Hi,
I can confirm what Bert Van Den Berg wrote about the round shaped
"crystals". It seems to appear often with DDM (in my case too, even
sometimes in several drops per screen) and first looks like phase
separation. Then it starts to be hard and is looking like a small CD
under the microscope. I don't know what it is, but when I put it on the
beam the diffraction was very weak and was looking like a powder
pattern. I could never optimize these "crystals".
For the needles, I would really try to optimize them. They are looking
promissing. Maybe try micro-seeding !
Christophe
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Christophe Wirth
Structural biology department
Biozentrum, University of Basel
Klingelberstrasse 70
CH-4056 BASEL
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Ngo Duc Tri wrote:
Dear ccp4 Users,
I would like to say thank you to all of your valuable advices to
optimize the needle crystal and related problems when dealing with
membrane protein.
Here I report the summary of your advices to help other students who
got the same problem:
1. Additive screening from Hampton Research maybe useful in some cases.
2. Can apply techniques/tricks that are used for soluble proteins,
such as vary Mg2+ salt conc and identity, temperature,
volume/reservoir ratio, protein conc. and even trying different
detergents and/or mixtures including DDM
3. Round shape crystal is maybe detergent crystal, but other opinion
shows that DDM cannot create crystal in aqueous solution. I am still
confused about this problem but it's hard to optimize these kind of
crystal.
4. Try to collect data on the micro-diffraction beamline (but the
facilities is only available in US and Europe).
5. Powder diffraction also can be used to check the protein crystal or
detergent crystal and even solve the structure.
Thank you very much for your advices and suggestion!
My best regards,
TriNgo
PhD Student- Sungkyunkwan University, Korea
