Frozen vs Room temp. crystals
brad at helix0.chem.iastate.edu
Wed Apr 17 11:07:32 EST 1996
Bill Hunter (wnh at spec.ch.man.ac.uk) wrote:
: Dear Mark,
: Do you see a change in unit cell dimensions? I would be interested to know
: about MFID v resolution for your 2 data sets? Does a reduction in
: mobility/thermal motion lead to improved scattering? Whilst I've seen
: publications on protein models refined against data sets collected at different
: temperatures I don't recall seeing a detailed comparision of the actual data.
: Do you know of any relevant papers on the subject?
I've just finished collecting 2 data sets one at room temp and one at 107K.
The difference the data stats is remarkable. Resolution increased from 3.2A
to 2.6A. My unit cell parameters changed a little ~0.3A in axial lengths.
I am refining both models now and after several cycles of refinement
the RMSD in coordinates is ~0.15A, essentially the same structure. My data
are much better at 107K, which I feel are do to two factors. 1) There is less
thermal motion. 2) There is less decay of the crystal in the X-ray beam. I
was about to increase my collection time/frame by a factor of 1.5.
Also my crystals grew from PEG and I used 25% glycerol as the protected, worked perfectly. Hope the info. helps.
Brad Poland, ISU Ames, IA. ____/\o__ _ |/<_ <\
brad at helix0.chem.iastate.edu (_)| (_) / >
Some people eat to train, I train to eat!
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