IN-TRAP CLEANUP OF PROTEINS FROM ELECTROSPRAY-IONIZATION USING SOFT SUSTAINED OFF-RESONANCE IRRADIATION WITH FOURIER-TRANSFORM ION-CYCLOTRON RESONANCE MASS-SPECTROMETRY

Electrospray ionization Fourier transform ion cyclotron resonance (FI? CR) mass spectrometry is capable of producing high mass resolving powe r and improved mass accuracy for large proteins and noncovalent comple xes when coupled with collisionally induced dissociation (CID) of nonc ovalent adducts and consequent minimization of ion charge density in t he ICR trap during measurements. This work demonstrates the applicatio n of in-trap cleanup to several biologically relevant systems, includi ng carbonic anhydrase, 4-oxalocrotonate tautomerase (4OT) analogue, an d SecB, a chaperone from Escherichia coli. In-trap cleanup yields impr oved mass measurements for these systems and is expected to further en able measurements for even more complex systems where adduction levels have precluded study of intact complexes.