Fluorescence spectra of native purple bacterial reaction center (RC) and bacterial pheophytin (Bphe) replaced RCs were obtained from 600 nm to 900 nm with a selective excitation at 597 nm. With the help of measuring ...Fluorescence spectra of native purple bacterial reaction center (RC) and bacterial pheophytin (Bphe) replaced RCs were obtained from 600 nm to 900 nm with a selective excitation at 597 nm. With the help of measuring the fluorescence from bacterial chlorophyll, bacterial pheophytin and plant pheophytin, the corresponding components in the RCs are classified for fluorescence emission. Results showed that pheophytin substitution influences the composition of fluorescence spectra. Therefore, four, three and two components were obtained from fluorescence spectra of native RC, Bphe B_replaced RC and Bphe A,B _replaced RC, respectively. Fluorescence components are well correlated to the binding of plant pheophytin. The decay of excited state of primary electron donor P in different RCs was also studied by measuring the fluorescence decay at 686.4, 674.1 and 681.1 nm, respectively. The decaying kinetics changed in different RCs, indicating that pheophytin replacement influenced the energy transduction and primary photochemical reaction in purple bacterial reaction centers.展开更多
High energy consumption has seriously hindered the development of Fenton-like reactions for the removal of refractory organic pollutants in water.To solve this problem,we designed a novel Fenton-like catalyst(Cu-PAN3)...High energy consumption has seriously hindered the development of Fenton-like reactions for the removal of refractory organic pollutants in water.To solve this problem,we designed a novel Fenton-like catalyst(Cu-PAN3)by coprecipitation and carbon thermal reduction.The catalyst exhibits excellent Fenton-like catalytic activity and stability for the degradation of various pollutants with low H_(2)O_(2)consumption.The experimental results indicate that the dual reaction centers(DRCs)are composed of Cu-N-C and Cu-O-C bridges between copper and graphene-like carbon,which form electron-poor/rich centers on the catalyst surface.H_(2)O_(2)is mainly reduced at electron-rich Cu centers to free radicals for pollutant degradation.Meanwhile,pollutants can be oxidized by donating electrons to the electron-poor C centers of the catalyst,which inhibits the ineffective decomposition of H_(2)O_(2)at the electron-poor centers.This therefore significantly reduces the consumption of H_(2)O_(2)and reduces energy consumption.展开更多
Early events of charge separation in reaction centers (RCs) of bacterial photosynthesis are modeled by kinetic equations with time-dependent rate constants. An illustrative case of regular motion along a “slow” coor...Early events of charge separation in reaction centers (RCs) of bacterial photosynthesis are modeled by kinetic equations with time-dependent rate constants. An illustrative case of regular motion along a “slow” coordinates leading to oscillations in the kinetics is examined. Different schemes of charge separation are investigated. A good fitting of experimental kinetics of native Rba. sphaeroides RCs is achieved in the five states model P*1BAHA↔P*2BAHA↔I↔P+HA↔P+BA with two excited states BAHA and BAHA and three charge separated states I, P+HA and P+BA (P is a primary electron donor, bacteriochlorophyll dimer, BA and HA are an electron acceptor, monomeric bacteriochlorophyll and bacteriopheophytin in active A-branch, respectively). In the model only the first excited state is directly populated by optical excitation. The emission of the two excited states is assumed to be at 905 and 940 nm, respectively. The intermediate state I is assumed to absorb at 1020 nm as well as the P+HA state. The model explains the deep oscillations in the kinetics of the stimulated emission and of the absorption. In the simpler schemes without the I state or with only one excited state the accordance with the experiment is achieved at unreal parameter values. A possible nature of the I and BAHA states and a possible incoherent nature of the oscillations are discussed.展开更多
