title: Deducing fast electron density changes in randomly orientated uncrystallized biomolecules in a pump-probe experiment.
abstract: We propose a method for deducing time-resolved structural changes in uncrystallized biomolecules in solution. The method relies on measuring the angular correlations of the intensities, when averaged over a large number of diffraction patterns from randomly oriented biomolecules in solution in a liquid solvent. The experiment is somewhat like a pump-probe version of an experiment on small angle X-ray scattering, except that the data expected by the algorithm are not just the radial variation of the averaged intensities. The differences of these correlation functions as measured from a photoexcited and dark structure enable the direct calculation of the difference electron density with a knowledge of only the dark structure. We exploit a linear relation we derive between the difference in these correlation functions and the difference electron density, applicable for small structural changes.
authors.affiliation: Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA.
authors.forename: K
authors.initials: K
authors.lastname: Pande
authors.affiliation: Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA.
authors.forename: P
authors.initials: P
authors.lastname: Schwander
authors.affiliation: Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA.
authors.forename: M
authors.initials: M
authors.lastname: Schmidt
authors.affiliation: Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA dksaldin@uwm.edu.
authors.forename: D K
authors.initials: DK
authors.lastname: Saldin
mesh_terms: D000465:Algorithms; D004583:Electrons; D007834:Lasers; D008962:Models, Theoretical; D008968:Molecular Conformation; D013997:Time Factors; D014961:X-Ray Diffraction / Q000379:methods*
keywords: X-ray free-electron laser; proteins; time-resolved