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arXiv 2102.05162cond-mat.soft
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力学约束下生物大分子的热力学平衡

Thermodynamic equilibrium of biological macromolecules under mechanical constraints

Ashkan Shekaari, Mahmoud Jafari

摘要:

平衡蛋白质和其他生物大分子是这种生物系统的分子动力学模拟的基础,在这种生物系统中,它们在没有任何外部施加的机械约束的情况下执行自由动力学,直到与周围环境达到热力学平衡。然而,在一些重要的情况下,我们必须平衡的利益系统中不断存在的某些约束,被称为约束平衡在本工作中。这种类型的一个清楚的例子是单个淀粉样蛋白\b{eta}链或RNA,当反应坐标被定义为链两端之间的距离时,我们感兴趣的是进行复制交换伞形采样,以绘制相关的自由能谱作为相关的依赖量。在这种情况下,每个样品必须在两端固定的情况下平衡。在这里,我们引入了一个模拟技巧,使用转向分子动力学来执行这种所谓的约束平衡。然后,我们应用该方法平衡具有固定末端的淀粉样蛋白β十二聚体原纤维的单个拉伸的\b{eta}链。研究了总能量和实际固定的SMD原子在总时间跨度上所受的力的相关曲线,广泛地支持了这种平衡的有效性。

英文摘要:

Equilibrating proteins and other biomacromolecules is cardinal for molecular dynamics simulation of such biological systems in which they perform free dynamics without any externally-applied mechanical constraint, until thermodynamic equilibrium with the surrounding is attained. However, in some important cases, we have to equilibrate the system of interest in the constant presence of certain constraints, being referred to as constrained equilibration in the present work. A clear illustration of this type is a single amyloid \b{eta}-strand or RNA, when the reaction coordinate is defined as the distance between the two ends of the strand and we are interested in carrying out replica-exchange umbrella sampling to map the associated free energy profile as the dependent quantity of interest. In such cases, each sample has to be equilibrated with the two ends fixed. Here, we introduced a simulation trick to perform this so-called constrained equilibration using steered molecular dynamics. We then applied this method to equilibrate a single, stretched \b{eta}-strand of an amyloid beta dodecamer fibril with fixed ends. Examining the associated curves of the total energy and the force exerted on the practically-fixed SMD atom over the total timespan broadly supported the validity of this kind of equilibration.

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