Changes In Molecular Structure Research Articles

The Role of Gluten in Food Products and Dietary Restriction: Exploring the Potential for Restoring Immune Tolerance.

Wheat is extensively utilized in various processed foods due to unique proteins forming from the gluten network. The gluten network in food undergoes morphological and molecular structural changes during food processing, affecting the final quality and digestibility of the food. The present review introduces the formation of the gluten network and the role of gluten in the key steps of the production of several typical food products such as bread, pasta, and beer. Also, it summarizes the factors that affect the digestibility of gluten, considering that different processing conditions probably affect its structure and properties, contributing to an in-depth understanding of the digestion of gluten by the human body under various circumstances. Nevertheless, consumption of gluten protein may lead to the development of celiac disease (CD). The best way is theoretically proposed to prevent and treat CD by the inducement of oral tolerance, an immune non-response system formed by the interaction of oral food antigens with the intestinal immune system. This review proposes the restoration of oral tolerance in CD patients through adjunctive dietary therapy via gluten-encapsulated/modified dietary polyphenols. It will reduce the dietary restriction of gluten and help patients achieve a comprehensive dietary intake by better understanding the interactions between gluten and food-derived active products like polyphenols.

Molecular dynamics-based study of the modification mechanism of asphalt by graphene oxide.

Graphene oxide(GO) has been widely used in asphalt modification due to its excellent properties. To reveal the interaction effect between GO and asphalt materials, the microscopic behavior and molecular structure changes of asphalt and GO/asphalt were investigated by molecular dynamics (MD) simulations. Mean square displacement (MSD) results showed that GO significantly inhibited the diffusion of molecules of asphalt components. Radial distribution function (RDF) results that GO destroys the original sol-type structure of asphalt. Simultaneously, GO adsorbed resins at low-temperature, adsorbed asphaltenes at high-temperature, and dispersed as a dispersed phase in the light components. The concentration of the dispersed phase in the asphalt colloidal structure was increased and the mutual attraction was enhanced. This improves the deformation resistance at high temperature, but weakens the ductility at low temperatures. To investigate the mechanism of action of GO-modified asphalt, the asphalt model and the GO/asphalt composite system model were constructed using the Amorphous Cell module in Materials Studio 2020 software. Subsequently, molecular dynamics simulations of the GO/asphalt composite system were performed using the Forcite module, while the interactions between atoms and molecules were described using the COMPASS II force field.

INTEGRATED INVESTIGATION OF THE STRUCTURE OF INDUSTRIAL GREEN COKE

Integrated studies of green coke have been carried out by means of X-ray diffractometry, electron microscopy, electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR). It is determined by EPR spectroscopy that two types of radical structures are present in the samples: low-molecular aromatic radicals and conjugated polyaromatic structures in which the unpaired electron is delocalised. Analysis of line shapes in the EPR spectra reveals differences between the green coke samples under investigation. EPR is shown to be highly sensitive method allowing one to follow the changes of molecular structure during the production of green coke. The results obtained in the work with the help of EPR are in good agreement with the results of NMR spectroscopic studies. It is concluded that evaluation of the molecular structure of intermediate coking products is necessary to improve the composition of initial raw material and technological operations.

Influence of the phthalimide on the process of electrical aging of the high-pressure polyethylene

Relevance. The use of polyolefins without additional processing methods, namely, the increase in their electrophysical characteristics, is an actual modern requirement. For this, it is necessary to use the mechanism of ionization ageing where the role of the modifying additive must be elucidated by the method of infrared spectroscopy in high-pressure polyethylene. Purpose. The research aims to study the effect of low molecular weight organic additives of phthalimide on molecular structural changes in polymers that occur under external action. Methodology. The impact of electrical discharges on polymer dielectrics was carried out in a test cell of an asymmetric type. Tested polymer film before and after pre-stretching was tightly stretched onto this plate following the research procedure. To create an air gap of constant thickness between the top electrode and the polymer film, 1.5 mm thick glass spacers were placed along the edges. Results. The electrical strength (lifetime) of high-pressure polyethene (LDPE) and its optimal modification before and after electrical ageing was investigated. Following experimental data, at the content of 0.05 wt. % LDPE its electrical strength reaches a maximum value compared to both the original LDPE and LDPE at other additive contents. The introduction of 0.05 wt.% phthalimide into high-pressure polyethene contributes to a noticeable decrease in the intensity of the formation of C=0 groups, which is the measure of the oxidative degradation of polymer chains. Conclusions. The optimal composition of the phthalimide was determined and their electrophysical properties were studied. It was found that composites with additions of 0.05 wt.% phthalimide significantly improve the electrophysical properties of LDPE.

