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排序方式: 共有120条查询结果,搜索用时 15 毫秒
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2.
Jäger D Seliger C Redpath NT Friedrich I Silber RE Pönicke K Werdan K Müller-Werdan U 《Electrophoresis》2000,21(13):2729-2736
Elongation factor 2 (EF-2) catalyses the last step of the elongation cycle, translocation, in the course of protein biosynthesis. A system for analyzing post-translational modifications of EF-2, which is a single polypeptide of 857 amino acids, is reported and its application to cytosolic extracts of cultured neonatal rat heart myocytes, neonatal and adult rat cardiac tissue, and extracts of human left ventricular myocardium is described. Comparing different pH ranges in immobilized pH gradient-isoelectric focusing (IPG-IEF), a range of pH 3 - 10 and 4 - 9 resulted in a highly defined and reproducible resolution of six different EF-2 variants of all extracts in the first dimension. These six variants were detected by the "imaging plate" (phosphor radiation image sensor) after specific labeling with Pseudomonas exotoxin A catalyzed [32P]ADP-ribosylation. This finding could be confirmed in Western blot analysis with a specific polyclonal rabbit antibody. Using two-dimensional polyacrylamide gel electrophoresis (2-D-PAGE), five to six EF-2 variants could be demonstrated in all extracts. By application of a second IPG indicator strip to the 2-D gel, they could be aligned with corresponding spots in a silver-stained 2-D separation of human myocardial tissue, revealing that the EF-2 variants belong to the group of low-abundance proteins. 相似文献
3.
Gunter Silber Dieter Flockerzi Rajendra Singh Varma Ramamurthy Charubala Eugen Uhlmann Wolfgang Pfleiderer 《Helvetica chimica acta》1981,64(5):1704-1716
Nucleotides. XV. Synthesis and Properties of 2′O-t-Butyldimethylsilyl-5′-O-monomethoxytritylribonucleoside-3′-phosphotriesters, Starting Materials for Oligonucleotide Syntheses The syntheses of two types of fully blocked ribonucleoside 3′-phosphotriesters 6–14 have been achieved in excellent yields from 2′-O-t-butyldimethylsilyl-5′-O-monomethoxytrityl-ribonucleosides 1–5 by phosphorylation with 2-chloro- and 2,5-dichlorophenylphosphorodichloridate respectively and subsequent treatment by cyanoethanol to 6 , 8 , 10 , 12 and 14 and by p-nitrophenylethanol to 7 , 9 , 11 and 13 . These phosphotriesters are valuable starting materials for oligonucleotide syntheses due to the fact that the corresponding phosphotriesters 15–23 with free HO? C(5′) could be obtained by detritylation and the 3′-phosphodiester triethylammonium salts 24–32 by deblocking of the cyanoethyl and the 2,5-dichlorophenyl group respectively. All newly synthesized compounds have been characterized by UV.-and NMR.-spectra as well as C, H, N elementary analyses. 相似文献
4.
The high sensitivity that can be attained using an enzymatic system and mediated by 4-tert-butylcatechol (4-TBC) has been verified by on-line interfacing of a rotating biosensor and continuous flow/stopped-flow/continuous-flow processing. Horseradish peroxidase, HRP, [EC 1.11.1.7], immobilized on a rotating disk, in presence of hydrogen peroxide catalyzed the oxidation of 4-TBC, whose back electrochemical reduction was detected on glassy carbon electrode surface at −150 mV. Thus, when penicillamine (PA) was added to the solution, these thiol-containing compounds participate in Michael type addition reactions with 4-TBC to form the corresponding thioquinone derivatives, decreasing the peak current obtained proportionally to the increase of its concentration. The highest response for PA was obtained around pH 7. This method could be used to determine PA concentration in the range 0.02-80 μM (r = 0.998). The determination of PA was possible with a limit of detection of 7 nM, in the processing of as many as 50 samples per hour. The HRP-rotating biosensor was successfully applied to the determination of PA in pharmaceutical formulations. 相似文献
5.
6.
