Nuclear Magnetic Resonance Detection Research Articles

Parahydrogen-induced polarization enables the single-scan NMR detection of a 236 kDa biopolymer at nanomolar concentrations

Nuclear magnetic resonance (NMR) experiments utilizing parahydrogen-induced polarization (PHIP) were performed to elucidate the PHIP activity of the synthetic 236 kDa biopolymer poly-γ-(4-propargyloxy)-benzyl-L-glutamate) (PPOBLG). The homopolypeptide was successfully hyperpolarized and the enhanced signals were detected in 11.7 T solution NMR as a function of the PPOBLG concentration. The hydrogenation with parahydrogen caused signal enhancements of 800 and more for the vinyl protons of the side chain at low substrate concentration. As a result of this high enhancement factor, even at 13 nM of PPOBLG, a single scan 1H-NMR detection of the hyperpolarized protons was possible, owing to the combination of hyperpolarization and density of PHIP active sites.

Preparation of ultracold ions in strong magnetic field and application to gas-phase NMR spectroscopy II

This paper presents a gas-phase nuclear magnetic resonance (NMR) apparatus, which may enable a tandem combination with an ion cyclotron resonance mass spectrometer. The NMR technique is widely used for analyzing the physical and chemical properties of materials; however, it is mostly limited to materials in condensed phases. Here, we construct a gas-phase NMR apparatus to extend this technique to gas-phase molecular ions. We outline the principle of NMR detection based on a Stern-Gerlach-type experiment and describe the experimental procedures and results for the preparation and manipulation of ultracold ions, which are fundamental for the proposed NMR detection. The development of the gas-phase NMR probe and radio-frequency excitation system and the features of the apparatus are presented. We also discuss the feasibility of combining this apparatus with an ion cyclotron resonance cell for realizing an NMR apparatus for mass-selected molecular ions briefly.

Fully Automated Characterization of Protein-Peptide Binding by Microfluidic 2D NMR.

We demonstrate an automated microfluidic nuclear magnetic resonance (NMR) system that quantitatively characterizes protein-ligand interactions without user intervention and with minimal sample needs through protein-detected heteronuclear 2D NMR spectroscopy. Quantitation of protein-ligand interactions is of fundamental importance to the understanding of signaling and other life processes. As is well-known, NMR provides rich information both on the thermodynamics of binding and on the binding site. However, the required titrations are laborious and tend to require large amounts of sample, which are not always available. The present work shows how the analytical power of NMR detection can be brought in line with the trend of miniaturization and automation in life science workflows.

Preparation of nano-selenium from chestnut polysaccharide and characterization of its antioxidant activity.

Chestnut is widely cultivated and has high nutritional value due to its richness in polysaccharides. In order to improve the antioxidant activity of chestnut polysaccharide, chestnut polysaccharide (CP) was extracted by ultrasonic-assisted water extraction and alcohol precipitation and purified by cellulose DEAE-52 exchange and Sephadex G-100 chromatography in this study. CP isolates were characterized by I2-KI reaction, three-strand helical structure analysis, infrared spectrum analysis, and nuclear magnetic resonance detection. The results showed that CP is a pyrylan sugar with triple helical structure and connected by α-glycosidic bonds, with sugar residues 1,4-α-D-Glcp, 1,6-α-D-Galp, 1,5-α-L-Araf, 1,4-α-L-Rhap, and 1,4-β-D-Glcp in the CP backbone. After purification, the branching structure, rod, and spherical structure were significantly increased, with reduced lamellar structure. The in vitro scavenging rates of CP at 10 mg·mL-1 against DPPH, hydroxyl radicals, and ABTS were 88.95, 41.38, and 48.16%, respectively. The DPPH free radical scavenging rate of purified polysaccharide fraction CP-1a was slightly enhanced, and the other rates showed a small decrease. Selenized chestnut polysaccharide (CP-Se) was prepared using nano-selenium method. The selenization method was optimized and stable Se-CP was obtained. When the concentration was 5 mg·mL-1, Se-CP had significantly higher scavenging abilities 89.81 ± 2.33, 58.50 ± 1.60, and 40.66 ± 1.91% for DPPH, hydroxyl radical, and ABTS radicals, respectively, than those of CP. The results of this study provide insight into the effects purification and selenization of chestnut polysaccharide on antioxidant activity, and also provide a theoretical basis for the development of chestnut polysaccharide for use in functional foods or health products.

