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Robert G Griffin - One of the best experts on this subject based on the ideXlab platform.
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targeted 13c 13c distance measurements in a microcrystalline protein via j decoupled Rotational Resonance width measurements
ChemPhysChem, 2009Co-Authors: Patrick C A Van Der Wel, Ramesh Ramachandran, Matthew T Eddy, Robert G GriffinAbstract:Rotational Resonance width (R(2)W) magic-angle spinning (MAS) NMR experiments are performed to measure (13)C-(13)C distances in the hydrophobic core of the microcrystalline model protein G(Beta1). Such inter-residue distances are of particular value in NMR structure determinations. The experiments are done at a Larmor frequency of 750 MHz (1)H where the contribution of (13)C chemical shift anisotropy (CSA) to the R(2) transfer mechanism is significant. To minimize line broadening in the 2D spectra, we employ a combination of even/odd isotopic labeling with [1,3-(13)C] glycerol, and J-decoupling in the indirect dimension. This results in high-precision distance measurements between aromatic side chains of three tyrosine residues and distant methyl groups in the hydrophobic core of the protein. Even in the absence of information on the relative orientation of the shift tensors, we obtain relatively high precision data, which can be further improved by additional constraints on the tensor orientations.
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multipole multimode floquet theory of Rotational Resonance width experiments 13c 13c distance measurements in uniformly labeled solids
Journal of Chemical Physics, 2006Co-Authors: Ramesh Ramachandran, Jozef R Lewandowski, Patrick C A Van Der Wel, Robert G GriffinAbstract:A formal description of zero-quantum (ZQ) NMR processes using multipole-multimode Floquet theory is proposed for studying polarization transfer in magic angle spinning experiments. Specifically, we investigate the factors affecting the accuracy and precision of 13C-13C distance measurements that are based on ZQ-magnetization exchange processes in Rotational Resonance width experiments. With suitable examples drawn from measurements in N-acetyl-[U-13C,15N]-L-valine-L-leucine, we substantiate our approach and propose methods for improving the accuracy and reliability of such 13C-13C distance measurements in uniformly 13C, 15N-labeled solids. In addition, the theoretical model presented in this article provides a more general framework for describing relaxation phenomena involving multiple decay rate constants in zero-quantum processes.
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13c 13c Rotational Resonance width distance measurements in uniformly 13c labeled peptides
Journal of the American Chemical Society, 2003Co-Authors: Ramesh Ramachandran, Vladimir Ladizhansky, Vikram S Bajaj, Robert G GriffinAbstract:The Rotational Resonance width (R2W) experiment is a constant-time version of the Rotational Resonance (R2) experiment, in which the magnetization exchange is measured as a function of sample spinning frequency rather than the mixing time. The significant advantage of this experiment over conventional R2 is that both the dipolar coupling and the relaxation parameters can be independently and unambiguously extracted from the magnetization exchange profile. In this paper, we combine R2W with two-dimensional 13C-13C chemical shift correlation spectroscopy and demonstrate the utility of this technique for the site-specific measurement of multiple 13C-13C distances in uniformly labeled solids. The dipolar truncation effects, usually associated with distance measurements in uniformly labeled solids, are considerably attenuated in R2W experiments. Thus, R2W experiments are applicable to uniformly labeled biological systems. To validate this statement, multiple 13C-13C distances (in the range of 3-6 A) were determined in N-acetyl-[U-13C,15N]l-Val-l-Leu with an average precision of +/-0.5 A. Furthermore, the distance constraints extracted using a two-spin model agree well with the X-ray crystallographic data.
