脱水淫羊藿素的电喷雾多级串联质谱研究

研究了脱水淫羊藿素的电喷雾质谱行为，结果表明：该化合物在正、负离子模式下，均可得到较好的电喷雾质谱信息，且在负离子模式下电喷雾质谱分析的灵敏度较高；运用电喷雾碰撞诱导解离技术，发现正离子和负离子模式下的裂解方式虽有相似之处但并不完全相同；分别阐明了该化合物在正、负离子模式下的电喷雾质谱碎裂规律。     

芹菜素的电喷雾萃取电离串联质谱

采用实验室自制的电喷雾萃取电离源(EESI),结合串联质谱(MSn)技术,对芹菜素这一典型的黄酮类活性化合物的质谱行为进行了研究。实验表明,在正、负离子检测模式下,该化合物均能得到较好的EESI-MS信号,且在负离子检测模式下灵敏度更高。通过对比芹菜素的EESI-MS和电喷雾电离质谱(ESI-MS)谱图发现,芹菜素在EESI-MS和ESI-MS中的裂解规律相似,但是EESI是一种比ESI更软的电离模式。根据对芹菜素EESI-MS特征碎片离子的分析,提出了芹菜素在EESI-MS中裂解的基本规律,为EESI-MS技术用于分析、鉴定复杂基质中痕量芹菜素奠定了理论和实验基础。     

黄连中小檗碱及其同分异构体的电喷雾质谱研究

利用电喷雾多级串联质谱对黄连经水提、醇沉、薄层色谱分离后，得到的组分进行了详细研究，并对其中小檗碱及其同分异构体表小檗碱的分子离子[M ]进行了源内碰撞诱导解离(CID)，在不同源内CID能量(25％，50％)下碰撞诱解离时存在区别，并提出其碎裂机理方面的解释。     

L-抗坏血酸电喷雾串联质谱行为研究

采用电喷雾串联质谱(ESI-MSn)技术, 结合氢/氘交换方法, 研究了L-抗坏血酸在正、负离子模式下的质谱行为. 实验表明, 电喷雾质谱能够方便地观测到实验条件下L-抗坏血酸的特征裂解方式和相应碎片; 实验发现毛细管温度对L-抗坏血酸的裂解方式产生显著的影响, 从不同毛细管温度下的相应质谱信号强度变化能观察到L-抗坏血酸及其降解产物的热稳定性差异. 因此, 根据串联质谱所观测到的L-抗坏血酸特征碎片离子, 提出了L-抗坏血酸的结构变化及其降解反应的可能机理和基本规律, 为现代质谱技术快速测定复杂基体样品中的痕量抗坏血酸奠定了实验基础.     

三氟乙酸增强的解吸电喷雾电离质谱成像用于脂质空间分布研究

将三氟乙酸添加到解吸电喷雾电离质谱的喷雾溶剂中,提高了对脂质的成像检测能力,使小鼠脑组织切片中能检测到的脂质种类从59种提高到71种.此外,该方法还可以促进脂质的质子化峰的形成并抑制钠和钾加合物的形成,有利于简化谱图解析过程并实现更好的定量分析.利用该方法实现了小鼠脑组织切片上多种脂质的空间相关性研究,为探索脂质间潜在的代谢途径提供了新手段,在神经学、临床等领域具有巨大的应用前景.     

Novel Rearrangement of Small Peptides in Electrospray Ionization Tandem Mass Spectrometry

Electrospray ionization mass spectrometry (ESI-MS) is a powerful method for sequencing peptides. A novel fragmentation pattern with the loss of a neutral fragment of 45 Da was observed with the dipeptides, tripeptides,tetrapeptides and pentapeptides containing phenylalanine or histidine residues. A novel rearrangement reaction with the extrusion of a formamide piece was studied and the rearrangement mechanism was proposed and confirmed by deuterium labeling experiments with ESI-MS^n and high-resolution mass spectrometry. These findings are potentially helpful in identifying the specific sequence pattern in the peptide sequencing.     

