1. Division of Molecular Structure, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, U.K.
2. Chemistry Department, M.V.Lomonosov Moscow State University, Moscow 119991, Russia
3. Center for Magnetic Tomography & Spectroscopy, Faculty of Fundamental Medicine, M.V.Lomonosov Moscow State University, Moscow 119991, Russia