[phenixbb] Improvement of low resolution MR phases

Kajander, Tommi A tommi.kajander at helsinki.fi
Tue Jun 29 05:23:49 PDT 2021

Dear John,

Thanks for your suggestion - however I am not sure what this would mean? If look at the typical Wilson plot (which we of couse dont really have ... to 2 Å or 2.5Å) why would you expect an increase in intensity at this resolution?

Probably beyond my theoretical knowledge but I don't recall a case where the data would come back up in terms of I(sig) to above noise really?

(also in practical terms I think we might not have had the detector close enough since the data was limited to quite low resolution…)

Best wishes,

On 29 Jun 2021, at 11:13, John R Helliwell <jrhelliwell at gmail.com<mailto:jrhelliwell at gmail.com>> wrote:

Dear Tommi,
I have thought before about this kind of case, of 5 to 6 Angstrom resolution diffraction, namely that the molecular transform must increase again at higher resolution, say 2 1/2 Angstrom, at which therefore the measurable intensity would increase enough to maybe be above background.
To check this go back to your diffraction images and integrate to, say, 2Angstrom. Does the <I/sigI> show the increase at around 2 1/2 Angstrom resolution?
Obviously if you do have those higher resolution data measurable then matters improve all round.

Emeritus Professor John R Helliwell DSc

On 28 Jun 2021, at 12:56, Kajander, Tommi A <tommi.kajander at helsinki.fi<mailto:tommi.kajander at helsinki.fi>> wrote:

 Hello all,

I was wondering what would be current best protocols for trying to improve maps/phases for low resolution
MR / refinement solutions (5-6 Å resolution).

High solvent content of course, dimeric 2:2 protein complex so some NCS averaging and density modification
I assume might help (related structures known, currently maps very blobby, clear solution but I think should be able to do better...).

Also, refinement suggestions welcome.

Best route in phenix? So far worked initially with ccp4. Other suggestions also welcome.


Tommi Kajander, Ph.D.
Institute of Biotechnology
University of Helsinki
Viikinkaari 1 (P.O. Box 65)
00014 Helsinki, Finland
p. +358-50-4480991

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Tommi Kajander, Ph.D.
Structural Biology and Biophysics
Institute of Biotechnology
University of Helsinki
Viikinkaari 1 (P.O. Box 65)
00014 Helsinki, Finland
p. +358-2-941-58904 / +358-050-4480991
tommi.kajander at helsinki.fi<mailto:tommi.kajander at helsinki.fi>

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