# RPS-BLAST at the Blocks Server

RPS-BLAST: Reversed Position Specific Blast RPS-BLAST is one of the BLAST series of searching programs from NCBI. It reverses the popular PSI-BLAST search by comparing a protein query with a database of PSI-BLAST checkpoint files made from multiple alignments of protein families. Here the checkpoint files are made from the Blocks and Prints alignments, and are the same files searched with the similar IMPALA searching program also from NCBI. RPS-BLAST should be somewhat faster than IMPALA since it uses the BLAST heuristics while IMPALA does full dynamic programming. RPS-BLAST output closely mimics output of BLASTP family programs and should be compatible with SEALS BLAST parsers. Send suggestions, comments, complaints to blast-help@ncbi.nlm.nih.gov