Mass spectrometry structural analysis

Coupling chromatographic procedures with immunochemical techniques can also provide a very sensitive and specific analytical system for either determinative or confirmatory analysis. If the antibody used is very specific for the analyte of interest and the antibody reactivity is known to be sensitive to small variations in the structure of the analyte tested, positive reactions with the method are strongly indicative that an analyte of defined structural characteristics is present in the sample. Full rigorous confirmation, however, would depend on further analysis by mass spectrometry, which is the method of choice in confirmatory analysis. Mass spectrometry gives specific information on the identity and structure of the compound of interest. Coupled with chromatographic techniques it becomes a very powerful confirmatory tool for both quantitative and qualitative assessment of drug residues in foods. 

The synthesis yielded a mixture of products. Compound 8 was distilled off and purified by gas chromatography. The structure was determined by elemental analysis, mass spectrometry and by a study of the pmr spectrum15 It is apparent from examination of a model that structure 8a will not exist for steric reasons. The methyl groups at the Si atoms 3 and 7 interfere with... 

Flow injection analysis mass spectrometry (FIA-MS) has been reported to be a fast method for the characterization of combinatorial libraries (55,56). The method verifies the presence of the molecular ions of the expected product and side products or impurities but does not provide information on the quality of the analyzed samples. Significant improvements related to the increased analytical throughput, obtained by reducing the time between each injection without increasing the intersample carry-over from each analysis, were recently reported (57, 58). When coupled with RP-HPLC, FIA-MS allows the separation and the determination of the molecular weight of the components of each sample. This is normally enough to unequivocally attribute the structure of the expected library component and of any side products from a library synthesis. 

The structure of 33 has been supported by using elemental analysis, mass spectrometry and NMR spectroscopy [119]. However, the NMR spectra provided a more complex depiction. They indicated the presence of five species in a CDCI3 solution of sanguinarine fi ee base (I) a major bimole-cular stereoisomer, the racemate 6R,6"R + 6S,6 S, vsdiich is thermodynamically voured according to AMI calculations [120] (II) a minor isomer, a... 

The ideal detector is universal yet selective, sensitive and structurally informative. Mass spectrometry (MS) currently provides the closest approach to this ideal. The combination of multi-dimensional gas chromatography with high resolution MS or mass-selective detectors in the single ion monitoring (SIM)-mode is currently the most potent analytical tool in enantioselective analysis of chiral compounds in complex mixtures [29]. Nevertheless, it must be pointed out that the application of structure specific detection systems like MS [51] or Fourier transform infrared (FT-IR) [52] cannot save the fundamental challenges to optimum (chiral) resolutions and effective sample clean-up [53]. 

Discovery Trapoxins A and B (1 and 2) were isolated as antitnmor agents from the culture broth of Helicoma ambiens RF-1023 [1]. The structures were determined by x-ray analysis, mass spectrometry, NMR, and chemical studies [1,2]. 

Vilkas and Lederer411 used the procedure for the O- and N-methylation of a natural peptide glycoside and report that it is superior to the Kuhn methylation procedure. Methylation of peptides is useful in the analysis of structures by mass spectrometry. 

The structures of purified GIPCs from yeast or mycelial forms of S. schenckii were determined by methylation analysis, mass spectrometry and NMR spectroscopy. 

Reactions of diastereomeric mixtures of imino-oxaphospholenes (79a-c) with hexafluoroacetone (80) gave in each case only one diastereomer of each of the bicyclicphosphoranes (81a-c). The structures of (81a) and (81b) were shown by X-ray crystallography to have distorted tbp geometries with the oxygen atoms apical and the O-P-O angles ca. 169°. The compounds were also fully characterised by analysis, mass spectrometry... 

A ) (Scheme 1-3) [59-61], Transformation of complexes Ni(acac)2 L (L = HMPA, DMF, MP, MSt)) leads to formation of homo bi-(L = HMPA, DMF, MP) or hetero three nuclear (L = MSt, M=Na, Li, K) heteroligand complexes A Ni2(OAc)3(acac)L (Scheme 1) [10], The structure of the complex A with =MP is proved kinetically and by various physical-chemical methods of analysis (mass-spectrometry, electron and IR-spec-troscopy, element analysis). 

