Thermodynamic Analysis of Protein Stability

Understanding how tertiary structures of proteins are coded for in their amino acid sequences is onethe main targets in modern life science research. However，这一目标未被确定。其中一个答案是一种保护性结构是预先确定的不只是一个部分的amino acid sequence，但也有一个extensive interaction In fact，the same kinds of substitutions give different changes in conformational stability. These resultsshow that the effect of a single amino acid substitution on protein stability depends on thelocation of the mutation site及其环境in the protein structure. in order to estimate thecontribution of each factor to protein稳定性the data of structure and stability changes must be expanded by studying many mutant proteins with with系统和comprehensive substitutions. In这个项目，we tried to estimate some factors that conformational stability of a protein using数据基础of stability/structure，其中包括来自不同人类lysozymes系列的数据。我们将超过100个不同的人类lysozymes.改变stabilities and structures due tomutations were evaluated by DSC and X-ray analysis，respectively. Using database of structure and stability changes due to mutationswhich are obtained in this project, the magnitude of hydrophobicity of carbon atom (C)and the hydrophobicity of nitrogen and neutral oxygen atoms （N/O）可能估计to be 0.178kJ/mol/ A维D12维D1， and -0.013 kJ/mol/ A维D12维D1，respectively. The net contribution of an intramolecular hydrogen bond，an intermolecular one between protein and ordered water moleculesand an intermolecular one between ordered water molecules was estimated to be 8.5, 5.2and 5.0 kJ/mol, respectively，for a hydrogen bond with 3a length. The entropic cost due to The introduction of a water moleculecould be also estimated to be about 8 kJ/mol。

Understanding how tertiary structures of proteins are coded for in their amino acid sequences is one of the main targets in modern life science research. However, this goal has not yet been achieved. One of the reasons is that a protein structure is prescribed not only by a part of the amino acid sequence but also by an extensive interaction. In fact, the same kinds of substitutions give different changes in conformational stability. These results show that the effect of a single amino acid substitution on protein stability depends on the location of the mutation site and its environment in the protein structure. In order to estimate the contribution of each factor to protein stability, the data of structure and stability changes must be expanded by studying many mutant proteins with systematic and comprehensive substitutions. In this project, we tried to estimate some factors that contribute to conformational stability of a protein using data base of stability/structure, which are obtained from a series of mutant human lysozymes. Then, we constructed more than 100 mutant human lysozymes. Changes in stabilities and structures due to mutations were evaluated by DSC and X-ray analysis, respectively. Using database of structure and stability changes due to mutations, which are obtained in this project, the magnitude of hydrophobicity of carbon atom (C), and the hydrophobicity of nitrogen and neutral oxygen atoms (N/O) could be estimated to be 0.178 kJ/mol/ÅィイD12ィエD1, and -0.013 kJ/mol/ÅィイD12ィエD1, respectively. The net contribution of an intramolecular hydrogen bond, an intermolecular one between protein and ordered water molecules, and an intermolecular one between ordered water molecules was estimated to be 8.5, 5.2, and 5.0 kJ/mol, respectively, for a hydrogen bond with 3 Å length. The entropic cost due to the introduction of a water molecule could be also estimated to be about 8 kJ/mol.