Dear Murugan,
Am 29.06.10 11:05, schrieb Vandu Murugan:
Dear all,
I have collected a 2.7 angstrom home source data with Cu-Kalpha
source for a protein with 6 cysteines, with a multiplicity of around
23. I need to know, is there any significant anamolous signal present
in the data set, since there is no good model for my protein. Can any
one tell, which program to run, and what parameter to see? Thanks in
advance.
cheers,
Murugan
estimating the quality of the anomalous signal is not trivial, and
several quality indicators have been discussed (see for example Fu, Rose
& Wang, Acta Cryst D60, 499-506 (2004), or Zwart, Acta Cryst D61,
1437-1444 (2005)).
If you process your data with XDS, there are two quality indicators for
the anomalous signal, given both in the CORRECT.LP and in the XSCALE.LP
file. One is the correlation of anomalous differences between two
randomly chosen subsets that should have the same anomalous difference
due to crystallographic symmetry, called RANOM. The other describes the
absolute anomalous difference divided by their standard deviation,
called SIGANO. A typical rule of thumb (and the one that I use) is, that
RANOM should be >~ 30%, and SIGANO should be >~ 1.2. However, these
indicators might not be realistic (see references above) and therefore
should be taken with a grain of salt.
Good luck,
Dirk.
--
*******************************************************
Dirk Kostrewa
Gene Center Munich, A5.07
Department of Biochemistry
Ludwig-Maximilians-Universität München
Feodor-Lynen-Str. 25
D-81377 Munich
Germany
Phone: +49-89-2180-76845
Fax: +49-89-2180-76999
E-mail: kostr...@genzentrum.lmu.de
WWW: www.genzentrum.lmu.de
*******************************************************
