Mass spectrometry enantioselective discrimination

Of the two related techniques, FAB found far greater use in studies of enantioselective discrimination as compared to other desorption/ionization methods, such as MALDI and secondary ion mass spectrometry (SIMS). Chan and coworkers demonstrated enantiodiscrimina-tion of amino acids by a-, P-, and y-cyclodextrins using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) [28]. The observed levels of enantioselectivity were found to be dependent on the size of cyclodextrin cavities, as well as on the length and functionality of the amino acid side chain. Vairamani and coworkers demonstrated discrimination of amino acid methyl esters using various monosaccharide hosts by liquid secondary ion mass spectrometry (LSIMS) [29]. It is curious that more work has not been done using these sources. MALDI, in particular, is a simple and straightforward technique. Various researchers have demonstrated the observation of noncovalent complexes [30-32], for example, between peptides and proteins, but relatively little work has been performed that focuses on studying enantioselective noncovalent interactions by MALDI-MS. 

Schug, K.A. (2007) Solution phase enantioselective recognition and discrimination by electrospray ionization— mass spectrometry state-of-the-art, methods, and an eye towards increased throughput measurements. Comb. Chem. High Throughput Screen., 10,301-316. 

Czerwenka, C, Maier, N.M., Lindner, W. (2004) Enantiomer discrimination by mass spectrometry non-covalent interactions of an N-derivatized dipeptide with various cinchona alkaloid derivatives and comparison with enantioselective liquid-phase separations. Anal. Bioanal. Chem., 379,1039-1044. 

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