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41.
A. B. Mirgorodskaya F. G. Valeeva L. A. Kudryavtseva N. N. Vylegzhanina Yu. F. Zuev 《Russian Journal of General Chemistry》2006,76(4):590-595
A kinetic study of reactions of carboxylic acid esters with phenols activated with alkalis or amines in microemulsions based on cationic surfactants showed that the phenolates formed upon activation exhibit different nucleophilicity depending on the value of the negative charge on the oxygen atom, which is determined by the properties of the phenol, ionizing agent, and solvent. 相似文献
42.
Mirgorodskaya A. B. Kudryavtseva L. A. Zuev Yu. F. Idiyatullin B. Z. Fedotov V. D. 《Russian Journal of General Chemistry》2002,72(7):1007-1011
The parameters determining the structure and properties (surface potential and size of microdrops) of oil-water microemulsions containing various surfactants, and also the distribution of components between the dispersed phase and dispersing medium were determined by the kinetic method and by high-resolution 1H NMR spectroscopy with a pulse magnetic field gradient. 相似文献
43.
A. B. Mirgorodskaya F. G. Valeeva S. S. Lukashenko E. I. Yatskevich L. Ya. Zakharova A. I. Konovalov 《Kinetics and Catalysis》2012,53(2):206-213
Use of aqueous micellar solutions of dicationic surfactants with the general formula [R(CH3)2N(CH2)6N(CH3)2R]2+2Br− (R = n-C10H21 to n-C16H33) as the reaction medium for the alkaline hydrolysis of phosphonic acid esters has revealed a strong catalytic effect of the
surfactants, which can increase the reaction rate by two orders of magnitude. This effect depends on the surfactant structure,
shows itself at low surfactant concentrations, and is substrate-specific. The effect of the micelles on the phosphonate hydrolysis
rate is largely determined by the hydrophobicity factor. 相似文献
44.
Mirgorodskaya E O'Connor PB Costello CE 《Journal of the American Society for Mass Spectrometry》2002,13(4):318-324
Sustained off resonance irradiation (SORI) collision-induced dissociation (CID) is a commonly used method of collisionally activating ions for fragmentation in Fourier transform mass spectrometric experiments. To achieve the degree of fragmentation desired, both the irradiation frequency and amplitude must be optimized. This is a time-consuming procedure, particularly when the m/z values of the precursor ions vary over a broad range. We present an approach that simplifies this optimization by precalculating the irradiation frequency of the ions to be fragmented as a constant percentage of the reduced cyclotron frequency. Using this approach, the optimal amplitude was found to be significantly less dependent on the m/z value of the precursor ion, and therefore required little or no adjustment. This method considerably simplified optimization of SORI-CID for analysis of carbohydrates, glycoconjugates, and peptides over the mass range m/z 300-3500, requiring optimization of only a single experimental parameter, the irradiation amplitude, and only for the first MS/MS stage. 相似文献
45.
The formation of surfactant-hydrophobic amine mixed aggregates reduces the pK a of long-chain amines by 1–1.5 units compared with those in molecular solutions and is an important factor responsible for the high catalytic effect of the system in ester bond cleavage. In aqueous solution of geminal surfactants, the rate of azomethine formation in the reaction of long-chain amines with benzaldehydes is an order-of-magnitude higher than in ethanol. 相似文献
46.
A. B. Mirgorodskaya N. S. Erzikova L. A. Kudryavtseva A. I. Konovalov 《Russian Chemical Bulletin》2006,55(10):1788-1793
The pK
a values and constants of tautomeric equilibrium of several o-aminomethylphenols with different hydrophilic-lipophilic ability were measured in aqueous micellar solutions and in direct
microemulsions based on cetyltrimethylammonium bromide. The kinetics of hydrolysis of p-nitrophenyl acetate at different pH and concentrations of aminomethylphenol and surfactant was studied.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1724–1729, October, 2006 相似文献
47.
