As you say - it is 17.006 in all versions of atomsf.lib I have access to!
It is good that f' and f" will now reflect the wave length, although the
wavelengh is so often wrongly recorded that this had better be an
optional request rather than the default!
Eleanor
Ethan Merritt wrote:
On Thursday 03 January 2008 01:25, Boaz Shaanan wrote:
Is the wrong value pointed out by Ethan the reason why we tend
to nearly always see +ve difference peaks over Se-met after refinement ?
Could be.
I have attached a plot of the net scattering factor for the two
sets of values.
I am curious as to exactly which version[s] of atomsf had the wrong
value for A1. The various old copies I have lying around on my disks
all contain the correct value.
Ethan
Just curious.
Regards,
Boaz
----- Original Message -----
From: Garib Murshudov <[EMAIL PROTECTED]>
Date: Wednesday, January 2, 2008 19:19
Subject: Re: [ccp4bb] Refmac 5.4.0066 versus Refmac 5.4.0034
To: [email protected]
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
Boaz Shaanan, Ph.D.
Dept. of Life Sciences
Ben-Gurion University of the Negev
Beer-Sheva 84105
Israel
Phone: 972-8-647-2220 ; Fax: 646-1710
Skype: boaz.shaanan?
