Two-dimensional ELDOR in the study of model and biological membranes

Chiang, Yun‐Wei; Costa-Filho, Antonio J.; Freed, Jack H.

doi:10.1007/bf03166591

Cited by 9 publications

(29 citation statements)

References 17 publications

(12 reference statements)

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Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4] Among the various ESR techniques, continuous-wave (cw) ESR has been successfully extended to high magnetic fields. [2][3][4][5][6] The greatly improved orientational resolution that is provided by the ESR lineshapes in high frequencies/fields provides a better insight to the molecular dynamics. [2][3][4][5] By means of multi-frequency ESR experiments, one can unravel the details of dynamical modes of the complex systems since the different frequencies provide different time windows.…”

Section: Introductionmentioning

confidence: 99%

“…[2][3][4][5][6] The greatly improved orientational resolution that is provided by the ESR lineshapes in high frequencies/fields provides a better insight to the molecular dynamics. [2][3][4][5] By means of multi-frequency ESR experiments, one can unravel the details of dynamical modes of the complex systems since the different frequencies provide different time windows. [2][3][4][5]7 In recent years, it has been shown that 2D-ESR methods, in particular 2D-ELDOR (electron-electron double resonance) studies on complex fluids and macromolecules provide even greater spectral resolution to molecular dynamics and ordering.…”

Section: Introductionmentioning

confidence: 99%

“…[2][3][4][5] By means of multi-frequency ESR experiments, one can unravel the details of dynamical modes of the complex systems since the different frequencies provide different time windows. [2][3][4][5]7 In recent years, it has been shown that 2D-ESR methods, in particular 2D-ELDOR (electron-electron double resonance) studies on complex fluids and macromolecules provide even greater spectral resolution to molecular dynamics and ordering. 2,3,8 2D-ELDOR provides this, because it enables one to distinguish the homogeneous broadening a) Authors to whom correspondence should be addressed.…”

Section: Introductionmentioning

confidence: 99%

“…[2][3][4][5]7 In recent years, it has been shown that 2D-ESR methods, in particular 2D-ELDOR (electron-electron double resonance) studies on complex fluids and macromolecules provide even greater spectral resolution to molecular dynamics and ordering. 2,3,8 2D-ELDOR provides this, because it enables one to distinguish the homogeneous broadening a) Authors to whom correspondence should be addressed. Electronic addresses: ywchiang@mx.nthu.edu.tw and jhf3@cornell.edu.…”

Section: Introductionmentioning

confidence: 99%

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A new Lanczos-based algorithm for simulating high-frequency two-dimensional electron spin resonance spectra

Chiang

Freed

2011

The Journal of Chemical Physics

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The Lanczos algorithm (LA) is a useful iterative method for the reduction of a large matrix to tridiagonal form. It is a storage efficient procedure requiring only the preceding two Lanczos vectors to compute the next. The quasi-minimal residual (QMR) method is a powerful method for the solution of linear equation systems, Ax = b. In this report we provide another application of the QMR method: we incorporate QMR into the LA to monitor the convergence of the Lanczos projections in the reduction of large sparse matrices. We demonstrate that the combined approach of the LA and QMR can be utilized efficiently for the orthogonal transformation of large, but sparse, complex, symmetric matrices, such as are encountered in the simulation of slow-motional 1D-and 2D-electron spin resonance (ESR) spectra. Especially in the 2D-ESR simulations, it is essential that we store all of the Lanczos vectors obtained in the course of the LA recursions and maintain their orthogonality. In the LA-QMR application, the QMR weight matrix mitigates the problem that the Lanczos vectors lose orthogonality after many LA projections. This enables substantially more Lanczos projections, as required to achieve convergence for the more challenging ESR simulations. It, therefore, provides better accuracy for the eigenvectors and the eigenvalues of the large sparse matrices originating in 2D-ESR simulations than does the previously employed method, which is a combined approach of the LA and the conjugate-gradient (CG) methods, as evidenced by the quality and convergence of the 2D-ESR simulations. Our results show that very slow-motional 2D-ESR spectra at W-band (95 GHz) can be reliably simulated using the LA-QMR method, whereas the LA-CG consistently fails. The improvements due to the LA-QMR are of critical importance in enabling the simulation of high-frequency 2D-ESR spectra, which are characterized by their very high resolution to molecular orientation.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A new Lanczos-based algorithm for simulating high-frequency two-dimensional electron spin resonance spectra

