Methylene blue sensitized singlet oxygen oxidation of dl-α-tocopherol in dodecylsulfate (SDS) or cetyl trimethyl ammonium brondde (CTAB) ndcelles led to the formation, besidesα-tocopherol quinone and its epoxide, of...Methylene blue sensitized singlet oxygen oxidation of dl-α-tocopherol in dodecylsulfate (SDS) or cetyl trimethyl ammonium brondde (CTAB) ndcelles led to the formation, besidesα-tocopherol quinone and its epoxide, of a hitherto unknown spiro compound 6-hydroxy-2,6,8,9-tetramethyl-2-phytyl- 1-oxaspiro [4, 5] dec -8 - en - 7, 10-dione.展开更多
The CO-NO catalytic reaction on body-centred cubic （bcc） lattice is studied by Monte Carlo simulation. The simple Langmuir-Hinshelwood （LH） mechanism yields a steady reactive window, which is separated by continuo...The CO-NO catalytic reaction on body-centred cubic （bcc） lattice is studied by Monte Carlo simulation. The simple Langmuir-Hinshelwood （LH） mechanism yields a steady reactive window, which is separated by continuous and discontinuous irreversible phase transitions. The effect of precursor mechanism on the phase diagram of the system is also studied. According to this mechanism, the precursor motion of CO molecules is considered only on the surface of bcc lattice. Some interesting observations are reported.展开更多
Kinetic studies of the singlet oxygenation of the title compounds were performed accord- ing to Monroe's method. The reaction rate increases with temperature decreasing, leading to a ne- gative activation enthalpy...Kinetic studies of the singlet oxygenation of the title compounds were performed accord- ing to Monroe's method. The reaction rate increases with temperature decreasing, leading to a ne- gative activation enthalpy and a large negative activation entropy. These data are interpreted as the evidence for the intermediacy of an exciplex. The solvent effect on the reaction rate suggests that the “dioxetane” path involves a transition state or an intermediate with significant zwitterionic character. The electronic effect of the substituent is obvious, with electron-withdrawing substituent retarding the reaction and electron-donating substituent increasing the reaction rate. However, steric bulkiness at the 6-position does not play an important role in the reaction rate.展开更多
Oxidative post-translational modifications of specific chloroplast proteins contribute to the initiation of retrograde signaling.The Arabidopsis thaliana EXECUTER1(EX1)protein,a chloroplast-localized singlet oxygen(^(...Oxidative post-translational modifications of specific chloroplast proteins contribute to the initiation of retrograde signaling.The Arabidopsis thaliana EXECUTER1(EX1)protein,a chloroplast-localized singlet oxygen(^(1)O_(2))sensor,undergoes tryptophan(Trp)643 oxidation by^(1)O_(2),a chloroplast-derived and light-dependent reactive oxygen species.The indole side chain of Trp is vulnerable to^(1)O_(2),leading to the generation of oxidized Trp variants and priming EX1 for degradation by a membrane-bound FtsH protease.The perception of^(1)O_(2)via Trp643 oxidation and subsequent EX1 proteolysis facilitate chloroplast-to-nucleus retrograde signaling.In this study,we discovered that the EX1-like protein EX2 also undergoes^(1)O_(2)-dependent Trp530 oxidation and FtsH-dependent turnover,which attenuates^(1)O_(2)signaling by decelerating EX1-Trp643 oxidation and subsequent EX1 degradation.Consistent with this finding,the loss of EX2 function reinforces EX1-dependent retrograde signaling by accelerating EX1-Trp643 oxidation and subsequent EX1 proteolysis,whereas overexpression of EX2 produces molecular phenotypes opposite to those observed in the loss-of-function mutants of EX2.Intriguingly,phylogenetic analysis suggests that EX2 may have emerged evolutionarily to attenuate the sensitivity of EX1 toward^(1)O_(2).Collectively,these results suggest that EX2 functions as a negative regulator of the EX1 signalosome through its own^(1)O_(2)-dependent oxidation,providing a new mechanistic insight into the regulation of EX1-mediated^(1)O_(2)signaling.展开更多
2-Aryl-3H-indol-3-ones (3a-o) have been synthesized via methanol trapping reaction in singlet oxygenation of 2-arylindoles (1a-o), followed by thermal decomposition of the resultant 2-aryl-2-methoxy-3-oxo-2,3-dihydroi...2-Aryl-3H-indol-3-ones (3a-o) have been synthesized via methanol trapping reaction in singlet oxygenation of 2-arylindoles (1a-o), followed by thermal decomposition of the resultant 2-aryl-2-methoxy-3-oxo-2,3-dihydroindoles (2a-o) in good yields.展开更多
文摘Methylene blue sensitized singlet oxygen oxidation of dl-α-tocopherol in dodecylsulfate (SDS) or cetyl trimethyl ammonium brondde (CTAB) ndcelles led to the formation, besidesα-tocopherol quinone and its epoxide, of a hitherto unknown spiro compound 6-hydroxy-2,6,8,9-tetramethyl-2-phytyl- 1-oxaspiro [4, 5] dec -8 - en - 7, 10-dione.
