Exact Mass FAB and EI/FAB MS with Peptides Using a Direct Insertion FAB Probe

Abstract

We have successfully installed and tested the first direct insertion probe (DIP) fast atom bombardment (FAB) gun on a Kratos MS-80 mass spectrometer. the installation requires only minor modifications on the standard EI/CI source which do not interfere with normal EI or CI operation. A small 2 inch extender must be added to the solid inlet to accomodate the extra length of the probe tip; this can be replaced in a few minutes by the standard seal to accept the regular solid probe. We have operated the source under simultaneous EI/FAB conditions with excellent results. The use of sorbitol syrup helps to keep source contamination and background spectrum to a minimum making it possible to operate at sufficiently high resolution in order to make exact mass operation routine. The performance evaluation has been carried out with synthetic peptides and the results are presented here.     

Comparision of FAB and MALDI Mass Spectrometry of Ginsenosides

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鬼臼及其羧酸酯类化合物2位立体异构体的EI MS质谱研究

鬼臼(podophyllotoxin)及其衍生物在抗癌方面表现出良好的活性。最近,Lopez-perez等人研究了合成的鬼臼羧酸酯类化合物的细胞活性,发现鬼臼的4位降冰片烯酯化合物在对P-388,A-549,HT-29和MEL-28有较母体鬼臼强3~5倍的活性[1],因此引起了人们对鬼臼酯类化合物抗癌活性与结构特点     

硫酸头孢喹肟的质谱研究

头孢喹肟(cefquinome)是头孢菌类抗生素,又名克百特(cobactan),是德国赫司特动物保健品公司开发和研制的动物专用第四代头孢菌素类抗生素.     

新型减肥药利莫纳班的离子阱质谱和电子轰击质谱研究

新型减肥药利莫纳班(rimonabant)是一种选择性CB1受体拮抗剂,服后不易反弹.利莫纳班具有减轻体重和戒除烟瘾的功效,并能降低胆固醇、预防肥胖人群患上心脏病和糖尿病等.     

二甲基焦膦酸二烷基酯的EI-MS裂解规律研究

采用气相色谱-质谱(GC-MS)和气相色谱-串联质谱(GC-MS/MS)研究了二甲基焦膦酸二烷基(≥C2)酯电子轰击质谱(EI-MS)的裂解途径和机理。针对二甲基焦膦酸二烷基(≥C2)酯类化合物,开展了一级和二级质谱研究,确定离子间的母子关系;同时采用电荷和游离基理论,解释主要碎片离子的裂解机理。通过研究发现:对于二甲基焦膦酸二烷基(≥C2)酯类化合物,大部分化合物的EI-MS谱图中无分子离子峰;该类化合物均产生特征离子m/z 175、158、157、143、97、79、65和47;分子离子以不饱和氧、饱和氧和π键为电荷/游离基中心引发酯基上伴随γ氢重排的α断裂和i断裂,碎片离子进一步发生简单α断裂、消除反应(γe)及i诱导断裂等反应,产生相应的离子。根据该类化合物的质谱裂解规律,可为未知结构的该类化合物和其它相似结构化合物的鉴定提供参考。     

串联质谱法鉴定丙基膦酸烷基酯异构体

采用串联质谱(MS/MS)研究了丙基膦酸烷基酯异构体,以鉴定与磷相连的丙基基团。针对电子轰击质谱(EI-MS)谱图中特征离子m/z 125和化学电离质谱(CI-MS)谱图中的准分子离子,进行串联质谱研究,对碰撞气压力和碰撞能量进行优化。实验结果表明:在碰撞能量20 V,碰撞气压力1.0 mTorr时,电子轰击串联质谱(EI-MS/MS)模式下,正丙基膦酸酯的母离子m/z 125碎裂产生较强的子离子m/z 107,而异丙基膦酸酯的母离子m/z 125则碎裂产生较强的子离子m/z 65和83;在化学电离串联质谱(CI-MS/MS)模式下,正丙基膦酸酯的准分子离子产生子离子m/z 125(基峰)和107,异丙基膦酸酯的准分子离子产生子离子m/z 125、107和83;通过串联质谱反应,能清晰地区分正丙基和异丙基膦酸烷基酯(C≥2)。     

