Transmission electron microscopy: Studies of soft materials in chemistry and biology

Various studies were performed with transmission electron microscopy (TEM) as the main technique. The electron microscope is a powerful tool that allows us to work at scales of nanometers and smaller. Whether the observed structures are the effect of molecular design or influenced by sample preparation can be hard to distinguish. The first study addresses the three most common TEM methods, drying, staining and cryo-fixation, in terms of interpretation, artefacts and information that can be obtained. All three techniques were used in the next study. The mixing of a solvent and non-solvent to induce aggregation is common practice in soft matter chemistry. Bowl-shaped aggregates resulting from solvent mixing were characterized in detail, demonstrating their nature and the mechanism of their formation. In another more biological study, TEM was used to gain new insights in complex NDH-1 of the cyanobacterium Thermosynechococcus elongates. NdhP was located in the large complex by fusion with Green Fluorescent Protein and the subsequent analysis of the purified complex by single particle averaging. The main research was on ribosome dimerization in Lactococcus lactis. L. lactis has a different and much more common mechanism of dimerization than the well-studied bacterium Escherichia coli. Dimerization inhibits ribosome activity and is in L. lactis induced by protein HPFlong. The structure of HPFlong in complex with the dimeric 100S ribosome was solved. It allowed new insights in ribosome dimerization and inactivation by HPFlong showing a different mechanism of translation control to what was previously known.