Application Of Nuclear Magnetic Resonance Research Articles

A Programmable Pulse Sequence Generator for High Temperature Low-Field NMR Apparatus

The stable operation of pulse sequence generators at high temperatures (200°C) has been an important issue for some time in the application of nuclear magnetic resonance (NMR) apparatus for oil exploration. The application of system-in-package (SiP) technology was used to improve the temperature-resist grade of the hardware platform. A pulse sequence generator that meets the requirements of accurate phase and adjustable frequency during NMR apparatus in high temperature environments was designed and implemented. At ambient temperatures of up to 200°C, experimental results show that the delay times of the rising and falling edges of the pulse are 3.2 and 3.35 ns. respectively. The eye diagram Q factor of the critical path is not less than 15, and the Bit Error Rate (BER) is not more than 10–50. The experimental results show that a pulse sequence generator can meet the requirements of high temperature NMR apparatus, and can also provide a template for the design of an NMR pulse sequence generator for special fields of application, such as deep sea surveys and aviation.

Comparison of binding properties of a novel non-steroidal anti-inflammatory agent and ibuprofen to cyclooxygenase-1 and cyclooxygenase-2 enzymes by saturation transfer difference nuclear magnetic resonance

Saturation transfer difference nuclear magnetic resonance is a ligand-based screening technique that focuses directly on the physical interaction of a macromolecule (protein, enzyme, etc.) and a small ligand. It is a powerful tool in pharmaceutical research. Here, a comparison is reported of the binding characteristics of ibuprofen and a novel anti-inflammatory agent to cyclooxygenase-1 and cyclooxygenase-2 enzymes as an application of saturation transfer difference nuclear magnetic resonance. It has been shown that this novel agent is capable of binding to both isoforms of the cyclooxygenase enzymes. It has also been reported that novel agent binds better to cyclooxygenase-2.

Novel nested saddle coils used in miniature atomic sensors

A novel uniform magnetic field coil structure with two pairs of saddle coils nested is proposed in order to minish the aspect ratio without losing much field uniformity, which is significant in innovative miniature atomic instruments and sensors. Optimal configuration parameters are obtained from the Taylor expansion of the magnetic field. The remainder terms are used to estimate the field uniformity and optimize the configuration while minishing computation time. Compared with traditional saddle coils, the nested saddle coils have unique advantages in miniature applications where the aspect ratios are strictly limited. The optimized nested saddle coils were manufactured by Flexible Printed Circuit (FPC) technology and the magnetic field uniformities were verified experimentally using a flux-gate magnetometer. Furthermore, the example application of a miniature nuclear magnetic resonance (NMR) gyro demonstrates the practical use of the nested coils.

The Feasibility of Low Field NMR Technology in Geotechnical Engineering

In resent years, the nuclear magnetic resonance (NMR) technique has been applicated in a relatively small scale, which includes soil, rocks, coals, concrete and so on. In this paper, the auther indicate the theoretical background of NMR in short words and explain the measurement methods of T1 and T2 relaxation. Then the important parameters that have great impact of the result is emphasized. After introducing the representative research scope in soil, rocks, coals and concrete, the advantages and limitation of the NMR application are clear. Although the result of the NMR test is not accurate totally, the trend is correct and the accuracy is trusted in geotechnical engineering.

A Slice-based 13C-detected NMR Spin System Forming and Resonance Assignment Method.

Nuclear magnetic resonance (NMR) spectroscopy is attracting more attention in the field of computational structural biology. Till recently, 1H-detected experiments are the dominant NMR technique used due to the high sensitivity of 1H nuclei. However, the current availability of high magnetic fields and cryogenically cooled probe heads allow researchers to overcome the low sensitivity of 13C nuclei. Consequently, 13C-detected experiments have become a popular technique in different NMR applications especially resonance assignment and structure determination of large proteins. In this paper, we propose the first spin system forming method for 13C-detected NMR spectra. Our method is able to accurately form spin systems based on as few as two 13C-detected spectra, CBCACON, and CBCANCO. Our method picks slices from the more trusted spectrum and uses them as feedback to direct the slice picking in the less trusted one. This feedback leads to picking the accurate slices that consequently helps to form better spin systems. We tested our method on a real dataset of 'Ubiquitin' and a benchmark simulated dataset consisting of 12 proteins. We fed our spin systems as inputs to a genetic algorithm to generate the chemical shift assignment, and obtained 92 percent correct chemical shift assignment for Ubiquitin. For the simulated dataset, we obtained an average recall of 86 percent and an average precision of 88 percent. Finally, our chemical shift assignment of Ubiquitin was given as an input to CS-ROSETTA server that generated structures close to the experimentally determined structure.

