质谱技术在免疫分子的结构研究中的应用

质谱技术用于生物大分子的研究具有直接、简单、快速、经济等优点.近十年来,基质辅助激光解吸质谱(MALDI-MS)和电喷雾质谱(ESI-MS)在免疫学领域的研究中作出了重要贡献.本文着重对抗原、抗体、抗原-抗体复合物、抗原决定簇等免疫分子结构的质谱研究作一评述.大体分为四方面内容:免疫分子的分子量、翻译后修饰、异质性、构象变化的分析;质谱指纹图的取得和串联质谱测序;抗原-抗体复合物的证明;B-细胞表位和T-细胞表位序列的测定.这些研究结果对于理解免疫分子的免疫功能、对于疾病的早期诊断、对于发展新药和疫苗具有重要意义.

Stereoselective polymerization of rac-lactide with a bulky aluminum/Schiff base complex

An aluminum/Schiff base complex {[2,2-dimethyl-1,3-propylenebis(3,5-di-tert-butylsalicylideneiminato)](isopropanolato)aluminum(III) (2)} based on a bulky ligand and aluminum isopropoxide was prepared and employed for the stereoselective ring-opening polymerization (ROP) of rac-lactide (rac-LA). The initiator was characterized with nuclear magnetic resonance (NMR), crystal structure measurements, and elemental analysis. It contained a five-coordinate aluminum atom that was trigonal bipyramidal in the solid state according to the crystal structure measurements. The two conformational stereoisomers of 2 exchanged quickly on the NMR scale. Compound 2 polymerized rac-LA into a crystalline polymer that was characterized with H-1 NMR, wide-angle X-ray diffraction, electrospray ionization mass spectrometry, and gel permeation chromatography. The kinetics of the polymerization were first-order in both the monomer and initiator, and there was a linear relationship between the rac-LA conversion and the number-average molecular weight of poly(rac-LA) with a narrow molecular distribution (1.04-1.08). These features showed that the polymerization was well controlled. The high melting temperature (196-201 degreesC) and isotacticity of poly(rac-LA) indicated that complex 2 was a highly stereoselective initiator for the ROP of rac-LA.

Stereoselective polymerization of rac-lactide using a monoethylaluminum Schiff base complex

A monoethylaluminum Schiff base complex (2) with formula LA1Et (L = N,N'-(2,2-dimethylpropylene)bis(3,5-di-tei-t-butylsalicylideneimine) was synthesized and employed for the stercoselective ring-opening polymerization of rac-lactide (rac-LA). The complex 2 was characterized by nuclear magnetic resonance, crystal structure, and elemental analysis. It contains a five-coordinate aluminum atom with distorted trigonal bipyramidal geornetry in the solid state. In the presence of 2-propanol, 2 showed high stereoselectivity for the polymerization of rac-LA. The polymerization yielded crystalline poly(rac-LA) with a high melting temperature (193-201 degreesC). NMR, differential scanning calorimetry, and wide-angle X-ray diffraction indicated that the poly(rac-LA) was highly isotactic, and a stereocomplex was formed between poly-L- and poly-D-lactide block sequences. By the analysis of electrospray-ionization mass spectrometry and H-1 NMR, the polymer was demonstrated to be endcapped in both terminals with an isopropyl ester and a hydroxy group, respectively. The polymerization was of first order in rac-LA concentration. The relationship between the rac-LA conversion and molecular weights of the polymer was linear so that the polymerization could be well controlled.

Study on mechanism of interaction between Eu3+ and microperoxidase-11

The interaction mechanism between Eu3+ and microperoxidase-II (MP-11) in the aqueous solution was investigated using the UV-vis absorption spectroscopy, cyclic voltammetry and electrospray ionization mass spectrometry. It was found that one Eu3+ ion can coordinate with two carboxyl oxygen of two propionic acid groups of the heme group in the MP-11 molecule, leading the increase in the nonplanarity of the porphyrin ring and exposure degree of Fe(III) in the heme group. Therefore, the reversibility of the electrochemical reaction and the electrocatalytic activity of MP-11 for the reduction of oxygen are increased.

芍药苷的电喷雾串联质谱研究

采用电喷雾串联质谱(ESI-MSn)技术,结合H/D交换方法,在正、负离子检测模式下对白芍药材中主要成分芍药苷的质谱裂解规律进行了系统研究.实验结果表明,该化合物在正、负离子模式下均得到较好的质谱信息,且在正离子模式下,电喷雾质谱分析的灵敏度更高.同时获得了其质谱裂解规律,为白芍中其它化合物的分析鉴定提供了有效的质谱方法.

pH值对人参皂苷溶出影响规律的液质联用研究

采用液质联用(HPLC-ESI-MSn)技术,对不同pH值(2.4~11.2)条件下人参皂苷的溶出变化规律进行了系统研究,并提出了不同人参皂苷化合物的特征质谱裂解规律.实验结果表明,中性及碱性溶液对人参皂苷的溶出影响不大,仅仅在溶出总量上有所差别;而酸性是影响人参皂苷溶出的一个主要因素,随着水溶液酸性的增强(pH<4),人参皂苷溶出的种类明显减少,表明较强酸性条件下人参皂苷的溶出受到了抑制.

刺五加寡糖的电喷雾多级串联质谱研究

采用小柱层析法从刺五加中分离得到刺五加寡糖类系列化合物(刺五加二糖～刺五加六糖).实验结果表明, 在正离子模式下的ESI-MS谱中, 此类化合物呈现出特征的加合离子峰簇[M+Na]+/[M+K]+或[M+H2O+Na]+/[M+H2O+K]+, 可以确定其分子量; 在负离子模式下的ESI-MS谱中, 刺五加寡糖易形成[M-H]-/[M+nH2O-H]-(n<3).还利用电喷雾多级串联质谱(ESI-MSn)对刺五加三糖进行了系统的研究, 推断出刺五加三糖的组成与结构.

