Strain 870 had caused fatal septicaemia in a 34 year-old man and strain 901, meningitis in a 1 year-old infant. The RIFS 1958 invasive strain was responsible for septicaemia in an infant aged 2, and since the absence of mutations in the Selleckchem JIB04 rpoB gene, was chosen as control strain. Bacterial protein extraction was performed according to the protocol previously described , with some modifications. In particular, the confluent bacterial growth was scraped from the plates and washed twice with PBS, suspended in 5 ml of lysis buffer (500 mM NaCl, 10 mM EDTA, 50 mM Tris pH 8.0) containing 0.3 mg/ml protease inhibitor
(CompleteMini, Roche Diagnostic, Mannheim, Germany) and 150U DNase I (Roche Diagnostic). The sample analysed by 2-DE approach corresponds to the cytosolic fraction, in which most of the proteins involved in the metabolic pathway and in essential biological processes have been described in bacteria. Two-dimensional gel electrophoresis Before electrophoresis an aliquot of protein extract corresponding to 350 μg of each sample was precipitated by adding nine volumes of cold-ethanol
click here and keeping at -20°C overnight. Samples were centrifuged at 14. 000 g for 15 min at 4°C and pellets were dried and then dissolved in 185 μl of a rehydration buffer containing 7 M urea, 2 M thiourea, 2% w/v CHAPS, 50 mM DTT, 0.2% v/v Bio-Lytes™pH range 3-10. Each sample was loaded on an 11-cm precast Immobiline strip with a linear pH 4-7 gradient and three replica maps were performed. First- and second-dimension electrophoresis, and image analysis were carried out as already described by Mignogna et al. . Protein identification Spots selected according to the procedure previously described , were manually excised from gels and digested with trypsin. Digestion was performed at 37°C overnight.
Briefly, after several destaining steps using 50 mM ammonium bicarbonate (15 min), 50% acetonitrile in 50 mM ammonium bicarbonate (10 min) and 100% acetonitrile (15 min), subsequently, Tau-protein kinase about 100 ng of trypsin (Trypsin Gold, Mass Spectrometry Grade, Promega, Madison, WI, USA), solubilised in 10 μl of a 25 mM ammonium bicarbonate digestion buffer, were added to vacuum-dried gel. An aliquot (1 μl) of each mixture peptide was mixed with the same volume of α-cyano-4-hydroxy-trans-cinnamic acid matrix solution (5 mg/ml) in 70% acetonitrile containing 0.1% TFA (v/v) for MRT67307 purchase MALDI-ToF analysis, performed in a Voyager-DE STR instrument (Applied Biosystems, Framingham, MA) equipped with a 337 nm nitrogen laser and operating in reflector mode. Mass data were obtained by accumulating several spectra from laser shots with an accelerating voltage of 20 kV. Two tryptic autolytic peptides were used for the internal calibration (m/z 842.5100 and 2807.3145). Identification by peptide mass fingerprint (PMF), was performed using the Mascot search engine version 2.2  against NCBlnr database (10386837 sequences).