Morphological Transition Research Articles

Effect of boron on the microstructural evolution and wear resistance of high-hardness Fe-based alloy coatings prepared by laser cladding

One of the primary failure modes of 45 steel is severe surface wear, which significantly raises its application cost. In order to improve the wear resistance, high-hardness Fe-based alloy coatings with varying boron contents were prepared on 45 steel substrates by preplaced-powder laser cladding in this study. The effect of boron content on the phase composition and microstructural evolution of the coatings were systematically studied. The proportion, morphology, and distribution characteristics of boride phases in the coatings were discussed in detail. The results demonstrated that the Fe-based alloy coatings with different boron contents were composed of α-Fe, Cr7C3, and Fe2B phases. The boron content had a significant influence on the morphology and proportion of the boride phases. With the increase of boron content, the proportion of boride phases gradually increased and the morphology transition was reticular → cluster-shape → long strip-shape → plate-shape. The composition analysis revealed that the boride was Cr-rich Fe2B phase and the content of Cr in the borides increased with the boron content of the coating. The addition of boron could effectively improve the hardness and wear resistance of the Fe-based coatings, which could be attributed to the boride hard phases in the microstructures. The coating with 6.0 wt% B exhibited the highest microhardness and least amount of wear loss. The wear mechanism of the coating with different boron contents was also discussed.

A conserved zinc-binding site in Acinetobacter baumannii PBP2 required for elongasome-directed bacterial cell shape

Acinetobacter baumannii is a gram-negative bacterial pathogen that causes challenging nosocomial infections. β-lactam targeting of penicillin-binding protein (PBP)-mediated cell wall peptidoglycan (PG) formation is a well-established antimicrobial strategy. Exposure to carbapenems or zinc (Zn)-deprived growth conditions leads to a rod-to-sphere morphological transition in A. baumannii, an effect resembling that caused by deficiency in the RodA-PBP2 PG synthesis complex required for cell wall elongation. While it is recognized that carbapenems preferentially acylate PBP2 in A. baumannii and therefore block the transpeptidase function of the RodA-PBP2 system, the molecular details underpinning cell wall elongation inhibition upon Zn starvation remain undefined. Here, we report the X-ray crystal structure of A. baumannii PBP2, revealing an unexpected Zn coordination site in the transpeptidase domain required for protein stability. Mutations in the Zn-binding site of PBP2 cause a loss of bacterial rod shape and increase susceptibility to β-lactams, therefore providing a direct rationale for cell wall shape maintenance and Zn homeostasis in A. baumannii. Furthermore, the Zn-coordinating residues are conserved in various β- and γ-proteobacterial PBP2 orthologs, consistent with a widespread Zn-binding requirement for function that has been previously unknown. Due to the emergence of resistance to virtually all marketed antibiotic classes, alternative or complementary antimicrobial strategies need to be explored. These findings offer a perspective for dual inhibition of Zn-dependent PG synthases and metallo-β-lactamases by metal chelating agents, considered the most sought-after adjuvants to restore β-lactam potency against gram-negative bacteria.

Facet‐dependent Thermal and Electrochemical Degradation of Lithium‐rich Layered Oxides

Lithium‐rich layered oxides (LLOs) are promising candidate cathode materials for safe and inexpensive high‐energy‐density Li‐ion batteries. However, oxygen dimers are formed from the cathode material through oxygen redox activity, which can result in morphological changes and structural transitions that cause performance deterioration and safety concerns. Herein, a flake‐like LLO is prepared and aberration‐corrected scanning transmission electron microscopy (STEM), in situ high‐temperature X‐ray diffraction (HT‐XRD), and soft X‐ray absorption spectrum (sXAS) are used to explore its crystal facet degradation behavior in terms of both thermal and electrochemical processes. Void‐induced degradation behavior of LLO in different facet reveals significant anisotropy at high voltage. Particle degradation originates from side facets, such as the (010) facet, while the close (003) facet is stable. These results are further understood through ab initio molecular dynamics calculations, which show that oxygen atoms are lost from the {010} facets. Therefore, the facet degradation process is that oxygen molecular formed in the interlayer and accumulated in the ab plane during heating, which result in crevice‐voids in the ab plane facets. The study reveals important aspects of the mechanism responsible for oxygen ‐anionic activity‐based degradation of LLO cathode materials used in lithium‐ion batteries. In particular, this study provides insight that enables precise and efficient measures to be taken to improve the thermal and electrochemical stability of an LLO.

