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221.
Thierry Léveillard José-Alain Sahel 《Cellular and molecular life sciences : CMLS》2017,74(20):3649-3665
Visual perception by photoreceptors relies on the interaction of incident photons from light with a derivative of vitamin A that is covalently linked to an opsin molecule located in a special subcellular structure, the photoreceptor outer segment. The photochemical reaction produced by the photon is optimal when the opsin molecule, a seven-transmembrane protein, is embedded in a lipid bilayer of optimal fluidity. This is achieved in vertebrate photoreceptors by a high proportion of lipids made with polyunsaturated fatty acids, which have the detrimental property of being oxidized and damaged by light. Photoreceptors cannot divide, but regenerate their outer segments. This is an enormous energetic challenge that explains why photoreceptors metabolize glucose through aerobic glycolysis, as cancer cells do. Uptaken glucose produces metabolites to renew that outer segment as well as reducing power through the pentose phosphate pathway to protect photoreceptors against oxidative damage. 相似文献
222.
Zhenzhong Yu Jia Gao Olumuyiwa Igbalajobi Marek Skoneczny Marzena Sienko Agnieszka M.Maciejewska Jerzy Brzywczy Reinhard Fischer 《科学通报(英文版)》2021,(6):592-602
Phytochrome-dependent light signaling has been studied in several fungi.In Aspergillus nidulans light-stimulated phytochrome activates the high-osmolarity glyce... 相似文献
223.
Atmospheric oxidation capacity sustained by a tropical forest 总被引:2,自引:0,他引:2
Lelieveld J Butler TM Crowley JN Dillon TJ Fischer H Ganzeveld L Harder H Lawrence MG Martinez M Taraborrelli D Williams J 《Nature》2008,452(7188):737-740
Terrestrial vegetation, especially tropical rain forest, releases vast quantities of volatile organic compounds (VOCs) to the atmosphere, which are removed by oxidation reactions and deposition of reaction products. The oxidation is mainly initiated by hydroxyl radicals (OH), primarily formed through the photodissociation of ozone. Previously it was thought that, in unpolluted air, biogenic VOCs deplete OH and reduce the atmospheric oxidation capacity. Conversely, in polluted air VOC oxidation leads to noxious oxidant build-up by the catalytic action of nitrogen oxides (NO(x) = NO + NO2). Here we report aircraft measurements of atmospheric trace gases performed over the pristine Amazon forest. Our data reveal unexpectedly high OH concentrations. We propose that natural VOC oxidation, notably of isoprene, recycles OH efficiently in low-NO(x) air through reactions of organic peroxy radicals. Computations with an atmospheric chemistry model and the results of laboratory experiments suggest that an OH recycling efficiency of 40-80 per cent in isoprene oxidation may be able to explain the high OH levels we observed in the field. Although further laboratory studies are necessary to explore the chemical mechanism responsible for OH recycling in more detail, our results demonstrate that the biosphere maintains a remarkable balance with the atmospheric environment. 相似文献