Just checking my oxidized Se-Met experiments, I have 12658 to 12661 eV
for my peak energies, and 3 eV lower for the inflection.
As others have said, do the fluorescence scan. Use your experimentally
determined values.
Engin
On 7/16/09 11:54 AM, Phil Jeffrey wrote:
Always take the scan results ahead of the typical values unless they
are obviously wrong. Only use the "predicted" values if the scan is
broken or too weak (e.g. very small crystals) and in that case I'd be
tempted to add 10-20 eV to the "typical" peak wavelength to make sure
you weren't actually collecting the inflection point since they are
typically very close in SeMet.
In my NSLS X29-dominated data collections, I find I end up using
something like this for non-oxidized SeMet:
Peak: 12664 eV, 0.9790 Angstrom (usually in range 12662-12664)
Infl: 12662 eV, 0.9792 Angstrom (usually in range 12660-12662)
I also typically use high energy remote: 12860 eV, 0.964 Angstrom
give or take a few eV. This tends to translate well between the
relatively small number of beamlines that I personally end up using.
But I always prefer to take the results from the Chooch analysis of
the scan from the actual crystal.
Cheers (and good luck)
Phil Jeffrey
Princeton
Jerry McCully wrote:
Dear All:
Next week we are going to try some seleno-Met labeled crystals.
We checked the literature to try to find out the peak wavelength
that has been used for SAD or MAD data collection. But they are
slightly different ( may be 50 ev) in different papers.
I guess this is due to the discrepancy between the fluorescence
scanning and the theoretical vaules of f' and f''.
When we collect the data, which wavelength should we use?
Should we trust the scanning results?
--
Engin Özkan
Post-doctoral Scholar
Laboratory of K. Christopher Garcia
Howard Hughes Medical Institute
Dept of Molecular and Cellular Physiology
279 Campus Drive, Beckman Center B173
Stanford School of Medicine
Stanford, CA 94305
ph: (650)-498-7111
