The plasma membrane vesicles were purified from soybean (Glycine max L.) hypocotyls by two_phase partitioning methods. The stimulatory effects of K + on the coupling between ATP hydrolysis and proton transport by th...The plasma membrane vesicles were purified from soybean (Glycine max L.) hypocotyls by two_phase partitioning methods. The stimulatory effects of K + on the coupling between ATP hydrolysis and proton transport by the plasma membrane H +_ATPase were studied. The results showed that the proton transport activity was increased by 850% in the presence of 100 mmol/L KCl, while ATP hydrolytic activity was only increased by 28.2%. Kinetic studies showed that K m of ATP hydrolysis decreased from 1.14 to 0.7 mmol/L, while V max of ATP hydrolysis increased from 285.7 to 344.8 nmol Pi·mg -1 protein·min -1 in the presence of KCl. Experiments showed that the optimum pH was 6.5 and 6.0 in the presence and absence of KCl, respectively. Further studies revealed that K + could promote the inhibitory effects of hydroxylamines and vanadates on the ATP hydrolytic activity. The above results suggested that K + could regulate the coupling between ATP hydrolysis and proton transport of the plasma membrane H +_ATPase through modulating the structure and function of the kinase and phosphatase domains of the plasma membrane H +_ATPase.展开更多
Noble metal cocatalysts have shown great potential in boosting the performance of CdS in photocatalytic water splitting.However,the mechanism and kinetics of electron transfer in noble-metal-decorated CdS during pract...Noble metal cocatalysts have shown great potential in boosting the performance of CdS in photocatalytic water splitting.However,the mechanism and kinetics of electron transfer in noble-metal-decorated CdS during practical hydrogen evolution is not clearly elucidated.Herein,Pt-nanoparticle-decorated CdS nanorods(CdS/Pt)are utilized as the model system to analyze the electron transfer kinetics in CdS/Pt heterojunction.Through femtosecond transient absorption spectroscopy,three dominating exciton quenching pathways are observed and assigned to the trapping of photogenerated electrons at shallow states,recombination of free electrons and trapped holes,and radiative recombination of locally photogenerated electron-hole pairs.The introduction of Pt cocatalyst can release the electrons trapped at the shallow states and construct an ultrafast electron transfer tunnel at the CdS/Pt interface.When CdS/Pt is dispersed in acetonitrile,the lifetime and rate for interfacial electron transfer are respectively calculated to be~5.5 ps and~3.5×10^(10) s^(−1).The CdS/Pt is again dispersed in water to simulate photocatalytic water splitting.The lifetime of the interfacial electron transfer decreases to~5.1 ps and the electron transfer rate increases to~4.9×10^(10) s^(−1),confirming that Pt nanoparticles serve as the main active sites of hydrogen evolution.This work reveals the role of Pt cocatalysts in enhancing the photocatalytic performance of CdS from the perspective of electron transfer kinetics.展开更多
文摘The plasma membrane vesicles were purified from soybean (Glycine max L.) hypocotyls by two_phase partitioning methods. The stimulatory effects of K + on the coupling between ATP hydrolysis and proton transport by the plasma membrane H +_ATPase were studied. The results showed that the proton transport activity was increased by 850% in the presence of 100 mmol/L KCl, while ATP hydrolytic activity was only increased by 28.2%. Kinetic studies showed that K m of ATP hydrolysis decreased from 1.14 to 0.7 mmol/L, while V max of ATP hydrolysis increased from 285.7 to 344.8 nmol Pi·mg -1 protein·min -1 in the presence of KCl. Experiments showed that the optimum pH was 6.5 and 6.0 in the presence and absence of KCl, respectively. Further studies revealed that K + could promote the inhibitory effects of hydroxylamines and vanadates on the ATP hydrolytic activity. The above results suggested that K + could regulate the coupling between ATP hydrolysis and proton transport of the plasma membrane H +_ATPase through modulating the structure and function of the kinase and phosphatase domains of the plasma membrane H +_ATPase.
文摘Noble metal cocatalysts have shown great potential in boosting the performance of CdS in photocatalytic water splitting.However,the mechanism and kinetics of electron transfer in noble-metal-decorated CdS during practical hydrogen evolution is not clearly elucidated.Herein,Pt-nanoparticle-decorated CdS nanorods(CdS/Pt)are utilized as the model system to analyze the electron transfer kinetics in CdS/Pt heterojunction.Through femtosecond transient absorption spectroscopy,three dominating exciton quenching pathways are observed and assigned to the trapping of photogenerated electrons at shallow states,recombination of free electrons and trapped holes,and radiative recombination of locally photogenerated electron-hole pairs.The introduction of Pt cocatalyst can release the electrons trapped at the shallow states and construct an ultrafast electron transfer tunnel at the CdS/Pt interface.When CdS/Pt is dispersed in acetonitrile,the lifetime and rate for interfacial electron transfer are respectively calculated to be~5.5 ps and~3.5×10^(10) s^(−1).The CdS/Pt is again dispersed in water to simulate photocatalytic water splitting.The lifetime of the interfacial electron transfer decreases to~5.1 ps and the electron transfer rate increases to~4.9×10^(10) s^(−1),confirming that Pt nanoparticles serve as the main active sites of hydrogen evolution.This work reveals the role of Pt cocatalysts in enhancing the photocatalytic performance of CdS from the perspective of electron transfer kinetics.
