title: Study of FK-binding protein: FK506-metabolite complexes by electrospray mass spectrometry: correlation to immunosuppressive activity.
abstract: 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.
authors.affiliation: Isotechnika Inc., Edmonton, Alberta, Canada.
authors.forename: D J
authors.initials: DJ
authors.lastname: Trepanier
authors.forename: M D
authors.initials: MD
authors.lastname: Abel
authors.forename: D G
authors.initials: DG
authors.lastname: Freitag
authors.forename: R W
authors.initials: RW
authors.lastname: Yatscoff
mesh_terms: D006801:Humans; D020104:Immunophilins / Q000032:analysis*; D007166:Immunosuppressive Agents / Q000032:analysis*; D013058:Mass Spectrometry / Q000379:methods*; D011994:Recombinant Proteins / Q000032:analysis; D013329:Structure-Activity Relationship; D022021:Tacrolimus Binding Proteins
chemical_list: D007166:Immunosuppressive Agents; D011994:Recombinant Proteins; D022021:Tacrolimus Binding Proteins; D020104:Immunophilins