Time-domain Nuclear Magnetic Resonance Research Articles

Datasets of seed mucilage traits for Arabidopsis thaliana natural accessions with atypical outer mucilage

The seeds of Arabidopsis thaliana become encapsulated by a layer of mucilage when imbibed. This polysaccharide-rich hydrogel is constituted of two layers, an outer layer that can be easily extracted with water and an inner layer that must be examined in situ in order to study its properties and structure in a non-destructive manner or disintegrated through hydrolysis or physical means in order to analyze its constituents. Mucilage production is an adaptive trait and we have exploited 19 natural accessions previously found to have atypical and varied outer mucilage characteristics. A detailed study using biochemical, histological and Time-Domain NMR analyses has been used to generate three related datasets covering 33 traits measured in four biological replicates. This data will be a rich resource for genetic, biochemical, structural and functional analyses investigating mucilage constituent polysaccharides or their role as adaptive traits.

Single-sided Time Domain-Nuclear Magnetic Resonance to Study the Effect of Cell Membrane Electroporation on the Water Mobility in Vegetal Tissues

This paper presents the characteristics of potato and apple tissues, with/out electroporation, by Time Domain-Nuclear Magnetic Resonance (TD-NMR). A portable TD-NMR was used to measure the proton relaxation time, T2, and the changes in the cells due to molecular water mobility of potato tubers,-NMR to identify the modifications that occurred at the cell level involving water molecules mobility in potato tubers and apple tissues after the electroporation treatment and compared with non-electroporated ones. The comparisons with normal potato and apple tissue and preliminary measurements in bulk were performed. Samples were also analyzed in terms of conductivity of the tissue and microscopic morphology. The results indicate that the electroporation process effect is identified with a variation of the peak position in T2 distribution, associated with sub-cell modifications.

Effect of CO2-brine-rock reactions on pore architecture and permeability in dolostone: Implications for CO2 storage and EOR

Geologic carbon sequestration (GCS) is considered a feasible technology for storing substantive volumes of greenhouse gases in subsurface geological formations. In the reservoir, far from carbon dioxide (CO2) injection wells or in post-injection scenarios, diffusion dominates over advection. This condition conjoins with spatially distributed geochemical reactions to induce heterogeneous changes in pore architecture, i.e. pore body and throat sizes or surface roughness. These changes can affect CO2 transport properties and storage capacity. In this work, we investigated mineral dissolution and precipitation in dolomite samples saturated with a CO2-saturated brine at 93 °C and 34.5 MPa, aged without flow. Two rock types samples, i.e. intergranular- and vuggy-dominant, were selected to investigate changes in pore size, porosity and permeability under reactive conditions. Mineral dissolution and precipitation were characterized using scanning electron microscopy. Changes in pore size were quantified via time-domain nuclear magnetic resonance (TD-NMR) transverse relaxation time (T2) and diffusion coefficient (D) distributions. We show that mineral dissolution likely occurs in highly permeable pathways. These observations are confirmed through analysis of (T2) and diffusion coefficient (D) distributions. In contrast to results during CO2-enriched brine continuous injection, mineral precipitation was observed in micropores. The leftward shift of the T2 peaks, corresponding to micropores, also evidenced mineral precipitation in low-permeability zones. However, microscale alterations resulted only in a subtle increase in porosity and permeability. Results in this study shed light on effects of geochemical reactions on alteration of rock properties in diffusion-dominated regions during CO2 storage.

Characterisation of Fat Crystal Polymorphism in Cocoa Butter by Time-Domain NMR and DSC Deconvolution.

