The fine absorption bands of three aromatic amino acid residues, Tryptophan (Trp), Tyrosine (Tyr), and Phenylalanine (Phe), of bovine serum albumin (BSA) were studied by ultraviolet second derivative spectroscopy. The conformation transitions of BSA at pH 2.3-12 were analyzed along with the absorption spectrum of the peptide bonds. It is observed that there exist obvious conformation transitions around the isoelectric point ( pH 4.7) of BSA. The transitions are subtle between pH 5.7 and pH 10 but distinct in strong acidity( pH 2.3 ) and alkaline( pH 12) environments. Meanwhile,the concentration of BSA has certain effect on the conformation transition.%采用二阶导数紫外光谱,研究了牛血清蛋白(BSA)中色氨酸(Trp)、酪氨酸(Tyr)和苯丙氨酸(Phe)3种芳香族氨基酸残基的精细吸收谱带,并结合其肽键的吸收谱带综合分析了BSA pH值在2.3～12区间的构象变化.研究结果表明,BSA在等电点(pH值4.7)附近时构象变化较大;而在pH值5.7-10区间,构象变化较小;在强酸(pH值2.3)和强碱(pH值12)环境中,BSA构象变化非常明显.同时还发现,BSA质量浓度也在一定程度上影响其构象.
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