[1] Goethe Univ Frankfurt, Inst Organ Chem & Chem Biol, Ctr Biomol Magnet Resonance BMRZ, D-60438 Frankfurt, Germany
[2] Max Planck Inst Biophys, Dept Biol Struct, D-60438 Frankfurt, Germany
[3] Goethe Univ Frankfurt, Inst Biophys Chem, Ctr Biomol Magnet Resonance BMRZ, D-60438 Frankfurt, Germany