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Journal of Magnetic Resonance

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https://www.readbyqxmd.com/read/30396157/peptide-bond-conformation-in-peptides-and-proteins-probed-by-dipolar-coupling-chemical-shift-tensor-correlation-solid-state-nmr
#1
Dwaipayan Mukhopadhyay, Chitrak Gupta, Theint Theint, Christopher P Jaroniec
Multidimensional magic-angle spinning solid-state NMR experiments are described that permit cis and trans peptide bonds in uniformly 13 C,15 N-labeled peptides and proteins to be unambiguously distinguished in residue-specific manner by determining the relative orientations of the amide 13 C' CSA and 1 H-15 N dipolar coupling tensors. The experiments are demonstrated for model peptides glycylglycine and 2,5-diketopiperazine containing trans and cis peptide bonds, respectively. Subsequently, the measurements are extended to two representative proteins that contain exclusively trans peptide bonds, microcrystalline B3 immunoglobulin domain of protein G and Y145Stop human prion protein amyloid fibrils, to illustrate their applicability to a wide range of protein systems...
October 30, 2018: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/30388701/two-dimensional-magnetization-transfer-cpmg-mri-reveals-tract-specific-signatures-in-fixed-rat-spinal-cord
#2
Teresa Serradas Duarte, Noam Shemesh
Multiexponential T2 (MET2 ) Relaxometry and Magnetization Transfer (MT) are among the most promising MRI-derived techniques for white matter (WM) characterization. Both techniques are shown to have histologically correlated sensitivity to myelin, but these correlations are not fully understood. Furthermore, MET2 and MT report on different WM features, thus they can be considered specific to different (patho)physiological states. Two-dimensional studies potentially resolving interactions, such as those commonly used in NMR, have been rarely performed in this context...
October 24, 2018: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/30396156/inner-product-nmr-spectroscopy-a-variant-of-covariance-nmr-spectroscopy
#3
Kazuyuki Takeda, Youta Kobayashi, Yasuto Noda, K Takegoshi
We propose a variant of covariance NMR spectroscopy, namely, inner-product NMR spectroscopy, originally suggested in Takeda (2015). The mathematical operation of inner-product NMR is the same as that of covariance NMR, except that subtraction of the average value of the variable is intentionally omitted, so that the correspondence of the spectrum with that of conventional two-dimensional Fourier-transformation is established without having to request the average to become vanishingly small. We demonstrate inner-product NMR for 13 C DARR correlation experiments in a polycrystalline sample of 13 C-labeled l-alanine...
October 23, 2018: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/30391869/optimized-coherence-selection
#4
Vesselin Z Miloushev, Arthur G Palmer
A theoretical framework for optimized coherence order selection in regards to cogwheel phase cycling is developed based on analysis of solutions of the associated homogeneous linear Diophantine equation. The empirical Hughes-Carravetta-Levitt conjectures are derived. A general formula is constructed that is guaranteed to provide valid phase cycles. Optimality of this formula is proven for non-sparse sets of coherence levels with relatively prime lower absolute bounds. Smaller phase cycles can be constructed when these conditions do not hold...
October 23, 2018: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/30380458/multi-resonant-photonic-band-gap-saddle-coil-dnp-probehead-for-static-solid-state-nmr-of-microliter-volume-samples
#5
Alexander A Nevzorov, Sergey Milikisiyants, Antonin N Marek, Alex I Smirnov
The most critical condition for performing Dynamic Nuclear Polarization (DNP) NMR experiments is achieving sufficiently high electronic B1e fields over the sample at the matched EPR frequencies, which for modern high-resolution NMR instruments fall into the millimeter wave (mmW) range. Typically, mmWs are generated by powerful gyrotrons and/or extended interaction klystrons (EIKs) sources and then focused onto the sample by dielectric lenses. However, further development of DNP methods including new DNP pulse sequences may require B1e fields higher than one could achieve with the current mmW technology...
