Hi Peter,
Thanks for your reply.
>This data can be
processed to P3 or P321 with the R-fac almost the same
>After that, I used
Bales to do the MR, two solutions were found in P32
>(dimmer) and one in
P32 21 (monomer)
>Then, I refine the
structure using phenix.refine in both P32 and P32 21 sets, but the R/Rfree
stopped at 0.19/0.25 and never goes down.
>However, if I treat
the P32 data as a twin (with twin law h,-h-k,-l ), the R/Rfree can down to
0.12/0.18.
>Do an R vs R analysis
by loading up a model as well in xtriage to get a clue about the extend of the
pseudo symmetry.
I do the R vs R analysis with
P
And the D_ncs is high (0.95)
in resolution range 9.9841-4.2623, which may indicate an incorrect point group?
The results are as follow.
---------------------------------------------
Analysing possible
twin law : h,-h-k,-l
---------------------------------------------
mean |H| :
0.018 (0.50: untwinned; 0.0: 50% twinned)
mean H^2 :
0.001 (0.33: untwinned; 0.0: 50% twinned)
Estimation of twin
fraction via mean |H|: 0.482
Estimation of twin
fraction via cum. dist. of H: 0.487
Britton analyses
Extrapolation
performed on 0.47 < alpha < 0.495
Estimated twin
fraction: 0.455
Correlation:
0.9777
R vs R statistic:
R_abs_twin
= <|I1-I2|>/<|I1+I2|>
Lebedev, Vagin,
Murshudov. Acta Cryst. (2006). D62, 83-95
R_abs_twin
observed data : 0.022
R_abs_twin
calculated data : 0.090
R_sq_twin =
<(I1-I2)^2>/<(I1+I2)^2>
R_sq_twin
observed data : 0.001
R_sq_twin
calculated data : 0.006
Perfoming correlation
analyses
The supplied
calculated data are normalized and artificially twinned
Subsequently a
correlation with the observed data is computed.
Results:
Correlation : 0.832594802609
Estimated twin fraction : 0.49
Maximum Likelihood twin
fraction determination
Zwart,
Read, Grosse-Kunstleve & Adams, to be published.
The estimated
twin fraction is equal to 0.478
Log[likelihood]: 78991.418
twin fraction:
0.443
D_ncs in resolution
ranges:
9.9841 -- 4.2623 :: 0.950
4.2623 -- 3.4280 :: 0.694
3.4280 -- 3.0083 :: 0.655
3.0083 -- 2.7394 :: 0.885
2.7394 -- 2.5466 :: 0.853
2.5466 -- 2.3986 :: 0.824
2.3986 -- 2.2800 :: 0.817
The correlation of
the calculated F^2 should be similar to
the estimated
values.
Observed correlation
between twin related, untwinned calculated F^2
in resolutiuon
ranges, as well as ewstimates D_ncs^2 values:
Bin
d_max d_min CC_obs
D_ncs^2
1)
9.9841 -- 4.2623 :: 0.981 0.902
2) 4.2623 -- 3.4280 :: 0.970 0.482
3) 3.4280 -- 3.0083 :: 0.958 0.429
4) 3.0083 -- 2.7394 :: 0.954 0.783
5) 2.7394 -- 2.5466 :: 0.964 0.728
6) 2.5466 -- 2.3986 :: 0.953 0.679
7) 2.3986 -- 2.2800 :: 0.963 0.667
Best Regards,
Lauren