Dear Colleagues, I think the following paper will be of particular interest for some aspects of this thread:-
J. Appl. Cryst. (1984). 17, 118-119 [ doi:10.1107/S0021889884011092 ] Optimum X-ray wavelength for protein crystallography U. W. Arndt Abstract: If the diffraction pattern from crystalline proteins is recorded with shorter wavelengths than is customary the radiation damage may be reduced and absorption corrections become less important. Best wishes, John Professor John R Helliwell DSc On Wed, Feb 15, 2012 at 11:55 PM, Bart Hazes <bha...@ualberta.ca> wrote: > 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 >>>> ******************************************* >> >> >> > --
