CONFORMATIONS AND FOLDING OF LYSOZYME IONS IN VACUO

Proton transfer reactivity of isolated charge states of the protein he n egg-white lysozyme shows that multiple distinct conformations of thi s protein are stable in the gas phase, The reactivities of the 9+ and 10+ charge state ions, formed by electrospray ionization of ''native'' (disulfide-intact) and ''denatured'' (disulfide-reduced) solutions, a re consistent with values calculated for ions in their crystal structu re and fully denatured conformations, respectively, Charge states belo w 8+ of both forms, formed by proton stripping, have similar or indist inguishable reactivities, indicating that the disulfide-reduced ions f old in the gas phase to a more compact conformation.