共查询到20条相似文献，搜索用时 0 毫秒
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Jennifer Ahrens Philip T. M. Carlsson Nils Hertl Prof. Dr. Matthias Olzmann Mark Pfeifle Dr. J. Lennard Wolf Dr. Thomas Zeuch 《Angewandte Chemie (International ed. in English)》2014,53(3):715-719
Recently, direct kinetic experiments have shown that the oxidation of sulfur dioxide to sulfur trioxide by reaction with stabilized Criegee intermediates (CIs) is an important source of sulfuric acid in the atmosphere. So far, only small CIs, generated in photolysis experiments, have been directly detected. Herein, it is shown that large, stabilized CIs can be detected in the gas phase by FTIR spectroscopy during the ozonolysis of β‐pinene. Their transient absorption bands between 930 and 830 cm?1 appear only in the initial phase of the ozonolysis reaction when the scavenging of stabilized CIs by the reaction products is slow. The large CIs react with sulfur dioxide to give sulfur trioxide and nopinone with a yield exceeding 80 %. Reactant consumption and product formation in time‐resolved β‐pinene ozonolysis experiments in the presence of sulfur dioxide have been kinetically modeled. The results suggest a fast reaction of sulfur dioxide with CIs arising from β‐pinene ozonolysis. 相似文献
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Vanessa M. Kung Gabriel Cornilescu Samuel H. Gellman 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(48):14544-14547
We have examined whether parallel β‐sheet secondary structure becomes more stable as the number of β‐strands increases, via comparisons among peptides designed to adopt two‐ or three‐stranded parallel β‐sheet conformations in aqueous solution. Our three‐strand design is the first experimental model of a triple‐stranded parallel β‐sheet. Analysis of the designed peptides by nuclear magnetic resonance (NMR) and circular dichroism (CD) spectroscopy supports the hypothesis that increasing the number of β‐strands, from two to three, increases the stability of the parallel β‐sheet. We present the first experimental evidence for cooperativity in the folding of a triple‐stranded parallel β‐sheet, and we show how minimal model systems may enable experimental documentation of characteristic properties, such as CD spectra, of parallel β‐sheets. 相似文献
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Yong‐beom Lim Eunji Lee Myongsoo Lee 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2007,119(19):3545-3548
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Hui Wang Janardan Kundu Naomi&#x;J. Halas 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2007,119(47):9198-9202
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Markus Leutzsch Alexander Roth Katrin Steinke Dieter Sicker Hans‐Ullrich Siehl Maximilian Schmid Klaus‐Peter Zeller Stefan Berger 《Chemie in Unserer Zeit》2013,47(6):344-354
3‐O‐Acetyl‐11‐keto‐β‐boswelliasäure was extracted from pulverized frankincense and purified by HPLC. All analytical spectra were recorded and are reproduced either in the main part or in the supporting information. The NMR‐ and mass‐spectra have been interpreted and compared with theoretical calculations of the 13C chemical shifts. The project is a follow up of the recent book “Classics in Spectroscopy” by S. Berger und D. Sicker (Wiley‐VCH 2009). 相似文献
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Duan‐Yen Lu Peter P.‐Y. Chen Ting‐Shen Kuo Yi‐Chou Tsai 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(31):9234-9238
Herein, we report the employment of the Mo Mo quintuple bonded amidinate complex to stabilize Group 10 metal fragments {(Et3P)2M} (M=Pd, Pt) and give rise to the isolation of the unprecedented δ complexes. X‐ray analysis unambiguously revealed short contacts between Pd or Pt and two Mo atoms and a slight elongation of the Mo Mo quintuple bond in these two compounds. Computational studies show donation of the Mo Mo quintuple‐bond δ electrons to an empty σ orbital on Pd or Pt, and back‐donation from a filled Pd or Pt dπ orbital into the Mo Mo δ* level (LUMO), consistent with the Dewar–Chatt–Duncanson model. 相似文献
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Ying Zhang Kun Jiang Yi‐Ming Zhai Jun‐Jie Tan Da‐Li Meng Sha‐Li Guo Shi‐Jin Qu Chang‐Heng Tan 《Helvetica chimica acta》2014,97(3):369-374
Chemical investigation of the MeOH extract of the leaves of Gynura procumbens (Lour .) Merr . afforded one new sesquiterpenoid, muurol‐4‐ene‐1β,3β,10β‐triol ( 1 ), and two sesquiterpene glycosides, muurol‐4‐ene‐1β,3β,10β‐triol 3‐O‐β‐D ‐glucopyranoside ( 2 ) and muurol‐4‐ene‐1β,3β,15‐triol 3‐O‐β‐D ‐glucopyranoside ( 3 ), together with three known sesquiterpenoids. Their structures were elucidated on the basis of spectroscopic analyses and chemical methods. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(8):2115-2118
The conformational heterogeneity of backbone N‐substituted peptides limits their ability to adopt stable secondary structures. Herein, we describe a practical synthesis of backbone aminated peptides that readily adopt β‐sheet folds. Data derived from model N‐amino peptides suggest that extended conformations are stabilized through cooperative steric, electrostatic, and hydrogen‐bonding interactions. 相似文献
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Jun Jiang Shaul Mukamel 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2010,122(50):9860-9863
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Sabrina Fischer Armin Geyer 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(15):3928-3933