Hello phenixers,
I am a little bit at loss since this is the first time I have
encountered this situation.
I just collected preliminary data on a ligand soaked crystal. It goes
to about 1.85 A. The centrics and acentrics reflections tests look a
little deviant from ideal untwinned. I was looking at my xtriage log
file and it seemed to me like I have some twinned fraction. Phenix says
not. I realize too my completeness is not good.
Any educated insight would be helpful as I have never dealt with
twinning (if this actually the case).
Log file section:
Wilson ratio and moments
Acentric reflections
/<I>^2 :1.650 (untwinned: 2.000; perfect twin 1.500)
<F>^2/ :0.839 (untwinned: 0.785; perfect twin 0.885)
<|E^2 - 1|> :0.649 (untwinned: 0.736; perfect twin 0.541)
Centric reflections
/<I>^2 :2.099 (untwinned: 3.000; perfect twin 2.000)
<F>^2/ :0.749 (untwinned: 0.637; perfect twin 0.785)
<|E^2 - 1|> :0.703 (untwinned: 0.968; perfect twin 0.736)
NZ test (0<=z<1) to detect twinning and possible translational NCS
-----------------------------------------------
| Z | Nac_obs | Nac_theo | Nc_obs | Nc_theo |
-----------------------------------------------
| 0.0 | 0.000 | 0.000 | 0.000 | 0.000 |
| 0.1 | 0.052 | 0.095 | 0.171 | 0.248 |
| 0.2 | 0.126 | 0.181 | 0.285 | 0.345 |
| 0.3 | 0.197 | 0.259 | 0.371 | 0.419 |
| 0.4 | 0.271 | 0.330 | 0.440 | 0.474 |
| 0.5 | 0.334 | 0.394 | 0.499 | 0.520 |
| 0.6 | 0.394 | 0.451 | 0.553 | 0.561 |
| 0.7 | 0.447 | 0.503 | 0.600 | 0.597 |
| 0.8 | 0.497 | 0.551 | 0.629 | 0.629 |
| 0.9 | 0.541 | 0.593 | 0.660 | 0.657 |
| 1.0 | 0.581 | 0.632 | 0.697 | 0.683 |
-----------------------------------------------
| Maximum deviation acentric : 0.062 |
| Maximum deviation centric : 0.078 |
| |
| _acentric : -0.050 |
| _centric : -0.021 |
-----------------------------------------------
L test for acentric data
using difference vectors (dh,dk,dl) of the form:
(2hp,2kp,2lp)
where hp, kp, and lp are random signed integers such that
2 <= |dh| + |dk| + |dl| <= 8
Mean |L| :0.441 (untwinned: 0.500; perfect twin: 0.375)
Mean L^2 :0.270 (untwinned: 0.333; perfect twin: 0.200)
The distribution of |L| values indicates a twin fraction of
0.00. Note that this estimate is not as reliable as obtained
via a Britton plot or H-test if twin laws are available.
Cheers,
--
Yuri Pompeu
