The binding of thioguanine (6-TG) to bovine serum albumin was studied using the technique of microdialysis combined with spectrofluorimetric analysis. In the presence of NaOH (1.0 * 10~(-3) mol·L~(-1)), 6-TG can be oxidized by KMnO_4 (5.0 * 10~(-6)mol·L~(-1)) to 2-amino-6-guanine-sulfate acid, which produces higher fluorescence emission. The fluorescence was measured at 406 nm with excitation at 329 nm. The calibration curve was linear over the concentration range of 2.0 * 10~(-11) ～ 2.0 * 10~(-6)mol·L~(-1) for 6-TG with a detection limit of 4.0 * 10~(-12)mol·L~(-1). The microdialysis probe was utilized to sample the mixed solution at a perfusion rate of 5 μL ·min~(-1) and the recovery of 6-TG under experimental condition was (7. 2 ± 0.2)%. The data obtained by the present microdialysis fluorimetric method was analyzed with the Scathard analysis plot. The estimated association constant (K) and the number of the binding sites (n) on one of BSA were 1.02 * 10~(-4) (mol·L~(-1))~(-1) and 1.63 (Scatchard equation), respectively.

Key words: FLUOROSPECTROPHOTOMETRY, thioguanine, BOVINE SERUM ALBUMIN