Optimising magnetic resonance sampling patterns for parametric characterisation

Sampling strategies are often central to experimental design. Choosing efficiently which data to acquire can improve the estimation of parameters and reduce the acquisition time. This work is focused on designing optimal sampling patterns for Nuclear Magnetic Resonance (NMR) applications, illustrated with respect to the best estimate of the parameters characterising a lognormal distribution. Lognormal distributions are commonly used as fitting models for distributions of spin-lattice relaxation time constants, spin-spin relaxation time constants and diffusion coefficients. A method for optimising the choice of points to be sampled is presented which is based on the Cramér–Rao Lower Bound (CRLB) theory. The method’s capabilities are demonstrated experimentally by applying it to the problem of estimating the emulsion droplet size distribution from a pulsed field gradient (PFG) NMR diffusion experiment. A difference of <5% is observed between the predictions of CRLB theory and the PFG NMR experimental results. It is shown that CLRB theory is stable down to signal-to-noise ratios of ∼10. A sensitivity analysis for the CRLB theory is also performed. The method of optimizing sampling patterns is easily adapted to distributions other than lognormal and to other aspects of experimental design; case studies of optimising the sampling scheme for a fixed acquisition time and determining the potential for reduction in acquisition time for a fixed parameter estimation accuracy are presented. The experimental acquisition time is typically reduced by a factor of 3 using the proposed method compared to a constant gradient increment approach that would usually be used.

Recent Advances in NMR: Aggregation, Solvation, and Dynamics of Selected Organolithium Compounds

Nuclear magnetic resonance (NMR) spectroscopy is the most widely used analytical technique to study the structure and dynamics of organolithium compounds, which are the most popular reagents in organic synthesis due to their great diversity and high reactivity. The main strength of this method is that it allows direct analysis in solution of the aggregation, dynamic, and solvation state of reactive intermediates. In this review, we present the NMR tools (nD) involving the 6Li isotope and DOSY experiments with internal references and illustrate their contribution in the structural and dynamic characterization of organolithium compounds in solution through some selected example.1 Introduction2 Advantages of the 6Li isotope3 NMR Experiments Involving the 6Li Isotope4 Diffusion Ordered NMR Experiments5 Application of NMR to the Structural Characterization of Organolithium Species6 Conclusion

Morphology evolution and gelation mechanism of alkali induced konjac glucomannan hydrogel

A molecular-level mechanism of alkali induced konjac glucomannan (KGM) hydrogel gelation processing is considered with the application of nuclear magnetic resonance (NMR) spectroscopy and atomic force microscopy (AFM) as complementary methods to diffusive wave spectroscopy (DWS) microrheology and thermoanalysis. It is shown that deacetylation of KGM chains occurs immediately upon mixing with Na2CO3, inducing self-packaging. Partial unfolding of the packed loose structure of dehydrated KGM is observed upon heating. The configuration transition from random coils to self-assembling filament networks takes place before KGM aggregating to form large irreversible bundles with a lower degree of cross-linking. The gelation is not fulfilled until the temperature is increased to above 70 °C when the significant agglomeration is initiated among transitional fibrils to form junction zones essentially composed of acetyl-free portions. This suggests the intermolecular aggregation of KGM chains not simply regarding to hydrogen bonds, but essentially relating to hydrophobic interactions.

Application of high resolution NMR (1H and 13C) and FTIR spectroscopy for characterization of light and heavy crude oils

High-resolution nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy experiments were applied to obtain detailed information on the hydrocarbon chemistry of three light and three heavy crude oils. Quantitative fractions of aromatic molecules and functional groups constituting oil hydrocarbons were determined by 13C NMR spectroscopy and comparative analysis of the oil samples with different viscosity, origin and preliminary treatment. SARA composition and some important information about aromaticity, oxidation behavior, branching, aliphaticity and sulfurization of studied oil samples were obtained. Integral characteristics of high-resolution NMR and FTIR spectra have a great potential to study the structure and characterization of light and heavy crude oils, which could substitute present traditional fractionation procedures. Relationships between spectroscopic parameters obtained by high-resolution NMR and FTIR spectroscopy methods and crude oil compositions can be useful for fast prediction of crude oil properties due to different type of treatment, including thermal methods for enhanced oil recovery. Also quantitative proportions of functional groups obtained by NMR and spectral indices obtained by FTIR can be one of the criteria for developing fingerprint approach.

