Structure Mechanism Research Articles

Enhancement Mechanism of Asphalt Mixture Skeleton Structures Due to Morphological Characteristics of Steel Slag

Uncertainty still exists about the enhancement mechanism of the skeleton structure brought about by the steel slag, and the relationship between skeleton structure of steel slag asphalt mixture and the mechanical properties is still ambiguous. This study quantified the skeleton structure of steel slag asphalt mixture and explored the enhancement mechanism of skeleton structure brought about by the steel slag. The relationship between skeleton parameters and mechanical properties of steel slag asphalt mixture was also established. The results show that recycling steel slag as aggregate improves the skeleton quality of mix. The slag particles are not susceptible to be oriented tending to the horizontal direction. The abundant angularity of steel slag increased the contact number while the rough texture and non-spherical shape of steel slag enhanced the contact length. This project provided new insight and a notable opportunity to advance the comprehension of the skeleton structure of asphalt mixture containing steel slag.

Structure, Function, and Physicochemical Properties of Pore-forming Antimicrobial Peptides.

Antimicrobial peptides (AMPs), a class of antimicrobial agents, possess considerable potential to treat various microbial ailments. The broad range of activity and rare complete bacterial resistance to AMPs make them ideal candidates for commercial development. These peptides with widely varying compositions and sources share recurrent structural and functional features in mechanisms of action. Studying the mechanisms of AMP activity against bacteria may lead to the development of new antimicrobial agents that are more potent. Generally, AMPs are effective against bacteria by forming pores or disrupting membrane barriers. The important structural aspects of cytoplasmic membranes of pathogens and host cells will also be outlined to understand the selective antimicrobial actions. The antimicrobial activities of AMPs are related to multiple physicochemical properties, such as length, sequence, helicity, charge, hydrophobicity, amphipathicity, polar angle, and also self-association. These parameters are interrelated and need to be considered in combination. So, gathering the most relevant available information will help to design and choose the most effective AMPs.

Pleiotropic Regulation of PGC-1α in Tumor Initiation and Progression.

Mitochondria are recognized as a central metabolic hub with bioenergetic, biosynthetic, and signaling functions that tightly control key cellular processes. As a crucial component of mitochondrial biogenesis, peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α) is involved in regulating various metabolic pathways, including energy metabolism and ROS homeostasis. Recent studies have highlighted the significant role of PGC-1α in tumorigenesis, cancer progression, and treatment resistance. However, PGC-1α exhibits pleiotropic effects in different cancer types, necessitating a more comprehensive and thorough understanding. In this review, we discuss the structure and regulatory mechanisms of PGC-1α, analyze its cellular and metabolic functions, explore its impact on tumorigenesis, and propose potential strategies for targeting PGC-1α. The targeted adjustment of PGC-1α based on the metabolic preferences of different cancer types could offer a hopeful therapeutic approach for both preventing and treating tumors.

Exploring the inhibitory action of betulinic acid on key digestive enzymes linked to diabetes via in vitro and computational models: approaches to anti-diabetic mechanisms

ABSTRACT Phytochemicals are now increasingly exploited as remedial agents for the management of diabetes due to side effects attributable to commercial antidiabetic agents. This study investigated the structural and molecular mechanisms by which betulinic acid exhibits its antidiabetic effect via in vitro and computational techniques. In vitro antidiabetic potential was analysed via on α-amylase, α-glucosidase, pancreatic lipase and α-chymotrypsin inhibitory assays. Its structural and molecular inhibitory mechanisms were investigated using Density Functional Theory (DFT) analysis, molecular docking and molecular dynamics (MD) simulation. Betulinic acid significantly (p < 0.05) inhibited α-amylase, α-glucosidase, pancreatic lipase and α-chymotrypsin enzymes with IC50 of 70.02 μg/mL, 0.27 μg/mL, 1.70 μg/mL and 8.44 μg/mL, respectively. According to DFT studies, betulinic acid possesses similar reaction in gaseous phase and water due to close values observed for highest occupied molecular orbital (HOMO) and lowest occupied molecular orbital (LUMO) and the chemical descriptors. The dipole moment indicates that betulinic acid has high polarity. Molecular electrostatic potential surface revealed the electrophilic and nucleophilic attack-prone atoms of the molecule. Molecular dynamic studies revealed a stable complex between betulinic acid and α-amylase, α-glucosidase, pancreatic lipase and α-chymotrypsin. The study elucidated the potent antidiabetic properties of betulinic acid by revealing its conformational inhibitory mode of action on enzymes involved in the onset of diabetes.

