[1] Univ Dusseldorf, Inst Biochem & Mol Biol 2, Fak Med, D-40255 Dusseldorf, Germany
[2] Forschungszentrum Julich, Inst Strukturbiochem ICS 6, D-52425 Julich, Germany
[3] Univ Dusseldorf, Inst Phys Biol, Math Nat Wissensch Fak, D-40255 Dusseldorf, Germany
[4] Univ Virginia, Dept Mol Physiol & Biol Phys, Charlottesville, VA 22908 USA