Helical Structure Research Articles

Utilizing epoxy Bletilla striata polysaccharide collagen sponge for hemostatic care and wound healing

Hemostatic materials that are lightweight and possess good blood absorption performance have been widely considered for use in modern wound care. Natural hemostatic ingredients derived from traditional Chinese medicine have also received extensive attention. Bletilla polysaccharides are valued by researchers for their excellent hemostatic performance and good reactivity. Collagen is favored by researchers due to its high biocompatibility and low immunogenicity. In this study, Bletilla striata polysaccharide, the main hemostatic component of Bletilla striata, was activated by epoxy groups, and epoxidized Bletilla striata polysaccharide (EBSP) was prepared. Then, EBSP was crosslinked with collagen under alkaline conditions, and a new hemostatic material that was an epoxidized Bletilla polysaccharide crosslinked collagen hemostatic sponge was prepared. We demonstrated that endowing collagen with better hemostatic performance, cytocompatibility, and blood compatibility does not destroy its original three-stranded helical structure. Compared with the medical gauze, hemostasis time was shorter (26.75 ± 2.38 s), and blood loss was lower (0.088 ± 0.051 g) in the rat liver injury hemostasis model. In the rat model of severed tail hemostasis, hemostasis time was also shorter (47.33 ± 2.05 s), and the amount of blood loss was lower (0.330 ± 0.122 g). The sponge possessed good hemostatic and healing performance.

First GMVA observations with the upgraded NOEMA facility: VLBI imaging of BL Lacertae in a flaring state

We analyze a single-epoch Global mm-VLBI Array (GMVA) observation of the blazar BL\,Lacertae (BL\,Lac) at 86\,GHz from April 2021. The participation of the upgraded, phased Northern Extended Millimetre Array (NOEMA) adds additional sensitivity to the GMVA, which has facilitated the imaging of BL\,Lac during an unprecedentedly strong gamma -ray flare. We aim to explore the nature of the inner subparsec jet of BL\,Lac and the impact of the NOEMA participation in the observation. For the data reduction, we employed two advanced automatic pipelines: rPICARD for the flux density calibration as well as the model-agnostic signal stabilization and GPCAL for the antenna leakage calibration. The conventional hybrid imaging (CLEAN\,$+$\,amplitude and phase self-calibration) was applied to the calibrated visibilities to generate final VLBI images. We performed a ridge-line analysis and Gaussian model-fits on the final jet image to derive the jet parameters. In our data, the presence of NOEMA improves the image sensitivity by a factor of 2.5. The jet shows a clear wiggling structure within 0.4\,mas from the core. Our ridge-line analysis suggests the presence of a helical jet structure (i.e., a sinusoidal pattern). Six circular Gaussian components were fitted to the inner jet region. We estimated an apparent brightness temperature of sim 3\,times \,1012\,K in the two innermost components. They are likely to be highly boosted by relativistic beaming effect. We find four significant polarized knots in the jet. Interestingly, two of them are located in the core region. Finally, we suggest a number of physical scenarios to interpret our results.

Synthesis of Nonsymmetric NBN-Embedded [6]- and [7]Helicenes with Amplified Activities.

Two C1-symmetric heterohelicenes were constructed by nonsymmetrically extending the ortho-fused structures of a C2v-symmetric NBN-embedded phenalene derivative and featured intense luminescence, large Stokes shifts, and successive reversible redox behaviors. Increasing one fused phenyl unit in such a helical structure led to a 10-fold-enhanced dissymmetry factor. Their strong double hydrogen-bond-donating capability makes them distinctly red-shifted in absorption, emission, and CD and CPL spectra upon the addition of fluoride anion.

Preparation and temperature-controlled morphology of helical microrods composed of supramolecular α-cyclodextrin assemblies.

