Crambin Crystals at Ultra High Resolution of 0.67 Å Resolution and 100K. Martha M. Teeter¹, Victor S. Lamzin², Zbigniew Dauter³, and Keith S. Wilson³, ¹Department of Chemistry, Boston College, Chestnut Hill, MA 02167, ²EMBL, c/o DESY, Notkestr. 85, 22603 Hamburg, Germany, ³University of York, Heslington, York, YO1 5DD, UK

Diffraction data from single crystals of crambin, a small hydrophobic protein (4.7 kDa, 46 residues), can be collected to a resolution of 0.83 Å on a rotating anode generator. The reflections are over 90% above 2[sigma] at that limit. In EMBL Hamburg, a new wiggler beam line, BW7A, has recently been commissioned that allows the use of short wavelength radiation, around 0.6 Å. With the bright synchrotron source, crambin data was collected to the edge of the image plate detector or 0.67 Å at 100K. The 59,000 unique reflections creates a reflection to parameter ratio of 13 with 449 atoms.

The structure has been refined with SHELXL-96 to an R value of 7.9%. The model is currently being revised and parallel refinements with PROLSQ are underway.

Averaging the electron density for backbone atoms and calculation of a difference synthesis revealed that [sigma] bonding electrons were visible along the chain. Further [pi] electrons can be seen for the peptide unit. This structure shows great promise for testing refinement schemes for protein as well as revealing details of protein bonding through charge density refinements.