Great response, thanks everyone.
Best advice came from Harry Powell, James Murry and Marcus Winter: Talk
to the guys in the Chemistry department. Didn't even know we had such a
thing. Or at least the diffractometer there. Didn't know about that.
The student will be much better taken care of.
There were also good suggestions for how to deal with small-molecule
data on PX equipment. Before I die of boredom, I'll give this a try,
but it won't be any time soon.
Best.
Andreas
On 24/03/2014 7:15, [log in to unmask] wrote:
> Hi,
>
> this depends on your equipment. You can mount a 0.1-0.2 mm xtal as if it was
> a protein crystal onto a regular litho loop or better yet on a steel pin
> that has a glass fibre glued into it. Use superglue to glue the crystal at
> one end carefully to the glass fibre.
> Then it is easy to mount the crystal as if it was a protein crystal.
> Expect to move your detector as close as it is possible without bumping into
> things. Hopefully you can get to about 1.4 A (or better but 1.4 is probably
> the least resolution you need to get). Try different exposure times and or
> x-ray generator currents so that you don't get overloads. Still use 1 deg
> oscillation range. Not useful to go higher in my experience.
> HKL2000 will work with the small molecule license but even the macro license
> should work (but requires a bit more fiddling with some of the parameters).
> Use direct methods in shelxs or shelxd(?). Keep in mind that the space group
> may be centric or has mirror planes: P21/c is quite common but I would not go
> so far as to suggest a space group without having seen some data.
> Then use shelxs (or h) to refine the structure. You may find it useful to get
> a copy of platon (Prof. Spek). http://www.cryst.chem.uu.nl/spek/platon/
>
> Or wingx: http://www.chem.gla.ac.uk/~louis/software/wingx/
>
> It's doable but takes a bit of time if you have no small molecule
> crystallography background.
>
> Ah and before you start, ask the student for elemental analysis results. If
> the compound contains very heavy atoms, your CuKa radiation may not be useful.
> In that case or perhaps in all cases if you need to switch to Mo radiation
> (then resolution is not a problem as in the case of CuKa radiation).
>
>
> Good luck.
>
> Lothar
>
> .
>
--
Andreas Förster
Crystallization and X-ray Facility Manager
Centre for Structural Biology
Imperial College London
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