The polymorphic state of edible fats is an important quality parameter in fat research as well as in industrial applications. Nowadays, X-ray diffraction (XRD) is the most commonly used method to determine the polymorphic state. However, quantification of the different polymorphic forms present in a sample is not straightforward. Differential Scanning Calorimetry (DSC) is another method which provides information about fat crystallization processes: the different peaks in the DSC spectrum can be coupled to the melting/crystallisation of certain polymorphs. During the last decade, nuclear magnetic resonance (NMR) has been proposed as a method to determine, qualitatively and/or quantitatively, the polymorphic forms present in fat samples. In this work, DSC- and NMR-deconvolution methods were evaluated on their ability to determine the polymorphic state of cocoa butter, with XRD as a reference method. Cocoa butter was subjected to two different temperature profiles, which enforced cocoa butter crystallization in different polymorphic forms. It was found that XRD remains the best method to qualitatively determine the polymorphic state of the fat. Whereas the quantitative NMR and DSC deconvolution results were not fully in line with the XRD results in all cases, NMR deconvolution showed great promise both in a qualitative and quantitative way.

Single-Laboratory Validation Study of a Rapid TD-NMR Method for Quantitation of Total Fat in Sunflower Oil Powder.

A rapid total fat quantitation method for sunflower oil powder was developed using time-domain nuclear magnetic resonance (TD-NMR). Currently, industry has three major methods for the total fat quantitation: gravimetric analysis after ether extraction (AOAC Methods 933.05 and 989.05), gas chromatography with flame ionization detector (GC-FID; AOAC Method 996.06), and High-resolution NMR. The gravimetric analysis method takes a day using highly flammable solvents, and the GC-FID method takes two days requiring harsh chemicals for hydrolyzation, extraction, and methylation. The High-resolution NMR spectroscopy method requires simpler sample preparation and shorter analysis time compared to the other two methods. Often, the only required sample preparation step is to dissolve a sample in a solvent. The acquisition time depends on types of analyzing nuclei and sample. The vegetable oil analysis by 13C NMR takes about 4 h per sample. 1H NMR usually takes less time to analyze. In contrast, the TD-NMR relaxometry method takes only 1 h to prepare and analyze samples if the test is for total fat only. The acquisition time is 40 s per sample, and samples are analyzed "as is". A rapid analysis method in a quality control laboratory is very crucial for laboratory efficiency in releasing products. In this paper, a single-laboratory validation study is described for a rapid TD-NMR method to quantitate total fat in sunflower oil powder. This validation work is to provide documented evidence for the method validity as well as the method performance. The method used a Bruker minispec mq-20 NMR analyzer® with minispec plus® software. A Hahn echo pulse program was used in the method to collect spin echo signal to determine total fat content. The linearity/range result from 10 standards (0, 21, 42, 63, 83, 92, 100, 108, 117, and 125%) has coefficients of determination (R2) of 1.0000. The 100% level is 1.2 g-fat in 2.5 g sample, which is targeted fat content in a sunflower oil powder raw material. The method is specific for the quantitation of total fat in sunflower oil powder with no background interference from the matrix. The precision result of the 6 replicate samples at 100% level is 0.3% RSD. The accuracies measured from triplicate analysis of 80, 100, and 120% sample matrices are 100, 100, and 100% average recoveries, respectively. The ruggedness of the test method is 0.4% RSD of 12 analysis from 2 analysts (6 results from each analyst) on the different days. The test method is proven to be specific, linear, precise, accurate, rugged, and suitable for the intended use of quantitative analysis for total fat in sunflower oil powder. Traditional methods of gravimetric or GC-FID for total fat analysis of raw materials require lengthy sample preparation and experiment time. Laboratory needs to spend a day to perform gravimetric analysis following ether extraction method and 2 days for the GC-FID method. In addition, these test methods use highly flammable and harsh chemicals that generate hazardous chemical wastes. These hazardous wastes are harmful to analysts and environments. In contrast, the TD-NMR method is safe, environmentally friendly, and fast. Therefore, TD-NMR is a preferred method for quality control laboratories.