An experimental study of the thermal decomposition of a β‐hydroxy alkene, 3‐methyl‐3‐buten‐1‐ol, in m‐xylene solution, has been carried out at five different temperatures in the range of 513.15–563.15 K. The temperature dependence of the rate constants for the decomposition of this compound in the corresponding Arrhenius equation is given by ln k (s?1) = (25.65 ± 1.52) ? (17,944 ± 814) (kJ·mol?1)·T?1. A computational study has been carried out at the M05–2X/6–31+G(d,p) level of theory to calculate the rate constants and the activation parameters by the classical transition state theory. There is a good agreement between the experimental and calculated rate constants and activation Gibbs energies. The bonding characteristics of reactant, transition state, and products have been investigated by the natural bond orbital analysis, which provides the natural atomic charges and the Wiberg bond indices. Based on the results obtained, the mechanism proposed is a one‐step process proceeding through a six‐membered cyclic transition state, being a concerted and slightly asynchronous process. The results have been compared with those obtained previously by us (Struct Chem 2013, 24, 1811–1816) for the thermal decomposition of 3‐buten‐1‐ol, in m‐xylene solution. We can conclude that in the compound studied in this work, 3‐methyl‐3‐buten‐1‐ol, the effect of substitution at position 3 by a weakly activating CH3 group is the stabilization of the transition state formed in the reaction and therefore a small increase in the rate of thermal decomposition. 相似文献
7.
Abstract Due to the wide use of polymers in medicine, researchers are required to solve a very important problem–to understand the interaction between materials of nonphysiological origin and the surrounding biological liquids, and tissues, particularly blood. 相似文献
8.
We exploit the approximate (broken) symmetries of time translation, time reversal, and Hamiltonian structure to obtain general scaling laws governing the process of pattern formation in weakly damped Faraday waves. Using explicit parameter symmetries we determine, for the case of two-frequency forcing, how the strength of observed three-wave interactions depends on the frequency ratio and on the relative phase of the two driving terms. These symmetry-based predictions are verified for numerically calculated coefficients, and help explain the results of recent experiments. 相似文献
9.
The nucleophilic aromatic substitution (S(N)Ar) reaction between 1-fluoro-2,4-dinitrobenzene and piperidine (PIP) were studied in two different reverse micellar interfaces: benzene/sodium 1,4-bis(2-ethylhexyl) sulfosuccinate (AOT)/water and benzene/benzyl-n-hexadecyl dimethylammonium chloride (BHDC)/water reverse micellar media. The kinetic profiles of the reactions were investigated as a function of variables such as surfactant and amine concentration and the amount of water dispersed in the reverse micelles, W0 = [H2O]/[surfactant]. In the AOT system at W0 = 0, no micellar effect was observed and the reaction takes place almost entirely in the benzene pseudophase, at every AOT and PIP concentration. At W0 = 10, a slight increment of the reaction rate was observed at low [PIP] with AOT concentration, probably due to the increase of micropolarity of the medium. However, at [PIP] > or = 0.07 M the reaction rates are always higher in pure benzene than in the micellar medium because the catalytic effect of the amine predominates in the organic solvent. In the BHDC system the reaction is faster in the micellar medium than in the pure solvent. Increasing the BHDC concentration accelerates the overall reaction, and the saturation of the micellar interface is never reached. In addition, the reaction is not base-catalyzed in this micellar medium. Thus, despite the partition of the reactants in both pseudophases the reactions effectively take place at the interface of the aggregates. The kinetic behavior can be quantitatively explained taking into account the distribution of the substrate and the nucleophile between the bulk solvent and the micelle interface. The results were used to evaluate the amine distribution constant between the micellar pseudophase and organic solvent and the second-order rate coefficient of S(N)Ar reaction in the interface. A mechanism to rationalize the kinetic results in both interfaces is proposed. 相似文献
10.
Silber C Günther S Marzok C Deh B Courteille PW Zimmermann C 《Physical review letters》2005,95(17):170408
We report on the observation of sympathetic cooling of a cloud of fermionic 6Li atoms which are thermally coupled to evaporatively cooled bosonic 87Rb. Using this technique we obtain a mixture of quantum-degenerate gases, where the Rb cloud is colder than the critical temperature for Bose-Einstein condensation and the Li cloud is colder than the Fermi temperature. From measurements of the thermalization velocity we estimate the interspecies s-wave triplet scattering length |amx|=20(+9)(-6)aB. We found that the presence of residual rubidium atoms in the |2, 1> and the |1, -1> Zeeman substates gives rise to important losses due to inelastic collisions. 相似文献