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.     

Ligand-exchange chromatography of amino acids on nickel-Chelex 100.

A ligand-exchange chromatographic proceudre for the selective separation of amino acids from inorganic ions is presented. It was found that the binding of amino acids to the nickel-Chelex 100 resin is pH dependent. At pH 8.5-9.1, only the basic amino acids lysine, histidine and arginine are quantitatively attached to the complex, whereas at pH 11, other amino acids with the exception of aspartic acid and glutamic acid are also bound, although not quantitatively. All of the amino acids can be eluted from the complex with 3 M ammonia solution without the displacement of nickel ions from the complex. This method can be used for the removal of the basic amino acids from solutions in the presence of inorganic ions as well as other amino acids.     

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.     

Chiral separation and determination of the optical purity of thiamphenicol-related chiral compound by capillary zone electrophoresis with cyclodextrins as chiral selectors

Summary One classical method for quantitation of amino acids in proteins is hydrolysis of the proteins and determination of the free amino acids. Although the drastic experimental conditions necessary for complete hydrolysis always cause degradation of some of the amino acids, if mild hydrolysis conditions are used, a mixture of amino acids and oligopeptides is obtained. If these conditions are adequately tuned, the oligopeptides are almost exclusively dipeptides. For this reason we have initiated a study to find a derivatizing agent suitable for the analysis of amino acids and dipeptides by an absolute method of quantitation already tested for amino acids. FMOC-Cl was found to be a suitable derivatizing agent for this purpose.     

阴离子交换-积分脉冲安培检测法分离测定氨基酸注射液中的氨基酸和葡萄糖

 用阴离子交换 积分脉冲安培检测法测定了氨基酸注射液中 1 7种氨基酸和葡萄糖。研究了氨基酸和葡萄糖在阴离子交换中的保留行为。采用了优化的水、NaOH和NaAc三元梯度淋洗条件。在优化的梯度淋洗条件和积分脉冲安培检测条件下 ,氨基酸和葡萄糖的检出限为 0 3pmol～ 1 0 3pmol,线性范围约为 2个数量级。样品加标回收率为 88 3 %～ 1 0 4 6 %。方法简单、灵敏、准确。     

Protein alignment: Exact versus approximate. An illustration

We illustrate solving the protein alignment problem exactly using the algorithm VESPA (very efficient search for protein alignment). We have compared our result with the approximate solution obtained with BLAST (basic local alignment search tool) software, which is currently the most widely used for searching for protein alignment. We have selected human and mouse proteins having around 170 amino acids for comparison. The exact solution has found 78 pairs of amino acids, to which one should add 17 individual amino acid alignments giving a total of 95 aligned amino acids. BLAST has identified 64 aligned amino acids which involve pairs of more than two adjacent amino acids. However, the difference between the two outputs is not as large as it may appear, because a number of amino acids that are adjacent have been reported by BLAST as single amino acids. So if one counts all amino acids, whether isolated (single) or in a group of two and more amino acids, then the count for BLAST is 89 and for VESPA is 95, a difference of only six. © 2015 Wiley Periodicals, Inc.     

Selectivity control in the non-aqueous capillary electrophoretic separation of amino acids

The separation of dansylated amino acids and underivatized amino acids in non-aqueous electrolytes was evaluated with direct and indirect UV detection. Different migration orders were achieved for dansylated amino acids in methanol compared to aqueous electrolyte systems. A reversed migration order was observed for some dansylated amino acids. Separation selectivity was different under acidic and basic conditions and was also a function of the solvation properties of the solvent. Underivatized amino acids were separated in basic and acidic electrolytes in methanol; different separation selectivities and, for some amino acids, a reversed migration order were also observed in these electrolyte systems. Analytical merits of the separation of both derivatized and underivatized amino acids were briefly evaluated; detection limits for dansylated amino acids were in the range of 2·10⁻⁷–4·10⁻⁷ mol/l and, for underivatized amino acids, were 2·10⁻⁶–4·10⁻⁵ mol/l.     

