Nuclear Magnetic Resonance Experiments Research Articles

Identification of potential C1-binding sites in the immunoglobulin CL domains.

Immunoglobulin G (IgG) molecules that bind antigens on the membrane of target cells spontaneously form hexameric rings, thus recruiting C1 to initiate the complement pathway. However, our previous report indicated that a mouse IgG mutant lacking the Cγ1 domain activates the pathway independently of antigen presence through its monomeric interaction with C1q via the CL domain, as well as Fc. In this study, we investigated the potential interaction between C1q and human CL isoforms. Quantitative single-molecule observations using high-speed atomic force microscopy revealed that human Cκ exhibited comparable C1q binding capabilities with its mouse counterpart, surpassing the Cλ types, which have a higher isoelectric point than the Cκ domains. Nuclear magnetic resonance and mutation experiments indicated that the human and mouse Cκ domains share a common primary binding site for C1q, centred on Glu194, a residue conserved in the Cκ domains but absent in the Cλ domains. Additionally, the Cγ1 domain, with its high isoelectric point, can cause electrostatic repulsion to the C1q head and impede the C1q-interaction adjustability of the Cκ domain in Fab. The removal of the Cγ1 domain is considered to eliminate these factors and thus promote Cκ interaction with C1q with the potential risk of uncontrolled activation of the complement pathway in vivo in the absence of antigen. However, this research underscores the presence of potential subsites in Fab for C1q binding, offering promising targets for antibody engineering to refine therapeutic antibody design.

Nuclear magnetic resonance experiments on the time-varying law of oil viscosity and wettability in high-multiple waterflooding sandstone cores

A simulated oil viscosity prediction model is established according to the relationship between simulated oil viscosity and geometric mean value of T2 spectrum, and the time-varying law of simulated oil viscosity in porous media is quantitatively characterized by nuclear magnetic resonance (NMR) experiments of high multiple waterflooding. A new NMR wettability index formula is derived based on NMR relaxation theory to quantitatively characterize the time-varying law of rock wettability during waterflooding combined with high-multiple waterflooding experiment in sandstone cores. The remaining oil viscosity in the core is positively correlated with the displacing water multiple. The remaining oil viscosity increases rapidly when the displacing water multiple is low, and increases slowly when the displacing water multiple is high. The variation of remaining oil viscosity is related to the reservoir heterogeneity. The stronger the reservoir homogeneity, the higher the content of heavy components in the remaining oil and the higher the viscosity. The reservoir wettability changes after water injection: the oil-wet reservoir changes into water-wet reservoir, while the water-wet reservoir becomes more hydrophilic; the degree of change enhances with the increase of displacing water multiple. There is a high correlation between the time-varying oil viscosity and the time-varying wettability, and the change of oil viscosity cannot be ignored. The NMR wettability index calculated by considering the change of oil viscosity is more consistent with the tested Amott (spontaneous imbibition) wettability index, which agrees more with the time-varying law of reservoir wettability.

Core Analysis Using Nuclear Magnetic Resonance

Core analysis is critical for oil and gas exploration and recovery. Nuclear magnetic resonance (NMR) has been widely applied to the petroleum industry for many years, and NMR core analysis plays an important role in supporting borehole NMR formation evaluation and understanding the mechanisms of petrophysics and petrochemistry. It’s unfortunate, however, that there has been a lack of commented descriptions of the basic procedures for NMR rock core analysis in the literature, which has led to issues of comparability and repeatability of NMR measurements between different laboratories. In this paper, we present a brief guideline for NMR rock core analysis of conventional T2, T1, T1-T2, and D-T2 measurements. As an established procedure in daily laboratory work, NMR core analysis includes three sophisticated steps: rock sample preparation, an NMR experiment, and data analysis. The acquisition and saturation of rock samples are described, and corresponding solutions are also considered. Detailed NMR experimental measurements, data setting, and calibration are addressed. Laplace inversion for different NMR experiments and models for estimation of porosity, irreducible water, permeability, pore structure, and oil saturation are included. The aim of this paper is to try to standardize general NMR experiments for rock core analysis.