The electronic structure of protein chains L and M in photosynthetic reaction center (PRC) of Rhodobacter sphaeroides (Van Niel) Imhoff, Truper et Pfennig) was studied by using the Overlapping Dimer Approximation meth...The electronic structure of protein chains L and M in photosynthetic reaction center (PRC) of Rhodobacter sphaeroides (Van Niel) Imhoff, Truper et Pfennig) was studied by using the Overlapping Dimer Approximation method and the Extended Negative Factor Counter method at ab initio level. The result indicated that: (1) Amino acid residues, the molecular orbitals of which composed the main components of frontier orbitals of protein chain L (M), are located at the random coil areas of chain L (alpha helix areas of chain M). Since the random coil is flexible and more easy to change its conformation in the electron transfer process and to reduce the energy of the system, and the structure of the alpha helix is reletively stable, this difference might be one of the causes for the electron transfer in photosynthetic reaction center (PRC) only takes place along the L branch. (2) The His residues which axially coordinated to the 'special pair' P and accessory chlorophyll molecules (ABChls) are essentially important for the E-LUMO levels of P and ABChl. But, the corresponding molecular orbitals of these His residues do not appear in the composition of frontier orbitals of protein chains. It means that the interaction between pigment molecules and protein chains do not influence the contribution to the frontier orbitals of protein chains explicitly, but influences the corresponding E-LUMO levels significantly.展开更多
Photosystem I(PSI)is a large protein supercomplex that catalyzes the light-dependent oxidation of plastocyanin(or cytochrome c6)and the reduction of ferredoxin.This catalytic reaction is realized by a transmembrane el...Photosystem I(PSI)is a large protein supercomplex that catalyzes the light-dependent oxidation of plastocyanin(or cytochrome c6)and the reduction of ferredoxin.This catalytic reaction is realized by a transmembrane electron transfer chain consisting of primary electron donor(a special chlorophyll(Chl)pair)and electron acceptors A_(0),A_(1),and three Fe_(4)S_(4) clusters,F_(X),F_(A),and F_(B).Here we report the PSI structure from a Chl d-dominated cyanobacterium Acaryochloris marina at 3.3Åresolution obtained by single-particle cryo-electron microscopy.The A.marina PSI exists as a trimer with three identical monomers.Surprisingly,the structure reveals a unique composition of electron transfer chain in which the primary electron acceptor A_(0) is composed of two pheophytin a rather than Chl a found in any other well-known PSI structures.A novel subunit Psa27 is observed in the A.marina PSI structure.In addition,77 Chls,13α-carotenes,two phylloquinones,three Fe-S clusters,two phosphatidyl glycerols,and one monogalactosyl-diglyceride were identified in each PSI monomer.Our results provide a structural basis for deciphering the mechanism of photosynthesis in a PSI complex with Chl d as the dominating pigments and absorbing far-red light.展开更多
The photosynthetic reaction center complex(RCC)of green sulfur bacteria(GSB)consists of the membrane-imbedded RC core and the peripheric energy transmitting proteins called Fenna–Matthews–Olson(FMO).Functionally,FMO...The photosynthetic reaction center complex(RCC)of green sulfur bacteria(GSB)consists of the membrane-imbedded RC core and the peripheric energy transmitting proteins called Fenna–Matthews–Olson(FMO).Functionally,FMO transfers the absorbed energy from a huge peripheral light-harvesting antenna named chlorosome to the RC core where charge separation occurs.In vivo,one RC was found to bind two FMOs,however,the intact structure of RCC as well as the energy transfer mechanism within RCC remain to be clarified.Here we report a structure of intact RCC which contains a RC core and two FMO trimers from a thermophilic green sulfur bacterium Chlorobaculum tepidum at 2.9A resolution by cryo-electron microscopy.The second FMO trimer is attached at the cytoplasmic side asymmetrically relative to the first FMO trimer reported previously.We also observed two new subunits(PscE and PscF)and the N-terminal transmembrane domain of a cytochrome-containing subunit(PscC)in the structure.These two novel subunits possibly function to facilitate the binding of FMOs to RC core and to stabilize the whole complex.A new bacteriochlorophyll(numbered as 816)was identified at the interspace between PscF and PscA-1,causing an asymmetrical energy transfer from the two FMO trimers to RC core.Based on the structure,we propose an energy transfer network within this photosynthetic apparatus.展开更多
