Changes In Molecular Structure Research Articles

Modification of emulsifying properties of mussel myofibrillar proteins by high-intensity ultrasonication treatment and the stability of O/W emulsion

The purpose of this research was to investigate the effects of high-intensity ultrasonication (HIUS) treatment at different ultrasonic powers (0, 150, 300, 450, 600 W) on the emulsifying properties of mussel myofibrillar protein (MMP). The changes in fourier infrared spectroscopy, fluorescence spectroscopy, free sulfhydryl groups and surface hydrophobicity, indicated that HIUS treatment changes the structure of MMP. HIUS treatment could significantly improve the emulsifying properties of MMP by affecting its physicochemical properties. HIUS treatment improved the emulsification activity index, emulsification stability index, adsorption protein percentage, creaming index, interfacial tension, rheology and other emulsifying properties of O/W emulsion. HIUS treatment at 600 W had the best effect on the solubility of MMP. Solubility, compared to control, increased from 11.1% to 33.4%; and the change in molecular structure of MMP was characterized by smaller particles (from 48.64 to 20.60 µm), lager absolute zeta potential (from 56.24 to 79.92 mV), and decreased turbidity (from 1.68 to 0.97). The emulsion stabilized by MMP ultrasonicated at 600 W showed the best storage stability, with the lowest particle size, the lowest surface tension (11.83 mN/m) and the largest absolute value of zeta potential (31.78 mV), which was confirmed in the microstructure photos. The results of this research provide theoretical basis for the application of ultrasonic modified MMP as functional protein ingredients to control emulsion-type seafood products or design of MMP-based emulsion delivery systems for functional material in the food industry.

Fluorescence fluctuation spectroscopy with a cooled SPAD array detector to unravel molecular processes in living cells

The molecular dynamics and protein interactions in living cells remain poorly understood despite their importance to several cellular processes. RNA molecules, for example, play a major role in many processes, from encoding and regulating gene expression to catalyzing biological reactions. Alterations of the metabolism of RNAs and RNA-binding proteins are involved in neurodegenerative diseases, such as ALS in neuronal cells. In particular, the connection between biomolecular dynamic processes and cellular function/organization is still unclear.Here, we propose a new class of Fluorescence Fluctuation Spectroscopy (FFS) techniques performed with a novel single-photon-avalanche-diode (SPAD) array detector to better decipher molecular dynamics, interactions and structural changes directly in living cells with microsecond time resolution.

A Nanostructured Phthalocyanine/Albumin Supramolecular Assembly for Fluorescence Turn-On Imaging and Photodynamic Immunotherapy.

Smart phototheranostic nanomaterials are of significant interest for high-quality imaging and targeted therapy in the precision medicine field. Herein, a nanoscale photosensitizer (NanoPcM) is constructed through the self-assembly of morpholine-substituted silicon phthalocyanine (PcM) and albumin. NanoPcM displays a turn-on fluorescence depending on the acid-induced abolition of the photoinduced electron transfer effect (change in molecular structure) and disassembly of the nanostructure (change in supramolecular structure), which enables low-background and tumor-targeted fluorescence imaging. In addition, its efficient type I photoreaction endows NanoPcM with a superior immunogenic photodynamic therapy (PDT) effect against solid tumors. The combination of NanoPcM-based PDT and αPD-1-based immunotherapy can efficiently inhibit tumor growth, reduce spontaneous lung metastasis, and trigger abscopal effects. This study should provide a perspective for the future design of nanomaterials as promising phototheranostics for cancer imaging and therapy.

Effects of warming on starch structure, rice flour pasting property, and cooked rice texture in a double rice cropping system

