电喷雾电离质谱法研究环肽对HIV-1调控区DNA的识别及其相关碎裂机理和稳定性

利用电喷雾电离质谱(ESI-MS)和二级质谱(MS/MS)研究了六种结构不同的环五肽, 环七肽以及环十肽与HIV-1调控区DNA的非共价键相互作用. 在研究中比较了不同识别分子与靶序列DNA结合的强弱, 发现环七肽CP5对靶点DNA具有高亲合性的结合. 用MS/MS法研究了环肽与DNA复合物的碎裂机理; 用升温实验研究了其热稳定性, 发现与CP5结合后能提高HIV-1双螺旋DNA的热稳定性.     

电喷雾质谱法研究聚酰胺、酰亚胺衍生物与HIV-1基因DNA的相互作用

利用电喷雾质谱(ESI-MS)研究了6种识别分子与HIV-1基因调控区DNA的非共价键相互作用. 在研究中比较了不同识别分子与靶序列DNA结合的强弱, 发现双萘酰亚胺衍生物4对此序列DNA具有高亲合性的结合, 并分析了识别分子与DNA复合物的碎裂机理以及结合模式.     

石墨烯和氧化石墨烯的表面功能化改性

石墨烯和氧化石墨烯由于特殊的电子、光学、力学性能已成为当今科学研究的热点.重点综述了近年来石墨烯和氧化石墨烯的表面功能化改性研究进展.首先介绍了石墨烯、氧化石墨烯的基本结构与性质.然后将表面功能化分为非共价键结合改性、共价键结合改性和元素掺杂改性.非共价键结合的功能化改性分为四类：π-π键相互作用、氢键作用、离子键作用以及静电作用.共价键结合的功能化改性分为四类：碳骨架功能化、羟基功能化、羧基功能化和环氧基功能化.元素掺杂改性分为N、B、P等不同元素的掺杂功能化.总结了石墨烯、氧化石墨烯基体与改性分子的相互作用和反应类型,以及改性产物的性能与应用.最后对石墨烯和氧化石墨烯在表面功能化改性方面的发展前景作了展望和预测.     

重组人受体蛋白FKBP12与新型神经生长促进剂形成非共价键复合物的电喷雾质谱研究

FKBP12,是免疫抑制剂FK506结合蛋白(FK506-Binding Proteins,FKBPs)家族的主要成员,因预计分子量为12×103u而得名.自1989年发现此蛋白以来,人们的研究主要集中于其介导的免疫抑制作用.1992年研究发现,FKBP在神经系统中的含量比在免疫系统中要高出50倍以上,其介导的FK506在体内外均可促进神经再生.这一发现使FKBP蛋白家族的研究再次成为热点,人们力求设计一类新型的FKBP结合药物,去除FK506的免疫抑制作用,作为神经再生促进剂而用于临床.大量研究结果表明能够与FKBP结合的小分子化合物确实具有良好的促神经再生的作用.GPI-1046是这种设计的1个代表化合物,在多种模型中都有神经营养作用.美国Guilford公司已对其类似物进行了专利保护.本文通过电喷雾质谱(ESI-MS)研究rhFKBP12和其小分子配体的非共价键相互作用,筛选能够与rhFKBP12非共价键结合的小分子化合物,与生物活性实验相结合,为新药研究提供依据.     

基于非共价相互作用的非富勒烯受体光伏材料研究进展

有机太阳能电池由于制备简单、成本低,而且易于制备大面积柔性电池,因而受到了研究人员的广泛关注.非富勒烯受体材料因具有合成相对简单、易于纯化、能级和带隙可调等优点,极大地促进了有机太阳能电池效率的提高.基于非富勒烯受体材料的太阳能电池已经成为目前有机太阳能电池的研究热点之一,而具有分子内非共价键相互作用的受体材料是非富勒烯受体体系的重要组成部分.通过引入O、F、N、Se等杂原子,形成分子内非共价键相互作用,可以有效提高非富勒烯受体材料的平面性和电荷迁移率,降低光学带隙并拓宽吸收光谱,从而进一步提高太阳能电池的光伏性能.本文介绍了近几年来基于分子内非共价键相互作用的聚合物和小分子非富勒烯受体材料的研究进展,并展望了其发展趋势和应用前景.     

