Department of Computer Science and Department of Biology, Biocomputing group, University of Bologna, Bologna, Italy. vassura@cs.unibo.it|Department of Computer Science and Department of Biology, Biocomputing group, University of Bologna, Bologna, Italy. vassura@cs.unibo.it|Department of Computer Science and Department of Biology, Biocomputing group, University of Bologna, Bologna, Italy. vassura@cs.unibo.it|Department of Computer Science and Department of Biology, Biocomputing group, University of Bologna, Bologna, Italy. vassura@cs.unibo.it|Department of Computer Science and Department of Biology, Biocomputing group, University of Bologna, Bologna, Italy. vassura@cs.unibo.it|Department of Computer Science and Department of Biology, Biocomputing group, University of Bologna, Bologna, Italy. vassura@cs.unibo.it