羟基卟啉衍生物的电喷雾多级串联质谱研究

研究了3种单羟基卟啉的电喷雾多级串联质谱,对其可能的裂解途径进行了归纳;结果表明,仅仅在苯环上无取代基的卟啉HPTPP中才能观察到失去活性的羟基或羟苯基的裂解碎片,苯环具有拉电子取代基的卟啉比具有推电子取代基的卟啉更容易裂解;由此可见,苯环上取代基性质对羟基卟啉的裂解方式有一定的影响。     

二肽衍生物的电喷雾质谱研究

基于HIV整合酶核心结构域,合成了以HIV整合酶为靶标的二肽衍生物,采用多级质谱技术（二级、三级）研究二肽衍生物在质谱条件下的化学键断裂途径,发现主要的断裂方式为：氨基与羰基间的NH-CO键的断裂以及N-(苯并噻唑-2-基)甲酰氨基与亚甲基间的CO-C间的断裂。     

电喷雾离子源正离子模式下环烯醚萜苷的质谱裂解行为

利用高分辨率四极杆-飞行时间串联质谱(Q-TOF MS/MS)对环烯醚萜苷同系组分7,8-环戊烯型和环戊烷型环烯醚萜苷在电喷雾正离子(ESI⁺)模式下的质谱裂解行为进行了研究. 在ESI⁺模式下, 环烯醚萜苷主要的质谱裂解途径是脱去母环上的功能基团, 如丢失H₂O, CO₂, CH₃OH, CH₃COOH和糖单元部分等, 由于它们均为葡萄糖苷, 所以共有碎片离子[Glc+Na]⁺(m/z 185.0). 环烯醚萜苷母核环上半缩醛结构的异构化造成二氢吡喃环的断裂, 但未发现与苷元部分在负离子(ESI^-)模式下相同的其它断裂. 环烯醚萜苷在ESI⁺模式下的断裂途径特征性不如其在ESI^-模式下的明显, 且灵敏度比后者低.     

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.     

表面活性剂的电喷雾质谱分析

采用不同的质谱采集模式分析了不同类型的表面活性剂。阳离子表面活性剂如氯化十二烷基二甲基苄基铵,适合正离子采集模式,准分子离子为其阳离子;阴离子表面活性剂如十二烷基苯磺酸钠,适合负离子采集模式,准分子离子为其阴离子;两性表面活性剂如氧化十四烷基二甲基胺,适合负离子采集模式,准分子离子为[M-H]^-;非离子表面活性剂如壬基酚聚氧乙烯（12）醚,适合正离子采集模式,准分子离子为[M＋Na]^-。     

Analytical Properties of Solid-substrate Electrospray Ionization Mass Spectrometry

Conventional electrospray ionization mass spectrometry (ESI-MS) uses a capillary for sample loading and ionization. Along with the development of ambient ionization techniques, ESI-MS using noncapillary emitters has attracted more interest in recent years. Following our recent report on ESI-MS using wooden tips (Anal. Chem. 83, 8201–8207 (2011)), the technique was further investigated and extended in this study. Our results revealed that the wooden tips could serve as a chromatographic column for separation of sample components. Sequential and exhaustive ionization was observed for proteins and salts on wooden tips with salts ionized sooner and proteins later. Nonconductive materials that contain microchannels/pores could be used as tips for ESI-MS analysis with sample solutions loaded to the sharp-ends only, since rapid diffusion of sample solutions by capillary action would enable the tips to become conductive. Tips of inert materials such as bamboo, fabrics, and sponge could be used for sample loading and ionization, while samples such as tissue, mushroom, and bone could form tips to induce ionization for direct analysis with application of a high voltage.

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。     

淫羊藿苷的电喷雾质谱研究

研究了淫羊藿苷的电喷雾质谱行为.结果表明,该化合物在正、负离子模式下均可得到较好的质谱信息,在负离子模式下,采用H/D交换方法,证明淫羊藿苷易形成加合2个水分子的准分子离子.利用电喷雾碰撞诱导解离方法,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.     

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.     

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。     

Sensitivity of Positive Ion Mode Electrospray Ionization Mass Spectrometry in the Analysis of Thiol Metabolites

High signal intensities of glutathione (GSH), [GSH+H]⁺ (m/z 308), cysteine (CySH), [CySH+H]⁺ (m/z 122), and homocysteine (hCySH), [hCySH+H]⁺ (m/z 136), are observed in ESI MS with on‐line electrochemistry (EC). Dimers formed by H‐bonding, which are not electrochemical products, are detected as [2GSH+H]⁺ (m/z 615), [2CySH+H]⁺ (m/z 243) and [2hCySH+H]⁺ (m/z 271) together with disulfide dimers GSSG, CySSCy and hCySSCyh, [GSSG+H]⁺ (m/z 613), [CySSCy+H]⁺ (m/z 241) and [hCySSCyh+H]⁺ (m/z 269). When dopamine is present a thiol/dopamine quinone (DAQ) adduct is observed. Formation of this adduct is proposed to occur by an electrochemical mechanism during ESI. Catalysis of thiol oxidation and analysis of thiol mixtures is addressed.     

