Fluorescence-Controlled Interaction of Human Serum Albumin with 4H-Furo[3,2-c]chromene-3,4(2H)-dione Derivatives

Noncovalent labeling of proteins with fluorescent dyes provides an interesting tool for bioanalytical studies without significant influence on the protein structure. The present research aims to study the interactions of 2,3-dihydrofuro[3,2-c]chromene-3,4(2H)-dione derivatives with human serum albumin (HSA) by electronic absorption and fluorescence spectroscopy. The fluorescence quantum yields and binding constants for the interactions of 2,3-dihydrofuro[3,2-c]chromene-3,4(2H)-dione derivatives with HSA at different pH values and temperatures were determined in both buffer solutions and solutions in chloroform and DMSO. Molecular docking was applied to identify the amino acid residues of HSA involved in interactions with the studied compounds, which increase the fluorescence intensity. The fluorescence intensity increased more than 314 times for (Z)-2-[4-(dimethylamino)benzylidene]-4H-furo[3,2-c]chromene-3,4(2H)-dione (3b), but the protein fluores­cence was quenched. Thus, compound 3b can be used as a noncovalent fluorescent marker for HSA with high emission intensity at low concentration.