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Basic matrices in the analysis of non-covalent complexes by matrix-assisted laser desorption/ionization mass spectrometry

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Author: Jespersen, S. · Niessen, W.M.A. · Tjaden, U.R. · Greef, J. van der
Type:article
Date:1998
Institution: Centraal Instituut voor Voedingsonderzoek TNO
Source:Journal of Mass Spectrometry, 11, 33, 1088-1093
Identifier: 234682
Keywords: Nutrition · Basic matrices · Complex formation · Ionization mass spectrometry · Matrix-assisted laser desorption · Non-covalent interactions · 4 nitroaniline · Cinnamic acid derivative · Gentisic acid · Glutathione transferase · Hemoglobin · Nicotinic acid derivative · Picolinic acid derivative · Protein · Pyridine derivative · Streptavidin · Complex formation · Mass spectrometry · Ph · Priority journal · Chymotrypsinogen · Glutathione Transferase · Hemoglobins · Humans · Hydrogen-Ion Concentration · Indicators and Reagents · Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization · Streptavidin

Abstract

A number of potential matrix candidates were investigated with regard to the importance of the pH in the matrix-assisted laser desorption/ionization mass spectrometry (MALDI/MS) analysis of non-covalently bound protein complexes. The matrices examined were 2,5-dihydroxybenzoic acid (DHB), 4-hydroxy-α-cyanocinnamic acid (HCCA), 2-aminonicotinic acid (ANA), 4-nitroaniline (NA), 2-amino-4-methyl-5-nitropyridine (AMNP) and 3-hydroxypicolinic acid (HPA). In solution these matrix compounds permitted the preparation of MALDI samples at pH in the range 2-7. Among the matrices tested, complex formation, by specific non-covalent interactions, could only be observed when HPA (pH 3.8) was used as the matrix for the MALDI analysis. Under these conditions, specific non-covalent complex formation of recombinant streptavidin and glutathione-S-transferases were observed but not for human hemoglobin. The MALDI spectra obtained with the neutral compounds ANA (pH 4.4), NA (pH 6.4) and AMNP (pH 7.1) as matrices contain only peaks of the subunit with no signal of the non-covalent bound complexes present. Considering the results obtained in this study with basic and acidified matrix materials, there does not appear to be a strong correlation between the pH of the matrix solution and the utility of a matrix for the analysis of non-covalently bound complexes.