MALDI-TOF MS analysis

FIGURE 10.5 (a) MALDI-TOF MS analysis of the apo-form of bovine Cu, Zn superoxide... 

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... 

Another interesting comparison has recently been made between MALDI-TOF MS analysis of whole cells, and MALDI FTMS of the same organisms. This work is reported in greater detail in a dedicated chapter later in this book. It should be noted here that it appears to be much more difficult to obtain spectra from intact bacteria by MALDI FTMS than it is by MALDI-TOF MS. Thus far only a single research group has reported protein-like ions desorbed directly from intact cells by MALDI FTMS. 

Approximately 90% to 95% of whole-cell MALDI MS profiles are representative of the ribosomal proteins abundant in rapid growth whole cells. Although the identification of proteins, from whole bacterial cells, by MALDI-TOF MS analysis is ambiguous, at best, due to the low-mass accuracy and resolving power, several researchers realized that many of the observed... 

Wang J and Sporns P. 2000a. MALDI-TOF MS analysis of food flavonol glycosides. J Agric Food Chem... 

Comparative sequence analysis based on MALDI-TOF-MS analysis of nucleic acids cleaved at specific bases and reference sequences used to construct in silico cleavage patterns enable cross-correlation of theoretical and experimental mass signal patterns. Observed signal pattern differences are indicators of sequence variations and... 

Wang, J., Kalt, W., and Sporns, P., Comparison between HPLC and MALDI-TOF MS analysis of anthocyanins in highbush blueberries, J. Agric. Food Chem., 48, 3330, 2000. 

Boc-OSu (200 mg, 950 pmol) and DIPEA (170 pL, 950 pmol) were added to the soln of peptide 20 (230 mg, 26 pmol) in DMSO (1 mL), and the mixture was stirred for 1.5 h. Et20 was added to precipitate the product, which was collected by centrifugation to give peptide 21 (Xaa= Ahx) yield HOmg (12% based on the pMeBHA resin amino group). MALDI-TOF-MS analysis gave [M + H]+ 4350.5 Da (calcd 4350.8 Da). 

Many other applications have been carried out using semi-quantitative primer extension based MALDI-TOF MS analysis with unknown analyte concentrations. One example involves the quantification of differential allele-specific expression. Medelian inheritance of allele-specific expression has been shown in humans (40). Allele-specific expression is of great importance for the identification of genetic components, which lead to population... 

Fig. 17 MALDI-TOF MS analysis of oligopeptides obtained from a racemic and b, c 3 7 and 4 6 L/D non-racemic mixtures of Ci8-G1u-NCA monomers. The vertical axis represents the relative abundance of each type of oligopeptide (h, d), where h is the number of R (unlabeled) repeat units and d the number of S (deuterated) repeat units e.g. (4,0) is the tetrapeptide containing four D repeat units and zero L repeat units. For oligopeptides with the same number of repeat units, ion intensity (I) and amount are reliably proportional. The relative abundance was calculated according to the equation shown below for the (4,0) tetrapeptide relative abundance (4,0) =7(4,0)/I[(4,0) + (3,1) + (2,2) + (1,3) + (0,4)]. For clarity, the distributions of only some of oligopeptides are shown...

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.

E. Elhanany, A. Ordentlich, O. Dgany, D. Kaplan, Y. Segall, R. Barak, B. Velan and A. Shafferman, Resolving pathways of interaction of covalent inhibitors with the active site of acetylcholinesterases MALDI-TOF/MS analysis of various nerve agent phosphyl adducts, Chem. Res. Toxicol., 14, 912-918 (2001). 

R. Erra-Balsells and H. Nonami, UV-MALDI-TOF MS analysis of carbohydrates. Reviewing comparative studies performed using nor-harmane and classical UV-MALDI matrices, Environ. Control Biol., 46 (2008) 65-90. 

Monagas, M. Quintanilla-Lopez, J.E. Gomez-Cordoves, C. Bartolome, B. Lehron-Aguilar, R. 2011. MALDI-TOF MS analysis of plant proanthocyanidins. J. Phar-maceut. Biomed. Anal. 51 358-372. 

Driedger, D.R., and Spoms, P. (2001) Immunoaffinity sample purification and MALDI TOF MS analysis of a solanine and a chaconine in serum. Journal of Agricultural and Food Chemistry, 49, 543 548. 

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