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On 08/19/13 16:49, Mahesh Lingaraju wrote:
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Hello people 

I recently obtained hexagonal rod like crystals (150x50x20 um) which turned out to be non diffracting. What is the usual convention for cases like this ? do people usually give up on the condition or still try to optimize it ? 

It depends: are other crystal forms available, and have you exhausted all of the commonly available screening kits?

Are there any ligands which you might try adding to the crystallization to firm up the lattice?

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The crystals are also not very reproducible. I believe it is because of ammonium acetate in the condition causing fluctuations in the pH because of its volatility. Is there any way to work around such a problem ?

When I was young and stupid, I set up some hanging drop crystals with ammonium in the drop, but not in the reservoir. I got some xtals that depended on the resulting pH change. Then I figured out that I should put the ammonium salt in both the drop and the reservoir.
You don't mention your conditions, but if you are doing something similar, you might change your procedures.

Or you could try substituting something else for the ammonium. Or increase the amount of buffer. And try a range of pH conditions.

Cheers,

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All Things Serve the Beam
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                               David J. Schuller
                               modern man in a post-modern world
                               MacCHESS, Cornell University
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