芦丁的电喷雾离子阱质谱分析

研究了芦丁在电喷雾离子阱质谱(ESI-MS)下的主要特征碎片离子及其裂解规律。应用电喷雾离子阱质谱技术研究芦丁的结构和正、负离子扫描条件下芦丁的主要特征碎片离子及其裂解规律。芦丁在正、负离子模式下均可得到较好的质谱信息,在正离子模式下,容易与Na+形成[M+Na]+的准分子离子,并裂解形成碎片m/z 605,487,331,325,313,185等,在负离子模式下,形成[M-H]-的准分子离子,并进一步碎裂形成碎片m/z 301,283,257,255,229,227,211等。分别阐明了芦丁在正、负离子模式下的电喷雾质谱碎裂规律,并对主要特征碎片离子进行归属,为进一步芦丁的结构优化和修饰提供了有价值的依据。     

丹参酮ⅡA和丹参酮Ⅰ的电子轰击与电喷雾电离质谱分析

采用电喷雾电离质谱(ESI-MS)和电子轰击质谱(EI-MS)两种质谱技术分别对传统中药丹参的主要脂溶性活性成分丹参酮ⅡA和丹参酮Ⅰ的化学结构和裂解途径进行系统研究。采用EI-MS从丹参酮ⅡA获得m/z 294[M] 、279、261、233、207等特征质谱峰,从丹参酮Ⅰ获得m/z 276[M] 、248、233、219、205等特征质谱峰;采用ESI-MS从丹参酮ⅡA获得m/z 295[M H] 、280、278、262、249等特征质谱峰,从丹参酮Ⅰ获得m/z 277[M H] 、259、249、231、221、193等特征质谱峰,并用Mass Frontier 3.0软件辅助解析了其中的主要特征碎片离子以及可能的裂解途径;比较了丹参酮ⅡA和丹参酮Ⅰ的电喷雾电离质谱和电子轰击质谱裂解规律,本研究为研究丹参二萜醌类主要特征活性成分的生物转化与结构修饰提供了依据。     

紫草素及去氧紫草素的ESI离子阱质谱裂解分析

应用电喷雾离子阱多级质谱技术对紫草素及其活性衍生物去氧紫草素的结构和质谱裂解规律进行比较研究,并在负离子模式下解析了紫草素的主要特征碎片离子及其裂解规律。紫草素负离子模式下的主要碎片为m/z 287,269,259,218,190及173;其中,碎片m/z 218是其特征峰,碎片m/z 269和m/z 259均可进一步裂解为m/z 241,碎片m/z 190为m/z 259和m/z 218的共同产物离子;此外,碎片m/z 190和m/z 173均可进一步裂解为m/z 162。去氧紫草素负离子模式下主要裂解为碎片m/z 271、253、228和203;其中,碎片m/z253是其特征峰。紫草素和去氧紫草素均能发生过渡态氢重排β-裂解和连续的CO中性丢失。     

一种聚酰胺-胺型树枝状分子的电喷雾离子阱质谱分析

以己二胺为分子内核,室内合成了一类支化代数为1.0G的聚酰胺-胺型树枝状分子己二胺四丙酰胺二胺(1.0G支化物)。应用ESI-MS技术研究并表征了该支化物的分子结构与正、负离子扫描条件下的主要特征碎片离子及主要裂解途径。1.0G支化物在正、负离子模式下均可以得到较佳的质谱信息。在正离子模式下,容易与H+形成[M+H]+准分子离子,并裂解形成碎片m/z573.41,m/z 555.40,m/z 471.30,m/z 459.30,m/z 453.28,m/z 369.17,m/z357.16等。在负离子模式下丢失一个H+,形成[M-H]-准分子离子,并进一步碎裂成碎片m/z 571.43,m/z 511.29,m/z 457.20,m/z 397.05,m/z 342.99,m/z240.84等。分别阐述了1.0G支化物在正、负离子模式下的电喷雾质谱裂解规律并对主要特征碎片离子进行了结构归属,为进一步对聚酰胺-胺型树枝状分子的表征与结构指认提供了有价值的依据。     

