Fluorometric study of tetracycline-bovine serum albumin interaction

The interaction of four tetracyclines (tetracycline, oxytetracycline, chlortetracycline and methacycline) with bovine serum albumin is studied fluorometrically. It is demonstrated that these tetracyclines exhibit the main features of fluorescent probes; increase of their fluorescence and quantum yield both in mixtures with bovine serum albumin and in non-polar, organic solvents, accompanied by blue shift of fluorescence emission maximum. The thermodynamic values ΔH and ΔS of the reaction of binding of tetracyclines to bovine serum albumin have been determined fluorometrically. The results reveal that the binding of tetracyclines to bovine serum albumin is due mainly to non-polar (hydrophobic) interactions. It has been found that the divalent metal ions are not involved in the binding of tetracyclines to bovine serum albumin at least at pH 10·5.