Thermally Triggered Multilevel Diffractive Optical Elements Tailored by Shape-Memory Polymers for Temperature History Sensors.

The morphological transitions induced by external stimuli in shape-memory polymers (SMPs) can be exploited with the real-time response of far-field diffraction patterns in diffractive optical elements (DOEs). In this paper, we combine the temperature characteristics of SMPs and the display characteristics of DOEs to obtain an optical temperature sensing film where the temperature information is taken as a change of far-field diffraction images. This process was achieved by imprinting the micropatterns of the DOEs on the epoxy-based SMP film, which can be programmed to hold a temporary optical image and revert to its original image upon exposure to a specific temperature. Furthermore, the specific temperature at which the image transformation occurs can be customized by varying the chain flexibility of the SMP. Based on a range of transition points, by imprinting the desired combination of SMP-DOEs on a film, a sensor that can record and inform the temperature history is demonstrated. As for the feasible application of this technique, it can be used for the compact and reliable optical temperature indicators, which can be applied in temperature-sensitive industries such as food and pharmaceuticals.

Assessment of an E10 gasoline surrogate: Qualitative and quantitative comparisons of in-cylinder spray morphology

A minimum-component gasoline fuel surrogate that captures both chemical and physical behaviors of a full-distillate fuel is needed for high-fidelity CFD simulations. This study evaluates gasoline spray characteristics in a direct-injection spark-ignition engine under motored operation. Two fuels are compared; PACE-20, which is a 9-component surrogate formulation of RD5-87, is compared with its target fuel RD5-87, which is a full-boiling range research grade E10 gasoline. The spray morphologies of both fuels are recorded for a centrally-located direct-injection 8-hole spray subject to intake air cross-flow during the early part of the intake stroke. High-speed imaging recorded scattered light of the side and axial projections of the liquid spray. Quantitative metrics were developed and employed to facilitate comparison of spray morphologies as well as to identify the transition in spray morphology due to flash boiling. This paper builds on a previous study of RD5-87 where coolant temperature (20°C–100°C), in-cylinder pressure (40–110 kPa), engine speed (650–1950 rpm), and injection pressure (60–180 bar) were systematically changed to span operating conditions with and without flash boiling. Images of the PACE-20 morphology are selected for a sub-set of operating conditions from the previous study where distinctive morphology changes occurred. Visual inspection of the images and quantitative metrics demonstrate that the PACE-20 spray morphology is equivalent to that of the RD5-87 in most cases. The exception was for changes in the ambient-gas pressure where the flash-boiling transition occurred at ∼5 kPa higher in-cylinder pressure for PACE-20. Three empirical metrics, Merging Index, Asymmetry, and Flash Index are proposed here and they were found to be useful both as quantitative comparisons of the fuel morphologies, and for identifying the transition in spray morphology due to flash boiling.

