Sample Preparation for MALDI

The quality of the protein-doped cryst s is experimentally crucial and decisive for the quality of their spectrum. Only proteins incorporated in matrix crystals jump into the gas phase. Not every matrix is suited for every protein. Which matrix delivers the best results is not predictable. You have to try things Table 7.1 shows suitable matrices. 

According to Vorm et al. (1994) and Vorm and Mann (1994), fast drying yields smaller and more evenly distributed protein-doped crystals. Hence, the protein/matrix droplets are often dried in a vacuum. Hewlett-Packard offers a a device with which you can visually track the crystallization in the vacuum. 

If the protein/peptide solution contains high concentrations of nonvolatile substances, it is advisable to wash the crystals briefly (10 seconds) in cold water. The nonvolatile substances 

Dried Drops Fast Evaporation Dissolved Nitrocellulose 

Dissolve 40 mg/ml a-cyano-4-hydroxy cinnamic acid (aC) in 50% acetonitrile, 0.1% TFA. Dissolve 40 mg/ml a-cyano-4-hydroxy cinnamic acid (aC) in acetone. Dissolve 40 mg/ml a-cyano-4-hydroxy cinnamic acid (aC) in acetone. 

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I. D. Figueroa, O. Torres, and D. H. Russell. Effects of the Water Content in the Sample Preparation for MALDI on the Mass Spectra. Anal. Chem., 70(1998) 4527-4533. 

Trimpin, S. Grimsdale, A.C. Rader, H.J. Mullen, K. Characterization of an Insoluble Poly(9,9-Diphenyl-2,7-Fluorene) by Solvent-Free Sample Preparation for MALDI-TOF-MS. Anal. Chem. 2002, 74, 3777-3782. 

Sample preparation for MALDI is relatively straightforward. The sample could be a commercially obtained protein or peptide, or a band from a dried SDS gel (section 3.2.3) or a spot from a dried 2D gel (section 3.2.5). Solutions of the sample and the matrix are made up and mixed either in a tube prior to placing onto the target plate or on the target plate itself. To obtain good spectra, it is essential to keep the salt concentrations in buffers to a minimum. Two common methods are described below. 

Table 7.2. You have a choice Three sample preparations for MALDI. ...

Sample preparation for MALDI analysis The a-cyano-4-hydroxy-cinnamic add methyl ester matrix was prepared by spotting 0.5 pi of a 1,5% solution in acetone onto the target and spotting 0.4 pi of a solution of the sample in 40% acetonitrile on top of the dried matrix thin-layer. 40% acetonitrile dissolves the surface layer of the matrix allowing for a concentrated incorporation of the analytes into the matrix surface. 

Zhukov, A., M. Schurenberg, O. Jansson, D. Areskoug, and J. Buijs. 2004. Integration of surface plasmon resonance with mass spectrometry Automated ligand fishing and sample preparation for MALDI MS using a Biacore 3000 biosensor. /. Biomol. Technol. 15 112-9. 

Ekstrom S, Wallman L, Hok D, Marko-Varga G, Laurell T (2006) Miniaturized solid-phase extraction and sample preparation for MALDI MS using a microfabricated integrated selective enrichment target. J Proteome Res 5 1071-1081... 

Sample prepared for MALDI analysis (thin tissue section washed, fixed to MALDI plate, and MALDI matrix applied, see Chapters 4, 7, 11, 16, 20, and 21 for detailed methodologies). 

MALDI-MS has extensively been reviewed [273, 276,297-300]. Matrix and sample preparation for MALDI have been discussed [300] and advances in mass spectrometry (MALDI, ESI) of polymers have recently been reviewed [268,301]. Textbooks are available [270,302]. 

Fig. 11.11. Sample preparation for MALDI. (a) Pipetting of 1 pi of sample-matrix solution onto a standard MALDI target (b) same spots after DHB has crystallized show large crystals on the rim and evenly distributed small crystals in the center, (c) cummulative effect of hydrophilic spots bright areas in circles) present on a hydrophobic surface of an Anchor-Chip target on crystallizing DHB matrix.

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