Rearrangement Of Network Research Articles

Catalyst-Free Cardanol-Based Epoxy Vitrimers for Self-Healing, Shape Memory, and Recyclable Materials.

Bio-based vitrimers present a promising solution to the issues associated with non-renewable and non-recyclable attributes of traditional thermosetting resins, showcasing extensive potential for diverse applications. However, their broader adoption has been hindered by the requirement for catalyst inclusion during the synthesis process. In this study, a cardanol-based curing agent with poly-hydroxy and tertiary amine structures was prepared by a clean synthetic method under the theory of click chemistry. The reaction of a cardanol-based curing agent with diglycidyl ether of bisphenol A formed catalyst-free, self-healing, and recyclable bio-based vitrimers. The poly-hydroxy and tertiary amine structures in the vitrimers promoted the curing of epoxy-carboxylic acid in the cross-linked network and served as internal catalysts of dynamic transesterification. In the absence of catalysts, the vitrimers network can achieve topological network rearrangement through dynamic transesterification, exhibiting excellent reprocessing performance. Moreover, the vitrimers exhibited faster stress relaxation (1500 s at 180 °C), lower activation energy (92.29 kJ·mol-1) and the tensile strength of the recycled material reached almost 100% of the original sample. This work offers a new method for preparing cardanol-based epoxy vitrimers that be used to make coatings, hydrogels, biomaterials, adhesives, and commodity plastics in the future.

Stress amplification and relaxation imaging around cracks in nanocomposite gels using ultrasound elastography.

The quantification and modeling of gel fracture under large strain and dissipative conditions is still an open issue. In this study, a novel method for investigating the mechanical behavior of gels under highly deformed states, specifically in the vicinity of the crack tip, was developed to gain insights into fracture processes. Shear wave elastography, originally developed for the biomedical community, is employed as a powerful tool to quantitatively map the local elasticity of model gels. Here, the local stress is experimentally measured from the shear wave velocity according to nonlinear acoustoelasticity theory. The stress concentration observed at the crack tip in elastic gels is validated using classical finite element methods. Subsequently, the mechanisms of network rearrangements in viscoelastic gels (with silica nanoparticles) are analyzed both spatially and temporally. These gels consist of 90 wt% water and are synthesized with sticky nanoparticles to introduce exchangeable sacrificial bonds that facilitate stress relaxation. The nanoparticles efficiently provide stress relaxation around the crack tip, mitigating a stress singularity. The amplitude of stress relaxation was measured quantitatively and appears to be higher closer to the crack. This paper showcases the feasibility and potential of a new experimental approach that enables non-invasive and dynamic mapping of gel fracture mechanics.

Thermoswitchable catalysis to inhibit and promote plastic flow in vitrimers.

Acid-base catalysis is a common strategy to induce covalent bond exchanges in dynamic polymer networks. Strong acids or strong bases can promote rapid network rearrangements, and are simultaneously preferred catalysts for chemical reactions where maximum efficiency at the lowest possible temperature is aimed for. However, within the context of dynamic polymer networks, the incorporation of highly active catalysts can negatively affect the longer term application potential. Network dynamicity can diminish through catalyst ageing or quenching and highly active catalysts may prematurely activate bond exchanges, leading to dimensional instability and thus low creep resistance of the polymer networks. Herein, we present several examples where we explicitly explored weak acids (carboxylic acids) as catalysts for dynamic bond exchanges, using vinylogous urethanes (VU) as a well-understood protic acid catalysed vitrimer chemistry. Surprisingly, we have found that the sought-after long-term stability offered by a weak acid does not necessarily bring lower activity at high temperature. In fact, the weak acids show a remarkable thermoswitchable catalytic behaviour, going from an inactive hydrogen bonded state to an active state where the polymer matrix is protonated, with a profound impact on the network reactivity and rheology. Carboxylic acids with different electronic or steric environments show clear reactivity trends and their fine-tuning resulted in the most thermally responsive VU vitrimers studied to date. Our findings point out that catalyst choice and design for vitrimers is only poorly informed by catalyst performance in more traditional chemical reactions (in solvent), and that a more tailored catalyst design holds great promise for the field of vitrimers.