NMR-BASED EXPERIMENTAL RESEARCH ON THE CHARACTERISTICS OF ROCK FRAGMENTATION BY BLASTING BASED ON POROSITY CHANGE

In this paper, the nuclear magnetic resonance detection technology is introduced to quantitatively identify the range of damage on the rock samples under different blasting conditions. This was accomplished by examining the rock breaking and the damage caused by the dynamic effect of explosive stress wave and the quasi-static effect of detonation gas. Two experimental conditions were undertaken: 1) blocked blasthole under the combined action of explosive stress wave and detonation gas; 2) non-blocked blasthole under the single action of explosive stress wave-with rock porosity and transverse relaxation time, T<sub>2</sub>, spectrum among other parameters used as the criteria. Nuclear magnetic resonance (NMR) detection technology intuitively was also used. The results of nuclear magnetic resonance were compared and verified with ultrasonic test, rock strength measurement, and numerical simulation tests of fluid-solid coupling. Results show that the range of damage under the combined action of explosive stress wave and detonation gas is larger than that under the single action of explosive stress wave. The quasi-static action of the explosive gas plays an important role in the process of rock breaking.

Mechanical damage characteristics and nondestructive testing techniques of fruits: a review

Fruits will be subjected inevitably to various external forces in the process of harvesting, transportation, processing, and storage, which will cause mechanical damage. The research on mechanical properties and damage mechanisms of fruit can effectively control its loss. In this study, fruits are divided into different types according to their morphology and structure. The impact, vibration, static pressure, and other mechanical damage on fruits are studied. It is important to identify the damaged parts of fruit after damage quickly and accurately. Therefore, this study analyzes the application of nondestructive testing technologies such as spectral detection technology, NMR (nuclear magnetic resonance) detection technology, and acoustic and electrical characteristics detection technology in fruit damage detection.

Metabolic signatures of lymphangioleiomyomatosis in biofluids: nuclear magnetic resonance (NMR)-based metabonomics of blood plasma: a case-control study.

Our aim was to analyze and compare the characteristics and differences of blood metabolites between lymphangioleiomyomatosis (LAM) patients and healthy controls, in order to find biomarkers that can be used for the diagnosis and classification of LAM. Between January 2020 to January 2022, 61 eligible LAM patients [51 sporadic LAM (S-LAM) and 10 tuberous sclerosis complex LAM (TSC-LAM)] from the First Affiliated Hospital of Guangzhou Medical University and 30 healthy controls were enrolled. Blood samples were taken for nuclear magnetic resonance (NMR) detection. Data analysis was performed by the umbrella program, and Wilcoxon analysis was used for comparisons between groups. The difference indicators were modeled by logistic regression. Diagnostic accuracy of the best predictive parameters was evaluated by the area under the receiver operating characteristic (ROC) curve (AUC), and the sensitivity and specificity were calculated. The indexes differed between LAM patients and healthy controls, S-LAM patients and healthy controls, and between TSC-LAM patients and healthy controls. There were two different metabolic indexes between S-LAM and TSC-LAM patients. After logistic regression modeling and ROC analysis, methionine (AUC =0.929, sensitivity =73.8%, specificity =100%, cut-off value =0.011 mmol/L) and acetic acid (AUC =0.966, sensitivity =95.1%, specificity =90%, cut-off value =0.006 mmol/L) had the highest diagnostic efficiency in LAM patients, and could be used to distinguish between affected and healthy people. Methionine was significantly associated with pneumothorax (P<0.05), and creatinine was significantly correlated with hysteromyoma (P<0.05). Methionine and acetic acid in the plasma of LAM patients are potential biomarkers. Methionine was also associated with pneumothorax in LAM patients. Also, acetone and creatinine were promising metabolic markers to distinguish S-LAM from TSC-LAM. NMR as a new non-invasive diagnostic method had a good discriminatory power for LAM.

