实际无规杂聚物的平衡性质及其与球状和天然未折叠蛋白质的相关性
Equilibrium properties of realistic random heteropolymers and their relevance for globular and naturally unfolded proteins
摘要：
随机杂聚物不显示球状蛋白质的典型平衡性质，但却是理解蛋白质物理学的起点，特别是描述其非天然状态。到目前为止，它们的研究仅限于热力学极限下的平均场模型，或晶格上极小链的计算机模拟。在描述了一种自调整并行回火技术，有效地采样的低能量状态的挫折系统，而不需要调整系统相关的参数的算法，我们将其应用到随机杂聚物在连续空间中移动。我们表明，如果单体之间的平均相互作用是负的，通常的描述通过随机能量模型是几乎正确的，只要它被扩展到非紧凑的构象。如果平均相互作用是正的，那么这样一个简单的描述就会出现，系统的行为方式就更类似于伊辛自旋玻璃。前一种情况是球状蛋白质变性状态的模型，后一种情况是天然未折叠蛋白质的模型，其平衡性质因此产生了质的不同。
英文摘要：
Random heteropolymers do not display the typical equilibrium properties of globular proteins, but are the starting point to understand the physics of proteins and, in particular, to describe their non-native states. So far, they have been studied only with mean-field models in the thermodynamic limit, or with computer simulations of very small chains on lattice. After describing a self-adjusting parallel-tempering technique to sample efficiently the low-energy states of frustrated systems without the need of tuning the system-dependent parameters of the algorithm, we apply it to random heteropolymers moving in continuous space. We show that if the mean interaction between monomers is negative, the usual description through the random energy model is nearly correct, provided that it is extended to account for non-compact conformations. If the mean interaction is positive, such a simple description breaks out and the system behaves in a way more similar to Ising spin glasses. The former case is a model for the denatured state of glob- ular proteins, the latter of naturally-unfolded proteins, whose equilibrium properties thus result qualitatively different.
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