Joint Use of SAXS and SANS

Jill Trewhella

While there are common underlying principals and methods for extracting structural information from neutron or X-ray scattering data, there are important differences in the way X-rays and neutron are produced and in how they interact with matter that can be capitalized upon. X-ray sources are inherently more intense than neutron sources and hence require smaller samples and offer greater potential in time-resolved studies. On the other hand, there can be large isotope effects in neutron scattering that facilitate contrast variation experiments, particularly using deuterium substitution that changes the scattering density of a component with changing its elemental composition. This presentation will describe how one can combine the information from X-ray and neutron scattering experiments with information from NMR, crystallography and other biophysical tools to advance our understanding of the molecules of life and how they work in concert to achieve their specialised functions. Importantly, a 3D structure derived from solution scattering data does not always lead to a uniquely determined solution, and there are inherent limits to the information content of a scattering profile beyond the issue of resolution. The inclusion of neutron scattering data with contrast variation along with data from other complementary techniques can dramatically reduce the ambiguity in models from a single scattering data profile. We have used these approaches to study protein complexes involved in signalling and regulation. Examples will be discussed that highlight the potential of the utilisation of hybrid experimental data from our studies of proteins controlling bacterial responses to environmental signals (1), heart muscle action (2,3), and a potential host-virus response mechanism (4).

1. Whitten, A. E., Jacques, D. A., Hammouda, B., Hanley, T., King, G. F., Guss, J. M., Trewhella, J. and Langley, D. B. The Structure of the Sda-KinA Complex Suggests an Allosteric Mechanism of Histidine Kinase Inhibition, J. Mol. Biol. 368, 407-420, 2007.
2. Whitten, A. E, Jeffries, C. M., Harris, S. P., and Trewhella, J. Cardiac Myosin Binding Protein-C Decorates F-actin: Implications for Cardiac Function, Proc. Natl Acad. Sci. U.S.A. 105, 18360-18365, 2008.
3. Lu, Y., Kwan, A. H., Jeffries, C. M., Guss, J. M. and Trewhella, J. The Motif of Human Cardiac Myosin Binding Protein C is Required for its Ca2+-Dependent Interaction with Calmodulin, J. Biol. Chem. 287, 31596-31607, 2012.
4. Taylor, J. E., Chow, J. Y. H., Jeffries, C. M., Kwan, A. H., Duff, A. P., Hamilton, W. A. and Trewhella, J. Calmodulin Binds a Highly Extended HIV-1 MA Protein that Refolds upon its Release, Biophys. J.103, 1-9, 2012.

Useful additional references

5. Whitten, A. E., Cai, S., and Trewhella, J. MULCh: ¬ModULes for the Analysis of Small-angle Neutron Contrast Variation Data from Biomolecular Complexes, J. Appl. Cryst. 41, 222-226, 2008.
6. Jacques, D. A., Guss, J. M., Svergun, D. and Trewhella J. Publication Guidelines for Structural Modelling of Small-Angle Scattering Data from Biomolecules in Solution, Acta Cryst. D68, 620-626, 2012.
7. Jacques, D. A., and Trewhella, J. Small-angle Scattering for Structural Biology; Expanding the Frontier While Avoiding the Pitfalls, Protein Science 19, 642-657, 2010. Highlighted in the journal's 'in this issue'.

Date/time: Saturday, 1 November 2014, 9:00