I would like to acknowledge the following people for their assistance during the period of study: Dr Z. Dauter (EMBL, Hamburg) for helpful discussions and encouragement, Dr G. Davies (University of York) for his encouragement, Eleanor Dodson (University of York) for her helpful comments concerning data evaluation, Dr. C. Hermes, Dr. V. Lamzin, Dr. H.-F. Nolting and Dr. M. Koch (EMBL, Hamburg) for helpful discussions Dr. P.W. Loeffen (ESRF, Grenoble) for his friendship and encouragement and finally Howard Terry, Sandra McLaughlin (EMBL, Hamburg) and Dr. Kate Poole (MPI für Medizinische Forschung, Heidelberg) for their support and friendship.
I would also like to thank the European Molecular Biology Laboratory for financial support.
Finally, I would especially like to thank my supervisors Dr. R.F. Pettifer (University of Warwick) and Dr. K.S. Wilson (EMBL, Hamburg) for their patience and guidance throughout my time in Hamburg.
I hereby declare that the work contained in this thesis is my own except where specifically cited or referenced otherwise.