COMPACT POLYMERS
COMPACT POLYMERS
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DOI：
10.1021/ma00202a031
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发表时间：
1989-12-01
期刊：
影响因子：
5.5
通讯作者：
DILL, KA
中科院分区：
文献类型：
--
作者：
CHAN, HS;DILL, KA
摘要：聚合物的紧密构象是球状蛋白质天然状态的主要构象，因此具有重要意义。我们研究了二维正方晶格上的短链构型的计算机穷举计算的紧凑的聚合物状态。可访问的配置的数量被发现取决于两个因素：（i）配置自由度和排除的体积，在过去被广泛研究，和（ii）的紧凑对象的“形状”熵。此外，我们还研究了致密聚合物中环形成的概率以及环对之间的拓扑相关性。我们发现，有一个内在的空间驱动力的环被配置成螺旋和反平行片在紧凑的链，类似于我们最近发现的更开放的链。此外，我们详细研究了几个构象后，剩余的巨大减少的构型空间后，增加的紧凑性。这几种构象绝大多数是由二级结构主导的：螺旋、反平行和平行片层以及转弯。这种优势随链长而增加。发现构造具有小于约50%二级结构的紧凑链是极其困难的。这表明蛋白质二级结构形成的驱动力可能是非特异性空间相互作用，而不是氢键或其他特异性相互作用。
ABSTRACT; The compact conformations of polymers are important because they are the principal con-figurations of the nativestates of globular proteins. We study the compact polymeric state by exhaustive computer enumeration of short-chain configurations on two-dimensional square lattices. The number of accessible configurations is found to depend on two factors:(i) configurational freedom and excluded volume, extensively studied in the past, and (ii) a “shape” entropy of the compact object. In addition, we study the probability of loop formation in compact polymers and topological correlations among pairs of loops. We find that there is an intrinsic steric driving force for loops to be configured into helices and antiparallel sheets in compact chains, similar to that we have recently found for more open chains. Also, we study in detail the few conformations that remain after the enormous reduction of configurational space upon increasing the compactness. Those few conformations are overwhelmingly dominated by secondary structures: helices, antiparallel and parallel sheets, and turns. This dominance increases with chain length. It is found to be exceedingly difficult to configure a compact chain with less than about 50% secondary structure. This suggests that the driving force for formation of secondary structures in proteins may be nonspecific steric interactions rather than hydrogen-bonding or other specific interactions.