Cumulative Intensity Distribution Question?

Chris Colbert colbc at
Fri Jan 9 14:36:45 EST 1998

I have a question concerning cumulative intensity distributions.

My problem is that the distribution from my current data differs
from the theoretical values by atleast 10% at Z=0-0.2 and less
beyond that with Z being defined by CCP4 truncate.  Both curves
for acentric and centric data are below the theoretical curves.

My questions then are:

1)  Has anyone had a similar experience with their data? and what
did you do to correct the data as far as a stucture solution is 

2)  What could be the reason that my curves differ from the theoretical?
	Twinning? etc.

3)  Any further thoughts as to the meaning of the cumulative intensity
distribution.  What types of problems can be identified from this analysis?

If you would like to see a copy of my plot or display the truncate information
for yourself, please email me and I will email the plot to you or the output
log file for you to display it in CCP4 using xloggraph.  

Thanks for any help you can offer,

Chris Colbert
colbc at

Christopher L. Colbert
Purdue University Macromolecular Crystallography         
Lilly Hall of Life Sciences                         

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