N-quaternary compounds—XXVIII : Circular dichroism of α-trimethylammonium acids

The dichroic absorption of α-trimethylammonium carboxylic acids has been compared with that of α-amino acids. The quaternary acids were synthesized by methylation of amino acids or by the Menschutkin reaction between bromo acids and trimethylamine. The stereochemical course in the Menschutkin reaction is discussed. Rate of racemisation in alkaline solution of the synthesized quaternary acids has been determined.     

黑蚂蚁的脂肪酸及抗氧化性能的分析

对黑蚂蚁中脂肪酸的组成和含量进行测定。采用索氏提取法提取其脂肪酸,再进行甲酯化处理,以气相色谱-质谱联用仪进行了分离和鉴定。由黑蚂蚁中分离鉴定出11种脂肪酸,占脂肪酸总量的99.78%,不饱和脂肪酸占脂肪酸总量的80.65%,饱和脂肪酸占脂肪酸总量的19.13。通过流动注射化学发光法分析了黑蚂蚁的抗氧化性能,结果表明,黑蚂蚁具有较强的抗氧化性能。     

银环蛇蛇蜕的化学成分研究Ⅱ . 脂肪酸和氨基酸组分

用色谱－质谱（GC－MS）联用技术分析了银环蛇蛇蜕的脂肪酸成分,鉴定出36种脂肪酸（饱和酸28种不饱和酸8种）,在蛇蜕中发现16种饱和二元酸,并发现了自然界中少见的奇数碳脂肪酸14种及支链酸2种,用氨基酸自动分析仪测定了蛇蜕水提取液中的13种游离氨基酸,酸性水解液中17种氨基酸,在蛇蜕中发现存在牛 磺酸。     

Basic profiles of organic acids in urine

Altogether 143 of the organic acids regularly occurring in urine of healthy individuals are identified as methyl esters by gas chromatography-mass spectrometry with respect to their complete chemical structures. They are classified as dicarboxylic acids, oxocarboxylic acids, hydroxycarboxylic acids, aromatic acids, furancarboxylic acids, nitrogen-containing acids and acid conjugates. By pre-fractionating the complex mixture of the total organic acids, peak overlap is minimized, and substances in low concentrations can also be detected and identified. The qualitative patterns of the urinary organic acids in the fractions are constant and reproducible, and in many cases a reliable identification of organic acids is possible by gas chromatography alone, using methylene units and separation on OV-1701 capillary columns.     

小鼠眼球中脂肪酸的组成分析

首次对小鼠眼球中的脂肪酸组成进行了气相色谱分析。小鼠眼球中的脂肪酸经氯仿－甲醇－盐酸混合液萃取,用甲醇－氢氧化钾法甲酯化,在２５ｍ×０．２５ｍｍＰＥＧ－２０Ｍ熔融石英毛细管柱内进行分离,眼球中１２种主要脂肪酸得到了定性和定量。测试结果提示：正常小鼠眼球中饱和脂肪酸含量较高,占全部脂肪酸含量的５２．８％;不饱和脂肪酸含量较少,但以多不饱和脂肪酸居多,占全部脂肪酸含量的１８．２％,不饱和脂肪酸与饱和脂肪酸的比值为０．６。可为有关眼疾病的治疗、预防及生化方面的深入研究提供有意义的信息。     

Enzymatic fluorimetric determination of the individual bile acids in blood serum

An enzymatic fluorimetric method is described for the determination of total bile acids (cholic acid and deoxycholic acid), primary bile acids (cholic and chen acids and individual bile acids in serum without prior separation of the acids. Total and primary bile acids are determined by equilibrium procedures by conver of the 3α- and 7α-hydroxy bile acids to 3-oxo and 7-oxo bile acids by α-NAD⁺, in the presence of 3α- and 7α-hydroxysteroid dehydrogenase (HSD), respectively, and measurement of the generated NADH fluorimetrically. Chenodeoxycholic acid is determined with 7α-HSD in the presence of cholic and deoxycholic acids by a differential kinetic procedure, and cholic and deoxycholic acids are calculated by difference. Interferents are removed by treatment of serum with Sachrom rein. Only 1.00 ml of serum is required. Low cost, simplicity and reliability are the main features of the method. The recovery of bile acids added to serum averaged 103% (range 83–122%). The method is suitable for routine use in small clinical laboratories.     

