1,720,984 research outputs found
Mims Electron-Nuclear Double Resonance (ENDOR) with chirp microwave pulses
No full texthttp://dx.doi.org/10.13039/501100001659 German Research Foundationhttp://dx.doi.org/10.13039/501100004189 Max-Planck-Gesellschafthttp://dx.doi.org/10.13039/100010661 Horizon 2020 Framework Programmehttp://dx.doi.org/10.13039/501100000781 European Research Councilhttp://dx.doi.org/10.13039/100010663 H2020 European Research Counci
High-frequency 263 GHz PELDOR.
No full textPulsed electron-electron double resonance (PELDOR/DEER) at high frequencies can provide information on the relative orientation of paramagnetic centres or spin labels, if those are rigidly oriented in a host biomolecule and experiments are performed with sufficient orientation selectivity. We present the first comparative PELDOR study at 263 and 94 GHz on a model RNA system containing rigid nitroxides. We show that at 263 GHz still considerable modulation depth is observed and orientation selectivity is significant, particularly in g (x)-g (y) plane of the nitroxides
High DNP efficiency of TEMPONE radicals in liquid toluene at low concentrations.
Get PDFWe show that at low concentrations (≤5 mM) TEMPONE radicals in liquid toluene exhibit higher DNP efficiency than in water. In spite of reduced coupling factors, the improved DNP performance in toluene results from favourable saturation and leakage factors, as determined by pulse electron–electron double resonance (ELDOR) and NMR relaxation, respectively. The extracted coupling factors at 0.35 Tesla support theoretical predictions of the Overhauser mechanism
Drift Models on Complex Projective Space for Electron-Nuclear Double Resonance
No full textENDOR spectroscopy is an important tool to determine the complicated
three-dimensional structure of biomolecules and in particular enables
measurements of intramolecular distances. Usually, spectra are determined by
averaging the data matrix, which does not take into account the significant
thermal drifts that occur in the measurement process. In contrast, we present
an asymptotic analysis for the homoscedastic drift model, a pioneering
parametric model that achieves striking model fits in practice and allows both
hypothesis testing and confidence intervals for spectra. The ENDOR spectrum and
an orthogonal component are modeled as an element of complex projective space,
and formulated in the framework of generalized Fr\'echet means. To this end,
two general formulations of strong consistency for set-valued Fr\'echet means
are extended and subsequently applied to the homoscedastic drift model to prove
strong consistency. Building on this, central limit theorems for the ENDOR
spectrum are shown. Furthermore, we extend applicability by taking into account
a phase noise contribution leading to the heteroscedastic drift model. Both
drift models offer improved signal-to-noise ratio over pre-existing models
W-band orientation selective DEER measurements on a Gd3+/nitroxide mixed-labeled protein dimer with a dual mode cavity
No full textDouble electron-electron resonance (DEER) at W-band (95 GHz) was applied to measure the distance between a pair of nitroxide and Gd3+ chelate spin labels, about 6 nm apart, in a homodimer of the protein ERp29. While high-field DEER measurements on systems with such mixed labels can be highly attractive in terms of sensitivity and the potential to access long distances, a major difficulty arises from the large frequency spacing (about 700 MHz) between the narrow, intense signal of the Gd3+ central transition and the nitroxide signal. This is particularly problematic when using standard single-mode cavities. Here we show that a novel dual-mode cavity that matches this large frequency separation dramatically increases the sensitivity of DEER measurements, allowing evolution times as long as 12 mu s in a protein. This opens the possibility of accessing distances of 8 nm and longer. In addition, orientation selection can be resolved and analyzed, thus providing additional structural information. In the case of W-band DEER on a Gd3+-nitroxide pair, only two angles and their distributions have to be determined, which is a much simpler problem to solve than the five angles and their distributions associated with two nitroxide spin labels. (C) 2012 Elsevier Inc. All rights reserved
Drift Models on Complex Projective Space for Electron-Nuclear Double Resonance
No full textENDOR spectroscopy is an important tool to determine the complicated
three-dimensional structure of biomolecules and in particular enables
measurements of intramolecular distances. Usually, spectra are determined by
averaging the data matrix, which does not take into account the significant
thermal drifts that occur in the measurement process. In contrast, we present
an asymptotic analysis for the homoscedastic drift model, a pioneering
parametric model that achieves striking model fits in practice and allows both
hypothesis testing and confidence intervals for spectra. The ENDOR spectrum and
an orthogonal component are modeled as an element of complex projective space,
and formulated in the framework of generalized Fr\'echet means. To this end,
two general formulations of strong consistency for set-valued Fr\'echet means
are extended and subsequently applied to the homoscedastic drift model to prove
strong consistency. Building on this, central limit theorems for the ENDOR
spectrum are shown. Furthermore, we extend applicability by taking into account
a phase noise contribution leading to the heteroscedastic drift model. Both
drift models offer improved signal-to-noise ratio over pre-existing models
Spin density localization and accessibility of organic radicals affect liquid-state DNP efficiency
No full textA dual-mode microwave resonator for double electron–electron spin resonance spectroscopy at W-band microwave frequencies.
No full textEnhancing NMR Signals in Liquids by Fluorine‐19 Overhauser Dynamic Nuclear Polarization (DNP) and Hyperpolarization Transfer to Carbon‐13
No full textEuropean Research Council https://doi.org/10.13039/50110000078
High-resolution measurement of long-range distances in RNA: pulse EPR spectroscopy with TEMPO-labeled nucleotides
Get PDFStructural information at atomic resolution of biomolecular assemblies, such as RNA and RNA protein complexes, is fundamental to comprehend biological function. Modern spectroscopic methods offer exceptional opportunities in this direction. Here we present the capability of pulse EPR to report high-resolution long-range distances in RNAs by means of a recently developed spin labeled nucleotide, which carries the TEMPO group directly attached to the nucleobase and preserves Watson–Crick base-pairing. In a representative RNA duplex with spin-label separations up to 28 base pairs (≈8 nm) we demonstrate that the label allows for a model-free conversion of inter-spin distances into base-pair separation (Δbp) if broad-band pulse excitation at Q band frequencies (34 GHz) is applied. The observed distance distribution increases from ±0.2 nm for Δbp = 10 to only ±0.5 nm for Δbp = 28, consistent with only small deviations from the “ideal” A-form RNA structure. Molecular dynamics (MD) simulations conducted at 20 °C show restricted conformational freedom of the label. MD-generated structural deviations from an “ideal” A-RNA geometry help disentangle the contributions of local flexibility of the label and its neighboring nucleobases and global deformations of the RNA double helix to the experimental distance distributions. The study demonstrates that our simple but strategic spin labeling procedure can access detailed structural information on RNAs at atomic resolution over distances that match the size of macromolecular RNA complexes
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