Neurobehavioral perspectives on autistic spectrum disorder

Understanding genetics and environmental influences in autism has been explored in greater depth in recent decades. However, the mechanism by which they converge that leads to autism still needs to be explored further. An autism diagnosis in DSM-5 results from a neurodevelopmental disorder hurting normal brain function, affecting communication and social interaction combined with restricted or repetitive patterns of behavior and interests. This paper reviews current work investigating how the underlying mechanism of the brain structure and function relates to the complex and aberrant behavioral manifestations of autism. Mapping this connection can provide us with a better understanding of autism signs and symptoms, making the process of accurate diagnosis more straightforward. As a complex neurobehavioral condition, autistic individuals process the environment and their interactions with others differently from those without autism. So, they make different perceptions and connections between themselves and the environment. Consequently, they will have difficulty communicating, forming relationships, and responding appropriately to their environment. It is this lifelong neurobehavioral dysfunction that prevents autistic individuals from adequately understanding what they perceive and the emotional expression of others. There will be differences in their mental states, how their brains work, and how their thinking processes will be affected by a neurodevelopmental disability.

Kajian Psikoanalisis Sigmund Freud Berbasis Novel Karya Tulus Setiyadi untuk Menangani Kecemasan

Anxiety is one of the most common psychological problems experienced by everyone. The novel Kasrimpet Piweling and Puspita Rinengga by Tulus Setiyadi is one of the literary works that raises the issue of anxiety for its characters. Therefore, this research will discuss the anxiety of the main character in the novels Kasrimpet Piweling and Puspita Rinengga by Tulus Setiyadi using the psychoanalytic view proposed by Sigmund Freud. This research aims to explain the anxiety experienced by the main character in both novels. The theory used in this research is Sigmund Freud's psychoanalysis theory. Data collection with literature study method using library techniques, reading, recording and classification. Data analysis is done by looking at the personality structure, anxiety and ego defense mechanisms used by the characters. This type of research is literary research using descriptive method. The research data are in the form of words, phrases, clauses, sentences, narration from the narrator, characters' speech, and characters' actions related to ego defense mechanisms in Kasrimpet Piweling and Puspita Rinengga novels. The data collection techniques in this research are as follows: (1) conducting a literature study, (2) reading and understanding the novel, (3) marking the parts of the novel that indicate id, ego, and super ego (4) identifying the main characters and additional characters in the novel, (5) recording the data in the novel.

Polymeric Materials as a Promising Platform for Suppressing Protein Aggregation Process

Abstract: The idea of designing novel anti-amyloid therapeutic agents has generated a lot of scientific interest and the potential for treating a variety of human pathophysiologies, such as neurodegenerative and non-neuropathic diseases linked to amyloid protein aggregation. To address this, different small molecules, peptides, surfactants, nanomaterials, etc., have been thoroughly investigated to learn more about their antiamyloidogenic capabilities, offering a great deal of potential for them to show up as future anti-amyloidogenic agents. In contrast to existing smallmolecule analogues, polymers have been envisaged as promising anti-amyloid agents for treating these diseases because of their enthralling physicochemical features and simplicity of functionalisation. This review article emphasises the latest developments in the design of synthetic polymers such as amino acid-conjugated polymers, glycopolymers, zwitterionic polymers and so on reported in the last decade in modulating amyloid aggregation process. Additionally, the structural function and mechanism involved in modifying the aggregation process are highlighted in order to inspire the researchers even more and provide insight into this important field of study.

Structural mechanisms for binding and activation of a contact-quenched fluorophore by RhoBAST.

The fluorescent light-up aptamer RhoBAST, which binds and activates the fluorophore-quencher conjugate tetramethylrhodamine-dinitroaniline with high affinity, super high brightness, remarkable photostability, and fast exchange kinetics, exhibits excellent performance in super-resolution RNA imaging. Here we determine the co-crystal structure of RhoBAST in complex with tetramethylrhodamine-dinitroaniline to elucidate the molecular basis for ligand binding and fluorescence activation. The structure exhibits an asymmetric "A"-like architecture for RhoBAST with a semi-open binding pocket harboring the xanthene of tetramethylrhodamine at the tip, while the dinitroaniline quencher stacks over the phenyl of tetramethylrhodamine instead of being fully released. Molecular dynamics simulations show highly heterogeneous conformational ensembles with the contact-but-unstacked fluorophore-quencher conformation for both free and bound tetramethylrhodamine-dinitroaniline being predominant. The simulations also show that, upon RNA binding, the fraction of xanthene-dinitroaniline stacked conformation significantly decreases in free tetramethylrhodamine-dinitroaniline. This highlights the importance of releasing dinitroaniline from xanthene tetramethylrhodamine to unquench the RhoBAST-tetramethylrhodamine-dinitroaniline complex. Using SAXS and ITC, we characterized the magnesium dependency of the folding and binding mode of RhoBAST in solution and indicated its strong structural robustness. The structures and binding modes of relevant fluorescent light-up aptamers are compared, providing mechanistic insights for rational design and optimization of this important fluorescent light-up aptamer-ligand system.

