THE FUNCTIONAL ROLE OF 23 kD AND 24 kD POLYPEPTIDES OF THYLAKOID IN Mg~(2+)-INDUCED CHANGE OF EXCITATION ENERGY DISTRIBUTION BETWEEN TWO PHOTOSYSTEMS IN THE CHLOROPLASTS FROM Codium fragile

In contrast to the chloroplasts from higher plants, Mg~(2+)-induced PS--Ⅱ fluorescence inten-sity increase does not relate to Mg~(2+)-induced surface charge density decrease of thylakoidin the chloroplasts from Codium fragile. Tbe extraction of the green alga chloroplasts withCa~(2+) to remove the 30--31kD polypeptide (Q_B protein) on the thylakoid surface does notaffect the above Mg~(2+)-induced phenomena. If the Ca~(2+)-treated chloroplasts are further di-gested by trypsin to remove the 23kD and 24kD polypeptides on the membrane surface,the Mg~(2+)-induced fluorescence effect will completely disappear whereas the property ofMg~(2+)-induced surface charge density changes remains unchanged. These results not onlyshow that the 23kDa and 24kDa polypeptides on the thylakoid surface are the specific act-ing sites of the cation that induce Chla fluorescence change, but also demonstrate that thecation-induced change of excitation energy distribution between two photosystems is not con-trolled by the electros     

FUNCTIONAL ANALYSIS OF PROTEINS ON THE THYLAKOID MEMBRANE——EFFECTS OF Mg~(2+) AND BSA ON THE TRYPSIN-INDUCED CHLOROPHYLL a FLUORESCENCE AND THYLAKOID MEMBRANE SURFACE CHARGE CHANGES IN SPINACH CHLOROPLASTS

Trypsin digestion of spinach chloroplasts not only inhibits light-induced variable fluorescence yield (△F/F_0) but also abolishes Mg~(2+) stimulating effect on △F/F_0. If chloroplasts are incubated by Mg~(2+) prior to trypsin digestion, Mg~(2+) stimulating ability remains unchanged whereas the enzyme-induced △F/F_0 decline itself is not affected. The protective effect of pretreatment of chloroplasts with Mg~(2+) against trypsin closely correlated with alteration of the net negative charge on the outer surface of the thylakoid membrane by Mg~(2+). In contrast to this, addition of BSA to the chloroplast digested with trypsin significantly recovers the light-induced variable fluorescence yield but it does not influence Mg~(2+)-induced variable fluorescence change. The recovery effect of BSA incubation is not dependent upon Mg~(2+) concentration. Also, BSA does not alter the net negative charge on the outer surface of the thylakoid membrane.These results demonstrate the existence of two independent prote     

THE PIGMENT-PROTEIN COMPLEXES OF HIGHER PLANTS MIGRATION IN THYLAKOID AND THE REGULATION OF LIGHT ENERGY DISTRIBUTION BETWEEN PHOTOSYSTEMS

Appressed and non-appressed lamella membranes of Castor bean leaf chloroplasts were separated by non-ionic detergent Triton-X 100.Appressed membranes showed a high oxygen-evolving activity and low chl a/b ratio. Examining with SDS-PTGE and liquid nitrogen temperature fluorescence measurement showed that they contained only PSII and light-harvesting pigment-protein complexes (LHCP),and there was no detectable amount of PSI. Freeze-fracture electromicroscopic observation confirmed that this part was really an appressed lamella membrane. Through divalent cation Mg~(++), the thylakoid membranes were induced to unstack and restack.With the addition of Mg~(++), the fluorescence intensity was changed instantly. We realized that there existed two processes:One was a rapid process which was accomplished within 30 s. The other was a slow process of which the time duration was about 60 min. This dual effects of Mg~(++) had not been reported before.We had analyzed the change of F685/F730 and discussed the possible     

Mg~(2+)-MEDIATED CHANGES IN FLUIDITY OF PHOSPHOLIPID DECREASE THE SLOW MOTION OF THE INCORPORATED H~+-ATPase IN LIPOSOMES

