Dear CCP4 community,
(hijacking the thread)
I so far failed to get a sulfur SAD phased structure and I blamed it
on the low symmetry space group C2 plus weakish diffraction if you
don't want to overexpose your crystal and be able to collect 20-30x
redundancy.
What do the expert think about fine slicing versus "regular" data
collection for sulfur SAD phasing ?
Thanks,
Jürgen
On Nov 11, 2009, at 8:19 AM, Miguel Ortiz Lombardia wrote:
Le 11 nov. 09 à 13:16, Matthias Zebisch a écrit :
Dear bb!
What is the optimal wavelength for Sulfur SAD phasing?
Is it 1.9A or should one go below that to reduce absorption/damage.
Also, would the same wavelength be appropriate to maximize anomalous
scattering to position chlorides, calcium, sulfate in already
phased structures?
Thanks in advance,
Matthias
Hi Matthias,
We collected a highly-redundant sulfur-SAD data set at 2.0 A
wavelength. We managed to solve the structure thanks to two of the
three sulfur atoms present in the protein, plus one chloride ion
that happened to be bound to it. Radiation damage was an issue, but
only after anomalous redundancy was higher than 30. With very, very
high redundancy it was not possible to solve the structure. Thus, in
some cases, it may be worth trying with less images.
Of course, as Fred said, the precission of the measurements is
extremely important for sulfur-SAD phasing.
Best,
-- Miguel
Architecture et Fonction des Macromolécules Biologiques (UMR6098)
CNRS, Universités d'Aix-Marseille I & II
Case 932, 163 Avenue de Luminy, 13288 Marseille cedex 9, France
Tel: +33(0) 491 82 55 93
Fax: +33(0) 491 26 67 20
e-mail: miguel.ortiz-lombar...@afmb.univ-mrs.fr
Web: http://www.pangea.org/mol/spip.php?rubrique2
-
Jürgen Bosch
Johns Hopkins Bloomberg School of Public Health
Department of Biochemistry & Molecular Biology
Johns Hopkins Malaria Research Institute
615 North Wolfe Street, W8708
Baltimore, MD 21205
Phone: +1-410-614-4742
Lab: +1-410-614-4894
Fax: +1-410-955-3655
http://web.mac.com/bosch_lab/
