Department of Cell Biology and Physiology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, United States of America.|Wallace H. Coulter Department of Biomedical Engineering at Georgia Institute of Technology and Emory University, Atlanta, Georgia, United States of America.|Department of Mathematics, University of South Carolina, Columbia, South Carolina, United States of America.|Department of Mathematics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America.|Department of Mathematics, University of South Carolina, Columbia, South Carolina, United States of America.|Department of Mathematics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America.|Department of Cell Biology and Physiology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, United States of America.|Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, United States of America.|Department of Mathematics, University of South Carolina, Columbia, South Carolina, United States of America.|Department of Cell Biology and Physiology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, United States of America.|Department of Mathematics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America.