Using the unique ability of small-angle neutron scattering to resolve a hydrogen-rich surfactant from a deuterated membrane protein, the results of removing free surfactant from the equilibrium are revealed.

Preferred orientation of macromolecules is one of the major issues that are commonly encountered in obtaining isotropic cryo-EM maps. Here, a comprehensive examination was performed of how macromolecule orientations respond to changes in physical factors, such as freezing temperature, and chemical factors, such as the addition of surfactants, for a standard set of macromolecules, which provides insights into their behaviour on grids and can be utilized to address the preferred orientation problem in a systemic manner for any given macromolecule.