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1.
An attempt to link the heat of reaction obtained from analysis of UV spectra, bond energies deduced from crystallographic
data and calorimetric measurements of [bis(d-, l-, and dl-alaninato)diaqua] nickel(II) dihydrate complexes to theoretical values obtained from calculation is described. The heat of
reaction, which includes energy of ligand exchange in addition to crystal field stabilization energy of the three complexes,
was calculated from changes in spectral shifts, bond lengths, and free energy between nickel(II) ion and the d-, l-, and dl-alanine complexed nickel(II) ion in aqueous solution. These investigations were done by UV–visible spectroscopy, X-ray crystallography,
and isothermal calorimetry. The results reveal that the experimental heat of reaction based on the three mentioned parameters
is in good agreement with the theoretical value. The results are found to be of considerable interest in its linking of spectrochemical
quantities with thermodynamic functions. 相似文献
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Dipeptide l-methionyl-glycine (Met-Gly) hydrochloride was characterized structurally by means of solid-state linear polarized IR (IR-LD)
spectroscopy of oriented samples as colloidal suspension in nematic liquid crystal. Quantum chemical ab initio calculations and vibrational analysis support the experimental data. 1H and 13C nuclear magnetic resonance (NMR) data, mass spectrometry (ESI-MS and FAB-MS) techniques, thermogravimetry (TGV), and differential
scanning calorimetry (DSC) method were employed as well. The experimental and theoretical data of hydrochloride salt were
compared with analogous data of the neutral dipeptide with the aim to explain the role of intermolecular hydrogen bonding
on the conformational behavior and spectroscopic properties of the compound studied. 相似文献
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O. V. Statsenko S. N. Bolotin V. T. Panyushkin 《Russian Journal of General Chemistry》2004,74(8):1286-1288
Complexation of Cu(II) ions with L- and DL-threonine in aqueous solution was studied. Treatment of the ESR spectra of solutions containing Cu(II) and threonine in various ratios and having various pH, involving total line shape analysis, revealed formation of geometric isomers of the complex ions [Cu(thrH–1)2]2– differing in the mutual arrangement of the N and O atoms in the equatorial plane; the complexation and isomerization equilibrium constants were determined.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 8, 2004, pp. 1388–1391.Original Russian Text Copyright © 2004 by Statsenko, Bolotin, Panyushkin.This revised version was published online in April 2005 with a corrected cover date. 相似文献
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C. Pascali A. Bogni C. Cucchi L. Laera O. Crispu G. Maiocchi F. Crippa E. Bombardieri 《Journal of Radioanalytical and Nuclear Chemistry》2011,288(2):405-409
Samples of l-[S-methyl-11C]methionine prepared by on-column [11C]methylation on a C18 cartridge were analyzed by HPLC under different conditions in order to explain some anomalies observed
in the UV-chromatograms. By so doing, two new unlabelled impurities were found and identified as iodide and homocystine. Their
amounts are still compatible with the safe human use of the radiotracer solution. Nevertheless, if needed, iodide can be totally
removed by elution through an anion-exchange resin, while homocystine can be reduced by either decreasing the amount of precursor
used in the synthesis or preventing its air oxidation. 相似文献
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Anita Kovács I. Csóka Magdolna Kónya E. Csányi A. Fehér I. Erős 《Journal of Thermal Analysis and Calorimetry》2005,82(2):491-497
Summary The properties of the inner and the external aqueous phases, were studied in w/o/w multiple emulsions with light microscopic image analysis and differential scanning calorimetry (DSC). The importance of multiple
emulsions lies in the presence of these aqueous phases, making them available for sustained, controlled drug delivery systems.
