Suzukida M, Le H P, Shahid F, McPherson R A, Birnbaum E R, Darnall D W
Biochemistry. 1983 May 10;22(10):2415-20. doi: 10.1021/bi00279a017.
The single cysteine residue (Cys-34) of human serum albumin was modified with the organic mercurial [4-[p-(dimethylamino)phenyl]azo]phenyl]mercuric acetate. Introduction of this chromophore into the protein results in the quenching of the protein tryptophan fluorescence spectrum due to energy transfer from the tryptophan residue to the mercurial. Since human albumin contains only a single tryptophan, it was then possible to calculate distances between the mercurial bound at Cys-34 and Trp-214 under various conditions. This distance contracted during the course of the N leads to F transition, being 34-35 A in the N conformation (pH 6-7.5) and 29.9 A in the F conformation (pH 3.6). The distance increased substantially during the course of the F leads to E transition occurring between pH 3.6 and pH 1.9 and was found to be nearly 37 A at pH 1.9. The distance between Cys-34 and Trp-214 was found to undergo a slight contraction during the N leads to B transition occurring between pH 7.0 and pH 9.0. At pH 8.5-9 where the protein is predominately in the B form, the distance was found to be slightly more than 31 A.
人血清白蛋白的单个半胱氨酸残基（Cys-34）用有机汞化合物[4-[对-(二甲基氨基)苯基]偶氮]苯基]醋酸汞进行修饰。将这种发色团引入蛋白质会导致蛋白质色氨酸荧光光谱猝灭，这是由于能量从色氨酸残基转移到汞化合物上。由于人白蛋白仅含有一个色氨酸，因此在各种条件下都能够计算结合在Cys-34处的汞化合物与Trp-214之间的距离。在N向F转变过程中，该距离缩短，在N构象（pH 6 - 7.5）中为34 - 35 Å，在F构象（pH 3.6）中为29.9 Å。在pH 3.6和pH 1.9之间发生的F向E转变过程中，该距离大幅增加，在pH 1.9时发现接近37 Å。在pH 7.0和pH 9.0之间发生的N向B转变过程中，发现Cys-34与Trp-214之间的距离略有缩短。在蛋白质主要为B形式的pH 8.5 - 9时，发现该距离略大于31 Å。
