2,2-二羟甲基丙二酸二乙酯的化学电离质谱分析

化学电离(chem ical ionization,CI)是由Munson和Field[1]于1966年提出的一种质谱电离技术,其原理实际上是分子-离子反应[2,3]。在化学电离条件下,常常可以得到丰度很强的准分子离子峰,没有或很少碎片离子,能准确提供相对分子质量信息,但缺乏结构信息。我们在实验中发现,采用适     

取代螺环戊烷的电子轰击和化学电离正,负离子质谱

本文报道了苯取代螺环戊烷衍生物的电子轰击(EI)正离子和化学电离正、负离子(PNCI)质谱。通过亚稳离子测定,研究了该类化合物的裂解机理。在卤代螺环戊烷的EI质谱中,分子离子峰都很弱,甚至不出现M 离子。其特征离子为[M-X]~ 、[M-2X] 和[M-X-HX]~ 。CI正离子谱有较强的[M H]~ 、[M-2X]~ 和[M-x]~ ,CI负离子谱的特征离子为[M X]~-,它们在多数情况下为基峰离子,另外还出现HX_2~-或X~-离子。     

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。     

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。     

天麻中对羟基苯类化合物的高效液相色谱-质谱研究

天麻中对羟基苯类化合物的(EsI(-))一级质谱图中除分子离子峰[M-1]外，还可见明显的[M-1 20] m[2m-1]峰，由此规律可方便确证未知同类样品的分子离子峰。由二级质谱(ESI/MS/MS)的特征碎片离子93、105和107等，结合紫外光谱及核磁结果确定了3个不纯样品中主要成分的结构，同时初步确定了两个同类杂质的结构。     

二茂钛含氟有机酸衍生物的质谱研究

本文研究了二茂钛含氟长链有机酸衍生物(1～3)和具有环状结构的新型二茂钛全氟有机酸(4～7)的电子轰击质谱(EIMS)和负离子化学电离质谱(NICIMS)。在EI谱中出现弱的或不出现M~+,1～7均以CpTiF_2离子为基峰。高质量区的主要特征碎片离子有[M-·cp]~+、[M-R]~+(1～3)和氟重排离子。在低质量区出现一系列二茂钛及茂钛氟重排离子。 1、4～7的NICI(CH_4)质谱中,4、5出现强的M~-离子峰,1出现[M-1]-离子峰,有两个钛的环状结构化合物6和7出现双电荷M~=离子峰,而不出现M~-。     

一些有机硅立体异构体的氧化亚氮负化学电离质谱研究

本文以氧化亚氮(N_2O)为反应气首次研究了一些有机硅立体异构体的负化学电离(NCI)质谱。反应离子(Reactant ions)和样品分子中硅及活性氢原子作用分别产生加合离子[M+O]~-和准分子离子[M-H]~-,它们的碎裂过程显示一定的立体专一性,为这些立体异构体的辨析提供了判据。     

长链不饱和醇的能量分辨质谱

本文用CH4作反应气的化学电离法（CIMS）在三级串连四极质谱仪上完成了四对十四碳不饱和醇蒸发量构体的能量分辩质谱研究。目标化合物的CIMS极其相似，它们各自的准分子离子[M-I]^ 的碰撞活化分解谱也差别不大，但在0-50eV的能量分辨质谱显示了顺、反异构信息，文中讨论了导致顺、反异构体的能量分辨质谱差异的原因。     

电喷雾飞行时间质谱与大气压化学电离质谱法分析烟叶中茄尼醇的比较

采用反相高效液相色谱(RP-HPLC-UV)和电喷雾飞行时间质谱(ESI-TOF/MS)、大气压化学电离质谱(APCI-MS),分析烟叶中的茄尼醇.使用反相G4色谱柱,以V(甲醇):V(水)=9:1为流动相,茄尼醇和烟草中的其它成分分离良好;茄尼醇在ESI正离子全范围扫描中主要形成[M-H2O H] 和[M NH4] 离子,只有微弱的[M H] 离子,同时会产生一些碎片离子;而在APCI正离子全范围扫描中主要形成[M-H2O H] 离子,检测不到[M H] 离子,碎片离子也很少;通过对茄尼醇的ESI-TOF/MS和APCI-MS的质谱分析特征比较可以发现,茄尼醇在ESI源分析中的信号强度远远小于在APCI源分析中的信号强度,说明APCI源更适于茄尼醇的定量分析.     