Physicochemical properties of wet-glycated soy proteins

On a lab-scale, glycation is generally a lengthy process that would be costly if replicated on an industrial scale. In this study, a simplified method for glycating soy protein isolate has been developed. Soy proteins were glycated with allulose, fructose, and glucose in the presence of water. Free amino group content, protein solubility, browning index, and reducing sugar concentration were measured for the glycated proteins. Fourier Transform Infrared (FT-IR) spectroscopy was used to examine structural changes, and hydration behavior was evaluated using Time Domain Nuclear Magnetic Resonance (TD-NMR) relaxometry through T2 relaxation time measurements. The results showed that proteins could be glycated under these austere conditions and with minimal control. It was found that high temperatures were not favorable for glycation, and lower temperatures could be preferred. At high temperatures, proteins become more denatured and less soluble, as shown through the Lowry method for protein solubility and TD-NMR results. Higher browning was observed at a higher temperature, primarily when allulose and fructose were used for glycation. The highest glycation was obtained with glucose, while allulose and fructose showed the lowest reactivity under the proposed conditions. Proteins with low solubility had longer T2 relaxation times, indicating more free water and weaker water-binding capability.

Selection of industrial tomatoes using TD-NMR data and computational classification methods

Tomato processing chain has a world economic relevance for the food industry and the agribusiness, providing ready-to-eat products and raw material for other production chains. The product quality is depending on control of some fruit attributes, such as color, soluble solids content (SSC), and defects. The aim of this study was to develop accurate and nondestructive classification models according to the tomato maturation stage, SSC, and presence of defects using Time-Domain Nuclear Magnetic Resonance (TD-NMR) associated with computational classification methods. Each class showed different decay times. Green tomatoes showed a shorter decay signal than red tomatoes, mainly due to the relaxation signal being related to the water mobility in different vegetable tissue compartments. Classification models resulted in great accuracy performances, the best accuracy for each classification were: maturity index: 97% (SVM); SSC: 100% (SVM and kNN); presence of defects: 90% (PLS-DA). These results show that CPMG decays associated with computational methods can be used in the tomato processing industry to classify tomato samples. These classification models showed the potential of TD-NMR technique in a high-throughput screening application before the processing.

Spotting Frozen Curd in PDO Buffalo Mozzarella Cheese Through Insights on Its Supramolecular Structure Acquired by 1H TD-NMR Relaxation Experiments

The addition of frozen curd (FC) during the production process of “Mozzarella di Bufala Campana”, an Italian cheese with Protected Designation of Origin (PDO), is a common fraud not involving modifications of the chemical composition in the final product. Its detection cannot thus be easily obtained by common analytical methods, which are targeted at changes in concentrations of diagnostic chemical species. In this work, the possibility of spotting this fraud by focusing on the modifications of the supramolecular structure of the food matrix, detected by time domain nuclear magnetic resonance (TD-NMR) experiments, was investigated. Cheese samples were manufactured in triplicate, according to the PDO disciplinary of production, except for using variable amounts of FC (i.e., 0, 15, 30, and 50% w/w). Relaxation data were analysed through different approaches: (i) Discrete multi-exponential fitting, (ii) continuous Laplace inverse fitting, and (iii) chemometrics approach. The strategy that lead to best detection results was the chemometrics analysis of raw Carr-Purcell-Meiboom-Gill (CPMG) decays, allowing to discriminate between compliant and adulterated samples, with as low as 15% of FC addition. The strategy is based on the use of machine learning for projection on latent structures of raw CPMG data and classification tasks for fraud detection, using quadratic discriminant analysis. By coupling TD-NMR raw decays with machine learning, this work opens the way to set up a system for detecting common food frauds modifying the matrix structure, for which no official authentication methods are yet available.

Microwave glycation of soy protein isolate with rare sugar (D-allulose), fructose and glucose

Glycation, the initial step of Maillard reaction, can be used to modify the properties of proteins. In this study, to speed up the reaction, microwave glycation of soy protein isolate (SPI) in an aqueous medium with fructose, glucose, and D-allulose (rare sugar) were performed at pH 7 and pH 10 and the results were compared with the conventional ‘water bath glycation’ method. The reducing sugar concentration of glycated protein was quantified by High Performance Liquid Chromatography (HPLC) experiments and the structural changes of the soy protein isolate after glycation were investigated by Fourier Transform Infrared spectroscopy (FT-IR) and Time Domain Nuclear Magnetic Resonance (TD-NMR) relaxometry. Alkaline pH was found to be more effective for microwave glycation of soy protein isolate. The reactivity of sugars for microwave glycation reaction was ordered as D-allulose > fructose > glucose. According to the results, microwave heating was found to be more effective for glycation of SPI than water bath heating. NMR relaxometry results provided valuable information about structural characteristics and water mobility in the system.