Significant efforts have been devoted so far to artificially fabricate supramolecular helical nano- and microstructures through the regulated assembly of biological and synthetic building blocks. However, the preparation of supramolecular helical structures with a regulated morphology remains challenging. Here, helical microrods composed of supramolecular α-cyclodextrin (α-CD) assemblies were fabricated by allowing an α-CD/1,1,1,3,3,3-hexafluoro-2-propanol (HFIP)/2-pentanol mixture to stand at 30-60 °C under high humidity conditions. The morphology could be controlled by temperature to produce helical microrods with a regulated pitch and length. These helical rods can be applied as optical devices, chiral separation devices and asymmetric catalysts.

Nonreciprocity and chirality hosted by ferromagnetic helical chains: Heat generation vs spin filtering

Motivated by the booming development of spintronics based on chiral helical microstructures, we employed the standard nonequilibrium Green’s function theory to study nonreciprocity and chirality of the heat generation and spin filtering in ferromagnetic helical chains. Our results demonstrate that magnetization, spin–orbit interaction, and nonstep electrostatic potential distribution by bias jointly determine nonreciprocity of the heat generation, and only spin–orbit interaction determines nonreciprocity of the spin-polarized current. Chirality of the heat generation and spin-polarized current is determined by both magnetization and spin–orbit interaction, and some quantitative relationships related to chirality were discovered. However, a transverse field can break these relations and suppress heat generation significantly and modulate nonreciprocity and chirality of the spin-polarized current effectively. By further simulating the critical electrostatic potential distribution, we found with the transverse field applied, compared to the case with zero temperature, that the finite temperature less than one characteristic phonon energy can suppress nonreciprocity of the heat generation while enhancing that of the spin filtering. In terms of chirality, compared to the left-handed helical structure, the right-handed one is more advantageous for designing spin filtering diodes.

Optimized shape design and thermal characteristics investigation of helically coiled tube type heat exchanger

The effects of the helical coil tube designs on heat transfer characteristics during heating process were conducted by some researchers and confirmed that the conventional helical coil tube was not the ideal shape for important heat transfer. Despite this, there was no published paper that presented the optimal helical coil structure for important heat transfer. Therefore, this work addresses the influence of different helical coil structure designs on heat transfer characteristics and temperature distribution during heating process. The study was performed for three configurations named constant-diameter coil, variable-diameter coil and variable-pitch coil. Based on CFD simulation, the mathematical model was validated with experimental results and show good agreement. The results suggest that the helical coil with variable-pitch gives the best heat transfer performance compared with other helical coil structure. Among all considered designs, the combined properties of the helical coil with variable-pitch were better than that of other helical coil structures. As a result, this work could provide a shortcut method in the selection of the appropriate helical coil immersed or wrapped on the tank which need the high heat transfer.

Prediction of the Structural Color of Liquid Crystals via Machine Learning

Materials that generate structural color may be promising alternatives to dyes and pigments due to their relative long-term stability and environmentally benign properties. Liquid crystal (LC) mixtures of cholesteryl esters demonstrate structural color due to light reflected from the helical structure of the self-assembled molecules. The apparent color depends on the pitch length of the liquid crystal. While a wide range of colors have been achieved with such LC formulations, the nature of the pitch–concentration relationship has been difficult to define. In this work, various machine learning approaches to predict the reflected wavelength, i.e., the position of the selective reflection band, based on LC composition are compared to a Scheffe cubic model. The neural network regression model had a higher root mean squared error (RMSE) than the Scheffe cubic model with improved predictions for formulations not included in the dataset. Decision tree regression provided the best overall performance with the lowest RMSE and predicted position of the selective reflection band within 0.8% of the measured values for LC formulations not included in the dataset. The predicted values using the decision tree were over two-fold more accurate than the Scheffe cubic model. These results demonstrate the utility of machine learning models for predicting physical properties of LC formulations.