The Effect of a Low Degree of Fluorine Substitution on Cotton Fiber Properties

AbstractCellulose modification often employs chemical processes to tailor its properties and functionalities to fit the demands of a wide range of applications, maximizing its potential as a versatile and sustainable material. From both synthetic and environmental standpoints, one of the ultimate goals is to achieve significant modifications to enhance the end properties of the cellulose while minimizing the number of modified building blocks. The current study demonstrates that a synthetic glucose derivative, 6‐deoxy‐6‐fluoro‐glucose (6F‐Glc), fed into the fertilized cotton ovules, resulted in the accumulation of fluorine inside the cotton fibers with no apparent alteration to their morphology or development. These fibers exhibited a degree of substitution of 0.006, which is 170 times lower than that reported for chemical methods for cellulose modification. However, the physical characterization of the modified fibers showed a surprisingly large impact of this low‐level modification on the cellulose structure (e.g., hydrogen bonding network rearrangement) and a modest increase in the mechanical properties of the fibers. The obtained results exemplify the use of biological systems to introduce low quantities of new functionalities while maximizing the impact on fiber properties.

Abstract LB_B17: Single-cell analysis of dynamic remodeling of radiated TNBC cells

Abstract The dynamic rearrangement of the cellular cytoskeletal network and changes in cellular stiffness play crucial roles in the progression of malignant tumors, including those with invasive and metastatic traits. Despite the acknowledged connections, the inherent complexity of cancer and the various microenvironments that individual cells experience during treatment have hindered comprehensive investigations into therapeutic responses, particularly at the individual cell level. Notably, the emergence of large DNA damage-induced cells following radiotherapy in the challenging-to-treat triple-negative breast cancer (TNBC) subtype suggests potential concurrent alterations in cellular mechanics. This study dives into the complex interplay among radiation therapy, cytoskeletal architecture, and cellular stiffness at the level of individual cells. By utilizing atomic force microscopy (AFM) as a quantitative and non-invasive technique, we discerned how cancer cells respond to radiation treatment based on their cytoskeletal properties. Our findings revealed a clear correlation between radiation therapy and disruptions in cytoskeletal integrity, along with a simultaneous increase in cellular stiffness. These observed changes could potentially indicate impending cell death or a reduced tendency for metastasis. Building on these insights, we propose that assessing cytoskeletal features through AFM holds potential for tailoring personalized radiation therapy approaches, depending on the distinct responses exhibited by cancer cells post-treatment. This shift in approach, guided by mechanics, underscores the capacity to enhance treatment effectiveness while minimizing unintended damage. By shedding light on the intricate interplay between radiation-induced cellular responses and mechanical properties, this study lays the foundation for innovative strategies that leverage cytoskeletal attributes to customize and optimize therapeutic interventions for TNBC and potentially other malignancies. Citation Format: Minhee Ku, Jin Sung Kim, Woong Sub Koom, Jaemoon Yang. Single-cell analysis of dynamic remodeling of radiated TNBC cells [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr LB_B17.

Accretion Cycles, Structural Evolution, and Thrust Activity in Accretionary Wedges With Various Décollement Configurations: Insights From Sandbox Analog Modeling

