PSI-BLAST/PHI-BLAST

BLAST stands for Basic Local Alignment Search Tool.The emphasis of this tool is to find regions of sequence similarity, which will yield functional and evolutionary clues about the structure and function of your novel sequence. Position specific iterative BLAST (PSI-BLAST) refers to a feature of BLAST 2.0 in which a profile is automatically constructed from the first set of BLAST alignments. PSI-BLAST is similar to NCBI-BLAST2 except that it uses position-specific scoring matrices derived during the search, this tool is used to detect distant evolutionary relationships. Pattern Hit Initiated BLAST (PHI-BLAST) treats two occurrence of the same pattern within the query sequence as two independent sequences. This can be seen in a number of ways, from the statistical analysis at the end of the search results. This tool is only available for database protein searches.