To make the feature-encoded sequence to be a vector with a fixed number of dimensions, three properties of a sequence was used: composition (C), transition (T), and distribution (D). C represents the global composition of each letter in the sequence; T, the frequency of a code letter changing from one to another; D, the distribution pattern of the code letters along the sequence, measuring the percentage of the sequence length within which the first, 25%, 50%, 75%, and 100% of the amino acids of each code letter is located. Take the above hydrophobic property sequence as an example: its C feature is 5/15 = 33.3% for all of P, H, and N, while the T feature is 2/10 = 20%, 3/10 = 30% and 5/10 = 50% for the changes between H and P, N and H, N and P, respectively. The measurement of feature D is a little more complicated. For the letter H, the first, 25%, 50%, 75% and 100% of Hs in the sequence is located at the position of 2, 5, 6, 14, and 15. Thus its D feature is ( , with a total of 21 components. Likewise, for the sequences encoded by the other four biochemical properties, each is also corresponding to 21 components. But for the sequence encoded by the solvent accessibility with only two states (''buried'' or ''exposed to solvent''), the encoded sequence is corresponding to only 14 components. Finally, by adding the 20 components of AAC [87] into the vector concerned, the total number of components thus obtained for a given protein is 5|21z20z14~139; i.e., the protein can be formulated as a 139-D vector given by