The quantum yield and binding to bovine serum albumin (BSA) were investigated with various fluorescent 7-alkylamino (bearing 2-12 carbon atoms), 7-benzylamino, and 7-p-methoxybenzyl-amino derivatives of 4-nitrobenzoxadiazole (NBD). Among them, alkylamino derivatives gave high quantum yield in both ethanol and BSA solution, and greater affinity to BSA was found with those having a longer alkyl chain. In particular, those with C8-C12 alkyl chains may be useful in research on hydrophobic regions as fluorescent probes. In the binding of these probes to BSA, the logarithm of the primary association constant increased linearly with increase in the length of the side chain; a hydrophobic cleft similar to that on the human serum albumin molecule was suggested to exist also on the BSA molecule. In the investigation of the binding displacement of 7-amino-NBD derivatives based on Sudlow's classification, almost no displacement was observed with site II drugs, ibuprofen and flufenamic acid. However, diazepam (a site II drug) showed different behavior from other site II drugs. It was particularly interesting that the difference of the displacing behavior between diazepam and other site II drugs increases with increase of the side chain length of the alkylamino-NBD probes.
研究了量子产率和与
牛血清白蛋白(
BSA)的结合情况,采用了各种荧光的7-烷基
氨基(含有2-12个碳原子)、7-苯基
氨基和7-对
甲氧基苯基
氨基衍
生物的4-
硝基苯并噁二唑(NBD)。其中,烷基
氨基衍
生物在
乙醇和
BSA溶液中均表现出较高的量子产率,且具有较长烷基链的衍
生物与
BSA有更强的亲和力。特别是C8-C12烷基链的衍
生物在研究疏
水区域作为荧光探针时可能会很有用。在这些探针与
BSA结合的过程中,主要结合常数的对数与侧链长度的增加呈线性关系;推测
BSA分子上也存在类似于人
血清白蛋白分子上的疏
水裂缝。根据Sudlow分类法对7-
氨基-NBD衍
生物的结合置换进行研究时,几乎没有观察到与II位点药物如
布洛芬和
氟芬那酸的置换。然而,
地西泮(一个II位点药物)的行为与其他II位点药物不同。特别有趣的是,
地西泮与其他II位点药物之间的置换行为差异随着烷基
氨基-NBD探针侧链长度的增加而增加。