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Rotational Resonance nmr separation of dipolar coupling and zero quantum relaxation
Journal of Magnetic Resonance, 2003Co-Authors: Phillip R Costa, Boqin Sun, Robert G GriffinAbstract:Abstract The solid state NMR technique of Rotational Resonance ( R 2 ) has been used extensively to measure distances approaching 5–6 A between 13 C nuclei in a variety of compounds including amyloidogenic peptides and membrane proteins. The accuracy of the distance information extracted from the time-dependent spin dynamics at R 2 is often limited by the accuracy with which the relevant zero-quantum lineshape parameters are estimated. Here we demonstrate that measurement of spinning frequency dependent magnetization exchange dynamics provides data from which both distance and zero-quantum relaxation parameters can be extracted independently. In addition to providing more accurate distance information, this technique allows examination of the zero-quantum lineshape, which can indicate the presence of correlated relaxation or chemical shift distributions between dipolar-coupled sites. With this approach we have separated the contribution of dipolar couplings and zero quantum relaxation to R 2 exchange curves. Thus, we have significantly improved the accuracy of the measurement of the intramolecular, internuclear distances between a pair of 13 C ’s in two model compounds ( N -acetyl- d , l -valine and glycylglycine·HCl) that lie in the distance range 4.6–4.7 A.
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Rotational Resonance tickling accurate internuclear distance measurement in solids
Journal of the American Chemical Society, 1997Co-Authors: Philip R Costa, Boqin Sun, Robert G GriffinAbstract:Accurate distance measurements between pairs of nuclear spins can provide detailed information about molecular structure in the solid state. The Rotational Resonance (R 2 ) technique, in particular, has been used to measure internuclear distances in a variety of compounds, often between pairs of 13 C nuclei where the outer range is 5- 6A . Recent studies have revealed that the spin dynamics at Rotational Resonance are influenced by zero-quantum line shape parameters including T2 zq and the dispersion in isotropic chemical shift differences. Errors in the estimation of these parameters are often the limiting factor in determining the accuracy of a distance measurement. Here we present a modification of R 2 , termed "Rotational Resonance tickling" (R 2 T), which uses a ramped rf field to induce fast passage through the dipolar Resonance condition, thereby greatly reducing the dependence of the spin dynamics on zero-quantum parameters. Extraction of distance information from the resulting exchange curves is approximately a single-parameter fit, with accuracies in model systems that appear to be on the order of (0.1 A or better. An additional feature of the technique is that it does not demand the very high-power 1 H decoupling fields typically required in other recoupling experiments to limit signal loss during mixing. We demonstrate the technique in a pair of 13 C2-labeled model compounds, tyrosine ethyl ester and glycylglycine hydrochloride, with effective internuclear distances (including intermolecular effects) of 5.05 and 4.3 A, respectively.
Takehiko Terao - One of the best experts on this subject based on the ideXlab platform.
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13c 1h dipolar driven 13c 13c recoupling without 13c rf irradiation in nuclear magnetic Resonance of rotating solids
Journal of Chemical Physics, 2003Co-Authors: K Takegoshi, Shinji Nakamura, Takehiko TeraoAbstract:Two recently proposed 13C–13C recoupling methods under magic angle spinning (MAS), resonant interference recoupling (RIR), and 13C–1H dipolar-assisted Rotational Resonance (DARR), are examined on a common theoretical foundation using the average Hamiltonian theory. In both methods, a rf field is applied on not 13C but 1H to recouple the 13C–1H dipolar interactions, and spectral overlap necessary to conserve energy for 13C–13C polarization transfer is achieved by the 13C–1H dipolar line broadening. While DARR employs time-independent 13C–1H interactions recoupled by suitable rf irradiation to 1H spins, RIR uses time-dependent 13C–1H interactions modulated appropriately by 1H rf irradiation. There are two distinct cases where 13C–1H line broadening realizes 13C–13C spectral overlap. For a pair of a carbonyl or aromatic carbon and an aliphatic carbon, spectral overlap can be achieved between one of the spinning sidebands of the former 13C Resonance and the 13C–1H dipolar powder pattern of the latter. On the ...
