Characterization of Progesterone Derivatives by LC-DAD-ESI/MSn and Its Application to the Identification of Impurities in Flurogestone Acetate

The fragmentation behaviors of progesterone derivatives were studied by high-performance liquid chromatography electrospray ionization tandem mass spectrometry. Under tandem MS conditions, most of the fragments were formed by the cleavage of peripheral groups. Analyses of the fragmentation pathways revealed that the presence of substituents of a progesterone derivative could be deduced from characteristic losses. Characteristic cleavages of 28 and 58 Da were observed from ring cleavages with compounds containing two specific double bonds in the progesterone backbone. In addition, UV spectra were acquired to support MS-based analysis. The presence of nine impurities in crude flurogestone acetate samples were characterized, followed by their tentative assignments based on mass spectral fragmentation patterns.     

Characterizing the electrospray ionization mass spectral fragmentation pattern of indole derivatives synthesized from 2-keto glycosides

Four indole derivatives synthesized from 2-keto glycosides were analyzed by electrospray ionization tandem mass spectrometry (ESI-MSn) with low-energy collision-induced dissociation to establish a general structural elucidation of indole derivatives. Their fragmentation pathways are proposed on the basis of the MSn studies and deuterium-labeled experiments. Indole derivatives undergo complicated gas-phase rearrangements in addition to simple bond cleavages. A rearrangement, which involves a contraction of the six-membered ring, was observed and a mechanism was proposed. The observations may have some potential applications in the interpretation of the mass spectra of indole derivatives.     

Differentiation of diastereomeric chlorin derivatives by fast atom bombardment mass spectrometry

The stereochemistry of six pairs of diastereomeric chlorin derivatives was investigated by electron impact (EI), fast atom bombardment (FAB) and direct chemical ionization DCI mass spectrometry. It was demonstrated that FAB and EI mass spectrometry are convenient and rapid methods for distinguishing between diastereomeric chlorin derivatives due to their different fragmentation patterns.     

Characterization and determination of six aristolochic acids and three aristololactams in medicinal plants and their preparations by high-performance liquid chromatography-photodiode array detection/electrospray ionization mass spectrometry

Aristolochic acid derivatives (AAs) and aristolactam derivatives (ALs) have been characterized by electrospray ionization mass spectrometry, and their fragmentation pathways are proposed. ALs exhibit a single ionization product [M+H]+, whereas AAs show multiple ionization products. By optimizing the chromatographic separation and mass spectrometric parameters, the precursor ions of the derivatives with the best responses were found, and the sensitivities in the determination of the nine derivatives were improved. Based on the investigation of ionization behaviour, a HPLC-DAD/ESI-MS (high-performance liquid chromatography-photodiode array detection/electrospray ionization mass spectrometry) method has been developed for simultaneous analysis of nine derivatives, i.e., AA I, AA II, AA C, AA D, 7-OH AA I, aristolic acid I, AL AII, AL IIIa and AL IVa, in nine medicinal herbs and two preparations. The method appears to be suitable for safety assurance and quality control of commercially available samples with good selectivity and suitable sensitivity.     

富勒烯及其衍生物的质谱研究

本文制备了一系列富勒烯及其衍生物，并利用多种质谱技术进行了鉴定、表征、揭示了它们在离子源条件下的稳定性及解规律。这些富勒烯及其省生物在ＦＤＭＳ、ＩＳＭＳ中均得到了较强的准分子离子峰且碎片峰很少。结果表昨ＦＤＭＳ，ＬＳＩＭＳ技术均适于富勒烯及其衍生物的定性分析，是目前富勒烯分析鉴定中较好的方法。     

Investigation of the tris(trimethoxyphenyl)phosphonium acetyl charged derivatives of peptides by electrospray ionization mass spectrometry and tandem mass spectrometry

Charged derivatives of peptides are useful in obtaining simpler collision-activated dissociation (CAD) mass spectra. An N-terminal charge-derivatizing reagent capable of reacting with picomole levels of peptide has been recently reported (Huang et al. Anal. Chem. 1997, 69, 137-144) in the contexts of analyses by fast atom bombardment (FAB) and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. Electrospray ionization (ESI) mass spectrometric investigation of these tris(trimethoxyphenylphosphonium) acetyl derivatives are described in this article, including studies by in-source fragmentation (ISF) and tandem mass spectrometry (MS/MS). Results from ISF are compared with those from MS/MS. Similarities and differences between ESI-ISF, MALDI-post-source decay (PSD), and FAB-CAD data are presented. Differences in fragmentation of these charged derivatives in the triple quadrupole and ion trap mass spectrometers also are discussed. Application of this derivatizing procedure to tryptic digests and subsequent analysis by liquid chromatography-mass spectrometry is also shown.     

