1. Department
of Biosciences, Section for Biochemistry and Molecular Biology, University of Oslo, P.O.
Box 1066, Blindern, 0316 Oslo, Norway
2. Swedish
NMR Centre, University of Gothenburg, P.O. Box 465, 405 30 Gothenburg, Sweden
3. Department
of Biomedical and Biotechnological Sciences (BIOMETEC), Microbiology
Section, University of Catania, via Androne 81, 95124 Catania, Italy