Glutathione peroxidase, the first example of selenoproteins identified in mammals, was subjected to force field calculations and molecular dynamics in order to enable a clearer comprehension of enzymatic selenium cata...Glutathione peroxidase, the first example of selenoproteins identified in mammals, was subjected to force field calculations and molecular dynamics in order to enable a clearer comprehension of enzymatic selenium catalysis. Starting from the established X-ray structure of bovine GPX, all kinetically defined intermediates and enzyme substrate complexes were modelled. The models thus obtained support the hypothesis that the essential steps of the catalysis are three distinct redox changes of the active site selenium which, in the ground state, presents itself at the surface of selenoperoxidases as the center of a characteristic triad built by selenocysteine, glutarnine and tryptophan. In GPX, four arginine residues and a lysine residue provide an electrostatic architecture which, in each reductive step, directs the donor substrate GSH towards the catalytic center in such a way that 1ts sulfhydryl group must react with the selenium moiety. To this end, different equally efficient modes of substrate binding appear possible. The models are consistent with substrate specificity data, kinetic pattern and other functional characteristics of the enzyme. Comparison of molecular models of GPX with those of other members of the GPX superfamily reveals that the cosubstrate binding mechanisrns are unique for the classical type of cytosolic glutathione peroxidases but cannot operate e. g. in plasma GPX and phospholipid hydroperoxide GPX. The structural differences between the selenoperoxidases, shown to be relevant to their specificities, are discussed in terms of functional diversification within the GPX superfamily展开更多
To improve the contact between platinum catalyst and titanium substrate, a layer of TiO2 nanotube arrays has been synthesized before depositing Pt nanoflowers by pulse electrodeposition. Dramatic improvements in elect...To improve the contact between platinum catalyst and titanium substrate, a layer of TiO2 nanotube arrays has been synthesized before depositing Pt nanoflowers by pulse electrodeposition. Dramatic improvements in electrocatalytic activity （3x） and stability （60x） for methanol oxidation were found, suggesting promising applications in direct methanol fuel cells. The 3x and 60x improvements persist for Pt/Pd catalysts used to overcome the CO poisoning problem.展开更多
There have been many studies on life cycle assessment in sewage treatment,but there are scarce few studies on the treatment of industrial wastewater in combination with advanced oxidation technology,especially in cata...There have been many studies on life cycle assessment in sewage treatment,but there are scarce few studies on the treatment of industrial wastewater in combination with advanced oxidation technology,especially in catalytic wet air oxidation(CWAO).There are no cases of using actual industrialized data onto life cycle assessment.This paper uses Simapro 9.0 software to establish a life cycle assessment model for the treatment of high-concentration organic wastewater by CWAO,and comprehensively explains the impact on the environment from three aspects:the construction phase,the operation phase and the demolition phase.In addition,sensitivity analysis and uncertainty analysis were performed.The results showed that the key factors affecting the environment were marine ecotoxicity,mineral resource consumption and global warming,the operation stage had the greatest impact on the environment,which was related to high power consumption during operation and emissions from the treatment process.Sensitivity analysis showed that electricity consumption has the greatest impact on abiotic depletion and freshwater aquatic ecotoxicity,and it also proved that global warming is mainly caused by pollutant emissions during operation phase.Monte Carlo simulations found slightly higher uncertainty for abiotic depletion and toxicity-related impact categories.展开更多
After analysing the disadvantages of the traditional residue hydrotreating-catalytic cracking combination process, RIPP has proposed a bi-directional combination technology integrating residue hydrotreating with catal...After analysing the disadvantages of the traditional residue hydrotreating-catalytic cracking combination process, RIPP has proposed a bi-directional combination technology integrating residue hydrotreating with catalytic cracking called RICP which does not further recycles the FCC heavy cycle oil (HCO) inside the FCC unit and delivers HCO to the residue hydrotreating unit as a diluting oil for the residue that is concurrently subjected to hydrotreating prior to being used as the FCC feed oil. The RICP technology can stimulate residue hydrotreating reactions through utilization of HCO along with an in- creased yield of FCC light distillate, resulting in enhanced petroleum utilization and economic benefits of the refinery.展开更多