Rapid simulation of two-dimensional spectra with correlated anisotropic dimensions.

A new algorithm has been developed to simulate two-dimensional (2D) spectra with correlated anisotropic frequencies faster and more accurately than previous methods. The technique uses finite-element numerical integration on the sphere and an interpolation scheme based on the Alderman-Solum-Grant algorithm. This method is particularly useful for numerical calculations of joint probability distribution functions involving quantities with a parametric orientation dependence. The technique's efficiency also allows for practical least-squares fitting of experimental 2D solid-state nuclear magnetic resonance (NMR) datasets. The simulation method is illustrated for select 2D NMR methods, and a least-squares analysis is demonstrated in the extraction of paramagnetic shift and quadrupolar coupling tensors and their relative orientation from the experimental shifting-d echo 2H NMR spectrum of a NiCl2 · 2D2O salt.

Microscopic occurrence and distribution of oil and water in situ shale: Evidence from nuclear magnetic resonance

Characterizing the microscopic occurrence and distribution of in-situ pore water and oil is crucial for resource estimation and development method selection of shale oil. In this paper, a series of nuclear magnetic resonance (NMR) experiments were conducted on shales from the Gulong Sag, Songliao Basin, China, at AR, WR-AR, WOR-AR, Dry, SO, and WR states. In-situ pore water and oil were reconstructed after WOR-AR. An improved T1–T2 pattern for shale oil reservoirs comprising water and oil was proposed to classify and quantitatively detect pore fluids at different occurrence states. The total and free oil contents derived from NMR T1–T2 spectra at AR states were found to correlate well with those from multistage Rock-Eval. Moreover, the NMR-calculated total and free oil are generally larger than those measured from multistage Rock-Eval, whereas adsorbed oil is the opposite, which implies that adsorbed, bound, and movable oils in shale pores can be accurately and quantitatively detected via NMR, without absorbed hydrocarbons in kerogen. As per the NMR T2 and T1–T2 spectra at WOR-AR state, the microdistributions of in-situ pore water and oil were clearly demonstrated. Adsorbed, bound, and movable oils primarily occur in the micropores (<100 nm), mesopores (100–1000 nm), and macropores (>1000 nm), respectively, whereas capillary-bound water is primarily correlated with micropores. Thus, the microscopic occurrence and distribution of adsorbed oil are remarkably affected by pore water, followed by bound oil, and movable oil is hardly affected. This study would be helpful in further understanding the microscopic occurrence characteristics of pore fluids in-situ shale oil reservoirs.

NMR diffusion in restricted environment approached by a fractional Langevin model

The diffusion motion of spin-bearing molecules is considerably affected in confined environments. In Nuclear Magnetic Resonance (NMR) experiments, under the presence of magnetic field gradients, this movement can be encoded in spin phase and the NMR signal attenuation due to diffusion can be evaluated. This paper considered this effect in both normal and anomalous diffusion by means of the Langevin stochastic model within the Gaussian phase approximation (GPA) for a constant gradient temporal profile. The phenomenological approach illustrates the emergence of fractional order exponential decay in the NMR signal and retrieves the classical result from Hanh echo.

High-throughput prediction of protein conformational distributions with subsampled AlphaFold2

This paper presents an innovative approach for predicting the relative populations of protein conformations using AlphaFold 2, an AI-powered method that has revolutionized biology by enabling the accurate prediction of protein structures. While AlphaFold 2 has shown exceptional accuracy and speed, it is designed to predict proteins’ ground state conformations and is limited in its ability to predict conformational landscapes. Here, we demonstrate how AlphaFold 2 can directly predict the relative populations of different protein conformations by subsampling multiple sequence alignments. We tested our method against nuclear magnetic resonance experiments on two proteins with drastically different amounts of available sequence data, Abl1 kinase and the granulocyte-macrophage colony-stimulating factor, and predicted changes in their relative state populations with more than 80% accuracy. Our subsampling approach worked best when used to qualitatively predict the effects of mutations or evolution on the conformational landscape and well-populated states of proteins. It thus offers a fast and cost-effective way to predict the relative populations of protein conformations at even single-point mutation resolution, making it a useful tool for pharmacology, analysis of experimental results, and predicting evolution.

