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Great Idea! And if you want to gradually drop the pH
without using dialysis buttons, use carbonated beverage as
the reservoir solution. Put weakly buffered protein in the drop,
perhaps with enough PEG to be close to the nucleation point.
Cover with a glass cover slip instead of tape. CO2 diffusion
should gradually lower the pH and induce crystallization.
Going the oposite way is easy with ammonia, but most proteins
get more soluble at high pH, I think. Of course you can diffuse
NH3 out of the droplet into a nonvolatile acidic reservoir.
Does anyone know about the variablity between batches of diet coke?
Ed
Jon Caruthers wrote:
actually, to follow up here, I grew crystals of a MBP-protein fusion
construct using diet-coke as a buffer. It turned out that these crystals
diffracted better than anything grown with any other buffer of similar
pH (2Å vs. ~3.5Å with other buffers), so maybe there's something to this
idea of using CO2 as a buffer.
Jon Caruthers
Begin forwarded message:
*From: *"Bryan W. Lepore" <[EMAIL PROTECTED]>
*Date: *October 14, 2005 10:42:54 AM PDT
*To: *CCP4 Bulletin Board <ccp4bb@dl.ac.uk>
*Subject: Re: [ccp4bb]: increase the size of crystals
*
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On Fri, 14 Oct 2005, William Scott wrote:
Maybe you should try Perrier. ;-)
Excellent point. There might be enough benzene in it to be a
cryoprotectant.
ha ha!
but seriously, if water sits around, the partial pressure of CO2
could be around
400 microatmospheres, thanks to the industrial revolution, so you'll
have a nice
equilibrium of bicarbonic acid and co2 ( its around pH 5.4)
see j. chem. ed. 77, 1574, 2000 <- study of reef response to climate
change
-bryan