In this study,an efficient catalyst Ag@g-C_(3)N_(4) nanocomposite was successfully synthesized through a simple green reaction,and the characterizations through XRD,FTIR,SEM,BET and XPS were also studied.The activitie...In this study,an efficient catalyst Ag@g-C_(3)N_(4) nanocomposite was successfully synthesized through a simple green reaction,and the characterizations through XRD,FTIR,SEM,BET and XPS were also studied.The activities of Ag@g-C_(3)N_(4) were investigated toward the reduction of 4-nitrophenol to their corresponding aminophenol compounds in the presence of excess NaBH_(4) as a reducing agent.The Ag@g-C_(3)N_(4) nanocomposites exhibited high catalytic activities,in which a 92.2%4-nitrophenol conversion in 10 min and the apparent rate constant K_(app)=264.27×10^(-3) min-1were obtained.The as-prepared Ag@g-C_(3)N_(4) nanocomposites showed great potential in catalytically inducing the reduction of 4-nitrophenol,which makes them economically and energy conservation attractive from industrial waste water treatment.展开更多
P-glycoprotein(ABCB1)is the first discovered mammalian member of the large family of ATP binding cassette(ABC)transporters.It facilitates the movement of compounds(called allocrites)across membranes,using the energy o...P-glycoprotein(ABCB1)is the first discovered mammalian member of the large family of ATP binding cassette(ABC)transporters.It facilitates the movement of compounds(called allocrites)across membranes,using the energy of ATP binding and hydrolysis.Here,we review the thermodynamics of allocrite binding and the kinetics of ATP hydrolysis by ABCB1.In combination with our previous molecular dynamics simulations,these data lead to a new model for allocrite transport by ABCB1.In contrast to previous models,we take into account that the transporter was evolutionarily optimized to operate within a membrane,which dictates the nature of interactions.Hydrophobic interactions drive lipid-water partitioning of allocrites,the transport process’s first step.Weak dipolar interactions(including hydrogen bonding,π-π stacking,and π-cation interactions)drive allocrite recognition,binding,and transport by ABCB1 within the membrane.Increasing the lateral membrane packing density reduces allocrite partitioning but enhances dipolar interactions between allocrites and ABCB1.Allocrite flopping(or reorientation of the polar part towards the extracellular aqueous phase)occurs after hydrolysis of one ATP molecule and opening of ABCB1 at the extracellular side.Rebinding of ATP re-closes the transporter at the extracellular side and expels the potentially remaining allocrite into the membrane.The high sensitivity of the steady-state ATP hydrolysis rate to the nature and number of dipolar interactions,as well as to the dielectric constant of the membrane,points to a flopping process,which occurs to a large extent at the membrane-transporter interface.The proposed unidirectional ABCB1 transport cycle,driven by weak dipolar interactions,is consistent with membrane biophysics.展开更多
The special electronic configuration of phosphorus atoms endows organophosphorus reagents with unique chemical properties,which enable them to be used to catalyze various organic reactions,such as the Wittig reaction,...The special electronic configuration of phosphorus atoms endows organophosphorus reagents with unique chemical properties,which enable them to be used to catalyze various organic reactions,such as the Wittig reaction,Staudinger reaction,Appel reaction and Mitsunobu reaction.However,the catalytic process will be accompanied by the generation of large amounts of phosphine oxide waste,resulting in the reduction of atom utilization of the reaction,and it is difficult to separate the product.Therefore,it is essential to explore a greener and more sustainable organic synthesis route based on the catalytic cycle of phosphine oxide as a model.This paper summarizes the catalytic cycle and recycling of phosphorus with or without reducing agents and reviews the related developments in recent decades:from the addition of stoichiometric strong reducing agents,to the design of ring phosphines with specific structures,to the development of new energy inputs(electrochemistry),to the addition of a series of compounds to activate the P(V)––O double bond,driving the catalytic cycle of phosphine oxide through chemical transformation.This review also points out the development potential of this field in the future,which will promote its development and progress in a greener direction.展开更多
