1. *Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM 87501;
2. Los Alamos National Laboratory, MSB285, Los Alamos, NM 87545;
3. Bauer Laboratory, Harvard University, 7 Divinity Avenue, Cambridge, MA 02138; and
4. Department of Systems Biology, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115