海藻糖和氨基酸之间相互作用的分子动力学模拟

虽然海藻糖已经广泛用于蛋白质稳定性研究,但海藻糖稳定蛋白质的作用机理尚不清晰.本文利用全原子分子动力学模拟研究了20种常见氨基酸和海藻糖之间的分子机理.结果表明,所有氨基酸,尤其是极性和带电氨基酸,均优先与水分子结合.相反,仅有疏水性氨基酸与海藻糖发生相互作用,尤其是芳香族和疏水性氨基酸的侧链更易于和海藻糖接触.所有氨基酸的主链与水分子接触的趋势一致.虽然氨基酸和海藻糖与水之间均形成氢键,但氨基酸和海藻糖之间的氢键相互作用要弱于氨基酸和水之间的氢键相互作用.上述分子模拟的结果对于海藻糖稳定蛋白质作用机理的解析及高效蛋白质稳定剂的理性设计具有非常重要的理论指导意义.     

中国梨木虱分泌物中氨基酸的分离与分析

利用离子交换色谱法分离了中国梨木虱分泌物中的氨基酸;利用毛细管气相色谱法对梨木虱分泌物中氨基酸的三氯乙酰了酯衍生物进行了分析。用标准样对照定性,内标法定量。分泌物中共检出13种氨基酸。     

New Naturally Occurring Amino Acids

The majority of the 500 or so naturally occurring amino acids known today were discovered during the last 30 years, for example during the search for new antibiotics in the culture media of microorganisms, or as components of the antibiotics in fungi, seeds, in numerous plants and fruits, and in the body fluids of animals. Some 240 of these amino acids occur free in nature, some only as intermediates in metabolism. This article provides an overview of the developments that have taken place in this area since 1956 when the last review appeared. Summary accounts are presented, dealing with new unsaturated amino acids, cyclopropane- and cyclobutane-amino acids, heterocyclic amino acids, halogen-containing amino acids sulfur-, selenium- and phosphorus-containing amino acids as well as aliphatic amino acids. In a few cases, e. g. betalamic acid and muscaflavin, the biosynthesis is described in detail.     

Some factors affecting separation and detection of amino acids by high-performance anion-exchange chromatography with integrated pulsed amperometric detection

Some factors influencing the separation and detection of amino acids by high-performance anion-exchange chromatography with integrated pulsed amperometric detection were investigated. These factors include eluent concentration, column temperature, and detection waveform. The selectivity changes in weakly retained amino acids are slight with changing sodium hydroxide eluent concentration. When sodium acetate eluent concentration is changed, the selectivity variations between strongly retained amino acids containing two carboxyl groups and containing only one carboxyl group are obviously different. Significant but slight selectivity changes in weakly retained amino acids can be achieved through changing the column temperature. Sodium hydroxide and sodium acetate eluent concentration affect the detection of amino acids. Detection sensitivity of amino acids can be improved by increasing the concentration of sodium hydroxide and sodium acetate in a certain concentration range. The detections of amino acids at two different detection waveforms were compared. The hydroxyl amino acids can be selectively detected by choosing a modified detection waveform. The optimized gradient elution condition and column temperature for analyzing 19 amino acids were obtained. The time for the gradient elution program was 60 min. The column temperature was 35 degrees C. Under the optimized conditions, detection limits for 19 amino acids were 0.15-4.52 pmol. The calibration graphs of peak area for all the analytes were linear for about three orders of magnitude. The RSDs (n=5) of peak area were 0.6-5.6%. The determination of trace amino acid impurities in valine product is shown as an application example.     

Mass spectroscopic approach to amino acids formation processes by UV irradiation to simple organic molecules in aqueous solution.

We have studied amino acid formation by UV (193 nm) irradiation to organic molecules (amines, alcohols and amides) in aqueous solution. Among several types of detected amino acids, small aliphatic amino acids (Gly and alpha-, beta-Ala and alpha-, beta-, gamma-ABA) were quantitatively identified. Among these small aliphatic amino acids, certain amino acids were formed in its free form, even before hydrolysis, contrary to the results of UV irradiation to a gas mixture of CO, NH3, and H2O, where amino acids were hardly detected before hydrolysis. The species distribution of identified amino acids showed a dependence on the starting organic molecules, and also on the presence of ammonia. The formation processes of the identified small aliphatic amino acids were investigated with the aid of electrospray ionization (ESI) MS and MS/MS measurements of photoproducts. Possible formation processes of these amino acid precursors from each starting molecules are proposed. By identifying the amino acid precursor, which has a chiral carbon atom, a new possibility is suggested for asymmetric photosynthesis of amino acid from achiral organic molecules.     

