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Updated: Jul 17, 2026

Mass Spectrometric Approaches to Study Protein Structure and Interactions in Lyophilized Powders
Published on: April 14, 2015
Trehalose and calcium exert site-specific effects on calmodulin conformation in amorphous solids
Yunsong Li1, Todd D Williams, Richard L Schowen
1Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, KS 66047, USA.
Abstract:
We have adapted hydrogen/deuterium (H/D) exchange with electrospray ionization mass spectrometry (ESI-MS) to study protein conformation and excipient interactions in lyophilized solids. Using calmodulin (CaM, 17 kD) as a model protein, we demonstrate that trehalose and calcium exert site-specific effects on protein conformation. The effects of calcium are observed primarily in the calcium binding loops, while those of trehalose are observed primarily in non-terminal alpha-helical regions. To our knowledge, this is the first demonstration of site-specificity in the effects of excipients on protein structure in the solid state, and of the utility of H/D exchange with ESI-MS to characterize proteins in amorphous solids.
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