Dear Felix,
as far as I understand we are talking about the frame width, not the
total data range for indexing ("10 degree rotations to get enough spots
per frame"). I have used 180degrees of data for indexing. At least XDS
places the reflection at the centre of the frame so that with a 10deg
frame width the position is know within +/-5 degree - it is not
surprising indexing fails here.
Regards,
Tim
On 03/25/2014 09:41 AM, Felix Frolow wrote:
> Dear Tim,
> I am sure your statement is too general and is not very precise.
> 10 deg oscillation range is as precise as 0.1 deg. Positions of diffraction spots on the area detector have
> defined position on rotation axis within the precision/accuracy of the stepping motor and the spacial resolution of the area detector
> and NOT defined by oscillation range. If it does, change your setup. We need sometimes 10 deg to have enough reflections for indexing. Obviously we
> need some reflections to define the orientational matrix and cell dimensions.
>
> FF
>
> Dr Felix Frolow
> Professor of Structural Biology and Biotechnology, Department of Molecular Microbiology and Biotechnology
> Tel Aviv University 69978, Israel
>
> Acta Crystallographica F, co-editor
>
> e-mail: [log in to unmask]
> Tel: ++972-3640-8723
> Fax: ++972-3640-9407
> Cellular: 0547 459 608
>
> On Mar 25, 2014, at 10:26 , Tim Gruene <[log in to unmask]> wrote:
>
>> Dear David,
>>
>> I dare claim that rather you do not know how to use the listed programs
>> in the case for small molecule data rather than none of them were
>> optimised. E.g. 10degree frames loose all the possible accuracy in the
>> phi-direction so I am not surprised you had trouble indexing. There is
>> no reason for that, if you know which parameters to modify.
>>
>> In addition to that, concluding from one single data set that programs
>> are not optimised may be a little overinterpreted. In my experience,
>> this interpretation does not hold.
>>
>> Best,
>> Tim
>>
>> On 03/24/2014 10:03 PM, David Schuller wrote:
>>> Coincidentally, I just spent my day trying to index a lattice of ~ 10 x
>>> 10 x 11 A.
>>>
>>> Mounting samples: if the compound is stable, just glue it to the end of
>>> a steel pin. No muss, no fuss.
>>>
>>> We had to attenuate our synchrotron beam heavily to make it work; motors
>>> can only turn so fast.
>>>
>>> We did 10 degree rotations to get enough spots per frame per imaging.
>>> Detector setup allowed for ~ 1 A resolution.
>>>
>>> Indexing was a challenge for many of the samples, heavily overloaded
>>> spots and streaks seemed to be causing the most problems.
>>>
>>> We tried various of the usual macromolecular programs for indexing;
>>> HKL2000, iMosFlm, XDS, DPS. None of them seem to be optimised for this,
>>> but some of them actually worked in some instances.
>>>
>>>
>>>
>>>
>>>
>>> On 03/24/14 14:04, Andreas Förster wrote:
>>>> Dear all,
>>>>
>>>> I've been approached by a materials student with a petri dish full of
>>>> big, sturdy, salty, yellow crystals. He claims I have the best kit
>>>> for single-crystal diffraction on campus.
>>>>
>>>> I would very much appreciate advice on how to deal with this, anything
>>>> in the range from "won't work" to "use software X to analyze data in
>>>> space group P-43N" would be welcome.
>>>>
>>>> Thanks.
>>>>
>>>>
>>>> Andreas
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>
>> --
>> Dr Tim Gruene
>> Institut fuer anorganische Chemie
>> Tammannstr. 4
>> D-37077 Goettingen
>>
>> GPG Key ID = A46BEE1A
>>
>
>
--
Dr Tim Gruene
Institut fuer anorganische Chemie
Tammannstr. 4
D-37077 Goettingen
GPG Key ID = A46BEE1A