In-situ photocatalytic degradation of low-density polyethylene: A pathway towards eco-sustainability and circular economy

The present study demonstrates the accelerated rate of photo-degradation in low-density polyethylene (LDPE) films using nanomaterials like titanium dioxide (TiO2) in a photochemical reactor, an efficient, environmentally benign, and sustainable chemical. The effect of various parameters such as source of light, catalyst loading, pH, and temperature was investigated to achieve maximum degradation on a laboratory scale. The surface morphology with molecular and chemical structure changes in the nanocomposite films was monitored before and after degradation using various analytical techniques. It is found that the degradation reaction rate is greatly affected by pH and temperature and follows the first-order photo-thermal kinetics reactions. The calculated activation energies for the different properties range from 77.6 kJ/mol for carbonyl group formation to 55 kJ/mol for vinyl group formation at an optimum pH of 4 and temperature of 30 °C, respectively. The optimized sample's storage modulus (Esm) increased from 17.76 to 210 MPa, demonstrating the loss of tensile strength after irradiation and increased elasticity. Thus, it clearly demonstrated that the LDPE sample loaded with 12% catalyst and exposed to 288 h at pH 4 and 30 °C temperature degraded most efficiently with 6.25% weight loss. In addition, there is a high correlation between the area of degradation and carbonyl index with R2 > 0.96, which helps in validating the fact that during the degradation process, there is volatilization of degradation products that leads to the formation of 0.523 mm (in length) of holes (microscopic analysis). This study brings new insights into reducing plastic pollution by minimizing waste prevention and generation at the source by promoting the usage of intermediates (formed during degradation) as a secondary material for producing new plastic products.

The Boltzmann distributions of molecular structures predict likely changes through random mutations

New folded molecular structures can only evolve after arising through mutations. This aspect is modeled using genotype-phenotype maps, which connect sequence changes through mutations to changes in molecular structures. Previous work has shown that the likelihood of appearing through mutations can differ by orders of magnitude from structure to structure and that this can affect the outcomes of evolutionary processes. Thus, we focus on the phenotypic mutation probabilities φqp, i.e., the likelihood that a random mutation changes structure p into structure q. For both RNA secondary structures and the HP protein model, we show that a simple biophysical principle can explain and predict how this likelihood depends on the new structure q: φqp is high if sequences that fold into p as the minimum-free-energy structure are likely to have q as an alternative structure with high Boltzmann frequency. This generalizes the existing concept of plastogenetic congruence from individual sequences to the entire neutral spaces of structures. Our result helps us understand why some structural changes are more likely than others, may be useful for estimating these likelihoods via sampling and makes a connection to alternative structures with high Boltzmann frequency, which could be relevant in evolutionary processes.

Changes in physicochemical properties, molecular structure and microstructure during vacuum assisted quick pickling of low-NaCl salted eggs

In order to clarify the quality formation process of low-NaCl salted eggs (LSEs) under the dual action of vacuum and salt, changes of physicochemical properties, molecular structure, and microstructures of egg white as well as interior and exterior yolks were systematically studied. Results showed that the salt content of egg whites and egg yolks increased to around 5% and 1% respectively, which were only about half of their traditional counterparts. Exterior yolk exudes more oil than the interior yolk, which was consistent with the observation of a more compact microstructure by scanning electron microscopy (SEM). Rheological testing demonstrated a significant increase in the viscosity of yolks but a decrease of egg whites. At the molecular level, proteins of egg white and yolk had gone through the process of denaturation and aggregation, but their change tendencies of free sulfhydryl group, surface hydrophobicity and secondary structure were slightly different. In summary, vacuum assisted two-stage pickling could effectively shorten the ripening time of salted eggs and reduce salt content without compromising their good quality.

