氨基酸卟啉锌配合物对氨基酸酯的分子识别研究(英文)

用紫外可见吸收光谱滴定方法研究了一种新型的苏氨酸卟啉锌配合物(主体)对氨基酸酯(客体)的分子识别.这种锌卟啉可以与氨基酸酯形成 1:1和 1:2的两种加合物.氨基酸酯的氨基首先与氨基酸残基的羧基作用形成 1:1的加合物,然后与锌卟啉的中央锌原子配位形成 1:2的加合物,客体分子与主体分子上的氨基酸残基之间的排斥作用以及主客体之间的色散力作用是主体分子能识别客体分子的另外两种作用。     

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.     

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.     

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.     

Complexation of Amino Acid Methylesters and Amino Alcohols by 18-Crown-6 and Benzo-18-crown-6 in Methanol

The complexation of protonated amino acid methylesters and amino alcohols bythe ligands 18-crown-6 (18C6) and benzo-18-crown-6 (B18C6) has been studiedin methanol using calorimetric titrations. No influence of the anions upon thestability constants and thermodynamic data for the reaction of protonated aminoacid methylesters with both ligands has been noticed, which indicates the completedissociation of the salts employed. A similar effect has been observed for thecomplexation of protonated and unprotonated amino alcohols with 18C6 andB18C6. The values obtained of the reaction enthalpies for the complexation ofprotonated amino acid methylesters with 18C6 are larger than those correspondingto the complexation with B18C6. The results demonstrate that the complex formationof unprotonated amino alcohols is favored by entropic contributions, while thecomplexation of protonated amino alcohols is favored by enthalpic contributionswith both ligands. The influence of various substituents on the complexation behaviorof amino acid and amino alcohol has also been investigated.     

Quantification of glycated N‐terminal peptide of hemoglobin using derivatization for multiple functional groups of amino acids followed by liquid chromatography/tandem mass spectrometry

A novel method of amino acid analysis using derivatization of multiple functional groups (amino, carboxyl, and phenolic hydroxyl groups) was applied to measure glycated amino acids in order to quantify glycated peptides and evaluate the degree of glycation of peptide. Amino and carboxyl groups of amino acids were derivatized with 1‐bromobutane so that the hydrophobicities and basicities of the amino acids, including glycated amino acids, were improved. These derivatized amino acids could be detected with high sensitivity using LC‐MS/MS. In this study, 1‐deoxyfructosyl‐VHLTPE and VHLTPE, which are N‐terminal peptides of the β‐chains of hemoglobin, were selected as target compounds. After reducing the peptide sample solution with sodium borohydride, the obtained peptides were hydrolyzed with hydrochloric acid. The released amino acids were then derivatized with 1‐bromobutane and analyzed with LC‐MS/MS. The derivatized amino acids, including glycated amino acids, could be separated using an octadecyl silylated silica column and good sharp peaks were detected. We show a confirmatory experiment that the proposed method can be applied to evaluate the degree of glycation of peptides, using mixtures of glycated and non‐glycated peptide. Copyright © 2015 John Wiley & Sons, Ltd.     

Potential of fermentation profiling via rapid measurement of amino acid metabolism by liquid chromatography-tandem mass spectrometry

Monitoring amino acid metabolism during fermentation has significant potential from the standpoint of strain selection, optimizing growth and production in host strains, and profiling microbial metabolism and growth state. A method has been developed based on rapid quantification of underivatized amino acids using liquid chromatography-electrospray tandem mass spectrometry (LC-MS-MS) to monitor the metabolism of 20 amino acids during microbial fermentation. The use of a teicoplanin-based chiral stationary phase coupled with electrospray tandem mass spectrometry allows complete amino acid analyses in less than 4 min. Quantification is accomplished using five isotopically labeled amino acids as internal standards. Because comprehensive chromatographic separation and derivatization are not required, analysis time is significantly less than traditional reversed- or normal-phase LC-based amino acid assays. Intra-sample precisions for amino acid measurements in fermentation supernatants using this method average 4.9% (R.S.D.). Inter-day (inter-fermentation) precisions for individual amino acid measurements range from 4.2 to 129% (R.S.D.). Calibration curves are linear over the range 0-300 microg/ml, and detection limits are estimated at 50-450 ng/ml. Data visualization techniques for constructing semi-quantitative fermentation profiles of nitrogen source utilization have also been developed and implemented, and demonstrate that amino acid profiles generally correlate with observed growth profiles. Further, cellular growth events, such as lag-time and cell lysis can be detected using this methodology. Correlation coefficients for the time profiles of each amino acid measured illustrate that while several amino acids are differentially metabolized in similar fermentations, a select group of amino acids display strong correlations in these samples, indicating a sub-population of analytes that may be most useful for fermentation profiling.     

