Using Ion Mobility Mass Spectrometry to Determine the Stereochemistry of Biopolymer Building Blocks

Amino acids and carbohydrates are involved in many biological process which are critical in determining their accurate characterization. These monosaccharide percussors are fundamental building blocks to their functionality such as cell-cell recognition, cellular adhesion, protein folding and solubility, metabolism, and immune/host pathogen response. All amino acids, except glycine, exist in two stereochemical forms, with the L-form being most common in nature. These precursors can have multiple structures that can make their characterization complex. For example, aldohexoses have four chiral centers and, thus, 2⁴ = 16 isomers. There will be eight d-isomers and eight l-isomers. We have developed an approach that allows us to identify the absolute configuration of these biopolymer building blocks. In this method, the analyte is derivatized with an optically pure compound containing an additional stereochemical center, the labeled species can be resolved by ion mobility mass spectrometry. Differences in collision cross section were calculated. The hypothesis of this approach has been evaluated on aldohexose monosaccharides, amino acid standards, and peptides.