色谱-质谱分析在有机地球化学研究中的应用

色谱-质谱分析在有机地球化学领域主要用来检测地质体中的生物标志物和分子化合物。生物标志物(biomarkers)指存在地壳和大气圈中,分子结构与特定天然产物之间具有明确联系,或与特定生物类别的分子结构之间具有相关性的天然有机化合物。从1982年到1992年10年的时间共召开了五届全国有机地球化学会议,每次会议都有生物标志物专题,在五届的全国有机地球化学会议中共有论文摘要1491篇,和生物标志物有关的论文达     

超临界CO2在泥岩生物标志物分析中的应用与索氏抽提技术的实验对比

应用超临界萃取/气相色谱-质谱技术测定泥岩中的正构烷烃、藿烷,其有机地化参数与经典索氏抽提基本相符.该方法样品用量少,且高效、快速、无污染和危险,适用于有机地球化学研究中稀少地质样品生物标志化合物及一些分子标志物的分析检测工作.     

谱图检索结合二级质谱定性分析烟草中挥发性成分

采用同时蒸馏萃取法提取烟叶中的挥发性成分,利用气相色谱-质谱联用仪(GC-MS)分离测定,通过谱库检索和匹配度定性结合色谱保留指数方法鉴定烟叶中挥发性成分,并引入离子阱二级质谱对谱库检索匹配度差距小、含量低,背景干扰大的物质准确定性.采用谱图检索结合二级质谱定性共鉴定144个化合物,其中104个化合物在烟草挥发性成分的文献中已有报道,报道中有9个化合物是通过二级质谱定性,其余40个化合物还未见报道.结果表明,离子阱二级质谱定性的引入提高了对未知化合物定性的准确性和可靠性,适合于烟叶这类复杂植物体系的化学组分研究.     

石油和生油岩中萜烷、甾烷、芳代甾烷的GC-MS分析

在有机地球化学研究中,生物标志化合物由于有明显的生物继承性、热作用敏感性、结构的稳定性,所以占有重要地位。本文仅就松辽盆地原油或生油岩中萜烷、甾烷和芳化甾烷的GC—MS分析方法和鉴定作一论述。     

超高效液相色谱-串联质谱法鉴定猪肉的特异性肽生物标志物

以亲缘关系较近的猪、牛和羊3个物种的肌肉组织为研究对象,采用超高效液相色谱-串联质谱(UPLC-MS),筛选并确认了猪物种肉特异性肽生物标志物.3种纯肉样品经蛋白质提取、胰蛋白酶消化和UPLC-TripleTOF-MS分离鉴定,得到的总离子流图谱(TIC)与Uniprot蛋白质数据库对比分析,筛选出3个物种肉的3种高丰度同源蛋白和8种潜在的肽生物标志物;潜在的肽生物标志物经QTRAP-MS质谱的多反应模式(MRM)分析,最终确认了猪物种肉的5种肽生物标志物,其中3种肽生物标志物未见文献报道.     

气相色谱-质谱/质谱检测原油中 27、24、21-降胆甾烷

随着地质勘探研究工作的深入和发展,一些常规检测的生物标记化合物,已无法满足特殊区域地质研究的需要,地球化学家把注意力放在一些含量极微,但具有明确断代标志意义或明确生源的标志物身上,而这些组分靠常规的GC-MS分析根本检测不到。而GC-MS/MS由于是二级质谱串联比GC-MS增加     

一种有机质谱谱图的库检索新算法

一种有机质谱谱图的库检索新算法律祥俊，林少凡，张金碚，张法义（南开大学中心实验室，天津，３０００７１）关键词检索，算法，质谱，数据库利用计算机匹配技术识别有机质谱谱图中的库检索方法仅需用低分辨质谱图即可识别未知化合物，似为最成功的方法［１～３］．质谱...     

生物标志化合物的合成研究：Ⅲ.5α—胆甾烷和5β—胆甾烷的合成

地质体内古生物遗体的某些成分,经长期的物理化学变化逐渐演变成某些稳定的、特征性的化合物,地球化学上称为生物标志物(biological markers或biomarkers),生物标志化合物与它们的生物前身物的对比可用于研究沉积环境、古生态特征,特别可为石油的成因、迁移,油源对比,地质模拟实验等提供重要依据。类异戊二烯烃、萜类、甾烷等都是石油、煤和近代沉积物中已知的生物标志物.前文报道了4α-甲基-5α-胆甾烷,     

生物医学样品中路易氏剂代谢产物分析检测方法研究进展

综述生物医学样品中路易氏剂代谢产物分析方法的研究现状,主要总结了路易氏剂染毒生物医学样品中标志物、样品制备和仪器分析方法的研究进展。路易氏剂染毒生物标志物主要包括游离和加合代谢产物两种,分析过程主要是对选定的生物标志物进行巯基化衍生和富集纯化,之后采用气相色谱–质谱、液相色谱–质谱等仪器对目标物进行检测鉴定。     

