Gas-phase dissociation pathways of a tetrameric protein complex

The gas-phase dissociation of the tetrameric complex transthyretin (TTR) has been investigated with tandem-mass spectrometry (tandem-MS) using a nanoflow-electrospray interface and a quadrupole time-of-flight (Q-TOF) mass spectrometer. The results show that highly charged monomeric product ions dissociate from the macromolecular complex to form trimeric products. Manipulating the pressure conditions within the mass spectrometer facilitates the formation of metastable ions. These were observed for the transitions from tetrameric to monomeric and trimeric product ions and additionally for losses of small molecules associated with the protein complex in the gas phase. These results are interpreted in the light of recent mechanisms for the electrospray process and provide insight into the composition and factors governing the stability of macromolecular ions in the gas phase.