]> Pattern Hit Initiated BLAST. Query an amino acid (protein) sequence against a library of amino acid (protein) sequences. "PHI-BLAST expects as input a protein query sequence and a pattern contained in that sequence. PHI-BLAST searches the specified database for other protein sequences that also contain the input pattern and have significant similarity to the query sequence in the vicinity of the pattern occurrences." Source: http://www.ncbi.nlm.nih.gov/Education/BLASTinfo/Post_Blast.html.