PSIC: profile extraction from sequence alignments with position-specific counts of independent observations

1European Molecular Biology Laboratory, Meyerhofstrasse1, Postfach 10.2209, D-69012 Heidelberg, 2Max-Delbruck-Centrum fur Molekulare Medizin, Robert-Rossle-Strasse 10, D-13122 Berlin-Buch, Germany, 3V.A. Engelhardt Institut of Molecular Biology, Russian Academy of Sciences, Vavilov Street 32, 117984 Moscow, 5Moscow Institute of Physics and Technology, Institutsky per. 9, Dolgoprudny, Moscow Region and 6Institute of Control Sciences, Russian Academy of Sciences, Profsoyuznaya Street 65, 117806 Moscow, Russia