Dear Herman,
this might work. To get more realistic scaling/ merging statistics, one
should expand to P1, add independent noise to U's and coordinates,
create the hkl and force it back into the original symmetry.
Best,
Tim
On 02/13/2014 04:38 PM, [log in to unmask] wrote:
> By applying a high temperature factor, one should not suffer Fourier ripples, since the "missing" high resolution reflections have negligible intensities, or put differently, one simulates a poorly diffracting crystal.
>
> Best,
> Herman
>
> -----Ursprüngliche Nachricht-----
> Von: CCP4 bulletin board [mailto:[log in to unmask]] Im Auftrag von Tim Gruene
> Gesendet: Donnerstag, 13. Februar 2014 16:22
> An: [log in to unmask]
> Betreff: Re: [ccp4bb] create a lower resolution data set by truncating a high resolution data
>
> Dear Blaine Mooers,
>
> I don't think that you avoid Fourier ripples with this method. You may, however, increase the noise level so that the Fourier ripples drown in the noise.
>
> You don't really generate a low resolution data set by truncation for that very reason. Crystals that only diffract to 3.5A, say, usually do this because of a high degree of disorder with leeds to more noise.
>
> Of course you could add noise to the sigma-values, but this is merely cosmetics.
>
> There are repositories for frames (JCSG?), where you might want to get real data that diffract to the desired resolution, reprocess and then carry out the phasing experiments.
>
> Best,
> Tim
>
> On 02/13/2014 03:54 PM, Mooers, Blaine H.M. (HSC) wrote:
>> For some simulated phasing experiments, I want to create a lower
>> resolution diffraction data set by truncating a high resolution data
>> set. I would like to avoid Fourier ripples due to the truncation of
>> the high resolution data by downscaling the data such that
>> <I/sigma>=2.0 in the highest resolution shell of the truncated data.
>> What is the best way to do this?
>
>> Blaine Mooers Assistant Professor Department of Biochemistry and
>> Molecular Biology University of Oklahoma Health Sciences Center S.L.
>> Young Biomedical Research Center Rm. 466
>
>> Shipping address: 975 NE 10th Street, BRC 466 Oklahoma City, OK
>> 73104-5419
>
>> Letter address: P.O. Box 26901, BRC 466 Oklahoma City, OK 73190
>
>
>> office: (405) 271-8300 lab: (405) 271-8313 fax: (405) 271-3910
>> e-mail: [log in to unmask]
>
>> Faculty webpage:
>> http://www.oumedicine.com/department-of-biochemistry-and-molecular-bio
>> logy/faculty/blaine-mooers-ph-d-
>
>> X-ray lab webpage:
>> http://www.oumedicine.com/department-of-biochemistry-and-molecular-bio
>> logy/department-facilities/macromolecular-crystallography-laboratory
>
>> Small Angle Scattering webpage:
>> http://www.oumedicine.com/docs/default-source/ad-biochemistry-workfile
>> s/small-angle-scattering-links.html?sfvrsn=0
>
>
>
--
Dr Tim Gruene
Institut fuer anorganische Chemie
Tammannstr. 4
D-37077 Goettingen
GPG Key ID = A46BEE1A
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