[ccp4bb]: Re: your mail

[Norbert Straeter <strater@chemie.fu-berlin.de>]

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> I have a protein that requires 0.5 to 1M NaCl to be soluble at 10mg/ml. My
> question is whether I should bother screening this protein and whether there
> are any protein crystals grown using protein buffers at such high salt
> concentrations? I am aware that ammonium sulfate is used at high
> concentrations to grow many crystals but are there crystals successfully
> grown from proteins that require high salt concentrations to be soluble?
> Please share your experience. Thanks
> 
One obvious thing to try first is to slowly reduce the salt
concentration. Using this method I crystallized Aminopeptidase A from
E. coli, which precipitates if the salt concentration (NaCl or KCl) is
lower than about 0.8 M. In the case of this protein vapor diffusion was
o.k., e.g. the dilution of the protein as the drop grew bigger did not
prevent the formation of crystals. Otherwise you might want to try
diffusion across a membrane.

Good luck,
Norbert