Chunxiang Yao's research while affiliated with Osaka Prefecture University and other places

Publications (11)

Article
Radicals containing the histidine residue have been generated in the gas phase by femtosecond electron transfer to protonated histidine-N-methylamide (1H+), Nalpha-acetylhistidine-N-methylamide (2H+), Nalpha-glycylhistidine (3H+), and Nalpha-histidylglycine (4H+). Radicals generated by collisional electron transfer from dimethyldisulfide to ions 1H...
Article
Gas-phase cytosine molecules and cation-radicals represent a complex system of several nearly isoenergetic tautomers within each group. Computational methods differ in ordering the relative enthalpies of neutral cytosine tautomers. At our highest level of theory, CCSD(T)/aug-cc-pVTZ calculations find an enol form, anti-2-hydroxy-4-aminopyrimidine (...
Article
Gas-phase cytosine molecules and cation–radicals represent a complex system of several nearly isoenergetic tautomers within each group. Computational methods differ in ordering the relative enthalpies of neutral cytosine tautomers. At our highest level of theory, CCSD(T)/aug-cc-pVTZ calculations find an enol form, anti-2-hydroxy-4-aminopyrimidine (...
Article
Cytosine cations were generated by chemical ionization and fast-atom bombardment of cytosine, and their dissociations in the gas phase were studied by tandem mass spectrometry and quantum chemistry calculations at levels of theory up to CCSD(T)/aug-cc-pVTZ. Metastable cytosine cations undergo loss of NH3, H2O, and [CHNO] molecules as major dissocia...
Article
Ammonium radicals derived from protonated beta-alanine N-methyl amide (BANMA) were generated by femtosecond collisional electron transfer to gas-phase cations prepared by chemical ionization and electrospray. Regardless of the mode of precursor ion preparation, the radicals underwent complete dissociation on the time scale of 5.15 micros. Deuterium...
Article
A computational study at correlated levels of theory is reported to address the structures and energetics of transient radicals produced by hydrogen atom abstraction from C-1, C-2, C-3<sub>,</sub> C-4, C-5, O-1, O-3, and O-5 positions in 2-deoxyribofuranose in the gas phase and in aqueous solution. In general, the carbon-centered radicals are found...
Article
Tautomers of 1-methylcytosine that are protonated at N-3 (1+) and C-5 (2+) have been specifically synthesized in the gas phase and characterized by tandem mass spectrometry and quantum chemical calculations. Ion 1+ is the most stable tautomer in aqueous and methanol solution and is likely to be formed by electrospray ionization of 1-methylcytosine...
Article
Welch ein Radikalziel! Zwei zentrale Wasserstoffatomaddukte von 1-Methylcytosin wurden durch die gezielte chemische Erzeugung von Cytosinradikalen hergestellt. Der Femtosekundenstoßtransfer von Elektronen aus molekularen Elektronendonoren (Dimethyldisulfid und Trimethylamin) auf Gasphasentautomere von protoniertem 1-Methylcytosin liefert stabile Ra...
Article
The title hypervalent ammonium radicals were investigated by neutralization-reionization mass spectrometry and quantum chemical calculations. Methyl ammonium (1) forms a small fraction of metastable radicals from isotopomers CH3ND3 (la) and CD3NH3 (1b) when these are produced by femtosecond electron transfer to vibrationally excited precursor catio...
Article
Cation-radicals and dications corresponding to hydrogen atom adducts to N-terminus-protonated N(alpha)-glycylphenylalanine amide (Gly-Phe-NH(2)) are studied by combined density functional theory and Møller-Plesset perturbational computations (B3-MP2) as models for electron-capture dissociation of peptide bonds and elimination of side-chain groups i...
Article
Combined ab initio and density functional theory calculations at the B3-MP2/6-311++G(3df,2p) level of theory are used to investigate the structures and energetics of radicals produced by hydrogen atom addition to cytosine tautomers, 1-methylcytosine, and cytosine−water complexes. H-atom adducts to the N-3 positions are the most stable radical isome...

