THERMAL-STABILITY OF PROTEINS IN THE PRESENCE OF POLY(ETHYLENE GLYCOLS)
THERMAL-STABILITY OF PROTEINS IN THE PRESENCE OF POLY(ETHYLENE GLYCOLS)
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DOI：
10.1021/bi00398a042
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发表时间：
1987-12-01
期刊：
影响因子：
2.9
通讯作者：
LEE, JC
中科院分区：
文献类型：
--
作者：
LEE, LLY;LEE, JC
摘要：研究了核糖核酸酶、溶菌酶、凝乳酶原和/3-乳球蛋白在聚乙二醇存在或不存在时的热去折叠。用非线性最小二乘法将展开曲线拟合为二态模型，得到了AH、As和熔融温度Tm的值。在聚乙二醇的存在下，观察到所有研究的蛋白质体系的热转变温度都降低了。这种下降的幅度取决于所使用的特定蛋白质和聚乙二醇的分子大小。转变温度下降的幅度与这些蛋白质的平均疏水性之间可以建立线性关系；也就是说，最大的可观察到的下降与疏水性最高的蛋白质有关。进一步分析热去折叠数据表明，聚乙二醇组分对所有研究蛋白质的去折叠AH0与温度的关系有显著影响。对于/3-乳球蛋白，AH-Tm的曲线图表明斜率从负值变为正值，从而意味着聚乙二醇的存在导致ACP在热展开过程中发生变化。溶剂-蛋白质相互作用的研究结果表明，在高温下，聚乙二醇1000优先与蛋白质的变性状态相互作用，但在低温下被排除在天然状态之外。这些观察结果与以下事实相一致，即聚乙二醇本质上是疏水的，并且在展开时会与暴露的疏水侧链发生良好的相互作用，从而导致热转变温度降低。
Revised Manuscript Received July 10, 1987 abstract: Thermal unfolding of ribonuclease, lysozyme, chymotrypsinogen, and/3-lactoglobulin was studied in the absence or presence of poly (ethylene glycols). The unfolding curves were fitted to a two-state model by a nonlinear least-squares program to obtain values of AH, AS, and the melting temperature Tm. A decrease in thermal transition temperature was observed in the presence of poly (ethylene glycol) for all of the protein systems studied. The magnitude of such a decrease depends on the particular protein and the molecular size of poly (ethylene glycol) employed. A linear relation can be established between the magnitude of the decrease in transition temperature and the average hydrophobicity of these proteins; namely, thelargest observable decrease is associated with the protein of the highest hydrophobicity. Further analysis of the thermal unfolding datareveals that poly (ethylene glycols) significantly effect the relation between AH0 of unfolding and temperature for all theproteins studied. For/3-lactoglobulin, a plot of AH versus Tm indicates a change in slope from a negative to a positive value, thus implying a change in ACp in thermal unfolding caused by the presence of poly (ethylene glycols). Results from solvent-protein interaction studies indicate that at high temperature poly (ethylene glycol) 1000 preferentially interacts with the denatured state of protein but is excluded from the native state at low temperature. These observations are consistent with the fact that poly (ethylene glycols) are hydrophobic in nature and will interactfavorably with the hydrophobic side chains exposed upon unfolding; thus, it leads to a lowering of thermal transition temperature.