Hi everyone,
Can anyone help me with interpretation of a self rotation function and
native Patterson from a dataset with pseudosymmetry? I've always been
a bit poor on spherical polars. The space group is P21 with beta =
92.2°. The kappa=180° section of the SRF, calculated using Molrep, is at
http://mole.mbfys.lu.se/~derek/selfRF_180.png
and contains two big peaks around 7 sigma. I'm having trouble
identifying these in the list of peaks from Molrep:
theta phi chi alpha beta gamma
Isym_i Isym_j
Sol_RF 1 0.00 0.00 0.00 0.00 0.00 0.00 1 1
Sol_RF 1 90.00 -90.00 180.00 0.00 180.00 0.00 1 2
Sol_RF 1 90.00 90.00 180.00 0.00 180.00 0.00 2 1
Sol_RF 1 0.00 0.00 0.00 0.00 0.00 0.00 2 2
Sol_RF 2 158.56 180.00 180.00 0.00 42.89 -180.00 1 1
Sol_RF 2 111.44 0.00 180.00 -180.00 137.11 0.00 1 2
Sol_RF 2 111.44 0.00 180.00 180.00 137.11 0.00 2 1
Sol_RF 2 21.44 0.00 180.00 180.00 -42.89 0.00 2 2
Sol_RF 3 165.65 0.00 180.00 -180.00 28.70 0.00 1 1
Sol_RF 3 104.35 -180.00 180.00 0.00 151.30 180.00 1 2
Sol_RF 3 104.35 180.00 180.00 0.00 151.30 -180.00 2 1
Sol_RF 3 14.35 -180.00 180.00 0.00 -28.70 180.00 2 2
It seems to me to be two copies of peak 2. I believe theta starts in
the middle, perpendicular to the page and phi starts on the x axis,
thus the peak just below the centre would be (21.44, 0, 180). I
presume that the second peak is the symmetry-related (158.56, 180, 0)?
However where is (111.44 0 180)? I would expect to see this near the
bottom of the plot, but it's not there. I'm sure I'm missing something
fundamental about the symmetry of the SRF projection, but
unfortunately I don't have a supervisor to bug about this (I *am* the
supervisor...)
In the native Patterson
http://mole.mbfys.lu.se/~derek/nativePatterson.png
there are two peaks of almost equal height. How can this be reconciled
with having only one strong peak in the SRF? There are most likely two
dimers in the asymmetric unit, but there may only be one, with very
high resulting solvent content. What's more the molecules are leucine-
rich repeat proteins and have weak internal symmetry. I believe this
was an issue with the ribonuclease inhibitor, but looking briefly at
the crystallisation article and structure article I wasn't able to
find a rationalisation of this problem. The 2-fold is perpendicular to
b*. How could this cause the two peaks?
Thanks
Derek