Low field, time domain NMR in the agriculture and agrifood sectors: An overview of applications in plants, foods and biofuels

In this contribution, a selective overview of low field, time-domain NMR (TD-NMR) applications in the agriculture and agrifood sectors is presented. The first applications of commercial TD-NMR instruments were in food and agriculture domains. Many of these earlier methods have now been recognized as standard methods by several international agencies. Since 2000, several new applications have been developed, using state of the art instruments, new pulse sequences and new signal processing methods. TD-NMR is expected, in the coming years, to become even more important in quality control of fresh food and agricultural products, as well as for a wide range of food-processed products. TD-NMR systems provide excellent means to collect data relevant for use in the agricultural environment and the bioenergy industry. Data and information collected by TD-NMR systems thus may support decision makers in business and public organizations.

Perspectives in process analytics using low field NMR

Low field NMR is a powerful analytical tool which creates an enormous added value in process analytics. Based on specific applications in process analytics and perspectives for low field NMR in form of spectroscopy, relaxation, diffusion, and imaging in quality control, diverse applications and technical realizations like spectrometers, time domain NMR, mobile NMR sensors and MRI will be discussed.

Dissociable effects of dietary sodium in early life upon somatic growth, fluid homeostasis, and spatial memory in mice of both sexes.

Postnatal growth failure is a common morbidity for preterm infants and is associated with adverse neurodevelopmental outcomes. Although sodium (Na) deficiency early in life impairs somatic growth, its impact on neurocognitive functions has not been extensively studied. We hypothesized that Na deficiency during early life is sufficient to cause growth failure and program neurobehavioral impairments in later life. C57BL/6J mice were placed on low- (0.4), normal- (1.5), or high- (3 g/kg) Na chow at weaning (PD22) and continued on the diet for 3 wk (to PD40). Body composition and fluid distribution were determined serially by time-domain NMR and bioimpedance spectroscopy, and anxiety, learning, and memory were assessed using the elevated plus maze and Morris water maze paradigms in later adulthood (PD63-PD69). During the diet intervention, body mass gains were suppressed in the low- compared with normal- and high-Na groups despite similar caloric uptake rates across groups. Fat mass was reduced in males but not in females fed low-Na diet. Fat-free mass and hydration were significantly reduced in both males and females fed the low-Na diet, although rapidly corrected after return to normal diet. Measures of anxiety-like behavior and learning in adulthood were not affected by diet in either sex, yet memory performance was modified by a complex interaction between sex and early life Na intake. These data support the concepts that Na deficiency impairs growth and that the amount of Na intake which supports optimal somatic growth during early life may be insufficient to fully support neurocognitive development.

Asymmetric Co-unit Inclusion in Statistical Copolyesters

The biodegradation of isodimorphic random butanediol-succinate/adipate copolymers (PBSAs) can be affected by a change in the semicrystalline morphology. A crucial point for the final semicrystalline structure is the incorporation of monomers of the minority component into the crystals of the majority component. We use proton time-domain NMR and wide-angle X-ray scattering to characterize the copolymers across their complete composition range and analyze the possible inclusion of minority comonomers in the PBA-rich 20/80 and the PBS-rich 60/40 composition by applying different solid-state 13C NMR experiments. For the PBA-rich copolymers, we find a nearly constant volumetric crystallinity of 50% up to the 50/50 composition combined with an increase of the crystalline lamella thickness. NMR has detected the BS units incorporated into the BA crystalline structure, where on average every tenth monomer is a BS comonomer. In PBS-rich crystals, the crystallinity and crystallite thickness decrease from neat PBS to PBSA 60/40 by 37% and ∼20%, respectively. We also find evidence that the BA units are excluded from the bulk crystal but accumulate at the crystallite surface. The amount of BA units in these pocket-like structures can be estimated to be 7–9% of the BA comonomer content.