基于超高效液相色谱-四极杆/静电场轨道离子阱高分辨质谱法非靶向筛查典型三嗪类除草剂

采用超高效液相色谱-四极杆/静电场轨道阱高分辨质谱（UPLC-Q-Orbitrap）研究典型三嗪类除草剂的特征质谱裂解规律。14种三嗪类除草剂的标准溶液经Acquity BEH C18色谱柱（100 mm×3.0 mm,1.7μm）分离,用甲醇和0.1%甲酸水溶液进行梯度洗脱,在电喷雾正离子模式下采集离子信息。通过分析主要特征离子碎片发现：含O、含Cl和含S 3类亚型三嗪类除草剂质谱断裂方式包括：均三嗪环上氨基取代基的碳氮键断裂、均三嗪环上杂原子取代基自由基的丢失和均三嗪环的开环反应。含O三嗪类除草剂的主要特征离子碎片为m/z 142.07234和m/z 100.05060,含Cl三嗪类除草剂的主要特征离子碎片为m/z104.00017,含S三嗪类除草剂的主要特征离子碎片为m/z 116.02769。本研究中得到的三嗪类除草剂的裂解规律可作为非靶向筛查具有相似结构特征的三嗪类化合物的重要依据。     

三唑仑苯二氮(艹卓)类药物的电喷雾质谱裂解特征

采用电喷雾/四极杆飞行时间质谱(ESI-QqTOF)联用技术,对3种三唑仑苯二氮(艹卓)类药物进行CID研究,并以质子化准分子离子[M+H]+作为内标物,对碎片离子进行了准确质量测定,确认了这些碎片离子的元素组成,探讨了该类化合物的质谱裂解规律.研究发现,它们的ESI-MS2(源内)和ESI-MS3质谱分别生成脱去N2分子、HCN或CH3CN分子和Cl原子的碎片离子,其中m/z 205为3种药物共有的碎片离子,这些特征可用于三唑仑苯二氮(艹卓)类药物的体内代谢转化和定量研究.     

N-环己基吡嗪酮类化合物的EI质谱及其解析

总结和归属了 (2H)_2_环己基_3 ,4二氢吡咯并[1 ,2_a]吡嗪_1_酮及其7个苯甲酰基衍生物和3个苯乙酰基衍生物在电子轰击电离质谱 (EI_MS)中的主要裂解方式和特征 ,指明了主要碎片离子的来源和结构 ,这10个芳酰基衍生物质谱图中的主要碎片峰均来自麦氏重排和异构化后的α_裂解,由其裂解产生的m/z120和m/z163离子是该类化合物共同的特征离子 ;吡嗪酮苯甲酰基衍生物基峰为M -82 ,苯乙酰基类衍生物基峰为m/z245。     

乙二胺钴氧合反应的电喷雾串联质谱研究

采用电喷雾多级串联质谱技术对氧载体模型化合物乙二胺钴氧合产物的的质谱裂解规律进行了探讨。以固相法合成的乙二胺钴吸氧初和吸氧6 d两个阶段为研究体系,在正离子电喷雾质谱条件下能够清楚地观测到乙二胺钴氧合配合物的特征碎片离子。对其中m/z 150.86的碎片峰进行子离子扫描,可得到失去中性氧分子(M=32)的子离子碎片峰(m/z 118.85),从而可进一步确认其为氧合配合物碎片峰。本文采用电喷雾多级串联质谱技术对吸氧初和吸氧饱和后的两个体系进行了合理的初步探讨,根据所得质谱数据对乙二胺钴氧合产物的结构、裂解规律及氧气的存在形态给出初步合理的推论,结果表明,吸氧过程是一个老化的过程,乙二胺钴配合物从吸氧初到吸氧饱和后,其形态经历了从双核过氧桥联配合物到双核过氧羟基双桥联配合物形态的转变。初步确立电喷雾质谱(ESI-MS)可做为研究氧合反应和表征氧合配合物的有效技术手段。     

