School of Biological Sciences, The University of Manchester, 2.205 Stopford Building, Oxford Road, Manchester M13 9PT, , UK1
ZMBH, University of Heidelberg, D69120 , Germany2
Author for correspondence: Erich Bornberg-Bauer. Tel: +44 161 275 7396. Fax: +44 161 275 5082. e-mail: ebb{at}bioinf.man.ac.uk