NMR derived water content from high magnetic susceptibility rock cuttings

Nuclear magnetic resonance (NMR) well logging is a well-established technique for in-situ fluid measurement. It is however not routinely used in the mining industry to quantify water content in high magnetic susceptibility iron ore rock cuttings because the ore’s magnetic properties adversely affect the measurement. In this study the relationship between NMR signal intensity and magnetic susceptibility is studied using a low magnetic field (2 MHz) benchtop NMR instrument. Magnetic susceptibility is commonly measured during well logging protocols and therefore could be used to correct and hence render quantitative NMR measurements of moisture content in iron ore. In this study NMR signal from water-saturated synthetic samples (magnetite/maghemite/hematite mixed with borosilicate glass beads) is measured as a function of iron content and magnetic susceptibility to obtain such a correlation. This correlation is then applied to iron ore rock cuttings. Comparison with gravimetric measurements show that a standard error of estimate of water content across all samples tested of 6.4 wt% using no correction, is reduced to 1.5 wt% using the corrections, corresponding to a relative error reduction from 47% to 11%. Additional comparison with whole rock cores shows that a higher magnetic susceptibility threshold for using the corrections is required for whole rock cores than for the rock cuttings, this difference requires further study. These results encourage the broad use of these types of correlations for NMR measurements of iron rich cuttings and application of NMR well logging to iron ore deposits.

Indirect detection of 10B (I = 3) overtone NMR at very fast magic angle spinning

The application of overtone nuclear magnetic resonance (OT NMR) to symmetric spin transitions of integer quadrupolar nuclei is of considerable interest since this transition is immune to the first-order quadrupolar interaction, thus resulting in narrow NMR lines. Owing to its roles in nature and its high natural abundance, 14N (I = 1) OT NMR has been explored, in which the indirect and/or direct acquisitions of 14N OT were experimentally demonstrated. However, other than 14N nucleus, no OT NMR observation of other integer quadrupolar nuclei has been reported in the literature. In this work, we extend the application of OT NMR to another integer quadrupolar nucleus, namely 10B (I = 3). However, this is not straightforward owing to the unfavorable characteristics of 10B isotope. Here, for the first time, we present the selective acquisition of 10B central (−1 ↔ +1) OT NMR via detection of 1H nuclei on perborate monohydrate sample. Numerical calculations are in a good agreement with the experimental results. Both show that the optimal sensitivity is achieved when the carrier frequency is applied at the second OT spinning sideband, i.e. an offset of twice of the spinning frequency from the center band.

A method to determine nuclear magnetic resonance (NMR) T2cutoff based on normal distribution simulation in tight sandstone reservoirs

The T2cutoff is an important input parameter in nuclear magnetic resonance (NMR) applications. The accuracy of the T2cutoff affects the prediction reliability of parameters associated with the identification and evaluation of formations. Current methods are based on regional statistics; they have limited applications and the predicted values are not always reliable. In this study, a total of 36 core samples, drilled from Triassic tight sandstone reservoirs of the southwest Ordos Basin in China, were used for laboratory NMR measurements under fully brine saturated and irreducible water conditions. Based on the morphological character analysis of experimental NMR T2 spectra, we demonstrate that NMR T2 spectra can be fully simulated using the normal distribution function. In addition, a new method was proposed, which can predict various T2cutoffs based on the morphological differences of NMR T2 spectra, and the irreducible water saturation (Swirr) was calculated, which represents the ratio of the sum volume of clay bound water and capillary bound water to total pore volume. The reliability of this method was verified by comparing the predicted T2cutoff and Swirr values with those of core NMR experimental results. Finally, we extended this method into field applications in several tight sandstone reservoirs in China. The results show that total T2 distributions of the formation were fully simulated by the normal distribution function, and various T2cutoff and Swirr values were precisely predicted. Meanwhile, tight sands permeability curves, predicted based on the Timur-Coates model, were also accurately estimated. The results of our study may be applied to improve tight sandstone reservoir identification and evaluation using NMR logs.

