Fast Tree Search for Triangular Lattice Model and Designability Analysis
三角网格模型的快速树搜索算法及可设计性分析

Using a triangular lattice model to research designability of protein folding,we overcame parity problem of previous cubic lattice model.This paper enumerated all the sequences and compact conformations on a two-dimension triangular lattice simple model of size 4 5 6 5 4.The energy of a sequence folded into a structure is minus the number of hydrophobic amino acids in the"core"of the structures.We used two types of amino acids-hydrophohic (H) and polar (P)-to make up the sequence,so there are 2~(24) 2~(12) different sequences excluding the reverse symmetry se- quences.The total simple solvation string number of distinct structures was 219093 excluding reflection symmetry in the self-avoiding path of length 24 triangular lattice model.Based on triangular lattice model,a fast search algorithm is presented in order to search the protein conformation space by constructing a fast search tree.The algorithm decreased the computation by computing the objective energy of tree nodes.The parallel experiments proved that the fast tree search algorithm yielded an exponential speed-up in models of size 4 5 6 5 4.To understand the search result we perform statistical analysis in designability.