The phylogeny and global biogeography of Primulaceae based on high-throughput DNA sequence data

The angiosperm family Primulaceae is morphologically diverse and distributed nearly worldwide. However, phylogenetic uncertainty has obstructed the identification of major morphological and biogeographic transitions within the clade. We used target capture sequencing with the Angiosperms353 probes, taxon-sampling encompassing nearly all genera of the family, tree-based sequence curation, and multiple phylogenetic approaches to investigate the major clades of Primulaceae and their relationship to other Ericales. We generated dated phylogenetic trees and conducted broad-scale biogeographic analyses as well as stochastic character mapping of growth habit. We show that Ardisia, a pantropical genus and the largest in the family, is not monophyletic, with at least 19 smaller genera nested within it. Neotropical members of Ardisia and several smaller genera form a clade, an ancestor of which arrived in the Neotropics and began diversifying about 20 Ma. This Neotropical clade is most closely related to Elingamita and Tapeinosperma, which are most diverse on islands of the Pacific. Both Androsace and Primula are non-monophyletic by the inclusion of smaller genera. Ancestral state reconstructions revealed that there have either been parallel transitions to an herbaceous habit in Primuloideae, Samolus, and at least three lineages of Myrsinoideae, or a common ancestor of nearly all Primulaceae was herbaceous. Our results provide a robust estimate of phylogenetic relationships across Primulaceae and show that a revised classification of Myrsinoideae and several other clades within the family is necessary to render all genera monophyletic.

Rationalizing the Design of Pluronics-Surfactant Mixed Micelles through Molecular Simulations and Experiments.

Aqueous systems comprising polymers and surfactants are technologically important complex fluids with tunable features dependent on the chemical nature of each constituent, overall composition in mixed systems, and solution conditions. The phase behavior and self-assembly of amphiphilic polymers can be changed drastically in the presence of conventional ionic surfactants and need to be clearly understood. Here, the self-aggregation dynamics of a triblock copolymer (Pluronics L81, EO3PO43EO3) in the presence of three cationic surfactants (with a 12C long alkyl chain but with different structural features), viz., dodecyltrimethylammonium bromide (DTAB), didodecyldimethylammonium bromide (DDAB), and ethanediyl-1,2-bis(dimethyldodecylammonium bromide) (12-2-12), were investigated in an aqueous solution environment. The nanoscale micellar size expressed as hydrodynamic diameter (Dh) of copolymer-surfactant mixed aggregates was evaluated using dynamic light scattering, while the presence of a varied micellar geometry of L81-cationic surfactant mixed micelles were probed using small-angle neutron scattering. The obtained findings were further validated from molecular dynamics (MD) simulations, employing a simple and transferable coarse-grained molecular model based on the MARTINI force field. L81 remained molecularly dissolved up to ∼20 °C but phase separated, forming turbid/translucent dispersion, close to its cloud point (CP) and existed as unstable vesicles. However, it exhibited interesting solution behavior expressed in terms of the blue point (BP) and the double CP in the presence of different surfactants, leading to mixed micellar systems with a triggered morphology transition from unstable vesicles to polymer-rich micelles and cationic surfactant-rich micelles. Such an amendment in the morphology of copolymer nanoaggregates in the presence of cationic surfactants has been well observed from scattering data. This is further rationalized employing the MD approach, which validated the effective interactions between Pluronics-cationic surfactant mixed micelles. Thus, our experimental results integrated with MD yield a deep insight into the nanoscale interactions controlling the micellar aggregation (Pluronics-rich micelles and surfactant-rich micelles) in the investigated mixed system.

Solvent System-Guided Extraction of Centaurium spicatum (L.) Fritch Provides Optimized Conditions for the Biological and Chemical Characteristics of the Herbal Extracts.

