Exploration of mononucleotides as fixed ligands towards chiral discrimination of hexose monosaccharides by the kinetic method

Abstract

The most recent version of the kinetic method, i.e. fixed ligand method, is applied towards chiral discrimination of three pairs of enantiomeric hexose monosaccharides under mass spectral conditions. Naturally occurring mononucleotides are used as fixed ligands (FL) and the amino acids are selected as the chiral references (ref) to discriminate the analyte (A), the enantiomers of glucose, mannose and galactose. Chiral discrimination is achieved by investigating the collision-induced dissociation spectra of trimeric complex ion, [Ni^II(FL)(ref)(A)–H]⁺ generated by electrospraying the solution mixture of D- or L-analyte (A), FL, amino acid (ref) and NiCl₂. The relative abundance of product ions resulting from the competitive loss of reference amino acid and analyte are considered for measuring the degree of chiral discrimination by applying the kinetic method. L-Asp, L-Thr, L-Glu, L-Trp and L-Ser are found as suitable reference compounds. Among the tested mononucleotides (5′AMP, 5′GMP, 5′CMP, 5′UMP and 5′TMP), 5′GMP is found to be the best for the studied analytes. Chiral discrimination is found to depend on the nature of the monosaccharide, the functional groups present in the side chain of reference amino acids and the configuration of reference amino acids.