Hydrogen Deuterium Exchange Mass Spectrometry of Oxygen Sensitive Proteins

The protocol detailed here describes a way to perform hydrogen deuterium exchange coupled to mass spectrometry (HDX-MS) on oxygen sensitive proteins. HDX-MS is a powerful tool for studying the protein structure-function relationship. Applying this technique to anaerobic proteins provides insight into the mechanism of proteins that perform oxygen sensitive chemistry. A problem when using HDX-MS to study anaerobic proteins is that there are many parts that require constant movement into and out of an anaerobic chamber. This can affect the seal, increasing the likelihood of oxygen exposure. Exposure to oxygen causes the cofactors bound to these proteins, a common example being FeS clusters, to no longer interact with the amino acid residues responsible for coordinating the FeS clusters, causing loss of the clusters and irreversible inactivation of the protein. To counteract this, a double vial system was developed that allows the preparation of solutions and reaction mixtures anaerobically, but also allows these solutions to be moved to an aerobic environment while shielding the solutions from oxygen. Additionally, movement isn't limited like it is in an anaerobic chamber, ensuring more consistent data, and fewer errors during the course of the reaction.