Tetracycline hydrochloride binds with high affinity to warfarin site (site-I)on Bovine serum Albumin: Temperature and pH influence the binding process

The interaction of tetracycline hydrochloride to Bovine Serum Albumin (BSA)at various temperatures and pH values using Equilibrium Dialysis (ED) methodwas studied. Scatchard analysis of the binding data revealed the presence of onehigh affinity binding site with k2 value of 1.67x106 M-1 and six low affinitybinding sites with k2 value of 1.44x105 M-1 at pH 7.4 and 25 degree C. Site-specific probe displacement data suggested that warfarin site (site-I) is the highaffinity binding site and benzodiazepine site (site-II) is the low affinity bindingsite on BSA for this drug. The high affinity binding site was found to beaffected by temperature and pH of the medium. The thermodynamic data indicatedthat the binding process of tetracycline hydrochloride to BSA is spontaneous,exothermic and entropically driven. Electrostatic forces, hydrogen bonding,hydrophobic interactions and van der Waals forces are probably involved in theoverall binding process of tetracycline hydrochloride to BSA. The affinity of thisdrug to BSA is dependent on the conformational changes of BSA caused by N-Btransition.