October 23, 2018: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/30384129/nmr-supersequences-with-real-time-homonuclear-broadband-decoupling-sequential-acquisition-of-protein-and-small-molecule-spectra-in-a-single-experiment
#6
Veera Mohana Rao Kakita, Kavitha Rachineni, Mandar Bopardikar, Ramakrishna V Hosur
NOAH (NMR byOrderedAcquisition using 1 H-detection) type of pure shift NMR pulse scheme has been designed for the efficient utilization of magnetization that presents in a spin-system under consideration. The proposed strategy, PROSMASH-HSQC2 (PROtein-HSQC and SMAll molecule-HSQC Signals with Homodecoupling) uses the real-time BIRD pure shift NMR strategy and two HSQC spectra (13 C-HSQC for small molecules and 15 N-HSQC for 15 N-isotopic labelled proteins) can be recorded in a single NMR experiment. Thus, this method permits precise determination of drug-protein interactions at atomic levels by monitoring the chemical shift perturbations, and will have potential applications in drug discovery programs...
October 22, 2018: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/30380459/multiparametric-quantification-of-the-heterogeneity-of-free-ca-2-concentration-by-19-f-mr-spectroscopy
#7
Norbert W Lutz, Monique Bernard
For biological tissue that is heterogeneous with respect to free intracellular Ca2+ concentration ([Ca2+ ]i ), the lineshape of the 19 F MRS resonance of injected [Ca2+ ]-sensitive 4-FBAPTA or BAPTA-FF reflects the statistical distribution of [Ca2+ ]i values. While conventional 19 F MRS of these fluorinated Ca2+ reporter molecules only provides one [Ca2+ ]i value per spectrum, our specially designed lineshape analysis reveals at least eight quantitative statistical parameters (descriptors) characterizing the [Ca2+ ]i distribution within the observed tissue volume...
October 17, 2018: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/30366222/quantitative-measurement-of-t2-t1%C3%AF-and-t1-relaxation-times-in-articular-cartilage-and-cartilage-bone-interface-by-se-and-ute-imaging-at-microscopic-resolution
#8
Rohit Mahar, Syeda Batool, Farid Badar, Yang Xia
Both spin-echo (SE) and ultra-short echo (UTE) based MRI sequences were used on a 7 T µMRI system to quantify T2, T1ρ and T1 relaxation times from articular cartilage to the cartilage-bone interface on canine humeral specimens at 19.5 µm pixel resolution. A series of five relaxation-weighted images were acquired to calculate one relaxation map (T2, T1ρ or T1), from which the depth-dependent profiles were examined between the SE method and the UTE method, over the entire non-calcified cartilage and within the cartilage-bone interface...
October 12, 2018: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/30359907/implications-of-the-magnetic-susceptibility-difference-between-grey-and-white-matter-for-single-voxel-proton-spectroscopy-at-7-t
#9
Donghyun Hong, Jack J A van Asten, Seyedmorteza Rohani Rankouhi, Jan-Willem Thielen, David G Norris
Magnetic susceptibility differences between grey matter (GM) and white matter (WM) can potentially affect lineshapes and chemical shifts in single-voxel spectroscopy. This study aimed to investigate the consequences and potential utility of these effects. Spectroscopy voxels were segmented into GM, WM, and cerebrospinal fluid based on T1 -weighted images. GM and WM lineshapes were computed using multi-echo gradient-echo images to measure the frequency distribution. Twenty 7 Tesla single voxel spectra with corresponding T1 -weighted images were acquired from the frontal and parietal lobes from five healthy human volunteers...
October 12, 2018: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/30366223/onlyparahydrogen-spectrosopy-opsy-pulse-sequences-one-does-not-fit-all
#10
Andrey N Pravdivtsev, Frank Sönnichsen, Jan-Bernd Hövener
The hyperpolarization of nuclear spins using parahydrogen is an interesting effect that allows to increase the magnetic resonance signal by several orders of magnitude. Known as ParaHydrogen And Synthesis Allow Dramatically Enhanced Nuclear Alignment (PASADENA) and ParaHydrogen Induced Polarization (PHIP), the method was successfully used for in vitro analysis and in vivo imaging. In this contribution, we investigated four known and four new variants of Only Parahydrogen SpectroscopY (OPSY) sequences (Aguilar et al...
