Differentiate salt and protein crystals

From: Theresa H. Hsu
Date: 15 March 2012 15:43

Hi all.

I set up some trays of membrane protein remotely in cubic phase. I don't have ready access to them so I can't shoot/pick the crystals. Under polarising lights, some crystals appears coloured across many conditions, making me think these are salt. Is there some knowledge of inorganic chemistry that be relied to prioritise some for reproductions at my lab? Can detergents crystallise and produce colours under polarising light?

Thank you.

Theresa

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From: Jingquan Tan


Hi Theresa,

Your observation of colored crystals under polarising lights seems odd to me. I assume your protein should be colorless and under normal light these crystals are colorless? Are these trays set up in glass plate or plastic plates? If you are willing to upload some pictures, I might be able to tell you whether they are salt crystals or not.

Regards

Jingquan

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From: Jon Agirre


The best reproduction I can suggest would be to setup one or two LCP experiments exchanging the protein for its buffer. If you get crystals, you know for sure they're not protein.

Cheers,

Jon

--

Dr. Jon Agirre

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From: Jacob Keller 

It should be pointed out that the converse is not true: if you don't get crystals from buffer-only crystallizations, it doesn't mean that your putative protein crystals are really protein.

Jacob