Chiang

Freed

2011

The Journal of Chemical Physics

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Pulsed Methods in Electron Spin Resonance

Bowman

2010

Encyclopedia of Analytical Chemistry

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This article describes how pulsed electron spin resonance (ESR) signals and spectra are generated. A few basic pulse sequences are introduced, along with a simple vector model and the Bloch equations to explain the signals that are produced and the type of information each signal contains. The major applications of pulsed ESR are described for the measurement of ESR spectra, relaxation times, chemical reaction kinetics, molecular motion, hyperfine interactions, and the distances between radicals. The common pulse sequences used for each of these measurements are described and some of the limitations and drawbacks are discussed. The simple models for pulsed ESR are modified, as needed, to explain unexpected features encountered in some experimental measurements. Double resonance and 2D spectroscopies such as electron nuclear double resonance (ENDOR), double electron–electron resonance (DEER), and hyperfine sublevel correlation (HYSCORE) are discussed.

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The New Fluorescent Membrane Probe Ahba: A Comparative Study with the Largely Used Laurdan

2013

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Lipid bilayers have been largely used as model systems for biological membranes. Hence, their structures, and alterations caused on them by biological active molecules, have been the subject of many studies. Accordingly, fluorescent probes incorporated into lipid bilayers have been extensively used for characterizing lipid bilayer fluidity and/or polarity. However, for the proper analysis of the alterations undergone by a membrane, a comprehensive knowledge of the fluorescent properties of the probe is fundamental. Therefore, the present work compares fluorescent properties of a relative new fluorescent membrane probe, 2-amino-N-hexadecyl-benzamide (Ahba), with the largely used probe 6-dodecanoyl-N,N-dimethyl-2-naphthylamine (Laurdan), using both static and time resolved fluorescence. Both Ahba and Laurdan have the fluorescent moiety close to the bilayer surface; Ahba has a rather small fluorescent moiety, which was shown to be very sensitive to the bilayer surface pH. The main goal was to point out the fluorescent properties of each probe that are most sensitive to structural alterations on a lipid bilayer. The two probes were incorporated into bilayers of the well-studied zwitterionic lipid dimyristoyl phosphatidylcholine (DMPC), which exhibits a gel-fluid transition around 23 °C. The system was monitored between 5 and 50 °C, hence allowing the study of the two different lipid structures, the gel and fluid bilayer phases, and the transition between them. As it is known, the fluorescent emission spectrum of Laurdan is highly sensitive to the bilayer gel-fluid transition, whereas the Ahba fluorescence spectrum was found to be insensitive to changes in bilayer structure and polarity, which are known to happen at the gel-fluid transition. However, both probes monitor the bilayer gel-fluid transition through fluorescence anisotropy measurements. With time-resolved fluorescence, it was possible to show that bilayer structural variations can be monitored by Laurdan excited state lifetimes changes, whereas Ahba lifetimes were found to be insensitive to bilayer structural modifications. Through anisotropy time decay measurements, both probes could monitor structural bilayer changes, but the limiting anisotropy was found to be a better parameter than the rotational correlation time. It is interesting to have in mind that the relatively small fluorophore of Ahba (o-Abz) could possibly be bound to a phospholipid hydrocarbon chain, not disturbing much the bilayer packing and being a sensitive probe for the bilayer core.

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Two-dimensional ELDOR in the study of model and biological membranes

Cited by 9 publications

References 17 publications

A new Lanczos-based algorithm for simulating high-frequency two-dimensional electron spin resonance spectra

A new Lanczos-based algorithm for simulating high-frequency two-dimensional electron spin resonance spectra

Pulsed Methods in Electron Spin Resonance

The New Fluorescent Membrane Probe Ahba: A Comparative Study with the Largely Used Laurdan

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