title: Simulating electron spin resonance spectra of nitroxide spin labels from molecular dynamics and stochastic trajectories.
abstract: Simulating electron spin resonance spectra of nitroxide spin labels from motional models is necessary for the quantitative analysis of experimental spectra. We present a framework for modeling the spin label dynamics by using trajectories such as those from molecular dynamics (MD) simulations combined with stochastic treatment of the global protein tumbling. This is achieved in the time domain after two efficient numerical integrators are developed: One for the quantal dynamics of the spins and the other for the classical rotational diffusion. For the quantal dynamics, we propagate the relevant part of the spin density matrix in Hilbert space. For the diffusional tumbling, we work with quaternions, which enables the treatment of anisotropic diffusion in a potential expanded as a sum of spherical harmonics. Time-averaging arguments are invoked to bridge the gap between the smaller time step of the MD trajectories and the larger time steps appropriate for the rotational diffusion and/or quantal spin dynamics.
authors.affiliation: Department of Physics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Deniz
authors.initials: D
authors.lastname: Sezer
authors.forename: Jack H
authors.initials: JH
authors.lastname: Freed
authors.forename: Benoît
authors.initials: B
authors.lastname: Roux
mesh_terms: D003198:Computer Simulation; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D008956:Models, Chemical; D008958:Models, Molecular; D015233:Models, Statistical; D009569:Nitric Oxide / Q000737:chemistry*; D013113:Spin Labels; D013269:Stochastic Processes
chemical_list: D013113:Spin Labels; D009569:Nitric Oxide