1. Institute of Molecular Biology, Bulgarian Academy of Sciences, Acad. G. Bonchev Str.,
bl. 21, Sofia 1113, Bulgaria
2. Department of Biosciences and
Nutrition, Center for Biosciences, Karolinska Institutet, S-141 83 Huddinge, Sweden
3. 51 Natal Road, Cambridge CB1 3NY,
U.K.