The exposome paradigm to predict environmental health in terms of systemic homeostasis and resource balance based on NMR data science.

The environment, from microbial ecosystems to recycled resources, fluctuates dynamically due to many physical, chemical and biological factors, the profile of which reflects changes in overall state, such as environmental illness caused by a collapse of homeostasis. To evaluate and predict environmental health in terms of systemic homeostasis and resource balance, a comprehensive understanding of these factors requires an approach based on the “exposome paradigm”, namely the totality of exposure to all substances. Furthermore, in considering sustainable development to meet global population growth, it is important to gain an understanding of both the circulation of biological resources and waste recycling in human society. From this perspective, natural environment, agriculture, aquaculture, wastewater treatment in industry, biomass degradation and biodegradable materials design are at the forefront of current research. In this respect, nuclear magnetic resonance (NMR) offers tremendous advantages in the analysis of samples of molecular complexity, such as crude bio-extracts, intact cells and tissues, fibres, foods, feeds, fertilizers and environmental samples. Here we outline examples to promote an understanding of recent applications of solution-state, solid-state, time-domain NMR and magnetic resonance imaging (MRI) to the complex evaluation of organisms, materials and the environment. We also describe useful databases and informatics tools, as well as machine learning techniques for NMR analysis, demonstrating that NMR data science can be used to evaluate the exposome in both the natural environment and human society towards a sustainable future.

Development of a TD-NMR Method to Monitor Brazil Nuts Oil Content: A Green and Low-Cost Based Approach

Growth in the international popularity of Brazil nuts oil (Bertholletia excelsa, Bonpl.) has demanded a closer look at quality aspects of the nuts. In this context, time-domain 1H nuclear magnetic resonance spectroscopy (TD-NMR) can be a useful tool for assessing the lipid portion of such matrices. In this work, a TD-NMR method was developed and validated to assess the oil content directly from Brazil nuts following the ISO 10565:1998 and DOQ-CGCRE-008. Full validation was addressed covering the working range from 0.67 to 25.00 g (coefficient of determination, R2 = 0.9993). Limits of detection (LOD) and quantification (LOQ) were 0.20 and 0.67 g, respectively. The repeatability and intermediate precision assays met the guide requirements. Oil contents obtained in two laboratories (different equipment) were statistically similar (66.93 ± 4.69 and 70.13 ± 4.15%), highlighting the method’s robustness. The developed approach has the potential to be adopted as an industrial reference method for in situ monitoring of Brazil nuts oil contents.

Recent Low-field Time-domain NMR Spectroscopy and its Application on Analysis of Rubber Structural Change

Recent Low-field Time-domain NMR Spectroscopy and its Application on Analysis of Rubber Structural Change

Fast-forward approach of time-domain NMR relaxometry for solid-state chemistry of chitosan

Chitosans with different average degrees of acetylation and weight molecular weight were analyzed by time-domain NMR relaxometry using the recently proposed pulse sequence named Rhim and Kessemeier - Radiofrequency Optimized Solid-Echo (RK-ROSE) to acquire 1H NMR signal of solid-state materials. The NMR signal decay was composed of faster (tenths of μs) and longer components, where the mobile-part fraction exhibited an effective relaxation transverse time assigned to methyl hydrogens from N-acetyl-d-glucosamine (GlcNAc) units. The higher intrinsic mobility of methyl groups was confirmed via DIPSHIFT experiments by probing the 1H-13C dipolar interaction. RK-ROSE data were modeled by using Partial Least Square (PLS) multivariate regression, which showed a high coefficient of determination (R2 > 0.93) between RK-ROSE signal profile and average degrees of acetylation and crystallinity index, thus indicating that time-domain NMR consists in a promising tool for structural and morphological characterization of chitosan.