The effect of Mg~(2+) on the slow motion of H~+-ATPase in proteoliposome was studied. The ST-ESR spectra of H~+-ATPase labeled with maleimide and incorporated in liposomes at various Ma~(2+)concentrations with incubation method were measured. The relationship between the diagnostic param-eters L"/L, C'/C derived from ST-ESR spectra and Mg~(2+) concentrations or temperatures was com-pared with that of the order parameter S derived from 5NS-ESR spectra under the same conditions. Obtain-ed results clearly showed that the increase of Mg~(2+) concentration or the decrease of temperature maycause the increase of the rotational correlation time of H~+-ATPase in proteoliposome. And the rota-tional diffusion rate of H~+-ATPase in membrane lipid is related to the activation energy of the sur-rounding lipid. The change of Mg~(2+) concentration in proteoliposome leads to a change of activarionenergy and influence in turn the slow motion of H~+-ATPase in 1ipid.     

THEORETICAL STUDY OF REACTION DYNAMICS OF H_2 ■ H+H ON LITHIUM(100) SURFACE

A generalized LEPS potential energy surface of (H_2?H +H)/Li(100) plane systemwas constructed based on the ab initio SCF absorption and surface diffusion of a hydrogenatom on lithium(100) surface, and reaction kinetic behaviour of this system was investigatedby means of QCT method. It was shown from analysis of the feature of this potential energysurface that the activation energy of absorption of H_2 molecules on a lithium(100) planeis unnecessary and the dissociation of H_2 on the Li(100) plane relates closely to the adsorp-tion sites and adsorption fashions, and the horizontal manner of dissociation of H_2 is easierthan the standing one. And it was also shown from the analysis of various collision trajec-tories that the surface recombination probabilities of bi-hydrogen atoms at low covering arevery small, and that the surface dissociation probabilities of H_2 are controlled by its vibra-tional quantum number. The potential energy surface of gas-metal surface interaction systemconstructed here is con     

Valence modulated nickel oxynitride network as integrated bifunctional electrodes for enhanced energy storage

As promising electrode materials,transition metal oxides have attracted considerable attention owing to their excellent performance in electrochemical energy storage.However,their poor conductivity and fragile structure limit their practical application.In this study,a binder-free nickel oxide/oxynitride network(NiON WS)bifunctional electrodes with cation multivalent states that exhibit high energy storage performance were synthesized for the first time.The massive active sites,high specific surface areas,and multiple cation valence states of NiON WS were advantageous for electrochemical redox reaction during its application in supercapacitors(1283.5 mF cm^-2)and lithium-ion batteries(1345.0 mA h g^-1).Particularly,the NiON WS based flexible asymmetric SCs exhibit excellent capacitance and energy densities.First-principle calculations were employed to study the mechanism of the electrochemical performance improvement of NiON WS.This study demonstrates the potential of transition metal oxides electrode with high capacity and activity for electrochemical energy storage and conversion.     

THE ELECTRONIC STATE OF Pt ON Pt/L ZEOLITE CATALYST

The effect of the alkali metal cation modification on the aromatization of n-C6 over Pt/ML zeolite catalysts (M=Li. Na. K. Rb) was studied. The results showed that the selectivity for aromati/ation of n-C6 over Pt/MI, increased as the basicity of the alkali cation increased. According to PASCA experiments, dispersed Pt particles were located on the "electron-donation" site of L zeolite XPS measurements further evidenced that a stronger hasicitv of the mouifving canon contributed more electron donation to Pt particles on the surface of 1, zeolite, and shifted the electron binding energy of Pt 4f to lower energies On the other hand, the electron binding energy of Pt 4f in Pt/ML zeolite after reduction was lower than that of Pt0 It is proposed that Pt particles in reduced samples may exist as a Ptδ- state. Moreover, the selectivity for aromatization of aikane was improved since the Ptδ- state was less active to extensive dehvdrogenation of aikane. Ptδ- stale may be presented in the reduced phase of the     

The Energy Transfer Processes between Carotenoid and Chlorophyll Regulated by Electron Exchange Mechanism