五氯化磷辅助下氨基酸的自组装成肽反应研究

L-α-氨基酸和D-α-氨基酸可与五氯化磷直接发生磷酰化反应，随后自组装成多肽，但β-氨基酸不能成肽，DL-α-氨基酸成肽困难；在SOCl2存在下，α-氨基酸也不能成肽，用电喷雾质谱研究了氨基酸的自组装反应，反应过程中有五元环状的氨基酸五配位磷中间体生成，使用硅烷基保护的氨基酸，在^31PNMR中可观察到五配位磷中间体。     

植物油中脂肪酸不同定量方法的比较分析

比较峰面积归一化法与标准曲线法两种方法分析植物油中脂肪酸百分比含量的差异.利用气相色谱-质谱联用仪(GC-MS)检测10种市售食用植物油中的8种主要脂肪酸,峰面积归一化法和标准曲线法计算脂肪酸的百分比含量.结果表明,标准曲线法与峰面积归一化法相比,肉豆蔻酸、棕榈酸、十七烷酸、硬脂酸和棕榈油酸所占的百分比升高,而油酸、亚...     

Profiling and characterisation by liquid chromatography/multi-stage mass spectrometry of the chlorogenic acids in Gardeniae Fructus

The chlorogenic acids of Gardeniae Fructus used traditionally as a Chinese herbal medicine (zhizi) have been investigated qualitatively by liquid chromatography/multi-stage mass spectrometry (LC/MS(4)). Twenty-nine chlorogenic acids were detected and twenty-five characterised to regioisomer level on the basis of their fragmentation, twenty-four for the first time from this source. Assignment to the level of individual regioisomers was possible for three caffeoylquinic acids, three dicaffeoylquinic acids, three sinapoylquinic acids, four caffeoyl-sinapoylquinic acids, two feruloyl-sinapoylquinic acids, one p-coumaroyl-sinapoylquinic acid, three (3-hydroxy, 3-methyl)glutaroylquinic acids, two (3-hydroxy, 3-methyl)glutaroyl-feruloylquinic acids, one (3-hydroxy, 3-methyl)glutaroyl-dicaffeoylquinic acid, and one (3-hydroxy, 3-methyl)glutaroyl-caffeoyl-feruloylquinic acid. Six (3-hydroxy, 3-methyl)glutaroyl-caffeoylquinic acids were detected and two were tentatively assigned as 3-caffeoyl-4-(3-hydroxy, 3-methyl)glutaroylquinic acid and 3-caffeoyl-5-(3-hydroxy, 3-methyl)glutaroylquinic acid. The (3-hydroxy, 3-methyl)glutaroyl residue modifies the mass spectral fragmentation behavior and elution sequence compared with the chlorogenic acids that contain only a cinnamic acid residue(s). Fourteen of these twenty-nine chlorogenic acids have not previously been reported from any source.     

Identification of individual acids in a commercial sample of naphthenic acids from petroleum by two-dimensional comprehensive gas chromatography/mass spectrometry

The identification of most individual members of the complex mixtures of carboxylic acids found in petroleum ('naphthenic acids') has eluded chemists for over a century; they remain unresolved by conventional gas chromatographic methods. Recently, however, we successfully used two-dimensional comprehensive gas chromatography/mass spectrometry to identify numerous individual diamondoid acids in the naphthenic acids of oil sands process water (OSPW). We have now applied the same methods to a study of a mixture of commercially available naphthenic acids originally refined from petroleum. The results confirm that OSPW and refined petroleum contain very different distributions of acids, as noted previously, although some of the diamondoid acids recently identified in OSPW were detectable in both. Rather, two-dimensional comprehensive gas chromatography/time-of-flight mass spectrometry (GCxGC/ToF-MS) of the methyl esters of the petroleum acids and of numerous acids synthesised for comparison showed that the former comprised mainly C(8-18) straight-chain, methyl-branched, acyclic isoprenoid, cyclohexyl and isomeric octahydropentalene, perhydroindane and perhydronaphthalene (decalin) acids. Some of the latter bicyclic acids occurred as both the non-alkyl-substituted isomers and the bicyclic ethanoic and propanoic acids. Also present in minor quantities was a range of phenyl carboxylic and substituted phenyl alkanoic acids, and traces of non-acids, including trimethylnaphthalenes, again identified by comparison with the synthesised compounds. These results represent some of the first identifications of multiple individual naphthenic acids in commercial mixtures originating from petroleum and provide a basis for future studies of the petroleum geochemistry, toxicities and environmental impacts of the acids. Furthermore, characterisation of the acids will be important for improving the understanding of the role of naphthenic acids in petroleum engineering, particularly for oil pipeline deposition problems.     

