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961.
Rabindra N. Roy James J. Gibbons Jonathan K. Trower Gregory A. Lee 《Journal of solution chemistry》1980,9(7):535-551
Activity coefficients of hydrochloric acid in mixed solutions of manganous chloride at twelve ionic strengths, from 0.1 to 5.0 mole-kg–1, were obtained from emf measurements of cells without liquid junction at five temperatures from 5 to 45°C. The data were interpreted in terms of the simple and convenient Pitzer treatment. Activity coefficients for manganous chloride in the mixtures were also derived using Pitzer's equations. Hydrochloric acid follows Harned's rule fromI=0.1 to 3.0 mole-kg–1, as concluded by Downes, whereas quadratic terms are warranted fromI=3.5 to 5.0 mole-kg–1. Contrary to Downes' conclusion, Harned's rule clearly does not hold true for manganous chloride at most ionic strengths. 相似文献
962.
The thermal motion of a long-chain molecule dispersed in a solvent is examined in terms of the velocity autocorrelation, in a reference frame attached to a subunit of the chain. 相似文献
963.
J. P. Stark 《Journal of statistical physics》1971,3(4):395-399
The classical canonical partition function for a one-dimensional, two-component system is examined for the case of nearest-neighbor interactions. The quasi-chemical model of solid solutions is found to be a natural consequence of the definition of the partition function when one replaces the normal configurational energy with a configurational free energy. Consequently, the quasi-chemical theory may be viewed as a consequence of the definition of the partition function and not as merely a physically pleasing model. 相似文献
964.
James L. Monroe 《Journal of statistical physics》1992,67(5-6):1185-1200
We continue an earlier study of multisite interaction Ising spin models on Husimi trees. In particular, attention is given to systems with both a nearestneighbor pair interaction and three-site interactions. We use our calculations of the phase diagrams of the systems on Husimi trees as approximations of systems with the same interactions but on a regular lattice, e.g., the triangle lattice. Specific models where exact results are available are used as test cases. All of the work involves computation of quantities, such as the magnetization, by iterative processes. Hence we are dealing with a discrete map and for certain values of the interaction strengths we obtain for the magnetization diagram results involving period doubling, chaos, period-three windows, etc., all phenomena of recent interest in connection with dynamical systems and now associated with certain Ising spin systems. 相似文献
965.
Quantum chromodynamics corrections to orderα
s (the running coupling constant), using the quark-parton approach are calculated for the spin-dependent structure functions
in deep-inelastic polarised electron-nucleon scattering. Consequences of these corrections for the Bjorken sum rule and the
asymmetry in the case of longitudinally polarised (with respect to the beam) nucleons is discussed which could provide possible
tests of quantum chromodynamics. Comparison of our results with the moments of the flavour non-singlet contribution to the
structure functions obtained using operator product expansion is also given.
An erratum to this article is available at . 相似文献
966.
Summary We analyse saturated-absorption and two-photon absorption line shapes in Doppler-broadened three-level systems with nearly
degenerate resonance frequencies. The two counterpropagating equal-frequency laser beams of arbitrary intensity irradiating
the sample are allowed to couple to both atomic transitions. Various Doppler-free resonances associated to two- and three-photon
effects occur. Their saturating behaviour is analysed. A comparison is made with experiments by Woerdmann and Schuurmans and
by Himbertet al.
To speed up publication, the authors of this paper have agreed to not receive the proofs for correction. 相似文献
967.
