葡萄球菌核酸酶的冷变性
Cold denaturation of staphylococcal nuclease.
作者信息
Griko Y V, Privalov P L, Sturtevant J M
机构信息
Institute of Protein Research, Academy of Sciences of the Union of Soviet Socialist Republics, Pushchino, Moscow Region.
出版信息
Proc Natl Acad Sci U S A. 1988 May;85(10):3343-7. doi: 10.1073/pnas.85.10.3343.
Denaturation of staphylococcal nuclease was studied in a temperature range from -7 to 70 degrees C by scanning microcalorimetry and spectropolarimetry. It was found that the native protein is maximally stable at about 20 degrees C and is denatured upon heating and cooling from this temperature. The heat and cold denaturation processes are approximated rather well by a two-state transition showing that the molecule is composed of a single cooperative system. The main difference between these two processes is in the sign of the enthalpy and entropy of denaturation: whereas the heat denaturation proceeds with increases in the enthalpy and entropy, the cold denaturation proceeds with decreases in both quantities. The inversion of the enthalpy sign occurs at about 15 degrees C in an acetate buffer, but this temperature can be raised by addition of urea to the solvent.
通过扫描量热法和旋光光谱法，在-7至70摄氏度的温度范围内研究了葡萄球菌核酸酶的变性。结果发现，天然蛋白质在约20摄氏度时最稳定，从该温度加热和冷却时会发生变性。热变性和冷变性过程通过两态转变能得到较好的近似，表明该分子由单一协同体系组成。这两个过程的主要区别在于变性焓和熵的符号：热变性时焓和熵增加，而冷变性时两者均减少。在醋酸盐缓冲液中，焓符号的反转发生在约15摄氏度，但通过向溶剂中添加尿素可以提高这个温度。
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