雪上一支蒿中乌头碱类生物碱的电喷雾串联质谱分析

利用电喷雾串联质谱 (ESI MS MS)对雪上一支蒿的乙醇提取液进行了直接分析 ,方法简便 ,直观 ,用样量少。ESI MS可以给出分子量信息 ,MS MS方法则可以从复杂体系中获得结构信息。在雪上一支蒿中发现乌头碱、去氧乌头碱及它们的水解产物和脂类生物碱等共 1 9种二萜生物碱 ,其中脂类生物碱为首次在该植物中发现

淫羊藿甙及其与金属离子配合物的电喷雾多级串联质谱研究

利用电喷雾多级串联质谱 ( ESI-MSn)研究了淫羊藿甙及其与金属离子形成的配合物 ,获得淫羊藿甙的质谱碎裂规律 ;并对淫羊藿甙与铝离子、铁离子形成的配合物结构进行了初步确定。结果表明 :淫羊藿甙与铝离子、铁离子可形成比较稳定的 2∶ 1的配合物

Capillary liquid chromatographic-high-resolution mass spectrometric analysis of ribonucleotides

A method of capillary HPLC-high-resolution MS was developed for the trace analysis of ATP, GTP, dATP and dGTP Dimethylhexylamine (DMHA) was used as ion-pairing agent for the HPLC retention and separation of the nucleotides and positive ion electrospray time-of-flight MS was used for the detection. The application of capillary HPLC allowed minimal usage of DMHA while providing excellent peak retention and resolution, which significantly reduced the ion suppression in electrospray ionization-MS analysis and thus increased the sensitivity. Adduct ions of nucleotides and DMHA were used as quantitative ions in order to achieve the best sensitivity. DMHA concentration at 5 mM in the aqueous mobile phase at pH 7 was found to be the optimal conditions for the C Is capillary column. The method was applied to determine ATP level in cultured C6 glioma cells that were treated with toxic concentrations of Zn. The results showed that the cellular ATP level decreased from 2.7 pmol/cell (<10% cell death) in average control cell samples to 0.36 pmol/cell as the concentration of Zn increased to 120 mg/l (>35% cell death) in culture medium.

白山草乌中二萜生物碱的电喷雾串联质谱分析

利用电喷雾串联质谱 ( ESI-MS2 )对吉林省白山市地产草乌的乙醇提取液进行了直接分析 ,方法简便 ,直观 ,用样量少。ESI-MS可以给出分子量信息 ,MS2 方法则可以从复杂体系中获得结构信息。在该植物中发现中乌头碱、次乌头碱乌头碱及中乌头碱的水解产物和脂类生物碱等九种二萜生物碱

刺五加叶中黄酮类化合物的分析

利用电喷雾多级串联质谱 (ESI MSn)技术 ,分析了刺五加叶中黄酮类化合物 ,并根据黄酮类化合物的特征显色反应 ,采用紫外 可见分光光度法 ,对刺五加叶中总黄酮的含量进行了测定。分析结果表明 :刺五加叶含有槲皮素及其相关的黄酮甙类化合物 ,其含量达 37.2 5 %。

蛋白质分子量测定过程中的酸效应

在基质辅助激光解吸电离飞行时间质谱 (MALDI TOF MS)和电喷雾质谱 (ESI MS)测定蛋白质分子分子量的过程中 ,适当提高样品的酸度 ,可提高分析测试的灵敏度。在选定最佳样品分子浓度的基础上 ,通过适当加入三氟乙酸 (TFA)来调整测试样品的酸度 ,准确测定了标准蛋白质 溶菌酶 (lysozyme)的分子量 ,并且对蛋白质分子在“软电离”质谱中 ,受酸效应的影响进行了初步探讨

电喷雾多级串联质谱快速鉴定木鳖子皂苷

利用电喷雾正负离子多级串联质谱相结合的方法 ,并结合皂苷部分醇解产物和皂苷元的质谱数据 ,鉴定了木鳖子皂苷的结构 ,推断了木鳖子皂苷的电喷雾质谱机理

人参四逆汤抗休克作用的有效组分成分分析

分析人参四逆汤抗失血性休克作用的提取组分 S- 1和 S- 7的组成成分。方法　结合硅胶色谱柱分离 ,利用 ESI/MSn、MAL DI- TOF/MS等技术分析鉴定 S- 1和 S- 7的化学成分。结果　从人参四逆汤水煎液的抗休克作用的有效组分 S- 7中分析和鉴定了人参皂苷 - Ra1 、- Ra2 、- Rb1 、- Rb2 、- Rb3、- Rc、- Rd、- Re、- Rg1 、- Rg2 、- Rg3、- Rf等 12种人参皂苷 ;从有效组分 S- 1中检出下列二萜生物碱成分 :苯甲酰次乌头碱油酸酯 (14 - benzoylhypaconine- 8-linoleate,HAL )、苯甲酰去氧乌头碱油酸酯 (14 - benzoyldeoxyaconine- 8- oleate,HAO )、苯甲酰次乌头碱棕榈酸酯(14 - benzoylhypaconine- 8- palmitate,HAP)、苯甲酰中乌头碱 (benzoylmesaconitine,BM)、苯甲酰乌头碱 (benzoyla-conitine,BA)、苯甲酰次乌头碱 (benzoylhypaconitine,BH)。结论...