Structural mechanism of bacteriophage lambda tail’s interaction with the bacterial receptor

Bacteriophage infection, a pivotal process in microbiology, initiates with the phage’s tail recognizing and binding to the bacterial cell surface, which then mediates the injection of viral DNA. Although comprehensive studies on the interaction between bacteriophage lambda and its outer membrane receptor, LamB, have provided rich information about the system’s biochemical properties, the precise molecular mechanism remains undetermined. This study revealed the high-resolution cryo-electron microscopy (cryo-EM) structures of the bacteriophage lambda tail complexed with its irreversible Shigella sonnei 3070 LamB receptor and the closed central tail fiber. These structures reveal the complex processes that trigger infection and demonstrate a substantial conformational change in the phage lambda tail tip upon LamB binding. Providing detailed structures of bacteriophage lambda infection initiation, this study contributes to the expanding knowledge of lambda-bacterial interaction, which holds significance in the fields of microbiology and therapeutic development.

In situ investigation on the evolution mechanism of heterogeneous micro-scale structure in potassium-niobate microwave flash sintering

Heterogeneity in the final product of flash sintering is a significant limitation for massive development. Synchrotron radiation computed tomography (SR-CT) was initially used to investigate the in-situ experiment of potassium-niobate (KNbO3) prepared by microwave flash sintering, revealing the temporal evolution of KNbO3 microstructure. The study has revealed the critical role of spatial arrangement between incompact particles and sintered agglomerates in achieving homogeneity in flash-sintered samples. Particles located the angle formed by the sintered agglomerate are more likely to experience electric field concentration, resulting in densification, and the densification rate decreases as the increases of angle size formed by the dense sintered agglomerates. This letter highlights that the presence of particles between sintered agglomerates is a significant factor contributing to heterogeneous sintering. The phenomenon is explained through a combination of experiments and simulation, which holds promise for enhancing the homogeneity of the sintering process.

Sound absorber based on a sonic black hole and multi-layer micro-perforated panels

In order to achieve low-frequency and broadband sound absorption simultaneously, we propose a structure that combines a sonic black hole with multilayer micro-perforated panels. Firstly, we present finite element models for composite structures based on sonic black holes and micro-perforated panels and describe the sound absorption mechanism of the composite structure by comparing the sound absorption phenomena of micro-perforated panels with sonic black holes and micro-perforated panels with ordinary circular tubes. Secondly, the effects of the end coordinates of the sonic black hole, the number of panels and the parameters of the micro-perforated panels are discussed. Thirdly, the theoretical model of the proposed structure is developed using the transfer matrix method. Finally, the sound absorption test of the proposed structure is carried out using impedance tubes. The test results show that the sound absorption coefficient of the sample with a geometric length of 203 mm reaches 0.8 at 223 Hz and stabilizes above 0.9 at 398–1600 Hz. The sound absorber based on a sonic black hole and multi-layer micro-perforated panels has excellent sound absorption performance and has great research potential and application value.

For the regeneration of spent graphite: The exploring of structural failure mechanism about commercial graphite

Along with the wide application of electric automobiles, the great “wave” of recycling for lithium-ion batteries would be upcoming due to their limited cycling lifespan. As the main components but without valuable elements, spent graphite suffers from effective recycling manners. Although the regeneration method has been deemed as a promising manner, the clarifying of their failure mechanism is prerequisite to the exploring of regeneration methods. Herein, commercial graphite with different healthy states is prepared through the disassembling of cells at different cycles. Assisted by the detailed structural analysis, the systematic failure process is clearly illustrated. At initial cycling, the shuttling of lithium ions renders the decomposing of unstable carbon atoms and some weak interlayer structures. With further cycling, the interlayer architecture and large-size grains were further damaged, to form small-size grains, accompanying enhanced anisotropy, finally resulting in the increasing internal resistance. Moreover, owing to the ion-diffusion behaviors, graphite sheets have an obvious moving, resulting in the transformation from 2H-phase to 3R-phase with the decreasing of energy-storage activity. Thus, from the perspective of internal structure, the decreasing of graphitized grains and the formation of 3R-phase served as crucial failure factors. Given this, the work is anticipated to illustrate the failure mechanism of graphite, meanwhile offering the basic regeneration direction of spent graphite samples.

