Small-angle X-ray and neutron scattering (SAXS/SANS)

Principal Investigator: Frank Gabel

Group members involved: Viviam Moura da Silva, Eric Girard, Bruno Franzetti


Biological small-angle scattering (SAS) provides low-resolution structural information on bio-macromolecules in solution on a nanometer length-scale. The general dimensions of the molecules (radii of gyration, oligomeric state, molecular weight and interaction of different partners) can be obtained as basic information. More sophisticated approaches include ab initio shape analysis or rigid-body modeling of complexes composed of subunits with known high-resolution structure.

Modeling techniques and software have witnessed a tremendous progress over the last 20 years. The most recent generation combines small-angle X-ray (SAXS) and/or neutron (SANS) scattering with structural restraints from complementary techniques such as crystallography, electron microscopy and NMR.

While the majority of experiments are carried out by SAXS, SANS in combination with contrast variation (H2O/D2O ratio in the solvent) and labeling schemes (deuteration of subunits) allows to focus specifically on subunits within a complex in situ by masking the contribution of the others.

Importantly, SAXS/SANS are solution techniques and therefore allow to follow macromolecular conformational changes by varying buffer composition, temperature, pressure, and by titrating ligands and binding partner in vitro.

Research projects and collaborations:

  • Low-resolution structural study of the large aminopeptidase TET and the unfoldase PAN by SAXS/SANS (ELMA Group, IBS)
  • Hydration effects and their impact on SAXS/SANS curves and modeling (ELMA Group, IBS)
  • Methodological developments of SAXS/SANS NMR hybrid approaches. Collaborations with the Sattler NMR group at the Chemistry Department, TUM Munich, Germany, and the Carlomagno NMR group at Birmingham University, UK.


  • ANR Grant JCJC "Hydrosas" (2011-2015)
  • ANR Grant PRCI "PROTstretch" (2015-2019)
  • ANR Grant PRC "DeepSAXS" (2021-2025)


  • Gabel, F., Engilberge, E., Schmitt, E., Thureau, A., Mechulam, Y., Pérez, J. and Girard. E. (2022) Medical contrast agents as promising tools for biomacromolecular SAXS experiments. Acta D78, 1120-1130.
  • Ibrahim, Z., Martel, A., Moulin, M., Kim, H.S., Härtlein, M., Franzetti, B. and Gabel, F. (2017) Time-resolved neutron scattering provides new insight into protein substrate processing by a AAA+ unfoldase. Sci. Rep. 7, 40948.
  • Hennig, J., Militti, C., Popowicz, G.M., Wang, I., Sonntag, M., Geerlof, A., Gabel, F., Gebauer, F. and Sattler, M. (2014) Structural basis for the assembly of the Sxl-Unr translation regulatory complex. Nature 515(7526), 287-290.
  • Appolaire A, Girard E, Colombo M, Durá MA, Moulin M, Härtlein M, Franzetti B, Gabel F. (2014) Small-angle neutron scattering reveals the assembly mode and oligomeric architecture of TET, a large, dodecameric aminopeptidase. Acta Crystallogr. D70(Pt 11), 2983-2993.
  • Lapinaite, A., Simon, B., Skjaerven, L., Rakwalska-Bange, M., Gabel, F. and Carlomagno, T. (2013) The structure of the box C/D enzyme reveals regulation of RNA methylation. Nature 502(7472), 519-523.

A complete list of publications can be found here.