Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America.|Department of Biology, University of Nebraska-Omaha, Omaha, Nebraska, United States of America.|Department of Biology, University of Nebraska-Omaha, Omaha, Nebraska, United States of America.|Department of Biology, University of Nebraska-Omaha, Omaha, Nebraska, United States of America.|Department of Biology, University of Nebraska-Omaha, Omaha, Nebraska, United States of America.|Department of Mathematics, University of Nebraska-Omaha, Omaha, Nebraska, United States of America.