无机磷试剂辅助均环肽库的建立及其电喷雾质谱研究

在无机磷试剂辅助下建立了氨基酸自组装成均环肽的方法, 得到了相应的均环肽库. 均环肽库的建立增加了肽库的多样性, 为药物筛选提供了新的选择性. 采用电喷雾多级质谱技术, 对系列均环多肽 [M＋H]＋离子和[M＋Na]＋离子的质谱裂解规律进行了系统研究, 两种系列的离子具有不同的质谱裂解特征, 分别提出了其可能的质谱裂解机制. 该研究丰富了环多肽化合物的电喷雾多级质谱研究, 结果表明环肽化合物的加钠离子较加氢离子的质谱图可以更容易地用于环多肽的序列测定. 本研究为其它类似环肽化合物结构的分析鉴定及利用电喷雾质谱推测环肽序列提供了有效的质谱方法.     

The role of pattern recognition in the computer-aided classification of mass spectra

The requirements for the use of pattern recognition techniques as an aid in the identification of chemical substances from their mass spectra are reviewed. Decision-tree pattern recognition is recommended as potentially satisfying these requirements. Examples of this approach using a large data base of mass spectra are provided.     

Top-down identification of endogenous peptides up to 9 kDa in cerebrospinal fluid and brain tissue by nanoelectrospray quadrupole time-of-flight tandem mass spectrometry

Recent work on protein and peptide biomarker patterns revealed the difficulties in identifying their molecular components, which is indispensable for validation of the biological context. Cerebrospinal fluid and brain tissue are used as sources to discover new biomarkers, e.g. for neurodegenerative diseases. Many of these biomarker candidates are peptides with a molecular mass of <10 kDa. Their identification is favourably achieved with a 'top-down' approach, because this requires less purification and an enzymatic cleavage will often not yield enough specific fragments for successful database searches. Here, we describe an approach using quadrupole time-of-flight mass spectrometry (TOFMS) as a highly efficient mass spectrometric purification and identification tool after off-line decomplexation of biological samples by liquid chromatography. After initial peptidomic screening with matrix-assisted laser desorption/ionization (MALDI) TOFMS, the elution behaviour in chromatography and the exact molecular mass were used to locate the same signals in nanoelectrospray measurements. Most of the peaks detected in MALDI-TOFMS could be retrieved in nanoelectrospray quadrupole TOFMS. Suitable collision energies for informative fragment spectra were investigated for different parent ions, charge states and molecular masses. After collision-induced dissociation, the resulting fragmentation data of multiply charged ions can become much more complicated than those derived from tryptic peptide digests. However, the mass accuracy and resolution of quadrupole TOF instruments results in high-quality data suitable for determining peptide sequences. The protein precursor, proteolytic processing and post-translational modifications were identified by automated database searches. This is demonstrated by the exemplary identifications of thymosin beta-4 (5.0 kDa) and NPY (4.3 kDa) from rat hypothalamic tissue and ubiquitin (8.6 kDa) from human cerebrospinal fluid. The high data quality should also allow for de novo identification. This methodology is generally applicable for peptides up to a molecular mass of about 10 kDa from body fluids, tissues or other biological sources.     

NMR and pattern recognition methods in metabolomics: From data acquisition to biomarker discovery: A review

Metabolomics is the discipline where endogenous and exogenous metabolites are assessed, identified and quantified in different biological samples. Metabolites are crucial components of biological system and highly informative about its functional state, due to their closeness to functional endpoints and to the organism's phenotypes. Nuclear Magnetic Resonance (NMR) spectroscopy, next to Mass Spectrometry (MS), is one of the main metabolomics analytical platforms. The technological developments in the field of NMR spectroscopy have enabled the identification and quantitative measurement of the many metabolites in a single sample of biofluids in a non-targeted and non-destructive manner. Combination of NMR spectra of biofluids and pattern recognition methods has driven forward the application of metabolomics in the field of biomarker discovery. The importance of metabolomics in diagnostics, e.g. in identifying biomarkers or defining pathological status, has been growing exponentially as evidenced by the number of published papers. In this review, we describe the developments in data acquisition and multivariate analysis of NMR-based metabolomics data, with particular emphasis on the metabolomics of Cerebrospinal Fluid (CSF) and biomarker discovery in Multiple Sclerosis (MScl).     

Link test--A statistical method for finding prostate cancer biomarkers

We present a new method, link-test, to select prostate cancer biomarkers from SELDI mass spectrometry and microarray data sets. Biomarkers selected by link-test are supported by data sets from both mRNA and protein levels, and therefore results in improved robustness. Link-test determines the level of significance of the association between a microarray marker and a specific mass spectrum marker by constructing background mass spectra distributions estimated by all human protein sequences in the SWISS-PROT database. The data set consist of both microarray and mass spectrometry data from prostate cancer patients and healthy controls. A list of statistically justified prostate cancer biomarkers is reported by link-test. Cross-validation results show high prediction accuracy using the identified biomarker panel. We also employ a text-mining approach with OMIM database to validate the cancer biomarkers. The study with link-test represents one of the first cross-platform studies of cancer biomarkers.     