Electron ionization and atmospheric pressure photochemical ionization in gas chromatography-mass spectrometry analysis of amino acids

The mass spectra of tert-butyldimethylsilyl (TBDMS) derivatives of 17 amino acids were obtained using electron ionization (EI) and atmospheric pressure photochemical ionization (APPhCI) mass spectrometry. The APPhCI mass spectra for all of the derivatives except arginine were shown to consist of only molecular [M](+.) and quasimolecular [MH](+) ions whereas, in the case of EI, the compounds in question underwent a drastic fragmentation. The application of APPhCI to gas chromatography-mass spectrometry enables a reliable identification of the TBDMS derivatives of amino acids in a mixture, even if its components are only partially resolved, due to the unique molecular masses for each compound. Comparison of the respective positive-ion chemical ionization (PICI) mass spectra available in the literature with APPhCI spectra has shown that, in the case of PICI, unlike APPhCI, noticeable fragmentation occurs.     

苯并二氮杂(艹卓)类衍生物在质谱中的逆偶极加成反应

在对二氮杂(艹卓)类衍生物--二氢-1,5-二氮杂卓上亚胺双键与腈氧化物环加成产物的电子轰击质谱(EI-MS)研究中,发现这些衍生物均形成了丰度较大的逆1,3-偶极加成(Retro-1,3-Dipolar Addition,RDA)的碎裂反应产物特征离子.     

Understanding the Fragmentation Pathways of Carbocyclic Derivatives of Amino Acids by Using Electrospray Ionization Tandem Mass Spectrometry

Aminoacyl derivatives of aminoadamantanes amantadine and rimantadine have been investigated in regard to their antiviral properties. So far, few studies on the mass spectrometric fragmentation pathway of these compounds have been reported using high-resolution mass spectrometry (HRMS). Two major fragmentation pathways have been observed. For the rimantadine derivatives, losses of rimantadine and N-(1-adamantyl) ethylformamide were described. Similarly, in case of amantadine derivatives, there were losses of amantadine and N-(1-adamantyl) formamide. The loss of the aminoacyl group was common to all of the studied compounds. Understanding the fragmentation mechanism can bring new insight into the characterization of these compounds.     

The investigation of substituent effects on the fragmentation pathways of pentacoordinated phenoxyspirophosphoranes by ESI‐MSn

The fragmentation pathways of pentacoordinated phenoxyspirophosphoranes were investigated in the positive mode by electrospray ionization multistage mass spectrometry. The results demonstrate that the sodium adducts of the title compounds undergo two competitive fragmentation pathways, and the fragmentation patterns are heavily dependent on the various substituent patterns at the phenolic group. An electron‐withdrawing substituent at the ortho‐position always results in the removal of a corresponding phenol analogue, while cleavage by spiroring opening becomes the predominant fragmentation pathway if an electron‐donating substituent is at the phenolic group. The substituent effects on the competitive fragmentation pathways were further elucidated by theoretical calculations, single crystal structure analysis, and high‐resolution mass spectrometry. The results contribute to the understanding of the gas‐phase fragmentation reactions and the structure identification of spirophosphorane analogues by electrospray ionization multistage mass spectrometry.     

Sequencing of sulfonic acid derivatized peptides by electrospray mass spectrometry

We report the application of nanoelectrospray ionization tandem mass spectrometry (nES-MS/MS) and capillary LC/microelectrospray MS/MS (cLC/&mgr;ES-MS/MS) for sequencing sulfonic acid derivatized tryptic peptides. These derivatives were specifically prepared to facilitate low-energy charge-site-initiated fragmentation of C-terminal arginine-containing peptides, and to enhance the selective detection of a single series of y-type fragment ions. Both singly and doubly protonated peptides were analyzed by MS/MS and the results were compared with those from their derivatized counterparts. Model peptides and peptides from tryptic digests of gel-isolated proteins were analyzed. Derivatized singly protonated peptides fragment in the same way by nES-MS/MS as they do by post-source decay matrix-assisted laser desorption/ionization mass spectrometry (PSD-MALDI-MS). They produce fragment ion spectra dominated by y-ions, and the simplified spectra are readily interpreted de novo. Doubly protonated peptides fragment in much the same way as their non-derivatized doubly protonated counterparts. The fragmentation of doubly protonated derivatives is especially useful for sequencing peptides that possess a proline residue near the N-terminus of the molecule. The singly protonated forms of these proline-containing derivatives often show enhanced fragmentation on the N-terminal side of the proline and considerably reduced fragmentation on the C-terminal side. In addition, sulfonic acid derivatization increases the in-source fragmentation of arginine-containing peptides. This could be useful for sequence verification and sequence tagging for use in single stage mass spectrometry. Copyright 2000 John Wiley & Sons, Ltd.     