AbstractBackground and objectivesClimate warming has significant effects on rice quality. However, the effects of warming on starch structure, rice flour pasting properties, and cooked rice texture are unclear in double rice cropping systems. Therefore, a free‐air temperature increase experiment was conducted with two indica rice cultivars. The objectives of this study were to explore the changes in rice flour pasting properties and cooked rice texture under warming conditions and their relationships with starch structures.FindingsUnder warming conditions, rice starch had a lower amylose content (Peak 3) and proportion of long amylopectin branch chains (B3 chains) but a higher proportion of short amylopectin branch chains (A chains and B1 chains), amylopectin branching degree, relative crystallinity, ratio of 1045/1022 cm−1, and swelling power. Compared to the control treatment, warming significantly increased the peak viscosity, breakdown, and pasting temperature but decreased the setback of rice flour. Moreover, the hardness of cooked rice was significantly decreased, while its stickiness was significantly increased under warming conditions.ConclusionsThe changes in starch molecular structures resulted in lower hardness and setback but a higher stickiness, peak viscosity, breakdown, and pasting temperature of cooked rice or rice flour, which means better eating quality and worse cooking quality of double‐cropped indica rice under climate warming conditions.Significance and noveltyThese findings are expected to provide important information for improving rice cooking and eating quality and developing the rice industry under future climate warming conditions.

Aquaphotomics Research of Cold Stress in Soybean Cultivars with Different Stress Tolerance Ability: Early Detection of Cold Stress Response.

The development of non-destructive methods for early detection of cold stress of plants and the identification of cold-tolerant cultivars is highly needed in crop breeding programs. Current methods are either destructive, time-consuming or imprecise. In this study, soybean leaves’ spectra were acquired in the near infrared (NIR) range (588–1025 nm) from five cultivars genetically engineered to have different levels of cold stress tolerance. The spectra were acquired at the optimal growing temperature 27 °C and when the temperature was decreased to 22 °C. In this paper, we report the results of the aquaphotomics analysis performed with the objective of understanding the role of the water molecular system in the early cold stress response of all cultivars. The raw spectra and the results of Principal Component Analysis, Soft Independent Modeling of Class Analogies and aquagrams showed consistent evidence of huge differences in the NIR spectral profiles of all cultivars under normal and mild cold stress conditions. The SIMCA discrimination between the plants before and after stress was achieved with 100% accuracy. The interpretation of spectral patterns before and after cold stress revealed major changes in the water molecular structure of the soybean leaves, altered carbohydrate and oxidative metabolism. Specific water molecular structures in the leaves of soybean cultivars were found to be highly sensitive to the temperature, showing their crucial role in the cold stress response. The results also indicated the existence of differences in the cold stress response of different cultivars, which will be a topic of further research.

Computational modelling studies for high temperature monazite systems

Monazite is widely considered as a potential source of fissile feedstock for nuclear power generation, as it generally contains significant quantity of thorium (Th), uranium (U) and rare earth elements (REEs) within the mineral ore structure. Currently, a new process of high-temperature cracking of monazite is under development to improve the liberation of these cations from the robust monazite lattice. The current process for extraction of the REEs from the mineral involves complicated processes which makes use of harsh chemicals. These process therefore has significant scope for optimisation. With this in mind, the stability of monazite systems, t-CeSiO4 and m-LaSiO4 was investigated using first-principle calculation employing density functional theory (DFT) to gain a better understanding of the inherent molecular structures and the influence of temperature on conformation. The calculated lattice parameters for the model of t-CeSiO4 were found to be in good agreement with the experimental values (within 3%) and deemed a sufficient m-LaSiO4 of the system to be exposed to simulated reaction conditions. The elastic properties suggested that t-CeSiO4 is the more stable structure compared to m-LaSiO4 structure at 0 K. Semi-empirical embedded atom method interatomic potentials incorporated in the LAMMPS code were also employed to investigate the lattice expansion of t-CeSiO4 at high temperatures. It was found that calculated a and b lattice parameters expand with a linear ratio to a temperature of 2200 K whereas the c parameter was found to contract in the same temperature range. The findings provided an in depth understanding of the monazite molecular structure change at higher temperatures that may be helpful in plasma cracking optimisation experimental methodologies.

Effect of the Molecular Structure Change of a Matrix Polymer (Nylon 6) on the Deformation of Dispersed Phase (a Thermotropic Liquid Crystalline Polymer) Droplets in Shear Flow.