AbstractThe architecture (geometry, fault network, and stacking pattern of accreted thrust sheets) of accretionary wedges influences subduction zone processes. However, it remains challenging to constrain the architectural evolution in natural accretionary wedges over geological timescales. In this study, we undertook sandbox analog modeling, with quantitative analysis of the wedge geometry and digital image correlation‐based kinematics, to delineate the wedge growth history with four décollement settings (single or double and continuous or discontinuous). The results show that the wedge is formed by repeated episodic frontal accretion with a constant cycle (i.e., the accretion cycle), and the degree of coupling between the base of the wedge and subducting plate interface appears to depend on the relative strengths of the wedge and detachment. An interbedded décollement layer in the incoming sediment facilitated wedge segmentation and rearrangement of the internal fault network, which weakened the wedge strength. A combination of a detachable high‐friction patch in the basal décollement and a continuous interbedded weak layer enabled underplating of underthrusted sediment beneath the inner wedge, which involved a low‐angle, long‐lived forethrust and multiple cycles of frontal accretion on short‐lived forethrusts at the deformation front. Our findings suggest that décollement configuration is a key factor in controlling the accretion cycle, strain distribution, fault network, and wedge strength on timescales of ∼105 yr in natural accretionary systems. This result should be considered when investigating modern subduction zones.

Differential interactome mapping of aggregation prone/prion-like proteins under stress: novel links to stress granule biology

BackgroundAberrant stress granules (SGs) are emerging as prime suspects in the nucleation of toxic protein aggregates. Understanding the molecular networks linked with aggregation-prone proteins (prion protein, synuclein, and tau) under stressful environments is crucial to understand pathophysiological cascades associated with these proteins.MethodsWe characterized and validated oxidative stress-induced molecular network changes of endogenous aggregation-prone proteins (prion protein, synuclein, and tau) by employing immunoprecipitation coupled with mass spectrometry analysis under basal and oxidative stress conditions. We used two different cell models (SH-SY5Y: human neuroblastoma and HeLa cell line) to induce oxidative stress using a well-known inducer (sodium arsenite) of oxidative stress.ResultsOverall, we identified 597 proteins as potential interaction partners. Our comparative interactome mapping provides comprehensive network reorganizations of three aggregation-prone hallmark proteins, establish novel interacting partners and their dysregulation, and validates that prion protein and synuclein localize in cytoplasmic SGs. Localization of prion protein and synuclein in TIA1-positive SGs provides an important link between SG pathobiology and aggregation-prone proteins. In addition, dysregulation (downregulation) of prion protein and exportin-5 protein, and translocation of exportin-5 into the nucleus under oxidative stress shed light on nucleocytoplasmic transport defects during the stress response.ConclusionsThe current study contributes to our understanding of stress-mediated network rearrangements and posttranslational modifications of prion/prion-like proteins. Localization of prion protein and synuclein in the cytoplasmic SGs provides an important link between stress granule pathobiology and aggregation-prone proteins. In addition, our findings demonstrate nucleocytoplasmic transport defects after oxidative stress via dysregulation and nuclear accumulation of exportin-5.

Critical analysis of the thermal stability of transesterification vitrimers for 3D‐printing applications based on digital light processing

Abstract3D‐printable vitrimers processed by digital light processing (DLP) have been recently developed, based on the transesterification reaction of β‐hydroxyester structures from mono‐ and diacrylate monomers employed in the formulation. These materials show promising repairability and recyclability, in addition to other interesting features such as shape memory and shape reconfigurability. It has been reported that structural changes taking place due to transesterification promote network rearrangement and an enhancement of the thermomechanical properties. However, the elevated temperatures required for the network reconfiguration cast some doubts on their applicability in real‐life scenarios. In this paper, we analyze the effect of the thermal treatment on the thermomechanical properties and relaxation behavior of these materials and discuss the underlying mechanism explaining the observed changes. We identify some critical issues related to use of a monoacrylate containing β‐hydroxyester moieties, and propose solutions to overcome the most relevant drawbacks. © 2023 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.