Citations

... Several experimental and theoretical papers can be found in the literature on prototropic conversions for cytosine in the gas phase, solid state, and microhydrated cytosine . Depending on the experimental method applied (matrix isolation IR, MW, REMPI, IR laser in helium nanodroplets, MS, core-level X-ray photoemission, and near-edge X-ray absorption), two or three tautomers have been detected for cytosine in the gas phase [9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Matrix isolation (argon and nitrogen matrices at 15 K) infrared [11] and Molecular beam microwave (MW) [12] spectroscopies suggested mixture of amino-oxo tautomer and the "rare" aminohydroxy and imino-oxo tautomers while through a Resonance Enhanced Multiphoton Ionization (REMPI) [13,14] investigation it was established that both amino-oxo and enol-amino tautomers coexist in the gas-phase. ...
... Among the canonical structures, the lowest energy isomer was the 2-oxo, N3-H, 4imine cation radical dC5 +· that was marginally more stable than the classical 2-oxo, 4-NH 2 cation-radical dC1 +· (Table 3). This order of thermodynamic stability was similar to that reported for analogous cytosine cation radicals carrying H or a methyl group at N-1. 24,41 Three of the noncanonical cation radicals, dC7 +· -dC9 +· , were found to be substantially more stable than the canonical forms (Table 3, Figure 3). The lowest-energy structure dC7 +· was an N3-H cytosine tautomer which showed a near-coplanar arrangement of the deoxyribose and cytosine rings, as illustrated by the C2−N1−C1′−O dihedral angle (Figure 3). ...
... The reactions are likely initiated by hydrogen atom abstraction from the sugar molecule. Based on a recent publication [23], the bond between hydrogen and C-5 is the one with the lowest homolytic dissociation energy in 2-deoxyribofuranoses like 1-O- methyl-2-deoxy-D-ribose. However, breaking the bond of C-4 or C-3 to hydrogen is less than 2 kcal/mol more endothermic. ...
... Very often, their signals, being in the background, cannot be identified. Some isomers of neutral 1methylcytosine have already been studied in various environments [95][96][97][98][99][100][101]. There are also a few documents on radicals [102][103][104][105][106][107] and metal complexes [108][109][110]. ...
... These dissociations are also observed for the [Sn(Ura-H)] + ion (giving m/z 188 and 162), and have been already reported for the [Pb(Ura-H)] +ion.43 Note also that elimination of 43u (H,N,C,O) is common to both protonated45,46,47,48 or metal-uracil.43, 49, 50, 51, 52 Another interesting dissociation pathway is the sequential elimination of methyl radicals from the [(CH 3 ) 2 Sn(N,C,O)] + complex. ...
... 5.3. RÉSULTATS ET DISCUSSIONSqui sont de l'ordre de 0.4 eV pour la rupture de la liaison C − N H 3 après la capture d'un électron[146] [152], et autour de 0.6 -0.8 eV pour un transfert de proton dans le tri-peptide doublement protoné TIK[153]. Il existe donc un mécanisme menant à la baisse de l'état de charge d'un peptide protoné contenant au moins un groupement N H + 3 solvaté par CE : la perte de N H + 4 (CE).Figure 5.8 -Spectres de masse des espèces cationiques formées après ECD et CID à 5V du complexe triplement protoné [KY K + 3H] 3+ (CE) 1 (m/z = 234,814). ...
... Charge inversion mass spectrometry using alkali metal targets for singly protonated peptides and amino acids provide information on radical traps in the dissociation mechanism of the charge reduced doublet state peptides, as evidenced by a computational study. [54][55][56][57] For multiply charged peptides upon collision with alkali metals, N-C α bond cleavage induced by electron transfer processes have been reported by Hvelplund et al. 58) A combined experimental and computational study of the e ect of proline in model dipeptides, i.e., Pro-Gly and Gly-Pro was performed. 55) Gas-phase protonated peptide ions were discharged by collision with potassium or cesium atoms at 3 keV collision energies, and the peptide radical intermediates and their dissociation products were analyzed following collisional ionization to anions. ...
... In case of ECD and ETD however, the labile bonds survive activation, while backbone cleavage of the peptide occurs. [45][46][47][48][49][50][51] Nevertheless, a number experimental and theoretical studies 35,40,44,[49][50][51][52] contradict this assumption suggesting that long-lived intermediates are formed during ECD and ETD fragmentation processes and that IVR is also relevant for open-shell peptide ion chemistry. ...
... Some isomers of neutral 1methylcytosine have already been studied in various environments [95][96][97][98][99][100][101]. There are also a few documents on radicals [102][103][104][105][106][107] and metal complexes [108][109][110]. However, literature data are not complete for MC and only a little information can be derived on ionization effects. ...
... These dissociations are also observed for the [Sn(Ura-H)] + ion (giving m/z 188 and 162), and have been already reported for the [Pb(Ura-H)] +ion.43 Note also that elimination of 43u (H,N,C,O) is common to both protonated45,46,47,48 or metal-uracil.43, 49, 50, 51, 52 Another interesting dissociation pathway is the sequential elimination of methyl radicals from the [(CH 3 ) 2 Sn(N,C,O)] + complex. ...