Physicochemical characterization and environmental stability of a curcumin-loaded Pickering nanoemulsion using a pea protein isolate-dextran conjugate via the Maillard reaction

This study investigated pea protein isolate (PPI) and dextran (DX) conjugates produced via the Maillard reaction as Pickering stabilizers for various food applications. The results found that as heating time increased (0–5 h), the grafting degree heightened. The PPI-DX conjugate exhibited a rough porous surface in contrast to native PPI, accompanied by changes in molecular weight and secondary structure. Additionally, the aggregation of low-solubility PPI was partially inhibited due to the contribution of increased solubility and reduced surface hydrophobicity by glycation. Curcumin-loaded Pickering nanoemulsions stabilized with PPI-DX had smaller droplets and higher curcumin encapsulation (greater than80 %) than PPI-stabilized nanoemulsions. PPI-DX adsorbed on the interface showed improved physical stability compared to PPI alone, even after various pH conditions and three heat treatments. The nanoemulsion stabilized with PPI-DX demonstrated improved apparent viscosity and dispersion stability. These findings highlight the effectiveness of PPI-DX conjugates as stabilizers for developing stable and functional Pickering nanoemulsions.

Natural and laboratory-induced maturation of kerogen from the Vaca Muerta Formation: A comparison study

Artificial maturation of kerogen is a widely used technique to assess the hydrocarbon potential of shale rocks and to observe thermal transformations of organic matter in the laboratory. However, the degree of reproducibility of natural geological transformation at the molecular level is still not fully established. In the present work, a set of kerogens isolated from Vaca Muerta Formation core samples at varying levels of thermal maturity were studied. Another set of samples was obtained by anhydrous pyrolysis of kerogen in a closed system. Molecular structures measured by solid-state techniques (13C NMR, XPS and FTIR) were compared in natural and artificially matured samples at equivalent levels of thermal maturation. We observed that heating in an anhydrous closed system accurately reproduces most of the molecular structural changes observed during natural thermal maturation, with exceptions related to the branching degree and oxygen containing groups. The evolution of some parameters, such as N and S content, are highly variable in the natural samples because of differences in their deposition environments. In these cases, artificial thermal maturation changes are smaller and follow more clearly defined trends because variables other than thermal changes are not present. This is the first work comparing natural and artificial thermal maturation in the Vaca Muerta Formation and add valuable data regarding the limitation of artificial maturation that can be extrapolated to other formations.

Changes in the three-dimensional molecular structure of coal during methane adsorption induced swelling

Methane (CH4) adsorption-induced swelling is one of the critical factors controlling the permeability of coalbed methane (CBM). CH4 adsorption alters the molecular structure of coal so as to induce coal swelling, and many uncertainties still exist in the process. In this study, the change in the molecular structures of different chemical structures by CH4 adsorption was investigated using the Grand Canonical Monte Carlo method to simulate the alteration of bond lengths and bond angles during swelling. The results demonstrate that the alteration of chemical structure is more extensive than a chemical bond, which is the critical factor causing the swelling behavior. Owing to the complex molecular structure of coal, among the different types of chemical structures, the C-O-C (-O-) chemical structure showed the most significant change in bond angle, with the largest degree of change is 12.89%. Compared with other chemical structures, the C-C-C (aromatic -C-) chemical structures are more stable and the largest degree of change is 0.65%. For the different types of chemical bonds, the C-C chemical bonds showed the most significant change in bond lengths, with the largest degree of change is 2.94%. And the O-H chemical bond showed the smallest change, with the largest degree of change is 0.79%. Considering the structure evolution of coal, the C-O-C (-O-) chemical structure decreases with increasing maturity and changes to the greatest after the adsorption of methane. The aromatic structure increases and the degree of deformation decreases, which is consistent with the previous experimental values for swelling. These results reveal the details of different types of chemical group deformation, providing a molecular-level insight into adsorption swelling and permeability changes.

