Tandem mass spectrometry acid derivatives

Figure 2.5. Tandem mass spectrometry. A. A peptide mixture is electrosprayed into the mass spectrometer. Individual peptides from the mixture are isolated (circled peptide) and fragmented. B. The fragments from the peptide are mass analyzed to obtain sequence information. The fragments obtained are derived from the N or C terminus of the peptide and are designated "b" or "y" ions, respectively. The spectrum shown indicates peptides that differ in size by the amino acids shown.

When using PFT with a neutral selector, it is quite difficult to avoid any entrance of the chiral selector into the ionization source, particularly at a high pH, where EOF is important. The use of BGE at low pH and/or coated capillary to minimize EOF is therefore mandatory. However, the coaxial sheath gas, which generally assists the ionization process, leads to an aspirating phenomenon of the chiral selector in the MS direction. Javerfalk et al. were the first to apply PFT with a neutral methyl-/i-CD for the separation of racemic bupivacaine and ropivacaine with a polyacrylamide-coated capillary and an acidic pH buffer (pH 3). Cherkaoui et al. employed another neutral CD (HP-/1-CD) with a PVA-coated capillary for the analysis of amphetamines and their derivatives. To prevent a detrimental aspiration effect, analyses were carried out without nebulization pressure. Numerous other studies presented excellent results such as the enantioselective separation of adrenoreceptor antagonist drugs using tandem mass spectrometry (MS/MS) the separation of clenbuterol enantiomers after solid-phase extraction (SPE) of plasma samples or the use of CD dual system for the simultaneous chiral determination of amphetamine, methamphetamine, dimethamphetamine, and p-hydroxymethamphetamine in urine. 

Kozar, M., and Fox, A. (2002), Analysis of a stable halogenated derivative of muramic acid by gas chromatography-negative ion chemical ionization tandem mass spectrometry, J. Chromatogr., 946, 229-238. 

In the absence of tandem mass spectrometry equipment, almost equally reliable estimations of the PA concentrations can be made using gas chromatography-mass spectrometry (GC-MS). A standard quadrupole instrument, such as the one used for organic acid analysis, will be sufficient. Depending on the derivative, a choice between positive and negative ionization will have to be made. In general, a more extensive prepurification of the biological samples, will have to be realized. 

The basic goal of the mass spectrometry measurement in the context of peptide analysis in proteomics and phosphoproteomics is to determine specific attributes that are then used in subsequent database searches to provide 1. the identity of the proteins present in the sample 2. location of the site(s) of phosphorylation in these proteins. Both pieces of information are derived from the mass of the peptide and, most importantly, from the gas-phase dissociation patterns that are diagnostic of the peptide s amino acid sequence and phosphosite location. The gas-phase dissociation patterns are obtained via tandem mass spectrometry (MS/MS). On a phosphoproteome-wide scale, the analysis includes measurement of the attributes for many thousands of individual peptides. 

Deterding, L. J. and Gross, M. L. Tandem mass spectrometry for identifying fatty acid derivatives that undergo charge-remote fragmentations. Org. Mass Spectrom. 23 169-177, 1988. 

The differentiation of anomeric acyclonucleosides by FAB tandem mass spectrometry was reported (90MI1 91MI10). Regioisomeric compounds could be differentiated by kinetic energy release measurements [87-AQ(C)271 91RCM72]. Electronic structure, spectral properties, and acid-base and tautomeric equilibria of some adenosine acyclo derivatives were investigated (89MI5). 

J. A. ZirroUi and R. C. Murphy, Low-enragy tandem mass spectrometry of the molecnlar ion derived from fatty acid methyl estes a novel method for analysis of branched-chain fatty acids, J. Am. Soc. Mass Spectrom. 4, 223-229 (1993). 

A number of MS investigations report putative adenylylated peptides, with the majority only conducted at the MS level, with the exception of a few, which were conducted at the tandem mass spectrometry (MS/MS) level. The distinct mass shift upon adenylylation of amino acid residues (serine, threonine, or tyrosine) renders it a good target for MS detection and identification. However, the fragmentation of adenylylated tryptic peptides derived from adenylylated proteins has only recently been systematically investigated. We demonstrated that adenylylated peptides show loss of parts of the AMP upon different fragmentation techniques (Figure 9.4). 

Jia, M. Wu, W.W. Yost, M.G. Chadik, P.A. Stacpoole, P.W. Henderson, G.N. Simultaneous determination of trace levels of nine haloacetic acids in biological samples as their pentafluorobenzyl derivatives by gas chromatogra-phy/tandem mass spectrometry in electron capture negative ion chemical ionization mode. Anal. Chem. 2003, 75, 4065 080. 

Fig. 10.8. Nanoparlicie-assisted iaser desorption/ionization imaging of iipids. Upper panel) Opticai images of rat cerebeiium tissue before/after being sprayed with nanopar-ticies (NPs) and 2,5-dihydroxybenzoic acid (DffB) soiution were shown. Successive brain section stained with hematoxyiin-eosin (ff E) is aiso presented. Middle panel) ton images obtained with NPs and DHB are shown. Visuatized ions were identified as gaiactosyiceramide (C24h 0) and PC (diacyi-34 2) by tandem mass spectrometry on both DHB- and NP-coated sections. Bottom panel) Exampie representation of MS/MS resuif on fhe tissue sprayed with NP, for ion at m/z 850.8. Product ion spectmm indicates that the ion was derived from gaiacfosyiceramide(C24h 0).

Recently, automated multiple development (AMD) thin layer chromatography has been applied for the analyis of caffeic acid derivatives in E. angustifolia root extracts [45, 46]. The separation was performed on silica plates (Sil G-50 UV 254) and AMD was achieved in 25 steps using methanol, ethylacetate, toluene, 1,2-di-chloroethane, 25% ammonia solution, and anhydrous formic acid as modifiers. For the screening of echinacoside in crude plant extracts, a fast-atom-bombardment tandem mass spectrometry method has been developed [47, 48]. 

Uutela P, Ketola RA, Piepponen P, Kostiainen R. Comparison of different amino acid derivatives and analysis of rat brain microdialysates by liquid chromatography tandem mass spectrometry. Anal Chim Acta 2009 633 223-31. 

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