Proteins are essential for organisms and participate in virtually every process within cells. Knowledge about the structure of proteins provides crucial information about their function in... Show moreProteins are essential for organisms and participate in virtually every process within cells. Knowledge about the structure of proteins provides crucial information about their function in biological mechanisms. In determining the structure of proteins with biophysical approaches, electron paramagnetic resonance (EPR) is rapidly gaining ground. The aim of this thesis is to provide insight in how broad the application of EPR can be to study proteins, in particular those which are difficult if not impossible to study with other approaches. The focus of this thesis is to investigate the aggregation and misfolding of intrinsically disordered proteins and to determine the structure of disordered parts of proteins with EPR. Specifically, the amyloid β (Aβ) peptide, the α-synuclein (αS) protein, and the light-harvesting protein CP29 are studied. Show less
A spectrometer for Electron Paramagnetic Resonance (EPR), operating at the very high microwave frequency of 275 GHz in both continuous wave (cw) and pulsed mode, is described and its capabilities... Show moreA spectrometer for Electron Paramagnetic Resonance (EPR), operating at the very high microwave frequency of 275 GHz in both continuous wave (cw) and pulsed mode, is described and its capabilities are illustrated. A superconducting magnet provides the magnetic field up to 12 Tesla and experiments are possible between room temperature and 5 K. The system utilizes pseudo-optical techniques to minimize microwave losses and a single-mode resonator is used to maximize the microwave field at the sample position. The material under study can also be subjected to a radiofrequency radiation field to enable Electron Nuclear Double Resonance (ENDOR) experiments. Technical details of the design and the operation are presented. First results are discussed which demonstrate the increased sensitivity and resolution compared to experiments at lower microwave frequencies. These concern various materials, ranging from semi-conductors to proteins, including an aqueous solution of a proxyl radical at room temperature. ENDOR performance is illustrated with data from a sample of zinc-germanium-phosphide (ZnGeP2) doped with Manganese (Mn). Separate chapters cover experiments on the organic semiconductor P3HT and the observation of Dynamic Nuclear Polarization (DNP) in zinc oxide (ZnO). Show less
