W0192

Ab Initio Methods for Large Peptides and Small Proteins. George M. Sheldrick, University of Goettingen, Germany

For more than a decade, classical direct methods proved very effective at solving structures with 100 or less unique atoms, but rapidly ran out of steam above 200 atoms. This barrier was first convincingly broken by the 'Shake and Bake' approach of Weeks, Miller, Hauptman et al. in 1993. The new program SHELXD, also known as 'half-baked', was inspired by Shake and Bake but differes in many important details. It has been able to solve several previously unsolved equal-atom structures with more than 500 unique atoms; the largest structure solved so far contained 2024 protein atoms (30kD) but was facilitated by the presence of 8 iron atoms and synchrotron data measured to 1.2 Å. However the program needs a few more years of mutations and Darwinian selection before it can be released.