1. Biological Physics Group, Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213, USA
2. ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire, OX11 0QX, UK
3. University of Southern Denmark, Dept. Physics, Chemistry & Pharmacy, PhyLife, Campusvej 55, Odense M5230, Denmark
4. Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
5. Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, PA 15261, USA