Thermal dissociation of streptavidin homotetramer in the gas phase: Subunit loss versus backbone fragmentation

► Thermal dissociation pathways of gas phase protonated ions of the homotetramer streptavidin are elucidated. ► Backbone fragmentation and water loss compete with the loss of intact subunit. ► Kinetic data consistent with the presence of multiple non-interconverting structures. ► Proposed that backbone fragmentation requires unfolding of the N-terminus of the subunit.