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101.
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103.
Jin Chen Lin-xi Zhang A-gen Xia 《高分子科学》2006,(1):13-19
It is important to know the rate of intra-molecular contact formation in proteins in order to understand how proteins fold clearly. Here we investigate the rate of intra-molecular contact formation in short two-dimensional compact polymer chains by calculating the probability distribution p(r) of end-to-end distance r using the enumeration calculation method and HP model on two-dimensional square lattice. The probability distribution of end-to-end distance p(r) of short two-dimensional compact polymers chains may consist of two parts, i.e. p(r) = p1(r) p2(r), where p1(r) and p2(r) are different for small r. The rate of contact formation decreases monotonically with the number of bonds N, and the rate approximately conforms to the scaling relation of k(N) ∝ N-α. Here the value of α increases with the contact radius a and it also depends on the percentage of H (hydrophobic) residues in the sequences of compact chains and the energy parameters of εHH, εHP and εPP . Some comparisons of theoretical predictions with experimental results are also made. This investigation may help us to understand the protein folding. 相似文献
104.
Scaling predictions for bottle‐brush polymers with a rigid backbone and flexible side chains under good solvent conditions are discussed and their validity is assessed by a comparison with Monte Carlo simulations of a simple lattice model. It is shown that typically only a rather weak stretching of the side chains is realized, and then the scaling predictions are not applicable. Also two‐component bottle brush polymers are considered, where two types (A,B) of side chains are grafted, assuming that monomers of different kind repel each other. In this case, variable solvent quality is allowed. Theories predict “Janus cylinder”‐type phase separation along the backbone in this case. The Monte Carlo simulations, using the pruned‐enriched Rosenbluth method (PERM) give evidence that the phase separation between an A‐rich part of the cylindrical molecule and a B‐rich part can only occur locally. The correlation length of this microphase separation can be controlled by the solvent quality. This lack of a phase transition is interpreted by an analogy with models for ferromagnets in one space dimension.
105.
Louis P. Lee Daniel J. Cole Mike C. Payne Chris‐Kriton Skylaris 《Journal of computational chemistry》2013,34(6):429-444
First principles electronic structure calculations are typically performed in terms of molecular orbitals (or bands), providing a straightforward theoretical avenue for approximations of increasing sophistication, but do not usually provide any qualitative chemical information about the system. We can derive such information via post‐processing using natural bond orbital (NBO) analysis, which produces a chemical picture of bonding in terms of localized Lewis‐type bond and lone pair orbitals that we can use to understand molecular structure and interactions. We present NBO analysis of large‐scale calculations with the ONETEP linear‐scaling density functional theory package, which we have interfaced with the NBO 5 analysis program. In ONETEP calculations involving thousands of atoms, one is typically interested in particular regions of a nanosystem whilst accounting for long‐range electronic effects from the entire system. We show that by transforming the Non‐orthogonal Generalized Wannier Functions of ONETEP to natural atomic orbitals, NBO analysis can be performed within a localized region in such a way that ensures the results are identical to an analysis on the full system. We demonstrate the capabilities of this approach by performing illustrative studies of large proteins—namely, investigating changes in charge transfer between the heme group of myoglobin and its ligands with increasing system size and between a protein and its explicit solvent, estimating the contribution of electronic delocalization to the stabilization of hydrogen bonds in the binding pocket of a drug‐receptor complex, and observing, in situ, the n → π* hyperconjugative interactions between carbonyl groups that stabilize protein backbones. © 2012 Wiley Periodicals, Inc. 相似文献
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107.
Atomic force microscopy (AFM) is used to measure the surface roughness of crystalline Pt thin films as a function of film thickness and growth rate. Our films were electrodeposited on Au/Cr/glass substrates, under galvanostatic control (constant current density), from a single electrolyte containing Pt4+ ions. Crystalline structure of the films was confirmed by X-ray diffraction (XRD) technique. The effect of growth rate (deposition current density) and film thickness (deposition time) on the kinetic roughening of the films were studied using AFM and roughness calculation. The data is consistent with a rather complex behaviour known as “anomalous scaling” where both local and large scale roughnesses show power law dependence on the film thickness. 相似文献
108.
W.-S. Jung F. Z. Wang S. Havlin T. Kaizoji H.-T. Moon H. E. Stanley 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(1):113-119
We investigate scaling and memory effects in return intervals between price volatilities above a certain threshold q for the
Japanese stock market using daily and intraday data sets. We find that the distribution of return intervals can be approximated
by a scaling function that depends only on the ratio between the return interval τ and its mean 〈τ〉. We also find memory effects
such that a large (or small) return interval follows a large (or small) interval by investigating the conditional distribution
and mean return interval. The results are similar to previous studies of other markets and indicate that similar statistical
features appear in different financial markets. We also compare our results between the period before and after the big crash
at the end of 1989. We find that scaling and memory effects of the return intervals show similar features although the statistical
properties of the returns are different. 相似文献
109.
We carry out a systematic study of the different contributions to the deviations of the elliptic flows from the quark number scaling in high energy heavy ion collision in a quark combination model.The effects that we considered are:the resonance decay,the flavor dependence of the quark elliptic flow and the combination of quarks/antiquarks with slightly different transverse momenta.Our results show that the deviations observed in experiments can be well reproduced within the combination framework if all the three effects are considered. We make a detailed analysis of the different contributions using a Monte-Carlo program and suggest measuring the quark number scaling in intermediate pT range more precisely. 相似文献
110.
I. McGillivray 《Potential Analysis》2002,16(3):289-303
We study the effective resistance between disjoint compact sets relative to the n-th level approximation F
n
to the generalized Sierpiski carpet in d dimensions. This yields a simple criterion for determining recurrence of simple random walk on the associated pre-fractal graph in terms of the resistance scaling factor. 相似文献