Membranes are the most important biological interface. They separate the living cell from the outer world. Membranes fulfill a variety of different functions including alimentation and protection of the cell. Besides the interest in fundamental science, the study of cell membranes is motivated by applications in nanotechnology and bio-inspired materials science. Trans-membrane proteins and membrane-associated proteins are the first to be attacked in many infectious diseases. However, and despite the fact that membranes have been studied for decades, our understanding of functioning of membranes and in particular of membrane proteins is still qualitative. Very few processes could be revealed on a molecular level. We developed a technique to study functioning of membrane embedded proteins in situ and under realistic, physiological conditions. The technique is capable to access the small nanometer length scales and fast dynamics of picoseconds to microseconds involved at the same time. The basic knowledge gained from our research has the potential to support research into better treatments for infectious diseases, and the development of more advanced and smart materials such as biosensors. The outcome of this research can eventually be used to impact on proteins, to for instance suppress protein function that leads to cell damage or death. Transport of drugs through a cell membrane can be enhanced. Membranes with tailored properties can be fabricated for use as highly efficient biosensors.

We use inelastic neutron scattering to study functioning of membrane-embedded proteins. This technique has only recently been developed and applied to the study of protein-protein interactions in a biological membrane. Understanding protein communication and concerted protein dynamics on the function of a biological membrane could have a dramatic impact on the way we model and understand biological systems. In the past, molecular motions in biological materials were mostly considered as to be thermally activated motions in local environments. On a molecular level, the different constituents of a cell membrane, such as proteins and peptides, were expected to move independently from each other. But interdependency and collectivity seem to be fundamental properties of biological materials. In previous experiments we found evidence for an interaction between the constituents in a biological membrane, in particular between membrane embedded proteins. This interaction may lead to effective communication, and concerted protein dynamics and function. This observation may be relevant to understand the way proteins work in a cell. In particular coupled proteins may work more efficiently than isolated entities. The investigation of complicated proteins in the way we propose is certainly one of the challenges in biological physics today. The corresponding experiments can only be conducted at the latest generation of neutron sources, because very high intensity is necessary to make the very small signals visible.