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 α,α-, α,β-, and β,β-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 α,α-trehalose is the highest and that of β,β-trehalose is the lowest, indicating that α-glycosyl bonds cleave more easily than β-glycosyl bonds. The relative ion abundance depends on both the α- and β-glycosyl linkage type and the number of α-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 β,β-trehalose is larger than those of α,α- and α,β-trehalose, indicating that the isotope effect on the β-glycosyl bond cleavage is larger than that on the α-glycosyl bond cleavage. The thermal energy increase in trehalose-d₈ molecules over the corresponding trehalose molecules is calculated from the vibrational modes.