1. Microsoft Research—University of Trento Centre for Computational and Systems Biology (CoSBi), Piazza Manci 17, Povo (Trento) 38100, Italy
2. Microsoft Research Cambridge, 7 J J Thomson Avenue, Cambridge CB3 0FB, UK
3. Systems Biology Program, College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QF, UK