The Impact of Polymorphism on Charge Transport Properties for Pyrene-FxTCNQ Cocrystals

Research on the charge transport properties of organic semiconductor materials is crucial for the development of organic sensors. In this paper, we investigated the charge transport properties of pyrene-TCNQ, pyrene-F2TCNQ, and pyrene-F4TCNQ cocrystals using the quantum nuclear tunneling model and Monte Carlo simulations to calculate charge mobility. At room temperature, we observed hole mobility values is 0.658 cm2V-1s-1 and electron mobility values is 1.492 cm2V-1s-1, respectively, for pyrene-TCNQ. As the number of F atoms in TCNQ increases, we observed an increase in both hole and electron mobility. Our results showed that the electron to hole mobility ratio was approximately 2.2 for pyrene-TCNQ, 0.6 for pyrene-F2TCNQ, and 0.5 for pyrene-F4TCNQ. Our findings suggest that the introduction of F atoms causes changes in the TCNQ molecular structure, cocrystal stacking mode, adjacent molecular distance, and intermolecular polarization. These changes lead to a modification of the reorganization energy and transfer integrals, ultimately affecting charge transport. Additionally, our results showed that transport along the π-π direction in the three cocrystals exhibited strong anisotropic characteristics, which were much larger than those observed in the other two directions.

New Insights into Acylhydrazones E/Z Isomerization: An Experimental and Theoretical Approach.

A family of acylhydrazones have been prepared and characterized with the aim of investigating their potential as information storage systems. Their well-established synthetic methodologies allowed for the preparation of seven chemically stable acylhydrazones in excellent yields that have been photophysically and photochemically characterized. In addition, DFT and TD-DFT calculations have been performed to gain more insights into the structural, energetic and photophysical properties of the E/Z isomers. Our results reveal that E/Z configurational isomerization upon irradiation is highly dependent on the stabilization of the E or Z isomers due to the formation of intramolecular H bonds and the electronic/steric effects intrinsically related to their structures. In addition, Raman spectroscopy is also used to confirm the molecular structural changes after the formation of hydrogen bonds in the isomers.

Influence of Gamma-irradiation on the Structural, Morphological, and Optical Properties of β-H2Pc Nanocrystalline Films: Implications for Optoelectronic Applications

Abstract In this study, the effects of gamma radiation with doses ranging from 0 KGy to 100 KGy on the structural and optical properties of the Beta Metal-free Phthalocyanine (β-H2Pc) powder and films were investigated. X-ray diffraction and scanning electron microscope were used to examine the crystalline and morphological structures of the thin films. While Fourier transform infrared and absorption spectra were utilized to study the changes in molecular structure and energy absorption, respectively. The results showed that while γ-irradiation induced changes in the surface morphology and optical properties of β-H2Pc, the molecular structure remained stable except for the disappearance of the hydroxyl (OH) functional group peak. The irradiation dose was found to affect the dielectric constants, dispersion characteristics, and nonlinear optical susceptibility of the material. The β-H2Pc thin films exhibited high absorption coefficients and refractive index values, making them promising candidates for optoelectronic devices such as solar cells. However, careful consideration of the effects of gamma irradiation on other properties of β-H2Pc such as stability, toxicity, and cost-effectiveness is necessary. Graphical Abstract

Chemical Property Evaluation and Tensile Strength Correlation of XLPE Insulators Based on Accelerated Thermal Aging

Cross-linked polyethylene (XLPE) cable is a representative power transmission cable. XLPE has excellent mechanical properties, chemical and heat resistance, and insulation. However, XLPE insulation deteriorates during operation due to electrical, mechanical, and thermal stresses. Among these, thermal stress is a major factor and reduces insulation properties due to a change in molecular structure. Therefore, XLPE characteristic evaluation by heat exposure is essential for power cable condition evaluation. Herein, deteriorated XLPE samples were characterized by tensile strength, X-ray diffraction, Fourier-transform infrared spectroscopy, differential scanning calorimetry, and ultraviolet-visible spectroscopy after exposure to various temperatures and durations. Comparing the tensile strength with other analysis results yielded correlations. Each characteristic showed a linear relationship. The correlation between tensile strength and carbonyl index was the strongest, and the coefficient of determination, R2, was 0.9299. Therefore, these results will provide important information on chemical properties when establishing operational management standards for XLPE insulators in the future.

