1. Section de Bioénergétique, Département de Biologie Cellulaire et Moléculaire, CNRS URA 2096, CEA Saclay, F-91191 Gif-sur-Yvette, France, Grenoble High Magnetic Field Laboratory, 25 Avenue de Martyrs, B.P. 166, F-38042 Grenoble, France, Department of Molecular Physics, Wageningen Agricultural University, NL-6703 Wageningen, The Netherlands, and Fachbereich Physik, Freie Universität Berlin, D-14195 Berlin, Germany