I played around with a few years back - tried all kinds of different
data collection strategies and wavelengths.
What worked for me was collecting data at wavelength of 1.7A from a
few different crystals and then merge them together to get a higher
redundancy.
Both calcium and sulfur signals were visible and provided enough
phasing power.
Bone recognition mechanism of porcine osteocalcin from crystal
structure.
Hoang QQ, Sicheri F, Howard AJ, Yang DS.
Nature. 2003 Oct 30;425(6961):977-80.
Radiation damage was a concern with longer wavelength.
Cheers,
Quyen
_______________________________
Quyen Hoang, Ph.D
Department of Biochemistry and Molecular Biology,
Start Neurosciences Research Institute
Indiana University School of Medicine
635 Barnhill Drive, Room MS0013D
Indianapolis, Indiana 46202-5122
Phone: 317-274-4371
Fax: 317-274-4686
email: [email protected]
On Nov 11, 2009, at 10:23 AM, Jim Pflugrath wrote:
2.29 Angstrom is an excellent wavelength for Cl, Ca and S anomalous
scatterers. This is the wavelength produced by a Cr home source.
Some older references:
Acta Crystallogr D Biol Crystallogr. 2003 Nov;59(Pt 11):1943-57.
Epub 2003
Oct 23. Away from the edge: SAD phasing from the sulfur anomalous
signal
measured in-house with chromium radiation.
Acta Crystallogr D Biol Crystallogr. 2005 Jul;61(Pt 7):960-6. Epub
2005 Jun
24. Away from the edge II: in-house Se-SAS phasing with chromium
radiation.
Acta Crystallogr D Biol Crystallogr. 2005 Aug;61(Pt 8):1013-21. Epub
2005
Jul 20. Structure determination of a novel protein by sulfur SAD using
chromium radiation in combination with a new crystal-mounting method.
I'm sure there are several structures done with Cr radiation since
the above
articles were published. Does any body else want to chime in?
Jim
-----Original Message-----
From: CCP4 bulletin board [mailto:[email protected]] On Behalf Of
Matthias Zebisch
Sent: Wednesday, November 11, 2009 6:16 AM
To: [email protected]
Subject: [ccp4bb] sulfur sad phasing
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
