Diffracted intensity goes up by the cube of the wavelength, but so does
absorption and I don't know exactly about radiation damage. One
interesting point is that on image plate and CCD detectors the signal is
also proportional to photon energy, so doubling the wavelength gives 8
times diffraction intensity, but only 4 times the signal on integrating
detectors (assuming the full photon energy is captured). So it would be
interesting to see how the equation works out on the new counting
detectors where the signal does not depend on photon energy. Another
point to take into account is that beamlines can have different optimal
wavelength ranges. Typically, your beamline guy/gal should be the one to
ask. Maybe James Holton will chime in on this.
Bart
On 12-02-15 04:21 PM, Jacob Keller wrote:
Well, but there is more scattering with lower energy as well. The
salient parameter should probably be scattering per damage. I remember
reading some systematic studies a while back in which wavelength
choice ended up being insignificant, but perhaps there is more info
now, or perhaps I am remembering wrong?
Jacob
On Wed, Feb 15, 2012 at 5:14 PM, Bosch, Juergen<jubo...@jhsph.edu> wrote:
No impact ? Longer wavelength more absorption more damage. But between the
choices given no problem.
Spread of spots might be better with 1.0 versus 0.9 but that depends on your
cell and also how big your detector is. Given your current resolution none of
the mentioned issues are deal breakers.
Jürgen
......................
Jürgen Bosch
Johns Hopkins Bloomberg School of Public Health
Department of Biochemistry& Molecular Biology
Johns Hopkins Malaria Research Institute
615 North Wolfe Street, W8708
Baltimore, MD 21205
Phone: +1-410-614-4742
Lab: +1-410-614-4894
Fax: +1-410-955-3655
http://web.mac.com/bosch_lab/
On Feb 15, 2012, at 18:08, "Jacob Keller"<j-kell...@fsm.northwestern.edu>
wrote:
I would say the better practice would be to collect higher
multiplicity/completeness, which should have a great impact on maps.
Just watch out for radiation damage though. I think the wavelength
will have no impact whatsoever.
JPK
On Wed, Feb 15, 2012 at 4:23 PM, Seungil Han<shan06...@gmail.com> wrote:
All,
I am curious to hear what our CCP4 community thoughts are....
I have a marginally diffracting protein crystal (3-3.5 Angstrom resolution)
and would like to squeeze in a few tenth of angstrom.
Given that I am working on crystal quality improvement, would different
wavelengths make any difference in resolution, for example 0.9 vs. 1.0
Angstrom at synchrotron?
Thanks.
Seungil
--------------------------------------------
Seungil Han, Ph.D.
Pfizer Inc.
Eastern Point Road, MS8118W-228
Groton, CT 06340
Tel: 860-686-1788, Fax: 860-686-2095
Email: seungil....@pfizer.com
--
*******************************************
Jacob Pearson Keller
Northwestern University
Medical Scientist Training Program
email: j-kell...@northwestern.edu
*******************************************