Application of Low Field Nuclear Magnetic Resonance to evaluate asphalt binder viscosity in recycled mixes

The newly developed method to estimate asphalt viscosity and aging trends using Low Field Nuclear Magnetic Resonance (LF-NMR) was applied to characterize the effect of incorporating recycled materials and recycling agents in asphalt mix samples. The measurements were conducted on asphalt mix samples prepared with different binders: (1) a virgin binder, (2) a recycled binder from Reclaimed Asphalt Pavement (RAP), (3) a blend of virgin and RAP binder (recycled blend) and (4) a rejuvenated blend that consists of the recycled blend with the addition of a recycling agent (tall oil). The LF-NMR measurements were performed at room (25 °C) and magnet (36.4 °C) temperatures. The Relative Hydrogen Index (RHI) obtained from LF-NMR captured the expected binder viscosity trends for the asphalt mix samples prepared with each of the different binders. The viscosity of the binders and blends was estimated from Dynamic Shear Rheometer (DSR) measurements. The relationship between dynamic viscosity and RHI agreed with previous findings. The samples prepared with the rejuvenated blend had lower viscosity and higher RHI than the recycled blend, indicating that the tall oil was effective in lowering its viscosity. Small discrepancies in the trends of the rejuvenated blend as compared to the virgin binder were attributed to their similar detectable hydrogen content, obtained in the rejuvenated blend with the addition of tall oil, but different oxidation state, molecular distribution and steric hindrance. This indicates that the LF-NMR method is more influenced by the chemistry of the asphalt binders rather than their viscosity. The asphalt mix samples with virgin and rejuvenated binders were also subjected to an aging treatment at 70 °C for a month. A significant decrease of the RHI was detected for the samples prepared with rejuvenated binder whereas no significant change was detected for those prepared with virgin binders, which indicates that rejuvenated binders were more susceptible to additional aging that resulted in increased viscosity.

NMR Spectroscopy in Glass Science: A Review of the Elements

The study of inorganic glass structure is critically important for basic glass science and especially the commercial development of glasses for a variety of technological uses. One of the best means by which to achieve this understanding is through application of solid-state nuclear magnetic resonance (NMR) spectroscopy, which has a long and interesting history. This technique is element specific, but highly complex, and thus, one of the many inquiries made by non-NMR specialists working in glass science is what type of information and which elements can be studied by this method. This review presents a summary of the different elements that are amenable to the study of glasses by NMR spectroscopy and provides examples of the type of atomic level structural information that can be achieved. It serves to inform the non-specialist working in glass science and technology about some of the benefits and challenges involved in the study of inorganic glass structure using modern, readily-available NMR methods.

Recent developments in nutrimetabolomics: from food characterisation to disease prevention

Applications of mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy in the discipline of metabolomics have gained increasing interest in the area of foodomics due to their ability to characterise the metabolome of complex matrices. In this review, we report recent studies that have applied NMR and MS-based metabolomics for improved detection of food frauds, the identification of dietary markers and to investigate the interconnection between metabolome and microbiome. Overall, the advent of these new state-of-the-art technologies is contributing to expand the body of knowledge on human physiology and inter-individual metabolic diversity, which is highly valuable in the context of personalised nutritional interventions.

High-resolution magnetic resonance spectroscopy using a solid-state spin sensor.

Quantum systems that consist of solid-state electronic spins can be sensitive detectors of nuclear magnetic resonance (NMR) signals, particularly from very small samples. For example, nitrogen-vacancy centres in diamond have been used to record NMR signals from nanometre-scale samples, with sensitivity sufficient to detect the magnetic field produced by a single protein. However, the best reported spectral resolution for NMR of molecules using nitrogen-vacancy centres is about 100 hertz. This is insufficient to resolve the key spectral identifiers of molecular structure that are critical to NMR applications in chemistry, structural biology and materials research, such as scalar couplings (which require a resolution of less than ten hertz) and small chemical shifts (which require a resolution of around one part per million of the nuclear Larmor frequency). Conventional, inductively detected NMR can provide the necessary high spectral resolution, but its limited sensitivity typically requires millimetre-scale samples, precluding applications that involve smaller samples, such as picolitre-volume chemical analysis or correlated optical and NMR microscopy. Here we demonstrate a measurement technique that uses a solid-state spin sensor (a magnetometer) consisting of an ensemble of nitrogen-vacancy centres in combination with a narrowband synchronized readout protocol to obtain NMR spectral resolution of about one hertz. We use this technique to observe NMR scalar couplings in a micrometre-scale sample volume of approximately ten picolitres. We also use the ensemble of nitrogen-vacancy centres to apply NMR to thermally polarized nuclear spins and resolve chemical-shift spectra from small molecules. Our technique enables analytical NMR spectroscopy at the scale of single cells.