文摘Glutathione peroxidase, the first example of selenoproteins identified in mammals, was subjected to force field calculations and molecular dynamics in order to enable a clearer comprehension of enzymatic selenium catalysis. Starting from the established X-ray structure of bovine GPX, all kinetically defined intermediates and enzyme substrate complexes were modelled. The models thus obtained support the hypothesis that the essential steps of the catalysis are three distinct redox changes of the active site selenium which, in the ground state, presents itself at the surface of selenoperoxidases as the center of a characteristic triad built by selenocysteine, glutarnine and tryptophan. In GPX, four arginine residues and a lysine residue provide an electrostatic architecture which, in each reductive step, directs the donor substrate GSH towards the catalytic center in such a way that 1ts sulfhydryl group must react with the selenium moiety. To this end, different equally efficient modes of substrate binding appear possible. The models are consistent with substrate specificity data, kinetic pattern and other functional characteristics of the enzyme. Comparison of molecular models of GPX with those of other members of the GPX superfamily reveals that the cosubstrate binding mechanisrns are unique for the classical type of cytosolic glutathione peroxidases but cannot operate e. g. in plasma GPX and phospholipid hydroperoxide GPX. The structural differences between the selenoperoxidases, shown to be relevant to their specificities, are discussed in terms of functional diversification within the GPX superfamily
文摘To improve the contact between platinum catalyst and titanium substrate, a layer of TiO2 nanotube arrays has been synthesized before depositing Pt nanoflowers by pulse electrodeposition. Dramatic improvements in electrocatalytic activity （3x） and stability （60x） for methanol oxidation were found, suggesting promising applications in direct methanol fuel cells. The 3x and 60x improvements persist for Pt/Pd catalysts used to overcome the CO poisoning problem.
基金supported by National Natural Science Foundation of China(52100072,52100213)the Fundamental Research FundsfortheCentralUniversities(JZ2021HGTA0159,JZ2021HGQA0212)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA21021101)the Scientific Research Common Program of Beijing Municipal Commission of Education(KM202010017006)the Beijing Natural Science Foundation(8214056)。
文摘There have been many studies on life cycle assessment in sewage treatment,but there are scarce few studies on the treatment of industrial wastewater in combination with advanced oxidation technology,especially in catalytic wet air oxidation(CWAO).There are no cases of using actual industrialized data onto life cycle assessment.This paper uses Simapro 9.0 software to establish a life cycle assessment model for the treatment of high-concentration organic wastewater by CWAO,and comprehensively explains the impact on the environment from three aspects:the construction phase,the operation phase and the demolition phase.In addition,sensitivity analysis and uncertainty analysis were performed.The results showed that the key factors affecting the environment were marine ecotoxicity,mineral resource consumption and global warming,the operation stage had the greatest impact on the environment,which was related to high power consumption during operation and emissions from the treatment process.Sensitivity analysis showed that electricity consumption has the greatest impact on abiotic depletion and freshwater aquatic ecotoxicity,and it also proved that global warming is mainly caused by pollutant emissions during operation phase.Monte Carlo simulations found slightly higher uncertainty for abiotic depletion and toxicity-related impact categories.
文摘After analysing the disadvantages of the traditional residue hydrotreating-catalytic cracking combination process, RIPP has proposed a bi-directional combination technology integrating residue hydrotreating with catalytic cracking called RICP which does not further recycles the FCC heavy cycle oil (HCO) inside the FCC unit and delivers HCO to the residue hydrotreating unit as a diluting oil for the residue that is concurrently subjected to hydrotreating prior to being used as the FCC feed oil. The RICP technology can stimulate residue hydrotreating reactions through utilization of HCO along with an in- creased yield of FCC light distillate, resulting in enhanced petroleum utilization and economic benefits of the refinery.