Microcosmic mechanism of metal–organic framework enhanced thermoplastic polyurethane exposed to laser-induced shock wave

Incorporating nano-particles into polymer matrix has enabled improving shock wave mitigation (SWM) ability. Vast majority of researchers adopted inorganic nano-materials to enhance polymer matrix. Due to the incompatibility between inorganic nano-particles and polymers, complicated interface modification processes were often used. Metal–organic frameworks (MOFs) have good compatibility with polymers and show excellent SWM capabilities. However, they are brittle and experience lattice collapse after shock loading. Based on this, thermoplastic polyurethane (TPU) enhanced by zeolitic imidazolate framework-8 (ZIF-8) was proposed and prepared. The mixtures can not only improve the SWM ability of polymers, but also address the brittleness of MOFs. Additionally, scholars often use simulation methods to study energy dissipation mechanism of materials, rarely evidences of microstructural changes observed to support theoretical speculations. In this work, by analyzing surface morphology and molecular structural changes, energy dissipative mechanism was investigated. With addition amount of 5 wt% and 10 wt% ZIF-8 particles in TPU, the pressure can be reduced by 0.074 GPa and 0.1478 GPa than neat TPU. TPUM-10 had a stronger deformation resistance and SWM ability. Moreover, main chemical structures were remained unchanged after shock. The increased ability of SWM may relate to hydrogen bond forming process and delayed material failure.

Effect of Mass and Temperature Rate on the Thermal Properties of High-Density Polyethylene Using Differential Scanning Calorimetry

Mass and heating rates alter the thermal properties, molecular structure, and phase changes of the materials. This study aimed to investigate the influence of sample mass (10-30 mg) and heating rate (4-15 °C/min) on the thermal characteristics of high-density polyethylene (HDPE) using differential scanning calorimetry (DSC). The experiments were conducted in two cycles. In the first cycle, samples of different masses (10-30 mg) were heated to 180 °C followed by cooling at a constant heating rate of 10 °C/min with a mass flow rate of 20 ml/min of purging gas (nitrogen). In the second cycle, a sample mass of 15 mg was used to investigate the thermal characteristics while varying the temperature rates (4, 6, 8, 10, and 15 °C/min). It was concluded that the variation in sample mass significantly affected the thermal properties of HDPE, leading to a slight increase in the melting temperature and latent heat, which shifted towards higher temperatures. In contrast, the temperature rate caused a reduction in the latent heat and crystallization temperatures. The thermograms obtained from the experiments provided insight into the thermal behavior of HDPE under different conditions, and the findings emphasized the importance of carefully considering the effects of mass and temperature rate when measuring the thermal properties of HDPE.

Optimization of food-grade colloidal delivery systems for thermal processing applications: a review.

Colloidal delivery systems are widely used in the food industry to enhance the dispersibility, stability, efficacy, or bioavailability. However, when exposed to the high temperature, delivery systems are often prone to degradation, which limits its application in thermal processing. In this paper, the effects of thermal processing on the performance of traditional protein-based or starch-based delivery systems are firstly described, including the molecular structure changes of proteins, starches or lipids, and the degradation of embedded substances. These effects are unfavorable to the application of the delivery system in thermal processing. Then, strategies of improving the heat resistance of food grade colloid delivery system and their use in frying, baking and cooking food are mainly introduced. The heat resistance of the delivery system can be improved by a variety of strategies, including the development of new heat-resistant materials, the addition of heat-resistant coatings to the surface of delivery systems, the cross-linking of proteins or starches using cross-linking agents, the design of particle structures, the use of physical means such as ultrasound, or the optimization of the ingredient formula. These strategies will help to expand the application of heat-resistant delivery systems so that they can be used in real thermal processing.