四氢咪唑取代亚甲基β—二酮质谱碎裂机理的理论研究

理论计算非常适用于气相离子化学研究[1，2]，它与质谱实验相结合可以识别许多非常规的和以往所不知道的自由基离子，也可以提供反应能和机理方面的信息，有助于探讨可能的异构化过程和不同异构体结构的相对稳定性．离子／中性复合物（离子和中性碎片通过静电引力结合在一起）[3]作为有机离子质谱单分子碎裂的重要中间体已被越来越多的理论和实验结果所证实[3，4]．串联质谱低能碰撞诱导解离和同位素标记技术的实验结果表明[5]：四氢咪唑取代亚甲基β-二酮分子结构中氮原子上氢表现出不同活性，其气相单分子碎裂经历了离子／中性复合物的中…     

The Measurement of Leucine Enkephalinat the Femtomole Level by Fast Atom Bombardment Mass Spectrometry/Mass Spectrometry Methods

Abstract

FAB-MS/MS methods are used to quantify the neuropeptide leucine enkephalin (LE = YGGFL) in synthetic solutions. Maximum molecular specificity is provided by monitoring two metastable transitions from the LE (M + H)⁺, 556 → 425 and 556 → 336, in a forward geometry (E, B) mass spectrometer using a B/E linked-field selected reaction monitoring technique. Obtained sensitivity is 40 pg LE, which equals 72 fmol. The statistics of the best-fit straight lines are, for m/z 425: y = 34 + 166 (r = 0.999), and for m/z 336: y = 2.5x + 17.2 (r = 0.996).     

Structural characterization of glycoporphyrins by electrospray tandem mass spectrometry

Porphyrin derivatives having a galactose or a bis(isopropylidene)galactose structural unit, linked by ester or ether bonds, were characterized by electrospray tandem mass spectrometry (ES-MS/MS). The electrospray mass spectra of these glycoporphyrins show the corresponding [M + H](+) ions. For the glycoporphyrins with pyridyl substituents and those having a tetrafluorophenyl spacer, the doubly charged ions [M + 2H](2+) were also observed in ES-MS with high relative abundance. The fragmentation of both [M + H](+) and [M + 2H](2+) ions exhibited common fragmentation pathways for porphyrins with the same sugar residue, independently of the porphyrin structural unit and type of linkage. ES-MS/MS of the [M + H](+) ions of the galactose-substituted porphyrins gave the fragment ions [M + H - C(2)H(4)O(2)](+), [M + H - C(3)H(6)O(3)](+), [M + H - C(4)H(8)O(4)](+) and [M + H - galactose residue](+). The fragmentation of the [M + 2H](2+) ions of the porphyrins with galactose shows the common doubly charged fragment ions [porphyrin + H](2+), [M + 2H - C(2)H(4)O(2)](2+), [M + 2H - C(4)H(8)O(4)](2+), [M + 2H - galactose residue](2+) and the singly charged fragment ions [M + H - C(3)H(6)O(3)](+) and [M + H - galactose residue](+). The fragmentation of the [M + H](+) ions of glycoporphyrins with a protected galactosyl residue leads mainly to the ions [M + H - CO(CH(3))(2)](+), [M + H - 2CO(CH(3))(2)](+), [M + H - 2CO(CH(3))(2) - CO](+), [M + H - C(10)H(16)O(4)](+) and [M + H - protected galactose](+). The doubly charged ions [M + 2H](2+) fragment to give the doubly charged ions [porphyrin + H](2+) and the singly charged ions [M + H - protected galactose residue](+) and [M + H - CO(CH(3))(2)](+). For the porphyrins where the sugar structural unit is linked by an ester bond, [M + 2H](2+), ES-MS/MS showed a major and typical fragmentation corresponding to combined loss of a sugar structural unit and further loss of water, leading to the ion [M + 2H - sugar residue - H(2)O](2+), independently of the structure of the sugar structural unit. These results show that ES-MS/MS can be a powerful tool for the characterization of the sugar structural unit of glycoporphyrins, without the need for chemical hydrolysis.     

Accurate mass measurement and tandem mass spectrometry of intact globin chains identify the low proportion variant hemoglobin Lepore-Boston-Washington from the blood of a heterozygote

Within a mixture of proteins, minor polymorphic components are difficult to identify using a conventional proteomic approach. Their identification generally requires multi-dimensional separation steps, before or after proteolytic cleavage, followed by sequence analysis of the proteolytic products. In this study, we investigated the potential of tandem mass spectrometry for protein characterization by identifying the delta-beta hybrid human hemoglobin variant Lepore-Boston-Washington using electrospray ionization tandem mass spectrometry. Hemoglobin Lepore-Boston-Washington occurs mainly in heterozygotes, where it comprises approximately 10% of the total non-alpha-chains, the dominant non-alpha-chain being the normal beta (approximately 90%). Furthermore, Hemoglobin Lepore-Boston-Washington has an average molecular mass (15,865.23 Da) that is only 2 Da lower than that of the normal beta-chain (15,867.24 Da). Consequently, it cannot be resolved from the normal beta-chain by mass spectrometry. Here we show how Hemoglobin Lepore-Boston-Washington was identified directly from the diluted blood of a heterozygote by analyzing the product ions from the Lepore-Boston-Washington and normal beta-chain ions without prior separation of the individual chains. This study shows the potential of the tandem mass spectrometry for identifying a minor component in an unseparated mixture of proteins.     

