Electron Paramagnetic Resonance Spectra Simulation Directly from Molecular Dynamics Trajectories of a Liquid Crystal with a Doped Paramagnetic Spin Probe

We report simulation of EPR spectra directly and entirely from trajectories generated from molecular dynamics simulations. Results are reported for a model 3 beta-DOXYL-5 alpha-cholestane spin probe in a coarse-grained solvent representing a 5CB nematic host. The results are in excellent agreement with the experimental spectra. The calculated order parameters associated with the paramagnetic probe show strong correlation with the order parameter of 5CB mesogens and are in agreement with those reported in the literature. Simulation of EPR spectra entirely from molecular dynamics of real structures provides direct correlation between molecular motions and the features observed in the spectra, allowing unambiguous interpretation of the spectra. This method opens the possibility for computer engineering'' of spin-labeled materials with the desired properties, such as spin-labeled proteins, prior to experiment.