نتایج جستجو برای: deuterium compounds
تعداد نتایج: 235130 فیلتر نتایج به سال:
The hyperpolarization (HP) method signal amplification by reversible exchange (SABRE) uses para-hydrogen to sensitize substrate detection by NMR. The catalyst systems [Ir(H)2(IMes)(MeCN)2(R)]BF4 and [Ir(H)2(IMes)(py)2(R)]BF4 [py = pyridine; R = PCy3 or PPh3; IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene], which contain both an electron-donating N-heterocyclic carbene and a phosphine, ...
Nucleophilic substitution reactions of Y-aryl methyl (8) and Y-aryl propyl (10) chlorothiophosphates with substituted anilines and deuterated anilines are investigated kinetically in acetonitrile at 55.0 C. A concerted mechanism is proposed for 8 based on the negative ρXY (= –0.23) value, while a stepwise mechanism with a rate-limiting leaving group departure from the intermediate is proposed f...
Deuterium enrichment of interstellar methanol is reproduced experimentally for the first time via grain-surface H-D substitution in solid methanol at an atomic D/H ratio of 0.1. Although previous gas-grain models successfully reproduce the deuterium enrichments observed in interstellar methanol molecules (D/H of up to 0.4, compared to the cosmic ratio of ∼10), the models exclusively focus on de...
To understand the mechanism of H–D exchange reaction for synthesizing various deuterium-labeled molecules on heterogeneous metal catalysts as a first step, we analyzed effects H/D isotopes adsorption H2O/D2O and their dissociated OH/OD species Pt(111) surface. We applied combined plane-wave localized basis set method developed by us to directly treat electronic structures surface adsorbed regio...
This study aimed to develop a menadione (MD) determination method employing liquid chromatography-tandem mass spectrometry (LC-MS/MS) using a pseudo multiple reaction monitoring (MRM) technique, wherein two quadrupoles are used to monitor the same ion. Detection limits of 40 and 2 pg were obtained for MD and its deuterium-labeled form, respectively, whereas MD intra- and inter-assay coefficient...
The Tagish Lake meteorite fell last year on a frozen lake in Canada and may provide the most pristine material of its kind. Analyses have now shown this carbonaceous chondrite to contain a suite of soluble organic compounds (approximately 100 parts per million) that includes mono- and dicarboxylic acids, dicarboximides, pyridine carboxylic acids, a sulfonic acid, and both aliphatic and aromatic...
Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition. Some organics are similar, but not identical, to those in interplanetary dust particles and carbonaceous meteorites. A class of aromatic-poor organic material is also present. The organics are rich in oxygen and nitrogen compared with meteoritic organics. Aromatic compou...
Deuterium/hydrogen exchange in combination with mass spectrometry (DH MS) is a sensitive technique for detection of changes in protein conformation and dynamics. Since temperature, pH and timing control are the key elements for reliable and efficient measurement of hydrogen/deuterium content in proteins and peptides, we have developed a small, semiautomatic interface for deuterium exchange that...
Many cellular proteins form oligomers. The equilibrium between monomeric and oligomeric states of these proteins is important for the regulation of protein activity. Modulation of the oligomerization equilibrium could be an interesting approach in the development of new therapeutic agents. This review summarizes information about protein oligomerization and modulation of this process, demonstra...
In analogy with the reaction of phenols very strong super acids, these compounds can be protonated by weaker acid trifluoroacetic (TFA) and trifluoromethanesulphonic (TFS) also giving rise to formation OH and/or ring products, which identified unambiguously means 1HNMR spectroscopy. The same reactions are possible deuterated acids TFA-d TFS-d. However, from reactions, additional information on ...
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