大黄酸ESI-IT MS质谱行为及碎片离子的量子化学研究

采用电喷雾-离子阱质谱(ESI-IT MS),获取大黄酸分子的一级质谱和多级质谱碰撞诱导解离下的碎片离子,以量子化学计算大黄酸分子及其主要碎片离子的质谱行为。通过对质谱离子几何参数、键断裂能、电荷变化、自旋密度以及前线分子轨道的分析,可得到m/z 282.8、256.9、238.9、210.8、192.8、182.8、166.8离子的稳定构型以及质谱裂解途径,从而较系统地解释了大黄酸分子在ESI-IT MS中的裂解行为。     

超高效液相色谱-串联质谱法鉴别十字花科植物中硫代葡萄糖苷

建立超高效液相色谱–串联质谱法鉴别十字花科植物中硫代葡萄糖苷的分析方法。采用70%甲醇水溶液提取白芥种子中的硫代葡萄糖苷,通过反相C18柱分离,电喷雾–离子阱–飞行时间质谱测定。利用硫代葡萄糖苷二级质谱裂解产生的m/z 195,241,259,275,291特征离子和伴随产生的80,162,163,196,242 Da中性分子丢失规律,共鉴别出5种硫代葡萄糖苷。     

电喷雾质谱法分析假单胞菌的代谢产物鼠李糖脂

采用电喷雾质谱(ESI-MS)结合碰撞诱导解离(CA)技术,分析了假单胞菌BS-03,利用甘油产的鼠李糖脂提取物。根据一级和二级质谱图确定了提取物中存在23种鼠李糖脂组分,主要由4种物质(RhC10、RhC10C10、Rh2C10和Rh2C10C10)构成,其中前3种的丰度较高也较平均。该提取物中单鼠李糖脂的含量高于双鼠李糖脂,并且双鼠李糖脂的二级质谱图中普遍存在强度较高的m/z为205、247的特征碎片离子,而单鼠李糖脂中却不存在此特征碎片离子。     

Determination of Matrine and Oxymatrine in Sophora Flavescens by Nonaqueous Capillary Electrophoresis-Electrospray Ionization-Ion Trap-Mass Spectrometry

A simple, rapid, and sensitive nonaqueous capillary electrophoresis-electrospray ionization-ion trap-mass spectrometry (NACE-ESI-IT-MS) method was developed for determination of matrine and oxymatrine in Sophora Flavescens and medicinal preparations. The conditions for NACE separation and MS detection were systematically optimized. The optimum NACE buffer contained 30 mM ammonium acetate, 1% acetic acid, and 15% acetonitrile in methanol and the applied voltage on separation capillary was set at 25 kV. Berberine was selected as internal standard. In order to generate a stable electrospray, a sheath liquid (isopropanol/H₂O, 2/1, v/v) was used, which could also boost the flow through the ESI needle. The matrine and oxymatrine solutions were introduced into MS detection by a syringe pump for collecting the MSⁿ spectra to investigate the main fragment ions and its possible cleavage pathways. Both matrine and oxymatrine showed good linearity in the concentration ranges from 0.5 to 400 µg/mL, with linear correlation coefficient R > 0.99 and the limit of detections were 37.5 ng/mL for matrine and 50.0 ng/mL for oxymatrine, respectively. The recoveries at different content of Sophora Flavescens were 98.3%–102.9% for MT and 95.3%–100.6% for OMT, which indicates the reliability of this method.     