In this work, we investigated the effect of a change in the molecular structure and ensuing molar mass change of a matrix polymer (polyamide 6, Ny 6) on droplet deformation of a dispersed thermotropic liquid crystalline polymer (TLCP, a poly(ester amide)) in shear flow. This study focuses on a total capillary number (the sum of the shear capillary number and the elasticity capillary number) and the viscosity ratio between the TLCP and Ny 6, for the morphological development and mechanical performance of TLCP/Ny 6 blends. In contrast to Ny 6, which has a lower melt viscosity than the TLCP melt, a modified Ny 6 (m-Ny 6) with ca. 2 orders higher melt viscosity than that of Ny 6 at a shear rate of 1 s–1 was found to facilitate the deformation of the TLCP phase. A total capillary number was defined to characterize the viscoelasticity effect on droplet deformation in the blend system. The first normal stress difference obtained from the viscosity curve using Steller’s method was used for the evaluation of the elasticity capillary number. The total capillary number for the Ny 6 blend was far less than the critical capillary number and was insufficient for the dispersed TLCP droplets to be deformed. The shear capillary number of the m-Ny 6 blend was greater than the critical capillary number but was still insufficient for droplet deformation into fibril shapes. The total capillary number, including the elastic capillary number, was sufficiently greater than the critical capillary number for deformation of the dispersed TLCP droplets. Morphological observations and a comparison with the theoretical work confirmed the importance of the viscoelasticity of the melt in the immiscible Ny 6/TLCP blends for in situ composite fabrication in shear flow. Both the high viscosity and the first normal stress difference of m-Ny 6 promote the deformation and fibrillation of the dispersed TLCP droplets.

Effects of Superheated Steam Treatment on the Allergenicity and Structure of Chicken Egg Ovomucoid.

The aim of this study was to explore the effects of an emerging and efficient heating technology, superheated steam (SS), on the allergenicity and molecular structure of ovomucoid (OVM). OVM was treated with 120–200 °C of SS for 2 to 10 min. The allergenicity (IgG/IgE binding abilities and cell degranulation assay) and molecular structure (main functional groups and amino acids modification) changes were investigated. The IgG-binding ability of OVM decreased and the releases of β-hex and TNF-γ were inhibited after SS treatment, indicating that the protein allergenicity was reduced. Significant increases in oxidation degree, free SH content and surface hydrophobicity were observed in SS-treated OVM. The protein dimer and trimer appeared after SS treatment. Meanwhile, obvious changes occurred in the primary structure. Specifically, serine can be readily modified by obtaining functional groups from other modification sites during SS treatment. Moreover, the natural OVM structure which showed resistance to trypsin digestion was disrupted, leading to increased protein digestibility. In conclusion, SS-induced OVM aggregation, functional groups and amino acids modifications as well as protein structure alteration led to reduced allergenicity and increased digestibility.

Multistep Structural and Chemical Evaluation of Sugarcane Baggase, Pretreated With Alkali for Enhancing the Enzymatic Saccharification by Cellulase and Xylanase of the Pseudomonas sp. CVB-10 (MK443365) and Bacillus paramycoides T4 (MN370035) Mix-Culture System

The enzymatic saccharification of sugarcane bagasse was significantly increased by alkali pretreatment under mild conditions. The effectiveness of different concentrations of alkali and acid pretreatment of sugarcane bagasse for improving the enzymatic saccharification of lignocellulose has been evaluated. The sugarcane bagasse was characterized to contain 39.52% celluloses, 25.63% hemicelluloses, and 30.36% lignin. After that, sugarcane bagasse was pretreated with 5 and 10% of H2SO4 and NaOH at 121°C for 60 min. FTIR, XRD, and SEM analyses also showed significant molecular and surface structure changes of the sugarcane bagasse with 10% NaOH. Maximum saccharification was 489.5 mg/g from 10% NaOH pretreatment followed by 322.75, 301.25, and 276.6 mg/g from 10% H2SO4, 5% NaOH, and 5% H2SO4, respectively, which were 55.1, 32.0, 27.1, and 20.6 times higher than the that of the control. Cellulase and xylanase produced by Pseudomonas sp. CVB-10 (MK443365) and Bacillus paramycoides T4 (MN370035) were used to hydrolyze the pretreated bagasse, and the optimal condition was determined to be 30 h of the enzymatic reaction with the 3:1 ratio of enzymes under the temperature of 55°C, pH 5.0, and substrate concentration of 3%, leading to celluloses and hemicelluloses conversion in the enzymatic hydrolysis/saccharification that is more proficient.