Interpretation Automatique des Spectres de Masse de Composes Organiques. Mise au Point

Computerized methods for interpretation of mass spectra are increasing and many papers have now been published. Three different approaches can be used to identify an unknown compound. These methods are reviewed and discussed. First, the heuristic technique which tries to simulate the reasoning of the chemist and deduce the formulae. The only information needed are the mass spectra, the empirical formulae and the n.m.r. spectra. Some promising results have been obtained but the method has important restrictions. Another approach represents the mass spectra as points in a hyperspace. By developing decision surfaces it is possible to classify an unknown compound. This is called pattern recognition and the different empirical methods for recognizing patterns in mass spectral data are explained and reported. The last and simplest technique is to match an unknown spectrum against a library of standard references. When the unknown spectrum is in the library, this approach gives the best results.     

Stability-based biomarker selection

Biomarker identification, i.e., finding those variables that indicate true differences between two or more populations, is an ever more important topic in the omics sciences. In most cases, the number of variables far exceeds the number of samples, making biomarker identification extremely difficult. We present a strategy based on the stability of putative biomarkers under perturbation of the data, and show that in several cases important gains can be achieved. The strategy is very general and can be applied with all common biomarker identification methods; it also has the advantage that it does not rely on error estimates from crossvalidation, that in this setting tend to be highly variable.     

Discrimination of Penicillium isolates by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry fingerprinting

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used to generate highly reproducible mass spectral 'fingerprints' for twelve Penicillium species. Prior to MALDI-TOF MS analysis, eight replicate cultures of each Penicillium species were subjected to three one-minute bead-beating cycles in an acetonitrile/trifluoroacetic acid solvent. The mass spectra contained abundant peaks in the range of m/z 5000-20 000, and allowed unambiguous discrimination between species. In addition, a biomarker common to all Penicillium mass spectra was observed at m/z 13 900. Discriminant analysis using the MALDI-TOF MS data yielded classification error rates of 0% (i.e. 100% correct identification), indicating that MALDI-TOF MS data may be a useful diagnostic tool for the objective identification of Penicillium species of environmental and clinical importance.     

Identification of polymers by library search of pyrolysis mass spectra and pattern recognition analysis

A library of mass spectra of polymers containing about 200 entries is described. These spectra were obtained by direct pyrolysis-electron-impact mass spectrometry, i.e., by heating the polymers in the direct insertion probe for solid samples at a constant heating rate and recording repetitive mass spectra during the temperature rise. The library can be used both as a data base for library searches and as a training set for a pattern recognition analysis. The algorithm used to generate and search the files and a few applications of the library search and pattern recognition analysis are presented.     

Targeted biomarker detection via whole protein ion trap tandem mass spectrometry: thymosin beta4 in a human lung cancer cell line

N-Terminally acetylated thymosin beta4, a species implicated for use as a cancer biomarker, was identified in a human lung cancer cell line using ion trap tandem mass spectrometry at the whole protein level. Ion-ion proton transfer reactions were used for parent ion concentration/manipulation and to simplify interpretation of product ion spectra. Dissociation data for the +6 to +3 charge states are reported. As is usually the case, structural information available from the ion trap collisional activation of the protein is sensitive to parent ion charge state. Each parent ion charge state selected, however, provided sufficient information to make a confident identification. Furthermore, each charge state provided relatively rich fragmentation. Therefore, any of the charge states can be used to detect with high specificity thymosin beta(4) in a complex protein mixture. There are advantages associated with the rapid detection of protein biomarkers at the whole protein level, as opposed to the peptide level following protein digestion, particularly for relatively small protein and polypeptide biomarkers. Having identified and characterized the protein, product ion spectra obtained directly, without recourse to ion-ion proton transfer reactions, can be used for library matching. However, ion-ion proton transfer reactions for parent ion concentration and charge state purification are advantageous in addressing relatively complex mixtures.     

Rapid identification of environmental bacterial strains by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

In recent years, various mass spectrometry procedures have been developed for bacterial identification. The accuracy and speed with which data can be obtained by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) could make this a powerful tool for environmental monitoring. However, minor variations in the sample preparation can influence the mass spectra significantly. Therefore, the first objectives of this study were the adjustment and the optimization of experimental parameters allowing a rapid identification of whole bacterial cells without laborious sample preparation. The tested experimental parameters were matrix, extraction solvent, salt content, deposition method, culture medium and incubation time. This standardized protocol was applied to identify reference and environmental bacterial strains of Escherichia coli, Salmonella and Acinetobacter. The environmental bacterial strains were isolated from sewage sludge using an original microextraction procedure based on repeated sonications and enzymatic treatments. The bacterial identification was realized by the observation of the respective genus-, species- and strain-specific biomarkers. This bacterial taxonomy could be completed within one hour, with minimal sample preparation, provided that sufficient bacteria had been collected prior to MALDI-TOF analysis.