Biological Fiber Diffraction and Scattering at the Advanced Photon Source

Fiber diffraction and scattering can be used to extract structural information from partially ordered systems that are in general too large to be studied by conventional macromolecular crystallographic techniques. In dynamic systems such as muscle, one can study changes in the structure on the physiologically relevant millisecond time scale providing one has enough X-ray flux.

Macromolecular small angle scattering experiemtns can be used for estimation of Rg (radius of gyration) and Pr (radial density distribution function) to test hypotheses concerning macromolecular conformation in solution. Third generation storage rings such as the Advanced Photon Source (APS) ,the ESRF, France, and Spring-8, Japan can be outstanding X-ray sources for these kinds of experiments. The combination of high flux (~ 10^13 photons/s, small source sizes ( ~100 micrometers) and extremely small source divergence (~ 40 micro-radians) can yield diffraction patterns of exceptional quality from small specimens.

These same characteristics allow acquisition of solution scattering profiles with good statistics from dilute specimens in short periods of time with low instrumental background enabling high throughput and time resolved experiments. I will present recent results from the BioCAT undulator based beamline (a NIH-supported Research Center) at the APS which shows the promise of these technologies for biological research.

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