Spiked centaury (Centaurium spicatum) is a well-known medicinal plant from the Mediterranean region with various bioactivities, but there are no studies addressing the use of different solvent systems to improve its pharmacological potential. Nine extraction procedures were adapted to study the effects of solvent composition on the content of bioactive compounds in C. spicatum extracts and on corresponding bioactivities. Targeted metabolomics was performed to obtain information on the chemical composition of extracts. Ethanol-water-based extraction procedures were the most efficient in isolating polyphenols, while less polar butanol extract contained the highest amount of iridoids. Antioxidant potential analysis revealed stronger activity in extracts with higher polyphenol content. Bacillus cereus and Staphylococus aureus were designated as the most sensitive bacterial strains to the activity of extracts, while among the micromycetes tested, Penicillium funiculosum was the most susceptible strain. Butanol extract showed antivirulence potential on Candida albicans morphological transition from yeast to hyphal form, and selected extracts were effective against biofilm formation in two Candida species. All the extracts tested in this study showed no cytotoxic activity to immortalize human skin keratinocyte cell line (HaCaT), whereas extracts obtained by ethanol-water extraction stand out for their potent wound healing effects. Moreover, the influence of the extraction solvent system on various bioactivities of C. spicatum is reported herein for the first time. Overall, the results presented in this study promote the use of C. spicatum as a source of natural products with potential antioxidant, wound healing, and antimicrobial applications that are potentially safe for human use.

Red Blood Cell Deformation and Progressive Anemia Following Therapeutic Intervention in Patients With Adult T-Cell Leukemia/Lymphoma.

During therapeutic intervention for adult T-cell leukemia-lymphoma (ATLL), transient red blood cell (RBC) deformations and rapid anemia progression are often observed. These RBC responses are characteristically observed during the treatment of ATLL, and we examined the details and significance of these RBC responses. Seventeen patients withATLL were enrolled. Peripheral blood smears and laboratory findings were collected during the first two weeks after treatment intervention. We examined the transition of erythrocyte morphology and the factors associated with the induction of anemia. RBC abnormalities (i.e., elliptocytes, anisocytosis, and schistocytes) rapidly progressed following therapeutic intervention in five of the six cases for whom evaluable consecutive blood smears were available, with significant improvement evident after two weeks. Changes in RBC morphology were significantly associated with the red cell distribution width (RDW). Laboratory findings from all 17 patients showed various levels of anemia progression. A transient increase in RDW values was observed in 11 cases after therapeutic intervention. The degree of progressive anemia during the two-week period was significantly correlated with increased lactate dehydrogenase and soluble interleukin-2 receptor levels and an increase in RDW (P <0.01). In cases of ATLL, transient progression of RBC morphological abnormalities and RDW value were observed early after therapeutic intervention. These RBC responses may be associated with tumor and tissue destruction. RBC morphology or RDW values may provide important information about the tumor dynamics and general condition of the patients.

Functional analysis of soybean miR156 and miR172 in tobacco highlights their role in plant morphology and floral transition

Soybean (Glycine max), a significant oilseed and protein source for humans and livestock feed, needs short day photoperiod for floral induction. Further, soybean has a paleopolyploid genome with multiple copies of flowering genes adding to the complexity of genetic regulation of flowering, and seed set, especially in investigating the role of the noncoding genome. microRNAs, a class of noncoding RNA, play a regulatory role in plant development. miR156 and miR172 are major components of the essential regulatory hub controlling juvenile and vegetative developments and initiation of reproductive phase change leading to flowering. These microRNAs have been originally isolated and studied from model plant, Arabidopsis. However, a study on soybean microRNAs is lacking. We investigated the temporal expression patterns of gma-miR156a and gma-miR172a and found inversely related - gma-miR156a expression was higher in the vegetative stage, and gma-miR172a expression was elevated under inductive flowering conditions. The functions of gma-miR156a and gma-miR172a were evaluated via heterologous expressions in transgenic tobacco plants (Nicotiana tabacum L.). The analysis of overexpression transgenic lines highlighted that gma-miR156a plays a role in juvenile development via repression of the SPL transcription factor family. In contrast, gma-miR172a plays a pivotal role in the reproductive development phase by down-regulating its target genes, AP2. In addition, ectopic expression of gma-miR156a and gma-miR172a affected plant morphology and physiology during plant growth. Collectively, our results suggest that gma-miR156a and gma-miR172a regulate multiple morpho-physiological traits that could be used to enhance crop yield under changing climate conditions.