Adsorption Behavior of Amino Acids on a Stainless Steel Surface

The adsorption behavior of various amino acids on a stainless steel surface was investigated at 30 degrees C and over a pH range of 3-10. Acidic and basic amino acids except histidine adsorbed remarkably at pH 3-4 and 7-10, respectively, and showed Langmuir-type adsorption isotherms. The effects of pH and ionic strength on the adsorption isotherms were investigated to analyze the interactions between amino acids and adsorption sites on the stainless steel. Hydrophobic amino acids and glycine showed only small adsorbed amounts at all pHs tested. For the acidic and basic amino acids, reversibility of the absorption and the influence of the ionic strength on the adsorption behavior were examined. The adsorption isotherms of the derivatives of aspartic acid were also measured in order to examine the contribution of the carboxylic groups of acidic amino acids to the adsorption. Furthermore, a Fourier-transform infrared spectroscopic analysis and semiempirical molecular orbital calculation were carried out to analyze the ionization states and the configuration of the amino acids adsorbed on a stainless steel surface. These investigations suggest that the acidic and basic amino acids adsorb through two electrostatic interactions of two ionized groups in the amino acid with a stainless steel surface. Copyright 2000 Academic Press.     

海藻糖和氨基酸之间相互作用的分子动力学模拟

虽然海藻糖已经广泛用于蛋白质稳定性研究,但海藻糖稳定蛋白质的作用机理尚不清晰. 本文利用全原子分子动力学模拟研究了20种常见氨基酸和海藻糖之间的分子机理. 结果表明,所有氨基酸,尤其是极性和带电氨基酸,均优先与水分子结合. 相反,仅有疏水性氨基酸与海藻糖发生相互作用,尤其是芳香族和疏水性氨基酸的侧链更易于和海藻糖接触. 所有氨基酸的主链与水分子接触的趋势一致. 虽然氨基酸和海藻糖与水之间均形成氢键,但氨基酸和海藻糖之间的氢键相互作用要弱于氨基酸和水之间的氢键相互作用. 上述分子模拟的结果对于海藻糖稳定蛋白质作用机理的解析及高效蛋白质稳定剂的理性设计具有非常重要的理论指导意义.     

二十种混合氨基酸的质谱鉴定 直接磷酰化物的正负离子FAB-MS分析

将二十种天然氨基酸按等摩尔量混合后,用二异丙基亚磷酸酯直接磷酰化,可以高选择性(96%)地获得N-磷酰氨基酸衍生物的混合物,负离子FAB-MS可以原位检出混合物中全部N-磷酰氨基酸,且准分子离子峰较高,可发展为混合氨基酸衍生物全分析的有效手段.正离子FAB-MS则对碱性磷酰化氨基酸的检出更有利     

Highly Stereoselective Recognition and Deracemization of Amino Acids by Supramolecular Self‐Assembly

The highly stereoselective supramolecular self‐assembly of α‐amino acids with a chiral aldehyde derived from binol and a chiral guanidine derived from diphenylethylenediamine (dpen) to form the imino acid salt is reported. This system can be used to cleanly convert D ‐amino acids into L ‐amino acids or vice versa at ambient temperature. It can also be used to synthesize α‐deuterated D ‐ or L ‐amino acids. A crystal structure of the ternary complex together with DFT computation provided detailed insight into the origin of the stereoselective recognition of amino acids.     