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dipolar assisted Rotational Resonance in magic angle spinning nmr
Chemical Physics Letters, 2001Co-Authors: K Takegoshi, Shinji Nakamura, Takehiko TeraoAbstract:Abstract A new 13 C – 13 C recoupling mechanism which occurs under magic-angle spinning (MAS) is presented. The mechanism can basically be attributed to Rotational Resonance (R 2 ), but the conventional R 2 condition is modified by a recoupled 13 C – 1 H dipolar interaction. The 13 C – 1 H recoupling is attained by 1 H rf irradiation fulfilling a rotary-Resonance condition. The present method does not have the drawbacks associated with rf irradiation on 13 C and is applicable for band-selective recoupling between carbonyl/aromatic carbons and aliphatic carbons. The 13 C – 13 C recoupling mechanism under 13 C – 1 H recoupling is theoretically explained and is experimentally demonstrated using N -acetyl[1,2- 13 C] dl -valine and uniformly 13 C, 15 N-labeled glycylisoleucine.
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13c 1h dipolar assisted Rotational Resonance in magic angle spinning nmr
Chemical Physics Letters, 2001Co-Authors: K Takegoshi, Shinji Nakamura, Takehiko TeraoAbstract:Abstract A new 13 C – 13 C recoupling mechanism which occurs under magic-angle spinning (MAS) is presented. The mechanism can basically be attributed to Rotational Resonance (R 2 ), but the conventional R 2 condition is modified by a recoupled 13 C – 1 H dipolar interaction. The 13 C – 1 H recoupling is attained by 1 H rf irradiation fulfilling a rotary-Resonance condition. The present method does not have the drawbacks associated with rf irradiation on 13 C and is applicable for band-selective recoupling between carbonyl/aromatic carbons and aliphatic carbons. The 13 C – 13 C recoupling mechanism under 13 C – 1 H recoupling is theoretically explained and is experimentally demonstrated using N -acetyl[1,2- 13 C] dl -valine and uniformly 13 C, 15 N-labeled glycylisoleucine.
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Three-dimensional structure determination of a uniformly labeled molecule by frequency-selective dipolar recoupling under magic-angle spinning
Journal of Biomolecular NMR, 2000Co-Authors: Kaoru Nomura, Kiyonori Takegoshi, Takehiko Terao, Kenichi Uchida, Masatsune KainoshoAbstract:The complete three-dimensional (3D) structure of a glycylisoleucine (Gly-Ile) molecule was determined by individually measuring six dihedral angles with a frequency-selective homonuclear dipolar recoupling method, R2TR (Rotational Resonance in the tilted rotating frame), using a powder sample of diluted uniformly 13,15-labeled Gly-Ile. Each dihedral angle was obtained by recoupling a dipolar interaction between three or four bonds distant spins concerned or observing a dipolar correlation 2D powder pattern. The 3D structure of a Gly-Ile molecule was also determined by X-ray crystallography, and a good agreement with the NMR result was obtained. The results demonstrate that the R2TR method in a uniformly labeled powder sample can provide the 3D structure without the need to prepare a lot of selectively labeled samples.
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Rotational Resonance in the tilted rotating frame
Chemical Physics Letters, 1995Co-Authors: Kiyonori Takegoshi, Kaoru Nomura, Takehiko TeraoAbstract:Abstract We propose a new solid-state NMR technique under magic-angle spinning to recouple the dipolar interaction for a particular pair of homonuclear spins. In this method, a weak radio-frequency field is applied during the mixing time of the exchange NMR, and its frequency and intensity are chosen to realize Rotational Resonance for a particular pair of spins in the tilted rotating frame. The selective recoupling is demonstrated for the dipolar interaction between the CH and CH 3 carbons in triply 13 C-enriched l -alanine, whose chemical shift difference is too small to apply the conventional Rotational Resonance method.
Justin L. Neill - One of the best experts on this subject based on the ideXlab platform.
