1. Department of Physical Chemistry, Åbo Akademi University, Porthansgatan 3-5, FIN-20500 Turku, Finland; Chimie de la Matière Condensée, Université Pierre et Marie Curie, CNRS, 4 Place Jussieu, F-75252 Paris Cedex 05, France; and Institute of Biophysics and X-ray Structure Research, Austrian Academy of Sciences, Schmiedlstrasse 6, A-8042 Graz, Austria