We investigated quantum-chemical characteristics of gemcitabine (GEM), fluorescence quenching of bovine serum albumin (BSA) in aqueous solutions with the presence of GEM. The static mechanism of the complex formation with moderate binding constant K-A (similar to 4 x 10(5)M(-1)) and number of binding sites n approximate to 1.5 was established to take place in the solutions. Studying the energy transfer efficiency we found that molecules of GEM are localized near polar charged amino acid residues of the protein biomolecules at the average distance r = 2.91nm, R-0 = 2.45nm: The calculated thermodynamic parameters demonstrate the presence of both hydrogen bonds and hydrophobic interaction between the protein and ligand molecules.