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101.
Patrick J. Whitham Dennis P. Strommen Sandra Lundell Lisa D. Lau Rene Rodriguez 《Plasma Chemistry and Plasma Processing》2014,34(4):755-766
The plasma enhanced chemical vapor depositions of germanium chalcogenide thin films from germanium tetrachloride, hydrogen sulfide and alkyl chalcogenides were studied to determine the viability of these reagents for thin film deposition. Hydrogen sulfide is a commonly used reagent for this technique and was used to determine optimal reaction conditions for thin film deposition. Germanium tetrachloride, alkylsulfides and alkylselenides were also employed because of their lower potential toxicities and higher availabilities compared to their more typical congeners: germane, hydrogen sulfide and hydrogen selenide in the formation of germanium chalcogenides. Alkylsulfides were found to be unsuitable for the deposition of germanium sulfides, however alkylselenide precursors were used successfully for the deposition of germanium selenides. The relative mass flow rates, reactor pressure, substrate temperature and plasma power density were studied for their effects on germanium chalcogenide deposition. These parameters affected the composition, deposition rate, film quality, and spectroscopic properties of the deposited films. 相似文献
102.
Laura Köttner Dr. Monika Schildhauer Dr. Sandra Wiedbrauk Dr. Peter Mayer Prof. Dr. Henry Dube 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(47):10712-10718
The photophysical and photochemical properties of sulfoxide and sulfone derivatives of hemithioindigo photoswitches are scrutinized and compared to the unoxidized parent chromophores. Oxidation results in significantly blue-shifted absorptions and mostly reduction of photochromism while thermal stabilities of individual isomers remain largely unaltered. Effective photoswitching takes place at shorter wavelengths compared to parent hemithioindigos and high isomeric yields can be obtained reversibly in the respective photostationary states. Reversible solid-state photoswitching is observed for a twisted sulfone derivative accompanied by visible color changes. These results establish oxidized hemithioindigo photoswitches as promising and versatile tools for robust light-control of molecular behavior for a wide range of applications. 相似文献
103.
Sandra Mller Stefan Barwe Justus Masa Daniela Wintrich Sabine Seisel Helmut Baltruschat Wolfgang Schuhmann 《Angewandte Chemie (International ed. in English)》2020,59(4):1585-1589
Carbon corrosion at high anodic potentials is a major source of instability, especially in acidic electrolytes and impairs the long‐term functionality of electrodes. In‐depth investigation of carbon corrosion in alkaline environment by means of differential electrochemical mass spectrometry (DEMS) is prevented by the conversion of CO2 into CO32?. We report the adaptation of a DEMS system for online CO2 detection as the product of carbon corrosion in alkaline electrolytes. A new cell design allows for in situ acidification of the electrolyte to release initially dissolved CO32? as CO2 in front of the DEMS membrane and its subsequent detection by mass spectrometry. DEMS studies of a carbon‐supported nickel boride (NixB/C) catalyst and Vulcan XC 72 at high anodic potentials suggest protection of carbon in the presence of highly active oxygen evolution electrocatalysts. Most importantly, carbon corrosion is decreased in alkaline solution. 相似文献
104.
Daouda Ndiaye Maryame Sy Agns Pallier Sandra Même Isidro de Silva Sara Lacerda Aline M. Nonat Loïc J. Charbonnire va Tth 《Angewandte Chemie (International ed. in English)》2020,59(29):11958-11963
The search for more biocompatible alternatives to Gd3+‐based MRI agents, and the interest in 52Mn for PET imaging call for ligands that form inert Mn2+ chelates. Given the labile nature of Mn2+, high inertness is challenging to achieve. The strongly preorganized structure of the 2,4‐pyridyl‐disubstituted bispidol ligand L1 endows its Mn2+ complex with exceptional kinetic inertness. Indeed, MnL1 did not show any dissociation for 140 days in the presence of 50 equiv. of Zn2+ (37 °C, pH 6), while recently reported potential MRI agents MnPyC3A and MnPC2A‐EA have dissociation half‐lives of 0.285 h and 54.4 h under similar conditions. In addition, the relaxivity of MnL1 (4.28 mm ?1 s?1 at 25 °C, 20 MHz) is remarkable for a monohydrated, small Mn2+ chelate. In vivo MRI experiments in mice and determination of the tissue Mn content evidence rapid renal clearance of MnL1. Additionally, L1 could be radiolabeled with 52Mn and the complex revealed good stability in biological media. 相似文献
105.
Cem B. Yildiz Kinga I. Leszczyska Sandra Gonzlez‐Gallardo Michael Zimmer Akin Azizoglu Till Biskup Christopher W. M. Kay Volker Huch Henry S. Rzepa David Scheschkewitz 《Angewandte Chemie (International ed. in English)》2020,59(35):15087-15092
Main group analogues of cyclobutane‐1,3‐diyls are fascinating due to their unique reactivity and electronic properties. So far only heteronuclear examples have been isolated. Here we report the isolation and characterization of all‐silicon 1,3‐cyclobutanediyls as stable closed‐shell singlet species from the reversible reactions of cyclotrisilene c‐Si3Tip4 (Tip=2,4,6‐triisopropylphenyl) with the N‐heterocyclic silylenes c‐[(CR2CH2)(NtBu)2]Si: (R=H or methyl) with saturated backbones. At elevated temperatures, tetrasilacyclobutenes are obtained from these equilibrium mixtures. The corresponding reaction with the unsaturated N‐heterocyclic silylene c‐(CH)2(NtBu)2Si: proceeds directly to the corresponding tetrasilacyclobutene without detection of the assumed 1,3‐cyclobutanediyl intermediate. 相似文献
106.
