Study of the noncovalent interaction of squarylium dyes with serum albumins

Abstract

The noncovalent interaction of zwitterionic indolium squarylium dyes (hydrophilic and hydrophobic) and a structurally analogous ionic indodicarbocyanine (hydrophilic) dye with serum albumins was studied by spectral and fluorescent methods. It has been found that the hydrophilic squarylium dye with sulfonate groups most efficiently interacts with albumins, which is probably due to the double negative charge of the dye molecule at the expense of the sulfonate groups and the possibility to form hydrogen bonds with albumin. The hydrophobic squarylium dye, as well as the hydrophilic indodicarbocyanine dye without the squarylium fragment in its structure, bind with albumins much weaker than the structurally relevant hydro- philic squarylium dye. The properties of the latter dye permit us to recommend it for using as a spectral and fluorescent probe for serum albumins in extracellular media of living organisms.