Excessive consumption of energy and resources is a major challenge in wastewater treatment.Here,a novel heterogeneous Fenton-like catalyst consisting of Cu-doped graphenelike catalysts (Cu-GCD NSs) was first synthesiz...Excessive consumption of energy and resources is a major challenge in wastewater treatment.Here,a novel heterogeneous Fenton-like catalyst consisting of Cu-doped graphenelike catalysts (Cu-GCD NSs) was first synthesized by an enhanced carbothermal reduction of β-cyclodextrin (β-CD).The catalyst exhibits excellent Fenton-like catalytic activity for the degradation of various pollutants under neutral conditions,accompanied by low H_(2)O_(2)consumption.The results of structural characterization and theoretical calculations confirmed that the dual reaction centers (DRCs) were constructed on Cu-GCD NSs surface through C-O-Cu bonds supported on zero-valent copper species,which play a significant role in the high-performance Fenton-like reaction.The pollutants that served as electron donors were decomposed in the electron-poor carbon centers,whereas H_(2)O_(2)and dissolved oxygen obtained these electrons in the electron-rich Cu centers through C-O-Cu bonds,thereby producing more active species.This study demonstrates that the electrons of pollutants can be efficiently utilized in Fenton-like reactions by DRCs on the catalyst surface,which provides an effective strategy to improve Fenton-like reactivity and reduce H_(2)O_(2)consumption.展开更多
An Isolated photosystem （PS） II reaction center （RC） with altered pigment content was obtained by chemical exchange of native chlorophyll a （Chl） with externally added Cu-Chl a （Cu-Chl）. Pigment composition an...An Isolated photosystem （PS） II reaction center （RC） with altered pigment content was obtained by chemical exchange of native chlorophyll a （Chl） with externally added Cu-Chl a （Cu-Chl）. Pigment composition and spectroscopic properties of the RC exchanged with Cu-Chl were compared with native RC and RC treated with Chl In the same way. High-performance liquid chromatography analysis showed approximately 0.5 Cu-Chl per two pheophytln in the Cu-Chl-reconstltuted RC preparation. Insertion of Cu-Chl resulted in a decrease In absorption at 670 nm and an Increase at 660 nm, suggesting that the peripheral Chl may have been displaced. Fluorescence emission spectra of the Cu-Chl-reconstituted RC displayed a marked decrease In fluorescence yield and a blue shift of the band maximum, accompanied by the appearance of a broad peak at a shorter wavelength, Indicating that energy transfer In the modified RC was disturbed by Cu-Chl, a quencher of the excited state. However, there were few differences in the circular dichrolsm （CD） spectra, suggesting that the arrangement of pigments and proteins responsible for the CD signal was not significantly affected. In addition, no obvious change In peptlde components was found after the exchange procedure.展开更多
1 Results The photosynthetic bacterial reaction center (RC) is a membrane protein complex.The RC is composed of three protein subunits and redox components such as bacteriochlorophylls, bacteriopheophytins,and quinone...1 Results The photosynthetic bacterial reaction center (RC) is a membrane protein complex.The RC is composed of three protein subunits and redox components such as bacteriochlorophylls, bacteriopheophytins,and quinones.The RC performs the photochemical electron transfer from the bacteriochlorophyll dimer through a series of electron donor and acceptor molecules to a secondary quinone,QB.QB accepts electrons from a primary quinone,QA,in two sequential electron transfer reactions.The second electron trans...展开更多
Deg5,deg8 and the double mutant,deg5deg8 of Arabidopsis thaliana were used to study the physiological role of the DEG proteases in the repair cycle of photosystem II (PSII) under heat stress. PSII activity in deg muta...Deg5,deg8 and the double mutant,deg5deg8 of Arabidopsis thaliana were used to study the physiological role of the DEG proteases in the repair cycle of photosystem II (PSII) under heat stress. PSII activity in deg mutants showed increased sensitivity to heat stress, and the extent of this effect was greater in the double mutant, deg5deg8, than in the single mutants, deg5 and deg8. Degradation of the D1 protein was slower in the mutants than in the WT plants. Furthermore, the levels of other PSII reaction center proteins tested remained relatively stable in the mutant and WT plants following high-temperature treatment. Thus, our results indicate that DEG5 and DEG8 may have synergistic function in degradation of D1 protein under heat stress.展开更多
IN recent years,magnetic circular dichroism(MCD)demonstrated its unique advantages inanalysis of metal porphyrin and its interaction with protein.However,there were few re-ports about the application of MCD method in ...IN recent years,magnetic circular dichroism(MCD)demonstrated its unique advantages inanalysis of metal porphyrin and its interaction with protein.However,there were few re-ports about the application of MCD method in photosynthesis field.It is known that most pig-ments in PS Ⅱ-RC are metal porphyrin type.This note reports the MCD spectrum of PS Ⅱ-展开更多
