Probing Columnar Discotic Liquid Crystals by EPR Spectroscopy with a Rigid‐Core Nitroxide Spin Probe

Gopee, Hemant; Cammidge, Andrew N.; Oganesyan, Vasily S.

doi:10.1002/anie.201303194

Cited by 8 publications

(7 citation statements)

References 37 publications

(22 reference statements)

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“…EPR with nitroxide spin probes has proven to be a particularly effective technique in the study of the dynamic behaviour of various soft matter systems including lyotropic liquid crystals . EPR has the ability of directly resolving molecular reorientational dynamics on the sub‐nanosecond time scale .…”

Section: Introductionmentioning

confidence: 99%

“…Such techniques can greatly simplify the interpretation and analysis of experimental spectra, and hence provide unambiguous conclusions about molecular order and motions. These MD‐EPR methods have been successfully applied to spin labelled proteins and thermotropic liquid crystals …”

Section: Introductionmentioning

confidence: 99%

“…Both systems are industrially ubiquitous, have well definede xperimentalp hase diagrams exhibitingm ultiple lyotropic phases including micellar,r od/hexagonal and lamellar phases,a sw ell as intermediate mixed structures. [4,15,16] EPR with nitroxide spin probesh as proven to be aparticularly effective technique in the study of the dynamic behaviour of variouss oft matter systems [17][18][19][20] includingl yotropic liquid crystals. [3,4,6,21] EPR has the ability of directly resolvingm olecular re-orientational dynamics on the sub-nanosecond time scale.…”

Section: Introductionmentioning

confidence: 99%

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Prediction of EPR Spectra of Lyotropic Liquid Crystals using a Combination of Molecular Dynamics Simulations and the Model‐Free Approach

Prior

Oganesyan

2017

Chemistry A European J

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We report the first application of fully atomistic molecular dynamics (MD) simulations to the prediction of the motional electron paramagnetic resonance (EPR) spectra of lyotropic liquid crystals in different aggregation states doped with a paramagnetic spin probe. The purpose of this study is twofold. First, given that EPR spectra are highly sensitive to the motions and order of the spin probes doped within lyotropic aggregates, simulation of EPR line shapes from the results of MD modelling provides an ultimate test bed for the force fields currently employed to model such systems. Second, the EPR line shapes are simulated using the motional parameters extracted from MD trajectories using the Model-Free (MF) approach. Thus a combined MD-EPR methodology allowed us to test directly the validity of the application of the MF approach to systems with multi-component molecular motions. All-atom MD simulations using the General AMBER Force Field (GAFF) have been performed on sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium chloride (DTAC) liquid crystals. The resulting MD trajectories were used to predict and interpret the EPR spectra of pre-micellar, micellar, rod and lamellar aggregates. The predicted EPR spectra demonstrate good agreement with most of experimental line shapes thus confirming the validity of both the force fields employed and the MF approach for the studied systems. At the same time simulation results confirm that GAFF tends to overestimate the packing and the order of the carbonyl chains of the surfactant molecules.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Prediction of EPR Spectra of Lyotropic Liquid Crystals using a Combination of Molecular Dynamics Simulations and the Model‐Free Approach

Prior

Oganesyan

2017

Chemistry A European J

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“…The paper by Oganesyan and co-workers reported the first application of EPR spectroscopy to columnar discotic liquid crystal hexakis(n-hexyloxy)-triphenylene (HAT6) using a novel rigid-core nitroxide spin probe designed and synthesized for this purpose. 77 Simulation of the EPR line shapes using a BD simulation model with the Langevin equation corresponding to different phases of HAT6 provided a numerical estimate of molecular rotational dynamics, columnar order as well as the director distribution at different temperatures along both isotropic-columnar and columnarcrystalline phase transitions. 77 LvN equation combined with BD simulations have also been reported for spin systems with SW1/2 with substantially larger dimensions of the Liouville matrixes.…”

Section: Applications Of Bd Trajectories Approach and Its Further Devmentioning

confidence: 99%

“…77 Simulation of the EPR line shapes using a BD simulation model with the Langevin equation corresponding to different phases of HAT6 provided a numerical estimate of molecular rotational dynamics, columnar order as well as the director distribution at different temperatures along both isotropic-columnar and columnarcrystalline phase transitions. 77 LvN equation combined with BD simulations have also been reported for spin systems with SW1/2 with substantially larger dimensions of the Liouville matrixes. Examples include systems with electron spins up to S = 7/2 78 and copper(II) porphyrin with hyperfine coupling to four 14 N atoms.…”

Section: Applications Of Bd Trajectories Approach and Its Further Devmentioning

confidence: 99%

Chapter 2. Computational approaches for simulating motional EPR spectra

Oganesyan¹

2014

Electron Paramagnetic Resonance

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Direct Prediction of EPR Spectra from Lipid Bilayers: Understanding Structure and Dynamics in Biological Membranes

et al. 2018

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Of the many biophysical techniques now being brought to bear on studies of membranes, electron paramagnetic resonance (EPR) of nitroxide spin probes was the first to provide information about both mobility and ordering in lipid membranes. Here, we report the first prediction of variable temperature EPR spectra of model lipid bilayers in the presence and absence of cholesterol from the results of large scale fully atomistic molecular dynamics (MD) simulations. Three types of structurally different spin probes were employed in order to study different parts of the bilayer. Our results demonstrate very good agreement with experiment and thus confirm the accuracy of the latest lipid force fields. The atomic resolution of the simulations allows the interpretation of the molecular motions and interactions in terms of their impact on the sensitive EPR line shapes. Direct versus indirect effects of cholesterol on the dynamics of spin probes are analysed. Given the complexity of structural organisation in lipid bilayers, the advantage of using a combined MD‐EPR simulation approach is two‐fold. Firstly, prediction of EPR line shapes directly from MD trajectories of actual phospholipid structures allows unambiguous interpretation of EPR spectra of biological membranes in terms of complex motions. Secondly, such an approach provides an ultimate test bed for the up‐to‐date MD simulation models employed in the studies of biological membranes, an area that currently attracts great attention.

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Probing Columnar Discotic Liquid Crystals by EPR Spectroscopy with a Rigid‐Core Nitroxide Spin Probe

Cited by 8 publications

References 37 publications

Prediction of EPR Spectra of Lyotropic Liquid Crystals using a Combination of Molecular Dynamics Simulations and the Model‐Free Approach

Prediction of EPR Spectra of Lyotropic Liquid Crystals using a Combination of Molecular Dynamics Simulations and the Model‐Free Approach

Chapter 2. Computational approaches for simulating motional EPR spectra

Direct Prediction of EPR Spectra from Lipid Bilayers: Understanding Structure and Dynamics in Biological Membranes

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