Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.
Int J Biol Macromol. 2012 Jun 1;50(5):1286-91. doi: 10.1016/j.ijbiomac.2012.03.014. Epub 2012 Mar 30.
Differential precipitation of human plasma by ethanol is one of the most important processes for purifying therapeutic proteins, including human serum albumin. Better understanding of the effects of ethanol on the structure and stability of proteins is critical for effective and safe application of ethanol-induced protein precipitation. Here, we examined the effects of ethanol on the structure and solubility of bovine serum albumin (BSA) and SH-modified BSA. Ethanol caused BSA denaturation in a bimodal fashion, i.e., reduction of α-helix at low concentration and subsequent induction of the α-helical structure at higher concentration. In contrast, the solubility of BSA decreased monotonically. The secondary structure of SH-modified BSA was different from that of native BSA. Ethanol resulted in enhanced secondary structures of SH-modified BSA and decreased solubility monotonically. These results suggest the favorable interaction of ethanol with hydrophobic residues, leading to protein denaturation, but the unfavorable interaction with charged residues, leading to a reduction of protein solubility.
乙醇对人血浆的差异沉淀是纯化治疗性蛋白质（包括人血清白蛋白）的最重要过程之一。更好地了解乙醇对蛋白质结构和稳定性的影响对于有效和安全地应用乙醇诱导的蛋白质沉淀至关重要。在这里，我们研究了乙醇对牛血清白蛋白（BSA）和 SH 修饰的 BSA 结构和溶解度的影响。乙醇以双峰模式引起 BSA 变性，即在低浓度下减少α-螺旋，随后在较高浓度下诱导α-螺旋结构。相比之下，BSA 的溶解度呈单调下降。SH 修饰的 BSA 的二级结构与天然 BSA 的二级结构不同。乙醇导致 SH 修饰的 BSA 的二级结构增强，溶解度单调下降。这些结果表明乙醇与疏水性残基的有利相互作用导致蛋白质变性，但与带电残基的不利相互作用导致蛋白质溶解度降低。
