Chiral discrimination of α-amino acids by the DNA triplet GCA using amino acids as a co-selector

The DNA triplet GCA is successfully used as a chiral selector for the chiral discrimination of amino acids using amino acids themselves as a co-selector. Chiral discrimination was achieved by investigating the collision-induced dissociation spectra of the [X-A + X-R + 2Y - 2H](2-) ion generated by electrospraying a mixture of analyte amino acid (X-A), reference amino acid (X-R) and GCA (Y). The relative abundances of fragment ions resulting from the competitive loss of reference and X-A's are considered for measuring the degree of chiral discrimination. GCA successfully shows D-selectivity for all the amino acids, except Tyr and Lys. The success of the method lies in the selection of a suitable X-R that has closer GCA binding affinity to that of analyte. The degree of discrimination by GCA is improved in the presence of the reference, and the chirality of the reference does not change the selectivity of GCA. The suitability of the method for the measurement of optical purity is also demonstrated. Copyright (c) 2007 John Wiley & Sons, Ltd.