一锅法合成可印刷室温磷光二氟化硼衍生物

纯有机室温磷光(RTP)材料因其潜在的应用价值而备受关注.迄今,多数已报道的有机RTP材料在晶态下发射出较强的RTP,但在溶液加工过程中易生成无定形态,从而失去RTP性能.本文通过一锅法两步反应,合成了含有多个甲氧基的二氟化硼衍生物(BF2-t PMO).晶体结构分析表明,多个甲氧基的存在构建了有效的分子间非共价相互作用.这些非共价键作用可抑制分子运动,保持较高的发光效率.此外,这些非共价键作用能够使其在溶剂处理后依然保持晶态性质,进而保持RTP性能.实验结果表明, BF2-t PMO可溶解在不同溶剂中且在溶剂蒸发后仍能保持相同的RTP特性,为易加工型RTP材料的设计提供了有效的策略.     

光谱法研究呋苄西林钠与牛血清白蛋白的作用

采用紫外、荧光、红外光谱法研究了磷酸缓冲液中呋苄西林钠(FBS)与牛血清蛋白(BSA)的相互作用。结果表明,FBS与BSA有较强的相互作用,FBS对BSA内源荧光有猝灭作用,静态猝灭是引起BSA荧光猝灭的主要原因。按照Stern-Volmer方程和双对数方程分析处理实验数据,得到了不同温度下FBS与BSA反应的结合常数和结合位点数,常温(26℃)下,分别为1.04×105和1.09;实验结果还表明,FBS与BSA之间的相互作用影响了BSA的二级结构,使其构象发生变化。     

苯胺蓝黑与人血清白蛋白的相互作用及对其构象的影响

利用荧光光谱和同步荧光光谱研究了不同温度下苯胺蓝黑与人血清白蛋白相互作用时的荧光猝灭及构象的变化情况。实验结果表明,苯胺蓝黑与人血清白蛋白之间可以发生相互作用,而且有较强的结合。同步荧光光谱研究了人血清白蛋白与苯胺蓝黑的相互作用中人血清白蛋白构象的变化,结果显示二者结合改变了蛋白质的微环境。热力学参数说明小分子与蛋白质的作用以疏水作用为主。     

纳升电喷雾串联质谱"序列对接法"确定多肽的加钠位点

用QuattroM icro三级四极串联质谱分析常见的20种氨基酸的加钠效果。结果表明,绝大多数氨基酸与钠离子的非共价键结合力很弱甚至没有,但脯氨酸和苯丙氨酸很容易形成加钠离子峰。采用“序列对接法”测出重组人酸性纤维细胞生长因子(rh-a FGF)C-端肽段的全序列,并确定钠离子的加成位点为该肽段的第6位脯氨酸(6Pro)。通过酸化样品溶液获得无加钠、无序列间隙的该肽全序列,与加钠肽段的序列一致。     

怎样讲述键的极性

在现行高中化学课本中,有关极性键和非极性键的概念是这样阐述的：“在单质分子中,同种原子形成的共价键,两个原子吸引电子的能力相同,共用电子对不偏向任何一个原子,这两个电子在键的中央出现的机会最多,成键的原子都不显电性。这样的共价键叫做非极性共价键,简称非极性键。”“在化合物的分子中,不同种原子形成的共价键,由于不同原子吸引电子的能力不同,共用电子对必然偏向吸引电子能力强的原子一方,也就是说,靠近吸引电子能力强的原子一方电子云比较密集。因而吸引电子能力强的原子就带部分负电荷,吸引电子能力较弱的原子就带部分正电荷,这样的共价键叫极性共价键,简称极性键”。     

