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。     

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.     

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.     

Expanding the genetic code

The ability to incorporate unnatural amino acids into proteins directly in living cells will provide new tools to study protein and cellular function, and may generate proteins or even organisms with enhanced properties. Due to the limited promiscuity of some synthetases, natural amino acids can be substituted with close analogs at multiple sites using auxotrophic strains. Alternatively, this can be achieved by deactivating the editing function of some synthetases. The addition of new amino acids to the genetic code, however, requires additional components of the protein biosynthetic machinery including a novel tRNA-codon pair, an aminoacyl-tRNA synthetase, and an amino acid. This new set of components functions orthogonally to the counterparts of the common 20 amino acids, i.e., the orthogonal synthetase (and only this synthetase) aminoacylates the orthogonal tRNA (and only this tRNA) with the unnatural amino acid only, and the resulting acylated tRNA inserts the unnatural amino acid only in response to the unique codon. Using this strategy, the genetic code of Escherichia coli has been expanded to incorporate unnatural amino acids with a fidelity rivaling that of natural amino acids. This methodology is being applied to other cell types and unnatural analogs with a variety of functionalities.     

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.     

A convenient synthesis of amino acid methyl esters

A series of amino acid methyl ester hydrochlorides were prepared in good to excellent yields by the room temperature reaction of amino acids with methanol in the presence of trimethylchlorosilane. This method is not only compatible with natural amino acids, but also with other aromatic and aliphatic 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.     

Generation of a bacterium with a 21 amino acid genetic code

We have generated a completely autonomous bacterium with a 21 amino acid genetic code. This bacterium can biosynthesize a nonstandard amino acid from basic carbon sources and incorporate this amino acid into proteins in response to the amber nonsense codon. The biosynthetic pathway for the amino acid p-aminophenylalanine (pAF) as well as a unique pAF synthetase and cognate tRNA were added to Escherichia coli. Denaturing gel electrophoresis and mass spectrometric analysis show that pAF is incorporated into myoglobin with fidelity and efficiency rivaling those of the common 20 amino acids. This and other such organisms may provide an opportunity to examine the evolutionary consequences of adding new amino acids to the genetic repertoire, as well as generate proteins with new or enhanced biological functions.     

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.     

Radiation Chemical Studies of Protein Reactions: Dependence of Restorative Amino Acids on Radiation Dose

Abstract

Changes of specific rotation of protein irradiated with Co-60 gamma-rays were restored by some amino acids, such as mono-sodium 1-glutamate. Loss of this recovery effect in some amino acids by irradiation was studied by polarimetry and infrared spectometry. Optical rotation of protein-amino acid solutions increased with an increasing radiation dose given to the amino acids. Changes in optical rotation with irradiation may be due to the loss of the recovery effect of amino acids for the irradiated protein molecule. Changes in infrared spectra increased with an increasing radiation dose given to the amino acids. Such changes in infrared spectra with irradiation may be due to destruction of some radicals in the amino acid molecule.     

Modification of a micellar system for amino acid separation by MEKC--application for amino acid profiling in formulations for parenteral use

The paper proposes a new method for amino acid determination which can be applied for amino acid profiling in solutions for parenteral nutrition. The MEKC method based on a mixed micellar system was developed for the separation of 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) derivatized amino acids. Background electrolyte was based on tris-borate buffer with high alkaline pH. Sodium dodecyl sulfate micelles were modified using 1,2-hexanediol as a co-surfactant. The effect of the modifier on amino acid migration was studied with respect to hydrophobicity of the analytes. The modifier appeared to be suitable to improve the separation of AQC-tagged amino acids without an adverse effect on buffer ionic strength or EOF velocity. The method was successfully validated and applied for amino acid profiling in medicinal preparations for parenteral nutrition. The results obtained were compared with a reference chromatographic method (amino acid analyser).     

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.     

Gas Phase H/D Exchange of Sodiated Amino Acids: Why Do We See Zwitterions?

The gas-phase interaction of sodiated amino acids and sodiated amino acid methyl esters with various deuterium donors is investigated by combining results of H/D exchange reactions with those from density functional theory and molecular dynamics calculations. Discrepancy between experimentally and theoretically obtained structures for sodium cationized amino acids is explained by deuterium donor caused perturbation of the most stable amino acid conformation. Detailed study of H/D exchange mechanism on sodiated amino acids shows that the H/D exchange reaction is preceded by a multistep quasi-isoenergetic transition (perturbation) from a charge solvated to zwitterionic structure in the amino acid. Although the computation refers to the system AlaNa(+) and D(2)O, these mechanisms apply to all amino acids, except those where a functional side-chain group takes part in the perturbation process. The suggested perturbation mechanism applies also for other deuterium donors such as CD(3)OD or even ND(3) and indicates that a single water molecule suffices to convert the sodiated amino acid from charge solvated to zwitterionic form.     