Gobom J Nordhoff E Mirgorodskaya E Ekman R Roepstorff P 《Journal of mass spectrometry : JMS》1999,34(2):105-116
A simple reversed-phase nano-column purification and sample preparation technique is described, which markedly improves the mass spectrometric analysis of complex and contaminated peptide mixtures by matrix-assisted laser desorption/ionization (MALDI). The method is simple, fast and utilizes only low-cost disposables. After loading the sample on the column and a subsequent washing step, the analyte molecules are eluted with 50-100 nl of matrix solution directly on to the MALDI/MS target. The washing step ensures removal of a wide range of contaminants. The small bed volume of the column allows efficient sample concentration and the elution process yields very small sample spots. This simplifies the analysis and minimizes discrimination effects due to sample heterogeneity, because the desorption/ionization laser simultaneously irradiates a large portion of the sample. Taken together, these features of the method significantly improve the sensitivity for MALDI/MS analysis of contaminated peptide samples compared with the commonly used sample preparation procedures. This is demonstrated with in-gel tryptic digests of proteins from human brain that were separated by 2D gel electrophoresis. Furthermore, it is shown that with this method 2,5-dihydroxybenzoic acid (DHB) acts as an efficient matrix for peptide mapping. Both detection sensitivity and sequence coverage are comparable to those obtained with the currently preferred matrix alpha-cyano-4-hydroxycinnamic acid (CHCA). The higher stability of peptide ions generated with DHB compared with CHCA is advantageous when analyzing fragile sample molecules. Therefore, the method described here is also of interest for the use of Fourier transform ion cyclotron resonance (FT-ICR) or ion-trap mass analyzers. 相似文献
48.
Mirgorodskaya OA Haselmann KF Kjeldsen F Zubarev RA Roepstorff P 《European journal of mass spectrometry (Chichester, England)》2003,9(2):139-148
Potentially biologically-active nanostructures can be created from single chains of unmodified peptides by cross-linking different regions of the chain by disulfide bonds and cleaving the chain at specified sites to obtain the final configuration. The availability of techniques for assembly and characterization of such structures was tested on a two-loop structure created from a 21-residue linear peptide. Directed intra-molecular disulfide bond formation was performed by inserting partial sequences favoring intra-molecular SS bond formation ("loops") separated by partial sequences disfavoring such a process ("spacers") into the precursor sequence. Peptide bond cleavage by partial acid hydrolysis at specific sites (GG, NP/DP) inside the loops opened them; the same process in the spacer separated the loops. Synthesis, oxidation and bond cleavage were monitored by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI ToF MS). The hydrolysis fragments of the produced nanostructures were characterized by tandem electrospray ionization Fourier transform mass spectrometry (ESI FT-MS) with collisional and electron capture dissociations. The latter technique was especially useful as it cleaves SS bonds preferentially. The feasibility of the proposed synthesis approach and the adequacy of the analysis techniques for the test structure were demonstrated. 相似文献
49.
R. A. Shagidullina L. A. Kudryavtseva A. B. Mirgorodskaya L. Ya. Zakharova B. E. Ivanov 《Russian Chemical Bulletin》1990,39(5):1010-1013
Cetylpyridinium bromide micelles accelerate the reaction of paranitrophenyldiphenyl phosphate with orthoaminomethylphenol by more than an order of magnitude in aqueous micellar solutions. The rate constants for this reaction are, however, about 50 times lower in the micellar phase than in water, i.e., the principal factor responsible for micellar catalysis in this reaction is concentration of the reagent.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1126–1129, May, 1990. 相似文献
50.
The possibilities of using “oil-water” type microemulsions as a medium for reactions of nucleophilic substitution in esters have been considered. The kinetics of the reactions ofp-nitrophenyl acetate and caprylate with primary amines in the medium indicated has been studied. The hydrophoby factor, being of great importance for micellar solutions of surfactants, is not substantially manifested in detergent microemulsions: the rate constants of the reactions studied are in fact independent of the length of the alkyl radical of the nucleophile. 相似文献