Jain S, Kumar C V, Kalonia D S
School of Pharmacy, University of Connecticut, Storrs 06269-2092.
Pharm Res. 1992 Aug;9(8):990-2. doi: 10.1023/a:1015890024702.
Binding of Leu-enkephalin and the enkephalin metabolite, tyrosine-glycine-glycine (TGG), to bovine serum albumin (BSA) was studied as a model to investigate protein peptide interactions. TGG and Leu-enkephalin quench the tryptophyl fluorescence of BSA. Stern-Volmer quenching constants were typically in the range of 40 to 300 M-1, depending on the experimental conditions. The addition of Cu(II) or Ni(II) did not change the quenching constant, indicating that TGG does not compete for the metal binding sites on BSA. From fluorescence quenching studies with TGG, tyrosyl-glycine, tyrosine and glycyl-glycine, it was concluded that the presence of the tyrosine residue is required for the observed quenching. The phenolic group in tyrosine accounted for the quenching mechanism because phenol was efficient in quenching BSA fluorescence, whereas phenylalanine had no detectable effect. A large solvent isotope effect on the quenching constant of phenol and TGG with BSA strongly suggests an active role of the -OH functionality in the quenching mechanism.
以亮氨酸脑啡肽和脑啡肽代谢物酪氨酸 - 甘氨酸 - 甘氨酸（TGG）与牛血清白蛋白（BSA）的结合作为研究蛋白质 - 肽相互作用的模型。TGG和亮氨酸脑啡肽会淬灭BSA的色氨酸荧光。根据实验条件，斯特恩 - 沃尔默淬灭常数通常在40至300 M⁻¹范围内。添加Cu(II)或Ni(II)不会改变淬灭常数，这表明TGG不会竞争BSA上的金属结合位点。通过对TGG、酪氨酰甘氨酸、酪氨酸和甘氨酰甘氨酸进行荧光淬灭研究得出，观察到的淬灭需要酪氨酸残基的存在。酪氨酸中的酚基是淬灭机制的原因，因为苯酚能有效淬灭BSA荧光，而苯丙氨酸没有可检测到的影响。苯酚和TGG与BSA的淬灭常数存在较大的溶剂同位素效应，这强烈表明 -OH官能团在淬灭机制中起积极作用。
