title: Post-processing of EPR spectra by convolution filtering: calculation of a harmonics' series and automatic separation of fast-motion components from spin-label EPR spectra.
abstract: This communication reports on post-processing of continuous wave EPR spectra by a digital convolution with filter functions that are subjected to differentiation or the Kramers-Krönig transform analytically. In case of differentiation, such a procedure improves spectral resolution in the higher harmonics enhancing the relative amplitude of sharp spectral features over the broad lines. At the same time high-frequency noise is suppressed through filtering. These features are illustrated on an example of a Lorentzian filter function that has a principal advantage of adding a known magnitude of homogeneous broadening to the spectral shapes. Such spectral distortion could be easily and accurately accounted for in the consequent least-squares data modeling. Application examples include calculation of higher harmonics from pure absorption echo-detected EPR spectra and resolving small hyperfine coupling that are unnoticeable in conventional first derivative EPR spectra. Another example involves speedy and automatic separation of fast and broad slow-motion components from spin-label EPR spectra without explicit simulation of the slow motion spectrum. The method is illustrated on examples of X-band EPR spectra of partially aggregated membrane peptides.
authors.affiliation: Department of Chemistry, North Carolina State University, Raleigh, NC 27695-8204, USA. Alex_Smirnov@ncsu.edu
authors.forename: Alex I
authors.initials: AI
authors.lastname: Smirnov
mesh_terms: D003198:Computer Simulation; D003497:Cyclic N-Oxides; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D016018:Least-Squares Analysis; D012815:Signal Processing, Computer-Assisted; D013113:Spin Labels; D013229:Stearic Acids / Q000737:chemistry*
chemical_list: D003497:Cyclic N-Oxides; D013113:Spin Labels; D013229:Stearic Acids; C031183:stearic acid; C051599:4-(N,N,N-trimethylamino)-2,2,6,6-tetramethylpiperidine-1-oxyl