Precise Control of Neutron Contrast in Surfactant Micelles Provides Platform for Membrane Structure Studies

09/29/2017

Micelle-forming detergents are important tools used to solubilize and stabilize membrane proteins in solution for in vitro structural investigations. However, the detergents can cause significant residual signal that interferes with interpreting the structural data of membrane proteins during small-angle neutron scattering (SANS). Researchers have developed a framework for removing detergent contributions in future SANS experiments by eliminating the contrast between micelle core and shell. The plot shows the varied neutron scattering intensity (y axis) of a typical micelle solution (red) versus a the stable scattering intensity of a blend of natural micelles and those containing deuterated alkyl chain tails (blue). [Reprinted from Oliver, R. C., et al. 2017. DOI: 10.1021/acs.jpclett.7b02149]

Scientists in this study have successfully demonstrated the ability to manipulate the neutron contrast of detergent micelles by incorporating a similar detergent with deuterium-labelled alkyl chains. The presence of excess detergent micelle scattering often has a detrimental influence on scattering data obtained for membrane protein–detergent complexes. Isolation of the scattering signal from the protein of interest can be accomplished by eliminating all scattering from the detergent. This approach enabled determination of the overall structure and oligomeric state of a small membrane protein enzyme.

Instruments and Facilities

Small angle neutron scattering (SANS): Bio-SANS beamline (CG3) of the High-Flux Isotope Reactor at Oak Ridge National Laboratory (ORNL). Recorded scattering data using MantidPlot software. Neutron contrast studies: ModULes for the Analysis of Contrast (MULCh) Variation Data at the University of Sydney.

Funding Acknowledgements

Neutron scattering studies at CG-3 Bio-SANS instrument at the High-Flux Isotope Reactor (HFIR), Oak Ridge National Laboratory (ORNL), sponsored by the Office of Biological and Environmental Research (OBER) and Office of Basic Energy Sciences (OBES) Scientific User Facilities Division (SUF), U.S. Department of Energy (DOE) Office of Science. Work benefited from use of the SasView application, originally developed under National Science Foundation (NSF) Award DMR-0520547. SasView contains code developed with funding from the European Union’s Horizon 2020 Research and Innovation Programme under the SINE2020 project, Grant Agreement No 654000. Manuscript authored by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with DOE. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan.

References

Oliver, R. C., et al. “Designing Mixed Detergent Micelles for Uniform Neutron Contrast.” The Journal of Physical Chemistry Letters 8(20), 5041–5046 (2017). [DOI:10.1021/acs.jpclett.7b02149].