Determination on the binding of chlortetracycline to bovine serum albumin using spectroscopic methods

In this work, the interaction of chlortetracycline with bovine serum albumin (BSA) was investigated by fluorescence spectroscopy, circular dichroism (CD) spectroscopy, and molecular docking. Results indicated that chlortetracycline quenches BSA fluorescence mainly by a static quenching mechanism. The quenching constants (K(SV) ) were obtained as 5.64 × 10(4) , 4.49 × 10(4) , and 3.44 × 10(4/) M(-1) at 283, 295, and 307 K, respectively. The thermodynamic parameters of enthalpy change Δ H°, entropy change Δ S°, and free energy change Δ G° were -5.12 × 10(4/) J mol(-1), -97.6 J mol(-1) K(-1), and -2.24 × 10(4/) J mol(-1) (295 K), respectively. The association constant (K(A) ) and the number of binding sites (n) were 9.41 × 10(3) M(-1) and 0.86, respectively. The analysis results suggested that the interaction was spontaneous, and van der Waals force and hydrogen-bonding interactions played key roles in the reaction process. In addition, CD spectra proved secondary structure alteration of BSA in the presence of chlortetracycline.