Molecular-Level Interactions of Nanodisc-Forming Copolymers Dissected by EPR Spectroscopy

In this study, we focus on analyzing the non-covalent interaction patterns between three lipid-nanodisc-forming polymers and nitroxide radicals which are used as small organic tracer molecules. Besides the negatively charged polymers DIBMA and SMA(2:1), we characterize the solvation behavior of a new zwitterionic styrene/maleic amide sulfobetaine copolymer named SMA-SB. The used nitroxide spin probes vary in their respective chemical structure, allowing the report of different local micropolarities and nanoscopic regions by recording temperature-dependent continuous-wave electron paramagnetic resonance (CW EPR) spectra. In combination with dynamic light scattering (DLS) and electrophoretic light scattering (ELS) experiments, we are able to provide a nanoscopic interpretation of the dominant interaction patterns between the polymer and the chosen guest molecule.