I think there may be two effects going on here:
I think the "ears" on the round spots which also feature on the more rod shaped spots if you look closely could be related to a misalignment of the beamline optics. I think the change in spot shape from round to rod shaped is due to the crystal quality. Do the "ears" only feature on this image of this crystal or do they appear on other images? If the ear effect is a one off then that would tend to suggest it isn't a beamline optic effect. Liz Dr. Liz Duke Principal Beamline Scientist Diamond Light Source Harwell Science and Innovation Campus Chilton OX11 0DE UK Tel. 01235 778057 Mob. 07920 138148 From: CCP4 bulletin board [mailto:[email protected]] On Behalf Of Hubing Lou Sent: 24 November 2010 14:09 To: [email protected] Subject: [ccp4bb] unusual diffraction spots Dear CCP4BBer, I recently collected a dataset at synchrotron. The diffraction was quite anisotropic with one direction to 2.1Angstrom while the other is 3.0Ang. What unusual is in the diffraction image (see the attached file), clearly at low resolution there were some spots with tails ("two ears") and at the high resolution shell the spots turned to be rod-shaped. Please, can anyone explain how this could be? Is this related to the anisotropy? The protein was N-terminal his6-tagged, we are currently preparing new samples with the His-tag removed. But any other suggestions are also very welcomed. Regards, Hubing