Morphological Distribution and Structure Transition of Gluten Induced by Various Drying Technologies and Its Effects on Chinese Dried Noodle Quality Characteristics

Morphological Distribution and Structure Transition of Gluten Induced by Various Drying Technologies and Its Effects on Chinese Dried Noodle Quality Characteristics

Aβ protein growth monitoring by structure-specific label-free THz spectroscopy.

A variety of different amyloid β (Aβ) protein aggregate forms have been linked with severity of Alzheimer's disease (AD) and its aggregation pathway can be a primary biomarker for diagnosis. Our group recently developed the water-based near-field terahertz (THz) spectroscopy technique to measure Aβ in solution (Heo et al., ACS Nano, 2020, 14 (6), 6548-6558). By noting monotonic conductance change with frequency in monomers following Drude tail and nonlinear conductance behaviors in oligomers and fibrils adopting the localization parameter in Smith model, we derived a structure-specific discrete metric that we termed dementia quotient (DQ), which is a structurally defined biophysical index of Aβ aggregation state with modified Drude-Smith model. Furthermore, we investigate Aβ protein dynamics to identify various morphological phase transitions from monomers to fibrils by monitoring the structure-specific DQ values under physiological conditions including body temperature and incubation medium (e.g., buffer versus Matrigel). Our method could ultimately facilitate the early AD diagnosis by clearly detecting of Aβ oligomer state in a nanomolar concentration (∼nm) of the proteins.

Computational module of nanodroplet formation en route to fibrillization of amyloid peptides with designed flanking sequences.

Soluble oligomers populating early amyloid aggregation can be regarded as nanodroplets of liquid-liquid phase separation (LLPS). Amyloid peptides typically contain hydrophobic aggregation-prone regions connected by hydrophilic linkers and flanking sequences, and such sequence hydropathy pattern drives the formation of supramolecular structures in the nanodroplets and modulates subsequent fibrillization. Here, we studied LLPS and fibrillization of coarse-grained amyloid peptides with increasing flanking sequences. Nanodroplets assumed lamellar, cylindrical micellar and spherical micellar structures with increasing peptide hydrophilic/hydrophobic ratios, and such morphologies governed subsequent fibrillization processes. Adding glycine-serine repeats as flanking sequences to Aβ16-22, the amyloidogenic core of amyloid-β, our computational predictions of morphological transitions were corroborated experimentally. The uncovered inter-relationships between peptide sequence pattern, oligomer/nanodroplet morphology, and fibrillization pathway, kinetics and structure may contribute to our understanding of pathogenic amyloidosis in ageing, facilitate future efforts ameliorating amyloidosis through peptide engineering, and aid in the design of novel amyloid-based functional nano-biomaterials and nanocomposites.

Graded mesoderm assembly governs cell fate and morphogenesis of the early mammalian heart

Using four-dimensional whole-embryo light sheet imaging with improved and accessible computational tools, we longitudinally reconstruct early murine cardiac development at single-cell resolution. Nascent mesoderm progenitors form opposing density and motility gradients, converting the temporal birth sequence of gastrulation into a spatial anterolateral-to-posteromedial arrangement. Migrating precardiac mesoderm does not strictly preserve cellular neighbor relationships, and spatial patterns only become solidified as the cardiac crescent emerges. Progenitors undergo a mesenchymal-to-epithelial transition, with a first heart field (FHF) ridge apposing a motile juxta-cardiac field (JCF). Anchored along the ridge, the FHF epithelium rotates the JCF forward to form the initial heart tube, along with push-pull morphodynamics of the second heart field. In Mesp1 mutants that fail to make a cardiac crescent, mesoderm remains highly motile but directionally incoherent, resulting in density gradient inversion. Our practicable live embryo imaging approach defines spatial origins and behaviors of cardiac progenitors and identifies their unanticipated morphological transitions.

Client-induced elongation, expansion, and co-aggregation of the lens alpha-crystallins.