Amino acid end-group in commercial heparin. II. Reaction kinetics of the amino end groups with 2,4,6-trinitrobenzenesulfonic acid

Three different commercial heparins were trinitophenylated with 2,4,6-trinitrobenzenesulfonic acid (TNBS) under aqueous conditions. The reaction kinetics of amino groups in heparin with TNBS showed that the reactivities of amino groups were significantly different for free amino groups on heparin, compared to reactivities in peptides and amino acid residues attached to heparin molecules. With TNBS, unreactive amino groups were always present during the reaction.     

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.     

Separation of amino alcohols using divalent dipeptides as counter ions in aqueous CE

Divalent dipeptides have been introduced as counter ions in aqueous CZE. The dipeptides form ion pairs with amino alcohols in the BGE and facilitate the separation of amino alcohols. High concentrations of dipeptide caused reversed effective mobility for the analytes. The net charge of the dipeptide can be controlled using a buffer or a strong base, and regulates the interaction between the dipeptide and the amino alcohol. A stronger interaction and higher selectivity of amino alcohols was observed when the dipeptides were used as divalent counter ions, than in monovalent or uncharged form. Association constants for ion pairs between divalent dipeptides and amino alcohols can be used to enhance selectivity for amino alcohols in CZE. No chiral separation of amino alcohols was observed when using the dipeptides as ion‐pairing chiral selectors in aqueous BGE, but addition of methanol to the BGE promoted enantioselectivity.     

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.     

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.     

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.     

Quantum chemical studies on the tautomerism of some potentially tautomeric aminoindazole derivatives

The aqueous phase AM1, PM3, and PM5 calculation data had indicated that when a potentially tautomeric amino group is placed at 3C position of the indazole ring the ring-chain tautomerism becomes feasible. However, when the amino group is placed at 4–7C of the indazole ring only the annular tautomerism was found to be feasible and no effect of amino group to provoke a ring chain tautomerism was observed. On the other hand amino form of 3 amino substituted indazole was found to be predominant over imino forms whereas for the 4–7 amino substituted indazoles imino forms were found to be predominant over amino forms. The attempt to apply soft–hard base and soft nucleophile–electrophile criteria to protonation and tautomerism phenomena was successful.     

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.     

Highly Chemoselective Aerobic Oxidation of Amino Alcohols into Amino Carbonyl Compounds

The direct oxidation of unprotected amino alcohols to their corresponding amino carbonyl compounds has often posed serious challenges in organic synthesis and has constrained chemists to adopting an indirect route, such as a protection/deprotection strategy, to attain their goal. Described herein is a highly chemoselective aerobic oxidation of unprotected amino alcohols to their amino carbonyl compounds in which 2‐azaadamantane N‐oxyl (AZADO)/copper catalysis is used. The catalytic system developed leads to the alcohol‐selective oxidation of various unprotected amino alcohols, carrying a primary, secondary, or tertiary amino group, in good to high yield at ambient temperature with exposure to air, thus offering flexibility in the synthesis of nitrogen‐containing compounds.     

Dual substrate recognition of aminotransferases

Pyridoxal 5'-phosphate-dependent aminotransferases reversibly catalyzes the transamination reaction in which the alpha-amino group of amino acid 1 is transferred to the 2-oxo acid of amino acid 2 (usually 2-oxoglutarate) to produce the 2-oxo acid of amino acid 1 and amino acid 2 (glutamate). An aminotransferase must thus be able to recognize and bind two kinds of amino acids (amino acids 1 and 2), the side chains of which are different in shape and properties, from among many other small molecules. The dual substrate recognition mechanism has been discovered based on three-dimensional structures of aromatic amino acids, histidinol phosphate, glutamine:phenylpyruvate, acetylornithine, and branched-chain amino acid aminotransferases. There are two representative strategies for dual substrate recognition. An aromatic amino acid aminotransferase prepares charged and neutral pockets for acidic and aromatic side chains, respectively, at the same place by a large-scale rearrangement of the hydrogen-bond network caused by the induced fit. In a branched-chain aminotransferase, the same hydrophobic cavity implanted with hydrophilic sites accommodates both hydrophobic and acidic side chains without side-chain rearrangements of the active-site residues, which is reminiscent of the lock and key mechanism. Dual substrate recognition in other aminotransferases is attained by combining the two representative methods.     

Synthesis and antifungal activity of rhodopeptin analogues. 1. Modification of the east and south amino acid moieties

Structure-activity relationships of the east and south amino acid modified analogues of rhodopeptins, novel antifungal cyclic tetrapeptides isolated from Rhodococcus species Mer-N1033, have been investigated. It was observed that a basic amino acid moiety (lysine or ornithine) as the east amino acid and a hydrophobic and bulky neutral amino acid (i.e., gamma-methylleucine) as the south amino acid were indispensable structure motifs for antifungal activity of rhodopeptin analogues.