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enhancing sensitivity for high selectivity gas chromatography molecular Rotational Resonance spectroscopy
Analytical Chemistry, 2021Co-Authors: Farooq M Wahab, Justin L. Neill, Aleksandr V Mikhonin, Saba Aslani, Daniel W ArmstrongAbstract:A next-generation gas chromatograph-molecular Rotational Resonance (MRR) spectrometer (GC-MRR) with instrumental improvements and higher sensitivity is described. MRR serves as a structural information-rich detector for GC with extremely narrow linewidths and capabilities surpassing 1H nuclear magnetic Resonance/Fourier transform infrared spectroscopy/mass spectrometry (MS) while offering unparalleled specificity in regard to a molecule's three-dimensional structure. With a Fabry-Perot cavity and a supersonic jet incorporated into a GC-MRR, dramatic improvements in sensitivity for molecules up to 244 Da were achieved in the microwave region compared to the only prior work, which demonstrated the GC-MRR idea for the first time with millimeter waves. The supersonic jet cools the analytes to ∼2 K, resulting in a limited number of molecular Rotational and vibrational levels and enabling us to obtain stronger GC-MRR signals. This has allowed the limits of detection of the GC-MRR to be comparable to a GC thermal conductivity detector with an optimized choice of gases. The performance of this GC-MRR system is reported for a range of molecules with permanent dipole moments, including alcohols, nitrogen heterocyclics, halogenated compounds, dioxins, and nitro compounds in the molecular mass range of 46-244 Da. The lowest amount of any substance yet detected by MRR in terms of mass is reported in this work. A theoretically unexpected finding is reported for the first time about the effect of the GC carrier gas (He, Ne, and N2) on the sensitivity of the analysis in the presence of the gas driving the supersonic jet (He, Ne, and N2) in the GC-MRR. Finally, the idea of total molecule monitoring in the GC-MRR analogous to selected ion monitoring in GC-MS is illustrated. Structural isomers and isotopologues of bromobutanes and bromonitrobenzenes are used to demonstrate this concept.
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chiral analysis of pantolactone with molecular Rotational Resonance spectroscopy
Chirality, 2021Co-Authors: Reilly E. Sonstrom, Justin L. Neill, Aleksandr V Mikhonin, Reinhard Doetzer, Brooks H. PateAbstract:A molecular Rotational Resonance spectroscopy method for measuring the enantiomeric excess of pantolactone, an intermediate in the synthesis of panthenol and pantothenic acid, is presented. The enantiomers are distinguished via complexation with a small chiral tag molecule, which produces diastereomeric complexes in the pulsed jet expansion used to inject the sample into the spectrometer. These complexes have distinct moments of inertia, so their spectra are resolved by MRR spectroscopy. Quantitative enantiomeric excess (EE) measurements are made by taking the ratio of normalized complex signal levels when a chiral tag sample of high, known EE is used, while the absolute configuration of the sample can be determined from electronic structure calculations of the complex geometries. These measurements can be performed without the need for reference samples with known enantiopurity. Two instruments were used in the analysis. A broadband, chirped-pulse spectrometer is used to perform structural characterization of the complexes. The broadband spectrometer is also used to determine the EE; however, this approach requires relatively long measurement times. A targeted MRR spectrometer is also used to demonstrate EE analysis with approximately 15-min sample-to-sample cycle time. The quantitative accuracy of the method is demonstrated by comparison with chiral gas chromatography and through the measurement of a series of reference samples prepared from mixtures of (R)-pantolactone and (S)-pantolactone samples of known EE.
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copper catalyzed transfer hydrodeuteration of aryl alkenes with quantitative isotopomer purity analysis by molecular Rotational Resonance spectroscopy
Journal of the American Chemical Society, 2021Co-Authors: Zoua Pa Vang, Justin L. Neill, Reilly E. Sonstrom, Brooks H. Pate, Albert Reyes, Martin Holdren, Samantha E Sloane, Isabella Y Alansari, Joseph R ClarkAbstract:A copper-catalyzed alkene transfer hydrodeuteration reaction that selectively incorporates one hydrogen and one deuterium atom across an aryl alkene is described. The transfer hydrodeuteration protocol is selective across a variety of internal and terminal alkenes and is also demonstrated on an alkene-containing complex natural product analog. Beyond using 1H, 2H, and 13C NMR analysis to measure reaction selectivity, six transfer hydrodeuteration products were analyzed by molecular Rotational Resonance (MRR) spectroscopy. The application of MRR spectroscopy to the analysis of isotopic impurities in deuteration chemistry is further explored through a measurement methodology that is compatible with high-throughput sample analysis. In the first step, the MRR spectroscopy signatures of all isotopic variants accessible in the reaction chemistry are analyzed using a broadband chirped-pulse Fourier transform microwave spectrometer. With the signatures in hand, measurement scripts are created to quantitatively analyze the sample composition using a commercial cavity enhanced MRR spectrometer. The sample consumption is below 10 mg with analysis times on the order of 10 min using this instrument-both representing order-of-magnitude reduction compared to broadband MRR spectroscopy. To date, these measurements represent the most precise spectroscopic determination of selectivity in a transfer hydrodeuteration reaction and confirm that product regioselectivity ratios of >140:1 are achievable under this mild protocol.
