There is ALWAYS anomalous scattering. You do not have be at the
absorption edge to get it. The question is just whether your experiment
is good enough to detect it.
So your question of "overlapping" always has the answer Yes, but I would
remove the words "absorption edge" from your question.
Jim
On Thu, 25 Sep 2008, Michael Jackson wrote:
> Hello, I had recently collected and solved the phases for a protein
> molecule using CCP4 and the ShelXCDE SAD method in it. What I was
> wondering was that the peaks for the three SE incorporated methionines
> are there as expected, but there is one peak scored roughly as the
> second largest where the disulfide is based on ShelXD's HA search
> algorithm. This data was collected at 0.97960 Angstroms which is close
> to the peak Xray absorption edge for Se but does anyone know if a
> disulfide has any absorption edge overlapping here?
>
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