Determination of absolute configurations of amino acids by asymmetric autocatalysis of 2-alkynylpyrimidyl alkanol as a chiral sensor

Asymmetric autocatalysis of 2-alkynyl-5-pyrimidyl alkanol is employed as a chiral sensor of 20 amino acids. Asymmetric autocatalysis using amino acids as chiral initiators gave pyrimidyl alkanols of the absolute configurations that were correlated with those of the amino acids. The enantiomeric excesses of pyrimidyl alkanol are invariably high even when the enantiomeric excess of amino acids is as low as 0.1%. Thus, by determining the absolute configuration of pyrimidyl alkanol with high enantiomeric excess, one can determine the absolute configuration of amino acids even when their enantiomeric excess is low.     

Chromatographic determination of amino acids in foods

Amino acids in foods exist in a free form or bound in peptides, proteins, or nonpeptide bonded polymers. Naturally occurring L-amino acids are required for protein synthesis and are precursors for essential molecules, such as co-enzymes and nucleic acids. Nonprotein amino acids may also occur in animal tissues as metabolic intermediates or have other important functions. The development of bacterially derived food proteins, genetically modified foods, and new methods of food processing; the production of amino acids for food fortification; and the introduction of new plant food sources have meant that protein amino acids and amino acid enantiomers in foods can have both nutritional and safety implications for humans. There is, therefore, a need for the rapid and accurate determination of amino acids in foods. Determination of the total amino acid content of foods requires protein hydrolysis by various means that must take into account variations in stability of individual amino acids and resistance of different peptide bonds to the hydrolysis procedures. Modern methods for separation and quantitation of free amino acids either before or after protein hydrolysis include ion exchange chromatography, high performance liquid chromatography (LC), gas chromatography, and capillary electrophoresis. Chemical derivatization of amino acids may be required to change them into forms amenable to separation by the various chromatographic methods or to create derivatives with properties, such as fluorescence, that improve their detection. Official methods for hydrolysis and analysis of amino acids in foods for nutritional purposes have been established. LC is currently the most widely used analytical technique, although there is a need for collaborative testing of methods available. Newer developments in chromatographic methodology and detector technology have reduced sample and reagent requirements and improved identification, resolution, and sensitivity of amino acid analyses of food samples.     

Retention behavior of a homologous series and positional isomers of aliphatic amino acids in hydrophilic interaction chromatography

The retention behavior of several series of free α‐ and ω‐amino acids and positional isomers of amino pentanoic acid in the hydrophilic interaction chromatography mode (HILIC) was studied. The study was carried out on three stationary phases followed by post‐column derivatization with fluorescence detection in order to describe the retention mechanism of the tested amino acids. The effect of chromatographic conditions including acetonitrile content in the mobile phase, mobile phase pH (ranging from 3.5 to 6.5) and concentration of buffer in the mobile phase was investigated. The effect of the number of carbon atoms (n_C) in aliphatic chains of the individual homologue of α‐ and ω‐amino acids and the logarithm of the partition coefficient (logD) on retention was also a part of the presented study. A good correlation (r > 0.98) between the logk and logD values of amino acids or n_C, respectively, was observed. The described linear relationships were subsequently applied to predict the retention behavior of individual members of the homologous series of amino acids and to optimize the mobile phase composition in HILIC. The obtained results confirmed that the retention mechanism of α‐amino acids, ω‐amino acids and positional isomers of amino acids was based on the logD values and the number of carbon atoms in the aliphatic chains of amino acids. The elution order of ω‐amino acids and positional isomers of amino pentanoic acid was strongly dependent on the mobile phase pH in the investigated range whereas the retention factors of all α‐amino acids remained essentially unchanged on all tested stationary phases.     

Analysis of amino acids in brain and plasma samples by sensitive gas chromatography-mass spectrometry

Gas chromatography-mass spectrometry-selected-ion monitoring provided a simple and sensitive method for analyzing amino acids in plasma and brain samples. Although the sensitivities of chemical ionization and electron-impact ionization were similar chemical ionization produced higher-mass ions, which might increase the selectivity of the assay. Both chemical and electron-impact ionization distinguished the natural amino acids from the 15N-labelled amino acids. The recovery of amino acids from plasma and brain samples was ca. 75%. The amino acid levels determined by gas chromatography-mass spectrometry were comparable with the amino acid levels determined by high-performance liquid chromatography or amino acid analyzer.