硫醚型芳香族二胺单体的合成及应用

以对氨基硫酸及４，４＇－二氯基二苯砜为原料合成了含硫醚键芳香族二胺单体：，用它制备的聚酰亚胺显示了良好的耐热性能。     

含芳香基的乙二胺四乙酸酰胺衍生物的合成

乙二胺四乙酸二酐(1)与氨基芳香酸(2)进行酰化反应,合成了3种新型含芳香基的乙二胺四乙酸酰胺衍生物,其结构经UV,1H NMR,IR和元素分析表征。探讨了反应条件对收率的影响,在最佳反应条件[110mmol,n(1)∶n(2)=1∶2,pH 3~4时,于40℃反应12 h]下,收率高于75%。     

高效液相色谱法测定羊水中兴奋性氨基酸、抑制性氨基酸的含量

建立了反相高效液相色谱法测定羊水中兴奋性氨基酸天门冬氨酸、谷氨酸,抑制性氨基酸甘氨酸含量的方法,色谱柱为LUNAC18柱(4.6mm×250mm,5μm),流动相为乙腈水(V/V),按低压梯度洗脱,梯度系统0～4min,乙腈40%;4～20min,乙腈40%～52%;20～30min,乙腈52%～60%;30～40min,乙腈60%～40%。流速0.8mL/min,柱温40℃,紫外检测波长260nm;进样量10μL。结果显示,天门冬氨酸、谷氨酸和甘氨酸三者的线性范围均为2.5～85mg/L;标准加入的回收率为99.6%～102.6%。本方法灵敏度高、测定结果可靠。用本方法对201例不同孕期的羊水作兴奋性和抑制性氨基酸检测,发现羊水中3种氨基酸随妊娠进展而增加的趋势,胎儿畸形或宫内缺氧时羊水中这3种氨基酸水平明显升高。     

固定化D-氨基酸氧化酶催化DL-氨基酸去消旋化制备非天然L-氨基酸

在过氧化氢酶和氧气存在下,固定化D-氨基酸氧化酶(D-AAO)对映选择性催化DL-氨基酸中的D-对映体氧化脱氨为相应酮酸,L-对映体保留.研究了D-AAO的底物特异性并对反应条件进行了优化.结果表明:D-AAO具有较宽的底物谱,能够催化疏水性α-氨基酸的D-对映体氧化脱氨.在最优反应条件下,D-AAO催化DL-2-氨基丁酸、DL-2-氨基戊酸去消旋化,L-2-氨基丁酸、L-2-氨基戊酸的收率分别为48%和47%,ee分别为99.5%和99.8%.进一步地利用Pd-C/HCOONH4催化氧化脱氨过程中产生的亚氨基酸原位还原,有效提高了L-2-氨基丁酸、L-2-氨基戊酸的收率并保持高的光学纯度.     

A Green Synthesis of Diisopropyl Phosphoryl Amino Acid

In this paper,we report that diisopropyl phosphoryl amino acid be prepared with reasonable yields under solvent-free condition by adding amino acid to the mixture of diisopropyl phosphite and N-chlorodiisopropylamine.     

Benzylidene Acetal Protecting Group as Carboxylic Acid Surrogate: Synthesis of Functionalized Uronic Acids and Sugar Amino Acids

Direct oxidation of the 4,6‐O‐benzylidene acetal protecting group to C‐6 carboxylic acid has been developed that provides an easy access to a wide range of biologically important and synthetically challenging uronic acid and sugar amino acid derivatives in good yields. The RuCl₃–NaIO₄‐mediated oxidative cleavage method eliminates protection and deprotection steps and the reaction takes place under mild conditions. The dual role of the benzylidene acetal, as a protecting group and source of carboxylic acid, was exploited in the efficient synthesis of six‐carbon sialic acid analogues and disaccharides bearing uronic acids, including glycosaminoglycan analogues.     