In the presence of acetone and an excess of exogenous plant pheophytins, bacterio-pheophytins in the reaction centers from Rhodobacter sphaeroides RS601 were replaced by pheophytins at sites HA and HB, when incubated ...In the presence of acetone and an excess of exogenous plant pheophytins, bacterio-pheophytins in the reaction centers from Rhodobacter sphaeroides RS601 were replaced by pheophytins at sites HA and HB, when incubated at 43.5℃ for more than 15 min. The substitution of bacteriopheophytins in the reaction centers was 50% and 71% with incubation of 15 and 60 min, respectively. In the absorption spectra of pheophytin-replaced reaction centers (Phe RCs), bands assigned to the transition moments Qx (537 nm) and QY (758 nm) of bacteriopheophytin disappeared, and three distinct bands assigned to the transition moments Qx (509/542 nm) and QY (674 nm) of pheophytin appeared instead. Compared to that of the control reaction centers, the photochemical activities of Phe RCs are 78% and 71% of control, with the incubation time of 15 and 60 min. Differences might exist between the redox properties of Phe RC and of native reaction centers, but the substitution is significant, and the new system is available for further studies.展开更多
Based on the QM/MM optimized X-ray crystal structure of the photosynthetic reaction center (PRC) of purple bacteria Rhodopseudomonas (Rps.) viridis, quantum chemistry density functional method (DFT, B3LYP/6-31G) has b...Based on the QM/MM optimized X-ray crystal structure of the photosynthetic reaction center (PRC) of purple bacteria Rhodopseudomonas (Rps.) viridis, quantum chemistry density functional method (DFT, B3LYP/6-31G) has been performed to study the interactions between the pigment molecules and either the surrounded amino acid residues or water molecules that are either axially coordinated or hydrogen bonded with the pigment molecules, leading to an explanation of the mechanism of the primary electron-transfer (ET) reactions in the PRC. Results show that the axial coordination of amino acid residues greatly raises the ELUMO of pigment molecules and it is important for the possibility of ET to take place. Different hydrogen bonds between amino acid residues, water molecules and pigment molecules decrease the ELUMO of the pigment molecules to different extents. It is crucial for the ET taking place from excited P along L branch and sustains that the ET is a one-step reaction without through accessory bacteriochlorophyll (ABChl b). It is insufficient to treat the whole protein surrounding as a homogeneous dielectric medium.展开更多
Ammopiptanthus mongolicus (Maxim.) Cheng f. is one of the evergreen shrubs in the desert region of China. In midday its leaves bear photon flux density over 1 500 μmol·m -2 ·s -1 at natural habit...Ammopiptanthus mongolicus (Maxim.) Cheng f. is one of the evergreen shrubs in the desert region of China. In midday its leaves bear photon flux density over 1 500 μmol·m -2 ·s -1 at natural habitat. They show the obvious phenomenon of photoinhibition. For the study of the effects of drought stress on the major protective mechanism against strong light in A. mongolicus leaves, the diurnal variations of photosynthetic rate and chlorophyll fluorescence parameters were investigated under natural conditions with portable photosynthetic measurement system (CIRAS_1) and portable fluorometer (MFMS_2). The experimental results showed that, under normal and drought stress conditions,the net photosynthetic rate ( Pn ), the primary maximum photochemical efficiency of PSⅡ ( Fv/Fm ) and the quantum efficiency of noncyclic electron transport of PSⅡ ( Φ PSⅡ ) decreased obviously at noon (Figs.2,3A,4B). In comparison with plants under normal condition, under drought stress minimal chlorophyll fluorescence ( Fo ) decreased at first and then increased (Fig.3A), non_photochemical quenching ( NPQ ) quickly increased and sustained at a higher level (Fig.4B). This indicated that the major photoprotective mechanism of A. mongolicus leaves was the xanthophyll cycle_dependent thermal energy dissipation under normal condition, while under drought stress, the major photoprotective mechanism was both the xanthophyll cycle_dependent thermal energy dissipation and the reversible inactivation of PSⅡ reaction center.展开更多
基金The State Key Basic Research and Development Plan(G1998010100)the National Natural Science Foundation of China(39870161).
