Hi Tom et al., While probably unrelated, as a fresh graduate student we did one experiment where we observed no diffraction signal at all - no beamstop shadow, solvent ring etc. Being clever (we thought), we ran burn paper from the slits into the hutch, then through the hutch step by step along the path, to the detector position. We confirmed that the beam was indeed aligned, and when the beamstop was removed, that the beam was getting to the large sheet of lead in front of the detector. It was at that point, that the problem become obvious. We still have about two centuries of burn paper left in the cold room!
In a second case we were working on a beamline on the west coast of the US. Every crystal we put on vanished before we could even collect data - the loops appeared empty as soon as we looked through the microscope (this sets the decade). The beamline had an extra strong magnet on the goniometer and on closer inspection we saw that the hutch wall next to the goniometer was peppered with many crystals - they were being catapulted out of the loop when the base 'flipped' onto the magnet. There were so many that others will know this beamline. Both are probably unrelated to what you observed, some crystals are just ghost crystals, a term coined by George DeTitta I think. I'd love to know why myself. If all else fails, grow more crystals - shameless plug http://getacrystal.org A wonderful holiday season to all and may the new year be full of strongly diffracting crystals and plenty of X-rays. Best wishes, Eddie Edward Snell Ph.D. President and CEO Hauptman-Woodward Medical Research Institute Assistant Prof. Department of Structural Biology, University at Buffalo 700 Ellicott Street, Buffalo, NY 14203-1102 http://hwi.buffalo.edu Phone: (716) 898 8631 Fax: (716) 898 8660 Skype: eddie.snell Email: esn...@hwi.buffalo.edu [cid:image001.png@01D25B9C.BD1AC640] Heisenberg was probably here! From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Tom Huxford Sent: Wednesday, December 21, 2016 2:45 PM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] Crystal with ZERO diffraction Dear ccp4b collective mind and experience, Greetings from San Diego. I have done my fair share of synchrotron data collection on many diverse macromolecular crystal systems. But this weekend was the first time that I ever shot crystals that failed to diffract entirely. Details: we have purified and crystallized an ~90 kDa proteolytic fragment containing a single point mutant version of a myosin motor domain in complex with a separate light chain polypeptide. The crystals are relatively small (10-30 microns in each dimension) but clearly crystalline in character (clear faces, edges, and facets). The crystals tested positive for protein by absorbance at 280 nm. This weekend we tested more than 40 of them for diffraction in different cryo solvents and did not observe a single identifiable diffracted ray. It was as if we had only cryo on the end of our loops. Increasing the time of exposure or annealing did nothing to improve the situation. Crystals from a different protein system that we also tested this weekend on the same beamline diffracted to beyond 1.3 Å. I only post this because, in my experience, crystals of this size and superficial quality always give some signal--even if it is horrifyingly bad. But never complete diffraction silence. We will work this week to identify what it is that we "crystallized". But can anybody who has had a similar experience suggest what it is that could be going on here? Thanks in advance for any responses. And happy holidays to us all. Tom Huxford. ====================== Tom Huxford. Structural Biochemistry Laboratory Department of Chemistry & Biochemistry San Diego State University (619) 594-1606