Quantitative gas-liquid chromatography of non-protein amino acids.

The quantitative gas--liquid chromatographic analysis of non-protein amino acids, in the presence of protein amino acids, is described. The amino acids were determined as their N-trifluoroacetyl n-butyl esters on an ethylene glycol adipate column. The relative molar responses of 38 amino acids are reported.     

Mass spectra of some 2-, 3-, and 4-pyridinecarboxylic acids. Further evidence of a N-H interaction for loss of carbon dioxide

Mass spectra of 3-acetamido-, 3-methoxy-, and 4-methoxy-2-pyridinecarboxylic acids, 2,6-pyridinedicarboxylic acid, 4-nitro-2-pyridinecarboxylic acid N-oxide, 2-chloro- and 2-nitro-x-pyridinecarboxylic acids (X = 3 and 5), 2-chloro- and 2-nitro-4-pyridinecarboxylic acids, and 4-pyridinecarboxylic acid are reported. The 2-pyridinecarboxylic acids lost carbon dioxide (M-44) as has been reported. The 3-pyridinecarboxylic acids showed no definite trend in fragmentation; however, the 4-pyridinecarboxylic acids lost OH (M-17) first. This change in fragmentation pat-tern is due to an interaction of the ring nitrogen and carboxyl group in the 2-pyridinecarboxylic acids which is not present in the 4-pyridinecarboxylic acids.     

Micro-scale sequence analysis from the N-terminus of peptides using the fluorogenic Edman reagent 4-N,N-dimethylamino-1-naphthyl isothiocyanate

The fluorogenic Edman reagent 4-N,N-dimethylamino-1-naphthyl isothiocyanate (DNTC) was reacted with amino acids and peptides, cyclized by acid and the liberated 4-N,N-dimethylamino-1-naphthyl thiohydantoin (DNTH) amino acids were then separated and detected by HPLC. The fluorescence intensities of DNTH-amino acids except DNTH-proline and -serine were dramatically increased in the alkaline solution and organic solvent. Thus, the postcolumn reaction with alkaline acetonitrile solution was adopted in HPLC. The polar and aromatic amino acids afforded two DNTH-amino acids on derivatization with DNTC and cyclization with acids. These were suggested to be stereoisomers of DNTH-amino acids. The sequence analysis of 0.5 nmol Leu-enkephalin was achieved by the double coupling method with DNTC and phenyl isothiocyanate followed by the proposed HPLC system.     

Synthesis of enantiopure omega-functionalized C15 alpha-amino carboxylates

An efficient route for the synthesis of enantiopure omega-hydroxy, omega-carboxy, omega-oxo, and omega-amino alpha-amino acids and bis-alpha-amino acids was developed. The synthesis of omega-trityloxy delta,epsilon-unsaturated alpha-amino acids was based on the Wittig reaction of methyl (2S)-2-[bis(tert-butoxycarbonyl)amino]-5-oxopentanoate with omega-trityloxy alkylidene triphenylphosphoranes. After hydrogenation, the omega-hydroxy alpha-amino acid was used as starting material for the synthesis of other omega-functionalized alpha-amino acids. The length of the side chain of alpha-amino acids or bis-alpha-amino acids depends on the starting alkanediol or dibromide used to prepare the phosphoranes.     

Ligand-exchange chromatography of amino acids on copper-, cobalt- and zinc-chelex 100.

Procedures for the ligand-exchange chromatography of amino acids on copper-, cobalt-and zinc-Chelex 100 have been examined. Ligand exchange on the copper complex affords a simple and rapid method for the removal of amino acids (except for aspartic and glutamic acids) from dilute solutions. The influence of the pH on the binding of amino acids to the metal complex was also studied. The bound amino acids could be eluted with ammonium hydroxide which also causes a slight metal leakage. Chromatography on cobalt- and zinc-Chelex 100 showed that only the basic amino acids were quantitatively attached to these complexes at pH 8.3-9.5, whereas the others were predominantly EXCLUDED. This procedure can be used for the selective concentration and removal of basic amino acids in the presence of other amino acids.     