文摘Fluorescence spectra of native purple bacterial reaction center (RC) and bacterial pheophytin (Bphe) replaced RCs were obtained from 600 nm to 900 nm with a selective excitation at 597 nm. With the help of measuring the fluorescence from bacterial chlorophyll, bacterial pheophytin and plant pheophytin, the corresponding components in the RCs are classified for fluorescence emission. Results showed that pheophytin substitution influences the composition of fluorescence spectra. Therefore, four, three and two components were obtained from fluorescence spectra of native RC, Bphe B_replaced RC and Bphe A,B _replaced RC, respectively. Fluorescence components are well correlated to the binding of plant pheophytin. The decay of excited state of primary electron donor P in different RCs was also studied by measuring the fluorescence decay at 686.4, 674.1 and 681.1 nm, respectively. The decaying kinetics changed in different RCs, indicating that pheophytin replacement influenced the energy transduction and primary photochemical reaction in purple bacterial reaction centers.
基金supported by the National Natural Science Foundation of China(Nos.52150056,51838005,and 52100032)the Introduced Innovative R&D Team Project under the“Pearl River Talent Recruitment Program”of Guangdong Province(No.2019ZT08L387)+1 种基金the Special Basic Research Fund for Central Public Research Institutes of China(No.PMzx703-202204-152)the support from the BL14W1 beamline of Shanghai Synchrotron Radiation Facility(SSRF,China)。
文摘High energy consumption has seriously hindered the development of Fenton-like reactions for the removal of refractory organic pollutants in water.To solve this problem,we designed a novel Fenton-like catalyst(Cu-PAN3)by coprecipitation and carbon thermal reduction.The catalyst exhibits excellent Fenton-like catalytic activity and stability for the degradation of various pollutants with low H_(2)O_(2)consumption.The experimental results indicate that the dual reaction centers(DRCs)are composed of Cu-N-C and Cu-O-C bridges between copper and graphene-like carbon,which form electron-poor/rich centers on the catalyst surface.H_(2)O_(2)is mainly reduced at electron-rich Cu centers to free radicals for pollutant degradation.Meanwhile,pollutants can be oxidized by donating electrons to the electron-poor C centers of the catalyst,which inhibits the ineffective decomposition of H_(2)O_(2)at the electron-poor centers.This therefore significantly reduces the consumption of H_(2)O_(2)and reduces energy consumption.
文摘Early events of charge separation in reaction centers (RCs) of bacterial photosynthesis are modeled by kinetic equations with time-dependent rate constants. An illustrative case of regular motion along a “slow” coordinates leading to oscillations in the kinetics is examined. Different schemes of charge separation are investigated. A good fitting of experimental kinetics of native Rba. sphaeroides RCs is achieved in the five states model P*1BAHA↔P*2BAHA↔I↔P+HA↔P+BA with two excited states BAHA and BAHA and three charge separated states I, P+HA and P+BA (P is a primary electron donor, bacteriochlorophyll dimer, BA and HA are an electron acceptor, monomeric bacteriochlorophyll and bacteriopheophytin in active A-branch, respectively). In the model only the first excited state is directly populated by optical excitation. The emission of the two excited states is assumed to be at 905 and 940 nm, respectively. The intermediate state I is assumed to absorb at 1020 nm as well as the P+HA state. The model explains the deep oscillations in the kinetics of the stimulated emission and of the absorption. In the simpler schemes without the I state or with only one excited state the accordance with the experiment is achieved at unreal parameter values. A possible nature of the I and BAHA states and a possible incoherent nature of the oscillations are discussed.