Identification and Structural Assessment of Alkaline-Earth Metal Complexes with Flavonols by FAB Mass Spectrometry

Complexation of a series of flavonols with Mg^{2 +}, Ca^{2 +}, and Ba^{2 +} ions was studied by FAB mass spectrometry. The mass spectra of flavonol solutions containing magnesium ions revealed formation of 1 : 2 complexes MgL₂, undetectable by spectrophotometric and spectrofluorimetric methods. Experiments with a crown-substituted flavonol revealed formation of not unly previously known chelate complexes MgL and Mg₂L, but also of the 1 : 2 complex MgL₂ and crown complex MgHL. The barium ions form with the crown-substituted flavonol two types of sandwich complexes: Ba(HL)₂ and Ba₂(HL)₂. With the Ca^{2 +} ions, such complexes are not formed, and only the fragmentation product of the complex Ca(HL)₂ was detected.     

手性化合物在质谱中光学稳定性的研究

反应质谱法自创立以来 ,已广泛应用于有机立体化学的研究领域 .其方法是在质谱离子源中引入反应试剂 ,使之与分析物发生立体选择性反应产生特征离子 ,通过这些特征离子可获得待分析样品的立体化学信息 [1] .我们 [2～ 5 ] 在前期工作中 ,通过在质谱中引入手性反应试剂造成手性环境 ,成功地研究了对映体的绝对构型 .由于质谱过程中常伴随着高温、质子酸催化等因素 ,因而随着反应质谱在对映体构型方面研究的深入进行 ,手性反应试剂及手性样品在质谱过程中是否会发生变旋这一问题日益引起我们的重视 .当对映异构体手性中心连接一个氢原子和一个…     

奶油甘油三酯的毛细管气相色谱-EI质谱分析

以HP_5MS30m×0.25mm×0.25μm毛细管柱分离奶油中各甘油三酯 ,通过各自EI质谱确定其组成 ,共鉴定出108种甘油三酯 ,其中以丁酸双棕榈酸三甘油酯 (8.2% ,峰面积百分比 ,下同 )、癸酸双棕榈酸三甘油酯 (7.9% )、月桂酸双棕榈酸三甘油酯 (7.7% )、肉豆蔻酸双棕榈酸三甘油酯 (6.9% )、丁酸棕榈酸油酸三甘油酯 (6.2% )、丁酸棕榈酸硬脂酸三甘油酯 (5.9% )为主     

Differentiation of Diastereoisomers of Protected 1,2-Diaminoalkylphosphonic Acids by EI Mass Spectrometry and Density Functional Theory

Electron ionization mass spectrometry and density functional theory (DFT) calculations have been used to study the fragmentation of diastereoisomers of protected 1,2-diaminoalkylphosphonic acids. The loss of a diethoxyphosphoryl group and the elimination of diethyl phosphonate were found to be competitive fragmentation processes, which can be used to differentiate both stereoisomers. Selective deuterated analogs and product- and precursor-ion mass spectra allowed the elucidation of the fragmentation mechanisms. The structures of the transition states and product ions were optimized using the density functional theory (DFT), and free energy calculations confirmed the observed differences in the formation and relative intensities of specific fragment ions.

水杨酸与二烷基亚磷酸酯反应历程31P NMR与电喷雾质谱跟踪研究

The reaction between salicylic acid and dialkyl phosphite was traced by electrospray ionization mass spectrometry and ^31P NMR. All reactants, unstable intermediates and products were detected. The mechanism was proposed based on ESI-MS results and ^31P NMR profiles.     

