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141.
Amino Acid Oxidation: A Combined Study of Cysteine Oxo Forms by IRMPD Spectroscopy and Simulations
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Dr. Debora Scuderi Prof. Enrico Bodo Dr. Barbara Chiavarino Prof. Simonetta Fornarini Prof. Maria Elisa Crestoni 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(48):17239-17250
The redox activity of cysteine sulfur allows numerous post‐translational protein modifications involved in the oxidative regulation of metabolism, in metal binding, and in signal transduction. A combined approach based on infrared multiple photon dissociation spectroscopy at the Centre Laser Infrarouge d'Orsay (CLIO) free electron laser facility, calculations of IR frequencies, and finite temperature ab initio molecular dynamics simulations has been employed to characterize the gas‐phase structures of deprotonated cysteine sulfenic, sulfinic, and sulfonic acids, [cysSOx]? (x=1, 2, 3, representing the number of S‐bound oxygen atoms), which are key intermediates in the redox‐switching chemistry of proteins. The ions show different structural motifs owing to preferential binding of the proton to either the carboxylate or sulfur‐containing group. Due to the decreasing basicity of the sulfenic, sulfinic, and sulfonic terminals, the proton bound to SO? in [cysSO]? migrates to the carboxylate in [cysSO3]?, whereas it turns out to be shared in [cysSO2]?. Evidence is gathered that a mixture of close‐lying low‐energy conformers is sampled for each cysteine oxo form in a Paul ion trap at room temperature. 相似文献
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143.
Effects of Aromatic Fluorine Substitution on Protonated Neurotransmitters: The Case of 2‐Phenylethylamine
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M. Sc. Markus Schütz Dr. Aude Bouchet Prof. Barbara Chiavarino Prof. Maria Elisa Crestoni Prof. Simonetta Fornarini Prof. Otto Dopfer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(24):8124-8136
Fluorination of pharmaceutical compounds is a common tool to modulate their physiochemical properties. We determine the effects of site‐specific aromatic fluorine substitution on the geometric, energetic, vibrational, and electronic properties of the protonated neurotransmitter 2‐phenylethylamine (xF‐H+PEA, x=ortho, meta, para) by infrared multiphoton photodissociation (IRMPD) in the fingerprint range (600–1750 cm?1) and quantum chemical calculations at the B3LYP‐D3/aug‐cc‐pVTZ level. The IRMPD spectra of all ions are assigned to their folded gauche conformers stabilized by intramolecular NH+???π hydrogen bonds (H‐bonds) between the protonated amino group and the aromatic ring. H→F substitution reduces the symmetry and allows for additional NH+???F interactions in oF‐H+PEA, leading to three distinct gauche conformers. In comparison to oF‐H+PEA, the fluorination effects on the energy landscape (energy ordering and isomerization barriers) in pF‐H+PEA and mF‐H+PEA with one and two gauche conformers are less pronounced. The strengths of the intramolecular NH+???F and NH+???π bonds are analyzed by the noncovalent interaction (NCI) method. 相似文献
144.
Stereodynamics in the Collisional Autoionization of Water,Ammonia, and Hydrogen Sulfide with Metastable Rare Gas Atoms: Competition Between Intermolecular Halogen and Hydrogen Bonds
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Prof. Stefano Falcinelli Dr. Alessio Bartocci Prof. Simonetta Cavalli Prof. Fernando Pirani Prof. Franco Vecchiocattivi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(2):764-771
Recent experiments on the title subject, performed with a high‐resolution crossed‐beam apparatus, have provided the total ionization cross sections as a function of the collision energy between noble gas atoms, electronically excited in their metastable states (Ng*), and H2O, H2S, and NH3 reagents, as well as the emitted electron energy spectra. This paper presents a rationalization of all the experimental findings in a unifying picture to cast light on the basic chemical properties of Ng* under conditions of great relevance both from a fundamental and from an applied point of view. The importance of this investigation is that it isolates the selective role of the intermolecular halogen and hydrogen bonds, to assess their anisotropic effects on the stereodynamics of the promoted ionization reactions, and to model energy transfer and reactivity in systems of applied interest, such as planetary atmospheres, plasmas, lasers, and flames. 相似文献
145.
