Signal Traitment and Virtual Images Production (1/2)

Identification and characterization of all proteins expressed by a genome in biological samples represent major challenges in proteomics. Today’s commonly used high throughput approaches combine two-dimensional electrophoresis (2-DE) with peptide mass fingerprinting (PMF) analysis. Although automation is often possible, a number of limitations still adversely affect the rate of protein identification and annotation in 2-DE databases: the sequential excision process of pieces of gel containing protein; the enzymatic digestion step; the interpretation of mass spectra (reliability of identifications), and the manual updating of 2-DE databases. We present a highly automated method that generates a fully annotated 2-DE map. Using a parallel process, all proteins of a 2-DE are first simultaneously digested proteolytically and electro-transferred onto a polyvinylidene difluoride (PVDF) membrane. The membrane is then directly scanned by MALDI-TOF MS. After automated protein identification from the obtained peptide mass fingerprints using PeptIdent software (http://www.expasy.ch/tools/peptident.html), a fully annotated 2-D map is created online. It is a multi-dimensional representation of a proteome, that contains interpreted PMF data in addition to protein identification results. This “MS-imaging” method represents a major step towards the development of a clinical molecular scanner.