二维HP格点模型中的紧密高分子链构象及其热力学性质的研究  

STUDY OF NATIVE CONFORMATIONS AND THERMODYNAMIC PROPERTIES OF TWO-DIMENSIONAL HP COMPACT POLYMERS

作　　者：章林溪[1] 金进生[1] 王向红[1] 叶高翔[1] 赵得禄[2] 

机构地区：[1]浙江大学物理系,杭州310028 [2]中国科学院化学研究所分子科学中心高分子物理实验室,北京100080

出　　处：《高分子学报》2002年第4期515-519,共5页Acta Polymerica Sinica

基　　金：国家自然科学基金 (基金号 2 98740 2 1和 2 0 1740 3 6);国家重点基础研究专项经费 (批准号 95 预 12;G19990 64 80 0 );浙江省自然科学基金 (基金号 10 10 0 2 )

摘　　要：采用二维HP模型用精确计数法和MonteCarlo方法研究了链长为N(≤ 2 2 )的紧密高分子链的构象和热力学性质 .发现不同HP序列的紧密高分子链的平均自由能和平均配分函数与链长N存在关系 :〈F〉=aN+b ,　ln〈Z〉=a′N +b′ .同时发现对于可折叠成基态且简并度为 1的紧密高分子链 ,其平均自由能和平均配分函数与链长N也存在相似的关系 .在HP模型中对于链长为N的紧密高分子链 ,存在着 2 N + 1 个不同的HP序列 .我们发现可以折叠成基态且简并度为 1的蛋白质分子的HP序列数目NS 为NS =a× 2 N+ 1 　 (a =0 0 2 5 ) ,对应的HP序列中 ,疏水基团 (H)数目的含量为 4 0 %～ 6 0 %的序列出现的几率最大 .同时在这些紧密高分子链中有些具有相同的结构 ,发现结构的‘简并度’为 3 3～ 4 0 (10≤N≤ 16 ) .在紧密高分子链折叠过程中 ,折叠的初期能量下降比较快 ,折叠的中期能量下降比较缓慢 。The native conformations and thermodynamic properties of, compact polymers with chain length N (N less than or equal to 22) are investigated by using exact enumeration calculation method and Monte Carlo simulation method employing the HP model. The average Helmholtz free energy ( F) and average partition function (Z) can be expressed in the form of (F) = aN + b, ln (Z) = a'N where N is chain length of compact chains a, b and a', b' only depend on temperature.. We also find that the compact chains-with unique ground states have similar relationship in the thermodynamic property and the chain length. In the HP model, the number of sequences of conformations for a protein of chain length N is 2, and the number of sequences with unique ground state may be expressed as N-S: N-S = a x 2(N+1) ( a = 0.025). In these HP sequences, the sequences with 40% similar to 60% in the percentage of H residue have a large probability of emergence. We find that many structures are the same in those unique ground state, and the values of degeneration of structure are 3.3 - 4.0 (10 less than or equal to N less than or equal to 16) In - the processing of folding, the change of energy is fast in the beginning of folding, slow in the middle of floding and also fast in the end of folding of proteins.

关 键 词：二维HP格点模型 构象 热力学性质 紧密高分子链 二维HP模型 精确计数法 MONTE CARLO方法 折叠 

分 类 号：O631[理学—高分子化学]