Dear Jacob: I think the main impediment is that more diffuse scattering, for example, isn't as easy to model as Bragg crystalline diffraction. But it is definitely useful.
One example is tRNA: http://scripts.iucr.org/cgi-bin/paper?am0009 Acta Cryst. (1994). D50, 210-218 [ doi:10.1107/S0907444993011692 ] Analysis of diffuse scattering from yeast initiator tRNA crystals A. R. Kolatkar, J. B. Clarage and G. N. Phillips Jnr Abstract: Yeast initiator tRNA crystals exhibit strong X-ray diffuse scattering. This scattering can be used to extract information about lattice-coupled and intramolecular motions in the crystals. The amplitudes and correlation distances of these motions can be estimated by calculating the diffuse scattering and comparing the results with the observed scattering. Results indicate that both anisotropic, lattice-coupled motions as well as short-range correlated local disorder in the anticodon arm contribute to the overall disorder in the crystals. These types of motions can be correlated with aspects of tRNA function. This additional information complements the results from analysis of crystallographic data and provides a more detailed picture of the structure and dynamics of the molecule. The degree to which the methodology presented here can account for the observed diffuse scattering from tRNA represents a significant step forward in the ability to use this conventionally discarded information, and encourages the ultimate extension of these ideas to a wide variety of macromolecular systems. This is an example I am familiar with, but I am sure there are others. Bill On Jan 20, 2010, at 9:47 AM, Jacob Keller wrote: > Dear Crystallographers, > > One can see from many posts on this listserve that in any given x-ray > diffraction experiment, there are more data than merely the diffraction > spots. Given that we now have vastly increased computational power and data > storage capability, does it make sense to think about changing the paradigm > for model refinements? Do we need to "reduce" data anymore? One could imagine > applying various functions to model the intensity observed at every single > pixel on the detector. This might be unneccesary in many cases, but in some > cases, in which there is a lot of diffuse scattering or other phenomena, > perhaps modelling all of the pixels would really be more true to the > underlying phenomena? Further, it might be that the gap in R values between > high- and low-resolution structures would be narrowed significantly, because > we would be able to model the data, i.e., reproduce the images from the > models, equally well for all cases. More information about the nature of the > underlying macromolecules might really be gleaned this way. Has this been > discussed yet? > > Regards, > > Jacob Keller > > ******************************************* > Jacob Pearson Keller > Northwestern University > Medical Scientist Training Program > Dallos Laboratory > F. Searle 1-240 > 2240 Campus Drive > Evanston IL 60208 > lab: 847.491.2438 > cel: 773.608.9185 > email: j-kell...@northwestern.edu > *******************************************
