1. Department of Biomedical Engineering, University of Rochester, Rochester, New York 14620, United States
2. Center for Musculoskeletal Research, University of Rochester, School of Medicine and Dentistry, Rochester, New York 146421, United States
3. Departments of Biochemistry and Biophysics and of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
4. The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia 30332, United States