Increase chances playing with kappa to have Friedel pairs on same pictures. Collect starting from various angles at different locations on the crystal along the axis of the goniometer (make sure you shift enough the beam between each data set to avoid overlapping of irradiated area). As already mentioned, attenuate the beam as much as possible to avoid unnecessary damages. Are you experimenting at a top-up mode? Or decreasing ring current? Varistions in the intensity might become non negligible sonyou start and end intensity along the whole data sets should not be too different... Fe might change its ionic state because of radiation, so you need collecting very quickly as well.
Try MAD if SAD not working.
Leo
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Leonard CHAVAS
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Synchrotron SOLEIL
Proxima-I
L'Orme des Merisiers
Saint-Aubin - BP 48
91192 Gif-sur-Yvette Cedex
France
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Phone : + 33 169 359 746
Mobile : + 33 644 321 614
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-------- Original message --------
From: "Keller, Jacob" <[log in to unmask]>
Date: 04/08/2016 11:22 PM (GMT+01:00)
To: [log in to unmask]
Subject: Re: [ccp4bb] Anomalous data collection from long unit cell axis
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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