纳升电喷雾串联质谱(Q-TOF)测序中Na+加合肽的分析

电喷雾串联质谱测序法是蛋白质组研究中蛋白质鉴定的最有力的手段之一。肽段离子在ESI-Q-TOF中往往以多电荷形式出现(2～4个电荷),其中m／z在500～1000之间带双电荷的离子最适合测序。但这样的肽段很容易和Na+加合,有时加合峰的相对强度比原肽段高很多,有时甚至只有加合峰。Na+加合肽的序列分析比较困难,因数据库查寻不支持Na+加合,且Na+加合是非氨基酸特异的,序列分析中不能按修饰编辑,一旦有一个氨基酸的序列发生偏差,整个肽段序列就不正确。因此,Na+加合肽的序列分析很重要。在Na+加合肽序列分析中,寻找m／z相差22Da的离子,以其为起点分别按m／z从高到低和从低到高进行分析,可得到完整序列,用序列进行数据库检索可鉴定蛋白质,本文用此方法分析了5个Na+加合肽的序列,鉴定5个蛋白质。Na+加合位点分别为丝氨酸S、脯氨酸P和酪氨酸Y。     

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。     

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.     

On the sodium and lithium ion affinities of some α-amino acids

The decomposition of 59 different cluster ions (generated by fast atom bombardment) consisting of two different amino acids and a sodium ion was analysed. The only fragment ions of significant abundance could be assigned to sodium ion-bound amino acids. Assuming that the most abundant ion in the fragment ion spectrum corresponds to the amino acid with the highest sodium ion affinity (SIA), the 20 common α-amino acids could be ordered with increasing sodium ion affinity as follows: Gly, Ala, Cys, Val, (Leu, Ile), Ser, Met, Thr, (Phe, Pro), Asp, Tyr, (Glu, Lys), Trp, Asn, Gln, His, Arg. Quantitative determinations were carried out by comparison of the lithium ion affinity (LIA) of Ala with that of dimethylformamide (DMF) in a fragment ion scan of the ion-bound dimer Ala—Li⁺—DMF. LIA(Ala) was calculated from LIA(Ala) = LIA(DMF) – (1/C)ln[I(AlaLi⁺)/I(DMF—Li⁺)], where the constant C was estimated from measurements of proton-bound amine–amino acid clusters. From fragment ion analysis of nine other Li⁺-bound α-amino acid dimers, the following lithium ion affinities were obtained: Gly 51.0, Ala 52.6, Sar 53.5, α-aminobutyric acid 53.7, glycine methyl ester 54.7 and Val 54.8. SIA(Ala) was estimated to be 75% of the lithium ion affinity and from fragment ion analysis of ten Na⁺-bound α-amino acid dimers the following sodium ion affinities were obtained: Gly 37.9, Ala 39.4, α-aminobutyric acid 40.3, Val 41.0, glycine methylster 41.0 and Sar 41.2.     

Formation of metal complex ions from amino acid in the presence of Li+, Na+ and K+ by electrospray ionization: metal replacement of hydrogen in the ligands

Alkali metal cations easily form complexes with proteins in biological systems; understanding amino acid clusters with these cations can provide useful insight into their behaviors at the molecular level including diagnosis and therapy of related diseases. For the purpose of characterization of basic interaction between amino acids and alkali metal, each of the 20 naturally occurring amino acids were ionized in the presence of lithium, sodium and potassium cations by electrospray ionization, and the resulting product ions were analyzed. We focus our attention on the gas phase alkali metal ion-proton exchanged complexes in current study, specifically complexes with serine, threonine, asparagine and glutamine, which share characteristic pattern unlike other amino acids. All amino acids generated [M + H](+) and [M + Na](+) ions, where M stands for the neutral amino acid. Serine, threonine, asparagine and glutamine generated cluster ions of [nM - nH + (n + 1)Na](+) and [nM - (n - 1)H + (n - 1)Na + K](+) , where n = 1-7. While the (M - H + Li) and (M - H + K) species were not observed, the neutral (M - H + Na) species formed by proton-sodium cation exchange had a highly stable cyclic structure with ketone and amine ligand sites, suggesting that (M - H + Na) serves as a building block in cluster ion formation. Cluster ion intensity distributions of [nM - nH + (n + 1)Na](+) and [nM - (n - 1)H + (n - 1)Na + K](+) showed a magic number at n = 3 and 4, respectively. Extensive B3LYP-DFT quantum mechanical calculations were carried out to elucidate the geometry and energy of the cluster ions, and they provided a reasonable explanation for the stability and structure of the cluster ions.     

