1. CCP4 Daresbury Laboratory
UBOAT
Norman Stein
CCP4 Daresbury Laboratory
York 27/3/07

2. TRUNCATE replacement Converts I’s to F’s
Negative input I’s give positive output I’s, F’s
Calculates Statistics:
Moments of I
Wilson plot
Cumulative intensity distribution
Detection of anisotropy (Yorgo Modis)

3. Mathematical Detail Use Bayesian statistics
Combine prior knowledge and observations to give the posterior distribution.
Prior is the Wilson distribution
p(J) = (1/Σ) exp( - J/ Σ ) if J ≥ 0 (Acentric)
p(J) = if J < 0
p(J) = 1/(2πΣJ) exp( - J / 2Σ ) if J ≥ 0 (Centric)
p(J) = if J < 0
J is intensity, Σ is the mean intensity in the resolution shell
S French and K S Wilson Acta Cryst. A34, 517 (1978)

4. K S Wilson
A J C Wilson

5. Output intensity vs Input intensity (acentric)
J/σ – σ/Σ

6. Output Amplitude vs Input Intensity (acentric)
F/σ½
J/σ – σ/Σ

7. FUTURE WORK Twinning (H test initially)
Anisotropy (Clipper/Popov and Bourenkov)
Multiple data sets