Ongoing cell research aims at a coherent picture of the interactions and dynamical properties of proteins inside living cells under physiological conditions. In this context, red blood cells are exceptional, as they are highly specialized and relatively simple in composition, the main macromolecular component being haemoglobin.
We have used high-resolution quasielastic neutron scattering to study the motions of haemoglobin in whole red blood cells. Neutron scattering is exceptionally useful as measurements on living cells are possible without damaging these highly sensitive specimens. We find that the diffusion of haemoglobin in the crowded environment of a red blood cell can be described using concepts from colloid physics. Furthermore, interfacial hydration water has a large influence on protein diffusion. This work demonstrates how neutron scattering allows the measurement of internal protein dynamics and global macromolecular diffusion in whole cells, thereby contributing to a better understanding of cellular phenomena at the molecular level.