文摘The electronic structure of protein chains L and M in photosynthetic reaction center (PRC) of Rhodobacter sphaeroides (Van Niel) Imhoff, Truper et Pfennig) was studied by using the Overlapping Dimer Approximation method and the Extended Negative Factor Counter method at ab initio level. The result indicated that: (1) Amino acid residues, the molecular orbitals of which composed the main components of frontier orbitals of protein chain L (M), are located at the random coil areas of chain L (alpha helix areas of chain M). Since the random coil is flexible and more easy to change its conformation in the electron transfer process and to reduce the energy of the system, and the structure of the alpha helix is reletively stable, this difference might be one of the causes for the electron transfer in photosynthetic reaction center (PRC) only takes place along the L branch. (2) The His residues which axially coordinated to the 'special pair' P and accessory chlorophyll molecules (ABChls) are essentially important for the E-LUMO levels of P and ABChl. But, the corresponding molecular orbitals of these His residues do not appear in the composition of frontier orbitals of protein chains. It means that the interaction between pigment molecules and protein chains do not influence the contribution to the frontier orbitals of protein chains explicitly, but influences the corresponding E-LUMO levels significantly.
基金The project was funded by the National Key R&D Program of China(2020YFA0907600,2017YFA0503700,2017YFA0504803,2018YFA0507700,2019YFA0906300)the Strategic Priority Research Program of CAS(XDA27050402,XDB17000000)+2 种基金the Chinese Academy of Sciences Key Research Program of Frontier Sciences(QYZDY-SSW-SMC003)Youth Innovation Promotion Association of CAS(2020081),CAS Interdisciplinary Innovation Team(JCTD-2020-06)the Fundamental Research Funds for the Central Universities(2018XZZX001-13).
文摘Photosystem I(PSI)is a large protein supercomplex that catalyzes the light-dependent oxidation of plastocyanin(or cytochrome c6)and the reduction of ferredoxin.This catalytic reaction is realized by a transmembrane electron transfer chain consisting of primary electron donor(a special chlorophyll(Chl)pair)and electron acceptors A_(0),A_(1),and three Fe_(4)S_(4) clusters,F_(X),F_(A),and F_(B).Here we report the PSI structure from a Chl d-dominated cyanobacterium Acaryochloris marina at 3.3Åresolution obtained by single-particle cryo-electron microscopy.The A.marina PSI exists as a trimer with three identical monomers.Surprisingly,the structure reveals a unique composition of electron transfer chain in which the primary electron acceptor A_(0) is composed of two pheophytin a rather than Chl a found in any other well-known PSI structures.A novel subunit Psa27 is observed in the A.marina PSI structure.In addition,77 Chls,13α-carotenes,two phylloquinones,three Fe-S clusters,two phosphatidyl glycerols,and one monogalactosyl-diglyceride were identified in each PSI monomer.Our results provide a structural basis for deciphering the mechanism of photosynthesis in a PSI complex with Chl d as the dominating pigments and absorbing far-red light.
基金supported by a National Natural Science Foundation of China (32100202 to J.H.C.)Natural Science Foundation of Zhejiang Province,China (LR22C010001 to J.H.C.)+1 种基金the National Key Research and Development Program of China (2018YFA0507700,2017YFA0504803 to X.Z.)the Fundamental Research Funds for the Central Universities (2018XZZX001-13 to X.Z.)。
文摘The photosynthetic reaction center complex(RCC)of green sulfur bacteria(GSB)consists of the membrane-imbedded RC core and the peripheric energy transmitting proteins called Fenna–Matthews–Olson(FMO).Functionally,FMO transfers the absorbed energy from a huge peripheral light-harvesting antenna named chlorosome to the RC core where charge separation occurs.In vivo,one RC was found to bind two FMOs,however,the intact structure of RCC as well as the energy transfer mechanism within RCC remain to be clarified.Here we report a structure of intact RCC which contains a RC core and two FMO trimers from a thermophilic green sulfur bacterium Chlorobaculum tepidum at 2.9A resolution by cryo-electron microscopy.The second FMO trimer is attached at the cytoplasmic side asymmetrically relative to the first FMO trimer reported previously.We also observed two new subunits(PscE and PscF)and the N-terminal transmembrane domain of a cytochrome-containing subunit(PscC)in the structure.These two novel subunits possibly function to facilitate the binding of FMOs to RC core and to stabilize the whole complex.A new bacteriochlorophyll(numbered as 816)was identified at the interspace between PscF and PscA-1,causing an asymmetrical energy transfer from the two FMO trimers to RC core.Based on the structure,we propose an energy transfer network within this photosynthetic apparatus.