The long-lived nature of the eye lens presents unique challenges to the maintenance of protein stability and function. Age-related accumulation of chemical modifications to proteins in the lens promote the formation of light-scattering aggregates that disrupt vision, leading to cataract: a leading cause of blindness worldwide. To counteract these effects, ∼40% of the lens cytosol is composed of α-crystallins (αAc and αBc isoforms): ATP-independent chaperone “holdases” that work to prevent formation of protein aggregates capable of scattering light. Like other members of the small heat shock protein (sHSP) family of chaperones, the α-crystallins form large and polydisperse oligomeric assemblies that recognize and sequester destabilized proteins, through the formation of soluble chaperone/client complexes. Over time, saturating conditions of unfolding clientele overwhelm lens chaperone capacity, leading to light-scattering co-aggregates. A mechanistic basis for the chaperone/client co-aggregation pathway is not well understood. Here, we applied single-particle electron microscopy and other biophysical techniques to define the morphological transitions associated with chaperone/client co-aggregation, using the model client lysozyme. We observe a mechanism where αAc and αBc chaperone/client sequestration progresses through an “initiation complex” (∼15–20 nm diameter, akin to apo-state α-crystallins), and proceeds through an intermediate elongation/expansion stage where co-aggregates reach dimensions of 50–200 nm. Ultimately, under saturating client conditions, the elongation/expansion complexes appear to cluster (or collapse) to form large light-scattering aggregates (microns in diameter). Ensemble and single-particle analysis techniques show αAc and αBc adopt a similar overall mechanism of expansion/elongation, while some unique isoform-specific features may be attributed to characteristic differences in activity toward lysozyme client. Overall, this work provides a mechanistic basis for understanding how α-crystallins (and perhaps other sHSP's) accommodate destabilized clients and depicts a potential client-induced co-aggregation pathway leading to lens opacification and age-related vision loss.

Synchronized Swarmers and Sticky Stalks: Caulobacter crescentus as a Model for Bacterial Cell Biology.

First isolated and classified in the 1960s, Caulobacter crescentus has been instrumental in the study of bacterial cell biology and differentiation. C. crescentus is a Gram-negative alphaproteobacterium that exhibits a dimorphic life cycle composed of two distinct cell types: a motile swarmer cell and a nonmotile, division-competent stalked cell. Progression through the cell cycle is accentuated by tightly controlled biogenesis of appendages, morphological transitions, and distinct localization of developmental regulators. These features as well as the ability to synchronize populations of cells and follow their progression make C. crescentus an ideal model for answering questions relevant to how development and differentiation are achieved at the single-cell level. This review will explore the discovery and development of C. crescentus as a model organism before diving into several key features and discoveries that have made it such a powerful organism to study. Finally, we will summarize a few of the ongoing areas of research that are leveraging knowledge gained over the last century with C. crescentus to highlight its continuing role at the forefront of cell and developmental biology.

Ag3Sn Morphology Transitions During Eutectic Growth in Sn–Ag Alloys

Eutectic Ag3Sn can grow with a variety of morphologies depending on the solidification conditions and plays an important role in the performance of Pb-free solders. Here, we study morphology transitions in the β-Sn + Ag3Sn eutectic at increasing growth velocity using a combination of real-time X-ray imaging and analytical electron microscopy. Orthorhombic Ag3Sn grew as faceted plates or rods with [010] growth direction and (001) as the largest facet in all three eutectic growth morphologies: Irregular plate, broken-lamellar, and rod. Reproducible β-Sn + Ag3Sn orientation relationships formed for the latter two morphologies. The mechanisms of spacing adjustment and the reversible transition from plate to rod growth are studied for transient solidification after velocity changes. The transition from fully eutectic growth to β-Sn dendrites plus eutectic is reasonably reproduced using a competitive growth criterion. At the highest velocities, Ag3Sn rods developed perturbations whose break down into particles is discussed in terms of unsteady growth and pinch-off mechanisms.

