Dear CCP4bb,
I am having a little issue with some data that on the surface looks OK but it is not playing ball.
The target is a hetero-octamer - 4 each of 2 subunits.
Autoindexing with iMosflm appears to nail the lattice as mP (Penalty of 1; next best is mC with penalty of 40)
Cell dimensions are 94, 147,102, 90, 102, 90.
Scala gives
Overall InnerShell OuterShell
Low resolution limit 31.47 31.47 2.64
High resolution limit 2.50 7.91 2.50
Rmerge 0.120 0.039 0.710
Rmerge in top intensity bin 0.041 - -
Rmeas (within I+/I-) 0.144 0.047 0.859
Rmeas (all I+ & I-) 0.144 0.047 0.859
Rpim (within I+/I-) 0.080 0.026 0.478
Rpim (all I+ & I-) 0.080 0.026 0.478
Fractional partial bias -0.033 -0.012 -0.084
Total number of observations 273802 9515 34527
Total number unique 90106 2968 11962
Mean((I)/sd(I)) 6.8 17.6 1.6
Mn(I) half-set correlation CC(1/2) 0.993 0.998 0.557
Completeness 96.8 98.3 88.6
Multiplicity 3.0 3.2 2.9
Anomalous completeness 88.5 97.2 73.5
Anomalous multiplicity 1.6 1.7 1.6
DelAnom correlation between half-sets -0.018 0.111 0.003
Mid-Slope of Anom Normal Probability 0.959 - -
Outlier rejection and statistics assume that there is no anomalous scattering
Average unit cell: 94.03 146.71 101.90 90.00 102.41 90.00
Space group: P21
Average mosaicity: 0.83
Minimum and maximum SD correction factors: Partials 0.65 155.76
But then cTruncate gives
TRANSLATIONAL NCS:
Translational NCS has been detected at ( 0.000, 0.500, 0.500).
The probability based on peak ratio is 0.02% that this is by chance (with resolution limited to 4.00 A).
This will have a major impact on the twinning estimates and effectiveness of the truncate procedure
Peak# Location Ratio Q-score
1 ( 0.00, 0.50, 0.50) 0.44 0.02
The analysis uses the peak heights in the patterson map that are further than 14 A (approx. 4 Ca-Ca) from the origin. The presence of a large off origin peak (above 20%) and/or a very low Q-score, below 1.0, is a string indicator of the presence of tNCS. An intermidiate Q-score, between 5.0 and 1.0, may indicate weak tNCS or be the result of cross vector of a large scatterer such as a cluster or heavy metal.
Crystals from similar drops have previously autoindexed as C2
101.8, 146.7, 94.9, 90, 102.5, 90
Molecular replacement has not been successful (so far) and I am wondering if the translational NCS is causing an issue. Perhaps the space group/cell dimensions are not as autoindexing suggests if the tNCS interfering. Should I be treating the data some specific way ?
If anyone has experience of this and can provide advice/suggestions, then that would be much appreciated.
Kind regards,
Magnus