Coupling Electrochemistry with Probe Electrospray Ionization Mass Spectrometry

A new coupling of electrochemistry with mass spectrometry (MS) using probe electrospray ionization (PESI) is presented. Due to the high salt tolerance of PESI, the detection of electrochemical reaction products in room‐temperature ionic liquids (RTILs) is realized for the first time. Furthermore, PESI‐MS allows the analysis of electrochemical reaction products on different or multiple electrode surfaces. In addition, peptides and proteins fractionated through isoelectric focusing (IEF) in the presence of an external electric field can also be directly analyzed by using PESI‐MS, suggesting a new and rapid characterization means for the IEF technique. This study reveals the versatility of EC/PESI‐MS, which could have an impact in electrochemistry and bioanalysis fields.     

Laser Desorption Ionization Versus Electrospray Ionization Mass Spectrometry: Applications in the Analysis of Cluster Anions

Mass spectra of transition metal carbonyl cluster anions were recorded using laser desorption ionization time-of-flight (LDI-TOF) and electrospray ionization (ESI) techniques. The LDI spectra generally contain peaks corresponding the intact cluster together with extensive CO loss fragments ions whereas the ESI spectra exhibit peaks corresponding the intact cluster together with few (if any) CO loss fragment ions. The parameters of both techniques can be modified to vary the extent of fragmentation. In all cases no fragmentation of the metal core is observed. Overall, ESI is a more informative method for the analysis of these types of cluster anions.     

Toward Depth-Resolved Analysis of Plant Metabolites by Nanospray Desorption Electrospray Ionization Mass Spectrometry

Nanospray desorption electrospray ionization (nano-DESI) is one of the ambient desorption ionization methods for mass spectrometry (MS), and it utilizes a steady-state liquid junction formed between two microcapillaries to directly extract analytes from sample surfaces with minimal sample damage. In this study, we employed nano-DESI MS to perform a metabolite fingerprinting analysis directly from a Hypericum leaf surface. Moreover, we investigated whether changes in metabolite fingerprints with time can be related to metabolite distribution according to depth. From a raw Hypericum leaf, the mass spectral fingerprints of key metabolites, including flavonoids and prenylated phloroglucinols, were successfully obtained using ethanol as a nano-DESI solvent, and the changes in their intensities were observed with time via full mass scan experiments. In addition, the differential extraction patterns of the obtained mass spectral fingerprints were clearly visualized over time through selected ion monitoring and pseudo-selected reaction monitoring experiments. To examine the correlation between the time-dependent changes in the metabolite fingerprints and depth-wise metabolite distribution, we performed a nano-DESI MS analysis against leaves whose surface layers were removed multiple times by forming polymeric gum Arabic films on their surfaces, followed by detaching. The preliminary results showed that the changes in the metabolite fingerprints according to the number of peelings showed a similar pattern with those obtained from the raw leaves over time.     

皂苷的电喷雾负离子多级串联质谱研究

皂苷作为一类结构比较复杂的糖苷类化合物 ,广泛地存在于植物和海洋生物中 .现代医学研究表明 ,皂苷类化合物具有十分广泛的药理作用 .目前 ,在我国许多以皂苷类化合物为主要有效成分的药物都具有很好的疗效 .因此研究人员对于皂苷类化合物的结构研究有着愈来愈浓厚的兴趣 .然而皂苷类化合物具有极性大、难挥发、分子量大等特点 ,给分离纯化及结构鉴定带来很大的困难 .对于这类化合物结构的研究远远落后于生物碱和黄酮 .目前采用质谱技术测定皂苷类化合物的结构已有文献报道 ,但多局限于正离子质谱[1～ 6] ,对于负离子质谱仅限于 MS/ MS质…     