sio Bessa Ramos 《Macromolecular theory and simulations》2011,20(5):320-328
In the present work, we revisit the effect of macromolecular crowding on the sizes of flexible neutral polymer chains. Motivated by recent experimental measurements on crowding effects on neutral flexible polymers chains, we perform Monte Carlo simulations on a model system consisting of hard spheres (HS) and a neutral flexible polymer chain. We find that, depending on the ratio of the sizes of the colloidal particles to the sizes of the polymer chain, and thus, on the extent of the colloid partitioning among the chain segments and the solution, the flexible polymeric coil may be either continuously compressed, or initially compressed followed by a reswelling at high enough colloid concentration. The chain behavior is thus nonmonotonic, a point which, apart from the work of Khalatur et al., has not so far been stressed in simulations of flexible polymer chains under crowding conditions. A thermodynamic model for the polymer–colloid interactions based on the Gibbs–Duhem equation and on a “Flory‐type” argument is also presented, emphasizing the indirect influence of macromolecular crowding on the monomers chemical potential. We show explicitly that under crowding conditions, the colloids are driven into the most compact coil states. These analytical results are compared with the results of the potential of mean force between the chain center of mass and the colloids obtained from the Monte Carlo simulations, and a reasonable agreement is found. The implications of the aforementioned results are further discussed in the context of biological systems, specially those for which macromolecular crowding is supposed to play the important role of including preferentially other (charged) macromolecules into the colloid‐compressed polymer phase.
968.
Kim CG Lemaitre V Watts A Fischer WB 《Analytical and bioanalytical chemistry》2006,386(7-8):2213-2217
Vpu is an 81-amino-acid auxiliary protein of the genome of HIV-1. It is proposed that one of its roles is to enhance particle
release by self-assembling to form water-filled channels enabling the flux of ions at the site of the plasma membrane of the
infected cell. Hexamethylene amiloride has been shown to block Vpu channel activity when the protein is reconstituted into
lipid bilayers. In a docking approach with monomeric, pentameric and hexameric bundle models of Vpu corresponding to the transmembrane
part of the protein, a putative binding site of hexamethylene amiloride is proposed and is compared with the site for the
nonpotent amiloride. The binding mode for both ligands is achieved by optimizing hydrogen bond interactions with serines.
Binding energies and binding constants are the lowest for protonated hexamethylene amiloride in the pentameric bundle.
Figure The proposed binding site of the Vpu channel blocker hexamethylene amiloride within the lumen of the Vpu bundle. The bundle
is a homo-pentamer with each monomer consisting of the first 32 amino acids of Vpu including the transmembrane part of the
protein which is encoded by HIV-1. The bundle atoms are shown in their van der Waals representation and the helix backbone
in a ribbon representation. Residues Trp-23 and Ser-24 are highlighted as sticks. Hexamethylene amiloride is shown in yellow
(C atoms) and blue (N atoms) 相似文献
969.
Shi X Takamizawa A Nishimura Y Hiraoka K Akashi S 《Journal of mass spectrometry : JMS》2006,41(8):1086-1095
Laser spray, which is a newly developed ionization technique, can characterize the stability of noncovalent complexes in the solution phase. By using this advantage, laser spray has been applied to probe the intrinsic stability of double-stranded DNA (dsDNA) sequences and their binding affinities with various drugs in the solution phase. Systematic experiments were carried out using six 16-mer and three 22-mer dsDNA oligomers, together with the complexes of the 16-mer dsDNA with minor groove binders: berenil, Hoechst 33342, DAPI, and netropsin. Dissociation curves for each dsDNA or each complex were plotted as a function of laser power. The laser power (E50%), where 50% of each dsDNA or each complex was dissociated, was compared with its melting temperature (Tm) determined by UV spectroscopy. Linear correlations between E50% and Tm were obtained not only for the dsDNA oligomers (correlation factor r = 0.9835) but also for the 16-mer dsDNA complexes with minor groove binders (r = 0.9966). In addition, laser spray has successfully clarified the binding affinities of a 16-mer dsDNA with two intercalators: daunomycin and nogalamycin. In the case of the dsDNA-daunomycin complex, by changing the molar ratio of dsDNA : drug from 1 : 1 to 1 : 5, the concentration-dependent stability of the complex was confirmed by laser spray. The present results demonstrate that laser spray mass spectrometry can be a powerful and convenient method to investigate the relative binding affinities of dsDNA-ligand complexes in the solution phase, which could be applied to the early stage of high-throughput screening of drugs targeting for dsDNA. 相似文献
970.