1. Laboratory
of Biomolecular NMR, St. Petersburg State University, St. Petersburg 199034, Russia
2. Department
of Physics, St. Petersburg State University, St. Petersburg 198504, Russia
3. Center
for Magnetic Resonance, St. Petersburg State University, St. Petersburg 198504, Russia
4. Institute
of Experimental Physics II, University of Leipzig, Linnéstr.
5, D-04103 Leipzig, Germany