Design of a cryogen-free high field dual EPR and DNP probe

We present the design and construction of a cryogen free, dual electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) probe for novel dynamic nuclear polarization (DNP) experiments and concurrent “in situ” analysis of DNP mechanisms. We focus on the probe design that meets the balance between EPR, NMR, and low temperature performance, while maintaining a high degree of versatility: allowing multi-nuclear NMR detection as well as broadband DNP/EPR excitation/detection. To accomplish high NMR/EPR performance, we implement a novel inductively coupled double resonance NMR circuit (1H-13C) in a solid state probe operating at cryogenic temperatures. The components of the circuit were custom built to provide maximum NMR performance, and the physical layout of this circuit was numerically optimized via magnetic field simulations to allow maximum microwave transmission to the sample for optimal EPR performance. Furthermore this probe is based around a cryogen free gas exchange cryostat and has been designed to allow unlimited experiment times down to 8.5 Kelvin with minimal cost. The affordability of EPR/DNP experiment is an extremely important aspect for broader impact with magnetic resonance measurements. The purpose of this article is to provide as complete information as we have available for others with interest in building a dual DNP/EPR instrument based around a cryogen-free cryostat.

Frémy's Salt as a Low-Persistence Hyperpolarization Agent: Efficient Dynamic Nuclear Polarization Plus Rapid Radical Scavenging.

Nuclear magnetic resonance (NMR) spectroscopy is a key technique for molecular structure determination in solution. However, due to its low sensitivity, many efforts have been made to improve signal strengths and reduce the required substrate amounts. In this regard, dissolution dynamic nuclear polarization (DDNP) is a versatile approach as signal enhancements of over 10 000-fold are achievable. Samples are signal-enhanced ex situ by transferring electronic polarization from radicals to nuclear spins before dissolving and shuttling the boosted sample to an NMR spectrometer for detection. However, the applicability of DDNP suffers from one major drawback, namely, paramagnetic relaxation enhancements (PREs) that critically reduce relaxation times due to the codissolved radicals. PREs are the primary source of polarization losses canceling the signal improvements obtained by DNP. We solve this problem by using potassium nitrosodisulfonate (Frémy's salt) as polarization agent (PA), which provides high nuclear spin polarization and allows for rapid scavenging under mild reducing conditions. We demonstrate the potential of Frémy's salt, (i) showing that both 1H and 13C polarization of ∼30% can be achieved and (ii) describing a hybrid sample shuttling system (HySSS) that can be used with any DDNP/NMR combination to remove the PA before NMR detection. This gadget mixes the hyperpolarized solution with a radical scavenger and injects it into an NMR tube, providing, within a few seconds, quantitatively radical-free, highly polarized solutions. The cost efficiency and broad availability of Frémy's salt might facilitate the use of DDNP in many fields of research.

A dual-axis high-order harmonic and single-axis phase-insensitive demodulation atomic magnetometer for in situ NMR detection of Xe

Based on the parametric oscillation process, we demonstrate the dual-axis phase-sensitive demodulation (PSD) and single-axis phase-insensitive demodulation (PISD) for the atomic magnetometer in an in situ nuclear magnetic resonance (NMR) detection system, which can separate the precession signals of NMR from the oscillating magnetic fields. The two orthogonal magnetic fields can be detected simultaneously and independently by selecting the optimal demodulation phases with the traditional PSD method. The response signals of the parametric modulation magnetometer demodulated with high order harmonic signals are evaluated, which is a new exploration. The first order harmonic demodulation can present the best sensitivity about 250 fT/Hz1/2. The high order harmonic demodulation technology supplies a twofold 3 dB bandwidth. With the PISD method, a single-axis demodulation technique is proposed. The transverse nuclear spin precession magnetic fields can be extracted effectively with the demodulation R signal outputs by setting a specific longitudinal modulation magnetic field amplitude, which is a new demodulation strategy compared with the traditional demodulation method for the NMR system.

