On 2 Jan 2008, at 17:15, Ethan Merritt wrote:
On Tuesday 01 January 2008 06:40, Mark A Saper wrote:
Well, I guess one shouldn't change versions of refmac in the middle
of a structure refinement. What are the major differences between .
0034 and .0066 ? I noted that form factors for the Se atom have
changed dramatically even though I'm using the same " anom formfactor
SE -8.13 5.05 " command. Is this because the program is now using
the wavelength on the .MTZ file ?
with .0034:
SE 8.8706 2.4098 5.8196 0.2726 3.9731 15.2372
4.3543 43.8163 2.8409
The first coefficient here is wrong.
with .0066:
SE 17.0006 2.4098 5.8196 0.2726 3.9731 15.2372
4.3543 43.8163 -11.7969
These are the values given for a1, b1, ... a4, b4 in Table 6.1.1.4
of International Tables for Crystallography Volume C (1995).
The value of c (-11.7969) corresponds to an f' value of
-14.6378 (= -11.7969 - 2.8409)
This could only be possible at the inflection point of the Se
anomalous scattering curve, and only for a beam with a very narrow
bandwidth. Current generation beamlines more typically yield an
effective f' of -5e to -10e in practice.
We have corrected it. It was due to double addition of f' (one from
anom formfactor and one from a la crossec calculation). Now it should
not happen
Garib
--
Ethan A Merritt Courier Deliveries: 1959 NE Pacific
Dept of Biochemistry
Health Sciences Building
University of Washington - Seattle WA 98195-7742
