1. Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
2. Division of Engineering and Applied Science, California Institute of Technology, Pasadena, California 91125, USA
3. Department of Anatomy and Structural Biology, and Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, New York 10461, USA
4. Medicum, Faculty of Medicine, University of Helsinki, Helsinki, Finland