Phycobilisomes, carotenoids and chlorophylls are the major pigments for photosynthesis of alga1. But the exact mechanism for the excitation energy transfer between carotenoids and chlorophylls is not clear yet. Compared with the energy transfer process in the phycobilisome to photosystems, the overlap integral of emission spectra of carotenoid with the absorption spectra of the chlorophyll is small and the quantum yield of the carotenoid fluorescence is weak. This fact indicated that the me…     

Ultrafast spectroscopy studies on the mechanism of electron transfer and energy conversion in the isolated pseudo ginseng, water hyacinth and spinach chloroplasts

The spectroscopy characteristics and the fluorescence lifetime for the chloroplasts isolated from the pseudo ginseng, water hyacinth and spinach plant leaves have been studied by absorption spectra, low temperature steady-state fluorescence spectroscopy and single photon counting measurement under the same conditions and by the same methods. The similarity of the absorption spectra for the chloroplasts at room temperature suggests that different plants can efficiently absorb light of the same wavelength. The fluorescence decays in PS II measured at the natural QA state for the chloroplasts have been fitted by a three-exponential kinetic model. The three fluorescence lifetimes are 30, 274 and 805 ps for the pseudo ginseng chloroplast; 138, 521 and 1494 ps for the water hyacinth chloroplast; 197, 465 and 1459 ps for the spinach chloroplast, respectively. The slow lifetime fluorescence component is assigned to a collection of associated light harvesting Chl a/b proteins, the fast lifetime component to the react     

STUDIES ON THE SYMMETRY OF QUATERNARY STRUCTURE OF PHOSPHOENOLPYRUVATE CARBOXYLASE FROM SORGHUM LEAVES

Studies on the symmetry of quaternary structure of PEP carboxylase from sorghum leaves were carried out by means of chemical crosslinking with bifunctional reagents (diimidoesters) and subsequent SDS polyacrylamide gel electrophoresis.Results showed that the four identical subunits of the enzyme are associated isologously: i.e. the quaternary structure of the enzyme has a D_2 symmetry.The patterns of PEP carboxylase crosslinked with suberic dimethylimidate varied in the presence of various ligands.Substrate PEP, Mg~(2+) (required for catalysis of the enzyme), PEP plus Mg~(2+) and the inhibitor malate increased the extent of crosslinking of the enzyme in varying degrees, indicating that binding of these ligands to the enzyme gave rise to changes in the subunit interactions.However,the extent of crosslinking of PEP carboxylase with suberic dimethylimidate decreased greatly in the presence of the activator G6P. Meanwhile, the enzyme remains a tetrameric form either in the absence or in the presence of G6P.     

A rhodamine derivative for Hg2+-selective colorimetric and fluorescent sensing and its application to in vivo imaging

A rhodamine-based sensor has been developed for the detection of mercuric ions. The colorimetric and fluorescence responses, allowing naked-eye detections, are based on Hg~(2+)-induced opening of the rhodamine spirocycle. Among all the testes ions, only Hg~(2+)generated a significant fluorescence enhancement of up to 300-fold, with a bright yellow–green emission. This sensor was a low toxic compound, and was successfully applied in the in vivo imaging of Hg~(2+)in Spill 2 cells and C. elegans. This approach provides a sensitive and accurate method for the estimation of Hg~(2+)in environmental, tobacco and biological applications.     

INVESTIGATION OF THE SURFACE CHARACTERISTICS AND CATALYTIC ACTIVITY OF Sb_xO_y/SiO_2CATALYSTS FOR VAPOR-PHASE SYNTHESIS OF ISOPRENE FROM ISOBUTYLENE AND FORMALDEHYDE

The surface characteristics and catalytic activity of Sb_xO_Y/ SiO_2 catalysts forvapor-phasc synthesis of isoprene from isobutylene and formaldehyde have been investi-gated by TPR, XRD, XPS, IR and catalytic activity evaluation. The results show that whenthe Sb loadings are less than about 5 wt%,Sb_xO_Y is compIctely dispersed on the surface ofsilica to form a surface compound with Sb(V)=O group and the catalysts have relativelyhigh catalytic activity; when the Sb loadings are more than 5 wt%, in addition to this surfacccompound, the crystalline α-Sb_2O_4 is formed on the support surface and causes rapid de-crease of catalytic activity. It is suggcsted that the catalytic activity of Sb_xO_Y /siO_2 catalystsresults from synetgistic catalysis of the surface compound Sb(V)=O as the basic sites andthe surface silanol Si-OH as the acidie sites. The mechanism of this synergistic catalysis forisoprene production is discussed.     

