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
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
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
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
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
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
In this paper, the photophysical and photosensitive properties of Elsinochrome A (EA), another member of perylenequinone photosensitizers derived via artificially biological synthesis, were stud- ied by taking hypocre...In this paper, the photophysical and photosensitive properties of Elsinochrome A (EA), another member of perylenequinone photosensitizers derived via artificially biological synthesis, were stud- ied by taking hypocrellin A (HA) and hypocrellin B (HB) as the references. It was found that the quantum yield of singlet oxygen produced via the photosensi- tization of EA was 0.98 with HB (0.84) as a reference. Furthermore, the semiquinone anion could be pro- duced via photosensitization of EA in oxygen-free solution. Besides, taking advantage of nanosecond time-resolved spectral technique, the transient triplet absorption spectra and the lifetime of EA in cyclo- hexane were determined by the use of the ground- state depletion method.展开更多
文摘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.
基金Project supported by the National Natural Science Foundation of China
文摘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,
基金This work was supported by the National Natural Science Foundation of China(Grant No.20273079).
文摘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.
基金supported by the Strategic Priority Research Program of CAS(No.XDB01020300)NSF China Grants(Nos.21577149,21477139,21237005 and 21321004)NIH Grants(Nos.ES11497,RR01008 and ES00210)
文摘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.
文摘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.
基金Project supported by the National Natural Science Foundation of China
文摘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.
基金This research was supported by the National Natural Science Foundation of China （Grant No. 20262007 ） the Natural Science Foundation of Yunnan Province （Grant No. 2000C0106M）.
文摘In this paper, the photophysical and photosensitive properties of Elsinochrome A (EA), another member of perylenequinone photosensitizers derived via artificially biological synthesis, were stud- ied by taking hypocrellin A (HA) and hypocrellin B (HB) as the references. It was found that the quantum yield of singlet oxygen produced via the photosensi- tization of EA was 0.98 with HB (0.84) as a reference. Furthermore, the semiquinone anion could be pro- duced via photosensitization of EA in oxygen-free solution. Besides, taking advantage of nanosecond time-resolved spectral technique, the transient triplet absorption spectra and the lifetime of EA in cyclo- hexane were determined by the use of the ground- state depletion method.
