  Every day tens of thousands of sequence searches and sequence alignment
queries are submitted to webservers. The capitalized word "BLAST" become a
verb, describing the act of performing sequence search and alignment. However,
if one needs to search for sequences that contain, for example, two hydrophobic
and three polar residues at five given positions, the query formation on the
most frequently used webservers will be difficult. Some servers support the
formation of queries with regular expressions, but most of the users are
unfamiliar with their syntax. Here we present an intuitive, easily applicable
webserver, the Protein Sequence Analysis server, that allows the formation of
multiple choice queries by simply drawing the residues to their positions; if
more than one residue are drawn to the same position, then they will be nicely
stacked on the user interface, indicating the multiple choice at he given
position. This computer-game like interface is natural and intuitive, and the
coloring of the residues makes possible to form queries requiring not just
certain amino acids in the given positions, but also small nonpolar, negatively
charged, hydrophobic, positively charged, or polar ones. The webserver is
available at http://psa.pitgroup.org.