Fe(III) dihydroxybenzoquinone-based metal organic framework for sodium battery cathodes: Properties, charge-discharge kinetics and redox reaction mechanisms

Sodium batteries are promising energy storage devices that could promote the transition to clean energy. For this purpose, it is desirable to develop safe cathode materials that can be easily produced from cheap and abundant elements. One of the attractive options is Fe2(dhbq)3, a metal-organic framework (MOF) that is synthesized from 2,5-dihydroxybenzoquinone (H2dhbq) and Fe(III) salts. This work provides a comprehensive analysis of Fe2(dhbq)3, including its structure, properties, charge-discharge kinetics, and redox reaction mechanism in sodium batteries. Using a set of experimental and theoretical methods, we show that sodiation of Fe2(dhbq)3 in the potential range of 1.1–3.8 V vs. Na+/Na is accompanied by a reversible two-electron reduction of dhbq ligands, while iron is only marginally involved and formally remains in +3 state. The material delivers a high specific capacity of up to ∼180 mAh g−1. Diffusion of Na+ ions in NaxFe2(dhbq)3 at low-to-moderate sodiation degrees (≥2.2 V vs. Na+/Na) is so fast that it is kinetically indistinguishable from supercapacitance. Additionally, we show that Fe2(dhbq)3 can be synthesized by simply mixing solutions of H2dhbq and salts of Fe(III) at room temperature, which makes its production especially simple and scalable.

Study on structure and viscosity evolution mechanism of titanium-containing iron liquid in full viscosity range

This study aims to investigate the relationship between the viscosity of Fe-4.5wt%C-0.2wt%Ti melt and its liquid structure. The actual experimental results of viscosity measurement reveal that the viscosity range of Fe-4.5wt%C-0.2wt%Ti melt can be segmented into three intervals. Through thermodynamically calculated equilibrium phases and high-temperature confocal experiments, it is observed that the abrupt change in viscosity in the lower temperature range is attributed to the precipitation of the graphite phase. Moreover, differential scanning calorimetry experiments exhibit a distinct phase transition in the liquid phase region. To delve into the atomic structure of the liquid phase region, molecular dynamics simulations are employed. The high-temperature liquid structure of Fe-4.5wt%C-0.2wt%Ti melt predominantly consists of vacancies, atomic clusters with Ti as the core, and atomic clusters with C as the core. Within the high-temperature liquid phase region, the conversion of Free-Fe and C1-Fe to Cx-Fe occurs, resulting in a reduction of free volume and enhanced stability of the cluster. Consequently, the inhomogeneity of the Fe-4.5wt%C-0.2wt%Ti melt increases, and the viscosity exhibits a significant increase with temperature, leading to a variation in the viscosity within the liquid phase interval.

Allosteric coupling asymmetry mediates paradoxical activation of BRAF by type II inhibitors.

The type II class of RAF inhibitors currently in clinical trials paradoxically activate BRAF at subsaturating concentrations. Activation is mediated by induction of BRAF dimers, but why activation rather than inhibition occurs remains unclear. Using biophysical methods tracking BRAF dimerization and conformation, we built an allosteric model of inhibitor-induced dimerization that resolves the allosteric contributions of inhibitor binding to the two active sites of the dimer, revealing key differences between type I and type II RAF inhibitors. For type II inhibitors the allosteric coupling between inhibitor binding and BRAF dimerization is distributed asymmetrically across the two dimer binding sites, with binding to the first site dominating the allostery. This asymmetry results in efficient and selective induction of dimers with one inhibited and one catalytically active subunit. Our allosteric models quantitatively account for paradoxical activation data measured for 11 RAF inhibitors. Unlike type II inhibitors, type I inhibitors lack allosteric asymmetry and do not activate BRAF homodimers. Finally, NMR data reveal that BRAF homodimers are dynamically asymmetric with only one of the subunits locked in the active αC-in state. This provides a structural mechanism for how binding of only a single αC-in inhibitor molecule can induce potent BRAF dimerization and activation.

Allosteric coupling asymmetry mediates paradoxical activation of BRAF by type II inhibitors

Allosteric coupling asymmetry mediates paradoxical activation of BRAF by type II inhibitors

Online Compositional Analysis of Complex Oligomers in Biomass Degradation by High-Pressure Flow-Through Reactor Coupled with High-Resolution Mass Spectrometry.

