Prados A, Carpio A, Bonilla L L
Física Teórica, Universidad de Sevilla, Apartado de Correos 1065, E-41080 Sevilla, Spain.
Phys Rev E Stat Nonlin Soft Matter Phys. 2013 Jul;88(1):012704. doi: 10.1103/PhysRevE.88.012704. Epub 2013 Jul 8.
We analyze the force-extension curve for a general class of systems, which are described at the mesoscopic level by a free energy depending on the extension of its components. Similarly to what is done in real experiments, the total length of the system is the controlled parameter. This imposes a global constraint in the minimization procedure leading to the equilibrium values of the extensions. As a consequence, the force-extension curve has multiple branches in a certain range of forces. The stability of these branches is governed by the free energy: there are a series of first-order phase transitions at certain values of the total length, in which the free energy itself is continuous but its first derivative, the force, has a finite jump. This behavior is completely similar to that observed in real experiments with biomolecules like proteins and with other complex systems.
我们分析了一类一般系统的力-伸长曲线，这类系统在介观层面由依赖于其组分伸长的自由能来描述。与实际实验中所做的类似，系统的总长度是控制参数。这在导致伸长平衡值的最小化过程中施加了一个全局约束。因此，力-伸长曲线在一定力的范围内有多个分支。这些分支的稳定性由自由能决定：在总长度的某些值处存在一系列一阶相变，其中自由能本身是连续的但其一阶导数，即力，有一个有限的跃变。这种行为与在蛋白质等生物分子以及其他复杂系统的实际实验中观察到的行为完全相似。
