Investigation of the Binding Between Pepsin and Nucleoside Analogs by Spectroscopy and Molecular Simulation

In this paper, the interactions of pepsin with CYD (cytidine) or nucleoside analogs, including FNC (2′-deoxy-2′-β-fluoro-4′-azidocytidine) and CMP (cytidine monophosphate), were investigated by fluorescence, UV–visible absorption and synchronous fluorescence spectroscopy under mimic physiological conditions. The results indicated that FNC (CYD/CMP) caused the fluorescence quenching by the formation of complex. The binding constants and thermo-dynamic parameters at three different temperatures were obtained. The hydrophobic and electrostatic interactions were the predominant intermolecular forces to stabilize the complex. The F atom in FNC might weaken the binding of nucleoside analog to pepsin. Results showed that CYD was the strongest quencher and bound to pepsin with higher affinity.