Attenuate the beam massively, and/or speed up the frame rate.
Also mount the flying saucers to enable shooting from the side--use a bent micromesh. Not totally sure what the crystals look like, though. Usually the crystallographic long axis is normal to the plate face.
JPK
-----Original Message-----
From: CCP4 bulletin board [mailto:[log in to unmask]] On Behalf Of Mohamed Noor
Sent: Thursday, August 04, 2016 4:59 PM
To: [log in to unmask]
Subject: [ccp4bb] Anomalous data collection from long unit cell axis
Dear all
I am trying to get an anomalous dataset at Fe K edge for my protein. While I can routinely get native datasets to a resolution of 2.5-3 A, the high radiation damage coupled with non-isomorphism is preventing me from getting a high multiplicity anomalous dataset. The best that I have got so far has an anomalous signal to 4.5 A but this was not enough for phasing (I tried CRANK2 and phenix.autosol) with various options.
The SG is C 2221, with unit cell of about 130, 420, 85. Secondly, the crystals are not perfectly shaped like those 'usual' ones. On one side, they are almost flat like a flying saucer (for a lack of better description). The Rmerge then becomes wavy every 80 degrees or so.
The protein is about 60 kDa with 5 Fe (mixture of heme and [Fe-S]) per monomer. The synchrotron has a PILATUS detector.
Are there any helpful hints that you can share?
Thanks.
Mohamed
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