Fluorospectrophotometric Properties of the Products of Binding Reaction Between Bovine Serum Albumin and Antibiotics of Large Ring Lactones

The binding reaction between bovine serum albumin (BSA) and large ring lactone antibiotics,taking roxithromycin (RM) and azithromycin (AM) as example,was studied by fluorospectrophotometry and UV-VIS spectrophotometry.As shown by the experimental results,either of the antibiotics were bound strongly to BSA to form compound complex with mole ratio of 1 to 1 and equilibrium constants of KRM=3.6×104L·mol-1 and KAM=7.2×104L·mol-1.The action distance,r between the donor (BSA) and the acceptors (RM,AM) and their efficiency of energy transfer (E) were found,according to the principle of Frster′s non-nonradiative energy transfer,to have the following values: rRM=0.49 nm,rAM=1.58 nm,ERM=0.738,EAM=0.779.As proved by the Stern-Volmer equation,the fluorescence quenching of BSA caused by RM (or AM) was a static quenching process due to the binding reaction between BSA and RM (or AM).