Solving the phase problem is the crucial step in obtaining a crystal structure. For macromolecular crystallographers it may also be the most difficult and time-consuming step. The traditional methods used are Multiple Isomorphous Replacement and Molecular Replacement. This meeting covered aspects of some of the newer methods that are in use and some potential methods for the future.
Multiwavelength Anomalous Dispersion (MAD) was covered in some detail. In the first session, John Helliwell described the basic principles of anomalous scattering, Andy Thompson explained the beamline requirements of MAD and Janet Smith introduced us to MAD on proteins. This introduction to the method was followed by several case studies (Valerie Biou, Mark Peterson, Ian Glover and Harry Powell). Eric de la Fortelle described the use of the program SHARP for MAD phasing and Phil Evans talked about multiple wavelength simultaneous scaling. Rather more unusual uses of anomalous diffraction were described by Bill Shepard and Edgar Weckert.
The second day of the meeting was more theoretical. An introduction to direct methods was given by Zbyszek Dauter followed by two talks on ab-initio phasing of proteins (and the limitations of the method) by the Shake-and Bake method (Charles Weeks) and using ShelX (George Sheldrick). Gerard Bricogne covered maximum entropy techniques and Abraham Szoke introduced to us the application of holographic methods to crystallography. Case studies of using wARP to improve your phasing were presented by Anastassis Perrakis. The final presentations were on low resolution phasing strategies, based on solution scattering (Dimitri Svergun) or crystallographic images (Alexandre Urzhumtsev). Kevin Cowtan summarised what we had learnt in the meeting and led the discussion.
The meeting, this year, was held at York University for the first time. There were 418 participants in total, including 111 participants from Europe, 16 from the Americas and 2 from Japan. Bursaries, covering the cost of registration and accomodation were given to 232 young scientists, and an additional contribution was made to the travel costs of 23 young scientists from outside the UK. The speakers comprised 8 from the UK, 8 from elsewhere in Europe and 3 from the USA.
The meeting was organised and supported by the BBSRC Collaborative Computational Project in Protein Crystallography (CCP4). We thank the invited speakers for sharing their expertise with us and for the contributions to this booklet. We are greatful to Daresbury Laboratory for providing organisational support, with particular thanks to Diane Travers, Val Matthews and the rest of the SAS team who ensured that the meeting ran to plan.