Dynamic strength of molecular adhesion bonds
Dynamic strength of molecular adhesion bonds
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DOI：
10.1016/s0006-3495(97)78802-7
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发表时间：
1997-04-01
影响因子：
3.4
通讯作者：
Ritchie, K
中科院分区：
文献类型：
--
作者：
Evans, E;Ritchie, K
在生物学中，细胞界面上、细胞内和细胞下的分子连接主要是由弱的非共价相互作用引起的。如果保持足够的时间，这些粘结在任何拉力水平下都会失效，因此，当用超灵敏的力探头测试时，我们预计粘结材料的强度和界面处的粘结强度将是时间和加载率相关的特性。为了检验他能从键强度测量中学到什么，我们将Kramers的液体反应动力学理论推广到力作用下的键解离，并用SMART蒙特卡特(布朗动力学)模拟键断裂来检验预测。根据定义，粘结强度是在反复破坏试验中产生最频繁破坏的力，即破裂力分布的峰值。通过模拟验证，理论表明粘结强度经历了三个加载速率的动态变化过程。首先，键合强度以临界加载速率(大于或等于0)出现，在该临界加载速率下自发解离的频率刚刚足够频繁以将分布峰值保持在零力，在紧接在临界速率之上的慢加载区域中，强度作为加载速率的弱幂增长并且反映了力与键合势的初始耦合，在较高的加载速率下，存在交叉到快速区域，在该快速区域中，无论吸引力的类型如何，在几十年中，随着加载速率的对数，强度继续增加，最后，在接近分子动力学模拟区域的超快加载速率下，键势迅速被快速增加的力所淹没，因此，只有结构上的裸露摩擦阻力才能延缓分离，因此，为了揭示支配键强度的能量格局，必须在巨大的时间跨度内检查分子粘附力。然而，在实验室中的力测量的时间域与极快的分子运动尺度之间存在着显著的差距。使用生物素-亲和素键的模拟结果(Izraev，S.，S.Stepaniants，M.Balsera，Y.Oono和K.Schulten)。1997年。生物素亲和素-生物素复合体解离的分子动力学研究。，本期)，我们描述了布朗动力学如何帮助弥合分子动力学和探针测试之间的差距。
In biology, molecular linkages at, within, and beneath cell interfaces arise mainly from weak noncovalent interactions. These bonds will fail under any level of pulling force if held for sufficient time, Thus, when tested with ultrasensitive force probes, we expect cohesive material strength and strength of adhesion at interfaces to be time- and loading rate-dependent properties. To examine what can he learned from measurements of bond strength, we have extended Kramers' theory for reaction kinetics in liquids to bond dissociation under force and tested the predictions by smart Monte Carte (Brownian dynamics) simulations of bond rupture. By definition, bond strength is the force that produces the most frequent failure in repeated tests of breakage, i.e., the peak in the distribution of rupture forces. As verified by the simulations, theory shows that bond strength progresses through three dynamic regimes of loading rate. First, bond strength emerges at a critical rate of loading (greater than or equal to 0) at which spontaneous dissociation is just frequent enough to keep the distribution peak at zero force, In the slow-loading regime immediately above the critical rate, strength grows as a weak power of loading rate and reflects initial coupling of force to the bonding potential, At higher rates, there is crossover to a fast regime in which strength continues to increase as the logarithm of the loading rate over many decades independent of the type of attraction, Finally, at ultrafast loading rates approaching the domain of molecular dynamics simulations, the bonding potential is quickly overwhelmed by the rapidly increasing force, so that only naked frictional drag on the structure remains to retard separation, Hence, to expose the energy landscape that governs bond strength, molecular adhesion forces must be examined over an enormous span of time scales. However, a significant gap exists between the time domain of force measurements in the laboratory and the extremely fast scale of molecular motions. Using results from a simulation of biotin-avidin bonds (Izrailev, S., S. Stepaniants, M. Balsera, Y. Oono, and K. Schulten. 1997. Molecular dynamics study of unbinding of the avidin-biotin complex, Biophys. J., this issue), we describe how Brownian dynamics can help bridge the gap between molecular dynamics and probe tests.