Nonlinear-Least-Squares Analysis of Slow-Motion EPR Spectra in One and Two Dimensions Using a Modified Levenberg–Marquardt Algorithm

Budil, David E.; Lee, Sanghyuk; Saxena, Sunil; Freed, Jack H.

doi:10.1006/jmra.1996.0113

Cited by 859 publications

(1,038 citation statements)

References 21 publications

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“…2b) summarize the program used in the simulations shown here. This program, the Multi-Component EPR Fitting program was developed by Christian Altenbach (Althenbach 2017) and is based on the MOMD (microscopic order and macroscopic disorder) theory developed by Freed and coworkers (Schneider and Freed 1989;Budil et al 1996).…”

Section: Andmentioning

confidence: 99%

“…As the parameters used have been extensively discussed in earlier publication (Schneider and Freed 1989;Budil et al 1996), only a few of the most relevant points for performing the simulations will be mentioned here. The parameters are obtained through nonlinear least squares fitting of the experimental ESR signal based on the stochastic Liouville equation (Freed 1976).…”

Section: Andmentioning

confidence: 99%

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Structural insights on biologically relevant cationic membranes by ESR spectroscopy

et al. 2017

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Cationic bilayers have been used as models to study membrane fusion, templates for polymerization and deposition of materials, carriers of nucleic acids and hydrophobic drugs, microbicidal agents and vaccine adjuvants. The versatility of these membranes depends on their structure. Electron spin resonance (ESR) spectroscopy is a powerful technique that employs hydrophobic spin labels to probe membrane structure and packing. The focus of this review is the extensive structural characterization of cationic membranes prepared with dioctadecyldimethylammonium bromide or diC14-amidine to illustrate how ESR spectroscopy can provide important structural information on bilayer thermotropic behavior, gel and fluid phases, phase coexistence, presence of bilayer interdigitation, membrane fusion and interactions with other biologically relevant molecules.

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Section: Andmentioning

confidence: 99%

Section: Andmentioning

confidence: 99%

Structural insights on biologically relevant cationic membranes by ESR spectroscopy

et al. 2017

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“…The computation of the EPR spectra was performed according to a well-known procedure reported by Budil et al 2 …”

Section: Synthesis Of Polystyrene-co-poly(p-hydrazinostyrene) (Ps-psnmentioning

confidence: 99%

EPR Study of Spin Labeled Brush Polymers in Organic Solvents

Xia

Burts

et al. 2011

J. Am. Chem. Soc.

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Materials. All reagents were obtained from commercial venders and used as received unless otherwise noted. Styrene was distilled over CaH 2 before use; p-chlorostyrene was passed through a plug of neutral alumina. NB-PLA MMs were prepared according procedures we previously published. 1Characterizations. 1 H and 13 C NMR spectra were recorded in CDCl 3 using a Varian Mercury 300 or Varian Inova 500 spectrometer. Chemical shifts are reported in ppm relative to CDCl 3 (δ = 7.27).High-resolution mass spectra were obtained using an Agilent 6200 series accurate-mass time-offlight (TOF) LC/MS.Gel permeation chromatography (GPC) was carried out in THF on two PLgel 10 µm mixed-B LS columns (Polymer Laboratories) connected in series with a DAWN EOS multiangle laser light scattering (MALLS) detector and an Optilab DSP differential refractometer (both from Wyatt Technology). No calibration standards were used, and a dn/dc value of 0.05 mL/g was calculated for PLA brush polymers assuming 100% mass recovery.Electron paramagnetic resonance (EPR) spectroscopy was performed on a Bruker EMX X-band spectrometer. EPR tubes with O. D. 1 mm were used. The solutions were deoxygenated by bubbling argon then sealed prior to the EPR measurements. Typical parameters used for the EPR

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“…41 The case of non-zero director tilt angle ζ for the simulations was introduced in the literature 10, 11 , where the integration over all the azimuthal orientations was taken to simulate EPR spectra for the arbitrary orientation of the magnetic field with respect to the bilayer normal. For consistency, we carefully followed the simulation procedures established in the literature (comparable model system, simulation parameters, and notations).…”

Section: Epr Spectral Simulationsmentioning

confidence: 99%

Determining the Topology of Integral Membrane Peptides Using EPR Spectroscopy

et al. 2006

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This paper reports on the development of a new structural biology technique for determining the membrane topology of an integral membrane protein inserted into magnetically aligned phospholipid bilayers (bicelles) using EPR spectroscopy. The nitroxide spin probe, 2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid (TOAC) was attached to the pore-lining transmembrane domain (M2δ) of the nicotinic acetylcholine receptor (AChR) and incorporated into a bicelle. The corresponding EPR spectra revealed hyperfine splittings that were highly dependent on the macroscopic orientation of the bicelles with respect to the static magnetic field. The helical tilt of the peptide can be easily calculated using the hyperfine splittings gleaned from the orientational dependent EPR spectra. A helical tilt of 14° was calculated for the M2δ peptide with respect to the bilayer normal of the membrane, which agrees well with previous 15 N solid-state NMR studies. The helical tilt of the peptide was verified by simulating the corresponding EPR spectra using the standardized MOMD approach. This new method is advantageous because: (1) bicelle samples are easy to prepare, (2) the helical tilt can be directly calculated from the orientational-dependent hyperfine splitting in the EPR spectra, and (3) EPR spectroscopy is approximately 1000 fold more sensitive than 15 N solid-state NMR spectroscopy; thus, the helical tilt of an integral membrane peptide can be determined with only 100 μg of peptide. The helical tilt can be determined more accurately by placing TOAC spin labels at several positions with this technique.

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Nonlinear-Least-Squares Analysis of Slow-Motion EPR Spectra in One and Two Dimensions Using a Modified Levenberg–Marquardt Algorithm

Cited by 859 publications

References 21 publications

Structural insights on biologically relevant cationic membranes by ESR spectroscopy

Structural insights on biologically relevant cationic membranes by ESR spectroscopy

EPR Study of Spin Labeled Brush Polymers in Organic Solvents

Determining the Topology of Integral Membrane Peptides Using EPR Spectroscopy

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