Determination of triazine herbicides with GC/MS under EI, methane CI and ammonia CI conditions detecting positive and negative ions

Summary Mass spectra of 26 triazine herbicides including a few metabolites were measured with a Finnigan 4000 applying electron impact and chemical ionization using methane and ammonia as reactant gases monitoring both positive and negative ions. Chemical ionization was studied to find out possible advantages of ammonia over other reactant gases. Detection limits with SIM were measured with methane and ammonia. For most of the triazines ammonia was found to be superior to methane with respect to detection sensitivity.Part of this paper was presented at the Seventh International Congress of Pesticide Chemistry, Hamburg, August 5–10, 1990     

同位素质谱和无机质谱

本文是《分析试验室》定期评述中“同位素质谱和无机质谱”的第四篇评述，评述的范围是１９９４年１１月至１９９６年１０月我国气体同位素质谱，热电离同位素质谱，加速器质谱，火花源质谱，电感耦合等离子体质谱，辉光放电质谱，同位素稀释质谱，二次离子质谱，激光共振电离子飞行时间质谱，电子探针，质子探针，激光探针和它们在地学，核科学，环境科学，材料学，计理学，医学和生命科学中的应用，引用文献１４９篇。     

Comparative Study of Three Methods for Affinity Measurements: Capillary Electrophoresis Coupled with UV Detection and Mass Spectrometry, and Direct Infusion Mass Spectrometry

We present affinity capillary electrophoresis and mass spectrometry (ACE-MS) as a comprehensive separation technique for label-free solution-based affinity analysis. The application of ACE-MS for measuring affinity constants between eight small molecule drugs [ibuprofen, s-flurbiprofen, diclofenac, phenylbutazone, naproxen, folic acid, resveratrol, and 4,4'-(propane-1,3-diyl) dibenzoic acid] and β-cyclodextrin is described. We couple on-line ACE with MS to combine the separation and kinetic capability of ACE together with the molecular weight and structural elucidation of MS in one system. To understand the full potential of ACE-MS, we compare it with two other methods: Direct infusion mass spectrometry (DIMS) and ACE with UV detection (ACE-UV). After the evaluation, DIMS provides less reliable equilibrium dissociation constants than separation-based ACE-UV and ACE-MS, and cannot be used solely for the study of noncovalent interactions. ACE-MS determines apparent dissociation constants for all reacting small molecules in a mixture, even in cases when drugs overlap with each other during separation. The ability of ACE-MS to interact, separate, and rapidly scan through m/z can facilitate the simultaneous affinity analysis of multiple interacting pairs, potentially leading to the high-throughput screening of drug candidates.     

Studies on the Reaction of Salicylic Acid with Dialkyl Phosphite by Electrospray Ionization Mass Spectrometry and 31p NMR

The Atherton-Todd reaction has been extensively applied to the synthesis of phosphates and phosphoroami dates. [1] Zeng et al. [2] suggested that under Atheron-Todd reaction conditions, dialkyl phosphites are transformed into diakyl phosphorochloridates.     

噻二唑基取代硫脲化合物的低分辨质谱研究

研究了两类１９种取代硫脲类化合物的低分辨ＥＩ质谱。其主要裂解方式为噻二唑环开裂，硫代羰基裂解及中性丢失。杂原子的存在对质谱裂解有重要影响     

N,N''''-二苯亚甲基乙二胺衍生物的EI质谱研究

N,N-二苯亚甲基乙二胺由乙二胺和两分子的苯甲醛缩合得到.反应式为:     

同位素质谱和无机质谱分析

本文与本刊1991年专栏评述衔接,评述了1991～1992年10月间我国同位素质谱和无机质谱分析的情况。包括同位素分析、同位素示踪、同位位素稀释、同位素质谱计研制、火花质谱、二次离子质谱、离子探针、等离子体质谱等。资料来源以国内为主,也收集了少量代表学科先进水平的外国文献。参考文献252篇。