Electronic excitation energy transfer between molecules of cyanine dyes in a complex with protein and in systems of magnetic nanoparticles with protein coatings

Electronic excitation energy transfer (EEET) between molecules of carbocyanine dyes bound noncovalently with human serum albumin (HSA) has been studied. 3,3'-Di-(gamma-sulfopropyl)-9-methylcarbocyanine betaine has been used as an electronic excitation energy donor and 3,3'-di-(gamma-sulfopropyl)-4,5,4',5'-dibenzo-9-ethylthiacarbocyanine betaine, as an acceptor dye. EEET has been studied both in samples of HSA solutions and in systems containing protein-coated magnetic nanoparticles. Stable coatings of magnetic nanoparticles, consisting of a mixture of HSA and bovine serum albumin, have been formed by the method of free radical linking of protein molecules adsorbed on the surface of the particles. The effect of HSA denaturation on the spectral and fluorescent properties of the dyes and EEET has been studied, and the data on donor fluorescence quenching by the acceptor have been obtained. It has been concluded that HSA retains its functional properties in the linked coating, thereby providing evidence for biocompatibility of the coatings obtained by free-radical oxidative protein modification.