1. Contribution from the Department of Biochemistry, Center for Chemistry and Chemical Engineering, Lund University, Box 124, S-22100 Lund, Sweden, Department of Physical Chemistry, Uppsala University, Sweden, Laboratoire de Chimie Inorganique, URA CNRS 420, Université de Paris-Sud, F-91405 Orsay, France, Section de Bioenergetique, URA CNRS 2096, CEA Saclay, F-91191 Gif-sur-Yvette, France, and Department of Organic Chemistry, Royal Institute of Technology KTH, S-10044 Stockholm, Sweden