Stereochemical and Computational NMR Survey of 1,2,3-Triazoles: in Search of the Original Tauto-Conformers.

The conformational analysis of nine functionalized 1,2,3-triazoles was carried out by the correlation of calculated and experimental high-level nuclear magnetic resonance (NMR) chemical shifts. In solution, the studied triazoles are in exchange dynamic equilibrium caused by their prototropic tautomerism of the NH-proton. The experimentally unresolved NMR signals were assigned for most of the compounds. A more thorough survey was conducted for 4-t-butyl-1,2,3-triazole-5-carbaldehyde oxime. The analysis performed within the framework of the DP4+ formalism completely confirmed the hypothesis of the predominance of the 2H-tautomer. Thus, the methodology for estimating stereochemical structures in the absence of some experimental data allowed the most stable conformations for dynamic systems with different tautomeric ratios to be reliably identified.

Permeability Prediction of Carbonate Reservoir Based on Nuclear Magnetic Resonance (NMR) Logging and Machine Learning

Reservoir permeability is an important parameter for reservoir characterization and the estimation of current and future production from hydrocarbon reservoirs. Logging data is an important means of evaluating the continuous permeability curve of the whole well section. Nuclear magnetic resonance logging measurement results are less affected by lithology and have obvious advantages in interpreting permeability. The Coates model, SDR model, and other complex mathematical equations used in NMR logging may achieve a precise approximation of the permeability values. However, the empirical parameters in those models often need to be determined according to the nuclear magnetic resonance experiment, which is time-consuming and expensive. Machine learning, as an efficient data mining method, has been increasingly applied to logging interpretation. XGBoost algorithm is applied to the permeability interpretation of carbonate reservoirs. Based on the actual logging interpretation data, with the proportion of different pore components and the logarithmic mean value of T2 in the NMR logging interpretation results as the input variables, a regression prediction model is established through XGBoost algorithm to predict the permeability curve, and the optimization of various parameters in XGBoost algorithm is discussed. The determination coefficient is utilized to check the overall fitting between measured permeability versus predicted ones. It is found that XGBoost algorithm achieved overall better performance than the traditional models.

Systematic QM/MM Study for Predicting 31P NMR Chemical Shifts of Adenosine Nucleotides in Solution and Stages of ATP Hydrolysis in a Protein Environment.

NMR (nuclear magnetic resonance) spectroscopy allows for important atomistic insights into the structure and dynamics of biological macromolecules; however, reliable assignments of experimental spectra are often difficult. Herein, quantum mechanical/molecular mechanical (QM/MM) calculations can provide crucial support. A major problem for the simulations is that experimental NMR signals are time-averaged over much longer time scales, and since computed chemical shifts are highly sensitive to local changes in the electronic and structural environment, sufficiently large averages over representative structural ensembles are essential. This entails high computational demands for reliable simulations. For NMR measurements in biological systems, a nucleus of major interest is 31P since it is both highly present (e.g., in nucleic acids) and easily observable. The focus of our present study is to develop a robust and computationally cost-efficient framework for simulating 31P NMR chemical shifts of nucleotides. We apply this scheme to study the different stages of the ATP hydrolysis reaction catalyzed by p97. Our methodology is based on MM molecular dynamics (MM-MD) sampling, followed by QM/MM structure optimizations and NMR calculations. Overall, our study is one of the most comprehensive QM-based 31P studies in a protein environment and the first to provide computed NMR chemical shifts for multiple nucleotide states in a protein environment. This study sheds light on a process that is challenging to probe experimentally and aims to bridge the gap between measured and calculated NMR spectroscopic properties.

