发信人: crystalmaker (风雨无阻), 信区: Biology
标 题: Re: 蛋白质晶体衍射地背景问题
发信站: Unknown Space - 未名空间 (Sun May 22 16:07:50 2005) WWW-POST

Since when you changed the angle the spots are also changing so these spots
should not come from the detector problem.
if it is a protein crystal, you should have some spots (even few) at very low
resolution region; but your spots all appear around 2.5-3.0 A, no spots at
lower resolution, which seems not a protein one. plus, all the spots have very
high intensity.
sometimes we never understand why salt crystals appear under such a condition.


Since you said you have a lof of crystals in that drop, so you can try more
drops and collect the small crystals, either run a gel (if it is enough) or do
a Mass spectrum.



【 在 capry (IA) 的大作中提到: 】
: When I tried to collect the image of 0.5 degree, I saw one spot and when I
: increased the angle of the image to 5 degree (not rotating the crysal), I
say
: 4 spots. All spots are with high intensity. And resolution is between
2.5-3.0.
:
: When I did the rotation of the crystal, at some angle, the reflections are
: just gone.
:
: I am thinking of background diffraction from the buffer since the loop is
too
: big compared with the crystal. But I couldn't get much information. People
in
: our lab say protein crystal can't just have such small unit cell.
:
: 【 在 idiotic (confused) 的大作中提到: 】
: : Have you taken a few snap shots at different angles? If you did and those
: : spots were at the same positions, they are just fake spots (might be
defects
: : on the detector). Another possibility is the unit cell is very small and
you
: : have high symmetry and low mosaicity, you can only see a few spots. Try to
: : rotate 2-3 degrees and see if you can get more spots.
: :
: :
:
:

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