Tandem MALDI

Nielsen, M. L. Budnik, B. A. Haselmann, K. F. Zubarev, R. A. Tandem MALDI/EI ionization far tandem Fourier transfimn ion cyclotron resonance mass spectrometry of polypeptides. Int. J. Mass Spectrom. 2003, 226, 181 187. 

Anaslyuk, S.D., Shevchenko, N.M., Nazarenko, E.L., Imbs, T.I., Gorbach, V.I., Dmitrenok, P.S., and Zvyagintseva, T.N. (2010) Structural analysis of a highly sulfated fucan from the brown alga Laminaria cichorioides by tandem MALDI and ESI mass spectrometry. Carbohydr. Res., 345, 220-2212. 

Medzihradszky, K.F., Campbell, J.M., Baldwin, M.A., Falick, A.M., Juhasz, P., Vestal, M.L., and Burlingame, A.L., The characteristics of peptide collision-induced dissociation using a high-performance MALDI-TOF/TOF tandem mass spectrometer, Anal. Chem., 72, 552, 2000. 

Fast atom bombardment (FAB) Plasma desorption (PD) Liquid secondary-ion mass spectrometry (LSIMS) Thermospray (TSP)/plasmaspray (PSP) Electrohydrodynamic ionisation (EHI) Multiphoton ionisation (MPI) Atmospheric pressure chemical ionisation (APCI) Electrospray ionisation (ESI) Ion spray (ISP) Matrix-assisted laser desorption/ionisation (MALDI) Atmospheric pressure photoionisation (APPI) Triple quadrupole (QQQ) Four sector (EBEB) Hybrid (EBQQ) Hybrid (EB-ToF, Q-ToF) Tandem ToF-ToF Photomultiplier... 

Direct solid-state polymer/additive mass analysis has involved various ionisation modes El (Section 6.2.1), Cl (Section 6.2.2), DCI (Section 6.2.2.1), FAB (Section 6.2.4), FI (Section 6.2.5), FD (Section 6.2.6) and LD. Survey mass spectra obtained with soft ionisation methods (FI-MS, CI-MS) provide diagnostic overviews of chemical composition. The supplemental tandem (MS/MS) and atomic composition (AC-MS) techniques are used to make specific identifications of various organic ingredients. Direct analysis of polymer systems for more than a few thousand daltons has only just begun. Ionisation methods employed are FD, ESI and MALDI. Solid-probe ToF-MS (or DI-HRMS) is a breakthrough [188]. 

The major advantage of the tandem mass spectrometry approach compared to MALDI peptide fingerprinting, is that the sequence information obtained from the peptides is more specific for the identification of a protein than simply determining the mass of the peptides. This permits a search of expressed sequence tag nucleotide databases to discover new human genes based upon identification of the protein. This is a useful approach because, by definition, the genes identified actually express a protein. 

It should be pointed out that FAB, MALDI, and ESI can be used to provide ions for peptide mass maps or for microsequencing and that any kind of ion analyzer can support searches based only on molecular masses. Fragment or sequence ions are provided by instruments that can both select precursor ions and record their fragmentation. Such mass spectrometers include ion traps, Fourier transform ion cyclotron resonance, tandem quadrupole, tandem magnetic sector, several configurations of time-of-flight (TOF) analyzers, and hybrid systems such as quadrupole-TOF and ion trap-TOF analyzers. 

Warscheid, B. Jackson, K. Sutton, C. Fenselau, C. MALDI analysis of Bacilli in spore mixtures by applying a quadrupole ion trap time-of-fhght tandem mass spectrometer. Anal. Chem. 2003, 75, 5608-5617. 

Scrivens, J. Characterization of Oligomeric Systems Using MALDI MS/MS presented at 96 Lake Louise Workshop on Tandem Mass Spectrometry, Lake Louise, Canada 1996. 

Shimma S, Furuta M, Ichimura K. A novel approach to in situ proteome analysis using a chemical inkjet printing technology and MALDI-QIT-TOF tandem mass spectrometer. J. Mass. Spectrom. Soc. Jpn. 2006 54 133-140. 

TOF analyzers are especially compatible with MALDI ion sources and hence are frequently coupled in aMALDI-TOF configuration. Nevertheless, many commercial mass spectrometers combine ESI with TOF with great success. For proteomics applications, the quadrupole TOF (QqTOF) hybrid instruments with their superior mass accuracy, mass range, and mass resolution are of much greater utility than simple TOF instruments.21,22 Moreover, TOF instruments feature high sensitivity because they can generate full scan data without the necessity for scanning that causes ion loss and decreased sensitivity. Linear mode TOF instruments cannot perform tandem mass spectrometry. This problem is addressed by hybrid instruments that incorporate analyzers with mass selective capability (e.g., QqTOF) in front of a TOF instrument. 

UV/Visible Photodissociation. In the case of UV/visible PD the photon energies are high enough to enable direct fragmentation. Previously, UV photodissociation was utilized mainly to study dissociation kinetics of gas-phase ions, but recently it was demonstrated that UV PD could be used for tandem MS of MALDI generated protonated peptides [18]. 

K. F. Medzihradszky, J. M. Campbell, M. A. Baldwin, A. M. Falick, P. Juhasz, M. L. Vestal, and A. L. Burlingame. The Characteristics of Peptide Collision-Induced Dissociation Using a High-Performance MALDI-TOF/TOF Tandem Mass Spectrometer. Anal. Chem., 72(2000) 552-558. 

Biomolecular MS and in particular MALDI-TOF-MS (see Sections 2.1.22 and 2.2.1) permit the routine analysis of oligonucleotides up to 70-mers, intact nucleic acids, and the direct detection of DNA products with no primer labels with an increase in analysis speed and mass accuracy especially in contrast to traditional DNA separation techniques such as slab gels or capillary electrophoresis. Applications focus on the characterization of single nucleotide polymorphisms (SNPs) and short tandem repeats (STRs). Precise and accurate gene expression measurements show relative and absolute numbers of target molecules determined independently of the number of PCR cycles. DNA methylation can be studied quantitatively. 

B. Warscheid, K. Jackson, C. Sutton, and C. Fenselau. MALDI Analysis of Bacilli in Spore Mixtures by Applying a Quadrupole Ion Trap Time-of-Flight Tandem Mass Spectrometer. Anal. Chem., 75(2003) 5608-5617. 

Sequencing peptides with tandem mass spectrometry was carried out in the early 1980s (Biemann, 1986 Hunt et al., 1986 Hall et al., 1993). Usually the sensitivity and the lengths of sequences achievable were not sufficient to compete with Edman sequencing techniques. In 1988 and 1989, two efficient cold ionization techniques for large molecules were discovered MALDI (Karas and Hillenkamp, 1988) and the electrospray... 

Even though the MALDI peptide mass mapping technique is very powerful, it has limitations. It requires well-separated proteins, is less sensitive than identifications based on electrospray tandem mass spectrometry, can only identify proteins whose complete sequences are available in databases, and does not produce redundant information. 

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