Ongoing and Future Challenges

Jejfrey W. Hudgens , Richard Y.-C. Huang, and Emma D Ambro  

Hydrogen Exchange Mass Spectrometry of Proteins Fundamentals, Methods, and Applications, First Edition. Edited by David D. Weis. 

More recently, successes in the basic research laboratory have emboldened the pharmaceutical industry to employ HX-MS for the characterization of biopharmaceutical products that will enter commCTce (see also Chapter 13). To assure the quality of the product, the offeror might present HX-MS data that establish  

The calibration hierarchy is the sequence of calibrations from a reference to the final measuring system, where the outcome of each calibration depends on the outcome of the previous calibration [13]. This hierarchy requires that for measurements incorporating more than one input quantity in the measurement model (e.g., pH, 7), each input quantity must itself be metrologically traceable. In addition, each measurement and derived quantity is listed with an evaluated uncertainty that captures the uncertainties of the measurements and of the calibration hierarchy. Also, because the propagation of variances is additive, measurement uncertainty increases throughout the calibration hierarchy fiomthe RM (which is ideally a certified reference material aka CRM) to the sample. A statement describing the uncertainty is essential, as a measured quantity value unaccompanied by a measurement uncertainty is not only useless, but it is potentially dangerous because the measured value may be misinterpreted or misused. 

The ISO and GUM documents were written to encompass most common quantitative measurands. For biological entities, some extension is necessary, but these documents provide sufficient guidance to place HX-MS upon the strong foundation of the SI. For HX-MS, the relevant fundamental units are kilogram (kg), second (s), ampere (A), kelvin (K), and mole (mol). The measurand of HX-MS is always the m z spectrum of the deuterium shifted analyte or one of its proteolytic peptide ions.  

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