Interactions of photosensitized tetracycline with serum albumin

Interactions of tetracycline with bovine serum albumin (BSA) were studied b y fluorescence quenching and circular dichroism (CD) analysis. The binding isotherm exhibited at least 13 tetracycline binding sites on the albumin mo lecule. Amongst these, four were found to be high affinity sites and the re mainder were loose sites. The Scatchard analysis demonstrated the binding c onstant and capacity of BSA to be 4.6 x 10(6) liters/mole and 3.6, respecti vely. The CD data revealed a significant decrease in the mean residue ellip ticity (MRE), indicating alterations in the protein helicity. A reduction o f 20% in the alpha - helical content of the albumin was noted at higher lev els of tetracycline in the presence of Cu (II) ions. Thus the strong in vit ro interactions of tetracycline with albumin resulted in conformational cha nges in its globular structure and insinuate potential health risk due to p ossible macromolecular damage, under physiological conditions, from the for mation of tetracycline/Cu(II) complexes.