> -Secondly (referring to the attached image) in one of the lunes there is a line of reflections which is larger (i.e. more intense) and much more reasonably spaced.
>
Systematic absences- that would be your 4(1) axis - notice the row of spots leads directly to the beam center.
On 09/06/2015 09:48 PM, Rhys Grinter wrote:
> Dear All,
>
> I recently got some nice new well diffracting crystals for an exciting new protein I'm working. However after I collected some frames on the home source, I realised that the diffraction pattern for these crystals looks somewhat suspicious.
>
> -The first thing that tipped me off was the unusually long unit cell, the data was index as P41212 with a cell of 78,78,420. This led to many spot overlaps, however on closer inspect these reflections were not perfectly aligned.
> -Secondly (referring to the attached image) in one of the lunes there is a line of reflections which is larger (i.e. more intense) and much more reasonably spaced.
>
> This has led me to conclude that these crystals suffer from Non-merohedral twinning, i.e. the crystals are made up of two separate lattices offset by some arbitrary rotation. However I was wondering if someone with more experience in these matters could take a look at the attached diffraction and confirm my suspicions.
>
> Also, I was hoping someone could give me some suggestions on how to deal with this kind of data. The crystals diffract well (better than 2A at home) and at the synchrotron I should hopefully be able to achieve reasonable spot separation. From what I've read the best way of dealing with this kind of data is to determine the correct Space group and cell and integrate the two lattices separately. What is the best software and protocol to do this with?
>
> Also, does anyone have any tips for improving my crystals so they no longer exhibit this annoying pathology?
>
> All the best
>
> Rhys
>
> --
> Dr Rhys Grinter
> Sir Henry Wellcome Fellow
> Monash University
> +61 (0)3 9902 9213
> +61 (0)403 896 767
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