利用8-苯氨基-1-萘磺酸(ANS)荧光探针法，测定了牛血清白蛋白(BSA)与牛免疫球蛋白(bIgG)的表面疏水性，探讨了pH、温度、添加盐、十二烷基磺酸钠(SDS)、盐酸胍和辛酸钠(NaCA)对蛋白表面疏水性指数S0的影响。实验表明，对于阴离子型荧光探针ANS，pH对S0测定的影响显著，选择pH略高于蛋白等电点比较合适。温度对两种蛋白S0的影响不同，从50℃升至80℃，BSA表面疏水性降低，bIgG表面疏水性升高。添加盐促使蛋白的表面疏水性增强，相比 BSA，bIgG 增加幅度较大。不同变性剂对两种蛋白 S0的影响也不同，与变性机制、蛋白疏水特性及分子结构有关。添加NaCA对两种蛋白S0影响存在显著差异，随着NaCA浓度升高，BSA的S0值减小，而bIgG则维持基本不变，这与疏水层析分离过程的NaCA影响相一致。结果表明，ANS荧光探针法可用于考察不同溶液条件对蛋白质分子表面疏水性的影响，研究特定添加剂-蛋白质间疏水相互作用。%The surface hydrophobicities of bovine serum albumin (BSA) and bovine immunoglobulin G (bIgG) were studied by a fluorescence method with 8-anilino-1-naphthalene sulfonate (ANS) as the probe. Effects of factors including pH, temperature and additives on the surface hydrophobicity indexes (S0) were investigated. The results show that pH can significantly affect the determination of S0, as ANS is an anionic fluorescent probe. Solution pH slightly higher than isoelectric point of proteins is suitable. Temperature has different effects on S0 of BSA and bIgG. S0 of BSA decreases from 50℃ to 80℃, while that of bIgG increases. Salt addition could enhance the surface hydrophobicity of both proteins, and bIgG has much greater variation than that of BSA. Depending on the denaturation mechanisms, surface hydrophobic properties and molecular structure of proteins, the denaturants have different impacts on S0 of the two proteins. With the increase of sodium caprylate (NaCA) concentration, S0 of BSA declines and that of bIgG remaines unchanges. This result is consistent with the impacts of NaCA on the separation of BSA and bIgG in hydrophobic interaction chromatography. This study demonstrates that the ANS fluorescence probe method can be used to investigate the effects of liquid conditions on protein surface hydrophobicity and study the hydrophobic interactions between specific additives and proteins.
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