二维蛋白质模型分子在折叠过程中的构象研究

蛋白质在折叠过程中其构象要发生明显变化 .采用精确计数法 ,计算了在蛋白质折叠的不同阶段其尺寸大小及其分布情况 .发现在折叠的初期 ,分子的尺寸比较大 ,其分布也比较宽 .在折叠的后期 ,分子的尺寸比较小 ,其分布比较窄 .不同的氨基酸序列 ,其分子尺寸的分布也不同 .对于可折叠的氨基酸序列 ,在平均尺寸大小附近出现的几率特别大 .同时还计算了比值SN DN.这里SN 为可设计序列数目 (Thenumberofdesigningsequences) ,DN 为可设计构象数目 (Thenumberofdesignableconformations) ,并有关系- 1 6 8 4 +0 32 5 5N≤SN DN ≤- 0 86 6 4 +0 312 5N　 (N ≥ 13)通过这些研究以提高对折叠过程的认识

CONFORMATION STUDIES OF TWO-DIMENSIONAL MODEL MOLECULES OF PROTEINS IN THE PROCESS OF FOLDING

There are many changes for protein molecules in conformations in the process of folding.The mean square radius of gyration and its distribution function P(S) were calculated by using the exact enumeration calculation method.It was found that the dimension was large at the beginning of folding, and the range of its distribution was also wide.However,the dimension became small and compact at the end of folding,and the range of its distribution also became small.The mean square radius of gyration 〈S+2〉-t with the number of contacts t is shown as〈S+2〉-t/Nl+2=a+bNwhere a depends on the number of contacts ( t ) and b is independent of the number of contacts ( t ),and N is the chain length of two dimensional protein molecules.There are different distributions for various residue sequences.The value of P(S) nearby the mean square radius of gyration is more large for the folding sequence.A ratio of S-N/D-N was also calculated. S N is the number of designing sequences,and D N is the number of designable conformations.It was found that the ratio may be expressed as -1 684+0 3255N≤S N/D N≤-0 8664+0 3125N (N≥13)These results may provide some insights into the folding of proteins molecules.