Tree-ring structured phase change materials with high through-plane thermal conductivity and flexibility for advanced thermal management

Phase change materials (PCMs) as one of the most promising latent heat storage materials have been applied for thermal management of electronic devices. Nonetheless, simultaneously endowing PCMs with high through-plane thermal conductivity and flexibility remains challenging. Herein, a coupling strategy combining scraping, hot compression, and roll-cutting is proposed to fabricate polydimethylsiloxane/paraffin/boron nitride (PDMS/PW/BN) composites. The BN alignment across the in-plane (x-y direction) was firstly obtained via scraping, then hot compression and roll-cutting were introduced to induce BN aligned across the through-plane (z-direction). Consequently, PW was wrapped by the cross-linked PDMS/BN network, thus forming a similar tree-ring structure to natural wood. The tree-ring structure effectively avoided the liquid leakage of PW, thus showing a high dimension retention ratio of 98 %. The vertical orientation of the BN network imparted the PCMs improved through-plane thermal conductivity of the PCMs to 2.16 W·m−1·K−1 at a BN loading of 13.0 wt%, showing a remarkable improvement of 943 % in comparison with PDMS/PW. Interestingly, the PCMs exhibited tunable thermal conductivity by triggering the melting-crystallization transition of PW. The in-situ X-ray diffraction indicated that the BN network rearrangement occurred during the phase transition. Furthermore, the good thermal management capability of PCMs was practically confirmed on working chips and via finite element simulation. This work presents a cost-effective approach for producing flexible PCMs with high through-plane thermal conductivity, which have the potential to be used in the thermal management of advanced electronics.

Neighboring Molecular Engineering in Diels-Alder Chemistry Enabling Easily Recyclable Carbon Fiber Reinforced Composites.

Although a variety of dynamic covalent bonds have been successfully used in the development of diverse sustainable thermosetting polymers and their composites, solving the trade-off between recovery efficiency and comprehensive properties is still a major challenge. Herein, a "one-stone-two-birds" strategy of lower rotational energy barrier (Er) phosphate-derived Diels-Alder (DA) cycloadditions was proposed for easily recyclable carbon fiber (CF)-reinforced epoxy resins (EPs) composites. In such a strategy, the phosphate spacer with lower Er accelerated the segmental mobility and dynamic DA exchange reaction for network rearrangement to achieve high-efficiency repairing, reprocessing of the EPs matrix and its composites and rapid nondestructive recycling of CF; meanwhile, incorporating phosphorus-based units especially reduced their fire hazards. The resulting materials simultaneously showed excellent thermal/mechanical properties, superb fire safety and facile recyclability, realizing the concept of recycling for high-performance thermosetting polymers and composites. This strategy is of great significance for understanding and enriching the molecular connotation of DA chemistry, making it potentially applicable to the design and development of a wide range of dynamic covalent adaptable materials toward practical cutting-edge-tech applications.

Neighboring Molecular Engineering in Diels–Alder Chemistry Enabling Easily Recyclable Carbon Fiber Reinforced Composites

AbstractAlthough a variety of dynamic covalent bonds have been successfully used in the development of diverse sustainable thermosetting polymers and their composites, solving the trade‐off between recovery efficiency and comprehensive properties is still a major challenge. Herein, a “one‐stone‐two‐birds” strategy of lower rotational energy barrier (Er) phosphate‐derived Diels–Alder (DA) cycloadditions was proposed for easily recyclable carbon fiber (CF)‐reinforced epoxy resins (EPs) composites. In such a strategy, the phosphate spacer with lower Er accelerated the segmental mobility and dynamic DA exchange reaction for network rearrangement to achieve high‐efficiency repairing, reprocessing of the EPs matrix and its composites and rapid nondestructive recycling of CF; meanwhile, incorporating phosphorus‐based units especially reduced their fire hazards. The resulting materials simultaneously showed excellent thermal/mechanical properties, superb fire safety and facile recyclability, realizing the concept of recycling for high‐performance thermosetting polymers and composites. This strategy is of great significance for understanding and enriching the molecular connotation of DA chemistry, making it potentially applicable to the design and development of a wide range of dynamic covalent adaptable materials toward practical cutting‐edge‐tech applications.

