游离芳香氨基酸和半胱氨酸对光诱导高铁肌红蛋白还原的影响

肌红蛋白(Myoglobin,Mb)中血红素辅基不仅具有储氧功能,也能吸收特定波长的光而影响蛋白功能表达。实验发现,部分游离的氨基酸对光诱导高铁肌红蛋白(metM b,Fe(III)-Mb)的还原过程及还原程度都有重要作用,因此,本文采用紫外-可见吸收光谱、圆二色谱、三维荧光光谱法,在光照体系中加入拥挤试剂来模拟细胞内拥挤环境,研究芳香氨基酸[色氨酸(Trp)、苯丙氨酸(Phe)、酪氨酸(Tyr)、半胱氨酸(Cys)]对metM b还原的影响。结果表明,含-OH或-SH的氨基酸(Tyr、Cys)能使metM b发生较好的光还原,无-OH或-SH基团的氨基酸(Trp、Phe)对metM b的光还原作用较弱,氨基酸促进metM b光还原的整个过程可能是分子间电子转移的过程。metM b在拥挤环境聚蔗糖70(Ficoll 70)中的光诱导还原程度比在稀溶液中高,拥挤试剂Ficoll70对蛋白的二级结构起保护作用,能够稳定血红素微环境。     

The Biosynthesis of Aromatic Amino Acids and its Regulation

Microorganisms synthesize the aromatic amino acids phenylalanine, tyrosine, and tryptophan, as well as the related compounds p-aminobenzoic acid, tetrahydrofolic acid, p-hydroxybenzoic acid, ubiquinone, vitamin K, and nicotinic acid, by a highly branched route passing through shikimic acid. The biosynthesis is not regulated in the same way in all the organisms studied. The regulation is strongly dependent on the ability of the enzymes involved to be resolved into isozymes, their ability to be inhibited, and their activation, repression, and induction.     

水溶液中几种芳香族氨基酸π-π自堆叠作用

利用精密的流动混合微量热法测定了298.15 K时D/L-色氨酸、L-色氨酸、L-组氨酸和L-苯丙氨酸四种天然芳香族氨基酸水溶液的稀释焓, 根据所建立的拟等步自堆叠作用的化学模型对实验数据进行了处理, 计算得到模型参数K△Hm. 该化学作用参数与McMillan-Mayer理论模型中的焓对作用系数具有高度一致性, 即hxx=K△Hm. 结合文献报道的结果, 认为芳核π-π自堆叠作用在本质上是一种特殊的疏水-疏水作用, 一般表现为吸热效应; 取代基空间位阻、芳核以外部分的静电、氢键和手性选择性作用等对芳核π-π自堆叠作用有显著影响; 组合参数K△Hm实际上描述了芳核π-π自堆叠作用平衡及焓变的综合效应.     

人血浆中游离氨基酸的离子色谱/积分脉冲安培法分析

采用离子色谱积分脉冲安培法,在AminoPae PA10色谱柱上,用250 mmol/L的NaOH溶液和1.00 mol/L的乙酸钠溶液为淋洗液分离血浆中的游离氨基酸,以Au为工作电极,pH-Ag/AgCl电极为参比电极,检测了血浆中的16种游离氨基酸,无需衍生,检出限为0.11～3.3μg/L,样品加标回收率在87%～117%范围内.     

Determination of Proteinogenic Amino Acids in Human Plasma by Capillary Electrophoresis with Contactless Conductivity Detection

Capillary electrophoresis (CE) with contactless conductivity detection (CCD) represents a viable alternative to liquid chromatography in the analysis of amino acids (AA) in human plasma. After optimizing the composition of the background electrolyte (BGE), and introducing simple plasma pretreatment to remove spurious protein components, the CE/CCD methods allows determination of 18 from 20 proteinogenic AAs, three nonproteinogenic AAs and creatinine in 60 minutes. AAs are separated in their cationic forms in BGE containing 1.7 M acetic acid and 0.1% hydroxyethylcellulose, pH 2.2. LODs for individual AAs vary in an acceptable range with minimum of 4.3 μM for Arg and maximum of 42.9 μM for Cys. Mean concentrations and concentrations ranges for AAs in human plasma samples from 9 healthy individuals are found to agree well with those determined by an LC method in other two laboratories.     

Analysis of Thermal Decomposition Patterns of Aromatic and Heteroaromatic Amino Acids

Abstract

Differential enthalpic analysis of the thermal degradation of aromatic and heteroaromatic amino acids provides thermograms which are characteristic of specific amino acids (e.g. phenylalanine, tyrosine, tryptophan or histidine). Curve resolution of the resulting thermograms suggests that a minimum of three reactions are involved in the degradation (within the temperature limits of 500–620 [ddot]K) and provides T_M values for each of these concurrent reactions.     

