Matrix‐Assisted Laser Desorption/Ionization Mass Spectrometry in Peptide and Protein Analysis

Abstract

Matrix‐assisted laser desorption/ionization mass spectrometry (MALDIMS), first introduced in 1988 by Hillenkamp and Karas, has become a widespread analytical tool for peptides, proteins and most other biomolecules. In MALDI (matrix‐assisted laser desorption/ionization) analysis, the analyte is first co‐crystallized with a large molar excess of a matrix compound, usually an ultraviolet (UV)‐absorbing weak organic acid, after which laser radiation of this analyte–matrix mixture results in the vaporization of the matrix which carries the analyte with it. The matrix therefore plays a key role by strongly absorbing the laser light energy and causing, indirectly, the analyte to vaporize. The matrix also serves as a proton donor and receptor, acting to ionize the analyte in both positive and negative ionization modes, respectively. The efficient and directed energy transfer during a matrix‐assisted laser‐induced desorption event provides high ion yields of the intact analyte and allows for the measurement of compounds with high accuracy and subpicomole sensitivity. The ability to generate such accurate information can be extremely useful for protein identification and characterization. For example, a protein can often be unambiguously identified by the accurate mass analysis of its constituent peptides (produced by either chemical or enzymatic treatment of the sample). This article discusses basic MALDI concepts and instrumentation and focuses on applications in the field of peptides and proteins, specifically on the utility of MALDI in protein identification, protein structural studies, and as a clinical assay.

Anti-influenza Activity of a Bacillus subtilis Probiotic Strain

“…The molecular mass and the amino acid sequence of the purified peptide was determined with MALDI-TOF MS (Ultraflex II, Bruker, Germany) as described elsewhere (40). Spectra were acquired using the instrument in reflectron mode and calibrated using a standard peptide mixture.…”

“…Sample preparation for matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS) was performed using the dried-droplet method according to a published protocol (40). Briefly, 1 l of the sample was pipetted to the sample plate, mixed with 0.3 l of matrix, and air dried.…”

Special application of matrix-assisted laser desorption ionization time-of-flight mass spectrometry in clinical microbiological diagnostics

“…A MALDImódszer lényege, hogy a vizsgált minta molekuláinak ionizációja egy segédanyag, a mátrix, például alfa-ciano-4-hidroxi-fahéjsav vagy dihidroxi-benzoesav segítségé-vel történik meg, amely képes elnyelni az ionizációhoz használt lézer energiáját [1,2,3]. Az analit a mátrix kis molekuláiba ágyazódik, amelyek a lézer energiáját átad-ják az analit makromolekuláinak [2]. A folyamat közben a makromolekula-mátrix komplexek a vizsgálati mintá-ból felszabadulnak (deszorpció), majd a keletkező molekulaionokat nagyvákuumban egy gyorsítófeszültség juttatja az analizátorba.…”

Two-Dimensional Gel Electrophoresis and Mass Spectrometry in Studies of Nanoparticle-Protein Interactions

“…The far most commonly used matrix for peptide mass fingerprinting is CHCA, which is recommended for peptides with mass ions below 2500 Da (Beavis et al, 1992). Alternative matrices also used are sinapinic acid, mostly for masses higher than 25 kDa (Lewis et al, 2000) and DHB, originally suggested for glyco-or phosphopepides that are difficult to ionize (Strupat et al, 1991), but later also proven useful for silver stained proteins (Ghafouri et al, 2007). As illustrated in figure 11, CHCA and DHB have very different crystal structures on the target plate.…”