1. Department of Chemistry, Stanford University, Stanford, California 94305, United States
2. Department of Physics, Experimental Molecular Biophysics, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany
3. Research Building SupraFAB, Altensteinstreet 23a, 14195 Berlin, Germany
4. Stanford Synchrotron Radiation Lightsource, Menlo Park, California 94025, United States
5. Department of Chemistry, Scripps Research, La Jolla, California 92037, United States
6. Department of Chemistry-BMC, Uppsala University, 752 37 Uppsala, Sweden