Fast and Angström-resolution AFM to visualise conformational change in biomolecules

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Atomic Force Microscopy (AFM) basically acts as a miniature blind man's stick ('cantilever') following the contours of a sample surface, and line by line reconstructing a three-dimensional representation of the surface topography. This line-by-line scanning is a fundamental difference from other, more common microscopy techniques and a main reason why it generally takes minutes to complete a single image. AFM is unique in combining sub-molecular resolution imaging with the ability to operate in liquids. For high-resolution imaging of biological samples, molecules are generally adsorbed on a hard surface, which is the only compromise compared to physiological conditions. Membrane proteins are samples of particular interest, since they represent more than 50% of modern drug targets and therefore are of major pharmaceutical importance. Their function as molecular nanomachines is determined by Angstrom-sized structural ('conformational') changes occurring at millisecond time scales. For applications in future healthcare and for basic scientific understanding, the crucial question is how molecular structure and changes in this structure relate to the biological function of membrane proteins. This project combines high-resolution AFM techniques (that have yielded atomic resolution!) with fast scanning, to obtain images of membrane proteins with Angstrom spatial and millisecond temporal resolution. This will enable us to visualise conformational changes in real time and observe biomolecules at work. This will be demonstrated on bacteriorhodopsin, a light-driven molecular machine that pumps protons through the cell membrane.