You can try e.g.
- micro seeding
- change MPD concentration (lower MPD especially with seeding)
- scan the pH range
- change protein concentration (lower protein conc. especially with
seeding)
- try different temperatures (4 degrees, 20 degrees, higher, if your
protein supports it)
- add another purification step
- collect data and check whether you can solve the structure with the
twinned data
- carry out restricted proteolysis or slightly modify the protein
(expression system, purification tags ...)
For your second question, you can use small volume concentrators to check
the effect of
- different salts
- different salt concentrations
- different buffers
- different pH
- additives, especially reducing agents like DTT, beta-ME
- addition of, say, 5% glycerol
I am sure there are a lot more possibilities. If you explain a little more
what you have already done, we might give even more concise answers.
Cheers, Tim
--
Tim Gruene
Institut fuer anorganische Chemie
Tammannstr. 4
D-37077 Goettingen
GPG Key ID = A46BEE1A
On Fri, 21 Dec 2007, shivesh kumar wrote:
> Dear all,
> I have crystallized a protein in 63% of MPD at pH 3.8-4.6.The crystals are
> twinned but with sharp edges.I welcome all the suggestions to get single
> crystals.Also,I have needles of other mutant protein,the problem is during
> concentration,it gets precipitated even in the centricon.What should I do to
> avoid this precipitation to have a concentrated protein.Thanx in advance for
> the suggestions.
> Shivesh
>
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