Micelle-Derived Palladium Nanoparticles for Suzuki–Miyaura Coupling Reactions in Water at Room Temperature

Despite the wide utility of colloidal palladium (Pd) nanoparticle (NP)-catalyzed Suzuki–Miyaura cross-coupling reactions in laboratory and industrial synthesis, the easy construction of colloidal Pd NPs and the detailed role of surfactants remain the focus of attention. Here, we present a simple and sustainable strategy to construct a nanoreactor by connecting micelles with Pd NPs. The strategy enables us to employ a pH-induced morphological transition of sugar-based surfactant aggregates, such as worm-like, spherical, and tubular micelles, to investigate the solubilization of organic substrates. Pd NPs are mainly synthesized by the reduction of phenylboronic acid, further stabilized by the sugar-based surfactant micelles. A kinetic model is established, and the apparent activation energy of this reaction in aqueous micellar solutions is determined to be 46.7 kJ/mol. Notably, the recycled aqueous reaction mixture containing the micelles and Pd NPs can be reused.

Combination of current and new electrocardiographic-based criteria: a novel score for the discrimination of left bundle branch capture.

Most of the criteria used to diagnose direct capture of the left bundle branch (LBB) have never been validated in an external sample. We hypothesized that lead aVL might add relevant information, and the combination of several electrocardiograph (ECG)-based criteria might discriminate better LBB capture from left ventricular septal (LVS) capture, than each criterion separately. Single-centre study involving all consecutive patients who received LBB area pacing. LBB capture was defined according to QRS morphology transition criteria during decremental pacing. Multivariate logistic regression analysis was performed to develop a predictive score for LBB capture. A total of 71 patients with confirmed LBB capture were analysed. The optimal cut-off values of R wave peak time (RWPT) in lead V6 (V6-RWPT) and V6-V1 interpeak interval for the discrimination of LBB capture were <83 ms and ≥33 ms, respectively. The RWPT in lead aVL (aVL-RWPT) showed a good discrimination power for the differential diagnosis of LBB capture and LVS capture. The optimal value for aVL-RWPT was 79 ms [sensitivity (SN) and specificity (SP) of 71.2% and 88.4%, respectively]. A new score, with a good diagnostic performance (area under the curve of 0.976), was constructed gathering the information from V6-RWPT, aVL-RWPT, and V6-V1 interpeak interval. The optimal score of 3 points showed a SN and SP of 89.2% and 100%, respectively for the differentiation of LBB capture. ECG-based criteria are useful to confirm the capture of the LBB. The combination of V6-RWPT, aVL-RWPT, and V6-V1 interpeak interval values demonstrated better diagnostic performance than isolated measurements.

In silico design of photoresponsive peptide-based hydrogel with controllable structural and rheological properties

Self-assembly of peptide-based molecules has emerged as an appealing strategy for developing intelligent nanomaterials with favorable biocompatibility and biodegradability. However, how to design the self-assembly systems with controllable and reversible rheological property is still challenging. In this study, coarse-grained molecular dynamics simulation is employed to develop peptides-based hydrogel with photo-stimuli-responsive capability. Our simulations demonstrate that the bisazoFA molecule, generated by grafting azobenzene (azo) moiety to the phenylalanyl-alanine (FA), can self-assemble into twisted networks. With the introduction of diphenylalanine (FF), the micelles undergo morphological transitions from networks to lamellar structures. By manipulating the UV–vis light irradiation, the wormlike structure with orderly-arranged hydrophobic interior is achieved. The distinct self-assembled structures can induce varied viscosity. Furthermore, the mechanisms underlying the self-assembly/stimuli-response processes are examined in the perspective from energy and structure. Specifically, the varied structural/rheological property of systems are driven by the stacking modes between bisazoFA and spatial arrangement of FF molecules. This bottom-up in silico design not only offers a feasible strategy to develop hydrogel with controllable and reversible rheological property, but also enrich our understanding of the self-assembly of peptide-based molecules.