Microscopic Evidence for the Topological Transition in Model Vitrimers.

In addition to the glass transition, vitrimers undergo a topological transition from viscoelastic liquid to viscoelastic solid behavior when the network rearrangements facilitated by dynamic bond exchange reactions freeze. The microscopic observation of this transition is elusive. Model polyisoprene vitrimers based on imine dynamic covalent bonds were synthesized by reaction of α,ω-dialdehyde-functionalized polyisoprenes and a tris(2-aminoethyl)amine. In these dynamic networks nanophase separation of polymer and reactive groups leads to the emergence of a relevant length scale characteristic for the network structure. We exploited the scattering sensitivity to structural features at different length scales to determine how dynamical and topological arrests affect correlations at segmental and network levels. Chains expand obeying the same expansion coefficient throughout the entire viscoelastic region, i.e., both in the elastomeric regime and in the liquid regime. The onset of liquid-like behavior is only apparent at the mesoscale, where the scattering reveals the reorganization of the network triggered by bond exchange events. The such determined "microscopic" topological transition temperature is compared with the outcome of "conventional" methods, namely viscosimetry and differential scanning calorimetry. We show that using proper thermal (aging-like) protocols, this transition is also nicely revealed by the latter.

Pathological Correlates of Cognitive Decline in Parkinson's Disease: From Molecules to Neural Networks.

Parkinson's disease (PD) is a progressive neurodegenerative disorder caused by the death of dopaminergic neurons in the substantia nigra and appearance of protein aggregates (Lewy bodies) consisting predominantly of α-synuclein in neurons. PD is currently recognized as a multisystem disorder characterized by severe motor impairments and various non-motor symptoms. Cognitive decline is one of the most common and worrisome non-motor symptoms. Moderate cognitive impairments (CI) are diagnosed already at the early stages of PD, usually transform into dementia. The main types of CI in PD include executive dysfunction, attention and memory decline, visuospatial impairments, and verbal deficits. According to the published data, the following mechanisms play an essential role demonstrates a crucial importance in the decline of the motor and cognitive functions in PD: (1) changes in the conformational structure of transsynaptic proteins and protein aggregation in presynapses; (2) synaptic transmission impairment; (3) neuroinflammation (pathological activation of the neuroglia); (4) mitochondrial dysfunction and oxidative stress; (5) metabolic disorders (hypometabolism of glucose, dysfunction of glycolipid metabolism; and (6) functional rearrangement of neuronal networks. These changes can lead to the death of dopaminergic cells in the substantia nigra and affect the functioning of other neurotransmitter systems, thus disturbing neuronal networks involved in the transmission of information related to the regulation of motor activity and cognitive functions. Identification of factors causing detrimental changes in PD and methods for their elimination will help in the development of new approaches to the therapy of PD. The goal of this review was to analyze pathological processes that take place in the brain and underlie the onset of cognitive disorders in PD, as well as to describe the impairments of cognitive functions in this disease.

Hidden Beneath the Layers: Extending the Core/Shell Model of Reverse Micelles.

Reverse micelles (RMs) provide a unique and highly tunable model system to study water in confined environments. The complex properties of water within RMs arise from the disruption of extended hydrogen bond (H-bond) networks that mediate local and long-range dynamics in bulk aqueous systems. Modulating the water pool size influences its H-bond dynamics, with smaller RMs increasingly restricting the H-bond network rearrangements leading to slower dynamics; however, within small confined systems, the dynamics of the surfactants also influence the water dynamics. Using ultrafast two-dimensional infrared spectroscopy, we investigate the effects of RM size on the surfactant headgroup rotamer populations and picosecond interfacial H-bond dynamics of aerosol-OT surfactants. We find that the increased water penetration accelerates H-bond dynamics, with larger RMs showing faster dynamics. These results imply that the changes in the RM structure alter the physical structure of the RM interface and thus alter the solvation dynamics. The findings in this study can be used for developing models for structure-specific solvation dynamics that account for the surfactant packing and hydration at the interface.

