1989 年 37 巻 4 号 p. 1009-1012
A fluorescent probe applicable to protein binding measurement was developed. Several 2-phenylbenzotriazolyl-5-amine derivatives having an amino group on the 2-phenyl ring were synthesized. Their fluorescence characteristics and the binding affinity to α1-acid glycoprotein (α1-AGP)were investigated. They were practically non-fluorescent in aqueous solution, but were highly fluorescent in the presence of α1-AGP. This fluorescence was due to the binding of these compounds to α1-AGP. Of all the compounds synthesized, 7-chloro-2-(p-diethylaminophenyl)-2H-benzotriazolyl-5-amine (CDBA) bound to α1-AGP most strongly and was used as a fluorescent probe. The binding parameters of CDBA were estimated by the fluorometric titration method to be log K=6.18 and n=0.40. The fluorescence of CDBA in the α1-AGP solution was markedly quenched in the presence of basic drugs, indicating that these drugs competitively displace CDBA bound to α1-AGP. The binding constants of the basic drugs were calculated, based on the decrease of fluorescence intensity in the presence of the drug. The binding strength of the drugs tested ranged from 4.7 to 6.8 as log K value.
