Online, high-pressure digestion system for protein characterization by hydrogen/deuterium exchange and mass spectrometry

The rapid and complete digestion of proteins is important when protein characterization by hydrogen-deuterium exchange (HDx) is coupled with mass spectrometry. We developed a single-pump, online, high-pressure digestion system that relies on UPLC technology to aid in the digestion of proteins. Two model proteins, amyloid β-peptide 1-42 (Aβ 1-42) and an HIV-1 capsid mutant protein (NBSA), were used to demonstrate the efficacy of the highpressure system. Both model proteins readily aggregate and are difficult to digest under normal conditions. Our high-pressure system successfully digests these proteins into small, overlapping peptides. The extra information afforded by overlapping peptides allows us to pinpoint HDx protection to protein segments smaller than the digested peptide. The calculated average segment length (ASL) for both model proteins decreased by 2-fold for high-pressure digestion compared to digestion at ambient pressure.