Synthesis of libraries of thiazole, oxazole and imidazole-based cyclic peptides from azole-based amino acids. A new synthetic approach to bistratamides and didmolamides

Treatment of a 1 : 1 mixture of the thiazole-based amino acids 8a and 8b with FDPP-i-Pr(2)NEt in CH(3)CN gave a mixture of the cyclic trimers 14, 15, 16 and 17 and the cyclic tetramers 19 and 23 in the ratio 2 : 7 : 5 : 8 : 1 : 1 and in a combined yield of 70%. Separate coupling reactions between the bisimidazole amino acid 45 and the thiazole/oxazole amino acids 43a and 42a in the presence of FDPP-i-Pr(2)NEt led to the bisimidazole based cyclic trimers 55 and 57 respectively (54-57%) and to the cyclic tetramer 56 (8-11%). Similar coupling reactions involving the bisthiazole and bisoxazole amino acids 49 and 47 with the imidazole/oxazole/thiazole amino acids 41a, 42a and 43a gave rise to the library of oxazole, thiazole and imidazole-based cyclic peptides 58, 59, 60, 61, 62, 63, 64 and 65. A coupling reaction between the bisthiazole amino acid 49 and the oxazole amino acid 73 led to an efficient (36% overall) synthesis of bistratamide H (67) found in the ascidian Lissoclinum bistratum. Coupling reactions involving oxazolines with thiazole amino acids were less successful. Thus, a coupling reaction between the phenylalanine-based oxazoline amino acid 71a and either the thiazole amino acid 8a or the bisthiazole amino acid 74 gave only a 2% yield of the cyclic hexapeptide didmolamide A (4) found in the ascidian Didemnum molle. Didmolamide B (68) was obtained in 9% yield from a coupling reaction between 74 and the phenylalanine threonine amino acid 72, using either FDPP or DPPA.     

Expanding the genetic code

Although chemists can synthesize virtually any small organic molecule, our ability to rationally manipulate the structures of proteins is quite limited, despite their involvement in virtually every life process. For most proteins, modifications are largely restricted to substitutions among the common 20 amino acids. Herein we describe recent advances that make it possible to add new building blocks to the genetic codes of both prokaryotic and eukaryotic organisms. Over 30 novel amino acids have been genetically encoded in response to unique triplet and quadruplet codons including fluorescent, photoreactive, and redox-active amino acids, glycosylated amino acids, and amino acids with keto, azido, acetylenic, and heavy-atom-containing side chains. By removing the limitations imposed by the existing 20 amino acid code, it should be possible to generate proteins and perhaps entire organisms with new or enhanced properties.     

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。     

Determination of accessible amino groups on surfaces by chemical derivatization with 3,5-bis(trifluoromethyl)phenyl isothiocyanate and XPS/NEXAFS analysis

The determination of amino groups on surfaces capable of binding biomolecules is important for the understanding and optimization of technologically relevant coupling processes. In this study, three different types of amino-functionalized model surfaces, amino thiolate on Au, amino siloxane on Si, and polyethylene (PE) foils and films reacted with 1,2-diaminoethane (DAE) were derivatized with 3,5-bis(trifluoromethyl)phenyl isothiocyanate. Subsequently, these samples were analyzed by chemical derivatization X-ray photoelectron spectroscopy (CD-XPS) and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). The determination of amino groups by this analytical approach allows gaining insight into the availability of groups on surfaces that can actually serve as attachment sites for biomolecules in technical applications. In the case of the amino thiolate on Au, almost 90% of the expected amino groups were detected by CD-XPS. Investigation of the amino siloxane films revealed lower yields for the derivatization reaction in the order of 30%. The lowered reaction yields are thought to be due to interactions between the amino siloxane’s amino and silanol groups or the underlying substrate, making them inaccessible to the derivatization agent. The aminated PE samples are characterized by a complex surface chemistry and structure, and reaction yields of the derivatization reaction cannot be unequivocally derived. However, 1–3% of the total carbon atoms in the surface layer were found to be bound to amino groups accessible to the derivatization agent. It can be concluded that, depending on the detailed character of the investigated amino-terminated surface, the amount of amino groups accessible to CD-XPS can be substantially lower than the total amount of amino groups present at the surface.     

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。     

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.