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Taming Rugged Free Energy Landscapes Using an Average Force.
Accounts of Chemical Research ( IF 16.4 ) Pub Date : 2019-11-04 , DOI: 10.1021/acs.accounts.9b00473
Haohao Fu 1 , Xueguang Shao 1, 2 , Wensheng Cai 1 , Christophe Chipot 3, 4
Affiliation  

The observation of complex structural transitions in biological and abiological molecular objects within time scales amenable to molecular dynamics (MD) simulations is often hampered by significant free energy barriers associated with entangled movements. Importance-sampling algorithms, a powerful class of numerical schemes for the investigation of rare events, have been widely used to extend simulations beyond the time scale common to MD. However, probing processes spanning milliseconds through microsecond molecular simulations still constitutes in practice a daunting challenge because of the difficulty of taming the ruggedness of multidimensional free energy surfaces by means of naive transition coordinates. To address this limitation, in recent years we have elaborated importance-sampling methods relying on an adaptive biasing force (ABF). In this Account, we review recent developments of algorithms aimed at mapping rugged free energy landscapes that correspond to complex processes of physical, chemical, and biological relevance. Through these developments, we have broadened the spectrum of applications of the popular ABF algorithm while improving its computational efficiency, notably for multidimensional free energy calculations. One major algorithmic advance, coined meta-eABF, merges the key features of metadynamics and an extended Lagrangian variant of ABF (eABF) by simultaneously shaving the barriers and flooding the valleys of the free energy landscape, and it possesses a convergence rate up to 5-fold greater than those of other importance-sampling algorithms. Through faster convergence and enhanced ergodic properties, meta-eABF represents a significant step forward in the simulation of millisecond-time-scale events. Here we introduce extensions of the algorithm, notably its well-tempered and replica-exchange variants, which further boost the sampling efficiency while gaining in numerical stability, thus allowing quantum-mechanical/molecular-mechanical free energy calculations to be performed at a lower cost. As a paradigm to bridge microsecond simulations to millisecond events by means of free energy calculations, we have applied the ABF family of algorithms to decompose complex movements in molecular objects of biological and abiological nature. We show here how water lubricates the shuttling of an amide-based rotaxane by altering the mechanism that underlies the concerted translation and isomerization of the macrocycle. Introducing novel collective variables in a computational workflow for the rigorous determination of standard binding free energies, we predict with utmost accuracy the thermodynamics of protein–ligand reversible association. Because of their simplicity, versatility, and robust mathematical foundations, the algorithms of the ABF family represent an appealing option for the theoretical investigation of a broad range of problems relevant to physics, chemistry, and biology.

中文翻译:

使用平均力驯服崎Free的自由能源景观。

在纠缠于分子运动(MD)模拟的时间尺度内,对生物和非生物分子对象中复杂结构转变的观察常常因与纠缠运动相关的大量自由能垒而受阻。重要采样算法是研究稀有事件的一种强大的数值方案,已被广泛用于将模拟扩展到MD常用的时间范围之外。然而,由于难以通过朴素的过渡坐标来适应多维自由能表面的坚固性,因此通过微秒分子模拟进行毫秒级的探测过程实际上仍然是一项艰巨的挑战。为了解决这一局限性,近年来,我们已经制定了依赖于自适应偏压力(ABF)的重要性抽样方法。在此帐户中,我们回顾了旨在绘制与物理,化学和生物相关的复杂过程相对应的崎energy自由能源格局的算法的最新进展。通过这些发展,我们扩大了流行的ABF算法的应用范围,同时提高了其计算效率,尤其是多维自由能的计算效率。一种重要的算法进步是造币的meta-eABF,它同时消除了障碍并淹没了自由能源景观的山谷,将元动力学的关键特征与ABF的扩展拉格朗日变体(eABF)融合在一起,并且收敛速度高达5 -比其他重要性采样算法大两倍。通过更快的收敛和增强的遍历特性,meta-eABF代表了毫秒级时间尺度事件模拟中的重要一步。在这里,我们介绍该算法的扩展,特别是其经过良好调和和副本交换的变体,它们在提高数值稳定性的同时进一步提高了采样效率,从而允许以较低的成本执行量子力学/分子机械自由能的计算。 。作为通过自由能计算将微秒模拟与毫秒事件联系起来的范例,我们已应用ABF系列算法分解生物和非生物学性质的分子对象中的复杂运动。我们在这里展示了水如何通过改变大环的一致翻译和异构化机制来润滑酰胺基轮烷的穿梭作用。在用于严格确定标准结合自由能的计算工作流程中引入新的集体变量,我们可以最高精度地预测蛋白质-配体可逆缔合的热力学。由于它们的简单性,多功能性和强大的数学基础,ABF系列的算法为对与物理学,化学和生物学有关的广泛问题进行理论研究提供了一个有吸引力的选择。
更新日期:2019-11-04
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