Searching over a domain critical function: Recasting the phase problem of X-ray crystallography

This novel technique provides researchers with a powerful and practical tool to solve the phase problem in X-ray crystallography. The authors present a formulation of the phase problem in terms of a minimal function of phases and a new heuristic search algorithm called shake-and-bake for solving this minimal function. This algorithm is based on a hill climbing approach and a back-and-forth transformation between related spaces to utilize implicit chemical information. Since the shake-and-bake algorithm is computationally intensive, several parallel implementations have been explored. These implementations include master/slave multiple instruction/multiple data (MIMD) implementations on an Intel iPSC/860 Hypercube and a Thinking Machines Corporation CM-5. The experimental results indicate that this method is effective on structures, including three previously unknown structures in a variety of space groups