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ESR STUDIES ON THE SEMIQUINONE RADICAL ANIONS OF HYPOCRELLIN B AND ITS DERIVATIVES AND THE PRODUCTION OF ^(1)O_(2),O_(2)^(█*)
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作者 王志军 马良 +2 位作者 张曼华 蒋丽金 陈德文 《Chinese Science Bulletin》 SCIE 1992年第12期1007-1011,共5页
Ⅰ. INTRODUCTIONHypocrellins are 3, 10-dihydroxyl-4, 9-perylenequinone derivatives. They are potent inhibitors of cancer cells. Besides <sup>1</sup>O<sub>2</sub> and O<sub>2</sub>&l... Ⅰ. INTRODUCTIONHypocrellins are 3, 10-dihydroxyl-4, 9-perylenequinone derivatives. They are potent inhibitors of cancer cells. Besides <sup>1</sup>O<sub>2</sub> and O<sub>2</sub><sup>,</sup> other radicals could also be involved in the effects of Hypocrellins on the photosensitization of erythrocyte membranes. The ESR signal with hyperfine structures could be obtained after illumination of Hypocrellin A, B (HA, 展开更多
关键词 hypocrellins(HA and HB) semiquinone radical anions ^(1)O_(2) O_(2)^(█*) ESR
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Radical Stabilization in Dissolved Humates
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作者 Barbora Bakajová Ray von Wandruszka 《Open Journal of Physical Chemistry》 2011年第3期55-60,共6页
Quinoid entities, in which quinone and hydroquinone groups equilibrate via a semiquinone radical intermediate, are a common structural feature in humic materials. The electron paramagnetic resonance (EPR) signals of t... Quinoid entities, in which quinone and hydroquinone groups equilibrate via a semiquinone radical intermediate, are a common structural feature in humic materials. The electron paramagnetic resonance (EPR) signals of these radicals are significantly enhanced in the presence of diamagnetic divalent metal ions such as Mg2+, while monovalent ions do not show the effect. The addition of trivalent ions leads to rapid precipitation, leaving little room for observation. It was noted that the metal ions producing EPR signal enhancement were also underwent effective bridging interactions with humic subunits, forming pseudomicellar structures. Particle growth determined through dynamic light scattering measurements coincided with the onset of EPR signal enhancement, and surface tension measurements further corroborated the coincidence of aggregation. The addition of a chaotrope (urea), which broke up the humic structures, eliminated the EPR signal increases. These observations strongly suggested that bridging interactions by divalent metal ions, and the intramo- lecular aggregation that accompanied it, led to significant stabilization of semiquinone radicals within the humic structure. 展开更多
关键词 HUMIC Acid semiquinone EPR Enhancement BRIDGING Interactions Aggregation RADICAL STABILIZATION
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Quantification of the redox properties of microplastics and their effect on arsenite oxidation
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作者 Lin Chen Dengjun Wang +5 位作者 Tianran Sun Tingting Fan Song Wu Guodong Fang Min Yang Dongmei Zhou 《Fundamental Research》 CAS CSCD 2023年第5期777-785,共9页
Microplastics have attracted global concern.The environmental-weathering processes control their fate,transport,transformation,and toxicity to wildlife and human health,but their impacts on biogeochemical redox proces... Microplastics have attracted global concern.The environmental-weathering processes control their fate,transport,transformation,and toxicity to wildlife and human health,but their impacts on biogeochemical redox processes remain largely unknown.Herein,multiple spectroscopic and electrochemical approaches in concert with wet-chemistry analyses were employed to characterize the redox properties of weathered microplastics.The spectroscopic results indicated that weathering of phenol-formaldehyde resins(PFs)by hydrogen peroxide(H2O2)led to a slight decrease in the content of phenol functional groups,accompanied by an increase in semiquinone radicals,quinone,and carboxylic groups.Electrochemical and wet-chemistry quantifications,coupled with microbial-chemical characterizations,demonstrated that the PFs exhibited appreciable electron-donating capacity(0.264-1.15 mmol e-g^(-1))and electron-accepting capacity(0.120-0.300 mmol e-g^(-1)).Specifically,the phenol groups and semiquinone radicals were responsible for the electron-donating capacity,whereas the quinone groups dominated the electron-accepting capacity.The reversible redox peaks in the cyclic voltammograms and the enhanced electron-donating capacity after accepting electrons from microbial reduction demonstrated the reversibility of the electron-donating and-accepting reactions.More importantly,the electron-donating phenol groups and weathering-induced semiquinone radicals were found to mediate the production of H2O2 from oxygen for arsenite oxidation.In addition to the H2O2-weathered PFs,the ozone-aged PF and polystyrene were also found to have electron-donating and arsenite-oxidation capacity.This study reports important redox properties of microplastics and their effect in mediating contaminant transformation.These findings will help to better understand the fate,transformation,and biogeochemical roles of microplastics on element cycling and contaminant fate. 展开更多
