Fraction Fa-1 was subjected to tandem MS (MALDI TOF/TOF MS/MS) analysis. The first-order MS of Fa-1 was found to contain several peaks (data not shown),indicating that Fa-1 was a mixture. Further, the
second-order mass spectrometric analysis for an individual peak was performed. Figure 2a shows the
second-order MS of a peak with an m/z value of 849.3208. According to mass spectrometric data, the
peptide’s amino acid sequence was identified as SerAsn-Leu-Cys-Arg-Pro-Cys-Gly by searching the database NCBInr via the Mascot Server. This peptide consisted of eight amino acids with a mass of 848.8 Da and a predicated pI value of 8.23.Through a database search (http://blast.ncbi.nlm.
nih.gov/) using this peptide’s amino acid sequence,several proteins annotated as feather keratin-1 were retrieved from the database (Fig. 2b). This indicated that the peptide was derived from feather keratin and