Detection and identification of low-mass peptides and proteins from solvent suspensions of Escherichia coli by high performance liquid chromatography fractionation and matrix-assisted laser desorption/ionization mass spectrometry.

The application of high performance liquid chromatography (HPLC) to separate components in solvent suspension of Escherichia coli followed by off-line matrix-assisted laser desorption/ionization (MALDI) analysis of collected fractions results in the detection of over 300 peaks in the 2000-19,000 Da mass range, an order of magnitude increase in the number of components observed when compared with direct MALDI analysis of the entire solvent suspension. Mass measurements of these separated components using a time-lag focusing MALDI instrument are reported. MALDI analysis of the proteolytic digests of several collected fractions facilitates the identification of three components as specific proteins expected to be present in E. coli. The methodologies reported here should be very useful in searching for unique biomarkers for bacterial discrimination.