关键词 Microplastics WEATHERING Redox property semiquinone radicals Electron-donating and-accepting capacity Arsenite oxidation
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Photogeneration of the free radicals and singlet oxygen by chrysophanol from rheum 被引量:3
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作者 RAO Jing1,2, XIE Jie1, ZHAO Jingquan1 & ZHU Teng2 1. Key Laboratory of Photochemistry, Center for Molecular Science, Institute of Chemistry, The Chinese Academy of Sciences, Beijing 100080, China 2. University of Science and Technology Beijing, Beijing 10083, China 《Science China Chemistry》 SCIE EI CAS 2004年第5期381-387,共7页
In the current work, chryosphanol (MHAQ) was isolated and purified from rheum, and the photosensitization activities were studied. In nitrogen-saturated DMSO solution, irradia- tion of chryosphanol (MHAQ) with visible... In the current work, chryosphanol (MHAQ) was isolated and purified from rheum, and the photosensitization activities were studied. In nitrogen-saturated DMSO solution, irradia- tion of chryosphanol (MHAQ) with visible light (>430 nm) produced the semiquinone radical anions (MHAQ??), which was intensified significantly by an electron donor NADH, suggesting electron transfer between the excited and ground state photosensitizer molecules. In an air-saturated DMSO solution, superoxide radical anions (O2 ), trapped by DMPO, were detected. ?? It was proved that O2 was not originated from the singlet oxygen (1O2) but dependent on DMPO, ?? chrysophanol, oxygen and the irradiation time. The singlet oxygen and OH could also be pro- ? duced by the photosensitization of the photosensitizer. These suggest that chrysophanol pos- sesses the photosensitization activity via Type I mechanism and Type II mechanism. To evaluate the photosensitization activities of MHAQ, emodin and mixed anthraquinone derivatives ex- tracted from rheum, the relative productivities of O2 were estimated to be 1.8, 1.1 and 1.0 re- ?? spectively and the quantum yields for singlet oxygen to be 0.36, 0.53 and 0.14 respectively. Therefore, these low-cost pigments may be potentially used as phototherapeutic medicine for some kind of vascular diseases or photo-activated pesticides. 展开更多
关键词 chrysophanol ESR semiquinone RADICAL anions superoxide RADICAL anions hydroxyl radical singlet oxygen.
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Photochemistry of hypocrellin derivatives under anaerobic conditions 被引量:2
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作者 Yuying He An Jingyi Lijin Jiang 《Chinese Science Bulletin》 SCIE EI CAS 2000年第7期597-603,共7页
To improve the red absorption and solubility of hypocrellin, we have synthesized a series of hypocrellin B derivatives. The pnotochemistry of these new compounds in anaerobic media has been investigated by using elect... To improve the red absorption and solubility of hypocrellin, we have synthesized a series of hypocrellin B derivatives. The pnotochemistry of these new compounds in anaerobic media has been investigated by using electronic paramagnetic resonance (EPR) and spectrophotometric methods. The semiquinone anion radicals can be produced by self-electron transfer on irradiation, with the formation efficiency and EPR hyperfine structures of the semiquinone anion radicals dependent on the structures of the derivatives. When an electron donor is present, the electron transfer from electron donor to hypocrellin B derivatives enhanced the production of the corresponding semiquinone anion radical; in addition, the semiquinone anion radical and hydroquinone can be detected spectrophotometrically. Structural modifications exert little effect on the absorption position of semiquinone anion radical and hydroquinone, but influence their formation efficiency significantly. 展开更多
关键词 HYPOCRELLIN B DERIVATIVES semiquinone anion radical HYDROQUINONE electron PARAMAGNETIC resonance (EPR) spectrophotometry.
