7-Alkylaminocoumarin-4-acetic acids as fluorescent probe for studies of drug-binding sites on human serum albumin.
作者:Mitsuru IRIKURA、Akira TAKADATE、Shujiro GOYA、Masaki OTAGIRI
DOI:10.1248/cpb.39.724
日期:——
7-Alkylaminocoumarin-4-acetic acids I-IX having alkylamino groups different in alkylchain length were synthesized as fluorescence probes for characterization of drug-binding sites on human serum albumin (HSA). The fluorescences of I-IX were quenched or enhanced in the presence of HSA with shifts of the emission maxima to shorter wavelength. The binding constants and the number of binding sites were determined by the spectral changes of the probes I-IX bound to HSA through analysis of Scatchard's and Job's plots. The primary binding sites of the tested probes were found to be site 2 (diazepam site) on HSA from the results of competitive displacement studies. The polarity of site 2 was estimated from the relationship between the emission maximum of the probe of IV and Z-values, and was found to be comparable to that of acetonitrile. Simple attempts to estimate the site 2 region from the molecular size of the probe of VIII obtained using the Corey-Pauling-Koltun molecular model suggest that the hydrophobic cleft at site 2 is about 21-25 Å in depth. The distance between the lone tryptophan residue in HSA and probes bound to site 2 was estimated to be 15-17 Å using Forster's equation on the basis of fluorescence energy transfer. The present data suggest that I-IX are useful as fluorescence probes for the characterization of site 2 on HSA.
合成了9种具有不同烷基链长度的7-烷基氨基香豆酸-4-乙酸(I-IX),作为人血清白蛋白(HSA)药物结合位点特征化的荧光探针。在HSA存在下,I-IX的荧光被猝灭或增强,发射最大值向短波长移动。通过分析Scatchard和Job图,确定了与HSA结合的探针I-IX的结合常数和结合位点数量。竞争位移研究的结果表明,测试的探针的主要结合位点为HSA的位点2(地西泮位点)。利用探针IV的发射最大值与Z值之间的关系估算了位点2的极性,发现其与乙腈的极性相当。根据使用Corey-Pauling-Koltun分子模型获得的探针VIII的分子大小,简单尝试估算位点2区域,表明位点2的疏水裂缝深度约为21-25 Å。结合福斯特公式,基于荧光能量转移,估算HSA中孤立的色氨酸残基与结合在位点2的探针之间的距离为15-17 Å。目前的数据表明,I-IX作为荧光探针用于HSA位点2的特征化是有用的。