Identification of phosphorylcholine substituted peptides by their characteristic mass spectrometric fragmentation

Phosphorylcholine (PC) substituted biomolecules are wide-spread, highly relevant antigens of parasites, since this small hapten has been found to be a potent immunomodulatory component which allows the establishment of long lasting infections of the host. Structural data, especially of protein bound PC-substituents, are still rare due to the observation that mass spectrometric analyses are mostly hampered by this zwitterionic substituent resulting in low sensitivities and unusual but characteristic fragmentation patterns. Here we investigated the fragmentation behaviour of synthetic PC-substituted peptides by matrix-assisted laser desorption/ionization mass spectrometry and electrospray ionization ion trap mass spectrometry. We could show that the predominant neutral loss of a trimethylamine unit (Hoffmann elimination) leads to cyclic phosphate derivatives which prevent further fragmentation of the peptide backbone by stabilizing the positive charge at this particular side chain. Knowledge of this PC-specific fragmentation might help to identify PC-substituted biomolecules and facilitate their structural analysis.     

Electron ionization fragmentation mechanisms of different substituted 2,3-dihydro- and 2,3,4,5-tetrahydro-1,5-benzothiazepines

The electron ionization induced fragmentations of ten biologically significant 2,3-dihydro-1,5-benzothiazepines and the corresponding 2,3,4,5-tetrahydro-1,5-benzothiazepines have been studied by low- and high-resolution mass spectrometry. The fragmentations follow a general pattern, the details of which are discussed with respect to the nature and position of the substituent in the aromatic ring. The dihydro- and tetrahydro-1,5-benzothiazepines both undergo fragmentation through four routes (A-D). However, the most significant fragmentation takes place through route A, leading to the elimination of ring A or ring B of the molecule. The difference between the fragmentation patterns of dihydro- and tetrahydro-1,5-benzothiazepines appears mainly in route E where a phenylallylhydroxybenzene cation appears in all tetrahydro-1,5-benzothiazepines but is not observed in the corresponding dihydro derivatives.     

N-二异丙基磷酰化氨基酸-N-4-氨基吡啶衍生物的合成及对河豚毒素(TTX)解毒生物活性的研究

通过母体化合物4-氨基吡啶(4-AP)与N-二异丙基磷酰化氨基酸(DiPP-AA)在Ph3P和C2Cl6体系下的缩合反应,将具有生物活性的氨基吡啶环引入到磷酸化氨基酸结构中,设计、合成了5个N-二异丙基磷酰化氨基酸-N-4-氨基吡啶衍生物A1～A5.所有目标化合物均经IR,1H NMR,13C NMR,31P NMR,MS的表征.初步生物活性测试结果表明:目标化合物对河豚毒素(TTX)中毒的小鼠均有一定的解毒作用,并不同程度地延长了生存时间,而且毒性比母体化合物降低了.     

Multiple-stage mass spectrometry analysis of bisphenol A diglycidyl ether, bisphenol F diglycidyl ether and their derivatives

The fragmentation of bisphenol A diglycidyl ether (BADGE), bisphenol F diglycidyl ether (BFDGE) and their derivatives was studied by electrospray ionization tandem mass spectrometry. Multiple-stage mass spectrometry and accurate mass measurements were combined to establish the fragmentation pathways. BADGEs and BFDGEs tend to form ammonium adducts under electrospray conditions which fragmented easily. The fragmentation of [M+NH(4)](+) for BADGEs started with the cleavage of the phenyl-alkyl bond, which was followed by the α-cleavage of the ether group to generate the characteristic product ions at m/z 135, [C(9)H(11)O](+), and m/z 107, [C(7)H(7)O](+). The fragmentation of the BFDGE isomer mixtures was studied by on-line reversed-phase liquid chromatography coupled to multiple-stage mass spectrometry (LC/MS(n)). Information obtained from product ion spectra for each BFDGE isomer and its comparison with the fragmentation pathway of BADGE allowed each isomer and the chromatographic elution order to be identified.     

