Iodine is ideally suited for Cu K-alpha SAD phasing, and iodide ions can
normally be easily added by soaking crystals in potassium iodide
containing solutions, which can be done at the time of cryopreservation.
A quick lit search will turn up the appropriate protocols. For
structural genomics work where MR was unsuccessful or unusable, iodide
soaks were found to work as much as 80% of the time.
I've used iodide-soaked lysozyme for an XRD teaching lab and
undergraduate research student training, and SAD phasing works really
well on an overnight data collection on our Oxford Diffraction PX-ultra
system. It's worth a shot, and very easy to do. Many proteins will
tolerate soaking, especially if crystallized from salts.
_______________________________________
Roger S. Rowlett
Gordon & Dorothy Kline Professor Emeritus
Department of Chemistry
Colgate University
13 Oak Drive
Hamilton, NY 13346
tel: (315)-228-7245
ofc: (315)-228-7395
fax: (315)-228-7935
email: rrowl...@colgate.edu
On 4/3/2018 10:46 AM, Eleanor Dodson wrote:
Well - the S f" is only ~ 0.5 at Cu Kalpha so the signal will be very
weak..
Very accurate data may get a solution but you first have to position
the S atoms...
Much easier to try to make a heavy atom derivative!
Eleanor
On 3 April 2018 at 15:26, Manoj Saxena
<00001d16aa30e8a1-dmarc-requ...@jiscmail.ac.uk
<mailto:00001d16aa30e8a1-dmarc-requ...@jiscmail.ac.uk>> wrote:
Hi All,
I am writing to seek advice on doing sulphur SAD data collection
at Cu based home source for a protein that is 12 KDa and has 6 S
atoms.
I have seen some links online and some references but would be
grateful if
you can share your know-how for success with this.
Like what multiplicity of data would be good to aim for and
data processing tips.
Inputs from people who have tried and failed would also be highly
appreciated.
Thank you
Manoj Saxena
University of Puerto Rico
