Search

Abstract: Using a very weak electric field to accelerate the photofragment ions, we have constructed a very simple photofragment translational spectrometer with only a 50 mm total flight path, but we can get photofragment translational spectra with high resolution. On this apparatus, we have performed the photodissociation of CF3I at 281.73 nm, and the same laser will ionize I*(2P1/2) via REMPI. Seven well-resolved vibrational peaks were obtained. Six of them are assigned to the umbrella vibrational mode v2=0–5 states of photofragment CF3. The average internal energy is about 21% of the available energy. [Copyright &y& Elsevier]

The photodissociation of CF3I at 248 nm was performed on our high-resolution photofragment translational spectrometer. For further improvement of the resolution, we have taken the following procedures: (1) Kr was used as carrier gas, (2) optimum molecular beam angle θopt (when VMB⊥VCM) was selected, (3) the longitudinal molecular beam angle spread was reduced, and (4) the ionization region for photofragments was diminished. The photofragment translational spectra of I* (2P1/2) reveal eight well-resolved vibrational peaks. The highest peak was assigned to be v2=5 of the ν2 vibrational mode, and then the dissociation energy would be D0(C–I)=18 810±200cm−1=53.8±0.6 kcal/mol. [Copyright &y& Elsevier]

N-glycosylation is one of the most frequently occurring protein post-translational modifications (PTMs) with broad cellular, physiological and pathological relevance. Mass spectrometry-based N-glycomics has become the state-of-the-art instrumental analytical pipeline for sensitive, high-throughput and comprehensive characterization of N-glycans and N-glycomes. Improvement and new development of methods in N-glycan release, enrichment, derivatization, isotopic labeling, separation, ionization, MS, tandem MS and informatics accompany side-by-side wider and deeper application. This review provides a comprehensive update of mass spectrometry-based qualitative and quantitative N-glycomics in the years of 2017–2018. Image 1 • MS-based N-glycomics is the best tool for high-throughput profiling of N-glycans. • Qualitative information of N-glycans at multi-level are readily available. • Updated progresses in frontier methods and applications in 2017–2018 are reviewed. [ABSTRACT FROM AUTHOR]

By fixing the hydrogen bond length (O⋯H⋯N) at a value, the potential energy curves of the [M⋯H⋯NH3]+ were explored at the HF/6-31G(d) and B3LYP/6-31G(d) level of theory. The calculations indicate that as the hydrogen bond length is increased, the proton transfer barrier increases and the single-well potential energy curve tends to become double-welled. To model the proton transfer (PT) in ‘real’ system, the transition state connecting M⋯(H–NH3)+ and (M–H)+⋯NH3 has been optimized and the reaction path gives an estimate of the PT barrier. Correlated electronic structure calculation, coupled with ZPE correction, provides a better understanding of the PT barrier. [Copyright &y& Elsevier]