Polarization modulation with optical lock-in detection reveals universal fluorescence anisotropy of subcellular structures in live cells

The orientation of fluorophores can reveal crucial information about the structure and dynamics of their associated subcellular organelles. Despite significant progress in super-resolution, fluorescence polarization microscopy remains limited to unique samples with relatively strong polarization modulation and not applicable to the weak polarization signals in samples due to the excessive background noise. Here we apply optical lock-in detection to amplify the weak polarization modulation with super-resolution. This novel technique, termed optical lock-in detection super-resolution dipole orientation mapping (OLID-SDOM), could achieve a maximum of 100 frames per second and rapid extraction of 2D orientation, and distinguish distance up to 50 nm, making it suitable for monitoring structural dynamics concerning orientation changes in vivo. OLID-SDOM was employed to explore the universal anisotropy of a large variety of GFP-tagged subcellular organelles, including mitochondria, lysosome, Golgi, endosome, etc. We found that OUF (Orientation Uniformity Factor) of OLID-SDOM can be specific for different subcellular organelles, indicating that the anisotropy was related to the function of the organelles, and OUF can potentially be an indicator to distinguish normal and abnormal cells (even cancer cells). Furthermore, dual-color super-resolution OLID-SDOM imaging of lysosomes and actins demonstrates its potential in studying dynamic molecular interactions. The subtle anisotropy changes of expanding and shrinking dendritic spines in live neurons were observed with real-time OLID-SDOM. Revealing previously unobservable fluorescence anisotropy in various samples and indicating their underlying dynamic molecular structural changes, OLID-SDOM expands the toolkit for live cell research.

Ultrafast electronic dynamics and vibrational dynamics of SWCNT under alkylation and annealing

Using ultrashort visible pulse laser, we have performed transient absorption spectroscopy to study the electronic relaxation and vibrational dynamics for three SWCNT samples of non-substituted SWCNT, alkylated SWCNT, and annealed alkylated SWCNT. Estimated lifetimes of ∼100 fs and ∼1 ps can be assigned to intraband and interband relaxation processes, respectively. Compared with the non-substituted sample, the intraband transition rate was found to be 7% smaller for the alkylated sample and nearly equal to the annealed alkylated sample within 2%. It implies that the intraband relaxation rate is not affected by alkylation itself but inhibited by excess chemical modification. Conversely, the interband relaxation rate shows no difference between the three samples. Short-time Fourier transform analysis of the measured traces of pump–probe delay dependent difference absorbance visualizes the change of molecular vibration frequency reflecting the energy transfer from (6,5)-SWCNT to (6,4)-SWCNT and the molecular structure change during the interband transition.

​Malt Pasting Properties and Starch Molecular Structural Changes During Mashing

​Malt Pasting Properties and Starch Molecular Structural Changes During Mashing

Upper Trapezius Muscle Tonicity, Assessed by Palpation, Relates to Change in Tissue Oxygenation and Structure as Measured byTime-Domain Near Infrared Spectroscopy.

Palpation is a diagnostic tool widely used by manual therapists despite its disputed reliability and validity. Previous studies have usually focused on the detection of myofascial trigger points (MTrPs), i.e., the points within muscles thought to have undergone molecular composition, oxygenation and structural changes, altering their tonicity. Time-domain near-infrared spectroscopy (TD-NIRS) could provide new insights into soft tissue oxygenation and structure, in order to objectively assess the validity and reliability of palpation. This pilot study aims at (1) assessing the ability of TD-NIRS to detect a difference between palpably normal and hypertonic upper trapezius (UT) muscles, and (2) to estimate the reproducibility of the TD-NIRS measurement on UT muscles. TD-NIRS measurements were performed on 4 points of the UT muscles in 18 healthy participants (10F, mean age: 27.6years), after a physical examination by a student osteopath to locate these points and identify the most and least hypertonic. From TD-NIRS, the most hypertonic points had a higher concentration in deoxy- ([HHb]) (0.887±0.253μM, p<0.001) and total haemoglobin ([HbT]) (1.447±0.772μM, p<0.001), a lower tissue oxygen saturation (StO2) (-0.575±0.286%, p<0.001), and a greater scattering amplitude factor (AF) (0.2238±0.1343 cm-1, p=0.001) than the least hypertonic points. Moreover, the intraclass correlation coefficient one-way random-effects model (ICC (1,1)) calculated for each TD-NIRS parameter and for each point revealed an excellent reliability of the measurement (Mean±SD, 0.9253±0.0678). These initial results, showing that changes in TD-NIRS parameters correlate with changes in muscle tonicity as assessed by palpation, are encouraging and show that TD-NIRS could help to further assess the validity of palpation as a diagnostic tool in manual therapy.

