*** For details on how to be removed from this list visit the ***
*** CCP4 home page http://www.ccp4.ac.uk ***
Using a multiple wavelength structure determination with radiation
around the K
edge of Sulphur or Phosphorus (in the U.S we spell them Sulfur but not
Fosforus) would certainly avoid a lot of ?sample manipulation' and speed up
genomics-type research but there are huge experimental problems.
An experiment I was involved in many years ago involved used Cs L III edge
radiation. Our count rates dropped by a factor of 40 tuning from 1.5 to 2.5
Ang. (air and sample absorption, detector efficiency etc.)
To use P (2.14 Kev= 5.8 Ang approx.) or S (2.47 Kev = 5 Ang. approx.) these
problems would be much worse.
To do a good job of data collection you would need to work on
minimizing sample
and sample mount absorption, sample to detector absorption (vacuum path,
windowless detector?) and detector efficiency (present CCD's are better the
shorter the wavelength) and lots of stuff I can't think of.
Also your data resolution would be limited. At full backscattering (2theha=180
deg. You get lambda/2 resolution i.e 2.9 for P and 2.5 for S) and this would
entail a detector which completely wrapped around the crystal!!.
I don't want to discourage you but this is a major project for a dedicated
graduate student and an advisor who already has tenure.
James Phillips (not Fillips)
Duke University Medical Center
Quoting Richard Gillilan <[EMAIL PROTECTED]>:
*** For details on how to be removed from this list visit the ***
*** CCP4 home page http://www.ccp4.ac.uk ***
I know that some work has been done on phasing from Sulfur (2.47
keV). Does anyone know of work on
phasing from P, Cl, Ar, K, or Ca?
Are there any very important systems that might benefit from MAD in
range 2-5 keV?
Richard Gillilan
MacCHESS
Cornell
