Novel two-color fluorescence probe with extreme specificity to bovine serum albumin.

We report on strong, highly specific and stochiometric binding to bovine serum albumin of novel fluorescence probe FA, 2-(6-diethylaminobenzo[b]furan-2-yl)-3-hydroxychromone, that exhibits a very characteristic two-band fluorescence spectrum. Both absorption band and two fluorescence bands of FA are very sensitive to non-covalent interactions in the immediate environment of the probe. Multiparametric analysis of this spectroscopic information allows us to conclude that the binding site is characterized by very low polarity, high extent of screening from aqueous environment and unusually high electronic polarizability. The latter suggests the proximal location of probe FA to the aromatic amino acid residues in the binding site. The new probe can be proposed for the study of interaction of ligands and drugs of different nature with serum albumins.