We have datasets measured on crystals of a 19 kD protein that are P212121, with cell constants of 66, 75, 136. Matthew's considerations say 3, 4, or 5 copies per au are probable. xtriage finds a native peak at (0.0, -0.5, 0.036) that is 31 in height (origin=100) No self-rotation function peaks in xprep, that I can understand. Is this clearly translational symmetry that is making MR difficult? Hints as to how to go forward are welcome. thanks, Dave -- David N. Garboczi, PhD Phone: 301-496-4773 Investigator, Structural Biology Section (SBS) Laboratory of Immunogenetics (LIG) National Institute of Allergy and Infectious Diseases (NIAID) National Institutes of Health (NIH) Twinbrook 2/Room 110 12441 Parklawn Drive Rockville, Maryland 20852-1742 Fax: 301-402-0284 Email: [email protected]