Structure and dynamics of biomacromolecules in solution: recent developments and future perspectives in SANS/SAXS and neutron spectroscopy

摘要

This French University Habilitation (“mémoire” to obtain the “Diplôme d’Habilitation à Diriger des Recherches”, DHDR) is divided into two parts: the first one deals with the results that I have obtained after my PhD thesis in 2003, the second one discusses open questions related to theseresults as well as mid- and long-term perspectives.Three different topics are presented in the result chapters: 1) a combination of small angle scattering (SAS) and nuclear magnetic resonance (NMR) for rigid-body modeling of biomacromolecular complexes, 2) the combined use of small angle X-ray (SAXS) and neutron (SANS) scattering for the study of unfolded proteins and 3) the study of biomacromolecular and solvent dynamics by neutron spectroscopy combining several instruments.Points 1) and 3) are discussed in great detail, both in the results and perspective sections, since they represent the most advanced projects of my research. Point 2) is dealt with more briefly in the results section, since few results are available so far. However, perspectives are discussed. Aspecial perspective chapter deals with applications on membrane proteins. Key publications for the different chapters are:Chapter 1: Gabel et al. (2006) A target function for quaternary structural refinement from small angle scattering and NMR orientational restraints. Eur. Biophys. J. 35(4), 313-327. Gabel et al. (2008) A structure refinement protocol combining NMR residual dipolar couplings and small angle scattering restraints. J. Biomol. NMR 41(4), 199-208.Chapter 2: Gabel et al. (2009) Quantitative Modelfree Analysis of Urea Binding to Unfolded Ubiquitin Using a Combination of Small Angle X-ray and Neutron Scattering. J. Am. Chem. Soc. 131(25), 8769-8771.Chapter 3: Gabel (2005) Protein dynamics in solution and powder measured by incoherent elastic neutron scattering: the influence of Q-range and energy resolution. Eur. Biophys. J. 31(1), 1-12. Gabel & Bellissent-Funel (2007) C-Phycocyanin Hydration Water Dynamics in the Presence of Trehalose: An Incoherent Elastic Neutron Scattering Study at Different Energy Resolutions. Biophys. J. 92(11), 4054-4063.The habilitation thesis is focused on methodological aspects and developments of small angle scattering and neutron spectroscopy. It is obvious that the approaches discussed here and their sophisticated levels of data analysis rely fundamentally on the quality of the sample, and inparticular on monodispersity (for SAS) and amount of material for spectroscopy. The paramount importance of good biochemistry and the use of complementary techniques for the characterization of samples can hardly be overestimated. They include, amongst others, gelfiltration, analytical ultracentrifugation, static and dynamic light scattering, NMR, etc. They are quite simply indispensable for doing good and accurate science with SAS, in particular in more complex systems (macromolecular complexes, membrane proteins …). If they are not presentedin more detail in this thesis, it is not out of ignorance of this fact but due to the lack of space.