In vitro study on the interaction of methoxyflurane with human serum albumin: Phenotypic characterization

The binding behaviour of methoxyflurane to human serum albumin (HSA) was studied employing fluorescence, resonance light scattering (RLS), circular dichroism (CD) spectroscopy, UV–vis absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). The fluorescence spectra revealed that methoxyflurane causes the quenching of the fluorescence emission of serum albumin. Stern–Volmer plots were made and quenching constants (4.01 × 104 M−1 at 298 K) were thus obtained. Association constant at 298 K was 8.52 × 103 M−1 for the system, which could affect the distribution, metabolism, and excretion of the drug. TEM and RLS proved the existence of aggregates of HSA–methoxyflurane. The alterations of protein conformation in the presence of methoxyflurane were confirmed by the evidences from UV, CD and FTIR spectra. Site competitive experiments also suggested that the primary binding site for methoxyflurane was located at subdomain IIA which is close to Trp residue 214.