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.     

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.     

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。     

高效液相色谱法快速测定血清中的芳香族氨基酸

采用高效液相色谱-紫外检测法分离测定了血清中的芳香族氨基酸。采用的色谱柱为Waters Nova-Pak C18柱(4 μm,150 mm×3.9 mm i.d.),流动相为乙腈-水(体积比为6∶94,pH 3.4)溶液,流速为1.0 mL/min,检测波长为215 nm。血清标本经5%(体积分数)高氯酸溶液去除蛋白质后取上清液直接进样,10 min内完成测定。探讨了流动相的pH及其有机相的比例、蛋白质沉淀剂以及检测波长等因素对分离度和灵敏度的影响。考察了其他10余种氨基酸、多巴胺类等物质对目标组分检测的     

Use of Micelles in the TLC Separation of Polynuclear Aromatic Compounds and Amino Acids

Abstract

The polynuclear aromatic compounds (PNA): anthracene, napthalene, phenanthrene, pyrene, pyrenecarboxaldehyde, benzo (a) pyrene, benzo (e) pyrene, perylene and fluorene can be chromatographed on polyamide TLC sheets using an aqueous micellar solution cf sodium dodecylsulfate (SDS) as the mobile phase. Reversed micellar solutions (of sodium dioctylsulfosuccinate) were used in a reverse phase chromatographic separation of amino acids. Some amino acids tended to streak slightly rather than move as discrete spots. Conditions could be adjusted, however, so that most of the amino acids and all PNA's would move as spots.     

一种新型主客体荧光探针对人体氨基酸的识别研究

本文研究了环戊基全取代六元瓜环(CyP₆Q[6])与2-(β-吡啶)-1H-咪唑[4,5-f][1,10]菲咯啉盐酸盐(即Ar-IPHS)的主客体相互作用,并利用CyP₆Q[6]可使Ar-IPHS产生强烈荧光的性质制备了Ar-IPHS@CyP₆Q[6]荧光探针用以识别氨基酸。结果表明,探针可高效识别甘氨酸、赖氨酸、甲硫氨酸,检出限分别为2.27×10^-6、1.359×10^-5和1.690×10^-5mol/L。     

某些芳香族氨基酸作探针荧光猝灭法测定秋水仙碱

在适当的酸性介质中, 秋水仙碱(COL)能与色氨酸(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, 此时将引起上述氨基酸的荧光发生猝灭, 最大猝灭波长分别位于350 nm (Trp), 304 nm (Tyr), 284 nm (Phe). 其荧光猝灭值(ΔF)在一定范围内与秋水仙碱成正比. 当用Trp和Tyr作探针时, 荧光猝灭法测定秋水仙碱具有高灵敏度, 其检出限分别为15.1 ng/mL (3.78×10^－8 mol/L)和19.8 ng/mL (4.96×10^－8 mol/L). 文中研究了适宜的反应条件和影响因素, 考察了共存物质的影响, 表明方法有良好的选择性, 可用于秋水仙碱的测定. 文中讨论了复合物的组成、结合力和结合模式. 通过温度的影响以及Stern-Volmer作图, 判断该反应为静态猝灭反应, 它们的结合常数(K)在25 ℃时分别为9.7×10⁶ (COL-Trp), 8.9×10⁶ (COL-Tyr)和6.3×10⁵ (COL-Phe). 其作用力主要是芳基堆集作用和氢键结合作用, 而芳基堆集作用是发生荧光猝灭的主要原因.     

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.     

LC Determination of Amino Acids in Rat Plasma with Fluorescence Detection: Application to Exercise Physiology

An LC method for the determination of 20 amino acids (AAs), using 1,2-Benzo-3,4-dihydrocarbazole-9-ethyl chloroformate (BCEOC) as fluorescent labeling reagent, has been validated and applied for the analysis of AAs in rat plasma at three different states concerning exercise physiology. Identification of AA derivatives was carried out by LC-MS with electrospray ion (ESI), and the MS-MS cleavage mode of the representative tyrosine (Tyr) derivative was analyzed. Gradient elution on a Hypersil BDS C₁₈ column gave good separation of the derivatives. Excellent linear responses were observed and good compositional data could be obtained from as little as 50–200 μL of plasma samples. The contents of 20 AAs in rat plasma of three groups (24 rats, group A: quiet state, group B: at exercising exhaust, group C: 12 h after exercising exhaust) exhibited evident difference corresponding to the physiological states. Facile BCEOC derivatization coupled with LC-FLD-ESI-MS analysis allowed the development of a highly sensitive method for the quantitative analysis of trace level of AAs from plasma or other biochemical samples.