Department of Biochemistry, Stanford University School of Medicine, 466 Gates Computer Science, Stanford, CA 94305, USA. kamesh@cmgm.stanford.edu|Department of Biochemistry, Stanford University School of Medicine, 466 Gates Computer Science, Stanford, CA 94305, USA. kamesh@cmgm.stanford.edu|Department of Biochemistry, Stanford University School of Medicine, 466 Gates Computer Science, Stanford, CA 94305, USA. kamesh@cmgm.stanford.edu