Application of the atoms in molecules theory and computational chemistry in mass spectrometry analysis of 1,4-naphthoquinone derivatives

Mass spectrometry analysis of 2-(acylamino)-1,4-naphthoquinone derivatives was carried out using electrospray ionization ion source in combination with tandem mass spectrometry. Protonated molecules were dissociated by application of the collision-induced dissociation (CID), and the protonation sites were suggested on the basis of the HOMO, molecular electrostatic potential map (MEP), proton affinity, and Fukui functions calculated by B3LYP/6-31+G(d,p). The main fragmentation mechanisms undergone by the protonated ions were elucidated on the basis of energy, geometry, and topology analysis of equilibrium geometries. Compounds exhibiting only aliphatic hydrogens at the lateral chain undergo interesting ketene elimination. On the other hand, only the benzoylium ion formation is detected for 2-benzoylamino-1,4-naphthoquinone. The bonds geometric and atoms in molecules parameters give evidence that acidic hydrogen atoms play an important role in the fragmentation pathways.     

Tracing glycoprotein structures: electrospray ionization tandem mass spectrometric analysis of sugar-peptide adducts

Owing to the diversity of carbohydrate structures and their significance for the function of many biopolymers, structural analysis of various carbohydrate-related compounds is of great importance. Electrospray ionization tandem mass spectrometry (ESI-MS/MS) was used to establish the fragmentation behaviour of a range of sugar-peptide adducts as model compounds of widespread glycoprotein structures. The compounds used in this study were chosen to provide correlation of distinct fragment ions with specific structural differences, namely position and type of carbohydrate-peptide bond and structure of the sugar moiety. All compounds show N- and C-terminal sequence ions along with losses of up to three water molecules. Fructose-related Amadori compounds exhibit M + 78 modified N-terminal peptide fragment ions. Fragmentation of glucose-peptide esters is characterized by the sugar ring fragmentation. Additionally, under the ESI-MS conditions applied, the esters studied undergo intramolecular reaction giving cyclic sugar-peptide structures that can be traced by the presence of N-terminal peptide M + 42 adducts. Detailed analysis of cyclic fructose-related compound comprising structural features of both studied groups revealed a rich fragmentation pattern derived from amino acid residues and water molecules losses from [M - 2H(2)O + H](+) ion. Also, some interesting differences were found with respect to the nature of carbohydrate moieties.     

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。     

Structural characterization of trimethylsilyl methyl glycosides derivatives by high-resolution mass spectrometry,linked scans and MIKE experiments

Gas chromatography–mass spectrometry investigations have been carried out for the structural analysis of trimethylsilyl methyl derivatives of keto-deoxy sugars and sialic acids studied under electron ionization. Fragmentation patterns were determined. The three derivatives undergo some common fragmentation pathways. Formation of fragment ions possessing cyclic resonance-stabilized structures was demonstrated. As the sialic acid derivative contained a N-acetyl substituent, some additional fragmentations occurred and were also elucidated. Thus, the mechanism of fragmentation was revealed for these derivatives and new findings concerning some series of fragment ions are presented. Presented at the Annual French National Symposium on Mass Spectrometry, Electrophoresis and Proteomics, 20–23 September 2007 in Pau, France.     

Detection of chlorobenzene derivatives using vacuum ultraviolet ionization time-of-flight mass spectrometry.

Vacuum ultraviolet single-photon ionization time-of-flight mass spectrometry (VUV-SPI-TOFMS) has been applied for the detection of chlorobenzene, o-dichlorobenzene, and o-chlorophenol as surrogates for polychlorinated dibenzo-p-dioxine/furans (PCDD/F). The photoionization mass spectra of these compounds appear to be fragmentation free in the ionization processes by the VUV-SPI at 10.2 eV (121.6 nm). Quantum chemical calculations support no fragmentation in the photoionization of chlorobenzene derivatives at around 10 eV. The absolute photoionization cross-sections of chlorobenzene, o-dichlorobenzene, and o-chlorophenol were estimated at 10.2 eV. The photoionization cross-section is an important parameter in the detection of chlorobenzene derivatives by the single-photon ionization technique. The detection limit for chlorobenzene is on the order of tenth parts-per-billion volume (ppbv) in the present experimental setup.