HEAT-CAPACITY AND CONFORMATION OF PROTEINS IN THE DENATURED STATE
HEAT-CAPACITY AND CONFORMATION OF PROTEINS IN THE DENATURED STATE
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DOI：
10.1016/0022-2836(89)90318-5
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发表时间：
1989-02-20
影响因子：
5.6
通讯作者：
KHECHINASHVILI, NN
中科院分区：
文献类型：
--
作者：
PRIVALOV, PL;TIKTOPULO, EI;KHECHINASHVILI, NN
多种球状蛋白（胰腺核糖核酸酶 A、葡萄球菌核酸酶、鸡蛋清溶菌酶、肌红蛋白和细胞色素 c）和纤维状蛋白（胶原蛋白）在各种状态（天然、变性、有或没有二硫键交联或血红素）下的热容量、特性粘度和椭圆度已在较宽的温度范围内进行了实验研究。结果表明，变性蛋白质的部分热容显着超过天然蛋白质的热容，特别是在球状蛋白质的情况下，并且接近根据单个氨基酸残基的已知热容计算出的延伸多肽链的值。一些球状蛋白质（例如肌红蛋白和溶菌酶）在中性 pH 下的变性状态下在室温下出现的显着残留结构导致热容略有下降，这可能是由于从水中部分筛选了蛋白质非极性基团。展开状态的热容渐近增加，在约100℃时接近恒定值。天然状态的热容的温度依赖性可以在比变性状态短得多的温度范围内确定，并且相应地不太确定，在高达 80°C 时似乎是线性的。因此，变性热容增量似乎与温度有关，并且可能在约 140°C 时降至零。 C.
Heat capacity, intrinsic viscosity and ellipticity of a number of globular proteins (pancreatic ribonuclease A, staphylococcal nuclease, hen egg-white lysozyme, myoglobin and cytochrome c) and a fibrillar protein (collagen) in various states (native, denatured, with and without disulfide crosslinks or a heme) have been studied experimentally over a broad range of temperatures. It is shown that the partial heat capacity of denatured protein significantly exceeds the heat capacity of native protein, especially in the case of globular proteins, and is close to the value calculated for an extended polypeptide chain from the known heat capacities of individual amino acid residues. The significant residual structure that appears at room temperature in the denatured states of some globular proteins (e.g. myoglobin and lysozyme) at neutral pH results in a slight decrease of the heat capacity, probably due to partial screening of the protein non-polar groups from water. The heat capacity of the unfolded state increases asymptotically, approaching a constant value at about 100.degree. C. The temperature dependence of the heat capacity of the native state, which can be determined over a much shorter range of temperature than that of the denatured state and, correspondingly, is less certain, appears to be linear up to 80.degree. C. Therefore, the denaturational heat capacity increment seems to be temperature-dependent and is likely to decrease to zero at about 140.degree. C.