SEPARATION OF IRON AND MANGANESE IN THE EARLY DIAGENETIC PROCESSES AND ITS MECHANISM OF BIOGEOCHEMISTRY

Study shows that the reduction of iron (Fe~(3+)) and manganese (Mn~(4+)) in modern sedi-ments and the diffusive flux of the Mn~(2+) from the pore water into the overlying waterare mainly controlled by bacteria, and the distribution of the bacteria is believed to beaffected strongly by the sedimentary environment. It is the diffusive fluxes between Fe~(2+)and Mn~(2+) that lead to the separation of iron and manganese in the modern sediment at theChangjiang Mouth and near the shore. The level of the separation decreases with theincrease of the overlying water salinity and increases from the surface to the depth. Thismechanism has given a new explanation why manganese is concentrated in sediments onthe oceanic floor of ferromanganese-rich nodules.     

Adsorption and Vibration of CI Atoms on Ni Low-index Surfaces

The 5-parameter Morse potential（5-MP） of the interactions between Cl atoms and Ni surfaces was constructed. The adsorption and diffusion of Cl atoms on Ni low index-surfaces were investigated with 5-MP in detail. All the critical characteristics of the system, such as adsorption site, adsorption geometry, binding energy, eigenvalues for vibration, etc. were obtained. The calculated results show that chlorine atoms are likely to be adsorbed on the high symmetry- sites. Cl atoms locate on the four-fold hollow sites of the intact Ni（100） surface, while they tend to occupy threefold sites on the Ni（ 111 ） surface. The four-fold hollow sites are the most stable adsorption sites on the Ni （110） surface for Cl, although the three-fold sites and the long-bridge sites are stable adsorption sites on the Ni（110） surface for the atoms of the first and second periods. For the Cl-Ni surface adsorption system, the surface binding energy of a Cl atom is relevant to the coarse degree of the cluster surface, and the binding energies have an order of Ni （ 111 ） 〈 Ni（100） 〈Ni（100）.     

Effect Of Transition Metals On Catalytic Performance Of Ru／Sepiolite Catalyst For Methanation Of Carbon Dioxide

The effects of Mo,Mn and Zr transitional metals on the catalytic performance of Ru/sepiolite for CO2 methanation were investigated. The results indicated that addition of the transitional metals affected the activity of the Ru/sepiolite remarkably,and the activities of the catalysts were closely associated with the electronic state of the ruthenium surface,The addition of Mo increased the active surface area,the Ru dispersity,the number of active sites,and the resistance to poisoning.According to the Transition State Theory,when Mo is added into the Ru/sepiolite catalyst,the decrease in surface energy is at a cost of an increment in steric hindrance.When T≤674K,the energy factor was dominating,and resulted in a decreasing in the ratio of S(CH4)/(CO).Otherwise,the steric factor dominated the reaction course.     

Synthesis,UV-curing behavior and surface properties of fluorine-containing vinyl ether polymers

Five fluorine-containing vinyl ether monomers were prepared by the reaction between 2-vinyloxy ethanol, a fluorinated alcohol and hexafluorobenzene in the presence of sodium hydride in dimethylformamide. Two representative properties of these monomers, UV-curing behavior initiated by a cationic photo-initiator PAG 201 and surface free energy of coating films, were investigated. Photo-polymerization proceeded both rapidly and completely with a high double-bond conversion （〉 90%） and a fast curing rate （maximum curing time 〈 21 s） for three monomers. The surface energies of the monomers and the resulting polymer films were then investigated. The minimum surface free energy of the UV-cured homopolymer films reaches 7.1 mJ/m2. X-ray photoelectron spectroscopy data show that the low surthce tension is influenced by fluorine content in the soft segments and fluorinated chains＇ migration to the surface. The five monomers exhibit low viscosity, low surface energy, good thermal stability and good photo-polymerization properties, which make them great candidates for UV coating and photoresist applications.     

