Matrix-assisted laser desorption proteins

The ablated vapors constitute an aerosol that can be examined using a secondary ionization source. Thus, passing the aerosol into a plasma torch provides an excellent means of ionization, and by such methods isotope patterns or ratios are readily measurable from otherwise intractable materials such as bone or ceramics. If the sample examined is dissolved as a solid solution in a matrix, the rapid expansion of the matrix, often an organic acid, covolatilizes the entrained sample. Proton transfer from the matrix occurs to give protonated molecular ions of the sample. Normally thermally unstable, polar biomolecules such as proteins give good yields of protonated ions. This is the basis of matrix-assisted laser desorption ionization (MALDI). 

The three techniques — laser desorption ionization, laser ablation with secondary ionization, and matrix-assisted laser desorption — are all used for mass spectrometry of a wide variety of substances from rock, ceramics, and bone to proteins, peptides, and oligonucleotides. 

Laser-desorption mass spectrometry (LDMS) or matrix-assisted laser desorption ionization (MALDI) coupled to a time-of-flight analyzer produces protonated or deprotonated molecular ion clusters for peptides and proteins up to masses of several thousand. 

Experimentation showed that the protein was not glycosylated and that the sequence at the iV-amino acid terminus corresponded to that expected. The C-terminus sequence, however, did not correspond to that predicted and these data were interpreted in terms of the presence of a heterogeneous, truncated, protein. A study of the tryptic digest fragments from this protein with matrix-assisted laser desorption ionization (MALDI) with post-source decay enabled the authors to suggest the positions at which the parent protein had been truncated. 

Bemdt, P., Hobohm, U., and Langen, H. (1999). Reliable automatic protein identification from matrix-assisted laser desorption/ionization mass spectrometric peptide fingerprints. Electrophoresis 20, 3521-3526. 

Cain,T. Lubman, D. Weber, W. J. Differentiation of bacteria using protein profiles from matrix assisted laser desorption/ionization time of flight mass spectrometry. Rapid Comm. Mass Spectrom. 1994,8,1026-1030. 

Vaidyanathan, S. Winder, C. L. Wade, S. C. Kell, D. B. Goodacre, R. Sample preparation in matrix-assisted laser desorption/ionization mass spectrometry of whole bacterial cells and the detection of high mass (>20kDa) proteins. Rapid Comm. Mass Spectrom. 2002,16,1276-1286. 

Parker, C. E. Papac, D. L Tomer, K. B. Monitoring cleavage of fusion protein by matrix-assisted laser desorption ionization/mass spectrometry Recombinant HIV-1IIIB p26. Anal. Biochem. 1996, 239, 25-34. 

Jebanathirajah, J. A. Andersen, S. Blagoev, B. Roepstorff, P. A rapid screening method to monitor expression of recombinant proteins from various prokaryotic and eukaryotic expression systems using matrix-assisted laser desorption ioniza-tion-time-of-flight mass spectrometry. Anal. Biochem. 2002, 305, 242-250. 

Spengler, B. Kirsch, D. Kaufmann, R. Metastable decay of peptides and proteins in matrix-assisted laser-desorption mass spectrometry. Rapid Comm. Mass Spectrom. 1991, 5,198-202. 

The introduction and eventual commercialization of matrix-assisted laser desorption/ionization (MALDI) and electrospray (ESI) allowed biomarker status to be extended to proteins in 1996.15"17 With a few exceptions, ESI has been used in conjunction with extractions and high-pressure liquid chromatography (UPLC) interfaced with mass spectrometry. MALDI, on the other hand, has been widely adapted for rapid analysis of intact organisms, supported by bioinformatics.1819... 

Pineda, F. J. Antoine, M. D. Demirev, P A. Feldman, A. B. Jackman, J. Longenecker, M. Lin, J. S. Microorganism identification by matrix-assisted laser/desorption ionization mass spectrometry and model-derived ribosomal protein biomarkers. Anal. Chem. 2003,75,3817-3822. 

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