1. Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
2. Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
3. National Center for Macromolecular Imaging, Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA.
4. School of Molecular Sciences, Arizona State University, Tempe, AZ 85287, USA.
5. Biodesign Center for Molecular Design and Biomimetics (at the Biodesign Institute) at Arizona State University, Tempe, AZ 85287, USA.