文摘The CO-NO catalytic reaction on body-centred cubic （bcc） lattice is studied by Monte Carlo simulation. The simple Langmuir-Hinshelwood （LH） mechanism yields a steady reactive window, which is separated by continuous and discontinuous irreversible phase transitions. The effect of precursor mechanism on the phase diagram of the system is also studied. According to this mechanism, the precursor motion of CO molecules is considered only on the surface of bcc lattice. Some interesting observations are reported.
基金This report was partially supported by the National Natural Science Foundation of China
文摘Kinetic studies of the singlet oxygenation of the title compounds were performed accord- ing to Monroe's method. The reaction rate increases with temperature decreasing, leading to a ne- gative activation enthalpy and a large negative activation entropy. These data are interpreted as the evidence for the intermediacy of an exciplex. The solvent effect on the reaction rate suggests that the “dioxetane” path involves a transition state or an intermediate with significant zwitterionic character. The electronic effect of the substituent is obvious, with electron-withdrawing substituent retarding the reaction and electron-donating substituent increasing the reaction rate. However, steric bulkiness at the 6-position does not play an important role in the reaction rate.
基金This research was supported by the Strategic Priority Research Program from the Chinese Academy of Sciences(grant no.XDB27040102)the 100-Talent Program of the Chinese Academy of Sciences and the National Natural Science Foundation of China(NSFC)(grant no.31871397)to C.K.Support from a President's International Fellowship Initiative(PIFI)postdoctoral fellowship from the Chinese Academy of Sciences(no.2019PB0066)to V.D.is also acknowledged.
文摘Oxidative post-translational modifications of specific chloroplast proteins contribute to the initiation of retrograde signaling.The Arabidopsis thaliana EXECUTER1(EX1)protein,a chloroplast-localized singlet oxygen(^(1)O_(2))sensor,undergoes tryptophan(Trp)643 oxidation by^(1)O_(2),a chloroplast-derived and light-dependent reactive oxygen species.The indole side chain of Trp is vulnerable to^(1)O_(2),leading to the generation of oxidized Trp variants and priming EX1 for degradation by a membrane-bound FtsH protease.The perception of^(1)O_(2)via Trp643 oxidation and subsequent EX1 proteolysis facilitate chloroplast-to-nucleus retrograde signaling.In this study,we discovered that the EX1-like protein EX2 also undergoes^(1)O_(2)-dependent Trp530 oxidation and FtsH-dependent turnover,which attenuates^(1)O_(2)signaling by decelerating EX1-Trp643 oxidation and subsequent EX1 degradation.Consistent with this finding,the loss of EX2 function reinforces EX1-dependent retrograde signaling by accelerating EX1-Trp643 oxidation and subsequent EX1 proteolysis,whereas overexpression of EX2 produces molecular phenotypes opposite to those observed in the loss-of-function mutants of EX2.Intriguingly,phylogenetic analysis suggests that EX2 may have emerged evolutionarily to attenuate the sensitivity of EX1 toward^(1)O_(2).Collectively,these results suggest that EX2 functions as a negative regulator of the EX1 signalosome through its own^(1)O_(2)-dependent oxidation,providing a new mechanistic insight into the regulation of EX1-mediated^(1)O_(2)signaling.
基金Project supported by the Coal Industry Universities Science Foundation of China.
文摘2-Aryl-3H-indol-3-ones (3a-o) have been synthesized via methanol trapping reaction in singlet oxygenation of 2-arylindoles (1a-o), followed by thermal decomposition of the resultant 2-aryl-2-methoxy-3-oxo-2,3-dihydroindoles (2a-o) in good yields.