SNP的电喷雾串联质谱研究

采用电喷雾串联质谱技术对两组单核苷酸多态性(SNP)样品进行了研究,初步研究结果显示应用串联质谱可快速鉴定SNP分型以及确定SNP位点。采用16.3 mmol/L三乙胺(TEA)-400 mmol/L六氟异丙醇(HFIP)缓存溶液,电喷雾负离子模式下,长度为20 bp的寡核苷酸的MS扫描谱图显示其母离子呈较宽的多电荷态分布。选择低电荷态[M-4H]4-母离子,碰撞能为54 eV时,MS/MS扫描得到丰富的碎片离子,通过鉴定特征离子碎片(w和a-B离子系列)可确定其序列。     

Functionality,Effectiveness, and Mechanistic Evaluation of a Multicatalyst‐Promoted Reaction Sequence by Electrospray Ionization Mass Spectrometry

A multicatalytic three‐step reaction consisting of epoxidation, hydrolysis, and enantioselective monoacylation of cyclohexene was studied by using mass spectrometry (MS). The reaction sequence was carried out in a one‐pot reaction using a multicatalyst. All reaction steps were thoroughly analyzed by electrospray ionization (ESI) MS (and MS/MS), as well as high‐resolution MS for structure elucidation. These studies allow us to shed light on the individual mode of action of each catalytic moiety. Thus, we find that under the epoxidation conditions, the catalytically active N‐methyl imidazole for the terminal acylation step is partially deactivated through oxidation. This observation helps to explain the lower efficiency of the catalyst in the last step compared to the monoacylation performed separately. All reactive intermediates and products of the reaction sequence, as well as of the side‐reactions, were monitored, and we present a working mechanism of the reaction.     

基质辅助激光解析电离质谱和电喷雾质谱共同快速确证达托霉素结构

运用基质辅助激光解析电离-飞行时间串联质谱(MALDI-TOF/TOF MS)和电喷雾-四级杆-飞行时间质谱(ESI-Q-TOF MS)快速确证环脂肽达托霉素的结构。首先,ESI检测达托霉素相对分子量为1619.7107,与理论值偏差0.0007。选择其双电荷峰m/z 809.848作为母离子进行ESI串联质谱(MS/MS)测定,成功匹配了达托霉素环外氨基酸序列C9H19CO-Trp-Asn-Asp。其次,优化Li OH裂解达托霉素的实验条件,以MALDITOF/TOF MS监测开环效果,获得95%以上的开环样本后,分别运用MALDI和ESI进行MS/MS测定,达托霉素开环产物的b+和y+全部被匹配,达托霉素全部氨基酸序列得到确证。最后,对开环产物的ESI-MS/MS条件进一步优化,获得了丰富的低端碎片离子,解析了脂肪酸链结构,并绘制了脂肪酸链的裂解图。本方法快速、简便、准确,是确证环脂肽类化合物结构的可靠方法。     

Direct Determination of Chlorpyrifos in Honey by Neutral Desorption-Extractive Electrospray Ionization Mass Spectrometry

Neutral desorption-extractive electrospray ionization mass spectrometry was used for the direct, rapid, and quantitative determination of chlorpyrifos in honey without pretreatment. Under the optimized conditions, the limit of detection was 1.64?ng/mL with a linear dynamic range from 10 to 1,000?ng/mL and relative standard deviations from 1.97 to 6.14%. The recoveries of fortified honey samples at 50 and 500?ng/mL were 82.02 and 109.28% with relative standard deviations of 4.02 and 4.34%, respectively. This protocol offers high sensitivity, good precision, rapid analysis, and high specificity in a complex matrix.     

