Mass spectrometry analysis was performed in accordance with the procedure described in our previous report . In brief, mass spectra were obtained using a MALDI-TOF MS/MS analyzer (ABI PLUS 4800, Applied Biosystems, Foster City, CA). One μl of each sample was mixed with 1 μl matrix solution [1 μg/μl α-cyano-4-hydroxycinnamic acid (CHCA, Wako Pure Chemical Industries Ltd.) in 50% (v/v) acetonitrile and 0.3% (v/v) trifluoroacetic acid]. Analyte and matrix were spotted onto a stainless steel MALDI target plate and dried under ambient conditions. The peptides were analyzed using a MALDI-TOF MS/MS analyzer, and the authors searched the database with the Mascot search engine (http://www.matrixscience.com; Matrix Science, Boston, MA) using a Mascot MS/MS ion search through NCBInr databases. Proteins were considered as identified by MALDI-TOF MS if they had Mascot scores of 60 or higher (P < 0.05).