1. Uppsala Center for Computational Chemistry, Department of Cell and Molecular Biology, Uppsala University, Husargatan 3, Box
596, SE-75124 Uppsala, Sweden
2. Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden
3. Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron, DE-22607 Hamburg, Germany
4. Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States