Elucidation of O-Phosphoryl and N-Phosphoryl Amino Acids by Electrospray Ionization Tandem Mass Spectrometry

Mass spectroscopic characteristics of phosphoryl amino acids were studied in detail by positive and negative electrospray ionization mass spectrometry (ESI-MS) in conjunction with tandem mass spectrometry (MS/MS). Besides N-diisopropyloxyphosphoryl amino acids (N-DIPP-AA), O-phospho- and O-diisopropyloxyphosphoryl amino acids (O-DIPP-AA) were studied and compared to N-DIPP-AA. The fragmentation pathways of [M H]^ ,[M Na]^ and [M-H]^- ions of phosphoryl amino acids were summarized. In addition to several similar patterns, each of them showed its characteristic fragmention.     

电喷雾质谱法研究人参皂苷与溶菌酶的相互作用

用电喷雾质谱法研究了溶菌酶与人参皂苷Rg1和Re的非共价相互作用。非共价复合物的解离常数可以由溶菌酶和复合物的峰高直接计算得到。由各个体系得到的溶菌酶与Rg1和Re的一级解离常数KD, 1是一致的，但是二级解离常数KD, 2的差别较大。由此可以推断出复合物的峰高越强，结果的精密度越好。当固定溶菌酶的浓度不变时，复合物的解离常数会随着人参皂苷的浓度的增加而略微的增大。而当固定人参皂苷的浓度时，复合物的解离常数会随着溶菌酶的浓度的增加而减小。计算结果还证明了人参皂苷Rg1与溶菌酶的结合能力大于Re。     

金属硫蛋白的色谱/电喷雾电离质谱联用表征方法

通过反相液相色谱(RPLC)与电喷雾电离质谱(ESI-MS)的联用技术,对镉诱导金属硫蛋白标准物质MT-1和MT-2的结构进行表征分析。采用Vydac C8 反相色谱柱(250 mm×2.1 mm i.d., 5 μm, 30 nm),流动相A为pH 6.0的5 mmol/L乙酸铵水溶液,流动相B为pH 6.0的5 mmol/L乙酸铵的甲醇-水(体积比为1∶1)溶液,流动相流速为0.20 mL/min,在40 min内流动相B的体积分数从10%增加到37.5%进行梯度洗脱。分别用紫外(UV)和ESI-M     

土壤中一种新的尿素衍生物的电喷雾萃取电离质谱分析

采用电喷雾萃取电离串联质谱(EESI-MSⁿ)技术直接分析马尾松根际土壤溶液, 发现了一种不稳定的尿素衍生物3,3-二氨基-3-羟基丙酸. 为确证其结构, 以尿素为原料合成了该衍生物, 并采用EESI-MSⁿ分析合成产物. 结果表明, 合成产物与土壤溶液中的3,3-二氨基-3-羟基丙酸的EESI-MSⁿ分析结果相吻合, 说明土壤中确实存在该衍生物, 其可能是一种尿素在土壤里代谢过程的中间体. 本文结果表明, EESI-MS技术可以直接分析复杂基体样品中痕量物质的信号, 为研究尿素在土壤中的氮素转化机理提供了新的思路.     

牛油果中化学成分的内部萃取电喷雾电离质谱检测

采用内部萃取电喷雾电离质谱(iEESI-MS)技术,以甲醇作为萃取溶剂,无需样品预处理,在优化条件下分别对牛油果果肉和果皮中化学成分进行快速直接鉴定,并考察了不同成熟度牛油果果肉中化学成分的差异.实验结果表明,在负离子检测模式下,从果肉中鉴定出棕榈酸、硬脂酸、棕榈油酸、油酸和亚麻酸等12种有效营养成分,从果皮中鉴定出儿茶素、绿原酸等11种营养成分.利用正交偏最小二乘判别分析法(OPLS-DA)对不同成熟度的牛油果果肉的iEESI-MS指纹谱图数据进行分析发现,此方法能够有效判别不同成熟程度的牛油果且5种化学成分差异显著.本方法无需样品预处理、样品耗量少、分析速度快(单个样品检测时间小于1 min)且操作简便,为植物有效营养成分和医用价值的开发提供了一种快速质谱分析新方法.