Determination of glycoalkaloids and relative aglycones by nonaqueous capillary electrophoresis coupled with electrospray ionization-ion trap mass spectrometry

Glycoalkaloids are naturally occurring nitrogen-containing compounds present in many species of the family Solanaceae, including cultivated and wild potatoes (Solanum spp.), tomatoes (Lycopersicon spp.), etc. These compounds have pharmacological and toxicological effects on humans due to their significant anticholinesterase activity and disruption of cell membranes. Herein is reported the development of a capillary electrophoresis (CE) method using nonaqueous (NA) separation solutions in combination with ion trap mass spectrometry (MS and MS/MS) detection for the identification and quantification of glycoalkaloids and their relative aglycones. A mixture 90:10 v/v of MeCN-MeOH containing 50 mM ammonium acetate and 1.2 M acetic acid (applied voltage of 25.5 kV) was selected as a good compromise for the separation and detection of these compounds. The electrospray MS measurements were carried out in the positive ionization mode using a coaxial sheath liquid, methanol-water (1:1) with 1% of acetic acid at a flow rate of 2.5 microL/min. Under optimized experimental conditions, the predominant ion was the protonated molecular ion ([M+H](+)) of solanidine (m/z = 398), tomatidine (m/z = 416), chaconine (m/z = 852), solanine (m/z = 868), and tomatine (m/z = 1034). MS/MS experiments were carried out systematically by changing the relative collisional energy and monitoring the intensities of the fragment ions that were not high enough to allow better quantification than with the mother ions. The method was used for analyzing glycoalkaloids in potato extracts.     

Low-energy collisionally activated decomposition and structural characterization of cyclic heptapeptide microcystins by electrospray ionization mass spectrometry

Characteristics of electrospray ionization mass spectrometry/collision-induced dissociation (ESIMS/CID) mass spectra of microcystins, cyanobacterial cyclic heptapeptide hepatoxins, were examined. The collision conditions showed remarkable effects on the quality of the CID mass spectra, which were divided into three patterns according to the number of Arg residues. A characteristic cleavage reaction and neutral losses of MeOH, NH3 and guanidine group(s) from the (2S,3S,8S,9S)-3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4 E,6E-dienoic acid (Adda) and Arg residues were observed in the ESI and ESIMS/CID mass spectra, suggesting the most probable protonation sites in [M + H]+ and [M + 2H]2+ ions of microcystins. Microcystins with no Arg residue showed only [M + H]+ ions with a proton reacting at the methoxyl group in the Adda residue, and the ESIMS/CID/MS data revealed their structures unambiguously. The protonation site in [M + H]+ ions of microcystins with Arg residue(s) was the guanidine group. The [M + 2H]2+ ions of microcystins possessing one Arg residue had one proton on the Arg residue and probably another proton on the Adda residue, while the [M + 2H]2+ ions of microcystins having two Arg residues showed protonation at both Arg residues and the ESIMS/CID/MS data assigned their sequences. Structures of microcystins possessing one Arg residue can be assigned by ESIMS/CID/MS of [M + H]+ ions combined with those of [M + 2H]2+ ions.     

The identification of in vitro metabolites of CKD-732 by liquid chromatography/tandem mass spectrometry

The structural elucidation of fourteen metabolites of CKD-732, formed in vitro with rat liver microsomes, was performed using high-performance liquid chromatography/electrospray ionization-tandem mass spectrometry (HPLC/ESI-MS/MS). To identify proposed structures of the metabolites, the product ion mass spectra of the protonated molecules ([M + H]+), the retention times on reversed-phase HPLC, and UV-Vis spectra were utilized. Characteristic product ions for the identification of CKD-732 metabolites were observed at m/z 231, 236, and 252. The fragment ions at m/z 236 and 252 indicated the unchanged form and the N-oxide of the dimethylaminoethoxycinnamoyl group, respectively. The ion at m/z 231 indicated the presence of the hydroxylated form of the fumagillol group. The N-oxide of CKD-732, which was detected at m/z 515 and eluted later than CKD-732 in the reversed-phase HPLC system, was measured as a major metabolite. Three cis-trans isomers were also found.     

