The off-line strong cation exchange chromatography and online nano-LC ESI QqTOF MS were performed according to the protocol described by Wei et al. . The ProteinPilot software calculates a percent confidence, which reflects the probability that the hit is a false positive, so that at the 95% confidence level there is a false-positive identification rate of 5%. To be identified as being significantly differently expressed, a protein had to be quantified in at least three spectra with a p-value