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  • 1
    Publication Date: 2012-06-23
    Description: Ecosystem respiration is the biotic conversion of organic carbon to carbon dioxide by all of the organisms in an ecosystem, including both consumers and primary producers. Respiration exhibits an exponential temperature dependence at the subcellular and individual levels, but at the ecosystem level respiration can be modified by many variables including community abundance and biomass, which vary substantially among ecosystems. Despite its importance for predicting the responses of the biosphere to climate change, it is as yet unknown whether the temperature dependence of ecosystem respiration varies systematically between aquatic and terrestrial environments. Here we use the largest database of respiratory measurements yet compiled to show that the sensitivity of ecosystem respiration to seasonal changes in temperature is remarkably similar for diverse environments encompassing lakes, rivers, estuaries, the open ocean and forested and non-forested terrestrial ecosystems, with an average activation energy similar to that of the respiratory complex (approximately 0.65 electronvolts (eV)). By contrast, annual ecosystem respiration shows a substantially greater temperature dependence across aquatic (approximately 0.65 eV) versus terrestrial ecosystems (approximately 0.32 eV) that span broad geographic gradients in temperature. Using a model derived from metabolic theory, these findings can be reconciled by similarities in the biochemical kinetics of metabolism at the subcellular level, and fundamental differences in the importance of other variables besides temperature-such as primary productivity and allochthonous carbon inputs-on the structure of aquatic and terrestrial biota at the community level.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Yvon-Durocher, Gabriel -- Caffrey, Jane M -- Cescatti, Alessandro -- Dossena, Matteo -- del Giorgio, Paul -- Gasol, Josep M -- Montoya, Jose M -- Pumpanen, Jukka -- Staehr, Peter A -- Trimmer, Mark -- Woodward, Guy -- Allen, Andrew P -- England -- Nature. 2012 Jul 26;487(7408):472-6. doi: 10.1038/nature11205.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉School of Biological & Chemical Sciences, Queen Mary University of London, London E1 4NS, UK. g.yvon-durocher@exeter.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22722862" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biomass ; Biota ; Carbon/*metabolism ; Carbon Dioxide/*metabolism ; Cell Respiration ; Data Collection ; *Ecosystem ; *Global Warming ; Humans ; Kinetics ; Lakes ; Marine Biology ; *Oxygen Consumption ; Photosynthesis ; Rivers ; Seasons ; Seawater ; *Temperature ; Time Factors ; Trees/metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    ISSN: 0173-0835
    Keywords: Enantiomeric separation ; Charged β-cyclodextrins ; Dansyl-amino acids ; Capillary electrophoresis ; Histamine-modified β-cyclodextrins ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Two novel monosubstituted β-cyclodextrins (CD) bearing the histamine moiety linked to the upper CD rim, either through the amino group or the imidazole nitrogen 1N, CD-hm and CD-mh, were successfully used as chiral selectors in capillary electrophoresis for the enantiomeric discrimination of dansyl (Dns)-amino acids. Good results were obtained by using low concentrations of the selectors (1-3 mM). The effect of pH on the chiral discrimination was studied in order to modulate the number and the position of the positive charges. By increasing the pH from 5 to 7.5, chiral discrimination decreased along with the deprotonation of the imidazolyl moiety. Inversion of the migration order was observed with the two CDs, depending on the relative position of the charged moieties on the upper rim. Ion pair interaction coupled to inclusion complexation seems to account for the discrimination process. The effects of the temperature, CD concentration and capillary length on chiral resolution were also examined.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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