The AACompIdent tool can identify proteins by their AA composition. The program matches the percent empirically measured AA composition of an unknown protein against the theoretical percent AA compositions of proteins in the Swiss-Prot and/or TrEMBL databases. A score, which represents the degree of difference between the composition of the unknown protein and a protein in the database, is calculated for each database entry by the sum of the squared difference between the percent AA composition for all amino acids of the unknown protein and the database entry. All proteins in the database are then ranked according to their score, from lowest (best match) to highest (worst match). Estimated protein pI and MW, as well as species and keyword of interest can also be used in the identification procedure.
This tool is not easy to use due to the amount of prior knowledge the user needs before they can make use of the tool.