A human in vitro neuronal model for studying homeostatic plasticity at the network level

Mechanisms that underlie homeostatic plasticity have been extensively investigated at single-cell levels in animal models, but are less well understood at the network level. Here, we used microelectrode arrays to characterize neuronal networks following induction of homeostatic plasticity in human induced pluripotent stem cell (hiPSC)-derived glutamatergic neurons co-cultured with rat astrocytes. Chronic suppression of neuronal activity through tetrodotoxin (TTX) elicited a time-dependent network re-arrangement. Increased expression of AMPA receptors and the elongation of axon initial segments were associated with increased network excitability following TTX treatment. Transcriptomic profiling of TTX-treated neurons revealed up-regulated genes related to extracellular matrix organization, while down-regulated genes related to cell communication; also astrocytic gene expression was found altered. Overall, our study shows that hiPSC-derived neuronal networks provide a reliable invitro platform to measure and characterize homeostatic plasticity at network and single-cell levels; this platform can be extended to investigate altered homeostatic plasticity in brain disorders.

Suffusion behavior of crushed calcareous sand under reversed cyclic hydraulic conditions

Due to the unique properties of calcareous sand in reclamation projects, soil foundations consisting of calcareous sand-filled land are often exposed to reversible tidal waves. This may induce continuous long-term internal erosion of the soil that differs from monotonic seepage conditions, which has not yet been studied from a microscopic perspective. In this study, a selected particle size distribution (PSD) based on the breakage experiments of calcareous sand is adopted. Then, a series of reversed seepage flows is generated using CFD-DEM, taking into account both cyclic frequency and hydraulic gradient. Numerical results examine the overall suffused fine mass, the migration and suffusion degree across the divided layers along seepage, and the microscopic origins of continuous suffusion under reversed hydraulic conditions. Furthermore, the micro-mechanical and energetic evolution of soil skeletons is analyzed. The findings reveal that hydraulic gradient is the primary factor influencing suffusion outcomes at the initial stage (PEM increases from roughly 21% to 24%), while the cyclic frequency determines the long-term result (PEM increases from roughly 30% to 37%). From a microscopic point, the elimination of clogging, combined with energetic instability and force chain network rearrangement, is identified as the origin of continuous suffusion under reversed hydraulic loading.

Effect of cations (Na+, Co2+, Fe3+) contamination in Nafion membrane: A molecular simulations study

The cation contamination is an important reason for the degradation of performance and durability of Nafion membrane, but the contamination mechanism for cations with different valence in Nafion membranes at different water content was not revealed at the microscale. In this study, the molecular dynamics simulations are performed to study the effect of the contamination of cations with various valence (Na+, Co2+, Fe3+) on the Nafion membrane at different water content. The mechanism for the degradation of the membrane performance in the presence of cations has been clarified. Moreover, it is found that cations with high valence have more serious negative impact on the connectivity of water clusters and the rearrangement of hydrogen bond network. This study provides a fundamental and comprehensive insight into the mechanism of the cation contamination in Nafion membrane, which is useful for the design of high durable ion exchange membranes.

Understanding the Multifaceted Mechanism of Compound I Formation in Unspecific Peroxygenases through Multiscale Simulations.