Charge Regulation at the Nanoscale as Evidenced from Light-Responsive Nanoemulsions.

Emulsions are indispensable in everyday life, and the demand for emulsions' diversity and control of properties is therefore substantial. As emulsions possess a high internal surface area, an understanding of the oil/water (o/w) interfaces at the molecular level is fundamental but often impaired by experimental limitations to probe emulsion interfaces in situ. Here, we have used light-responsive surfactants (butyl-AAP) that can photoisomerize between E and Z isomers by visible and UV light irradiation to tune the emulsion interfaces. This causes massive changes in the interface tension at the extended o/w interfaces in macroemulsions and a drastic shift in the surfactants' critical micelle concentration, which we show can be used to control both the stability and phase separation. Strikingly different from macroemulsions are nanoemulsions (RH ∼90 nm) as these are not susceptible to E/Z photoisomerization of the surfactants in terms of changes in their droplet size or ζ-potential. However, in situ second-harmonic scattering and pulsed-field gradient nuclear magnetic resonance (NMR) experiments show dramatic and reversible changes in the surface excess of surfactants at the nanoscopic interfaces. The apparent differences in ζ-potentials and surface excess provide evidence for a fixed charge to particle size ratio and the need for counterion condensation to renormalize the particle charge to a critical charge, which is markedly different compared to the behavior of very large particles in macroemulsions. Thus, our findings may have broader implications as the electrostatic stabilization of nanoparticles requires much lower surfactant concentrations, allowing for a more sustainable use of surfactants.

Analytical Framework to Understand the Origins of Methyl Side-Chain Dynamics in Protein Assemblies.

Side-chain motions play an important role in understanding protein structure, dynamics, protein-protein, and protein-ligand interactions. However, our understanding of protein side-chain dynamics is currently limited by the lack of analytical tools. Here, we present a novel analytical framework employing experimental nuclear magnetic resonance (NMR) relaxation measurements at atomic resolution combined with molecular dynamics (MD) simulation to characterize with a high level of detail the methyl side-chain dynamics in insoluble protein assemblies, using amyloid fibrils formed by the prion HET-s. We use MD simulation to interpret experimental results, where rotameric hops, including methyl group rotation and χ1/χ2 rotations, cannot be completely described with a single correlation time but rather sample a broad distribution of correlation times, resulting from continuously changing local structure in the fibril. Backbone motion similarly samples a broad range of correlation times, from ∼100 ps to μs, although resulting from mostly different dynamic processes; nonetheless, we find that the backbone is not fully decoupled from the side-chain motion, where changes in side-chain dynamics influence backbone motion and vice versa. While the complexity of side-chain motion in protein assemblies makes it very challenging to obtain perfect agreement between experiment and simulation, our analytical framework improves the interpretation of experimental dynamics measurements for complex protein assemblies.

Investigation of the Reaction between a Homemade PEEK Oligomer and an Epoxy Prepolymer: Optimisation of Critical Parameters Using Physico-Chemical Methods.

