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Letzel MC Schäfer C Novara FR Speranza M Rozhenko AB Schoeller WW Mattay J 《Journal of mass spectrometry : JMS》2008,43(11):1553-1564
The displacement processes of several guests, incorporated in a calixarene host system, were investigated in the gas phase by electrospray ionization-Fourier transform-ion cyclotron resonance (ESI-FT-ICR) mass spectrometry. The complexes resulting from a resorcin[4]arene host with ammonia and sec-butylamine guests were isolated in an ICR-cell, separately using both states of the photoswitch as well as two reference systems for the open and closed forms of the photoswitchable host. The isolated complexes were forced to exchange the guest by using methylamine, ethylamine and sec-butylamine, resulting in different reaction rates for all the measured systems. Especially, the reaction rates of both states of the photoswitch are dependent on the provided guest. Potential side effects like proton exchanges were examined by an H/D-exchange experiment. The results were investigated and supported by quantum chemical calculations (DFT). 相似文献
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Rozhenko AB Schoeller WW Letzel MC Decker B Agena C Mattay J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(35):8995-9000
Host-guest complexes of tetramethylcavitand with different ammonium cations were investigated by using a quantum chemical method at the density functional level (BP86, B3 LYP). The NH4+ cation is strongly bound to the host. Increasing methyl substitution at the cation decreases its inclination towards the complex formation. The calculated data are in line with results from electrospray ionization mass spectrometry (ESI-MS) experiments. They reveal stable aggregates only for the NH4+ cation and for the primary alkylammonium cations. 相似文献
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Caterina Fraschetti Matthias C. Letzel Marlene Paletta Jochen Mattay Maurizio Speranza Antonello Filippi Massimiliano Aschi Alexander B. Rozhenko 《Journal of mass spectrometry : JMS》2012,47(1):72-78
The effect of cyclochirality of rccc‐2,8,14,20‐tetra‐n‐decyl‐4,10,16,22‐tetra‐O‐methylresorcin[4]arene (C) on the enantiodiscrimination of a number of chiral bidentate and tridentate aromatic and aliphatic biomolecules (G) has been investigated by nano‐electrospray ionization (nano‐ESI)‐Fourier transform ion cyclotron resonance mass spectrometry. The experimental approach is based on the formation of diastereomeric proton‐bound [C·H·G]+ complexes by nano‐ESI of solutions containing an equimolar amount of quasi‐enantiomers (C) together with the chiral guest (G) and the subsequent measurement of the rate of the G substitution by the attack of several achiral and chiral amines. In general, the heterochiral complexes react faster than the homochiral ones, except when G is an aminoalcoholic neurotransmitter whose complexes, beyond that, exhibit the highest enantioselectivity. The kinetic results were further supported by both collision‐induced dissociation experiments on some of the relevant [C2·H·G]+ three‐body species and Density functional theory (DFT) calculations performed on the most selective systems. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Morelos A Albuquerque IF Bondar NF Carrigan RA Chen D Cooper PS Dai Lisheng Denisov AS Dobrovolsky AV Dubbs T Endler AM Escobar CO Foucher M Golovtsov VL Gottschalk H Gouffon P Grachev VT Khanzadeev AV Kubantsev MA Kuropatkin NP Lach J Lang Pengfei Li Chengze Li Yunshan Luksys M Mahon JR McCliment E Newsom C Pommot Maia MC Samsonov VM Schegelsky VA Shi Huanzhang Smith VJ Tang Fukun Terentyev NK Timm S Tkatch II Uvarov LN Vorobyov AA Yan Jie Zhao Wenheng Zheng Shuchen Zhong Yuanyuan 《Physical review letters》1993,71(14):2172-2175
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Toni Neuwirth Dr. Anne-Catrin Letzel Cedric Tank Dr. Keishi Ishida Michael Cyrulies Dr. Lisa Schmölz Prof. Dr. Stefan Lorkowski Prof. Dr. Christian Hertweck 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(68):15855-15858
The anaerobe Clostridium acetobutylicum belongs to the most important industrially used bacteria. Whereas genome mining points to a high potential for secondary metabolism in C. acetobutylicum, the functions of most biosynthetic gene clusters are cryptic. We report that the addition of supra-physiological concentrations of cysteine triggered the formation of a novel natural product, clostrisulfone ( 1 ). Its structure was fully elucidated by NMR, MS and the chemical synthesis of a reference compound. Clostrisulfone is the first reported natural product with a diphenylsulfone scaffold. A biomimetic synthesis suggests that pentamethylchromanol-derived radicals capture sulfur dioxide to form 1 . In a cell-based assay using murine macrophages a biphasic and dose-dependent regulation of the LPS-induced release of nitric oxide was observed in the presence of 1 . 相似文献
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Alexander B. Rozhenko Wolfgang W. Schoeller Matthias C. Letzel Bjrn Decker Ceno Agena Jochen Mattay 《Journal of Molecular Structure》2005,732(1-3):7-20
A variety of conformations for three model calix[4]arenes with 8 or 12 OH groups have been investigated by calculations at density functional (RI-BP86) and RI-MP2 level of approximation. The calixarenes form stable complexes with the alkali metal cations of lithium up to caesium. For the investigations all-valence electron basis sets as well as various effective core potentials were probed. The stabilities of complexes were analysed in comparison with the corresponding benzene complexes, M+·C6H6. The formation of the calixarene metal complexes is considered in two steps, (a) in a distortion from the equilibrium conformation of the free calixarenes and (b) subsequent complexation. The distortion energies are small for the ‘crown’ and larger for the ‘boat’ conformations. On the other hand the latter are more stabilized by significant interaction energy of the cation with two adjacent π-systems of the aromatic rings. As a result, these two conformations are of similar stabilities for K+ to Cs+ complexes with resorc[4]arenes, with a slight advantage for the ‘boat’ structure. The most stable conformation for the coordination products of these cations with the calix[4]arene with 12 OH groups is a slightly flattened ‘crown’ that is derived by maximum hydrogen bonding of the OH-groups and the most effective cation-π interactions. Special cases are complexes of Li+ and Na+ which in most instances prefer the coordination on the oxygen atoms of the upper rim of the calixarene cavities and thus form ‘boat’-like structures. 相似文献
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Johanna Gra?mann Romy K. Scheerle Thomas Letzel 《Analytical and bioanalytical chemistry》2012,402(2):625-645
This review covers recent developments in mass spectrometry-based applications dealing with functional proteomics with special
emphasis on enzymology. The introduction of mass spectrometry into this research field has led to an enormous increase in
knowledge in recent years. A major challenge is the identification of “biologically active substances” in complex mixtures.
These biologically active substances are, on the one hand, potential regulators of enzymes. Elucidation of function and identity
of those regulators may be accomplished by different strategies, which are discussed in this review. The most promising approach
thereby seems to be the one-step procedure, because it enables identification of the functionality and identity of biologically
active substances in parallel and thus avoids misinterpretation. On the other hand, besides the detection of regulators, the
identification of endogenous substrates for known enzymes is an emerging research field, but in this case studies are quite
rare. Moreover, the term biologically active substances may also encompass proteins with diverse biological functions. Elucidation
of the functionality of those—so far unknown—proteins in complex mixtures is another branch of functional proteomics and those
investigations will also be discussed in this review. 相似文献