NMR Methodologies for the Detection and Quantification of Nanostructural Defects in Silicone Networks

We present and discuss a sensitive spectroscopic means of detecting and quantifying network defects within a series of polysiloxane elastomers through a novel application of 19F solution state nuclear magnetic resonance (NMR). Polysiloxanes are the most utilized non-carbon polymeric material today. Their final network structure is complex, hierarchical, and often ill-defined due to modification. Characterization of these materials with respect to starting and age-dependent network structure is obfuscated by the intractable nature of polysiloxane network elastomers. We report a synthetic strategy for selectively tagging chain-end silanols with an organofluorine compound, which may then be conveniently and quantitatively measured as a function of structure and environment by means of 19F NMR. This study represents a new and sensitive means of directly quantifying aspects of network architecture in polysiloxane materials and has the potential to be a powerful new tool for the spectroscopic assessment of stru...

Dynamic Nuclear Polarization Opens New Perspectives for NMR Spectroscopy in Analytical Chemistry.

Dynamic nuclear polarization (DNP) can boost sensitivity in nuclear magnetic resonance (NMR) experiments by several orders of magnitude. This Feature illustrates how the coupling of DNP with both liquid- and solid-state NMR spectroscopy has the potential to considerably extend the range of applications of NMR in analytical chemistry.

A novel efficient inversion method for three-dimensional NMR and the optimization of activation sequences and acquisition parameters

A three-dimensional (3D) nuclear magnetic resonance (NMR) spectrum can simultaneously provide distributions of longitudinal relaxation time (T1), transverse relaxation time (T2), and diffusivity (D); thus, it greatly improves the capacity of fluid identification, typing, and quantitative evaluations. However, several challenges that significantly hinder the widespread application of this technique remain. The primary challenges are the high time and memory costs associated with the current 3D NMR inversion algorithms. In addition, an activation sequence optimization method for 3D NMR inversions has not been developed. In this paper, a novel inversion method for 3D NMR spectra and a detailed optimization method for activation sequences and acquisition parameters were proposed. The novel method, namely randomized singular value decomposition (RSVD) inversion algorithm, can reduce memory requirements and ensure computational efficiency and accuracy. Window averaging (WA) technique was also adopted in this study to further increase computational speed. The optimized method for pulse sequences is mainly based on projections of the 3D NMR spectra in the two-dimensional (2D) and one-dimensional (1D) domains. These projections can identify missing NMR properties of different fluids. Because of the efficiency and stability of this novel algorithm and the optimized strategy, the proposed methods presented in this paper could further promote the widespread application of 3D NMR.

Spectroscopic imaging: Nuclear magnetic resonance and Raman spectrometry for the detection of collagen cross-linking from giant squid mantle, fin, and tentacle tissues

ABSTRACTThe application of proton nuclear magnetic resonance (1H-NMR) imaging and Raman spectrometry is described for the detection and structural characterization of collagen cross-linking (pyridinoline) in soluble and insoluble collagen fractions obtained by cation-exchange separation of the mantle, fins, and tentacles of giant squid (Dosidicus gigas). The pyridinoline was detected using a fluorometric procedure only in the soluble collagen fractions. However, the pyridinoline was detected using high-performance liquid chromatography (HPLC) only in the insoluble collagen fraction from the tentacles. Meanwhile, in all samples, pyridinoline was detected by 1H-NMR and Raman spectrometry. The higher peak intensities in both methods were observed in the insoluble collagen fraction from the tentacles. The muscles showed a lower decrease in shear force after 30 min of cooking. 1H-NMR and Raman spectrometry provides an assay which is more sensitive than fluorescence and HPLC for pyridinoline detection in squid tissues, suggesting greater potential for the analysis of different types of tissue and collagen fractions.