The lethal effect produced by sunlight in bacteria depends on the photodynamic action of the ultraviolet component of the radiation. Neither the reactive oxygen species involved nor the targets for damage have been ce...The lethal effect produced by sunlight in bacteria depends on the photodynamic action of the ultraviolet component of the radiation. Neither the reactive oxygen species involved nor the targets for damage have been certainly identified, and the aim of this study was to address these issues. During exposures to natural sunlight, photo-protection provided by nitrogen sparging was compared with which provided by the addition of L-histidine （an efficient scavenger for hydroxyl radical and singlet oxygen） or mannitol （an hydroxyl radical scavenger which reacts poorly with singlet oxygen） to the irradiation medium. Both scavengers reproduced for the most part the effect of oxygen depletion, indicating that damage depends mainly on hydroxyl radical generation. Survival of irradiated bacteria decreased considerably when they were cultured using a substrate unsuitable for fermentation, suggesting that respiration impairment is a key factor in cell killing. This observation is in keeping with the notion that the respiratory chain is the main target for the action of sunlight in Escherichia coli.展开更多
The C-H and C-C bonds are abundant in organic compounds,yet generally inert in chemical transformations.Therefore,direct functionalization of inert chemical bonds remains challenging.The fluorine-containing compounds ...The C-H and C-C bonds are abundant in organic compounds,yet generally inert in chemical transformations.Therefore,direct functionalization of inert chemical bonds remains challenging.The fluorine-containing compounds are of special interest for their uses in medicinal chemistry.Direct fluorination of C-H and C-C bonds undoubtedly represents one of the most ideal and attractive approaches to incorporate fluorine atom into complex molecules.Herein,we summarize the recent advances in radical-mediated C-H and C-C bond fluorination.Three types of transformations are discussed:(1)direct C-H abstraction/fluorination of alkanes;(2)decarboxylative fluorination of alkyl carboxylic acids;(3)ring-opening fluorination.展开更多
Transition-metal-salt-mediated radical reactions of fullerenes have attracted extensive attention as a new and important method for fullerene functionalization. The application of relatively cheap and easily available...Transition-metal-salt-mediated radical reactions of fullerenes have attracted extensive attention as a new and important method for fullerene functionalization. The application of relatively cheap and easily available ferric perchlorate (Fe(ClO 4 ) 3 ) to the synthesis of [60]fullerene (C 60 ) has demonstrated remarkable advantages and afforded a series of novel fullerene derivatives. In this review we present our recent progress in this area and summarize the reactions of C 60 with malonate esters, β-keto esters, nitriles, aldehydes/ketones, and arylboronic acids in the presence of Fe(ClO 4 ) 3 to afford the C 60-fused disubstituted lactones, C 60-fused hemiketal, C 60-fused dihydrofuran, C 60-fused oxazoles, C 60-fused 1,3-dioxolanes, and fullerenyl boronic esters. The possible reaction mechanisms for the above-mentioned reactions are also described in detail.展开更多
文摘The lethal effect produced by sunlight in bacteria depends on the photodynamic action of the ultraviolet component of the radiation. Neither the reactive oxygen species involved nor the targets for damage have been certainly identified, and the aim of this study was to address these issues. During exposures to natural sunlight, photo-protection provided by nitrogen sparging was compared with which provided by the addition of L-histidine （an efficient scavenger for hydroxyl radical and singlet oxygen） or mannitol （an hydroxyl radical scavenger which reacts poorly with singlet oxygen） to the irradiation medium. Both scavengers reproduced for the most part the effect of oxygen depletion, indicating that damage depends mainly on hydroxyl radical generation. Survival of irradiated bacteria decreased considerably when they were cultured using a substrate unsuitable for fermentation, suggesting that respiration impairment is a key factor in cell killing. This observation is in keeping with the notion that the respiratory chain is the main target for the action of sunlight in Escherichia coli.
基金supported by Soochow University,the National Natural Science Foundation of China(21402134)the Natural Science Foundation of Jiangsu Province(BK20140306)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘The C-H and C-C bonds are abundant in organic compounds,yet generally inert in chemical transformations.Therefore,direct functionalization of inert chemical bonds remains challenging.The fluorine-containing compounds are of special interest for their uses in medicinal chemistry.Direct fluorination of C-H and C-C bonds undoubtedly represents one of the most ideal and attractive approaches to incorporate fluorine atom into complex molecules.Herein,we summarize the recent advances in radical-mediated C-H and C-C bond fluorination.Three types of transformations are discussed:(1)direct C-H abstraction/fluorination of alkanes;(2)decarboxylative fluorination of alkyl carboxylic acids;(3)ring-opening fluorination.
基金supported by the National Natural Science Foundation of China (20972145, 21132007, 21102041)National Basic Research Program of China (2011CB921402)Scientific Research Foundation of Education Commission of Hubei Province (Q20120113)
文摘Transition-metal-salt-mediated radical reactions of fullerenes have attracted extensive attention as a new and important method for fullerene functionalization. The application of relatively cheap and easily available ferric perchlorate (Fe(ClO 4 ) 3 ) to the synthesis of [60]fullerene (C 60 ) has demonstrated remarkable advantages and afforded a series of novel fullerene derivatives. In this review we present our recent progress in this area and summarize the reactions of C 60 with malonate esters, β-keto esters, nitriles, aldehydes/ketones, and arylboronic acids in the presence of Fe(ClO 4 ) 3 to afford the C 60-fused disubstituted lactones, C 60-fused hemiketal, C 60-fused dihydrofuran, C 60-fused oxazoles, C 60-fused 1,3-dioxolanes, and fullerenyl boronic esters. The possible reaction mechanisms for the above-mentioned reactions are also described in detail.