Several researchers have examined the interest in using a thermoplastic to increase thermoset polymers' shock resistance. However, fewer studies have examined the nature of the mechanisms involved between both kinds of polymers. This was the objective of our work, which was carried out using a gradual approach. First, we describe the synthesis of a poly(ether ether ketone) oligomer (oPEEK) with hydroxyl terminations from the reaction of hydroquinone and 4,4'-difluorobenzophenone in N-methyl-2-pyrrolidone. Then, the main physicochemical properties of this oligomer were determined using different thermal analyses (i.e., differential scanning calorimetry (DSC), thermogravimetric (ATG), and thermomechanical analyses) to isolate its response alone. The chemical characterisation of this compound using conventional analytical chemistry techniques was more complex due to its insolubility. To this end, it was sulfonated, according to a well-known process, to make it soluble and enable nuclear magnetic resonance (NMR) and size exclusion chromatography (SEC) experiments. Additional information about the structural and chemical characteristics of the oligomer and its average molecular weight could thus be obtained. The synthesis of an oligoPEEK with α,ω-hydroxyl end-groups and a molecular weight of around 5070 g/mol was thus confirmed by NMR. This value was in accordance with that determined by SEC analysis. Next, the reaction of oPEEK with an epoxy prepolymer was demonstrated using DSC and dynamic rheometry. To this end, uncured mixtures of epoxy prepolymer (DGEBA) with different proportions of oPEEK (3, 5, 10 and 25%) were prepared and characterised by both techniques. Ultimately, the epoxy-oPEEK mixture was cured with isophorone diamine. Finally, topological analyses were performed by atomic force microscopy (AFM) in tapping mode to investigate the interface quality between the epoxy matrix and the oPEEK particles indirectly. No defects, such as decohesion areas, microvoids, or cracks, were observed between both systems.

Study on the Mechanical Degradation and Destruction Characteristics of Coal Oxidation

ABSTRACT Deep coal bodies are often in high stress and high temperature environments. To study the effects of stress and temperature on the mechanical degradation and failure characteristics of coal samples, nuclear magnetic resonance experiments were carried out before and after coal sample oxidation to analyze the effect of oxidation on the porosity of the coal samples. Through mechanical property experiments, the changes in the mechanical properties of the coal samples at different oxidation temperatures is analyzed. Then coal samples of different particle sizes are screened and statistically analyzed to determine the relationship between the fractal dimension of the broken block size and the oxidation temperature. A stress model for the oxidized coal samples is established to analyze its mechanical degradation and its breaking mechanism. Based on the results, As the oxidation temperature increases, The total porosity of the coal samples show an overall increasing trend, the elastic modulus, secant modulus, Poisson’s ratio, and shear modulus show a downward trend, and the destructive strain energy density decreases from 43.33 kg•m−3 to 15.47 kg•m−3, indicating the oxidized coal sample increases in plasticity and decreases in stiffness, resulting in a decrease in the amount of load the sample can carry. The fractal dimensions of the broken block size from raw coal to 200°C coal samples are 2.008, 2.092, 2.150, 2.159, 2.175, 2.183, 2.314, and 2.328. Oxidation leads to the formation a network of tiny fractures inside the coal samples; thus, the broken block size becomes more complex with worsened integrity. A model for the ability of the oxidized coal samples to resist destruction is established, and the diameters of unoxidized areas in oxidized coal samples are calculated to be 45.053, 44.956, 43.031, 41.931, 37.442, 28.081 and 13.778 mm. An analysis of the breaking mechanism of oxidized coal samples was carried out. Our results are beneficial for the safe operation of deep coal seam mining.

Experimental Study on the Mechanism and Law of Low-Salinity Water Flooding for Enhanced Oil Recovery in Tight Sandstone Reservoirs.

Currently, research surrounding low-salinity water flooding predominantly focuses on medium- to high-permeability sandstone reservoirs. Nevertheless, further investigation is necessary to implement this technique with regard to tight sandstone reservoirs. The present study comprises a series of experiments conducted on the crude oil and core of the Ordos Chang 6 reservoir to investigate the influence of ionic composition on low-salinity water flooding in tight oil reservoirs. The change in wettability on the rock surface was analyzed by using the contact angle experiment. The change in recovery rate was analyzed using a core displacement experiment. The reaction between rock fluids was analyzed using an ion chromatography experiment. Additionally, a nuclear magnetic resonance (NMR) experiment was used to analyze the mobilization law of crude oil and the change in wettability on the scale of the rock core. This led to a comprehensive discussion of the law and mechanism of enhancing the recovery rate via low-salinity water flooding from various perspectives. Experiments show that low-salinity water flooding is an effective technique for enhancing recovery in tight sandstone reservoirs. Altering the ionic composition of injected water can improve the water wettability of the rock surface and enhance recovery. Decreasing the mass concentration of Ca2+ or increasing the mass concentration of SO42- can prompt the ion-exchange reaction on the rock surface and detachment of polar components from the surface. Consequently, the wettability of the rock surface strengthens, augmenting the recovery process. Nuclear magnetic resonance experiments evidence that low-salinity water injection, with ion adjustment, significantly alters the interactions between the rock and fluid in tight sandstone reservoirs. As a result, the T2 signal amplitude decreases significantly, residual oil saturation reduces considerably, and the hydrophilic nature of the rock surface increases.