某些芳香族氨基酸作探针荧光猝灭法测定安乃近及其代谢产物

在pH3.2的缓冲介质中,安乃近(ANG)及其代谢产物4-甲氨基安替比林(MAA)、4-乙酰氨基安替比林(AAA)与色氨酸(Trp)、酪氨酸(Tyr)和苯丙氨酸(Phe)等芳香族氨基酸反应并形成结合产物,引起上述氨基酸的荧光发生猝灭,最大猝灭波长分别位于352nm(ANG-Trp体系)、304nm(ANG-Tyr,MAA-Tyr和AAA-Tyr体系)和284nm(ANG-Phe体系).其荧光猝灭值(ΔF)在一定范围内与ANG,MAA和AAA成正比.荧光猝灭反应具有较高灵敏度,对于ANG,MAA和AAA的检出限为13.3ng/mL(ANG-Trp体系)、15.8ng/mL(ANG-Tyr体系)、64.5ng/mL(ANG-Phe体系)、150.0ng/mL(MAA-Tyr体系)和230.8ng/mL(AAA-Tyr体系).实验研究了荧光猝灭反应的适宜条件和影响因素,考察了共存物质的影响,表明方法具有良好的选择性,可用于ANG片剂及其代谢物尿药浓度的快速测定.从吸收光谱的变化、温度的影响以及Stern-Volmer作图,判断该反应为静态猝灭反应,氨基酸和安乃近通过静电引力和芳基堆积作用而形成1:1的复合物.     

芳香氨基酸在吸附树脂上的传质速度的研究

本文建立了测量芳香氨基酸在吸附树脂上传质速度的方法。引用Boyd方程模型测定了苯丙氨酸和酪氨酸的有效内扩散系数;研究了树脂结构与芳香氨基酸扩散速度之间的关系;同时考察了温度、pH值诸因素对扩散速度的影响。     

Amino Acid Ionic Liquids as Chiral Ligands in Ligand‐Exchange Chiral Separations

Recently, amino acid ionic liquids (AAILs) have attracted much research interest. In this paper, we present the first application of AAILs in chiral separation based on the chiral ligand exchange principle. By using 1‐alkyl‐3‐methylimidazolium L ‐proline (L ‐Pro) as a chiral ligand coordinated with copper(II), four pairs of underivatized amino acid enantiomers—dl ‐phenylalanine (dl ‐Phe), dl ‐histidine (dl ‐His), dl ‐tryptophane (dl ‐Trp), and dl ‐tyrosine (dl ‐Tyr)—were successfully separated in two major chiral separation techniques, HPLC and capillary electrophoresis (CE), with higher enantioselectivity than conventionally used amino acid ligands (resolution (R_s)=3.26–10.81 for HPLC; R_s=1.34–4.27 for CE). Interestingly, increasing the alkyl chain length of the AAIL cation remarkably enhanced the enantioselectivity. It was inferred that the alkylmethylimidazolium cations and L ‐Pro form ion pairs on the surface of the stationary phase or on the inner surface of the capillary. The ternary copper complexes with L ‐Pro are consequently attached to the support surface, thus inducing an ion‐exchange type of retention for the dl ‐enantiomers. Therefore, the AAIL cation plays an essential role in the separation. This work demonstrates that AAILs are good alternatives to conventional amino acid ligands for ligand‐exchange‐based chiral separation. It also reveals the tremendous application potential of this new type of task‐specific ILs.     

Gas-Phase Conformational Map of the Amino Acid Isovaline

Four conformers of the non-proteinogenic α-amino acid isovaline, vaporized by laser ablation, are characterized by Fourier-transform microwave techniques in a supersonic expansion. The comparison between the experimental rotational and ¹⁴N nuclear quadrupole coupling constants and the ab initio calculated ones provides conclusive evidence for the identification of the conformers. The most stable species is stabilized by an N−H⋅⋅⋅O =C intramolecular hydrogen bond and a cis-COOH interaction, whereas the higher-energy conformers exhibit an N⋅⋅⋅H−O intramolecular hydrogen bond and trans-COOH, as in other aliphatic amino acids. The spectroscopic data herein reported can be used for the astrophysical purpose in a possible detection of isovaline in space.     

