Pooled fractions were concentrated to 500 μl using nanosep 10 k cutoff centrifugal device (Pall Life Sciences, MI, USA). In preparation for the MTT assay, the resultant fractions were diluted to 2 ml volumes with Sorenson’s buffer. Mass spectrometry (MS) Trypsin digests on excised gel bands were performed in a solution of 20 mM ammonium bicarbonate containing 0.5 μg trypsin (Promega corporation, Madison, WI, USA) and then LY294002 clinical trial analysed directly by LCMS as outlined below. Trypsin digests on the pool B fraction directly
were performed in a solution of 20 mM ammonium bicarbonate containing 10 μg trypsin (Promega corporation) and then the resultant digested MAPK inhibitor peptides were fractionated by 12 salt plug elutions ranging from 2 mM to 500 mM NaCl from a SCX TopTip (Glygen, Columbia, MD, USA) according to manufacturer’s instruction. Both digest protocols were incubated at 37°C for 12 hours. Tryptic digests were analysed by LC-MS/MS using the HCT ULTRA ion trap mass spectrometer (Bruker Daltonics, Bremen, Germany) coupled online with a 1200 series capillary HPLC (Agilent technologies). Samples were injected onto
a zorbax 300SB reversed phase column with buffer A (5% acetonitrile 0.1% formic acid) at a flow rate of 10 μl/minute. The peptides were eluted over a 30-minute gradient to 55% B (90% acetonitrile 0.1% formic acid). The eluant was nebulised and ionised using the Bruker electrospray source using the low flow electrospray needle with a capillary voltage of 4000 V dry gas at 300°C, flow AZD1152 clinical trial rate of 8 l/minute and nebuliser gas pressure at 1500 mbar. Peptides Chorioepithelioma were selected for MSMS analysis in autoMSn mode with smart parameter settings selected and active exclusion released after 1 minute. Data from LCMSMS runs were processed using Data Analysis 3.4 (Bruker Daltonics) and were exported in Mascot generic file format (*.mgf) and searched against an in-house database comprised of C. jejuni FASTA format genomes downloaded from the National Center for Biotechnology
Information (NCBI) FTP site using the MASCOT search engine (version 2.1, Matrix Science Inc., London, United Kingdom) using MUDPIT scoring. The mgf files from the salt plug elutions were combined into a single mgf file. The following search parameters were used: missed cleavages, 1; peptide mass tolerance, ± 0.4 Da; peptide fragment tolerance, ± 0.2 Da; peptide charge, 2+ and 3+; fixed modifications, carbamidomethyl; variable modification, oxidation (Met). Stability of cytotoxin to protease digestion The cytotoxin in pool B fraction was treated with trypsin (125 μg/ml) (Sigma, St. Louis, MO, USA) for 4 h at 37°C. The trypsin was inactivated by the addition of 125 μg/ml soybean trypsin inhibitor (Sigma). One hundred microliters of treated pool B fractions at a concentration of 2 μg/ml were added to a CHO cell monolayer in a microtitre plate. The MTT assay  for cytotoxicity was performed after a 24 h incubation period.