Spectroscopic studies of the interaction between alprazolam and apo-human serum transferrin as a drug carrier protein

The interaction between apo-human serum transferrin (Apo-hTf) and alprazolam was investigated using various spectroscopic techniques. The drug quenched the fluorescence intensity of Apo-hTf and the mechanism behind the quenching was static. The thermodynamic parameters (ΔG, ΔH, and ΔS) that obtained from tryptophan fluorescence study revealed that the interactions between alprazolam and Apo-hTf were spontaneous. Collectively, hydrophobic interactions and hydrogen bonding most likely played major roles in Apo-hTf/alprazolam interactions. Also, the absorption spectra of Apo-hTf increased in the presence of increasing concentration of alprazolam, reflecting Apo-hTf structural alteration after drug's binding. The CD results demonstrated that the Apo-hTf/alprazolam interaction does not affect the protein secondary and tertiary structure significantly until the molar ratios (alprazolam/Apo-hTf) of 10, but the conformational changes become visible at higher molar ratios. The DSC results suggested that alprazolam stabilized the Apo-hTf at alprazolam/Apo-hTf molar ratio of 20. Based on the achieved results, this potentially therapeutic agent can significantly bind to Apo-hTf which also further confirmed by molecular docking study. This study on the interaction of the drug with Apo-hTf should be helpful for understanding the transportation and distribution of drugs in vivo, as well as the action mechanism and dynamics of a drug at the molecular level.