Andrea Ienco Maria Caporali Ferdinando Costantino Annalisa Guerri Gabriele Manca Simonetta Moneti 《Journal of Coordination Chemistry》2014,67(23-24):3863-3872
Given the ability of forming homomeric amide···amide dimer by iso-nicotinamide (nda), we postulate the existence of a hydrogen bond equivalent of the iso-reticular metal organic nanotubes (MONT) built by using copper, p,p′-diphenylmethylene-diphosphinate (pcp), and bipyridine. We obtained the desired primary arrangement of Cu/pcp/nda consisting of a 1-D chain. Instead of the expected amide/amide dimer, the NH2 groups were engaged in H-bonding networks with the phosphinate ligands in a series of 2-D slabs. The differences and the similarities of the Cu/pcp chains in known MONTs and in the reported structure are also highlighted. 相似文献
146.
Davide Corinti Gilles Frison Barbara Chiavarino Elisabetta Gabano Domenico Osella Maria Elisa Crestoni Simonetta Fornarini 《Angewandte Chemie (International ed. in English)》2020,59(36):15595-15598
Platinum(IV) complexes are extensively studied for their activity against cancer cells as potential substitutes for the widely used platinum(II) drugs. PtIV complexes are kinetically inert and need to be reduced to PtII species to play their pharmacological action, thus acting as prodrugs. The mechanism of the reduction step inside the cell is however still largely unknown. Gas‐phase activation of deprotonated platinum(IV) prodrugs was found to generate products in which platinum has a formal +3 oxidation state. IR multiple photon dissociation spectroscopy is thus used to obtain structural information helping to define the nature of both the platinum atom and the ligands. In particular, comparison of calculations at DFT, MP2 and CCSD levels with experimental results demonstrates that the localization of the radical is about equally shared between the dxz orbital of platinum and the pz of nitrogen on the amino group, the latter acting as a non‐innocent ligand. 相似文献
147.
M. Bonesini E. Bonvin P. S. L. Booth L. J. Carroll A. J. Cass D. Cavalli G. Cecchet G. Costa M. Donnat P. A. Dorsaz D. N. Edwards J. R. Fischer L. Fluri D. Frame F. Gianotti S. Jack J. N. Jackson M. Kelly M. N. Kienzle-Focacci R. Lucock J. G. Lynch L. Mandelli M. Martin L. Mathys A. Maxwell M. Mazzanti J. J. Myerscough P. J. Negus S. Pensotti-Rancoita L. Perini D. Perrin G. Polesello W. H. Range L. Rosselet S. W. Snow A. S. Thompson R. M. Turnbull J. Wells M. Werlen WA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1988,38(3):371-382
The inclusive cross sections for production of prompt photons and π0 s by 280 GeV/c protons incident on a liquid hydrogen target, have been measured forp T in the range 4.0 to 6.5 GeV/c and for |x F |<0.45. A quantitative comparison of the prompt photon cross section with next-to-leading order QCD predictions using Duke and Owens structure functions is performed. Phenomenological fits to the π0 and prompt photon cross sections are given. 相似文献
148.
Summary The optimisation of chromatographic parameters is studied. The Window Diagram and Overlapping Resolution Map (ORM) methods are compared. The latter is developed to take into account the spot diameter and the average plate height variations with the development distance, in order to improve the reliability of the method. 相似文献
149.
150.
The Ewig—van Wazer NOCOR pseudopotential scheme is sued, with minor modifications, in SCF MO calculations on the interaction of a hydrogen atom with clusters of up to four platinum atoms. The electronic structures of the clusters and the nature of the metal—hydrogen bond are investigated; the results are compared with those of extended Hückel theory for the same systems. 相似文献