基金financially supported by the National Natural Science Foundation of China (Nos.52070046,51808140,51838005 and 21906034)the Introduced Innovative R&D Team Project under the"Pearl River Talent Recruitment Program"of Guangdong Province (No.2019ZT08L387)the BL14W1 beamline of Shanghai Synchrotron Radiation Facility (SSRF,China)。
文摘Excessive consumption of energy and resources is a major challenge in wastewater treatment.Here,a novel heterogeneous Fenton-like catalyst consisting of Cu-doped graphenelike catalysts (Cu-GCD NSs) was first synthesized by an enhanced carbothermal reduction of β-cyclodextrin (β-CD).The catalyst exhibits excellent Fenton-like catalytic activity for the degradation of various pollutants under neutral conditions,accompanied by low H_(2)O_(2)consumption.The results of structural characterization and theoretical calculations confirmed that the dual reaction centers (DRCs) were constructed on Cu-GCD NSs surface through C-O-Cu bonds supported on zero-valent copper species,which play a significant role in the high-performance Fenton-like reaction.The pollutants that served as electron donors were decomposed in the electron-poor carbon centers,whereas H_(2)O_(2)and dissolved oxygen obtained these electrons in the electron-rich Cu centers through C-O-Cu bonds,thereby producing more active species.This study demonstrates that the electrons of pollutants can be efficiently utilized in Fenton-like reactions by DRCs on the catalyst surface,which provides an effective strategy to improve Fenton-like reactivity and reduce H_(2)O_(2)consumption.
文摘An Isolated photosystem （PS） II reaction center （RC） with altered pigment content was obtained by chemical exchange of native chlorophyll a （Chl） with externally added Cu-Chl a （Cu-Chl）. Pigment composition and spectroscopic properties of the RC exchanged with Cu-Chl were compared with native RC and RC treated with Chl In the same way. High-performance liquid chromatography analysis showed approximately 0.5 Cu-Chl per two pheophytln in the Cu-Chl-reconstltuted RC preparation. Insertion of Cu-Chl resulted in a decrease In absorption at 670 nm and an Increase at 660 nm, suggesting that the peripheral Chl may have been displaced. Fluorescence emission spectra of the Cu-Chl-reconstituted RC displayed a marked decrease In fluorescence yield and a blue shift of the band maximum, accompanied by the appearance of a broad peak at a shorter wavelength, Indicating that energy transfer In the modified RC was disturbed by Cu-Chl, a quencher of the excited state. However, there were few differences in the circular dichrolsm （CD） spectra, suggesting that the arrangement of pigments and proteins responsible for the CD signal was not significantly affected. In addition, no obvious change In peptlde components was found after the exchange procedure.
文摘1 Results The photosynthetic bacterial reaction center (RC) is a membrane protein complex.The RC is composed of three protein subunits and redox components such as bacteriochlorophylls, bacteriopheophytins,and quinones.The RC performs the photochemical electron transfer from the bacteriochlorophyll dimer through a series of electron donor and acceptor molecules to a secondary quinone,QB.QB accepts electrons from a primary quinone,QA,in two sequential electron transfer reactions.The second electron trans...
基金the Frontier Project of the Knowledge Innovation Program of the Chinese Academy of Science (Grant No. KJCX2-SW-w29)
文摘Deg5,deg8 and the double mutant,deg5deg8 of Arabidopsis thaliana were used to study the physiological role of the DEG proteases in the repair cycle of photosystem II (PSII) under heat stress. PSII activity in deg mutants showed increased sensitivity to heat stress, and the extent of this effect was greater in the double mutant, deg5deg8, than in the single mutants, deg5 and deg8. Degradation of the D1 protein was slower in the mutants than in the WT plants. Furthermore, the levels of other PSII reaction center proteins tested remained relatively stable in the mutant and WT plants following high-temperature treatment. Thus, our results indicate that DEG5 and DEG8 may have synergistic function in degradation of D1 protein under heat stress.
