Determination of Electron Spin Resonance Static and Dynamic Parameters by Automated Fitting of the Spectra

The understanding of the functional role of the lipid diversity in biological membranes is a major challenge. Lipid models have been developed to address this issue by using lipid mixtures generating liquid-ordered (Lo)/liquid-disordered (Ld) immiscibility. The present study examined mixtures comprising Egg sphingomyelin (SM), cholesterol (chol) and phosphatidylcholine (PC) either containing docosahexaenoic (PDPC) or oleic acid (POPC). The mixtures were examined in terms of their capability to induce phase separation at the micron- and nano-scales. Fluorescence microscopy, electron spin resonance (ESR), X-ray diffraction (XRD) and calorimetry methods were used to analyze the lateral organization of the mixtures. Fluorescence microscopy of giant vesicles could show that the temperature of the micron-scale Lo/Ld miscibility is higher for PDPC than for POPC ternary mixtures. At 37°C, no micron-scale Lo/Ld phase separation could be identified in the POPC containing mixtures while it was evident for PDPC. In contrast, a phase separation was distinguished for both PC mixtures by ESR and XRD, indicative that PDPC and POPC mixtures differed in micron vs nano domain organization. Compared to POPC, the higher line tension of the Lo domains observed in PDPC mixtures is assumed to result from the higher difference in Lo/Ld order parameter rather than hydrophobic mismatch.

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“…The ESR parameters have been determined by least-squares spectral fittings as previously reported [41] (see also www.esr-spectsim-softw.fr).…”

Section: Esr Methodsmentioning

confidence: 99%

Docosahexaenoic acid promotes micron scale liquid-ordered domains. A comparison study of docosahexaenoic versus oleic acid containing phosphatidylcholine in raft-like mixtures

Georgieva

Chachaty

Hazarosova

et al. 2015

Biochimica et Biophysica Acta (BBA) - Biomembranes

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“…Numerical integration of the EPR absorbance on the whole orientation sphere being time-consuming, interpretation and modeling of powder EPR spectra have been often treated using perturbation theory. Examples of automated fitting of EPR powder spectra for S ϭ 1 2 species, based on high order perturbation calculations, were given in a recent paper (10). In case of higher spin values (S Ͼ 1 2 ), perturbation calculations are based on the relative importance of the zero field splitting (ZFS) and of the Zeeman splitting.…”

Section: Introductionmentioning

confidence: 99%

Modeling EPR Powder Spectra Using Numerical Diagonalization of the Spin Hamiltonian

Morin¹,

Bonnin

1999

Journal of Magnetic Resonance

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“…22). In the case of free radicals having several hyperfine interactions, we have shown that the EPRPOWDERFIT program enables to deduce the parameters of an effective Hamiltonian comprising the Zeeman electronic term and several hyperfine interaction terms.…”

Section: Resultsmentioning

confidence: 99%

Electron paramagnetic resonance: Nonlinear least-squares fitting of the Hamiltonian parameters from powder spectra with the Levenberg-Marquardt algorithm

Soulié

Berclaz

2005

Appl. Magn. Reson.

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In many instances, the deduction of spectroscopic parameters from electron paramagnetic resonance spectra depends on spectrum simulation and parameter optimization. We have developed two software packages based on the approximate formulae of Iwasaki for the calculation of line positions and on the Levenberg-Marquardt algorithm for nonlinear least-squares optimization. Our software applies to systems having an anisotropicg-tensor and an arbitrary number of hyperfine interactions with nuclei. They are written in the FORTRAN 77 programming language. At present, neither the nuclear quadrupolar interaction nor the nuclear Zeeman interaction terms are handled. The programs CRISAJU and EPRPOWDERFIT apply to the cases of single crystals and powders, respectively. For use in the latter, thanks to the software ODYSSEE which implements automatic differentiation of algorithms, an ancillary subroutine, which contributes to the performance of the optimization, was created automatically

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Determination of Electron Spin Resonance Static and Dynamic Parameters by Automated Fitting of the Spectra

Cited by 15 publications

References 27 publications

Docosahexaenoic acid promotes micron scale liquid-ordered domains. A comparison study of docosahexaenoic versus oleic acid containing phosphatidylcholine in raft-like mixtures

Docosahexaenoic acid promotes micron scale liquid-ordered domains. A comparison study of docosahexaenoic versus oleic acid containing phosphatidylcholine in raft-like mixtures

Modeling EPR Powder Spectra Using Numerical Diagonalization of the Spin Hamiltonian

Electron paramagnetic resonance: Nonlinear least-squares fitting of the Hamiltonian parameters from powder spectra with the Levenberg-Marquardt algorithm

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