Analysis of glycosyl bond cleavage and related isotope effects in collision-induced dissociation quadrupole-time-of-flight mass spectrometry of isomeric trehaloses.
The configuration isomers alpha,alpha-, alpha,beta-, and beta,beta-trehalose are distinguishable by a relative ion abundance analysis using collision-induced dissociation MS/MS measurements in electrospray ionization quadrupole-time-of-flight mass spectrometry. The relative abundance of the Y-type fragment ion of alpha,alpha-trehalose is the highest and that of beta,beta-trehalose is the lowest, indicating that alpha-glycosyl bonds cleave more easily than beta-glycosyl bonds. The relative ion abundance depends on both the alpha- and beta-glycosyl linkage type and the number of alpha-glycosyl bonds. The reaction path of glycosyl bond cleavage is calculated computationally using the molecular orbital method in the form of Hartree-Fock theory in conjunction with the 6-31G(d) basis set. The results are consistent with the experimental data. Isotope effects on the fragmentation of the glycosyl bonds are detected in the experiments of the H2O/D2O solvent systems. Furthermore, the isotope effect regarding beta,beta-trehalose is larger than those of alpha,alpha- and alpha,beta-trehalose, indicating that the isotope effect on the beta-glycosyl bond cleavage is larger than that on the alpha-glycosyl bond cleavage. The thermal energy increase in trehalose-d8 molecules over the corresponding trehalose molecules is calculated from the vibrational modes.
Yamagaki
Tohru
T
Department of Chemistry, School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 Japan. yamagaki@chem.s.u-tokyo.ac.jp
Fukui
Kazuhiko
K
Tachibana
Kazuo
K
D005947:Glucose / Q000737:chemistry*; D006868:Hydrolysis; D007554:Isotopes; D013058:Mass Spectrometry / Q000379:methods*; D008958:Models, Molecular; D014199:Trehalose / Q000737:chemistry*
D007554:Isotopes; D014199:Trehalose; D005947:Glucose