Differentiation of these two aqueous phases, studying the effect of manufacturing technology on droplet structure, quantitative
determination of phase volumes and any changes occurring during storage are essential when planning w/o/w emulsions. The present study uses microscopic observations combined with DSC measurements in order to identify the formed
structure, at developmental stage in case of different components, preparation methods, and stirring rates. These tools are
beneficial during manufacturing as in process controls, or to ensure product quality. 相似文献
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The iodide hydrides NdI2H (1) and DyI2H (2) were obtained by the reactions of diiodides NdI2 (3) and DyI2 (4) with hydrogen at atmospheric pressure and temperature of 120–200 °C. Hydrolysis of products 1 and 2 gives hydrogen in a high yield. The reactions of 1 with phenol and of 2 with isopropyl alcohol in THF afford the iodide phenoxide NdI2(OPh)(THF)4 and iodide isopropoxide DyI2(OPri)(PriOH)3, respectively. The reaction of 2 with cyclopentadiene is accompanied by disproportionation and gives, besides dihydrogen, Cp2DyI(THF)2 and DyI3(THF)3.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1887–1889, October, 2007. 相似文献
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The enzymatic synthesis of three isotopomers of l-DOPA labeled with deuterium and tritium at α carbon atom was elaborated. These compounds were converted into [(1S)-2H]–, [(1S)-
3H]–, and doubly labeled [(1S)-2H/3H]-dopamines using enzyme tyrosine decarboxylase. Doubly labeled (1R) isotopologue, i.e., [(1R)-2H/3H]-dopamine, was afforded by enzymatic decarboxylation of authentic l-DOPA carried out in deuteriated and tritiated incubation medium. 相似文献
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I. V. Kulakov 《Chemistry of Natural Compounds》2009,45(4):522-524
Condensation of the monosaccharides D-glucose and D-galactose with synthesized halo-substituted p-phenylenediamines and 4-amino-2,6-dibromophenol was studied. It was found that glycosylation occurred only at the 4-amino
group that was sterically unhindered by the halogen atom. The position of the aglycon in the glycoside was established by
PMR spectroscopy. 相似文献
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L. M. Likhosherstov O. S. Novikova A. O. Zheltova V. N. Shibaev 《Russian Chemical Bulletin》2005,54(5):1294-1297
A series of nitrogen-containing physiologically active compounds underwent smooth N-monoalkylation with N-bromoacetyl-β-glycopyranosylamines derived from N-acetyl-D-glucosamine and lactose. This reaction was demonstrated to be promising for the introduction of carbohydrate residues into
heterocyclic compounds, viz., pyridine, imidazole, pyrimidinetrione, carboline, and piperazine derivatives, and into an amino acid, 5-hydroxy-L-tryptophan, which is unstable in alkaline media.
Dedicated to Academician N. K. Kochetkov on the occasion of his 90th birthday.
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Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1256–1259, May, 2005. 相似文献
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Aqueous solution of water soluble colloidal MnO2 was prepared by Perez-Benito method. Kinetics of l-methionine oxidation by colloidal MnO2 in perchloric acid (0.93 × 10−4 to 3.72 × 10−4 mol dm−3) has been studied spectrophotometrically. The reaction follows first-order kinetics with respect to [H+]. The first-order kinetics with respect to l-methionine at low concentration shifts to zero order at higher concentration. The effects of [Mn(II)] and [F−] on the reaction rate were also determined. Manganese (II) has sigmoidal effect on the rate reaction and act as auto catalyst.
The exact dependence on [Mn(II)] cannot be explained due to its oxidation by colloidal MnO2. Methionine sulfoxide was formed as the oxidation product of l-methionine. Ammonia and carbon dioxide have not been identified as the reaction products. The mechanism with the observed
kinetics has been proposed and discussed. 相似文献
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Nowduri Annapurna Adari Kalyan Kumar Parvataneni Vani Gollapalli Nageswara Rao 《Transition Metal Chemistry》2008,33(6):691-696
The kinetics of oxidation of l-cystine by MnIII have been studied in sulfuric acid medium at 30 °C. The reaction was followed spectrophotometrically at λmax = 500 nm. The
reaction shows first order dependence on both [MnIII] and [cystine]. It was found that the rate of the reaction decreases with increase of [H+] up to a certain point and then remains unchanged. The oxidation product of the reaction was found to be cysteic acid. A
plausible mechanism has been proposed to account for the experimental results. 相似文献