HDX-AnalysesIn principle, two types of HDX-analyses are available for the investigation of the higher order structure of a protein or a peptide. Both types of analyses are based on so-called HDX (H/D exchange) experiments.In the case of analyses of the first type, the H/D exchange is determined by means of LC/MS data sets that are acquired without fragmentation. The method employed by MassMap® for the analysis of such data is particularly useful if structural differences between protein samples are to be elucidated without prior knowledge of the differences.The analyses of the second type are based on HDX/ETD experiments, i.e. experiments using electron transfer dissociation. It is the purpose of HDX/ETD experiments to determine the exchange rate constants of individual amide hydrogens of peptides. Due to a high degree of automation, the MassMap® method also named ETD Fragment Analyzerleads to more precise results and is significantly less time-consuming than manual approaches.