I may be biased, but the only way to really be sure is to shoot them.
If you see no spots at all, be sure to do a wide "oscillation" (rotation
during the exposure) shot as well. It is not unlikely for a salt
crystal to be oriented so that no relps are on the Ewald sphere, giving
no spots. But, if you sweep through 180 degrees during the exposure you
will at least have a nice, pretty symmetric diffraction pattern to look
at for a moment before the disappointment sets in.
-James Holton
MAD Scientist
On 4/15/2013 3:18 AM, Careina Edgooms wrote:
Dear ccp4
I have been performing trials on a protein DNA complex for a while now
and have not seen any crystals form. Today I checked an old plate
(over a month old) and I see 4 large crystals. *excitement* Three of
them look tetragonal in shape (like a pyramid) and one of them looks
hexagonal. I do not know if they are salt or protein. There is calcium
chloride in the buffer. They feel quite soft to touch. They do not
cause much birefringence. One of them does not seem to absorb much
izit. It did go a bit blue but not entirely.
How can I tell if this crystal is protein or not? Do you think its
worth trying to see how it diffracts?
Also, does Izit affect diffraction/ protein structures at all? Could I
use a crystal with Izit in a diffraction experiment and ultimately to
get the structure?
Best
Careina