Triaxial tests on high ductile concrete under different environmental conditions

AbstractTriaxial compression tests were conducted on high ductile concrete (HDC) under three curing conditions to study its triaxial mechanical properties under different curing environments. The three different curing conditions are as follows: standard curing (temperature 20 ± 2°C, humidity ≥95%), water curing (temperature 15 ± 2°C, humidity ≥95%), and −20°C (−20 ± 2°C, humidity ≥85%). The variation laws of stress–strain response, peak stress, peak strain, and volume strain were analyzed for HDC under different environmental conditions. The mechanism of the effect of HDC mesostructure on strength under different curing conditions was revealed using ultrasonic and nuclear magnetic resonance detection technology. The relationship between HDC uniaxial compressive strength and ultrasonic speed was obtained by fitting the test data, and the relationship between the shear strength and temperature was provided. Results show that the peak stress of HDC under the same confining pressure increases with the rise in the curing temperature. The peak strain also decreases, and the HDC exhibits better ductility under −20°C curing. The peak stress and peak strain of HDC under the same curing conditions increase with the rise in confining pressure. HDC specimen fracture is in the composite failure mode of shear and splitting, and it cracks but does not disintegrate. The pore size is larger and the strength is lower when the pores are more harmful.

Microanalytical characterizations, mechanical strength and water resistance performance of solidified dredged sludge with industrial solid waste and architecture residue soil

Industrial solid waste (slag, desulphurization gypsum, fly ash) and construction soil architecture residue soil are used to solidify dredged silt to develop a novel cover material. Through the application of shear, compressive, and permeability tests, shear strength parameters, unconfined compressive strength, volume shrinkage and hydraulic conductivity of the cured silt were assessed under the different curing times and wet-dry cycles conditions. The result shown slag played the most significant role in the silt consolidation process, followed by FGD gypsum and fly ash. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and nuclear magnetic resonance (NMR) detection methods were employed to determine the hydration products, chemical characteristics, microscopic morphology and pore structure of the solidified sludge, and identify the solidification mechanisms of the industrial waste and slag. After the wet and dry cycles, micropores and foramen (0.1–0.5 µm) continued to dominate pores, accounting for 64–76 % of pore space. Hydration products in the solidified sludge primarily consisted of C-S-H, C-A-S-H, and N-A-S-H gelled products, along with ettringite and zeolite.

NMR-Based Metabolomic Analysis of Plasma in Patients with Adult Congenital Heart Disease and Associated Pulmonary Arterial Hypertension: A Pilot Study.

Patients with unrepaired congenital heart disease (CHD) are prone to pulmonary arterial hypertension (PAH). The ovine pulmonary arterial smooth muscle cells exposed to increased pulmonary blood flow (PBF) exhibited hyperproliferation and metabolic alterations, but the metabolic disorders of patients with CHD and associated PAH (PAH-CHD) have not yet been fully understood. Adult CHD patients were prospectively included and divided into the PAH-CHD group (n = 24) and CHD group (n = 38), while healthy adults were included as healthy control (HC) group (n = 29). Plasma from each subject was prepared for nuclear magnetic resonance (NMR) detection. 1H-NMR spectra were acquired using 850 MHz NMR spectrometer. A total of 28 metabolites were identified from the NMR spectra and their relative concentrations were calculated and analyzed by multivariate and univariate statistical analyses and metabolic pathway analysis. Receiver operating characteristic (ROC) curve analysis and correlation analysis were performed to identify potential biomarkers and assess their roles in clinical assessment. Multivariate statistical analysis showed that the metabolic profile of PAH-CHD was altered relative to CHD or HC, while that of CHD was altered relative to HC. The identified characteristic metabolites were alanine, glucose, glycine, threonine and lactate, and the areas under the ROC curves (AUCs) were 0.769, 0.808, 0.711, 0.842 and 0.817, respectively. Multivariate ROC curve analysis showed AUCs ranging from 0.895 to 0.955 for the combination of these characteristic metabolites. The correlation analysis indicated that lactate and threonine were significantly correlated with mean pulmonary arterial pressure, pulmonary vascular resistance and N-terminal pro-B-type natriuretic peptide. The increased PBF could trigger global metabolic alterations in patients with CHD, which were more severe in patients with PAH-CHD. The characteristic metabolites have the potential to be biomarkers of PAH-CHD, which could be used for its noninvasive diagnosis, severity and prognosis assessment, thereby improving the management of PAH-CHD.

