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:[log in to unmask]] On Behalf Of Hubing Lou
Sent: 24 November 2010 14:09
To: [log in to unmask]
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
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