Mass spectrometry, combinatorial library analysis

Tolson, D. Organ, A. Shah, A. Development of a High-pressure Gradient Pumping System for Parallel Liquid Chromatography/Mass Spectrometry for the Analysis of Combinatorial Libraries, Rapid Commun. Mass Spectrom. 15, 1244-1249 (2001). 

Hughes, L Design of self-coded combinatorial libraries to facilitate direct analysis of ligands by mass spectrometry. J. Med. Chem. 1998, 41, 3804-3811. 

Shin YG, van Breemen RB Analysis and screening of combinatorial libraries using mass spectrometry. Biopharm Drug Dispos 2001, 22, 353-372. 

ESI-MS has been used for the quantification of a number of substrates and products of enzymatic reactions [56,57]. Hsieh et al. report the use of ion spray mass spectrometry (a technical variation of electrospray ionization) coupled to HPLC for the kinetic analysis of enzymatic reactions in real time [58]. The hydrolysis of dinucleotides with bovine pancreatic ribonuclease A and the hydrolysis of lactose with 3-galactosidase were monitored and the resulting data were used for the estimation of and v x of these reactions. Another field of application of electrospray mass spectrometry is the screening of combinatorial libraries for potent inhibitors [31,59]. 

Nawrocki, J. P., Wigger, M., Watson, C. H., Hayes, T. W., Senko, M. W., Benner, S. A., and Eyler, J. R. (1996). Analysis of combinatorial libraries using electrospray Fourier transform ion cyclotron resonance mass spectrometry. Rapid Commun. Mass Spectrom. 10 1860-1864. 

Wang, T. Zeng, L. Strader, T. Burton, L. Kassel, D. B. 1998. A new ultra-high throughput method for characterizing combinatorial libraries incorporating a multiple probe autosampler coupled with flow injection mass spectrometry analysis. Rapid Commun. Mass Spectrom., 12, 1123-1129. 

Boutin JA, Hennig P, Lambert PH, Bertin S, Petit L, Mahiev JP, Serkiz B, Volland JP, Fauchere JL, Combinatorial peptide libraries Robotic synthesis and analysis by nuclear magnetic resonance, mass spectrometry, tandem mass spectrometry, and high-performance capillary electophoresis techniques, Anal. Biochem., 234 126-141, 1996. 

LC-NMR data may be acquired in either onflow or stopped-flow modes. In the onflow mode, effluent flows directly from the column through the probe, where spectra are collected at fixed time intervals. Figure 4 shows a typical onflow LC-NMR spectrum.6 In the stopped-flow mode, several fractions are collected and analysed individually at a later time. Although mass spectrometry continues to be the favoured technique for the analysis of combinatorial libraries, the value of LC-NMR was demonstrated in a study by Chin et al.A1 in a stopped-flow study of four positional isomers of dimethoxybenzoylglycine. Iso-molecular-weight mixtures such as this can be problematic to analyse using mass spectrometry however, in this case assignment of the compounds was readily accomplished from the LC-NMR data (Fig. 5). 

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. 

Coupled chromatography-mass spectrometry techniques for the analysis of combinatorial libraries... 

Recent years has seen a paradigm shift in the way drugs are discovered and produced. Many areas of drug discovery rely on combinatorial approaches to produce more opportunities and screen more compounds. This has altered the way analysis is performed in all areas and none more so than in the analysis of combinatorial libraries. The rapid development of specialised coupled chromatography-mass spectrometry techniques for... 

As for all synthetic products to be tested in biological systems, a careful analytical characterization of peptide libraries is crucial in order to confirm their identity and establish their quality. Compared to individual peptides, however, the analysis of peptide libraries is complicated due to the fact that the peptides are either bound to a solid support or arranged in highly complex mixtures. This poses certain restrictions on which analytical methods can be used to characterize combinatorial libraries. For example, analytical methods that are based on the separation of product components, such as high performance liquid chromatography (HPLC) and capillary electrophoresis (CE), are only of limited use for the analysis of peptide libraries, in particular of those made up of complex nnixtures (>100 peptides per mixture). The analytical methods beneficially applicable to peptide libraries include amino acid analysis, mass spectrometry, and sequencing. 

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