Sample-centred shimming enables independent parallel NMR detection

Two major technical challenges facing parallel nuclear magnetic resonance (NMR) spectroscopy, at the onset, include the need to achieve exceptional B_0 homogeneity, and good inter-detector radiofrequency signal decoupling, and have remained as technical obstacles that limit high throughput compound screening via NMR. In this contribution, we consider a compact detector system, consisting of two NMR ‘unit cell’ resonators that implement parallel B_0 shimming with parallel radiofrequency detection, as a prototype NMR environment, pointing the way towards achieving accelerated NMR analysis. The utility of our approach is established by achieving local field correction within the bore of a 1.05T permanent magnet MRI. Our forerunner platform suppresses signal cross-coupling in the range of -21 dB to -30 dB, under a geometrically decoupled scheme, leading to a halving of the necessary inter-coil separation. In this permanent magnet environment, two decoupled parallel NMR detector sites simultaneously achieve narrow spectral linewidth, overcoming the spatial inhomogeneity of the magnet from 400 to 28 Hz.

Molecular basis of secondary relaxation in stiff-chain glassy polymers.

Recent progress in establishing local order in polycarbonate-like glasses using rotational echo double resonance and centerband-only detection of exchange solid-state nuclear magnetic resonance (NMR) has stimulated a renewed attempt to connect molecular motion within glassy polymers and the mechanical properties of the glass. We have in fact established a correlation between molecular motion characterized by NMR and the mechanical secondary relaxation (tan δ) for nine polycarbonate-like glasses. All of the NMR and mechanical data are for T ≪ Tg. The resulting structural insights suggest that the chains of these polymers are simultaneously both Flory random coils and Vol'kenstein bundles. The cooperative motions of groups of bundles can be described qualitatively by a variety of constrained-kinetics models of the glass. All of the models share a common trait for large-amplitude motion: an exponential increase in the time required for an inter-bundle dilation event with a linear increase in bundle group size. This dependence and a locally ordered Vol'kenstein bundle lead to an understanding of the surprising 60° (K) shift of tan δ to higher temperature for ring-fluoro-polycarbonate relative to that of polycarbonate by the apparently minor substitution of a fluorine for a hydrogen on every fourth ring.

Investigation of 1H nuclear magnetic resonance relaxometry to screen metabolic syndrome and diabetes.

The purpose of this study was to investigate and compare the abilities of 1H nuclear magnetic resonance (NMR) transverse relaxation constant time (T2) and longitudinal relaxation constant time (T1) to screen people at the risk of diabetes and metabolic syndrome. Human blood samples were collected for NMR detection and biochemical examinations. Bivariate correlations, categorical analyses were performed to explore the relationship between NMR relaxation time and metabolic biomarkers. Results show that NMR relaxation time of human serum correlated well with some biomarkers associated with diabetes and metabolic syndrome. Statistically significant differences in NMR relaxation time between subjects with normal and poor metabolic health were observed. NMR relaxation time, especially T2, can be used to screen people at risk of diabetes and metabolic syndrome.

Rapid Detection of Avocado Oil Adulteration Using Low-Field Nuclear Magnetic Resonance.

Avocado oil (AO) has been found to be adulterated by low-price oil in the market, calling for an efficient method to detect the authenticity of AO. In this work, a rapid and nondestructive method was developed to detect adulterated AO based on low-field nuclear magnetic resonance (LF-NMR, 43 MHz) detection and chemometrics analysis. PCA analysis revealed that the relaxation components area (S23) and relative contribution (P22 and P23) were crucial LF-NMR parameters to distinguish AO from AO adulterated by soybean oil (SO), corn oil (CO) or rapeseed oil (RO). A Soft Independent Modelling of Class Analogy (SIMCA) model was established to identify the types of adulterated oils with a high calibration (0.98) and validation accuracy (0.93). Compared with partial least squares regression (PLSR) models, the support vector regression (SVR) model showed better prediction performance to calculate the adulteration levels when AO was adulterated by SO, CO and RO, with high square correlation coefficient of calibration (R2C > 0.98) and low root mean square error of calibration (RMSEC < 0.04) as well as root mean square error of prediction (RMSEP < 0.09) values. Compared with SO- and CO-adulterated AO, RO-adulterated AO was more difficult to detect due to the greatest similarity in fatty acids’ composition being between AO and RO, which is characterized by the high level of monounsaturated fatty acids and viscosity. This study could provide an effective method for detecting the authenticity of AO.