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direct regioisomer analysis of crude reaction mixtures via molecular Rotational Resonance mrr spectroscopy
Chemical Science, 2020Co-Authors: Leo A Joyce, Justin L. Neill, Reilly E. Sonstrom, Danielle M Schultz, Edward C Sherer, Brooks H. PateAbstract:Direct analyses of crude reaction mixtures have been carried out using molecular Rotational Resonance (MRR) spectroscopy. Two examples are presented, a demonstration application in photocatalytic CH-arylation as well as generation of an intermediate in a natural product synthesis. In both cases, the reaction can proceed at more than one site, leading to a mixture of regioisomers that can be challenging to distinguish. MRR structural parameters were calculated for the low lying conformers for the desired compounds, and then compared to the experimental spectra of the crude mixtures to confirm the presence of these species. Next, quantitation was performed by comparing experimentally measured line intensities with simulations based on computed values for the magnitude and direction of the molecular dipole moment of each species. This identification and quantification was performed without sample purification and without isolated standards of the compounds of interest. The values obtained for MRR quantitation were in good agreement with the chromatographic values. Finally, previously unknown impurities were discovered within the photocatalytic CH-arylation work. This paper demonstrates the utility of MRR as a reaction characterization tool to simplify analytical workflows.
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a gas chromatography molecular Rotational Resonance spectroscopy based system of singular specificity
Angewandte Chemie, 2020Co-Authors: Daniel W Armstrong, Matt T. Muckle, Mohsen Talebi, Nimisha Thakur, Farooq M Wahab, Aleksandr V Mikhonin, Justin L. NeillAbstract:We designed and demonstrated the unique abilities of the first gas chromatography-molecular Rotational Resonance spectrometer (GC-MRR). While broadly and routinely applicable, its capabilities can exceed those of high-resolution MS and NMR spectroscopy in terms of selectivity, resolution, and compound identification. A series of 24 isotopologues and isotopomers of five organic compounds are separated, identified, and quantified in a single run. Natural isotopic abundances of mixtures of compounds containing chlorine, bromine, and sulfur heteroatoms are easily determined. MRR detection provides the added high specificity for these selective gas-phase separations. GC-MRR is shown to be ideal for compound-specific isotope analysis (CSIA). Different bacterial cultures and groundwater were shown to have contrasting isotopic selectivities for common organic compounds. The ease of such GC-MRR measurements may initiate a new era in biosynthetic/degradation and geochemical isotopic compound studies.
K Takegoshi - One of the best experts on this subject based on the ideXlab platform.
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solid state nmr analysis of interaction sites of curcumin and 42 residue amyloid β protein fibrils
Bioorganic & Medicinal Chemistry, 2011Co-Authors: Yuichi Masuda, Masashi Fukuchi, Tatsuya Yatagawa, Masato Tada, Kazuyuki Takeda, Kazuhiro Irie, Kenichi Akagi, Youko Monobe, Takayoshi Imazawa, K TakegoshiAbstract:Abstract Aggregation of 42-residue amyloid β-protein (Aβ42) plays a pivotal role in the etiology of Alzheimer’s disease (AD). Curcumin, the yellow pigment in the rhizome of turmeric, attracts considerable attention as a food component potentially preventing the pathogenesis of AD. This is because curcumin not only inhibits the aggregation of Aβ42 but also binds to its aggregates (fibrils), resulting in disaggregation. However, the mechanism of interaction between curcumin and the Aβ42 fibrils remains unclear. In this study, we analyzed the binding mode of curcumin to the Aβ42 fibrils by solid-state NMR using dipolar-assisted Rotational Resonance (DARR). To improve the quality of 2D spectra, 2D DARR data were processed with the covariance NMR method, which enabled us to detect weak cross peaks between carbons of curcumin and those of the Aβ42 fibrils. The observed 13C–13C cross peaks indicated that curcumin interacts with the 12th and 17–21st residues included in the β-sheet structure in the Aβ42 fibrils. Interestingly, aromatic carbons adjacent to the methoxy and/or hydroxy groups of curcumin showed clear cross peaks with the Aβ42 fibrils. This suggested that these functional groups of curcumin play an important role in its interaction with the Aβ42 fibrils.
