MALDI-MS analysis

Dai, Y., Whittal R.M., and Li, L., Two-layer sample preparation a method for MALDI-MS analysis of complex peptide and protein mixtures, Anal. Chem., 71, 1087, 1999. 

Bundy, J. Fenselau, C. Lectin-based affinity capture for MALDI-MS analysis of bacteria. Anal. Chem. 1999, 71,1460-1463. 

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... 

The two remaining shortfalls with MALDI-MS analysis of whole bacterial cells are sensitivity and mixture analysis. The sensitivity for MALDI-MS analysis of whole-cell bacteria from our experiments and those reported by other laboratories is about 107 cells/ml. To realistically utilize MALDI MS as a tool that meets DoD detector sensitivity goals, this should be 103 cells/ml or lower. 

Many situations exist when MALDI-MS analysis of a sample will involve a bacterial mixture or a single bacterium in a complex matrix. From our experience, MALDI-MS mixture analysis produces spectra that are highly irreproducible. Figure 14.5 represents spectra of two individual bacteria and a 50 50 mixture of the two bacteria. In the spectrum of the mixture the... 

Madonna et al. evaluated an immunologically based trapping/collection system to isolate bacteria prior to MALDI-MS analysis.27 Figure 14.6 illus-... 

S. L. Cohen and B. T. Chait Influence of Matrix Solution Conditions on the MALDI-MS Analysis of Peptides and Proteins. Anal. Chem., 68(1996) 31-37. 

Low W, Kang J, Di Gruccio M, Kirby D, Perrin M, et al. 2004. MALDI-MS analysis of peptides modified with photolabile arylazido groups. J Am Soc Mass Spectrom 15 1156. 

The use of MALDI-MS analysis alone to study in vivo protein modifications has several limitations, especially when it comes to identifying the specific amino acid... 

Each sample was mixed with the ionic liquid matrix (2,5-dihydroxybenzoic acid/pyridine) containing C-labelled glucose as internal standard and spotted on the target. MALDI-MS analysis generated reaction profiles by the simultaneous determination of product and substrate concentrations for each enzyme variant. The reaction profiles could be used to sort the enzyme variants into five different classes. 

An approach to multiplexing analysis was presented by Min et al. [23], who de-velopped a SAMDI-based assay scheme to screen for the activity of different kinases. In this assay scheme, peptide substrates were used that are specific for one type of kinase. A mixture of four substrates was immobilized on the SAM. After incubation with an appropriate kinase, the target surface was rinsed, thus stopping the reaction. Matrix was deposited on the surface and MALDI-MS analysis was carried out (Fig. 8.13). By monitoring the signal intensities for the substrates... 

In this pull-down assay, the enzymatic reaction is carried out completely in solution. Samples taken from the reaction mixture are then transferred to a SAM-modified MALDI target, on which the remaining substrate and the reaction product are selectively immobilized. Subsequent to the extraction of the analytes, the target is rinsed, treated with matrix, and MALDI-MS analysis is carried out. A major advantage of this assay scheme is that the inherent danger of negative influences on the reaction kinetics, which may be caused by immobilization of the substrate as in standard SAMDI-MS-based assay formats, is circumvented. Additionally, by selective extraction of the analytes of interest and removal of the other... 

Presence of the His392-T3rr415 (y, yes n, no) covalent bond was determined by MALDI-MS analysis of trypic digest mixtures. Where no indication is given, no determination was made. 

Combariza MY, SavariarEN, Vutukuri DR, Thayumanavan S, Vachet RW. Polymeric inverse micelles as selective peptide extraction agents for MALDI-MS analysis. Anal Chem 2007 79 7124-7130. 

In the last years, ILs have been applied as matrices for matrix-assisted laser desorption/ionization (MALDI) MS [42], thus expanding the use of MALDI. In Ref. 38 the suitability of alkylammonium- and alkylimidazolium salts of a-cyano-4-hydroxycinnamic acid was investigated as a MALDI matrix and at the same time as the additive of BGE. The alkylammonium salt produced better separation of phenolic compounds than the alkylimidazolium salt. The investigation suggests that it is possible to synthesize ILs suitable for electrophoretic analysis as well as for online MALDI-MS analysis. 

Mank, M., Stahl, B. and Boehm, G., 2,5-Dihydroxybenzoic acid butylamine and other ionic liquid matrixes for enhanced MALDI-MS analysis of biomolecules. Anal. Chem., 76,2938,2004. 

Basic Protocol 2 Purification of Flavonol Glycosides for MALDI-MS Analysis 11.5.2... 

This unit describes procedures for extraction, purification, and identification by MALDI-MS of fiavonol glycosides from a plant source. The extraction and purification protocols are not meant to be comprehensive, but rather to offer guidelines for sample preparation prior to a MALDI-MS analysis. The MALDI-MS technique is suggested as a complement to other analytical methods such as HPLC or NMR. Its strength lies in the ability to rapidly screen a number of samples for the presence of fiavonol glycosides, which can be identified on the basis of their molecular weights. 

Table 11.5.1 Troubleshooting Guide for MALDI-MS Analysis of Flavonol Glycosides...

The rate-limiting step of MALDI-MS analysis (Basic Protocol 3) is the sample preparation, which involves depositing matrix and sample solutions onto the probe, allowing the solvent to evaporate, and introducing the probe into the ion source. This process may require up to 10 min per sample. From this point, analysis can be carried out in less than 1 min per sample. If multiple spectra are to be collected for each sample, accordingly more time will be required. Manipulation of spectra and peak labeling can be achieved in less than 5 min. 

Cohen, S. L., and Chait, B. T. (1996). Influence of matrix solution conditions on the MALDI MS analysis of peptides and proteins. Anal. Chem. 68 31-37. 

The low volatility of ILs makes them useful as solvents working under high vacuum, and together with their more amorphous solid analogs they are convenient in matrix-assisted laser-desorption/ ionization-mass spectroscopy (MALDI-MS) analysis.103104... 

In another report, an open-access channel (i.e., no cover plate) has been used for CE separation before the MALDI-MS analysis [792]. 

One of the requirements in MALDI-MS analysis is the use of a liquid matrix. The electrowetting-on-dielectric (EWOD) method has been used to move and mix droplets containing proteins and peptides with the liquid matrix, all of which were situated at specific locations on an array of electrodes. With this method, insulin (1.75 pM), insulin chain B (2 pM), cytochrome c (1.85 pM), and myoglobin (1.45 pM) have been analyzed [518]. 

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