Spectral and Fluorescent Studies of the Interaction of an Anionic Oxacarbocyanine Dye with Bovine Serum Albumin

The influence of the formation of noncovalent intermolecular complexes with bovine serum albumin (BSA) on the spectral and fluorescent properties of the anionic oxacarbocyanine dye 3,3′-di-(γ-sulfopropyl)-5,5′-diphenyl-9-ethyloxacarbocyanine betaine (OCC) was studied. Binding of OCC to BSA increased significantly the dye fluorescence. Changes in the absorption and fluorescence spectra of OCC upon interaction with BSA argued in favor of a shift of the dye cis–trans equilibrium in the complex. The effects of adding albumin-denaturing compounds (urea, sodium dodecyl sulfate) on the spectral and fluorescent properties of the dye in the OCC–BSA complex were studied. It was concluded that OCC can act as a probe for albumins and can be used to study protein denaturing.