The reduced aminoacid alphabets has been obtained from the references bellow:
Li T, Fan K, Wang J, Wang W. Reduction of protein sequence
complexity by residue grouping. Protein Eng 2003; 5:323-330.
PubMed
Murphy LR, Wallqvist A, Levy RM. Simplified amino acid alphabets
for protein fold recognition and implications for folding.
Protein Eng 2000; 13:149-152.
PubMed
Pommié C, Levadoux S, Sabatier R, Lefranc G & Lefranc MP.
IMGT standardized criteria for statistical analysis of immunoglobulin
V-REGION amino acid properties. Journal of Molecular Recognition 2004; 17:17-32.
PubMed
Spitzer M, Fuellen G, Cullen P, Lorkowski S.
VisCoSe: visualization and comparison of consensus sequences.
Bioinformatics 2004; 20:433-435.
PubMed,
Web
Wang J, Wang W. A computational approach to simplifying the protein
folding alphabet. Nat Struct Biol 1999; 11:1033-1038. PubMed
The script has been created entirely with PHP scripting language, and source code is available at BioPHP.org