基于弹性网络模型的蛋白质变构路径与关键残基识别研究

目的 变构效应在蛋白质生物学功能执行过程中发挥着重要的调控作用,如何基于蛋白质空间结构,有效识别变构信号的传播路径和关键的残基位点是蛋白质结构-功能关系研究领域的热点科学问题。方法 本研究利用基于弹性网络模型(elastic network model,ENM)的力分布计算方法,通过分析蛋白质对外力的响应过程,来识别体系的变构路径以及变构过程中的关键残基。在该方法中,对蛋白质的关键变构位点施加外力,通过对体系形变以及内力分布情况的分析,有效识别与外力承载区域形变相耦合的关键残基,从而得到力信号在蛋白质结构内的传播路径。结果 利用该方法研究了人类磷酸甘油酸激酶(human phosphoglycerate kinase,h PGK)和蛋白质酪氨酸磷酸酶(protein tyrosine phosphatase,PTP) PDZ2结构域的变构调控路径和关键残基。对于h PGK,识别出从底物结合位点到铰链区的两条变构信号传导路径。对于PTP PDZ2,也成功识别出从配体结合位点传递到蛋白质远端的两条长程变构调控路径。计算结果与实验和分子动力学(molecular dynamics,MD)模拟得到的结果一致。结论 本研究为蛋白质体系关键残基识别及变构路径研究提供了有效的分析方法。

Application of crystal plasticity modeling in equal channel angular extrusion

Some applications of crystal plasticity modeling in equal channel angular extrusion（ECAE） of face-centered cubic metals were highlighted.The results show that such simulations can elucidate the dependency of grain refinement efficiency on processing route and the directionality of substructure development,which cannot be explained by theories that consider only the macroscopic deformation behavior.They can also capture satisfactorily the orientation stability and texture evolution under various processing conditions.It is demonstrated that crystal plasticity models are useful tools in exploring the crystallographic nature of grain deformation and associated behavior that are overlooked or sometimes erroneously interpreted by existing phenomenological theories.

Effects of annealing treatments on forming performance of zirconium alloys

The effects of annealing treatments(ATs)on the microstructure of Zr-Sn-Nb alloy strips were studied.Based on the characteristics of strips for nuclear fuel assemblies,punching experiments were carried out and the formability of zirconium alloy strips was quantitatively evaluated.The results indicate that the proportions of small-angle grain boundaries of the zirconium alloy under conditions of annealing treatment at 580°C(ATⅠ)and annealing treatment at 620°C(ATⅡ)are 14.3%and 23.2%,respectively,while that of the as-received material is 12.4%.And the forming limit margin fields of the zirconium alloy under ATⅠcan reach 0.43%,while the values of the as-received material and the ATⅡare-0.35%and-2.8%,respectively.The annealing process affects the evolution process of the strip recrystallization texture and the grain size.Moreover,the total texture and pole density are closely related to the degree of anisotropy of the strip.Besides,the small-angle grain boundary affects the strain path and crack expansion of the necking unit during the strip punching process,while the grain size affects the hardening exponent of the material.

Pyrolysis Mechanisms of Quinoline and Isoquinoline with Density Functional Theory

The pyrolysis mechanisms of quinoline and isoquinoline were investigated using the density functional theory of quantum chemistry,including eight reaction paths and a common tautomeric intermediate 1-indene imine.It is concluded that the conformational tautomerism of the intermediate decides the pyrolysis products(C6H6,HC≡C—C≡N,C6H5C≡N and HC≡CH)to be the same,and also decides the total disappearance rates of the reactants to be the same,for both original reactants quinoline and isoquinoline during the pyrolysis reaction.The results indicate that the intramolecular hydrogen migration is an important reaction step,which often appears in the paths of the pyrolysis mechanism.The activation energies of the rate determining steps are obtained.The calculated results are in good agreement with the experimental results.