Quantification of binding of some thiol-reactive clenbuterol analogues to bovine serum albumin by electron paramagnetic resonance spectroscopy

The only free thiol group of bovine serum albumin (BSA) was coupled in a high yield with some novel thiol-reactive clenbuterol analogues. The unreacted cysteines were probed with maleimide spin label to determine the yield of the coupling reaction. A novel approach to determining free thiol groups of BSA quantitatively by electron paramagnetic resonance spectroscopy and spectral decomposition without the usual gel-filtration step or extensive dialysis is presented.