Changes

From CCP4 wiki
Jump to navigationJump to search
795 bytes added ,  10:41, 10 December 2008
add R_d which measures radiation damage
Line 17: Line 17:  
Weiss and Hilgenfeld <ref name="WeHi97">M.S. Weiss and R. Hilgenfeld (1997) On the use of the merging R-factor as a quality indicator for X-ray data. J. Appl. Crystallogr. 30, 203-205[http://dx.doi.org/10.1107/S0021889897003907]</ref>).
 
Weiss and Hilgenfeld <ref name="WeHi97">M.S. Weiss and R. Hilgenfeld (1997) On the use of the merging R-factor as a quality indicator for X-ray data. J. Appl. Crystallogr. 30, 203-205[http://dx.doi.org/10.1107/S0021889897003907]</ref>).
   −
* measuring quality of averaged intensities/amplitudes:
+
==== measuring quality of averaged intensities/amplitudes ====
    
for intensities use  
 
for intensities use  
Line 34: Line 34:     
In the sums above, the summation omits those reflections with just one observation.
 
In the sums above, the summation omits those reflections with just one observation.
 +
 +
==== measuring radiation damage ====
 +
 +
We can plot (Diederichs <ref name="Di06">K. Diederichs (2006). Some aspects of quantitative analysis and correction of radiation damage. Acta Cryst D62, 96-101 [http://strucbio.biologie.uni-konstanz.de/strucbio/files/Diederichs_ActaD62_96.pdf]</ref>)
 +
 +
<math>
 +
R_{d} = \frac{\sum_{hkl} \sum_{|i-j|=d} \vert I_{hkl,i} - I_{hkl,j}\vert}{\sum_{hkl} \sum_{|i-j|=d} (I_{hkl,i} + I_{hkl,j})/2}
 +
</math>
 +
 +
which gives us the average R-factor of two reflections measured d frames apart. As long as the plot is parallel to the x axis there is no radiation damage. As soon as the plot starts to rise, we see that there's a systematical error contribution due to radiation damage.
 +
 +
Strong wiggles at very high d are irrelevant as only few reflections contribute.
    
=== Model quality indicators ===
 
=== Model quality indicators ===
1,313

edits

Cookies help us deliver our services. By using our services, you agree to our use of cookies.

Navigation menu