Biophysical study on the interaction of an anesthetic, vecuronium bromide with human serum albumin using spectroscopic and calorimetric methods

The interactions between an anesthetic, vecuronium bromide (VB) and human serum albumin (HSA) have been investigated systematically by steady-state/time-resolved fluorescence, circular dichroism (CD), UV–vis absorption, Fourier transform infrared spectroscopy (FTIR), mass spectroscopy and differential scanning calorimetry (DSC) methods under physiological conditions. The fluorescence quenching observed is attributed to the formation of a complex between HSA and VB, and the reverse temperature effect of the fluorescence quenching has been found and discussed. Fluorescence analysis has proved that there is one classical binding site on HSA for VB with a relative weak binding constant of 1.07 × 104 M−1 at 298 K. The primary binding pattern is determined by hydrogen bonding or van der Waals forces occurring in site I of HSA with ΔG° = −2.30 × 104 J mol−1, ΔS° = −233 J mol−1 K−1 and ΔH° = −9.23 × 104 J mol−1 at 298 K. VB could slightly change the secondary structure and induce unfolding of the polypeptides of protein. The DSC results provide quantitative information on the effect of VB on the stability of serum albumin. It is shown that VB can efficiently bind with HSA and be transported to the focuses needed.