Gaseous myoglobin ions stored at greater than 300 K

Multiply-charged myoglobin ions retaining the prosthetic heme group have been formed by electrospray, injected into a quadrupole ion trap, and stored for up to one second prior to mass analysis. Collisional activation experiments indicate that these ions readily fragment into the charged heme group and the complementary apomyoglobin ion. No fragmentation is observed, however, upon ion storage in the presence of a neutral bath gas at 1 × 10^?3 torr for up to one second. The significance of this observation is that these non-covalently-bound ions, in which both the heme group and the polypeptide carry charge, are kinetically stable for over one second at room temperature and, perhaps, at higher temperatures. This suggests that other biologically relevant ions derived using electrospray and bound by non-covalent interactions can be studied using the various tools available with ion storage mass spectrometers and by other techniques that employ relatively high pressure environments for the study of gaseous ions.