Insight into the fluorescence quenching of Trp214 at HSA by the Dimetridazole ligand from simulation

Spectroscopy is an important tool for detecting drug binding to amino acid sequences. One such important spectroscopic process is the fluorescence quenching due to charge transfer (CT) processes between a drug molecule and the chromophore center of Human Serum Albumin (HSA). We present a theoretical investigation of the CT occurring upon electronic excitation when a dimetridazole (Dmz) molecule incorporated in HSA interacts with tryptophan residue (Trp214). Structures of the donor–acceptor complexes were optimized using density-functional theory in vacuum as well as extracted from molecular dynamics (MD) trajectories of the Dmz and Trp214 complexes in HSA (Dmz&Trp214@HSA). Absorption, emission, and fluorescence quenching of the Trp214&Dmz complex in a large number of MD conformers were calculated using various quantum-mechanical approaches in order to generate statistical spectra that are then used for studying the CT between the non-bonded donor and the acceptor