Discerning the stability behaviour of mavacamten availing liquid chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy: In silico toxicity and mutagenicity prediction of degradation products.

The present study aimed to separate, identify, and characterise the degradation products formed when mavacamten is exposed to stress degradation as well as the stability of the drug in various environments and also to understand its degradation chemistry. Prediction of in silico toxicity and mutagenicity was aimed at the observed degradation products. Stress degradation along with stability studies and degradation kinetics were performed on mavacamten, and separation of degradation products was carried out by high-performance liquid chromatography. Tandem mass spectrometry studies were executed to characterise the structures of degradation products using product ion fragments. Orthogonally, nuclear magnetic resonance experiments were conducted to elucidate the structures having ambiguity in characterising them. Deductive Estimation of Risk from Existing Knowledge and Structure Activity Relationship Analysis using Hypotheses software were used to establish in silico toxicity and mutagenic profiles of mavacamten and its degradation products. Two degradation products of mavacamten found in acidic hydrolytic stress conditions were separated, identified, characterised, and proposed as 1-isopropylpyrimidine-2,4,6(1H,3H,5H)-trione and 1-phenylethanamine. Mavacamten was found to be stable under different pH and gastrointestinal conditions. The degradation kinetics of mavacamten under 1 N acidic condition followed zero-order kinetics, and it was degraded completely within 6 h. In silico toxicity and mutagenicity studies revealed that 1-phenylethanamine can be a skin sensitiser. A high-performance liquid chromatography method was developed for the separation of degradation products of mavacamten and characterised by liquid chromatography-tandem mass spectrometry and nuclear magnetic resonance. During the manufacturing and storage of drug product, precautions need to be taken when dealing with acidic solutions as the drug is prone to hydrolysis in acidic conditions. The formation of 1-phenylethanamine under these conditions is to be monitored as it is a skin sensitiser.

Selective Detection of Intermediate-Amplitude Motion by Solid-State NMR.

The coexistence of rigid and mobile molecules or molecular segments abounds in biomolecular assemblies. Examples include the carbohydrate-rich cell walls of plants and intrinsically disordered proteins that contain rigid β-sheet cores. In solid-state nuclear magnetic resonance (NMR) spectroscopy, dipolar polarization transfer experiments are well suited for detecting rigid components, whereas scalar-coupling experiments are well suited for detecting highly mobile components. However, few NMR methods are available to detect the segments that undergo intermediate-amplitude fast motion. Here, we introduce two NMR experiments, a two-dimensional T2H-filtered CP-hCH correlation and a three-dimensional J-INADEQUATE CCH correlation, to observe this intermediate-amplitude motion. Both experiments involve 1H detection under fast magic-angle spinning (MAS). By combining 1H transverse relaxation (T2H) filters with dipolar polarization transfer, we suppress the signals of both highly rigid and highly mobile species, thus revealing the signals of intermediate mobile species. 1H detection under fast MAS is crucial for distinguishing the different motional amplitudes. We demonstrate these techniques on several plant cell wall samples and show that they allow the selective detection and resolution of certain hemicellulose and pectin signals, which are usually masked by the signals of the rigid cellulose and the highly dynamic pectins in purely dipolar and scalar NMR spectra.