Computational Study on the Attack of .OH Radicals on Aromatic Amino Acids

The attack of hydroxyl radicals on aromatic amino acid side chains, namely phenylalanine, tyrosine, and tryptophan, have been studied by using density functional theory. Two reaction mechanisms were considered: 1) Addition reactions onto the aromatic ring atoms and 2) hydrogen abstraction from all of the possible atoms on the side chains. The thermodynamics and kinetics of the attack of a maximum of two hydroxyl radicals were studied, considering the effect of different protein environments at two different dielectric values (4 and 80). The obtained theoretical results explain how the radical attacks take place and provide new insight into the reasons for the experimentally observed preferential mechanism. These results indicate that, even though the attack of the first ^.OH radical on an aliphatic C atom is energetically favored, the larger delocalization and concomitant stabilization that are obtained by attack on the aromatic side chain prevail. Thus, the obtained theoretical results are in agreement with the experimental evidence that the aromatic side chain is the main target for radical attack and show that the first ^.OH radical is added onto the aromatic ring, whereas a second radical abstracts a hydrogen atom from the same position to obtain the oxidized product. Moreover, the results indicate that the reaction can be favored in the buried region of the protein.     

Enantiomeric Separation of Non-Protein Amino Acids by Chiral Ligand-Exchange High-Performance Liquid Chromatography

Abstract

The enantiomeric separation by high-performance liquid chromatography of underivatized non-protein amino acids was investigated by using a column packed with octadecylsilanized silica coated with N,S-dioctyl-D-penicillamine as a chiral ligand-exchange phase (Sumichiral OA-5000). Excellent to good separations of enantiomers were achieved with a variety of nonprotein amino acids carrying aliphatic or aromatic side-chains by optimizing the amount (0-20%, v/v) of the organic component (2-propanol) and the concentration (1-5 mM) of the complexing metal ion (Cu²⁺) in the hydro-organic eluent.     

以苯丙氨酸为例刍议芳香族氨基酸的生物合成机理

从磷酸烯醇式丙酮酸和4-磷酸赤藓糖为始探讨了3种芳香族氨基酸合成代谢共享的分支酸合成途径,并以苯丙氨酸为例从多学科角度讨论分析其合成代谢的独特性.通过多学科角度展示了生物体内不同代谢路径之间的关联及相似性,旨在展示一种教学新模式,帮助学生建立起跨学科内容的学习及归纳方法.     

高效毛细管电泳法在芳香族手性氨基酸与年龄的关系研究中的应用

建立了芳香族手性氨基酸的高效毛细管电泳的分离测定方法,在最佳实验条件下,测定了平均年龄为27±2和74±4岁的两组健康者血浆中D、L-苯丙氨酸、色氨酸和酪氨酸的含量.统计分析表明,血浆中芳香族手性氨基酸的含量与人类年龄之间具有一定关系.     

Buffer Influence on the Amino Acid Silica Interaction

Protein-surface interactions are exploited in various processes in life sciences and biotechnology. Many of such processes are performed in presence of a buffer system, which is generally believed to have an influence on the protein-surface interaction but is rarely investigated systematically. Combining experimental and theoretical methodologies, we herein demonstrate the strong influence of the buffer type on protein-surface interactions. Using state of the art chromatographic experiments, we measure the interaction between individual amino acids and silica, as a reference to understand protein-surface interactions. Among all the 20 proteinogenic amino acids studied, we found that arginine (R) and lysine (K) bind most strongly to silica, a finding validated by free energy calculations. We further measured the binding of R and K at different pH in presence of two different buffers, MOPS (3-(N-morpholino)propanesulfonic acid) and TRIS (tris(hydroxymethyl)aminomethane), and find dramatically different behavior. In presence of TRIS, the binding affinity of R/K increases with pH, whereas we observe an opposite trend for MOPS. These results can be understood using a multiscale modelling framework combining molecular dynamics simulation and Langmuir adsorption model. The modelling approach helps to optimize buffer conditions in various fields like biosensors, drug delivery or bio separation engineering prior to the experiment.