations in animals’ weights might impact performance in operant research, for example accuracy in a DMTS memory task. The effects of two different amounts of food deprivation on roosters performance in a delayed matching-to-sample (DMTS) procedure was measured. There were two conditions 75% and 95% ad libitum free feeding body weight. I attempted to assess whether a lower body weight produces more correct responses in a DMTS procedure. The results indicated that the roosters performed better when less food deprived. The last 10 sessions and the last 400 trials of both conditions was used to describe the memory performance and accuracy. There was a significant difference in the slope of the forgetting function when comparing the two conditions for the last 10 sessions, with no significant differences in the intercept. For the last 400 trials there was no significant difference for the slope or intercept when comparing the two conditions. A ceiling effect was seen to occur with some of the birds. The results from some of the roosters suggest that improved performance might occur due to exposure to the task. More accurate remembering occurred when the roosters changed from one condition to the other condition, suggesting that repeated exposure to the task increased memory performance and accuracy.

year: 2017

title: Ideology is theft: Thoughts on the legitimacy of a Maori psychology

authors: Tamatea, Armon J.

subjects: Maori

abstract: ‘War, in fact, can be seen as a process of achieving equilibrium among unequal technologies’ (McLuhan, 1964) 
We are at war. As Western science and its accompanying technology expands the frontiers of knowledge at an ever-increasing rate, ‘indigenous’ perspectives of knowledge are exiled into the borderlands of special interest groups and localized research programmes. Mainstream scientific thought lays claim to objective interpretations of experience at the expense of alternative realities offered by emerging theories of knowledge. Furthermore, as localized worldviews (i.e., those derived from ancestral knowledge bases and pre-industrial or non-scientific premises) challenge existing paradigms, the inevitable interactions threaten to undermine the fidelity of this knowledge. One such arena where this ideological conflict is apparent is the growing field of Maori psychology.

text: Ideology is theft: Thoughts on the legitimacy of a Maori psychology ‘War, in fact, can be seen as a process of achieving equilibrium among unequal technologies’ (McLuhan, 1964) 
We are at war. As Western science and its accompanying technology expands the frontiers of knowledge at an ever-increasing rate, ‘indigenous’ perspectives of knowledge are exiled into the borderlands of special interest groups and localized research programmes. Mainstream scientific thought lays claim to objective interpretations of experience at the expense of alternative realities offered by emerging theories of knowledge. Furthermore, as localized worldviews (i.e., those derived from ancestral knowledge bases and pre-industrial or non-scientific premises) challenge existing paradigms, the inevitable interactions threaten to undermine the fidelity of this knowledge. One such arena where this ideological conflict is apparent is the growing field of Maori psychology.

year: 2008