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101.
Summary The aminoacid glutamine in aqueous solution and in conditions of high temperature and long term storage is partly transformed into pyroglutamic acid which exhibits potential neurotoxic effects.Commercially available aminoacid mixtures supplemented with glutamine are heat-sterilized and some losses of glutamine and formation of pyroglutamic acid may occur.The aim of the work was to set up an easy and reliable HPLC method which allows the determination of pyroglutamic acid as a degradation product of glutamine. The column was a 5 m Hypersil ODS (100×4.6 mm) and the mobile phase 100% 0.007 M phosphate buffer pH 3.5.Stability studies in different conditions of temperature and time of storage were performed on aminoacid mixture available in the commerce. 相似文献
102.
E. K. Starostin A. A. Mazurchik A. V. Ignatenko G. I. Nikishin 《Russian Chemical Bulletin》1993,42(7):1174-1178
The decomposition of 1,4-dihydroxy-1,4-dihydroperoxycyclohexane under the action of FeSO4 and the decomposition of 1,4-cyclohexanedione monoethyleneketal hydroperoxide under the action of FeII salts in the presence of various ligands or under the action of CuII sulfate have been studied. A preparative method for the synthesis of derivatives of diketodicarboxylic or -functionally substituted ketocarboxylic acids from 1,4-cyclohexanedione monoethyleneketal has been developed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1231–1235, July, 1993. 相似文献
103.
Lewis酸催化高区域选择合成对位柑菁醛的研究 总被引:4,自引:0,他引:4
Lewis酸催化高区域选择合成对位柑菁醛的研究尹笃林,银董红,李谦和(湖南师范大学精细催化合成研究所,长沙410081)关键词月桂烯,丙烯醛,对位柑菁醛,Diels-Alder反应,Lewis酸,络合催化。1.前言可从松节油资源中制取的月桂烯(myr... 相似文献
104.
Natalini B Marinozzi M Sardella R Macchiarulo A Pellicciari R 《Journal of chromatography. A》2004,1033(2):363-367
The chromatographic resolution of enantiomeric amino acids is accomplished on a reversed phase column using aqueous mobile phase containing the chiral reagent N,N-dimethyl-S-phenylalanine-Cu(II). The separation is a result of the whole interaction between the diastereomeric complex surface and the mixed stationary phase realized by the dynamic coating of the RP-18 carbon chains layer. The elution order seems to be related to the different water coordination capability on copper ion in the formation of the mixed ternary complexes. 相似文献
105.
Glass capillaries coated with Chirasil-Val, a chirally functionalised polysiloxane, are capable in principle of resolving all protein amino-acid enantiomers in a single run and within a short analysis time, thus allowing for example the quantitative amino acid determination by enantiomer labelling. The elution characteristics of the individual amino acids however are also dependent upon the chemical nature of the capillary wall surface, and a surface pretreatment is found to be necessary if all protein amino acids are to be analysed. Of the various methods of pretreatment tested, etching of borosilicate glass with gaseous HCl followed by deposition of colloidal silicic acid is considered to be the most suitable. 相似文献
106.
在非质子极性溶剂-二甲基乙酰胺中,室温下用碘乙烷与C_1—C_6脂肪酸及乳酸的四甲基铵盐反应制备各酸相应的乙酯。乙酯在15%的邻苯二甲酸二壬酯与6%的土温-80混合固定液填充柱上获得满意分离。用本法测定饮料酒中的低沸点有机酸含量,简便、快速、准确。 相似文献
107.
Andrea S.C. Fonseca 《Tetrahedron》2007,63(6):1353-1359
The synthesis and photochemistry of 3-oxo-3H-benzopyran derivatives linked through ester, anhydride, urethane and carbonate bonds to representative l-amino acids, at the amino and carboxylic acid groups at the main chain or the hydroxyl group at the side chain, were carried out. The stability to photolysis of the resulting conjugates was studied at different wavelengths of irradiation (254, 300 and 350 nm), the anhydride and ester linkages being the most sensitive in the studied conditions. 相似文献
108.
Structure determination of triglycerides according to their number of unsaturated fatty acids (N.U.F.A.) is more easily achieved after ozonolysis of their mixtures (fats and oils) than by capillary gas chromatographic analysis of the mixture as such. Analyses performed before and after ozonolysis of cocoa buttel, hazelnut oil, and a mixture of both fats illustrate the potential of this approach to the structure elucidation of triglycerides by chromatographic techniques. 相似文献
109.
José Luis Baeza 《Tetrahedron letters》2007,48(21):3689-3693
To investigate the ability of 2-alkyl-2-carboxy-azetidines (Azx) to induce reverse turns when incorporated into peptides, RCO-Azx-l-Ala-NHMe dipeptide derivatives were selected as simplified tetrapeptide models, in which the azetidine residue is incorporated at the i + 1 position. Molecular modelling, 1H NMR and FTIR studies showed the high tendency of the model tetrapeptides to adopt γ-turn conformations, indicating that these azetidine-containing amino acids could serve as general γ-turn promoters. 相似文献
110.
M. J. Medina-Hernández M. Catalá-Icardo M. C. García-Alvarez-Coque 《Chromatographia》1995,41(5-6):455-461
Summary Hydrophobic character is usually expressed in terms of the partition coefficient in 1-octanol-water (log Po/w). However, measurement of this coefficient is often problematic. Retention in micellar liquid chromatography is mainly due
to hydrophobic interactions and can also be used as an index of hydrophobicity. A hydrophobicity scale was established with
retention data foro-phthalaldehyde (OPA)-N-acetyl-L-cysteine (NAC) amino acid derivatives, using the glycine derivative as reference. Since the
OPA-NAC derivatives only differ in the nature of R1 in the amino acid (R1CH (COOH)NH2), in the absence of electrostatic interactions the hydrophobic character of the substituent was responsible for retention.
Linear relationships were obtained between log of the ratiok′ of amino acid derivatives:k′ of the glycine derivative for a given mobile phase, and logP
o/w for the R1 substituent. Good correlations were also found for phenylthiohydantoin amino acid derivatives. 相似文献