Studies in Solute-Solute and Solute-Solvent Interaction of Some Substituted Ketimine Drugs in 75 % Dichloromethane Water Mixture under Different Temperature by Viscometric Technique

The computation of densities, specific viscosities of 5- Bromo-2-hydroxy-4-chloro (p-methyl phenyl) ketimine (L1) and 5- Bromo-2-hydroxy-4-chloro (p-amino phenol) ketimine (L2) drugs in 75% (DCM + water) mixture at the temperature range (308 to 314 K) are reported. The investigational data shows, the effect of temperature on viscosity of solute in DCM + water mixtures which gives idea about the molecular interactions present in different solutions. Considerable molecular interactions have been observed between the substituted ketimines drugs and DCM + water mixture. The experimental data at different temperature range (308 to 314 K) are used to investigate thermodynamic properties such as free energy change (∆G), enthalpy change (∆H) and entropy change (∆S) of substituted ketimines drugs in 75% (DCM + water) mixture. The experimental data gives the idea about effect of temperature on the molecular interaction and structural changes in solute.

The productive preparation of synthetic rutile from titanium slag via an improved microwave heating and acid-alkali joint leaching approach

The paper presents the conversion process from titanium slag to rutile TiO2 through adopting the process route in the order of “Alkali leaching-Microwave roasting-Acid leaching-Microwave calcination”. The transformations of the slag samples in terms of phase composition, molecular structure, and other changes before and after the process were observed through analytical technics such as XRD, Raman, FI-IR and SEM. The characterization results all showed that the series of process treatment not only converted the phase of high-titanium slag from the black rock into rutile TiO2, but also significantly reduced impurities, with the improved rutile TiO2 grade meets the production standards of titanium dioxide using the chlorination process. The work highlights that the combined process of microwave heating and acid-alkali joint leaching is a potential and productive approach for preparing artificial rutile TiO2 from titanium slag.

Influence of waxy proteins on wheat resistant starch formation, molecular structure and physicochemical properties

This study investigated the influence of wheat waxy proteins on type III resistant starch (RS3) formation, molecular structure and physicochemical properties. Waxy deletions led to a significant increase in B- and C-type starch granules, particle size of RS3, and slowly digesting starch content, and a decrease in content of amylose and RS3. X-ray powder diffraction and Fourier-transform infrared spectroscopy analyses revealed high relative crystallinity and long-range (1047/1022 cm−1, IR1) and low short-range (1022/995, IR2) crystalline structures of RS3 in waxy wheat, which suggests that waxy deletions could produce a more ordered crystalline structure and fewer amorphous regions in RS3 crystals. Further laser confocal microscopy Raman spectroscopy analysis found that waxy deletions significantly increased the full width at half maximum and intensity of the bands at 480 cm−1, as well as leading to more ordered RS3 crystals. These changes in molecular structure resulted in improved physicochemical properties of RS3.

A review of mechanochromic polymers and composites: From material design strategy to advanced electronics application

The design and fabrication of functional polymers with fascinating mechanochromic properties are of profound significance to their prospective applications, such as wearable electronic skin, smart screen, artificial muscle, encryption, and anti-counterfeiting devices. Drawn inspiration from color-changing properties of biological skins, numerous approaches, from molecular synthesis to special biomimicry engineering, have been employed to construct flexible stimuli-responsive materials with superior mechano-stimulated optical change performance. In this review, we highlight and discuss recent important progress in material structure design strategy for mechanochromic polymers and composites. These optical variations primarily originate from the force-induced molecular structure change, disruption of intermolecular interaction, evolution of physical photonic and morphological structure. Moreover, according to their respective structure-property relationships, their multifunctional applications in advanced electronics field are also demonstrated with representative examples. Furthermore, a summary and perspective regarding the existing challenges in this field will be discussed, aiming to provide valuable insight into their future developments. We believe this feature review will bring helpful guidance to readers for choosing effective chromogenic material design method to satisfy different application requirements.