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13c 1h dipolar driven 13c 13c recoupling without 13c rf irradiation in nuclear magnetic Resonance of rotating solids
Journal of Chemical Physics, 2003Co-Authors: K Takegoshi, Shinji Nakamura, Takehiko TeraoAbstract:Two recently proposed 13C–13C recoupling methods under magic angle spinning (MAS), resonant interference recoupling (RIR), and 13C–1H dipolar-assisted Rotational Resonance (DARR), are examined on a common theoretical foundation using the average Hamiltonian theory. In both methods, a rf field is applied on not 13C but 1H to recouple the 13C–1H dipolar interactions, and spectral overlap necessary to conserve energy for 13C–13C polarization transfer is achieved by the 13C–1H dipolar line broadening. While DARR employs time-independent 13C–1H interactions recoupled by suitable rf irradiation to 1H spins, RIR uses time-dependent 13C–1H interactions modulated appropriately by 1H rf irradiation. There are two distinct cases where 13C–1H line broadening realizes 13C–13C spectral overlap. For a pair of a carbonyl or aromatic carbon and an aliphatic carbon, spectral overlap can be achieved between one of the spinning sidebands of the former 13C Resonance and the 13C–1H dipolar powder pattern of the latter. On the ...
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dipolar assisted Rotational Resonance in magic angle spinning nmr
Chemical Physics Letters, 2001Co-Authors: K Takegoshi, Shinji Nakamura, Takehiko TeraoAbstract:Abstract A new 13 C – 13 C recoupling mechanism which occurs under magic-angle spinning (MAS) is presented. The mechanism can basically be attributed to Rotational Resonance (R 2 ), but the conventional R 2 condition is modified by a recoupled 13 C – 1 H dipolar interaction. The 13 C – 1 H recoupling is attained by 1 H rf irradiation fulfilling a rotary-Resonance condition. The present method does not have the drawbacks associated with rf irradiation on 13 C and is applicable for band-selective recoupling between carbonyl/aromatic carbons and aliphatic carbons. The 13 C – 13 C recoupling mechanism under 13 C – 1 H recoupling is theoretically explained and is experimentally demonstrated using N -acetyl[1,2- 13 C] dl -valine and uniformly 13 C, 15 N-labeled glycylisoleucine.
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13c 1h dipolar assisted Rotational Resonance in magic angle spinning nmr
Chemical Physics Letters, 2001Co-Authors: K Takegoshi, Shinji Nakamura, Takehiko TeraoAbstract:Abstract A new 13 C – 13 C recoupling mechanism which occurs under magic-angle spinning (MAS) is presented. The mechanism can basically be attributed to Rotational Resonance (R 2 ), but the conventional R 2 condition is modified by a recoupled 13 C – 1 H dipolar interaction. The 13 C – 1 H recoupling is attained by 1 H rf irradiation fulfilling a rotary-Resonance condition. The present method does not have the drawbacks associated with rf irradiation on 13 C and is applicable for band-selective recoupling between carbonyl/aromatic carbons and aliphatic carbons. The 13 C – 13 C recoupling mechanism under 13 C – 1 H recoupling is theoretically explained and is experimentally demonstrated using N -acetyl[1,2- 13 C] dl -valine and uniformly 13 C, 15 N-labeled glycylisoleucine.