Unspecific peroxygenases (UPOs) can selectively oxyfunctionalize unactivated hydrocarbons by using peroxides under mild conditions. They circumvent the oxygen dilemma faced by cytochrome P450s and exhibit greater stability than the latter. As such, they hold great potential for industrial applications. A thorough understanding of their catalysis is needed to improve their catalytic performance. However, it remains elusive how UPOs effectively convert peroxide to Compound I (CpdI), the principal oxidizing intermediate in the catalytic cycle. Previous computational studies of this process primarily focused on heme peroxidases and P450s, which have significant differences in the active site from UPOs. Additionally, the roles of peroxide unbinding in the kinetics of CpdI formation, which is essential for interpreting existing experiments, have been understudied. Moreover, there has been a lack of free energy characterizations with explicit sampling of protein and hydration dynamics, which is critical for understanding the thermodynamics of the proton transport (PT) events involved in CpdI formation. To bridge these gaps, we employed multiscale simulations to comprehensively characterize the CpdI formation in wild-type UPO from Agrocybe aegerita (AaeUPO). Extensive free energy and potential energy calculations were performed in a quantum mechanics/molecular mechanics setting. Our results indicate that substrate-binding dehydrates the active site, impeding the PT from H2O2 to a nearby catalytic base (Glu196). Furthermore, the PT is coupled with considerable hydrogen bond network rearrangements near the active site, facilitating subsequent O-O bond cleavage. Finally, large unbinding free energy barriers kinetically stabilize H2O2 at the active site. These findings reveal a delicate balance among PT, hydration dynamics, hydrogen bond rearrangement, and cosubstrate unbinding, which collectively enable efficient CpdI formation. Our simulation results are consistent with kinetic measurements and offer new insights into the CpdI formation mechanism at atomic-level details, which can potentially aid the design of next-generation biocatalysts for sustainable chemical transformations of feedstocks.

Effect of biaxial cyclic loading path on the mechanical and microstructure properties of articular cartilage

Cyclic loading stimulation has the potential to change both the mechanical properties and microstructure of cartilage, subsequently damaging the articular cartilage and contributing to joint osteoarthritis. This study focuses on investigating the behavior of knee articular cartilage under biaxial cyclic loading and analyzing the associated microstructural changes at the ultrastructural level. We studied the in-plane biaxial cyclic loading behavior of cartilage with a particular emphasis on understanding the effects of loading paths, taking into consideration the complex loading conditions encountered during daily activities. The experimental results reveal a clear influence of the constraints in the Y-direction (orthogonal direction) on the strain evolution in the X-direction. Furthermore, the variation in orthogonal stress corresponding to the loading path significantly impacts the biaxial mean strain of the test sample. To be specific, the uniaxial path, characterized by no constraints in the Y-direction, demonstrates the highest mean strain of 25.08 ± 0.88% in the X-direction, while the proportional path exhibits the lowest mean strain (10.77 ± 0.49%) in the X-direction due to the Y-direction's largest stress constraint. We explored the effects of stress amplitude and peak stress holding time on mean strain under a square path. Our observations indicate that the mean strain of cartilage increases with the higher stress amplitude or the longer peak stress holding time. Additionally, we analyzed the collagen fibril networks before and after biaxial cyclic loading to reveal the intrinsic deformation mechanism. The rearrangement of collagen fibril networks is closely associated with the stress state of cartilage, where higher stress levels lead to more severe fibril damage.

Rational design engineering of a more thermostable Sulfurihydrogenibium yellowstonense carbonic anhydrase for potential application in carbon dioxide capture technologies

Implementing hyperthermostable carbonic anhydrases into CO2 capture and storage technologies in order to increase the rate of CO2 absorption from the industrial flue gases is of great importance from technical and economical points of view. The present study employed a combination of in silico tools to further improve thermostability of a known thermostable carbonic anhydrase from Sulfurihydrogenibium yellowstonense. Experimental results showed that our rationally engineered K100G mutant not only retained the overall structure and catalytic efficiency but also showed a 3 °C increase in the melting temperature and a two-fold improvement in the enzyme half-life at 85 °C. Based on the molecular dynamics simulation results, rearrangement of salt bridges and hydrogen interactions network causes a reduction in local flexibility of the K100G variant. In conclusion, our study demonstrated that thermostability can be improved through imposing local structural rigidity by engineering a single-point mutation on the surface of the enzyme.