Study of FK-binding protein: FK506-metabolite complexes by electrospray mass spectrometry: correlation to immunosuppressive activity.

摘要

Electrospray ionization mass spectrometry was used to study several non-covalent FK-binding protein (FKBP) immunosuppressant complexes in the gas phase. Relative FKBP binding affinities were determined from the signal ratio for the 7+ charge states of bound and unbound complexes as a function of capillary exit voltage. All complexes displayed a 1:1 binding stoichiometry. The relative gas-phase binding affinities were found to be well correlated with in vitro FKBP binding and in vitro immunosuppression (rapamycin > FK506 > or = 31-demethyl FK506 > 13-demethyl FK506 Cyclosporin A; CsA). The method demonstrates potential as a simple, rapid, and automatable technique for prediction of the immunosuppressive activity of FKBP:drug complexes.