Patrick C A Van Der Wel - One of the best experts on this subject based on the ideXlab platform.
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spinning rate encoded chemical shift correlations from Rotational Resonance solid state nmr experiments
Journal of Magnetic Resonance, 2013Co-Authors: Patrick C A Van Der WelAbstract:Structural measurements in magic-angle-spinning (MAS) solid-state NMR rely heavily on (13)C-(13)C distance measurements. Broadbanded recoupling methods are used to generate many cross-peaks, but have complex polarization transfer mechanisms that limit the precision of distance constraints and can suffer from weak intensities for distant peaks due to relaxation, the broad distribution of polarization, as well as dipolar truncation. Frequency-selective methods that feature narrow-banded recoupling can reduce these effects. Indeed, Rotational Resonance (R(2)) experiments have found application in many different biological systems, where they have afforded improved precision and accuracy. Unfortunately, a highly selective transfer mechanism also leads to few cross-peaks in the resulting spectra, which complicates the extraction of multiple constraints. R(2)-width (R(2)W) measurements that scan a range of MAS rates to probe the R(2) matching conditions of one or more sites can improve precision, and also permit multiple simultaneous distance measurements. However, multidimensional R(2)W can be very time-consuming. Here, we present an approach that facilitates the acquisition of 2D-like spectra based on a series of 1D R(2)W experiments, by taking advantage of the chemical shift information encoded in the MAS rates where matching occurs. This yields a more time-efficient experiment with many of the benefits of more conventional multidimensional R(2)W measurements. The obtained spectra reveal long-distance (13)C-(13)C cross-peaks resulting from R(2)-mediated polarization transfer. This experiment also enables the efficient setup and targeted implementation of traditional R(2) or R(2)W experiments. Analogous applications may extend to other variable-MAS and frequency-selective solid-state NMR experiments.
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targeted 13c 13c distance measurements in a microcrystalline protein via j decoupled Rotational Resonance width measurements
ChemPhysChem, 2009Co-Authors: Patrick C A Van Der Wel, Ramesh Ramachandran, Matthew T Eddy, Robert G GriffinAbstract:Rotational Resonance width (R(2)W) magic-angle spinning (MAS) NMR experiments are performed to measure (13)C-(13)C distances in the hydrophobic core of the microcrystalline model protein G(Beta1). Such inter-residue distances are of particular value in NMR structure determinations. The experiments are done at a Larmor frequency of 750 MHz (1)H where the contribution of (13)C chemical shift anisotropy (CSA) to the R(2) transfer mechanism is significant. To minimize line broadening in the 2D spectra, we employ a combination of even/odd isotopic labeling with [1,3-(13)C] glycerol, and J-decoupling in the indirect dimension. This results in high-precision distance measurements between aromatic side chains of three tyrosine residues and distant methyl groups in the hydrophobic core of the protein. Even in the absence of information on the relative orientation of the shift tensors, we obtain relatively high precision data, which can be further improved by additional constraints on the tensor orientations.
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multipole multimode floquet theory of Rotational Resonance width experiments 13c 13c distance measurements in uniformly labeled solids
Journal of Chemical Physics, 2006Co-Authors: Ramesh Ramachandran, Jozef R Lewandowski, Patrick C A Van Der Wel, Robert G GriffinAbstract:A formal description of zero-quantum (ZQ) NMR processes using multipole-multimode Floquet theory is proposed for studying polarization transfer in magic angle spinning experiments. Specifically, we investigate the factors affecting the accuracy and precision of 13C-13C distance measurements that are based on ZQ-magnetization exchange processes in Rotational Resonance width experiments. With suitable examples drawn from measurements in N-acetyl-[U-13C,15N]-L-valine-L-leucine, we substantiate our approach and propose methods for improving the accuracy and reliability of such 13C-13C distance measurements in uniformly 13C, 15N-labeled solids. In addition, the theoretical model presented in this article provides a more general framework for describing relaxation phenomena involving multiple decay rate constants in zero-quantum processes.
