Vìsnik Odesʹkogo Nacìonalʹnogo Unìversitetu: Hìmìâ (May 2019)
STUDY OF INTERACTION OF FABOMOTIZOLE DIHYDROCHLORIDE WITH HUMAN SERUM ALBUMIN BY FLUORESCENT METHOD
Abstract
Drug-protein binding has become an important research field in life sciences, chemistry and clinical medicine. Under physiological conditions, in vitro interaction between the selective anxiolytic (non-benzodiazepine receptor agonist) drug 5-ethoxy-2-[(2-morpholin-4-yl-ethyl)thio]-1H-benzimidazole dihydrochloride (fabomotizole dihydrochloride, FD) and human serum albumin (HSA) was investigated at excitation wavelength 280 nm and at different temperatures (298 K and 313 K) by fluorescence emission spectroscopy. The emission of HSA is characterized by a broad emission band at 348 nm. The results of the experiment showed that FD quench the intrinsic fluorescence of the protein as a result of static interaction in the HSA – FD system, which is confirmed by shifts in the difference UV spectra of the HSA – FD and the reduction of the binding constant for the HSA – FD system with increasing temperature. The constant (lgKA = 6.15 at 298 K) and the number of binding sites of the HSA – FD system are established. The negative values of enthalpy change (ΔHº) and entropy change (ΔSº) can be attributed in part to van der Waals forces and in part to the formation of hydrogen bonds. A value of 1.24 nm for the average distance r between FD (acceptor) and tryptophan residues of HSA (donor) was estimated on the basis of the Förster resonance energy transfer (FRET). The overlap of the absorbance spectrum of FD with the fluorescence emission spectrum of HSA has been shown. The obtained data show that FD can be used as fluorescence probe for proteins being especially suitable for detecting the changes in the local polarity. Since, the pharmaceutical firms need standardized screens for protein binding in the first step of new drug design, this kind of study of interaction between HSA with FD would be useful in pharmaceutical industry and clinical medicine.
Keywords