Physicochemical properties of ultrasound-pretreated pea starch and its inclusion complexes with lauric acid

Ultrasound is a promising green technology for modifying starch. The influence of ultrasound pretreatment (UPT) at diverse temperatures on the morphology and molecular structure of pea starch and its ability to form inclusion complexes with lipids were investigated. After UPT at each temperature, the starch granules retained an unchanged crystalline structure but exhibited notable changes in short-range molecular order and molecular structure. In comparison with the samples treated at 0 and 20 °C, pea starch subjected to UPT at 40 °C had a significantly (P ≤ 0.05) higher complexing index with lauric acid (LA) and the starch-LA inclusion complex exhibited a higher enthalpy change, relative crystallinity, and resistant starch content. These differences were attributed to the higher temperature causing changes in the disruption points of starch chains and an enlargement in the molecular weight of linear chains. These results may promote the utilization of ultrasound for effective starch modification.

Mechanical properties of viscoelastic materials subjected to thermal‐oxidative aging: An experimental and theoretical study

AbstractViscoelastic materials (VEMs) made from rubber polymer will inevitably age due to the interactions with the harmful environment during service life, thus reducing the reliability of viscoelastic (VE) damping equipment installed in building structures. In order to understand and be able to predict the degradation of VE damping equipment, it is imperative to comprehensively study the influence of aging on the mechanical properties of VEMs. In this paper, a series of thermal‐oxidative (TO) aging tests and mechanical property tests are conducted on our previously developed VEMs to study effects of TO aging on the molecular chain structure and corresponding changes of macroscopic mechanical properties of VEMs. By classifying molecular chains of VEMS into elastic chains and free chains, the effects of different chemical reactions during TO aging on these two main chains and corresponding changes on macroscopic mechanical behaviors of VEMs are analyzed. This facilitates formulating a mathematical model that can characterize the mechanical behavior of TO aging VEMs. In conjunction with the experimental data, the accuracy and applicability of the proposed model are compared and verified. Sensitivity analyses of parameters involved in the proposed model are then performed. The experimental results demonstrate that the TO aging can degrade the deformation capability and harden the modulus of VEMs, which may adversely affect the performance of VE damping devices. The parameter analyses depict that the TO aging affects the macroscopic mechanical behavior of VEMs by altering the relative number and configuration of free chains and elastic chains as well as their respective contributions to the total stress of VEMs. The results point to the high accuracy of the proposed model in representing the strain–stress behavior of VEMs under different aging conditions.

A Study on the O2 Plasma Etching Method of Spray-Formed SWCNT Films and Their Utilization as Electrodes for Electrochemical Sensors.

In this study, we analyzed the morphological changes and molecular structure changes on the surface of single-walled carbon nanotube (SWCNT) films during oxygen plasma (O2) etching of SWCNT surfaces formed by the spray method and analyzed their potential use as electrochemical electrodes. For this purpose, a SWCNT film was formed on the surface of a glass substrate using a self-made spray device using SWCNT powder prepared with DCB as a solvent, and SEM, AFM, and XPS analyses were performed as the SWCNT film was O2 plasma etched. SEM images and AFM measurements showed that the SWCNT film started etching after about 30 s under 50 W of O2 plasma irradiation and was completely etched after about 300 s. XPS analysis showed that as the O2 plasma etching of the SWCNT film progressed, the sp2 bonds representing the basic components of graphite decreased, the sp3 bonds representing defects increased, and the C-O, C=O, and COO peaks increased simultaneously. This result indicates that the SWCNT film was etched by the O2 plasma along with the oxygen species. In addition, electrochemical methods were used to verify the damage potential of the remaining SWCNTs after O2 plasma etching, including cyclic voltammetry, Randles plots, and EIS measurements. This resulted in a reversible response based on perfect diffusion control in the cyclic voltammetry, and an ideal linear curve in the Randles plot of the peak current versus square root scan rate curve. EIS measurements also confirmed that the charge transfer resistance of the remaining SWCNTs after O2 plasma etching is almost the same as before etching. These results indicate that the remaining SWCNTs after O2 plasma etching do not lose their unique electrochemical properties and can be utilized as electrodes for biosensors and electrochemical sensors. Our experimental results also indicate that the ionic conductivity enhancement by O2 plasma can be achieved additionally.