October 10, 2018: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/30359906/oxygen-induced-leakage-of-spin-polarization-in-overhauser-enhanced-magnetic-resonance-imaging-application-for-oximetry-in-tumors
#11
Artem A Gorodetskii, Timothy D Eubank, Benoit Driesschaert, Martin Poncelet, Emily Ellis, Valery V Khramtsov, Andrey A Bobko
Overhauser-enhanced Magnetic Resonance Imaging (OMRI) is a double resonance technique applied for oxygen imaging in aqueous samples and biological tissues. In this report, we present an improved OMRI approach of oxygen measurement using the single line "Finland" trityl spin probe. Compared to a traditional approach, we introduced an additional mechanism of leakage of spin polarization due to an interaction of a spin system with oxygen. The experimental comparison of the new approach with an oxygen-dependent leakage factor to a traditional approach performed in phantom samples in vitro, and mouse tumor model in vivo, shows improved accuracy of determination of oxygen and contrast agent concentrations...
October 10, 2018: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/30340203/rapid-detection-of-the-presence-of-diffusion-exchange
#12
Teddy X Cai, Dan Benjamini, Michal E Komlosh, Peter J Basser, Nathan H Williamson
Diffusion exchange spectroscopy (DEXSY) provides a detailed picture of how fluids in different microenvironments communicate with one another but requires a large amount of data. For DEXSY MRI, a simple measure of apparent exchanging fractions may suffice to characterize and differentiate materials and tissues. Reparameterizing signal intensity from a PGSE-storage-PGSE experiment as a function of the sum, bs =b1 +b2 , and difference bd =b2 -b1 of the diffusion encodings separates diffusion weighting from exchange weighting...
October 10, 2018: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/30347386/chemical-shift-reference-scale-for-li-solid-state-nmr-derived-by-first-principles-dft-calculations
#13
S S Köcher, P P M Schleker, M F Graf, R-A Eichel, K Reuter, J Granwehr, Ch Scheurer
For studying electrode and electrolyte materials for lithium ion batteries, solid-state (SS) nuclear magnetic resonance (NMR) of lithium moves into focus of current research. Theoretical simulations of magnetic resonance parameters facilitate the analysis and interpretation of experimental Li SS-NMR spectra and provide unique insight into physical and chemical processes that are determining the spectral profile. In the present paper, the accuracy and reliability of the theoretical simulation methods of Li chemical shielding values is benchmarked by establishing a reference scale for Li SS-NMR of diamagnetic compounds...
October 9, 2018: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/30316016/nmr-relaxation-in-porous-materials-at-zero-and-ultralow-magnetic-fields
#14
Michael C D Tayler, Jordan Ward-Williams, Lynn F Gladden
NMR detection in the ultralow-field regime (below 10 μT) was used to measure the nuclear spin relaxation rates of liquids imbibed into silica pellets with mean pore diameters in the 10-50 nm range. Heptane, formic acid and acetic acid were studied and relaxation rate data were compared with a conventional field-cycling NMR technique. Detection of 1 H-13 C spin coupling NMR signals at zero field (∼0.1 nT) allowed spectroscopic identification of molecules inside the porous material and unambiguous measurements of the chemistry-specific relaxation rates in liquid mixtures...
October 6, 2018: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/30366221/diffusion-effects-in-myelin-sheath-free-induction-decay
#15
F T Kurz, L R Buschle, A Hahn, J M E Jende, M Bendszus, S Heiland, C H Ziener
Myelin sheath microstructure and composition produce MR signal decay characteristics that can be used to evaluate status and outcome of demyelinating disease. We extend a recently proposed model of neuronal magnetic susceptibility, that accounts for both the structural and inherent anisotropy of the myelin sheath, by including the whole dynamic range of diffusion effects. The respective Bloch-Torrey equation for local spin dephasing is solved with a uniformly convergent perturbation expansion method, and the resulting magnetization decay is validated with a numerical solution based on a finite difference method...
