1. Department of Biophysics, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218-2685, Department of Materials Science and Engineering, Biophysics Program, IPST, University of Maryland, College Park, Maryland 20472, National Institute of Standards and Technology, Center for Neutron Research, Gaithersburg, Maryland 20899, and Department of Polymer Science, University of Akron, Akron, Ohio 44325-3090