The elution order of the hop α- and β-acids has been studied under different modes of electrokinetic separation. A model is advanced to explain the shorter migration times of the more hydrophobic β-acids compared to the α-acids in micellar electrokinetic chromatography (MEKC). For quality control of the bitter principles in hops, the ruggedness of electrokinetic separation could be improved by replacing MEKC by microemulsion electrokinetic chromatography (MEEKC). 相似文献
107.
108.
Off-line SFE-CGC-ECD analysis of 2,4-D and Dicamba residues in real sugar cane,rice and corn samples
Fernando M. Lanas Sandra R. Rissato Antonio A. Mozeto 《Journal of separation science》1996,19(10):564-568
Determination of 2,4-D (2,4-dichlorophenoxyacetic acid) and Dicamba (2-methoxy-3,6-dichlorobenzoic acid) residues in sugar cane, rice, and corn was carried out both by solid liquid extraction (SLE), as already described in the literature, and by a supercritical fluid extraction (SFE) method developed in our laboratory. The extracts were esterified and cleaned-up by passing through a Florisil column. Extracts were analyzed by high resolution gas chromatography, with electron capture detection. The tested methods presented good recoveries (above 90%); the SFE CO2/acetone method showed better extraction efficiencies (extracted 30 % more herbicide in real samples), shorter extraction time and lower organic solvent consumption than the SLE method. 相似文献
109.
Microwave-assisted acid hydrolysis of proteins combined with liquid chromatography MALDI MS/MS for protein identification 总被引:4,自引:0,他引:4
Simple and efficient digestion of proteins, particularly hydrophobic membrane proteins, is of significance for comprehensive proteome analysis using the bottom-up approach. We report a microwave-assisted acid hydrolysis (MAAH) method for rapid protein degradation for peptide mass mapping and tandem mass spectrometric analysis of peptides for protein identification. It uses 25% trifluoroacetic acid (TFA) aqueous solution to dissolve or suspend proteins, followed by microwave irradiation for 10 min. This detergent-free method generates peptide mixtures that can be directly analyzed by liquid chromatography (LC) matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS) without the need of extensive sample cleanup. LC-MALDI MS/MS analysis of the hydrolysate from 5 microg of a model transmembrane protein, bacteriorhodopsin, resulted in almost complete sequence coverage by the peptides detected, including the identification of two posttranslational modification sites. Cleavage of peptide bonds inside all seven transmembrane domains took place, generating peptides of sizes amenable to MS/MS to determine possible sequence errors or modifications within these domains. Cleavage specificity, such as glycine residue cleavage, was observed. Terminal peptides were found to be present in relatively high abundance in the hydrolysate, particularly when low concentrations of proteins were used for MAAH. It was shown that these peptides could still be detected from MAAH of bacteriorhodopsin at a protein concentration of 1 ng/microl or 37 fmol/microl. To evaluate the general applicability of this method, it was applied to identify proteins from a membrane protein enriched fraction of cell lysates of human breast cancer cell line MCF7. With one-dimensional LC-MALDI MS/MS, a total of 119 proteins, including 41 membrane-associated or membrane proteins containing one to 12 transmembrane domains, were identified by MS/MS database searching based on matches of at least two peptides to a protein. 相似文献
110.
Hairy roots of Brugmansia candida produce the tropane alkaloids scopolamine and hyoscyamine. In an attempt to divert the carbon flux from competing pathways
and thus enhance productivity, the polyamine biosynthesis inhibitors cyclohexylamine (CHA) and methylglyoxal-bis-guanylhy,
drazone (MGBG) and the phenylalamine-ammonia-lyase inhibitor cinnamic acid were used. CHA decreased the specific productivity
of both alkaloids but increased significantly the release of scopolamine (approx 500%) when it was added in the mid-exponential
phase. However, when CHA was added for only 48 h during the exponential phase, the specific productivity of both alkaloids
increased (approx 200%), favoring scopolamine. Treatment with MGBG was detrimental to growth but promoted release into the
medium of both alkaloids. However, when it was added for 48 h during the exponential phase, MGBG increased the specific productivity
(approx 200%) and release (250–1800%) of both alkaloids. Cinnamic acid alone also favored release but not specific productivity.
When a combination of CHA or MGBG with cinnamic acid was used, the results obtained were approximately the same as with each
polyamine biosynthesis inhibitor alone, although to a lesser extent. Regarding root morphology, CHA inhibited growth of primary
roots and ramification. However, it had a positive effect on elongation of lateral roots. 相似文献