Spin labeling and electron paramagnetic resonance (EPR) have been employed to study structure and dynamics of proteins. The surface polarity of four single cysteine mutants of the Zn-azurin in... Show moreSpin labeling and electron paramagnetic resonance (EPR) have been employed to study structure and dynamics of proteins. The surface polarity of four single cysteine mutants of the Zn-azurin in frozen solution were studied using 275 GHz EPR (J-band), with the advantage compared to 9 GHz (X-band) and 95 GHz (W-band) to allow differentiating between sites having small differences in polarity. The polarity/proticity profiles of the four mutants have been obtained and compared with data already reported in literature of spin labels in different solvents. In order to detect distances at the nm scale, azurin was used as a known model system for double electron-electron spin resonance. The conformation of the spin label linker was modelled. The model was found to be in good agreement with experimental results and can be extended to other proteins. The dynamics of the transient complex of Nostoc sp. PCC 7119 cytochrome f __ plastocyanin was investigated by NMR using the paramagnetic relaxation enhancements. The experimental distance restraints, used in docking calculations, are best interpreted by the presence of a dynamic ensemble of protein-protein orientations within the complex, rather than by a single, well-defined structure, and can be described with an encounter complex model. Show less