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Interaction between hypocrellin and aliphatic amines 被引量:1
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作者 张曼华 陈申 +2 位作者 夏万林 蒋丽金 陈德文 《Science China Chemistry》 SCIE EI CAS 1996年第6期568-576,共9页
The interaction of hypocrellin, including hypocrellin A (HA) and hypocrellin B (HB), with aliphatic amines in deaerated solutions has been studied by ESR and nanosecond transient absorption spectra. In polar solvents,... The interaction of hypocrellin, including hypocrellin A (HA) and hypocrellin B (HB), with aliphatic amines in deaerated solutions has been studied by ESR and nanosecond transient absorption spectra. In polar solvents, the acid-base interaction between hypocrellin and amines was observed without irradiation. The signals of semiquinone radical anions of hypocrellm and the spin-trapping adduct of α-phenyl-N-tertbutyl-ratrone (PNB) with the aminoalkyl radicals have been detected in photoinduced ESR studies. The transient absorption of excited triplet state of HA and semiquinone radical anion of HA have been observed in laser flash photolysis studies. 展开更多
关键词 HYPOCRELLIN (HA and HB) semiquinone radical ANION ALIPHATIC AMINES ESR nanosecond TIME-RESOLVED transient absorption.
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Intrinsic chemiluminescence production from the degradation of haloaromatic pollutants during environmentally-friendly advanced oxidation processes:Mechanism,structure-activity relationship and potential applications 被引量:4
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作者 Benzhan Zhu Chen Shen +3 位作者 Huiying Gao Liya Zhu Jie Shao Li Mao 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2017年第12期68-83,共16页
The ubiquitous distribution of halogenated aromatic compounds(XAr) coupled with their carcinogenicity has raised public concerns on their potential risks to both human health and the ecosystem. Recently, advanced ox... The ubiquitous distribution of halogenated aromatic compounds(XAr) coupled with their carcinogenicity has raised public concerns on their potential risks to both human health and the ecosystem. Recently, advanced oxidation processes(AOPs) have been considered as an"environmentally-friendly" technology for the remediation and destruction of such recalcitrant and highly toxic XAr. During our study on the mechanism of metal-independent production of hydroxyl radicals(UOH) by halogenated quinones and H_2O_2, we found, unexpectedly, that an unprecedented UOH-dependent two-step intrinsic chemiluminescene(CL) can be produced by H_2O_2 and tetrachloro-p-benzoquinone, the major carcinogenic metabolite of the widely used wood preservative pentachlorophenol. Further investigations showed that, in all UOH-generating systems, CL can also be produced not only by pentachlorophenol and all other halogenated phenols, but also by all XAr tested. A systematic structure–activity relationship study for all 19 chlorophenolic congeners showed that the CL increased with an increasing number of Cl-substitution in general. More importantly, a relatively good correlation was observed between the formation of quinoid/semiquinone radical intermediates and CL generation. Based on these results, we propose that UOH-dependent formation of quinoid intermediates and electronically excited carbonyl species is responsible for this unusual CL production; and a rapid, sensitive,simple, and effective CL method was developed not only to detect and quantify trace amount of XAr, but also to provide useful information for predicting the toxicity or monitoring real-time degradation kinetics of XAr. These findings may have broad chemical, environmental and biological implications for future studies on halogenated aromatic persistent organic pollutants. 展开更多
关键词 Halogenated phenols Halogenated quinoid intermediates semiquinone radical Hydroxyl radicals Fenton reaction Chemiluminescene method
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Photo-induced Electron Transfer Between Hypocrellins and BNAH
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作者 安静仪 蒋丽金 《Chinese Science Bulletin》 SCIE EI CAS 1993年第14期1171-1176,共6页
1 Introduction Much research work has been done on the mechanism of photo-induced reduction of quinone dyes by electron donors with visible light. Two ways to obtain the net two-electron reduction product QH^- bave be... 1 Introduction Much research work has been done on the mechanism of photo-induced reduction of quinone dyes by electron donors with visible light. Two ways to obtain the net two-electron reduction product QH^- bave been proposed. One is the direct two-electron transfer (electron-proton-electron transfer) within the complex and the other is the disproportionatioh of the semiquinone radical QH·formed by one-electron transfer. 展开更多
关键词 hypocrellins HYPOCRELLIN semiquinone RADICALS ELECTRON TRANSFER BNAH.
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