October 4, 2018: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/30342370/a-versatile-custom-cryostat-for-dynamic-nuclear-polarization-supports-multiple-cryogenic-magic-angle-spinning-transmission-line-probes
#16
Faith J Scott, Nicholas Alaniva, Natalie C Golota, Erika L Sesti, Edward P Saliba, Lauren E Price, Brice J Albert, Pinhui Chen, Robert D O'Connor, Alexander B Barnes
Dynamic nuclear polarization (DNP) with cryogenic magic angle spinning (MAS) provides significant improvements in NMR sensitivity, yet presents unique technical challenges. Here we describe a custom cryostat and suite of NMR probes capable of manipulating nuclear spins with multi-resonant radiofrequency circuits, cryogenic spinning below 6 K, sample exchange, and microwave coupling for DNP. The corrugated waveguide and six transfer lines needed for DNP and cryogenic spinning functionality are coupled to the probe from the top of the magnet...
October 3, 2018: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/30326343/feedback-control-optimisation-of-esr-experiments
#17
David L Goodwin, William K Myers, Christiane R Timmel, Ilya Kuprov
Numerically optimised microwave pulses are used to increase excitation efficiency and modulation depth in electron spin resonance experiments performed on a spectrometer equipped with an arbitrary waveform generator. The optimisation procedure is sample-specific and reminiscent of the magnet shimming process used in the early days of nuclear magnetic resonance - an objective function (for example, echo integral in a spin echo experiment) is defined and optimised numerically as a function of the pulse waveform vector using noise-resilient gradient-free methods...
September 28, 2018: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/30296779/efficient-gpu-based-monte-carlo-simulation-of-diffusion-in-real-astrocytes-reconstructed-from-confocal-microscopy
#18
Khieu-Van Nguyen, Edwin Hernández-Garzón, Julien Valette
The primary goal of this work is to develop an efficient Monte-Carlo simulation of diffusion-weighted signal in complex cellular structures, such as astrocytes, directly derived from confocal microscopy. In this study, we first use an octree structure for spatial decomposition of surface meshes. Octree structure and radius-search algorithm help to quickly identify the faces that particles can possibly encounter during the next time step, thus speeding up the Monte-Carlo simulation. Furthermore, we propose to use a three-dimensional binary marker to describe the complex cellular structure and optimize the particle trajectory simulation...
September 27, 2018: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/30286413/real-time-j-upscaling-in-two-dimensional-pure-shift-diagonal-nmr-simultaneous-resolution-enhancement-in-chemical-shifts-and-scalar-couplings
#19
Veera Mohana Rao Kakita, Ramakrishna V Hosur
A two-dimensional real-time J-upscaled pure shift diagonal pulse scheme, JS-PSYCHE-DIAG has been developed. This method enhances the resolution in scalar coupling multiplets by real-time J-upscaling during the direct acquisition, and these J-upscaled multiplets resolve on the diagonal at the respective pure shift positions, which results in resolution enhancement in chemical shifts. Thus, both chemical shifts and scalar couplings get better resolved simultaneously in the same NMR experiment. The efficacy of the present method has been demonstrated, (i) on hesperidin for resolving the J-upscaled multiplets belonging to diastereomers and (ii) on a natural product, strychnine, to measure small scalar couplings including the long range values...
September 26, 2018: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/30292003/polarization-inversion-applied-to-proton-mas-nmr-spectroscopy-methylene-and-methine-free-proton-nmr-spectra
#20
Lokeswara Rao Potnuru, K V Ramanathan
Polarization-inversion (PI) has been applied to proton magic angle spinning (MAS) NMR spectra recorded under fast MAS conditions. The combination of cross-polarization (CP) from carbon to proton and subsequent polarization-inversion produces strong oscillatory behavior in the proton signal intensities at high MAS speeds of 60 kHz. It is observed that by a suitable choice of the polarization-inversion time, a proton spectrum free of methylene and methine protons can be obtained. Such a spectrum, on the one hand, increases the resolution of the crowded proton spectrum and on the other hand provides exclusively chemical shifts of protons such as NH, OH and SH which might otherwise overlap with carbon attached protons...
September 24, 2018: Journal of Magnetic Resonance
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