Transition metal-catalyzed syntheses of organic acids by chelation-promoted regioselective double bond insertion

The rhodium- or nickel-catalyzed reaction of vinylic halides with alkali salts of 3-butenoic acids leads to regioselective formation of dienoic acids, containing 3,5-conjugated double bonds. Monoarylacetylenes also react with 3-butenoic acids in a rhodium-catalyzed synthesis of the same acids. The stereochemistries of the acids and the nature of the by-products are discussed in the light of the proposed mechanisms.     

Analysis of 'ARN' naphthenic acids by high temperature gas chromatography and high performance liquid chromatography

Examination by high temperature GC (HTGC) of the methyl esters of the so-called 'ARN' naphthenic acids from crude oils of North Sea UK, Norwegian Sea and West African oilfields revealed the distributions of resolved 4-8 ring C80 tetra acids and trace amounts of other acids. Whilst all three oils contained apparently the same major acids, the proportions of each differed, possibly reflecting the growth temperatures of the archaebacteria from which the acids are assumed to have originated. The structures of the 4, 5, 7 and 8 ring acids are tentatively assigned by comparison with the known 6 ring acid and related natural products and an HPLC method for the isolation of the individual acids is described. ESI-MS of individual acids isolated by preparative HPLC established the elution order of the 4-8 ring acids on the HPLC and HTGC systems and revealed the presence of previously unreported acids tentatively identified as C81 and C82 7 and 8 ring analogues.     

Measurement of polyunsaturated fatty acids of myocardial lipids by high performance liquid chromatography

Summary This report describes a modified method for the separation and analysis of polyunsaturated fatty acids such as 20:4, 20:5, and 22:6, using HPLC. The results show that these fatty acids are well separated from the saturated acids. Since the unsaturated fatty acids elute earlier than saturated acids, and this method does not require the fractionation of free fatty acids using thin layer chromatography, a necessary step for the gas chromatographic analysis, the recoveries of polyunsaturated fatty acids were significantly higher as compared to those from gas chromatography. Furthermore, HPLC and gas chromatographic methods gave identical results for the acyl chain composition of phosphatidylserine. The advantages of using HPLC over gas chromatography in determining the acyl chain composition of free fatty acids and phospholipids are also discussed.     

氨基化氧化石墨烯和脂肪酸在水-油界面的共吸附动力学北大核心CSCD

合成了氨基化氧化石墨烯(NH_(2)-PEG-GO),利用界面张力仪研究了脂肪酸质量浓度、NH_(2)-PEG-GO质量浓度以及脂肪酸链长度对于NH_(2)-PEG-GO与脂肪酸在水-油界面共吸附行为的影响。结果表明,当NH_(2)-PEG-GO与脂肪酸共同存在于液相且质量浓度较低时,此时的水-油界面张力值要明显低于体系中只添加NH_(2)-PEG-GO或脂肪酸时的张力值。脂肪酸的链长越长,NH_(2)-PEG-GO与脂肪酸共吸附降低界面张力能力越强。由于相对于NH_(2)-PEG-GO,脂肪酸尺寸较小,所以初期的界面张力降低由脂肪酸吸附引起,而且,脂肪酸在水-油界面的吸附能够吸引NH_(2)-PEG-GO向界面扩散,表现出吸附的协同效应。而在吸附后期,界面张力降低现象由NH_(2)-PEG-GO主导,NH_(2)-PEG-GO与脂肪酸之间存在竞争吸附。     

Microwave-Assisted Esterification of Diverse Carboxylic Acids and Chiral Amino Acids

A facile and efficient synthetic method of esters from their corresponding carboxylic acids and amino acids is described. The esterification reaction of carboxylic acids and amino acids could be greatly accelerated under microwave irradiation because the reactions described in this article took place in only 5 min with almost quantitative yields, and distinct acidity of catalytic acids was well tolerated. Unlike the racemation problem in microwave-assisted N-acylation reactions, the esters of chiral amino acids could be achieved with retention of configuration under this condition.