Discovery of EX1 kinetics in hydrogen exchange (HX) mass spectrometry (MS) experiments
is rare. Proteins follow the EX1 kinetic regime when cooperative unfolding events
simultaneously expose multiple residues to solvent such that they all become deuterated
together before the region is able to refold. A number of factors can contribute to what we
call “false EX1” in which it appears as though EX1 occurs in a protein when it probably does
not. One of the contributors to false EX1 is peptide carryover between chromatographic runs …