A barrier to the use of hydrogen exchange mass spectrometry (HX-MS) in many contexts, especially analytical characterization of various protein therapeutic candidates, is that differences in temperature, pH, ionic strength, buffering agent, or other additives can alter chemical exchange rates, making HX data gathered under differing solution conditions difficult to compare. Here, we present data demonstrating that HX chemical exchange rates can be substantially altered not only by the well-established variables of temperature and pH, but by additives including arginine, guanidine, methionine, and thiocyanate. To compensate for these additive effects, we have developed an empirical method to correct the hydrogen... More
A barrier to the use of hydrogen exchange mass spectrometry (HX-MS) in many contexts, especially analytical characterization of various protein therapeutic candidates, is that differences in temperature, pH, ionic strength, buffering agent, or other additives can alter chemical exchange rates, making HX data gathered under differing solution conditions difficult to compare. Here, we present data demonstrating that HX chemical exchange rates can be substantially altered not only by the well-established variables of temperature and pH, but by additives including arginine, guanidine, methionine, and thiocyanate. To compensate for these additive effects, we have developed an empirical method to correct the hydrogen exchange data for these differences. First, differences in chemical exchange rates are measured using an unstructured reporter peptide, YPI. An empirical chemical exchange correction factor, determined using the HX data from the reporter peptide, is then applied to the HX measurements obtained from a protein of interest under different solution conditions. We demonstrate that the correction is experimentally sound through simulation and in a proof-ofconcept experiment using unstructured peptides under slow-exchange conditions (pD 4.5 at ambient temperature). To illustrate its utility, we applied the correction to HX-MS excipient screening data collected for a pharmaceutically-relevant IgG4 mAb being characterized to determine the effects of different formulations on backbone dynamics.