The chemical structure of lipid A of lipopolysaccharide isolated from Comamonas testosteroni was recently determined by lida et al. (1996) by means of methylation analysis, mass spectrometry and NMR. The lipid A backbone was found to consist of 6-0-(2-deoxy-2-amino-P-D-glucopyrano-syl)-2-deoxy-2-amino-alpha-D-glucose which was phosphorylated in positions 1 and 4. Hydroxyl groups at positions 4 and 6 were unsubstituted, and position 6 of the reducing terminal residue was identified as the attachment site of the polysaccharide group. Fatty acid distribution analysis and ES/MS of lipid A showed that positions 2,2, 3 and 3 of the sugar backbone were N-acylated or O-acylated by R-3-hydroxydecanoic acid and that the hydroxyl groups of the amide-linked residues attached to positions 2 and 2 were further O-acylated by tetradecanoic and dodecanoic acids, respectively. 

This chapter has identified two major challenges in the analysis of flavour components of grapes. One is that components may be present at trace or ultra-trace levels, and this places special demands on detection, characterization and quantitative analysis. The second is that components also exist in precursor forms which, in the case of the glycosides, necessitate techniques suited to analysis of relatively involatile compounds with wide structural diversity. Mass spectrometry, coupled... 

Under routine conditions, enrichment and isolation of single anthocyanins followed by classical structural elucidation (mass spectrometry, elemental analysis, UVA IS absorbance evaluation using shift reagents, NMR, thin layer chromatography of sugars and anthocyanidins) is rarely necessary, hence will not be discussed in detail. Routine analysis focuses on the quantification and the distribution of known anthocyanins to confirm the content and source of anthocyanins. 

Improvements in the instrumentation, ionization sources, high-resolution mass analyzers, and detectors [67-69], in recent years have taken mass spectrometry to a different level of HPLC-MS for natural product analysis. Mass spectrometry detection offers excellent sensitivity and selectivity, combined with the ability to elucidate or confirm chemical structures of flavonoids [70-72]. Both atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) are most commonly used as ionization sources for flavonoid detection [73-76]. Both negative and positive ionization sources are applied. These sources do not produce many fragments, and the subsequent collision-induced dissociation energy can be applied to detect more fragments. Tandem mass spectrometry (MS , n> 2) provides information about the relationship of parent and daughter ions, which enables the confirmation of proposed reaction pathways for firagment ions and is key to identify types of flavonoids (e.g., flavones, flavonols, flavanones, or chalcones) [77-80]. 

C. J. Hogan, E. Folta-Stogniev, B. Ruotolo, J. Fernandez de la Mora, IMS-MS study of native aggregates, from insulin to GroEL. To be submitted to Anal. Chem. 2009 Hogan, C., Ruotolo, B., Robinson, C., Fernandez de la Mora, J. Tandem differential mobility analysis-mass spectrometry of the GroEL complex Structure compaction in the gas phase and inelastic air-protein interaction, Submitted to J. Phys. Chem. B, 2010. 

Biomolecular interaction analysis-mass spectrometry (BIA-MS), a combination of SPR with MS, was first explored by Krone et al. in 1996 where SPR was used to quantify interactions between proteins and MS was used to determine the structural features of die bound proteins. Review articles on SPR-MS describe recent progress in the field of SPR-MS, including future trends and possible applications. ... 

One has seen that the number of individual components in a hydrocarbon cut increases rapidly with its boiling point. It is thereby out of the question to resolve such a cut to its individual components instead of the analysis by family given by mass spectrometry, one may prefer a distribution by type of carbon. This can be done by infrared absorption spectrometry which also has other applications in the petroleum industry. Another distribution is possible which describes a cut in tei ns of a set of structural patterns using nuclear magnetic resonance of hydrogen (or carbon) this can thus describe the average molecule in the fraction under study. 

Ions are also used to initiate secondary ion mass spectrometry (SIMS) [ ], as described in section BI.25.3. In SIMS, the ions sputtered from the surface are measured with a mass spectrometer. SIMS provides an accurate measure of the surface composition with extremely good sensitivity. SIMS can be collected in the static mode in which the surface is only minimally disrupted, or in the dynamic mode in which material is removed so that the composition can be detemiined as a fiinction of depth below the surface. SIMS has also been used along with a shadow and blocking cone analysis as a probe of surface structure [70]. 

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