Amino acid analysis using amine-sensitive membrane electrodes

A method for determining specific amino acids is described, based on the detection of the amine formed by the enzymatic reaction of an amino acid with decarboxylase, using an amine-sensitive membrane electrode. l-Tyrosine and l-phenylalanine are considered as examples. The corresponding amines tyramine and phenethylamine, respectively, were selectively detected by using a poly(vinyl chloride)-based membrane electrode containing sodium tetrakis[3,5- bis(trifluoromethyl)phenyl]borate as an ion exchanger and tricresyl phosphate as a solvent mediator. The detection limits of l-tyrosine and l-phenylalanine were 20 and 50μM, respectively. The response characteristics of electrodes were compared by changing ion exchangers and solvent mediators.     

Anion influence on extraction and transport of amino acid methyl esters by functionalised calix[4]arene

The liquid–liquid extraction of a series of amino acid methyl esters has been carried out with functionalised calix[4]arene (5,11,17,23-tetrakis(N-methylpiperazino)-25,26,27,28-tetrahydroxycalix[4]arene) from an aqueous phase into a chloroform phase as ion pairs in the presence of picrate ion or tropaeolin 00 as counter ion in order to study the molecular recognition properties of this receptor. The active transport assisted by pH gradient of amino acids as ion pairs through liquid membrane employing the functionalised calix[4]arene as carrier has been investigated. The results showed that the receptor exhibits good extractability towards amino acids and it can also act as carrier through liquid membrane aiming to the separation of amino acids. It was highlighted that the anion nature used as counter ion, the structure of calix[4]arene, and the structure of amino acids are responsible for the experimental results obtained. High yields in both amino acids extraction and transport were obtained for picrate ion used as counter ion.     

碳酸氢铵和食盐制纯碱工业中间产物的分析

研究了由碳酸氢铵和食盐为原料生产纯碱的中控分析方法。生产过程中，中间产物母液中共存的离子有Na^ 、HCO3^-、CO3^2-、NH4^ 、Cl^-，其中Na^ 采用钠离子选择性电极测定，此文主要研究了其余四种离子的滴定分析法。     

Use of capillary electrophoresis and laser-induced fluorescence for attomole detection of amino acids

A capillary electrophoresis and laser-induced fluorescence (CE-LIF) method was developed to identify and quantitate at amol (10(-18)) concentration. Amino acids were derivatized with 3-(4-carboxybenzoyl)-2-quinoline-carboxaldehyde prior to CE-LIF analysis. The assay was developed by varying the sodium borate concentration, buffer pH, operating voltage, and operating temperature. A run buffer system containing 6.25 mM borate, 150 mM sodium dodecyl sulfate, and 10 mM tetrahydrofuran (pH 9.66) at 25 degrees C, and 24 kV provided analysis conditions for a high-resolution, sensitive, and repeatable assay of amino acids. The rate of derivatization, stability of the labeled amino acids, and amino acid quantitation varied for each amino acid. Amino acids were detected with greater efficiency by this method than automated HPLC amino acid analysis. The repeatability of the assay ranged from 0.3 to 0.9% within a day and 0.7 to 1.5% between analysis days. Bacterial amino acid utilization in a chemically defined medium was successfully monitored using this method. This work defines a sensitive and repeatable method for the detection of amino acids during bacterial metabolism.