Physik Department, Technische Universität München, 85748 Garching, Germany.
J Am Chem Soc. 2012 Jan 11;134(1):623-30. doi: 10.1021/ja209454a. Epub 2011 Dec 19.
Amontons' law successfully describes friction between macroscopic solid bodies for a wide range of velocities and normal forces. For the diffusion and forced sliding of adhering or entangled macromolecules, proteins, and biological complexes, temperature effects are invariably important, and a similarly successful friction law at biological length and velocity scales is missing. Hydrogen bonds (HBs) are key to the specific binding of biomatter. Here we show that friction between hydrogen-bonded matter obeys in the biologically relevant low-velocity viscous regime a simple law: the friction force is proportional to the number of HBs, the sliding velocity, and a friction coefficient γ(HB). This law is deduced from atomistic molecular dynamics simulations for short peptide chains that are laterally pulled over planar hydroxylated substrates in the presence of water and holds for widely different peptides, surface polarities, and applied normal forces. The value of γ(HB) is extrapolated from simulations at sliding velocities in the range from V = 10(-2) to 100 m/s by mapping on a simple stochastic model and turns out to be of the order of γ(HB) ≃ 10(-8) kg/s. The friction of a single HB thus amounts to the Stokes friction of a sphere with an equivalent radius of roughly 1 μm moving in water. Cooperativity is pronounced: roughly three HBs act collectively.
阿蒙顿定律成功地描述了宏观固体之间在广泛的速度和法向力范围内的摩擦。对于扩散和强制滑动的附着或纠缠的大分子、蛋白质和生物复合物，温度效应始终是重要的，而在生物长度和速度尺度上同样成功的摩擦定律则缺失。氢键 (HBs) 是生物物质特异性结合的关键。在这里，我们表明，氢键物质之间的摩擦在生物相关的低速度粘性范围内遵循一个简单的定律：摩擦力与 HBs 的数量、滑动速度以及摩擦系数 γ(HB)成正比。该定律是从原子分子动力学模拟中推导出来的，用于在存在水的情况下侧向拉动平面羟基化底物上的短肽链，适用于广泛不同的肽、表面极性和施加的法向力。γ(HB)的值是通过映射到简单的随机模型，从模拟中在滑动速度范围 V = 10(-2) 到 100 m/s 中推断出来的，结果约为 γ(HB) ≃ 10(-8) kg/s。因此，单个 HB 的摩擦力相当于在水中以大约 1 μm 的等效半径移动的球体的斯托克斯摩擦力。协同作用很明显：大约三个 HBs 集体作用。