Study on the Microscopic Mechanism of Spontaneous Combustion and Oxidation Kinetics of Water-Leached Coal

In this article, a series of experiments have been carried out to study the spontaneous combustion and oxidation mechanism of coal after water immersion and investigate its tendency to spontaneous combustion, analyze the difficulty of spontaneous combustion of coal samples under different water immersion conditions, and establish a kinetic model of water immersion coal oxidation (taking the Bulianta 12# coal as a case study). They rely on physical oxidation adsorption, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetry, and oil bath heating. SEM has been used to analyze the characteristics of coal pore structure under different water immersion conditions (water-saturated coal samples under different water loss conditions until the coal samples are completely dried); FTIR served to investigate the characteristics of the molecular chemical structure of the coal surface before and after the coal is immersed in water. Through programmed temperature oxidation experiments combined with FTIR analyses and gas chromatographic (GC) analysis of gaseous products, it has been possible to study the changes of molecular structure and gas products on the surface of coal samples at different temperatures and water immersion conditions. The oxidation reaction rate of the 12# coal samples of Shendong Mine’s Bulianta Mine under different water content conditions during the spontaneous combustion process has been quantitatively studied. The difficulty of spontaneous combustion of coal samples has been correspondingly addressed. A kinetic model from the perspective of oxygen consumption has been proposed. Thermogravimetry-differential scanning calorimetry (TG-DSC) has been used to analyze and study the exothermal oxidation process before and after coal immersion. From the perspective of the exothermic intensity of the coal-oxygen reaction, an oxidation kinetic model for immersed coal samples has been developed to qualitatively determine its spontaneous combustion tendency. Results have shown that the increase in the specific surface area increases the risk of spontaneous combustion, and coal samples after soaking and drying have a stronger tendency to spontaneous combustion than raw coal. The moisture content of the coal sample leading to the easiest ignition conditions is 16.05%. Regardless of the moisture content, the critical temperature is maintained at 65–75°C, and the temperature of the left coal in the goaf should be prevented from exceeding this critical value.

Analysis of the aging mechanism and life evaluation of elastomers in simulated proton exchange membrane fuel cell environments

Abstract This paper studies the aging mechanism of elastomeric gaskets made from silicone rubbers in simulated proton exchange membrane fuel cells (PEMFCs) in humid, acidic, and high-temperature environments. The changes in the surface morphology are observed using optical microscopy. Attenuated total reflection Fourier transform infrared spectroscopy (AFT-FTIR) and X-ray photoelectron spectroscopy (XPS) are used to investigate the changes in the chemical molecular structure. The stress relaxation test is conducted to characterize the decay process of the mechanical properties. The results indicate that cracks appear on the surface and that the aging mechanism is mainly due to decomposition in the backbone and hydrolysis of the crosslinking. The stress relaxation modulus decreases as the acid concentration increases, which suggests a decrease in elasticity and an increase in brittleness. A master curve that relates time and concentration is constructed. Based on this inference, the experimental time can be shortened by about four times.

Microwave treatment alters the fine molecular structure of waxy hull-less barley starch

Waxy hull-less barley kernels and their isolated starches were exposed to different microwave conditions (power 640, 720, and 800 W, time 60, 120 and 180 s) and changes in morphology, particle size, digestibility, rheological properties, and molecular structure were measured and analyzed. Microwave treatment caused roughness and deformation of granular surfaces, and an increase in granule size. After treatment, the in vitro digestibility of starch was increased, i.e., the RDS increased, but the RS decreased. Microwave treatment decreased the K values of the in-kernel MWI WHBS. Dynamic rheological results showed that the in-kernel MWI WHBS pastes had lower TG′max, and higher G′max, G′90°C, G′25°C, G′0.1Hz and G′20Hz after treatment. The chain-length distribution did not significantly change after microwave treatment. However, the results for molecular size distributions showed that the peaks of amylopectin (Rh = ~100 nm) shifted left and right, indicating that the molecular volume might become smaller or larger under different processing conditions. The primary effects of microwave treatment may be loosening the molecular structure and cutting main chains of amylopectin.