  Unsupervised word segmentation methods were applied to analyze the protein
sequence. Protein sequences, such as 'MTMDKSELVQKA...', were used as input to
these methods. Segmented 'protein word' sequences, such as 'MTM DKSE LVQKA',
were then obtained. We compare the 'protein words' produced by unsupervised
segmentation and the protein secondary structure segmentation. An interesting
finding is that the unsupervised word segmentation is more efficient than
secondary structure segmentation in expressing information. Our experiment also
suggests there may be some 'protein ruins' in current noncoding regions.
