Damodaran S
Department of Food Science, University of Wisconsin-Madison, WI 53706.
Int J Biol Macromol. 1989 Feb;11(1):2-8. doi: 10.1016/0141-8130(89)90030-5.
The thermostability of serum albumin and beta-lactoglobulin in various salt solutions was studied using differential scanning calorimetry. Below 1.0 M salt concentrations, the relative effectiveness of various sodium salts on increasing the thermostability of beta-lactoglobulin followed the classic Hofmeister or lyotropic series, i.e. SO2-(4) greater than Cl- greater than Br- greater than ClO-4 greater than SCN-; however, in the case of serum albumin the above order was reversed, i.e. ClO-4 greater than SCN- greater than Br- greater than Cl- greater than SO2-(4), indicating that the thermostability of serum albumin was higher in chaotropic solution conditions. Circular dichroic analysis of serum albumin in NaClO4 solutions revealed that the alpha-helical content of the protein increased from 59% to 73% in 1.0 M NaClO4; no similar increase in secondary structure was observed for beta-lactoglobulin. These observations contradicted the general notion that the chaotropic effect of neutral salts on the stability of macromolecules is independent of any details of the macromolecular conformation itself. The results presented here indicate that the predisposition of the native conformation of a protein per se might affect whether the protein would undergo stabilization or destabilization (i.e. conformational adaptability) under moderate chaotropic solution conditions.
使用差示扫描量热法研究了血清白蛋白和β-乳球蛋白在各种盐溶液中的热稳定性。在盐浓度低于1.0 M时，各种钠盐提高β-乳球蛋白热稳定性的相对有效性遵循经典的霍夫迈斯特或离子促溶序列，即SO₂⁻₄＞Cl⁻＞Br⁻＞ClO₄⁻＞SCN⁻；然而，对于血清白蛋白，上述顺序相反，即ClO₄⁻＞SCN⁻＞Br⁻＞Cl⁻＞SO₂⁻₄，这表明血清白蛋白在离液剂溶液条件下热稳定性更高。对高氯酸钠溶液中的血清白蛋白进行圆二色性分析表明，在1.0 M高氯酸钠中，该蛋白质的α-螺旋含量从59%增加到73%；未观察到β-乳球蛋白的二级结构有类似增加。这些观察结果与中性盐对大分子稳定性的离液效应与大分子构象本身的任何细节无关这一普遍观点相矛盾。此处给出的结果表明，蛋白质本身天然构象的倾向可能会影响该蛋白质在适度离液剂溶液条件下是会发生稳定化还是去稳定化（即构象适应性）。
