Dr Mary-Jane Gething (Partner in the Sambrook & Tooze Partnership, our co-publishers of the Guidebooks Series) Dept of Biochemistry, Melbourne University, Parkville 3052, Australia. Tel: 00 61 3 9344 5948. Fax: 00613 9347 9109. Email: gething@ariel.ucs.unimelb.edu.au