Soft Supercharging of Biomolecular Ions in Electrospray Ionization Mass Spectrometry

The charge states of biomolecular ions in ESI-MS can be significantly increased by the addition of low-vapor supercharging (SC) reagents into the spraying solution. Despite the considerable interest from the community, the mechanistic aspects of SC are not well understood and are hotly debated. Arguments that denaturation accounts for the increased charging observed in proteins sprayed from aqueous solutions containing SC reagent have been published widely, but often with incomplete or ambiguous supporting data. In this work, we explored ESI MS charging and SC behavior of several biopolymers including proteins and DNA oligonucleotides. Analytes were ionized from 100 mM ammonium acetate (NH₄Ac) aqueous buffer in both positive (ESI+) and negative (ESI–) ion modes. SC was induced either with m-NBA or by the elevated temperature of ESI capillary. For all the analytes studied we, found striking differences in the ESI MS response to these two modes of activation. The data suggest that activation with m-NBA results in more extensive analyte charging with lower degree of denaturation. When working solution with m-NBA was analyzed at elevated temperatures, the SC effect from m-NBA was neutralized. Instead, the net SC effect was similar to the SC effect achieved by thermal activation only. Overall, our observations indicate that SC reagents enhance ESI charging of biomolecules via distinctly different mechanism compared with the traditional approaches based on analyte denaturation. Instead, the data support the hypothesis that the SC phenomenon involves a direct interaction between a biopolymer and SC reagent occurring in evaporating ESI droplets.

Electrospray Ionization Tandem Mass Spectrometry of Ammonium Cationized Polyethers

Quaternary ammonium salts (Quats) and amines are known to facilitate the MS analysis of high molar mass polyethers by forming low charge state adduct ions. The formation, stability, and behavior upon collision-induced dissociation (CID) of adduct ions of polyethers with a variety of Quats and amines were studied by electrospray ionization quadrupole time-of-flight, quadrupole ion trap, and linear ion trap tandem mass spectrometry (MS/MS). The linear ion trap instrument was part of an Orbitrap hybrid mass spectrometer that allowed accurate mass MS/MS measurements. The Quats and amines studied were of different degree of substitution, structure, and size. The stability of the adduct ions was related to the structure of the cation, especially the amine’s degree of substitution. CID of singly/doubly charged primary and tertiary ammonium cationized polymers resulted in the neutral loss of the amine followed by fragmentation of the protonated product ions. The latter reveals information about the monomer unit, polymer sequence, and endgroup structure. In addition, the detection of product ions retaining the ammonium ion was observed. The predominant process in the CID of singly charged quaternary ammonium cationized polymers was cation detachment, whereas their doubly charged adduct ions provided the same information as the primary and tertiary ammonium cationized adduct ions. This study shows the potential of specific amines as tools for the structural elucidation of high molar mass polyethers.     

有机盐类化合物醋酸钠的电喷雾质谱研究

利用电喷雾质谱技术研究了有机盐类化合物醋酸钠(NaAc)的特征质谱行为,实验结果表明,在全扫描电喷雾正负离子谱中都出现了质量数相差82的质谱峰簇．这与醋酸钠的相对分子质量相一致,正负质谱峰簇分别对应于簇合物离子Na^ (NaAc)n和Ac^-(NaAc)m:簇合物离子的多级串联质谱进一步证明了簇合物离子的存在。该结果为类似结构的盐类化合物的表征提供了一种新的质谱证据。     

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.     

电喷雾质谱在手性识别和分析中的应用

近年来电喷雾质谱以其快速、灵敏、简便、样品用量少等特点被越来越多地应用于手性分析研究中。本文综述了目前电喷雾质谱法在手性识别和分析中的应用,包括常用的分析方法及常用的质谱手性选择剂,并对其发展进行了展望。     

Quantifying Protein-Fatty Acid Interactions Using Electrospray Ionization Mass Spectrometry

The application of the direct electrospray ionization mass spectrometry (ESI-MS) assay to quantify interactions between bovine β-lactoglobulin (Lg) and a series of fatty acids (FA), CH₃(CH₂)_xCOOH, where x = 6 (caprylic acid, CpA), 8 (capric acid, CA), 10 (lauric acid, LA), 12 (myristic acid, MA), 14 (palmitic acid, PA) and 16 (stearic acid, SA), is described. Control ESI-MS binding measurements performed on the Lg-PA interaction revealed that both the protonated and deprotonated gas phase ions of the (Lg + PA) complex are prone to dissociate in the ion source, which leads to artificially small association constants (K _a ). The addition of imidazole, a stabilizing solution additive, at high concentration (10 mM) increased the relative abundance of (Lg + PA) complex measured by ESI-MS in both positive and negative ion modes. The K _a value measured in negative ion mode and using sampling conditions that minimize in-source dissociation is in good agreement with a value determined using a competitive fluorescence assay. The K _a values measured by ESI-MS for the Lg interactions with MA and SA are also consistent with values expected based on the fluorescence measurements. However, the K _a values measured using optimal sampling conditions in positive ion mode are significantly lower than those measured in negative ion mode for all of the FAs investigated. It is concluded that the protonated gaseous ions of the (Lg + FA) complexes are kinetically less stable than the deprotonated ions. In-source dissociation was significant for the complexes of Lg with the shorter FAs (CpA, CA, and LA) in both modes and, in the case of CpA, no binding could be detected by ESI-MS. The affinities of Lg for CpA, CA, and LA determined using the reference ligand ESI-MS assay, a method for quantifying labile protein–ligand complexes that are prone to in-source dissociation, were found to be in good agreement with reported values.     

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…