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Dear Sarah,
it is very common that SeMet preps behave differently from the native
crystal w.r.t. the crystallisation conditions, and 13Mets for a 43kDa
protein is a lot!
Don't judge a book by its cover: The only way to find out whether your
differently shaped crystals diffract is to test them on an X-ray
machine. Until you have done so you do not even know whether you have
a "SeMet-Problem".
Have you tried micro-seeding from the native crystals into a drop with
SeMet-protein?
Tim
On 04/17/12 09:58, Qian Sarah wrote:
> Hi, I'm now facing a problem about selenomethionine-labelled
> protein crystallization.. Native protein crystallized very well and
> diffracted to 2.5A. However, SeMet-protein expression level
> decreased to only 1/10, and its crystals have different shape with
> before(native protein crystals have beautiful rhombohedral shape,
> while SeMet-protein crystals have a shuttle shape). For another
> crystalllization condition the SeMet protein don't crystallize at
> all while the native protein got crystals with even higher
> resolution. I don't know whether these "shuttle shaped" crystals
> are worthy to be used or not? But there are only 13 Met in my
> protein (43KD), why they have so much difference? Is this common, I
> mean, the huge difference between SeMet and native protein
> crystallization? And, any suggestions about what I can try to
> solve this Se-Met problem? (What I'm doing now is to screen
> crystallization kit with SeMet protein.)
>
> Thank you very much for your help! best, Sarah
>
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- --
Dr Tim Gruene
Institut fuer anorganische Chemie
Tammannstr. 4
D-37077 Goettingen
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