傅里叶变换离子回旋共振质谱测定复杂表面活性剂组分

利用傅里叶变换离子回旋共振质谱(FT-ICR-MS)，分析了两类复杂的离子型表面活性剂样品。实验结果表明：高分辨FT-ICR-MS，可以简单、快速、准确地获得两类化合物的结构信息，利用其高准确度的质量测定数据，计算出复杂样品中各组分的元素组成，鉴定出具体化合物，显示了FT-ICR-MS在分子结构分析和未知物鉴定中的强大能力。     

Characterization of dinitroporphyrin zinc complexes by electrospray ionization tandem mass spectrometry. Unusual fragmentations of beta-(1,3-dinitroalkyl) porphyrins

The zinc complexes of diaryl bis(p-nitrophenyl)porphyrins and beta-(1,3-dinitroalkyl)tetraphenylporphyrins were studied by electrospray ionization (ESI) tandem mass spectrometry (MS/MS). All porphyrins showed the protonated molecule under ESI conditions. The protonated molecules were induced to fragment and the corresponding ESI tandem mass spectra were analysed. Porphyrins with two p-nitrophenyl groups showed, as expected, characteristic fragmentations including either loss of one nitro group, as the major fragment of the tandem mass spectra, and loss of both nitro groups. In contrast, MS/MS of the beta-(1,3-dinitroalkyl)porphyrins provided interesting and unexpected results such as the absence (or in insignificant abundance) of the ions formed by loss of one nitro group. However, these porphyrins show an abundant fragment due to combined loss of the two nitro groups. Also, the typical beta-cleavage of the alkyl chain is not observed per se, only when combined with loss of HNO2 or *NO2. Instead, alpha-cleavage, with loss of the beta-pyrrolic substituent, is the most favourable process.     

数字化矩形离子阱质谱仪的设计及性能

将数字化离子阱技术和矩形离子阱(RIT)技术相结合,建立了数字化矩形离子阱质谱仪.此技术和装置既具有数字化电源的结构简单、输出稳定和易精确控制等特点,又结合了矩形离子阱的高离子存储效率、结构简单以及加工和装配容易等优点.构建了基于电喷雾(ESI)电离源的数字化矩形离子阱质谱仪系统,并使用Fenfluramine和PPG2000分别对此系统的质量分辨率和质量范围进行了测试.研究结果表明:一个用印刷线路板(PCB)制作的简单矩形离子阱,在200 V(半峰值)的数字束缚电压的驱动下,获得了大于500的质量分辨率和超过2600 Th的质量范围.实验证明,数字化离子阱技术的应用可以显著提高矩形离子阱的性能,特别是质量范围等关键的质谱仪指标.     

Application of fractional mass for the identification of peptide-oligonucleotide cross-links by mass spectrometry

A method has been developed to identify oligonucleotide-peptide heteroconjugates by accurate mass measurements using MS. The fractional mass (the decimal fraction mass value following the monoisotopic nominal mass) for peptides and oligonucleotides is different due to their differing molecular compositions. This property has been used to develop the general conditions necessary to differentiate peptides and oligonucleotides from oligonucleotide-peptide heteroconjugates. Peptides and oligonucleotides generated by the theoretical digestion of various proteins and nucleic acids were plotted as nominal mass versus fractional mass. Such plots reveal that three nucleotides cross-linked to a peptide produce enough change in the fractional mass to be recognized from non-cross-linked peptides at the same nominal mass. Experimentally, a Cytochrome c digest was spiked with an oligonucleotide-peptide heteroconjugate and conditions for analyzing the sample using liquid chromatography (LC)-MS were optimized. Upon analysis of this mixture, all detected masses were plotted on a fractional mass plot and the heteroconjugate could be readily distinguished from non-cross-linked peptides. The method developed here can be incorporated into a general proteomics-like scheme for identifying protein-nucleic acid cross-links, and this method is equally applicable to characterizing cross-links generated from protein-DNA and protein-RNA complexes.     

液相色谱/质谱/质谱联用法测定润滑油中磷酸三苯酯含量

探讨了用ＬＣ／ＭＳ／ＭＳ联用仪测定液压油中的微量添加剂磷酸三苯酯的方法。应用ＭＲＭ方式记录了ＨＰＬＣ的流出峰,结果表明被分析样品浓度在１～７ｍｇ／Ｌ范围内,色谱峰面积与浓度有良好的线性关系。讨论了ＬＣ／ＭＳ／ＭＳ技术实验条件的选择方法。