Online analysis of the composition and evolution of complex oligomeric intermediates in biomass degradation is highly desirable to elucidate the mechanism of bond cleavage and study the effect of conditions on the selective conversion of feedstocks. However, harsh reaction conditions and complicated conversion systems pose tremendous challenges for conventional, state-of-the-art analytical techniques. Herein, we introduce a continuous and rapid compositional analysis strategy coupling a high-pressure flow-through reactor with online high-resolution mass spectrometry, which enables the molecular-level characterization of most biomass-related products throughout the conversion for over 2 h. Catalytic depolymerization of one model compound was studied, and temperature-dependent data of over 50 intermediates as well as recondensation dimers and oligomers were obtained, which have rarely been reported in the literature. Thousands of products during the flow-through conversion of birch wood with molecular weights up to 1000 Da were presented, and 8 typical lignin dimers and oligomers with various interunit linkages were identified at the molecular level, demonstrating the potential to analyze more complicated systems far beyond conventional methods, especially for complex oligomers. The continuous evolutions of different components and typical products were unveiled for the first time, providing valuable insights into the investigation of the structure, composition, and decomposition mechanism of lignocellulose as well as the influence of reaction conditions. This method leads to the previously unattained ability to probe and reveal complicated chemical compositions in high-pressure reactions and can be applied to all other high-pressure heterogeneous aqueous reactions.

Essential amino acid residues and catalytic mechanism of trans-epoxysuccinate hydrolase for production of meso-tartaric acid.

This study aimed to discuss the essential amino acid residues and catalytic mechanism of trans-epoxysuccinate hydrolase from Pseudomonas koreensis for the production of meso-tartaric acid. The optimum conditions of the enzyme were 45°C and pH 9.0, respectively. It was strongly inhibited by Zn2+, Mn2+ and SDS. Michaelis-Menten enzyme kinetics analysis gave a Km value of 3.50mM and a kcat of 99.75s-1, with an exceptional EE value exceeding 99.9%. Multiple sequence alignment and homology modeling revealed that the enzyme belonged to MhpC superfamily and possessed a typical α/β hydrolase folding structure. Site-directed mutagenesis indicated H34, D104, R105, R108, D128, Y147, H149, W150, Y211, and H272 were important catalytic residues. The 18O-labeling study suggested the enzyme acted via two-step catalytic mechanism. The structure and catalytic mechanism of trans-epoxysuccinate hydrolase were first reported. Ten residues were critical for its catalysis and a two-step mechanism by an Asp-His-Asp catalytic triad was proposed.

Pre-Professional Placement Intervention Models in the Social Work programmed at the Technical University of Manabí in 2024

Introduction: Pre-professional placements are a fundamental component of Social Work students' education, as they enable them to apply theoretical knowledge in real-world contexts. However, at the Technical University of Manabí, no prior research has been conducted on the intervention models utilized. Objetive: The objective of the research was to determine the intervention models currently employed in the pre-professional placements of the Social Work programmed at UTM. The study aimed to characterize the models in terms of their objectives, structure, activities and evaluation mechanisms. Methods: The study adopted a quantitative approach with an exploratory-diagnostic design. The population consisted of 510 students in the seventh and eighth levels. The sample comprised 426 students, selected through non-probability sampling. A 17-item questionnaire on intervention models was designed. Results: The main results identified 10 applied models, with Case Management, Crisis Intervention and Behavior Modification being the most prevalent. Most include clear objectives, action plans and teacher supervision. Conclusion: The effectiveness of the intervention models applied in the pre-professional practices is corroborated, however, systematic evaluation needs to be improved, the models need to be adapted to local needs and the articulation between theory and professional practice needs to be strengthened for a comprehensive training.

Microstructure Evolution and Mechanical Properties of Ti–6Al–4Zr–4Nb Alloys Fabricated by Spark Plasma Sintering (SPS)

AbstractThe near-α Ti–6Al–4Zr–4Nb (wt pct) alloy is a recently developed alloy with potential for aerospace applications. This study evaluates the microstructure and mechanical properties of Ti–6Al–4Zr–4Nb produced by spark plasma sintering (SPS). The SPS samples sintered in the α + β regions exhibited equiaxed α with a neighboring thin β phase. Above the β-transus temperature, the α/β lamellar structure formed, allowing control of the grain size (100 ~ 200 μm). The compressive strength and the creep property of the SPS samples were compared with the LBPDed and the forged samples. The compressive strength of the SPS sample was lower than that of the LPBFed sample but similar to the forged sample. The SPS samples exhibited longer creep rupture life (2220 hours) than LPBFed samples (1730 hours), but shorter than the forged sample (4109 hours). The creep deformation mechanism of the lamellar structure in the SPS sample was dislocation creep.