1. Institute for Cancer Research, Department of Biochemistry, The Norwegian Radium Hospital, Montebello, 0310 Oslo, Norway
2. University of Colorado at Boulder, Department of Molecular, Cellular and Developmental Biology, Campus Box 347, Boulder, CO 80309-0347, U.S.A.
3. Institute of Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
4. Central Laboratory, Blood Transfusion Service, Swiss Red Cross, Wankdorfstrasse 10, 3000 Bern 22, Switzerland