Interactions of tetracyclines with ovalbumin, the main allergen protein from egg white: Spectroscopic and electrophoretic studies.

The interactions of tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC) with ovalbumin (OVA), the main allergen protein of egg white, were investigated by molecular spectroscopy and electrophoresis at three pH conditions (1.5, 4.6 and 7.4). Molecular and synchronous fluorescence, UV-vis spectroscopy, electrophoresis and 1 H NMR were used to study the interaction process. Tetracyclines interact with ovalbumin fluorescence by a static quenching mechanism with non-fluorescent complex formation changing the native protein structure. The binding constant (Kb ) ranged from 2.11×104 to 58.4×104 Lmol-1 , and corresponding thermodynamic parameters were measured at different temperatures and pH values. The binding process was spontaneous (ΔG<0), and the magnitude of the interaction increased in the following order: TC<CTC<OTC. Hydrogen, electrostatic, and Van der Waals forces played a major role in stabilizing the complex. The distances between the donor (protein) and receptors (TC, OTC and CTC) were determined by FRET and varied of 2.95-3.52nm. Fe(III) and Zn(II) ions increase the affinities of TC and CTC for OVA, while OTC did not suffer a significant influence by the competitor metallic species evaluated.