Hi Nat,
okay. Looks like I missed this. Perhaps the data sets that I wish had Fiedel
pairs didn't and this solidified my incorrect assumption(s) about pdb
policy.
So Fiedel pairs are there when deposited. What about storage of images? Is it
coming soon - it feels like that it is about time....
Lothar
> On Fri, May 16, 2014 at 7:12 AM, <[log in to unmask]> wrote:
>
>> Short of storing images, which is the ultimate preservation of primary
>> information, I have always been puzzled by the fact that the PDB only
>> stores
>> unique reflections i.e. no Friedel pairs even when provided. Is this
>> outdated
>> perhaps ? I remember that my deposited SFs in the past where reduced to not
>> contain Friedel pairs. If there had been a concern about increasing the
>> storage space by actually less than twice the space for unique SFs, this
>> may
>> be invalid today and is still far less than the space required for images.
>> However, it is possible that the information content in Friedel pairs is
>> deemed insignificant compared to their extra costs. I for one would
>> appreciate
>> having access to Friedel pairs very much.
>>
>
> They definitely store Friedel pairs! Maybe you're confused by the layout
> of the mmCIF file, which (like MTZ) usually lists just the unique
> (non-anomalous) indices, but with separate values for F+/F- when they are
> available. I've been making extensive use of anomalous data depositions -
> unfortunately there aren't as many as we would like, either because many
> people do not realize that this is useful information even when the
> experiment was not specifically looking for anomalous signal, or because
> the complexity of PDB deposition discourages providing the most complete
> data.
>
> An even more useful improvement would be to make deposition of unmerged
> intensities straightforward - the JCSG does this somehow but it is
> non-trivial for the average user. Hopefully this will also change soon.
>
> -Nat
>
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