Structural Biology Department and Public Policy Program, Stanford University, Stanford, United States of America.|Institute for Computational and Mathematical Engineering, Stanford University, Stanford, United States of America.|Department of Microbiology and Immunology, Baxter Laboratory, Stanford University, Stanford, United States of America.|Statistics Department, Stanford University, Stanford, United States of America.|Statistics Department, Stanford University, Stanford, United States of America.|Department of Microbiology and Immunology, Baxter Laboratory, Stanford University, Stanford, United States of America.|Statistics Department, Stanford University, Stanford, United States of America.