PURIFICATION AND KINETICS OF MOUSE LIVER FRUCTOSE 6-PHOSPHATE, 2-KINASE

The mouse liver fructose 6-phosphate, 2-kinase was purified by ultracentrifugation, polyethylene glycol precipitation, and subsequently by chromatography on DEAE-Sephadex, Blue-Sepharose and phasphocellulose columnS. Gel filtration and SDS polyacrylamide electrophorcsis showed that the enzyme has a molecular weight of 110,000 with two identical subunits. Mg~(2+) is essential for its activity. The activation of the enzyme by Mg~(2+) showed a positive cooperativity. The substrate saturation curve for fructose 6-phosphate was sigmoidal and for ATP was hyperbolic. The K_m's for ATP increased with decrease in concentrations of fructose 6-phosphate indicating that the sequence for the substrates binding was in an ordered mechanism with respect to fructose 6-phosphate prior to ATP. An ionizable residue at the active site with pKa 9.5 was essential for the ATP binding and the pKa shifted to 9.8 after the binding of ATP.     

EVOLUTION OF SHORELINES ALONG THE NORTH BANK OF HANGZHOU BAY DURING THE LATE STAGE OF THE HOLOCENE TRANSGRESSION

Based upon the analyses of the sedimentary characteristics, the parallelism of longitudinal streams of the netty drainage system in Shanghai coastal plain to the ancient shorelines, the hydrodynamics in the northern bank of the Hangzhou Bay and the distribution of sites of ancient cultural remains, this paper indicates that during the period of 7000—4000 a B. P., the south spit of the Changjiang River mouth developed southward, and only stretched to the nearshore area of Jinshanwei. The southern end of the spit was a compoundrecurved one. In addition, the evolution of the shoreline west of Jinshanwei during the same period is discussed.     

STUDY ON POLYMER-RARE EARTH METAL ION COMPLEXES Ⅰ. FLUORESCENT PROPERTIES OF POLY(ACRYLIC ACID-CO-4-VINYLPYRIDINE)-RARE EARTH METAL COMPLEXES

A kind of copolymer of acrylic acid and vinylpyridine was synthesized and the fluorescent properties of the complexes of the copolymer with Eu~(3+) or Tb~(3+) were studied. It was found that the fluorescence intensity of the complexes of the eopolymer with Eu~(3+) was 20 times as high as that of the complexes of polyaerylic acid with Eu~(3+) and twice as high as that of the complexes of polyvinylpyridine with Eu~(3+). The effects of the composition of the copolymer and the content of Eu~(3+) or Tb~(3+) in the complexes were studied. The fluorescence lifetime of the complexes was measured and it was found that two or more kinds of energy transfer mechanism existed.     

SURFACE MODIFICATION OF POLYPROPYLENE MICROPOROUS MEMBRANE BY TETHERING POLYPEPTIDES

Two kinds of polypeptides were tethered onto the surface of polypropylene microporous membrane （PPMM） through a ring opening polymerization of L-glutamate N-carboxyanhydride initiated by amino groups which were introduced by ammonia plasma and y-aminopropyl triethanoxysilane treatments. X-ray photoelectron spectroscopy （XPS）, attenuated total reflectance Fourier transform infrared spectroscopy （FT-IR/ATR）, scanning electron microscopy （SEM）, together with water contact angle measurements were used to characterize the modified membranes. XPS analyses and FT-IR/ATR spectra demonstrated that polypeptides are actually grafted onto the membrane surface. The wettability of the membrane surface increases at first and then decreases with the increase in grafting degrees of polypeptide. Platelet adhesion and murine macrophage attachment experiments reveal an enhanced hemocompatibility for the polypeptide modified PPMMs. All these results give evidence that polypeptide grafting can simultaneously improve the hemocompatibility as well as reserve the hydrophobicity for the membrane, which will provide a potential approach to improve the performance of polypropylene hollow fiber microporous membrane used in artificial oxygenator.