Enantiomer-Selective Photo-Induced Reaction of Protonated Tryptophan with Disaccharides in the Gas Phase.

Doan, Thuc N.; Fujihara, Akimasa

In order to investigate chemical evolution in interstellar molecular clouds, enantiomer-selective photo-induced chemical reactions between an amino acid and disaccharides in the gas phase were examined using a tandem mass spectrometer containing an electrospray ionization source and a cold ion trap. Ultraviolet photodissociation mass spectra of cold gas-phase noncovalent complexes of protonated tryptophan (Trp) enantiomers with disaccharides consisting of two d-glucose units, such as d-maltose or d-cellobiose, were obtained by photoexcitation of the indole ring of Trp. NH2CHCOOH loss via cleavage of the Cα–Cβ bond in Trp induced by hydrogen atom transfer from the NH3 group of a protonated Trp was observed in a noncovalent heterochiral H (l-Trp)(d-maltose) complex. In contrast, a photo-induced chemical reaction forming the product ion with m/z 282 occurs in homochiral H (d-Trp)(d-maltose). For d-cellobiose, both NH2CHCOOH elimination and the m/z 282 product ion were observed, and no enantiomer-selective phenomena occurred. The m/z 282 product ion indicates that the photo-induced C-glycosylation, which links d-glucose residues to the indole moiety of Trp via a C–C bond, can occur in cold gas-phase noncovalent complexes, and its enantiomer-selectivity depends on the structure of the disaccharide.

TRYPTOPHAN; ENANTIOMERS; DISACCHARIDES; MOLECULAR evolution; TANDEM mass spectrometry; PHOTODISSOCIATION

Origins of Life & Evolution of the Biosphere, 2018, Vol 48, Issue 1, p123

0169-6149

Academic Journal

10.1007/s11084-017-9544-3