1. Department of Computer and Information Science, University of Delaware, Newark, DE 19716, USA
2. Swiss Institute of Bioinformatics, Centre Medical Universitaire, Geneva, Switzerland
3. Center for Bioinformatics and Computational Biology, University of Delaware, Newark, DE 19716, USA
4. Protein Information Resource, University of Delaware, Newark, DE 19716 and Georgetown University, Washington, DC 20007, USA