文摘IN recent years,magnetic circular dichroism(MCD)demonstrated its unique advantages inanalysis of metal porphyrin and its interaction with protein.However,there were few re-ports about the application of MCD method in photosynthesis field.It is known that most pig-ments in PS Ⅱ-RC are metal porphyrin type.This note reports the MCD spectrum of PS Ⅱ-
文摘In the presence of acetone and an excess of exogenous plant pheophytins, bacterio-pheophytins in the reaction centers from Rhodobacter sphaeroides RS601 were replaced by pheophytins at sites HA and HB, when incubated at 43.5℃ for more than 15 min. The substitution of bacteriopheophytins in the reaction centers was 50% and 71% with incubation of 15 and 60 min, respectively. In the absorption spectra of pheophytin-replaced reaction centers (Phe RCs), bands assigned to the transition moments Qx (537 nm) and QY (758 nm) of bacteriopheophytin disappeared, and three distinct bands assigned to the transition moments Qx (509/542 nm) and QY (674 nm) of pheophytin appeared instead. Compared to that of the control reaction centers, the photochemical activities of Phe RCs are 78% and 71% of control, with the incubation time of 15 and 60 min. Differences might exist between the redox properties of Phe RC and of native reaction centers, but the substitution is significant, and the new system is available for further studies.
基金This work was supported by the National Natural Science Foundation of China(Grant No.39890390) theState Key Basic Research Development Plan(Grant No.G1998010100).
文摘Based on the QM/MM optimized X-ray crystal structure of the photosynthetic reaction center (PRC) of purple bacteria Rhodopseudomonas (Rps.) viridis, quantum chemistry density functional method (DFT, B3LYP/6-31G) has been performed to study the interactions between the pigment molecules and either the surrounded amino acid residues or water molecules that are either axially coordinated or hydrogen bonded with the pigment molecules, leading to an explanation of the mechanism of the primary electron-transfer (ET) reactions in the PRC. Results show that the axial coordination of amino acid residues greatly raises the ELUMO of pigment molecules and it is important for the possibility of ET to take place. Different hydrogen bonds between amino acid residues, water molecules and pigment molecules decrease the ELUMO of the pigment molecules to different extents. It is crucial for the ET taking place from excited P along L branch and sustains that the ET is a one-step reaction without through accessory bacteriochlorophyll (ABChl b). It is insufficient to treat the whole protein surrounding as a homogeneous dielectric medium.
文摘Ammopiptanthus mongolicus (Maxim.) Cheng f. is one of the evergreen shrubs in the desert region of China. In midday its leaves bear photon flux density over 1 500 μmol·m -2 ·s -1 at natural habitat. They show the obvious phenomenon of photoinhibition. For the study of the effects of drought stress on the major protective mechanism against strong light in A. mongolicus leaves, the diurnal variations of photosynthetic rate and chlorophyll fluorescence parameters were investigated under natural conditions with portable photosynthetic measurement system (CIRAS_1) and portable fluorometer (MFMS_2). The experimental results showed that, under normal and drought stress conditions,the net photosynthetic rate ( Pn ), the primary maximum photochemical efficiency of PSⅡ ( Fv/Fm ) and the quantum efficiency of noncyclic electron transport of PSⅡ ( Φ PSⅡ ) decreased obviously at noon (Figs.2,3A,4B). In comparison with plants under normal condition, under drought stress minimal chlorophyll fluorescence ( Fo ) decreased at first and then increased (Fig.3A), non_photochemical quenching ( NPQ ) quickly increased and sustained at a higher level (Fig.4B). This indicated that the major photoprotective mechanism of A. mongolicus leaves was the xanthophyll cycle_dependent thermal energy dissipation under normal condition, while under drought stress, the major photoprotective mechanism was both the xanthophyll cycle_dependent thermal energy dissipation and the reversible inactivation of PSⅡ reaction center.