北豆根生物碱电喷雾质谱电离规律及其特征图谱研究

用电喷雾离子阱质谱(ESI-QITMS)研究了粉防已碱和青藤碱在正离子检测方式下的一级质谱和二级质谱,总结出各自的ESI碎裂规律。依据北豆根对照药材生物碱提取物各组分的二级质谱碎裂特征进行了提取物的初步结构分析。实验发现北豆根提取物中存在曾在北豆根叶中发现的阿克吐明、阿克吐米定、阿克吐明宁3种含氯生物碱。以北豆根中16种已知主要生物碱(其中有一种存在同分异构体)为对象,应用选择离子检测(SIM)模式制作了北豆根对照药材生物碱提取物的特征指纹图谱。     

Induction and identification of disulfide-intact and disulfide-reduced β-subunit of Shiga toxin 2 from Escherichia coli O157:H7 using MALDI-TOF-TOF-MS/MS and top-down proteomics

The disulfide-intact and disulfide-reduced β-subunit of Shiga toxin 2 (β-Stx2) from Escherichia coli O157:H7 (strain EDL933) has been identified by matrix-assisted laser desorption/ionization time-of-flight-time-of-flight tandem mass spectrometry (MALDI-TOF-TOF-MS/MS) and top-down proteomic analysis using software developed in-house. E. coli O157:H7 was induced to express Stx2 by culturing on solid agar media supplemented with 10-50 ng mL(-1) of ciprofloxacin (CP). Bacterial cell lysates at each CP concentration were analyzed by MALDI-TOF-MS. A prominent ion at mass-to-charge (m/z) ~7820 was observed for the CP concentration range: 10-50 ng mL(-1), reaching a maximum signal intensity at 20 ng mL(-1). Complex MS/MS data were obtained of the ion at m/z ~7820 by post-source decay resulting in top-down proteomic identification as the mature, signal peptide-removed, disulfide-intact β-Stx2. Eight fragment ion triplets (each spaced Δm/z ~33 apart) were also observed resulting from backbone cleavage between the two cysteine residues (that form the intra-molecular disulfide bond) and symmetric and asymmetric cleavage of the disulfide bond. The middle fragment ion of each triplet, from symmetric disulfide bond cleavage, was matched to an in silico fragment ion formed from cleavage of the backbone at a site adjacent to an aspartic acid or glutamic acid residue. The flanking fragment ions of each triplet, from asymmetric disulfide bond cleavage, were not matched because their corresponding in silico fragment ions are not represented in the database. Easier to interpret MS/MS data were obtained for the disulfide-reduced β-Stx2 which resulted in an improved top-down identification.     

Isotope edited product ion assignment by α-N labeling of peptides with [2H3(50%)]2,4-Dinitrofluorobenzene

An isotopic modification of Sanger's method for identifying peptide N-termini has been developed to assist peptide sequencing by tandem mass spectrometry. Tryptic peptides, such as Val-His-Leu-Thr-Pro-Val-Glu-Lys, are derivatized with an equimolar mixture of 2,4-dinitrofluorobenzene and [2H3]2,4-dinitrofluorobenzene. Under optimized derivatization conditions, the alpha-amino group could be derivatized while the epsilon-amine of the lysine side chain and the imidazole of histidine remained underivatized. The alpha-dinitrophenyl modified peptides were characterized by electrospray ionization-tandem mass spectrometry (ESI-MS/MS) and liquid chromatography (LC)-ESI-MS. The [M + H]+ ions showed a doublet pattern with a delta m/z of 3 and the [M + 2H]2+ ions were recognized as doublets with a delta m/z of 1.5. MS/MS was employed where both isotopic [M + 2H]2+ ions were alternately subjected to collision-induced dissociation in the second quadrupole. Fragmentation in the ionization source generated identical product ion patterns that were observed during fragmentation in the second quadrupole. In the product ion mass spectra, the N-terminal a and b ions (no c ion observed) are doublets with a delta m/z of 3 or 1.5, while the C-terminal y and z ions (no x ion observed) are singlets appearing at identical masses. Thus, the product ions containing the N-terminus derivatized with a dinitrophenyl group are unequivocally distinguished from the product ions containing the C-terminus. The dinitrophenyl modification generally enhanced the production of a and b ions without diminishing y and z ion yields.