基金Project supported by the Natural Science Foundation of Fujian Province(No.2019J01747 and 2020J01803)Fujian Provincial Key Laboratory of Featured Materials in Biochemical Industry(FJKLFBCM202104)China NSF(No.41976150)。
文摘In this study,an efficient catalyst Ag@g-C_(3)N_(4) nanocomposite was successfully synthesized through a simple green reaction,and the characterizations through XRD,FTIR,SEM,BET and XPS were also studied.The activities of Ag@g-C_(3)N_(4) were investigated toward the reduction of 4-nitrophenol to their corresponding aminophenol compounds in the presence of excess NaBH_(4) as a reducing agent.The Ag@g-C_(3)N_(4) nanocomposites exhibited high catalytic activities,in which a 92.2%4-nitrophenol conversion in 10 min and the apparent rate constant K_(app)=264.27×10^(-3) min-1were obtained.The as-prepared Ag@g-C_(3)N_(4) nanocomposites showed great potential in catalytically inducing the reduction of 4-nitrophenol,which makes them economically and energy conservation attractive from industrial waste water treatment.
基金Stiftung zur Forderung der biologischen Forschung,Basel,Switzerland.
文摘P-glycoprotein(ABCB1)is the first discovered mammalian member of the large family of ATP binding cassette(ABC)transporters.It facilitates the movement of compounds(called allocrites)across membranes,using the energy of ATP binding and hydrolysis.Here,we review the thermodynamics of allocrite binding and the kinetics of ATP hydrolysis by ABCB1.In combination with our previous molecular dynamics simulations,these data lead to a new model for allocrite transport by ABCB1.In contrast to previous models,we take into account that the transporter was evolutionarily optimized to operate within a membrane,which dictates the nature of interactions.Hydrophobic interactions drive lipid-water partitioning of allocrites,the transport process’s first step.Weak dipolar interactions(including hydrogen bonding,π-π stacking,and π-cation interactions)drive allocrite recognition,binding,and transport by ABCB1 within the membrane.Increasing the lateral membrane packing density reduces allocrite partitioning but enhances dipolar interactions between allocrites and ABCB1.Allocrite flopping(or reorientation of the polar part towards the extracellular aqueous phase)occurs after hydrolysis of one ATP molecule and opening of ABCB1 at the extracellular side.Rebinding of ATP re-closes the transporter at the extracellular side and expels the potentially remaining allocrite into the membrane.The high sensitivity of the steady-state ATP hydrolysis rate to the nature and number of dipolar interactions,as well as to the dielectric constant of the membrane,points to a flopping process,which occurs to a large extent at the membrane-transporter interface.The proposed unidirectional ABCB1 transport cycle,driven by weak dipolar interactions,is consistent with membrane biophysics.
基金support of this work from the National Science Foundation of China(Nos.21602123,21702121 and 21971143)the 111 Project(No.D20015)the Foundation of Hubei Three Gorges Laboratory(No.SC213008).
文摘The special electronic configuration of phosphorus atoms endows organophosphorus reagents with unique chemical properties,which enable them to be used to catalyze various organic reactions,such as the Wittig reaction,Staudinger reaction,Appel reaction and Mitsunobu reaction.However,the catalytic process will be accompanied by the generation of large amounts of phosphine oxide waste,resulting in the reduction of atom utilization of the reaction,and it is difficult to separate the product.Therefore,it is essential to explore a greener and more sustainable organic synthesis route based on the catalytic cycle of phosphine oxide as a model.This paper summarizes the catalytic cycle and recycling of phosphorus with or without reducing agents and reviews the related developments in recent decades:from the addition of stoichiometric strong reducing agents,to the design of ring phosphines with specific structures,to the development of new energy inputs(electrochemistry),to the addition of a series of compounds to activate the P(V)––O double bond,driving the catalytic cycle of phosphine oxide through chemical transformation.This review also points out the development potential of this field in the future,which will promote its development and progress in a greener direction.
