Center for Bioinformatics and Computational Biology and the Department of Computer Science, University of Maryland, College Park, Maryland, United States of America.|Department of Electrical Engineering and Computer Science and the Center for Computational Biology, University of California, Berkeley, Berkeley, California, United States of America.|Center for Bioinformatics and Computational Biology and the Department of Computer Science, University of Maryland, College Park, Maryland, United States of America.|Center for Bioinformatics and Computational Biology and the Department of Computer Science, University of Maryland, College Park, Maryland, United States of America.