Utilizing Differences in Mercury Injection Capillary Pressure and Nuclear Magnetic Resonance Pore Size Distributions for Enhanced Rock Quality Evaluation: A Winland-Style Approach with Physical Meaning

Pore structure is a fundamental parameter in determining the hydrocarbon storage capacity and flow characteristics of a reservoir. Mercury injection capillary pressure (MICP) and nuclear magnetic resonance (NMR) are two commonly utilized techniques for characterizing rock pore structures. However, current studies indicate that disparities in testing methodologies due to distinct physical characteristics lead to a partial misalignment in pore size distributions. We conducted MICP (dynamic) and NMR (static) experiments on eight tight sandstone and eight shale samples and proposed a method to utilize information from the differences in MICP and NMR pore size distributions, aiming to enhance the accuracy of rock quality analysis. We observed that in rock cores where large pores are interconnected with smaller pore throats, MICP tends to overestimate the proportion of these smaller pores and underestimate the larger ones. Furthermore, we integrated information from both dynamic and static experimental processes based on physical significance and found that the fitting accuracy of the newly proposed method is superior to the Winland r35 equation. Compared to the Winland r35 equation, our new method significantly improves fitting accuracy, increasing the R-squared value from 0.46 to 0.93 in sandstones and from 0.80 to 0.87 in shales. This represents a potential high-precision, comprehensive tool for rock quality analysis, offering a new perspective for an in-depth understanding of rock properties.

The impact of high temperature on mechanical properties and behaviors of sandstone

The impact of high temperature environments on the physical and mechanical properties of rocks is a significant factor to consider. The investigation into the impact of elevated temperatures on the physical and mechanical characteristics of rocks holds great importance in the advancement and exploitation of deep-seated mineral reserves, as well as in ensuring the safety and stability of subterranean engineering projects. This study utilizes the state-of-the-art GCTS Mechanical Loading Test System to conduct uniaxial and triaxial compression tests on sandstone after thermal treatment from 25°C to 650°C. In addition, XRD, SEM and nuclear magnetic resonance experiments were carried out on the sandstone after thermal treatment. The aim of the experiments is to provide a quantitative characterization of mechanical properties and behaviors of the rock samples. The results show that the mass, density, and wave velocity of sandstone decrease with increasing temperature, while volume and porosity increase. The mass, volume, and rate of density change of sandstone exhibit a significant increase when subjected to temperatures above 500°C. The uniaxial compressive strength and elastic modulus exhibit an initial increase followed by a subsequent decrease as the temperature rises, with 300°C serving as the critical turning point. The axial peak strain and Poisson’s ratio increase with increasing temperature. The cohesion decreases with increasing temperature, while the internal friction angle increases. Additionally, it is observed that the rate of change for both properties exhibits an increase beyond the temperature threshold of 400°C.

Inclusion complexes of β-cyclodextrin with isomeric ester aroma compounds: Preparation, characterization, mechanism study, and controlled release

Cyclodextrins (CDs) have been discovered to provide an efficient solution to the limited application of ester aroma molecules used in food, tobacco, and medication due to their strong smell and unstable storage. This work combined molecular modeling and experimental to analyze the conformation and controlled release of isomeric ester aroma compounds/β-CD inclusion complexes (ICs). The investigation revealed that ester aroma compounds could be effectively encapsulated within the β-CD cavity, forming ICs with low binding affinity. Furthermore, the key driving forces in ICs were identified as hydrogen bonds and van der Waals interactions through theoretical simulation. Results from the Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) and Isothermal titration calorimetry (ITC) experiments confirmed the intermolecular interaction predicted by the molecular model. Notably, the release rate of aroma compounds from L-menthyl acetate/β-CD (LMA/β-CD) IC exceeded that of terpinyl acetate/β-CD (TA/β-CD) IC. This difference is attributed to the length of the chain of aroma molecules and the variation in the position of functional groups, influencing the stable formation of ICs with β-CD. These findings hold potential implications for refining the application of ICs across diverse industries.