Fig. 1. The wide range of applications for HDX-MS in many protein-folding studies.

Clockwise from top left: Hamdi et al.²⁴ localized dehydration and zinc-activated disorder-to-order transitions in abiotic plant stress response proteins using HDX-MS. Baños-Mateos et al.²⁵ demonstrated how HDX-MS can be used in combination with X-ray crystallography and cryo-electron microscopy (cryo-EM) when determining the mechanism of exonuclease activity of DnaE1. Lim et al.²⁶ determined how an increase in temperature alters the Dengue virus capsid structure, resulting in an alteration in antibody-binding mode. Using ETD-HDX/MS/MS, Masson et al.²⁷ discerned the basis of isotype specificity of pharmaceutical compounds by determining single-residue exchange rates. Merkle et al.²⁸ localized the substrate-dependent partial unwinding of transmembrane helices, which facilities substrate translocation using HDX-MS. Lee et al.²⁹ revealed a new allosteric mechanism for interrupting the antiapoptotic binding of MCL-1 to BH3 domains, providing a new avenue for cancer therapy. Shukla et al.³⁰ demonstrated how HDX-MS can provide mechanistic and dynamic detail to cryo-EM structures, and how HDX-MS can aid modeling of X-ray structures within the cryo-EM density. Adams et al.³¹ illustrated the utility of HDX-MS, used in conjunction with X-ray crystallography and biophysical methods, to reveal how the monoclonal antibody VHH6 contemporaneously interacts with IL-6 and gp80 through a junctional epitope. Rostislavleva et al.³² pushed the limits of HDX-MS with the large lipid kinase VPS34 complex II by both determining the membrane-interacting regions of the lipid kinase and screening nanobodies to facilitate crystallization and subsequent structure determination. By altering the pH of the labelling solution, de Vera et al.³³ observed interactions of disordered protein domain on a millisecond timescale by HDX-MS.