Mass spectrometry ionization approaches

Tesche, F. Pickard, V. Matrix effects during analysis of plasma samples by electrospray and atmospheric pressure chemical ionization mass spectrometry practical approaches to their elimination. Rapid Commun Mass Spectrom 2003, 17, 1950—1957. 

Hou W, Watters JW, McLeod HL (2004) Simple and rapid docetaxel assay in human plasma by protein precipitation and high-performance liquid chromatography-tandem mass spectrometry. Journal of Chromatography B 804 263-267 Schuhmacher J, Zimmer D, Tesche F, Pickard V (2003) Matrix effects during analysis of plasma samples by electrospray and atmospheric pressure chemical ionization mass spectrometry practical approaches to their elimination. Rapid Communications in Mass Spectrometry 17 1950-1957 Shah PW (2001) Guidance for Industry Bioanalytical Method Validation U.S. Department of Health and Human Services, Food and Drug Administration... 

The first chapter gives a comprehensive introduction to the combination of miniaturization and mass spectrometry by approaching several aspects of this coupling. After a short recall of MS analysis and of the two soft ionization techniques of ESI and MALDI, we mention a number of motivations that encouraged people to use microfabrication techniques in the field of MS analysis and we describe also how they have done it and for which fields this unique combination is applied. 

Schweer, J., Samecki, J., Mayer Posner, F., Mullen, K., Rader, H.J., and Spickermann, J., Pulsed-Laser Polymerization/Matrix-Assisted Laser Desorption/ionization Mass Spectrometry. An approach toward Free-Radical Propagation Rate Coefficients of Ultimate Accuracy, Macromolecules 29, 4536 (1996). 

R. S. Annan, M. J. Huddleston, R. Verma, R. J. Deshaies, and S. A. Carr, A multidimensional electrospray ionization mass spectrometry-based approach to phos-phopeptide mapping. Anal. Chem. 73, 393-404 (2001). 

However, interpretation of, or even obtaining, the mass spectrum of a peptide can be difficult, and many techniques have been introduced to overcome such difficulties. These techniques include modifying the side chains in the peptide and protecting the N- and C-terminals by special groups. Despite many advances made by these approaches, it is not always easy to read the sequence from the mass spectrum because some amide bond cleavages are less easy than others and give little information. To overcome this problem, tandem mass spectrometry has been applied to this dry approach to peptide sequencing with considerable success. Further, electrospray ionization has been used to determine the molecular masses of proteins and peptides with unprecedented accuracy. 

Smith, R.M., Gas and Liquid Chromatography in Analytical Chemistry, Wiley, Chichester, U.K., 1988. Smith, R.M. and Busch, K.L., Understanding Mass Spectra A Basic Approach, Wiley, Chichester, U.K., 1998. Snyder, A.R, Biochemical and Biotechnological Applications of Electrospray Ionization Mass Spectrometry, Oxford University Press, Oxford, 1998. 

Using the same threshold ionization mass spectrometry setup, Perrin et al. [317] have measured the temporal decay of radical densities in a discharge afterglow. From these experiments the coefficient p for the radical SiH. has been determined to be 0.28, which is in agreement with already known results from other (indirect) experimental approaches [136,137,318]. For the Si2H5 radical is determined to be between 0.1 and 0.3. The coefficient p for atomic hydrogen on a-Si H lies between 0.4 and 1, and is thought to represent mainly surface recombination to H. ... 

In contrast to thermal ionization methods, where the tracer added must be of the same element as the analyte, tracers of different elemental composition but similar ionization efficiency can be utilized for inductively coupled plasma mass spectrometry (ICPMS) analysis. Hence, for ICPMS work, uranium can be added to thorium or radium samples as a way of correcting for instrumental mass bias (e g., Luo et al. 1997 Stirling et al. 2001 Pietruszka et al. 2002). The only drawback of this approach is that small inter-element (e g., U vs. Th) biases may be present during ionization or detection that need to be considered and evaluated (e.g., Pietruszka et al. 2002). 

Tandem mass spectrometry (MS/MS) is another common approach used for protein identification. In this method, proteins are digested and the resulting peptides are ionized directly from the liquid phase by... 

Arnold, R. J. Reilly, J. P. Fingerprint matching of E. coli strains with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry of whole cells using a modified correlation approach. Rapid Commun. Mass Spectrom. 1998,12,630-636. 

The focus of this chapter is the development of a technique often called wholecell matrix-assisted laser desorption ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS) or whole-cell MALDI-TOF MS. Some groups prefer to use terms such as intact or unprocessed rather than whole, but the intended meaning is the same regardless of which word is used. As noted in the first chapter of this book, there are many different methods for the analysis of bacteria. However, for the analysis of intact or unprocessed bacteria, whole-cell MALDI-TOF MS is the most commonly used approach. This method is very rapid. MALDI-TOF MS analysis of whole cells takes only minutes because the samples can be analyzed directly after collection from a bacterial culture suspension. Direct MALDI MS analysis of fungi or viruses is similar in approach1,2 but is not covered in this chapter. MALDI-TOF MS of whole cells was developed with very rapid identification or differentiation of bacteria in mind. The name (whole cell) should not be taken to imply that the cells are literally intact or whole. Rather, it should be taken to mean that the cells that have not been treated or processed in any way specifically for the removal or isolation of any cellular components from any others. In whole-cell analysis the cells have been manipulated only as necessary to... 

DEVELOPMENT OF SPECTRAL PATTERN-MATCHING APPROACHES TO MATRIX-ASSISTED LASER DESORPTION/ IONIZATION TIME-OF-FLIGHT MASS SPECTROMETRY FOR BACTERIAL IDENTIFICATION... 

Electrospray (ESI) ionization mass spectrometry also plays in important role in bacterial characterization. Because it typically includes a chromatographic separation step, the approach is not considered as rapid as MALDI approaches, which do not incorporate a separation. However, compared to the times needed to grow bacteria in culture prior to analysis, the time frame is not lengthy, and the addition of chromatographic separation provides many opportunities to increase specificity. ESI/MS has been used to characterize cellular biomarkers for metabolic, genomic, and proteomics fingerprinting of bacteria, and these approaches are reported in two chapters. 

The ability to resolve and characterize complicated protein mixtures by the combination of 2DLC and online mass spectrometry permits the combination of sample fractionation/simplification, top-down protein mass information, and bottom-up peptide level studies. In our lab, the simplified fractions generated by 2D(IEX-RP)LC are digested and analyzed using common peptide-level analysis approaches, including peptide mass fingerprinting (Henzel et al., 1993 Mann et al., 1993), matrix-assisted laser desorption/ionization (MALDI) QTOF MS/MS (Millea et al., 2006), and various capillary LC/MS/MS methodologies (e.g., Ducret et al., 1998). 

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