Simulation and experimental research on ultrasonic vibration high temperature rock

Ultrasonic vibration technology as a new type of auxiliary lithotripsy technology, a lot of research on this technology. However, at present, the effect of rock temperature on ultrasonic vibration of rock breaking has not been studied. Therefore, with the help of numerical simulation software, nuclear magnetic resonance detection and penetrant testing methods, it is necessary to complete the numerical simulation and laboratory testing of granite at different temperatures under ultrasonic vibration with granite as the research object. The main results are as follows:1. Under ultrasonic vibration, the number of rock cracks will increase with increasing temperature. And the fracture azimuth intensity in the rock model is 90°concentrated. 2. As the temperature increases, the accumulated thermal damage will promote the large number of expansion and connection of certain internal cracks, resulting in the macroscopic destruction of the rock sample and the increase in crack volume. 3. With the increase of temperature, the increase of porosity of rock samples under ultrasonic vibration has a staged characteristic. And 150 °C is the threshold. The significance of this research is to provide theoretical and technical support for the application of ultrasonic vibration technology in the future hard rock geological exploration and deep resource mining.

NMR Detection and Structural Modeling of the Ethylene Receptor LeETR2 from Tomato.

The gaseous plant hormone ethylene influences many physiological processes in plant growth and development. Plant ethylene responses are mediated by a family of ethylene receptors, in which the N-terminal transmembrane domains are responsible for ethylene binding and membrane localization. Until now, little structural information was available on the molecular mechanism of ethylene responses by the transmembrane binding domain of ethylene receptors. Here, we screened different constructs, fusion tags, detergents, and purification methods of the transmembrane sensor domain of ethylene receptors. However, due to their highly hydrophobic transmembrane domain (TMD), only a KSI-fused LeETR21–131 from tomato yielded a good-quality nuclear magnetic resonance (NMR) spectrum in the organic solvent. Interestingly, a dimer model of LeETR21–131 built by the AlphaFold2 algorithm showed greatly converged structures. The interaction analysis of ethylene and LeETR21–131 using molecular docking and molecular dynamics (MD) simulations demonstrated the potential binding sites of ethylene in LeETR21–131. Our exploration provides valuable knowledge for further understanding of the ethylene-perception process in ethylene receptors.

Optimization of Inside-Out Nuclear Magnetic Resonance Sensor With Logging-While-Drilling Tool Specification and Experimental Validation

The sensor determines the basic performance of the nuclear magnetic resonance (NMR) logging-while-drilling (LWD) system. However, the electromagnetic calculation and structure optimization of the sensor are complicated and difficult. In this study, we proposed an effective design method for inside-out NMR LWD sensor from the perspective of electromagnetic filed. First, a region of interest (ROI) was set first, the static magnetic field strength range in ROI corresponding to the ideal operating frequency bandwidth was defined as sensitive region, and the magnet system was optimized efficiently by introducing uniform design method to maximize the sensitive region. Different simplified finite element models were established to calculate different electromagnetic parameters of the RF coil system. The inside-out NMR LWD sensor was processed. Static magnetic field measurement result show that the proposed static magnetic field optimization method can effectively obtain the sensitive region with ideal radial position and strength, and is superior to the traditional optimization method. The NMR signal detection ability was tested by importing the Carr–Purcell–Meiboom–Gill (CPMG) sequence and phase-alternate pulse sequence technology. In particular, a porous and radially layered measurement device was designed, the signal sensitive region was quantitatively measured based on changes in sample porosity, and the width and height of signal sensitive region are 50 mm and 90 mm, respectively. The differences between static magnetic field sensitive region and signal sensitive region were analyzed, and suggestions for improving the sensor optimization method were provided at last.