When researchers perform peptide mass fingerprinting on gel slices, they typically use matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) spectrometers, such as Applied Biosystems' 4700 Proteomic Analyzer, the subject of the first review. But not all spectrometers use MALDI; others use electrospray ionization (ESI) instead. A liquid-phase technology, ESI allows researchers to couple the system to a high-performance liquid chromatography or capillary electrophoresis system to fractionate samples, instead of using gel electrophoresis for that purpose. Researchers tend to use ESI with tandem mass spectrometers, such as the LCQ™ Deca XP ion trap instrument included in Thermo Finnigan's new ProteomeX™ system, which is the subject of the second review.
MS has other applications that make it an invaluable tool for chemists, clinical researchers, environmental scientists, and forensic scientists as well. Genomic researchers often use MS to sequence DNA or to analyze single nucleotide polymorphisms (SNPs).2 But while peptides typically adopt a positive charge during ionization for MS analysis, nucleic acids usually become negatively charged, and negative ions are not easily analyzed unless the instrument is configured to do so. Micromass has now added this feature to its M@LDI line of instruments, extending those instruments' application ranges, as discussed in the third article.
1. J.M. Perkel, "Mass spectrometry applications for proteomics," The Scientist, 15:31, Aug. 20, 2001.
2. A. Adams, "Prospecting for gold in genome gulch," The Scientist, 16:36, April 15, 2002.