St. John's, Newfoundland and Labrador, Canada

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Faculty of Medicine
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Department of Biology
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Department of Earth Sciences
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    ABSTRACT: Rubisco is the most abundant protein on Earth that serves as the primary engine of carbon assimilation. It is characterized by a slow rate and low specificity for CO2 leading to photorespiration. We analyze here the challenges of operation of this enzyme as the main carbon fixation engine. The high concentration of Rubisco exceeds that of its substrate CO2 by 2–3 orders of magnitude; however, the total pool of available carbon in chloroplast, i.e., mainly bicarbonate, is comparable to the concentration of Rubisco active sites. This makes the reactant stationary assumption (RSA), which is essential as a condition of satisfying the Michaelis–Menten (MM) kinetics, valid if we assume that the delivery of CO2 from this pool is not limiting. The RSA is supported by active carbonic anhydrases (CA) that quickly equilibrate bicarbonate and CO2 pools and supply CO2 to Rubisco. While the operation of stromal CA is independent of light reactions, the thylakoidal CA associated with PSII and pumping CO2 from the thylakoid lumen is coordinated with the rate of electron transport, water splitting and proton gradient across the thylakoid membrane. At high CO2 concentrations, CA becomes less efficient (the equilibrium becomes unfavorable), so a deviation from the MM kinetics is observed, consistent with Rubisco reaching its Vmax at approximately 50% lower level than expected from the classical MM curve. Previously, this deviation was controversially explained by the limitation of RuBP regeneration. At low ambient CO2 and correspondingly limited capacity of the bicarbonate pool, its depletion at Rubisco sites is relieved in that the enzyme utilizes O2 instead of CO2, i.e., by photorespiration. In this process, CO2 is supplied back to Rubisco, and the chloroplastic redox state and energy level are maintained. It is concluded that the optimal performance of photosynthesis is achieved via the provision of continuous CO2 supply to Rubisco by carbonic anhydrases and photorespiration.
    Frontiers in Plant Science 02/2015; 6:106. DOI:10.3389/fpls.2015.00106
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    ABSTRACT: Several technological advancements exist for the purpose of disabling baited traps if they are lost or abandoned at sea. In this study, we investigated various biodegradable twines for their potential use in the snow crab (Chionoecetes opilio) fishery off Newfoundland and Labrador, Canada. The twines were deployed at sea for a duration of 124 days to measure degradation in breaking strength (kgf) over time. Results revealed significant variation in degradation rates among the twine types tested. Among the best performing twines, was the 3-ply cotton 96-thread twine. This twine exhibited a rapid and noticeable decline in breaking strength over the period of study with a total reduction of 63% of the initial strength upon conclusion of the study. This particular twine is now a mandatory condition of licence for all fishing enterprises targeting snow crab in the province of Newfoundland and Labrador.
    Fisheries Research 01/2015; 161:21–23. DOI:10.1016/j.fishres.2014.06.007
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    ABSTRACT: A direct ethanol fuel cell has been operated under sinusoidal (AC) potential cycling conditions in order to increase the yield of carbon dioxide and thereby increase cell efficiency relative to operation at a fixed potential. At 80 °C, faradaic yields of CO2 as high as 25% have been achieved with a PtRu anode catalyst, while the maximum CO2 production at constant potential was 13%. The increased yields under cycling conditions have been attributed to periodic oxidative stripping of adsorbed CO. These results will be important in the optimization of operating conditions for direct ethanol fuel cells, where the benefits of potential cycling are projected to increase as catalysts that produce CO2 more efficiently are implemented.
    Journal of Power Sources 12/2014; 268:439–442. DOI:10.1016/j.jpowsour.2014.06.075

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    St. John's, Newfoundland and Labrador, Canada
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    www.mun.ca
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Medicine and science in sports and exercise 01/2014; 46(1):131-42. DOI:10.1249/MSS.0b013e3182a123db
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