Biocomputing Group, Dept. of Biology University of Bologna, via Irnerio 42, 40126 Bologna, Italy. andrea@biocomp.unibo.it|Biocomputing Group, Dept. of Biology University of Bologna, via Irnerio 42, 40126 Bologna, Italy. andrea@biocomp.unibo.it|Biocomputing Group, Dept. of Biology University of Bologna, via Irnerio 42, 40126 Bologna, Italy. andrea@biocomp.unibo.it|Biocomputing Group, Dept. of Biology University of Bologna, via Irnerio 42, 40126 Bologna, Italy. andrea@biocomp.unibo.it