Department of Computer Science, Tufts University, 155 College Ave, Medford, MA 02155, USA. hwick@cs.tufts.edu.|Department of Computer Science, Tufts University, 155 College Ave, Medford, MA 02155, USA. hwick@cs.tufts.edu.|Department of Computer Science, Tufts University, 155 College Ave, Medford, MA 02155, USA. hwick@cs.tufts.edu.|Department of Computer Science, Tufts University, 155 College Ave, Medford, MA 02155, USA. hwick@cs.tufts.edu.|Institute of Biophysical Chemistry, Center for Biomolecular Magnetic Resonance, and Frankfurt Institute of Advanced Studies, Goethe University Frankfurt am Main, Max-von-Laue-Str, 9, 60438 Frankfurt am Main, Germany. guentert@em.uni-frankfurt.de.