ISSN:0005-9021    

DOI:10.1002/bbpc.19840880702

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880703

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880705

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractThe kinetics of proton transport coupled ATP synthesis at the chloroplast membrane was investigated upon energization of the membrane by an artificially generated ΔpH and an electric potential difference, Δψ. Using a rapid mixing system, rates of ATP synthesis were studied at short reaction times (<150 ms) where all relevant parameters (ΔpH, Δψ, substrate and product concentrations) remain practically constant at their initial values. Under these conditions it was found:1The maximal rate of ATP synthesis obtained under these artificial conditions is the same as that obtained by light‐induced ATP synthesis.2The turnover number of the ATPase is 410 s−1.3The rate of ATP synthesis depends in a sigmoidal way on the transmembrane electrochemical potential difference of protons, Δψ H +, regardless of the relative contributions by ΔpH and Δψ.4The functional dependence of the rate of ATP synthesis on Δμ H +does not reflect the kinetics of the catalytic events at the ATPase but the transformation of the ATPase from an inactive to a catalytically active state.5The binding of two protons to the ATPase from the inside of the membrane is

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880706

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractMeasurements of dielectric and calorimetric properties and of the lamellar repeat distance revealed a structural phase transition at temperatures below 0°C in hydrated phospholipid (DPPC) bilayers. The transition is marked 1. by a jump of the dielectric constant at microwave frequencies, 2. by a jump of the lamellar repeat distance, and 3. by an enthalpy of transition. These observations are interpretated by a change of the amount of bound water. Below the transition temperature only seven H2O molecules per lipid molecule are left bound as interlamellar water independent on the amount bound at higher temperatures. The observed loss of bound water at this subzero temperature phase transition may represent a physical process for irreversible freezing effects

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880707

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractThe pressure dependence of the linear birefringence of a cholesteric liquid crystal at constant temperature could be determined for the first time by combined measurements of the optical rotatory power and the selective light reflection up to 130°C and 3000 bar. From the birefringence data obtained in this way the corresponding pressure dependence of the order parameter η representing the degree of parallel orientation of the molecules was calculated fairly precisely. From these data follows that η at the transition point to the isotropic liquid phase is independent of the transition pressu

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880708

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractInvestigations in the temperature range −45 ≤θ/°C ≤ + 25 on LiBF4solutions in dimethoxyethane from infinite dilution to saturation permit to exemplify the features of conductance in solvents of low permittivity. Conductance measurements on thoroughly purified materials with the help of a measuring equipment known to produce precise data yield a complete set of conductance curves from infinite dilution to saturation at all temperatures of the program. The conductance curves show a minimum and a maximum of equivalent conductance and the change from positive to negative and once more to positive temperature coefficients of conductance. Various methods both for the evaluation of the limiting conductances,Λ∞, and the formation constants of ion pairs,KA, triple ions,KT, are critically discussed and reliable data for the LiBF4solutions in dimethoxyethane at all temperatures of the program are co

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880709

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractA 300 MHz proton NMR determination of the thermodynamic parameters of the Schlenk equilibrium of tert‐butylmagnesium bromide in tetrahydrofuran is reported for the temperature range 285‐−330 K. In solutions where bromide is in excess over tert‐butyl groups other equilibria intervene below 285 K. However when the Grignard stoichiometry prevails concentrations are governed by the Schlenk equilibrium and its determined parameters to at least 260 K. — The Ashby assignments of the1H resonances (low field: tBuMgBr, high field: tBu2Mg) are confirmed over the temperature range of our measurements but have been found to invert below 200‐−210 K. Resonances arising from impurities are assigned. — The13C spectrum is assigned. The CH3resonance of tBu2Mg occurs at a lower field than that of tBuMgBr. The equilibrium parameters determined from the13C spectra over the temperature range 282‐−322 K agree with those determined from the1H spectra though thei

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880710

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractMeasurements of density of an isobutyric acid (COOD)/D2O mixture of critical composition (upper critical point; critical composition:xDA,c= 0.113;xDA: mole fraction of acid; critical temperature:Tc= 45.738°C) as function of temperature in the one fluid phase region are reported. The functionp=P1+P2t+P3t(1 ‐ α)is fitted to the data (p: density;P1,P2,P3: constants;t: reduced temperature difference (T–Tc)/Tc; α: critical exponent, α = 0.11).P3has a positive value. Consequently, the coefficient dTc/dP(pressure dependence of critical temperature) has to be negative for thermodynamic reasons. This is confirmed by direct measurements. The experimentally determined values ofP1,P3and dTc/dPtogether with the value of the correlation length of local concentration fluctuations taken from the literature are consistent with the predictions of the amplitude relation of two‐scale factor universality. — For isobutyric acid/H2O, D2O mixtures of critical composition there exists a linear relation between the coefficient dTc/dPand the equivalent fraction of exchangeable protonsY(=nH/(nH+nD)). dTc/dPdecreases from dTc/dP= −40.9 mK bar−1for DA/D2O (Y=0) to dTc/dP= −55.0 mK bar

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880711

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY

摘要:

AbstractThe absorption and velocity of ultrasound are measured in a critical mixture of nitro‐benzene and isooctane (2,2,4‐trimethyl‐pentane) as function of the temperature difference (T–Tc) in the homogeneous phase region. The critical data of the system having an upper critical point are: critical temperatureTc= 29.16°C; critical compositionync= 0.525 (mass fraction of nitro‐benzene). The experiments are carried out in the temperature range 0.3 K ≤ (T–Tc) ≤ 21.8 K at seven frequencies between 9 MHz and 45 MHz. Four mixtures with off‐critical compositions and the pure components are also studied. — The sound absorption of the critical mixture is analysed in terms of the Bhattacharjee‐Ferrell theory. At the critical temperature the frequency dependence of ultrasound absorption is in agreement with the predictions of this theory. The data obtained at temperatures away from the critical temperature collapse on a single scaling curve when plotted as function of a reduced frequency given by the theory. Not all of the input data for the calculation of the temperature‐independent coefficient ω0of the temperature‐dependent characteristic relaxation frequency are available for that system. Therefore, the coefficient ω0is used as free parameter in a fitting procedure of the theoretical scaling function to the experimental scaling function. The best fit is obtained with ω0= 15 MHz. The agreement between theory and experiment is good and supports the universality concept of t

ISSN:0005-9021    

DOI:10.1002/bbpc.19840880712

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1984

数据来源: WILEY