It does look very twinned..
What about P1 as the true spacegroup twinned to P2
Keep this cell then the twinning operator is -h,k,-l
Eleanor
Flip Hoedemaeker wrote:
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Dear All,
I'd like your thoughts about this one:
- dataset of a 20 kD soluble protein, apparent space group P2 with a=36.5,
b=41.7, c=42.8 and beta 95.5°, but indexing is difficult and not very
stable.
- Crystals look plate-like, are very anisotropic, they diffract beyond 2.5Å
in the plane of the plates but in the third dimension (along b) the spots
are very streaky and poorly resolved.
- Cumulative intensity distribution (from Truncate) indicates possible
twinning (see below). The twinning servers are not useful with this space
group, and feeding all lattice permutations I can think of in Detwin does
not give an obvious answer sofar.
- Mathews coefficient is very low (1.6 for one mol/ASU, indicating 22%
solvent...
What could we be looking at here? Is the apparent unit cell created by
multiple lattices, e.g. With the real b being around 80Å? Can we force this
in Mosflm somehow? Any ideas on how to proceed? (apart from growing better
crystals, which we are trying).
Thx Flip
--------
$TABLE: Cumulative intensity distribution:
$GRAPHS
:Cumulative intensity distribution (Acentric and centric)
:N:1,2,3,4,5:
$$
Z Acent_theor Acent_obser Centric_theor
Centric_obser $$
$$
0.0 0.0 0.0 0.0 0.0
0.1 9.5 3.3 24.8 5.7
0.2 18.1 6.0 34.5 9.7
0.3 25.9 10.9 41.6 15.8
0.4 33.0 17.2 47.3 21.1
0.5 39.3 24.8 52.1 25.9
0.6 45.1 32.7 56.1 32.8
0.7 50.3 40.5 59.7 38.1
0.8 55.1 47.3 62.9 42.5
0.9 59.3 54.5 65.7 48.2
1.0 63.2 60.2 68.3 53.0
$$
<B><FONT COLOR="#FF0000"><!--SUMMARY_BEGIN-->
$TEXT:Warning: $$ comment $$
WARNING: **** Cumulative Distribution shows Possible Twinning ****
$$
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