Mass spectrometry for direct determination of proteins in cells: applications in biotechnology and microbiology.

A number of different procedures have been developed in recent years that utilize mass spectrometry for the direct determination of proteins in complex mixtures of biological origin. Specific examples of these include the use of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) or directly combined liquid chromatography-electrospray ionization mass spectrometry (LC/ESI-MS) for rapid profiling of protein expression in bacterial and eucaryotic cells and cell-free extracts. Approaches to sample cleanup, contaminant removal, and initial separation of analytes on-line for the direct determination of proteins in cells using MALDI- and ESI-MS are discussed. Advantages of these techniques over traditional biochemical methods are highlighted, and a critical review of their utility and potential as standard tools in the biomolecular and microbiological research laboratory is presented.