Department of Biosciences, Rice University, Houston, Texas, United States of America.|Department of Mathematics, University of Houston, Houston, Texas, United States of America.|Department of Biosciences, Rice University, Houston, Texas, United States of America.|Department of Mathematics, University of Houston, Houston, Texas, United States of America.|Department of Mathematics, University of Houston, Houston, Texas, United States of America, Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America.|Department of Biosciences, Rice University, Houston, Texas, United States of America, Institute of Biosciences and Bioengineering, Rice University, Houston, Texas, United States of America.