MALDI TOF MS system

Waters Corporation has now introduced the MicrobeLynx , a MALDI-TOF MS system developed for fingerprint bacterial ID. The system and its applications are described thus ... 

Recently, we described the first example of the coupling of a microfluidics device to a MALDI-TOF mass spectrometer, by integrating an on-chip microreaction unit with a MALDI-TOF standard sample plate.27 This allows (bio)chemical reactions to take place in the MALDI-TOF instrument. Since it is based on a pressure-driven fluidics handling method, using the vacuum in the ionization chamber of the MALDI-TOF-MS system, this approach avoids wires and tubes for feed and flow control. 

DE-MALDI TOF-MS systems can be set up to detect these ions and determine their m/z for structure determination. The technique is called postsource decay and it is particularly important in determining the sequence of amino acids in peptides formed from proteolytic digestion of proteins. 

Lacroix C, Gicquel A, Sendid B, Meyer J, Accoceberry I, Francois N, Morio F, Desoubeaux G, Chandenier J, Kauffmann-Lacroix C, Hennequin C, Guitard J, Nassif X, Bougnoux ME. Evaluation of two matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) systems for the identification of Candida species. Clin Microbiol Infec. 2014 20(2) 153-8. 

Mokrzycki-Issartel, N., Bouchon, B., Farrat, S., Berland, P, Laparra, H Madelmont, J.-C., and Theisen, M. (2003). A transient tobacco expression system coupled to MALDI-TOF-MS allows validation of the impact of differential targeting on structure and activity of a recombinant therapentic glycoprotein produced in plants. FEBS Lett. 552 170-176. 

MALDI-TOF-MS facilitates the analysis of carotenoids and other natural products with detection limits that are lower than most other techniques. For example, subpicomole quantities can be detected (Wingerath et al., 1999). The enhanced sensitivity is the result of the efficiency of the pulsed ionization and detection system in which a complete mass spectrum is recorded with each laser flash. Like FAB and LSIMS, molecular ions are the most abundant sample ions, although some protonated molecules and [M-H]+ ions may be formed as well. Abundant molecular ions of carotenoid esters have been observed using MALDI-TOF-MS (Kaufmann et al., 1996 Wingerath et al., 1996),... 

Figure 10 Procedure for multiplexed quantitative gene expression analysis using competitive PCR coupled with MALDI-TOF MS (MassARRAY system). Primers for three transcripts (CXCR4, HMBS, and GAPDH) to be measured simultaneously are depicted. Figure 11 illustrates the results for such an experiment.

A relevant set of not experimentally infected individuals (control) is required for differential analysis by MALDI-TOF-MS or RP-HPLC in order to discriminate between immune-induced molecules and constitutively present substances (19). This is a prerequisite when no in vitro assays are used to select the bioactive peptides from the immune system of the model invertebrate investigated. 

Various comprehensive studies on the polymerization of enantiopure and racemic esters of a-amino acids performed at the air/water interface to yield peptides have been reported over the years [189,190]. Recent reinvestigations of the products of these reactions by MALDI-TOF MS have demonstrated, however, that they are not longer than dipeptides [191]. For this reason, such esters cannot be regarded as realistic prebiotic model systems for the formation of long oligopeptides. On the other hand, amphiphilic Na-carboxyanhydrides [192] and thio-esters [193] of a-amino acids yield longer oligopeptides. 

Scheme4.88 Microfluidic system for MALDI protein analysis, (a) automated sample pretreatment and injection (b) microreactor (c) microdispenser used to deposit sample into nanovials (d) shallow nanovials on the MALDI target plate and (e) automated MALDI-ToF-MS analysis. Reprinted with permission from [345]. Copyright 2000 American Chemical Society.

The wide application of newly developed advanced Surface MALDI MS methods, such as laser desorption ionization (LDI), surface-enhanced laser desorption ionization (SELDI), direct ionization on silicon surface (DIOS), etc. have two shortcomings. First, problems with MALDI-TOF MS sample preparation for nano-sized systems have not been completely worked out. Second, the reliability and reproducibility of experimental data concerning similar bio-active systems is lacking. Sometimes molecular, associative and fragment ions cannot, be observed in the MALDI mass spectra. We are currently working on overcoming these difficulties with some encouraging results.13,14... 

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