Change of lamellar morphology upon polymorphic transition of form II to form I crystals in isotactic Polybutene-1 and its copolymer

Morphology and domain sizes in isotactic polybutene-1 homopolymer (iPB-1) and (butene-1)-ethylene random copolymer (iPB-1/C2) are studied by spin-diffusion time-domain 1H NMR and SAXS experiments. Lamellar thickness is smaller for iPB-1/C2 than for iPB-1 and decreases with decreasing crystallization temperature. iPB-1/C2 with form I’ crystals, which were directly formed upon crystallization from a heterogeneous melt, has typical for polyolefins lamellar morphology with the crystal-amorphous interface that separates crystal lamellae and interlamellar amorphous domains. Different lamellar structure is observed in iPB-1 and iPB-1/C2 with form I crystals which were obtained upon polymorphic phase transition from form II to form I crystals. The phase transition causes fragmentation of crystal lamellae into small blocks with a wide size distribution as was shown by the NMR method. Two types of the interface are present in these samples: the inner interface that separates crystal blocks within fragmented crystal lamellae, and the crystal-amorphous interface on the surface of fragmented lamellae. The molecular mechanism of polymorphic form II to form I phase transition is proposed. High chain mobility in form II crystals and chain folding structure on the lamellar surface play significant role at the initial and final stages of the restructuring of crystal lamellae during the phase transition, respectively.

Pre-treatment impact on the disposition of water in clay-based geopolymer

The effect of pre-treatment of low grade waste clay on the disposition of the water in clay based geopolymer has been investigated. The condition of the clay was untreated, calcined, and mechanically activated. Two different curing conditions were applied: ambient curing over 24 ​h and 120 ​°C over a 6 ​h. Time-domain NMR, FTIR, and EDS were used to study the water disposition in the clay-based geopolymer. Geopolymers cured under ambient conditions demonstrated no discernible change in the water interactions due to insufficient heat during curing to trigger the polycondensation. Time-domain NMR revealed that for the geopolymers heat-cured at 120 ​°C, the water component becomes more strongly bound with increasing curing time. The mechanically-activated system showed the strongest water bond compared to the calcined and untreated systems. FTIR results indicate that the intensity of the vibrational band arising from the structural water at 3620 ​cm-1 increases with increasing curing.

Physical characterization of high methoxyl pectin and sunflower oil wax emulsions: A low-field 1 H NMR relaxometry study.

Pectin-wax-based emulsion systems could be used to form edible films and coatings with desired water permeability characteristics. Pectin is often used in food industry due to its gelling and viscosity increasing properties. Physical properties of pectin are highly dependent on its esterification degree. Waxes are commonly used as edible coatings to enhance the water barrier properties of food products. This study focuses on preparing emulsions with sunflower oil wax (SFW) and high methoxyl pectin (HMP) at different concentrations for any possible edible film or coating formulations. Sunflower oil (SFO) was added as the dispersed oil phase to these emulsions. Characterization of the emulsions was performed by using particle size, rheology, and time domain nuclear magnetic resonance (NMR) relaxometry measurements. Effects of HMP concentration and the presence of SFO in the emulsion formulations were explored. Mean particle size values were recorded between 1 and 3µm. Rheology measurements showed that increasing HMP concentrations and presence of SFO in emulsions resulted in more pseudoplastic behavior. NMR transverse relaxation times (T2 ) were measured to detect the differences between the emulsions. Relaxation spectrum analysis was also conducted for a detailed understanding of the transverse relaxations. Addition of SFO and higher HMP concentrations decreased the T 2 values of the emulsion systems (P<0.05). However, T2 decreasing effect of SFO was compensated at 10% (w/w) HMP concentration showing that SFO was well dispersed in this particular emulsion formulation. Changes in the rheological behavior and relaxation times provided insight on the formation and stability of the emulsions. PRACTICAL APPLICATION: Findings of this study can be utilized and integrated to produce edible films and coatings with different water permeability characteristics. This study showed that NMR relaxometry parameters were also effective in monitoring and determining the physical characteristics of the pectin-wax-based emulsion systems as other conventional techniques including rheology and particle size measurements. Our NMR relaxometry findings were in correlation with the flow behavior and particle size results of the investigated emulsion systems.