Symmetrical Gas-Phase Dissociation of Noncovalent Protein Complexes via Surface Collisions

Previous gas-phase dissociation experiments of protein−protein complexes have resulted in product ion distributions that are asymmetric by charge and mass, providing limited insight into the chemical nature of subunit organization and interaction. In these experiments, a symmetric charge distribution results from an “energy sudden” collision of protein−protein complexes with a surface, indicating that it may be possible to probe the suboligomeric structure of noncovalent complexes in the gas phase. It is proposed that energy sudden surface activation of cytochrome C homodimers results in dissociation without significant unfolding of one of the monomeric subunits. Previously proposed mechanisms for the dissociation of protein−protein complexes are discussed in the context of these results. These experiments demonstrate the potential to preserve the structural details of subunit interaction within a protein−protein complex and help elucidate the asymmetric nature of macromolecular dissociation in the gas phase.