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Hi Sunando,
- Try smaller drop volumes; also try lower protein concentrations.
- What kind of a crystallization technique are you using? Often, vapour
diffusion by hanging drop method leads to rapid nucleation events - not
necessarily the best/optimal crystals. Try sitting drop method with OIL
(if you haven't done so already). OIL helps retard nucleation - can't
say that enough. Be warned that the crystal size may stay the same or
be bigger.
- That you do not see visible cracks in 0.1 mm crystals doesn't imply
that these crystals are devoid of defects. I have driven myself up the
wall with a cartload of diffraction data from defective crystals that I
thought were ok simply because they didn't *appear cracked*.
Hmmm.. are cracked crystals any good??? Best way to judge this is to
collect data from your cracked and so-called *not cracked* crystals.
LOOKS very often don't reveal anything about the crystal diffraction.
Are they indexable and scaleable???
More importantly, how do the intensity statistics look (intensity
distribution, Wilson plot etc.)? Oh my! do they reveal telltale signs
of impending disaster or what!!!
Sometimes if the problem is persistent with a certain crystal form, it
might even be worthwhile going after another crystal form.
Good luck!
Raji
On Oct 27, 2005, at 5:10 PM, Sunando Datta wrote:
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Hi
this is not a crystallography question. I could able to grow
reasonable
big(0.2-0.3mm) crystals of my protein. I am using 2-2.5% Peg4k/peg
5K(MME),Mg 5 mM, against 1M MgCl2 in reservoir(prot conc. approx.
20mg/ml, in hepes
,7.0,100mM NaCl, 1mMDTT, 10% glycerol). The crystals grow very
fast(with in 1 day
they appear and grow to max. size by 4 days. They grow at room temp,
not
at 4 deg.
The problem is wheneve they are exposed in air, I see lot of cracks
on
the crystal surface..I am mounting at room temp. this problem is
arising
for bigger crystals not for 0.1 mm crystals. Crystals are growing on a
skinny precipitate which is difficult to handle during mounting.
Have any one experienced this kind of situation? do the crystals
diffract
with cracks on surface? if not how to tackle this problem??
Thanks
Sunando
