Probing the Stability of Noncovalent Interactions Responsible for Covalently Linked Diubiquitin Ion Structure Using nESI-TWIMS-MS and Collision Induced Unfolding

摘要

CIU provides distinct fingerprints for each of the linkage types of covalent diubiquitin and noncovalent diubiquitin supply ingisight into the relative stabilities of each. Furthermore, it can be concluded that K63 adopts an unquestionably closed conformation at low collision energy and low charge state; that the charge state of the ion has a dramatic effect on the stability of the dimer; and that the addition of methanol induces the collapse of diubiquitin, contrary to the increase in CCS observed for the monomer. Furthermore, comparison of CIU fingerprints for the noncovalent dimer, the hydrophobic interface stabilized K48 dimer, and electrostatically stabilized K63 dimer ions supports previous assertions that the noncovalent dimer is stabilized by hydrophobic interaction.