title: OPTESIM, a versatile toolbox for numerical simulation of electron spin echo envelope modulation (ESEEM) that features hybrid optimization and statistical assessment of parameters.
abstract: Electron spin echo envelope modulation (ESEEM) is a technique of pulsed-electron paramagnetic resonance (EPR) spectroscopy. The analyis of ESEEM data to extract information about the nuclear and electronic structure of a disordered (powder) paramagnetic system requires accurate and efficient numerical simulations. A single coupled nucleus of known nuclear g value (g(N)) and spin I=1 can have up to eight adjustable parameters in the nuclear part of the spin Hamiltonian. We have developed OPTESIM, an ESEEM simulation toolbox, for automated numerical simulation of powder two- and three-pulse one-dimensional ESEEM for arbitrary number (N) and type (I, g(N)) of coupled nuclei, and arbitrary mutual orientations of the hyperfine tensor principal axis systems for N>1. OPTESIM is based in the Matlab environment, and includes the following features: (1) a fast algorithm for translation of the spin Hamiltonian into simulated ESEEM, (2) different optimization methods that can be hybridized to achieve an efficient coarse-to-fine grained search of the parameter space and convergence to a global minimum, (3) statistical analysis of the simulation parameters, which allows the identification of simultaneous confidence regions at specific confidence levels. OPTESIM also includes a geometry-preserving spherical averaging algorithm as default for N>1, and global optimization over multiple experimental conditions, such as the dephasing time (tau) for three-pulse ESEEM, and external magnetic field values. Application examples for simulation of (14)N coupling (N=1, N=2) in biological and chemical model paramagnets are included. Automated, optimized simulations by using OPTESIM lead to a convergence on dramatically shorter time scales, relative to manual simulations.
authors: Department of Physics, Emory University, Atlanta, GA 30322-2430, USA.
authors: Li
authors: L
authors: Sun
authors: Jessica
authors: J
authors: Hernandez-Guzman
authors: Kurt
authors: K
authors: Warncke
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D003300:Copper / Q000737:chemistry; D003627:Data Interpretation, Statistical; D004578:Electron Spin Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods*; D004798:Enzymes / Q000737:chemistry; D004981:Ethanolamine Ammonia-Lyase / Q000737:chemistry; D006632:Histamine / Q000737:chemistry; D008958:Models, Molecular; D015233:Models, Statistical; D009587:Nitrogen Isotopes; D011208:Powders; D012475:Salmonella / Q000201:enzymology; D012984:Software; D013113:Spin Labels
chemical_list: D004798:Enzymes; D009587:Nitrogen Isotopes; D011208:Powders; D013113:Spin Labels; D003300:Copper; D006632:Histamine; D004981:Ethanolamine Ammonia-Lyase