Design and Analysis of Bionic Continuum Robot With Helical Winding Grasping Function

Abstract In the field of grasping application, continuum robots are characterized by flexible grasping and high adaptability. Based on research on the physiological structure and winding method of seahorses, a continuum robot with a helical winding grasping function is presented in this paper. The continuum robot is driven by cables and uses a new flexural pivot with large deformation as a rotation joint. Firstly, based on the Serret–Frenet frame of the spatial cylindrical helix, the helical winding continuum robot is modeled and solved. The change rules of parameters such as the rotation angle of the joint and the helix parameters under the helical winding method are derived. Then, the compliance matrix of the joint is solved using the structural matrix method, and a stiffness model is established to analyze the relationship between the load and deformation of the continuum robot. The kinematics model of the continuum robot is established by using the modified Denavit–Hartenberg parameter method. The static model of the continuum robot is solved by vector analysis under the condition of considering gravity, and the relationship between the length change of cables and joint curvature is obtained. Finally, the stiffness model and static model of the continuum robot are verified by simulations and experiments. The test results show that within a certain radial range, the continuum robot has the function of helical winding and grasping for objects. Compared to the previous imitation seahorse tail robot, the helical winding structure not only provides a larger grasping area compared to in-plane form but also achieves a better bionic effect.

Helical magnetic micromotors decorated with nickel ferrocyanide for the active and rapid adsorption of radiocesium in water

Separating radioactive cesium from nuclear waste and contaminated environments is critical to mitigate radiological hazards. In response to this need, remote-controllable and Cs-selective micromotor adsorbents have been considered as a promising technology for rapid in-situ cleanup while minimizing secondary waste and radiation exposure to workers. In this study, we demonstrate the active and rapid removal of a radioactive contaminant from water by leveraging the magnetic manipulation capabilities of a helical and magnetic Ni micromotor coated with Cs-selective nickel ferrocyanide (NiFC). The use of polyvinyl alcohol fibers as a template enables the straightforward preparation of the helical wire structure, allowing for precise control over the diameter and pitch of the helix through simple twisting with Ni wires. By harnessing Ni2+ ions eluted from the Ni micromotor in an acid solution, we successfully fabricate NiFC-coated Ni (NiFC/Ni) micromotors that exhibit a selective removal efficiency greater than 98% for 137Cs, even in the presence of high concentrations of competing Na+ ions. Under the influence of an external magnetic field, the NiFC/Ni micromotor demonstrates rapid motion, achieving a pulling motion (100 body lengths per second) through a magnetic gradient and a tumbling motion (46 body lengths per second) induced by a rotating magnetic field. The tumbling motion of the NiFC/Ni micromotor substantially improves the Cs adsorption rate, resulting in a rate that surpasses that achieved under nonmoving conditions by a factor of 21. This improved adsorption rate highlights the considerable potential of magnetically manipulated micromotor self-propulsion for efficient water-pollution treatment.

Form factor of helical structures and twisted fibres.

A general formalism is presented for the isotropically averaged single-chain scattering function (form factor) of single, double, triple and higher-order helices, as well as twisted fibres consisting of concentric layers of strands. Form factors for double and triple helices with differently sized grooves have also been derived. The formulas include the longitudinal and transverse interference over the pitch and radius of the helices, respectively. The results may be useful for the analysis of small-angle scattering data of (bio)macromolecules or molecular assemblies exhibiting a helical arrangement.

Control of expansive soil desiccation cracks via helical auxetic yarn

Soil shrinkage leads to cracking of expansive soil during desiccation. Prevention of crack propagation in soil is of paramount importance. This research examines the effect of auxetic yarns, in control of expansive soil desiccation cracks. In this study, auxetic yarns with optimal properties were produced. Using an innovative test method, the influence of auxetic yarn structure on the prevention of soil crack propagation was investigated. It was found that the inclusion of auxetic yarns in the expansive soil results in a 9.94% reduction in crack propagation of the soil. In order to confirm the positive effect of auxetic yarns on the behavior of the soil samples, pull-out test was conducted on the auxetic yarns incorporated in the soil samples. The interaction between the soil and the auxetic yarn was found to be much higher than the interaction between the equivalent non-auxetic yarn and the same soil. This was not only attributed to the transverse expansion of auxetic yarn, but also to the helical structure that occurs in such yarn during the pull-out. The auxetic effect of the yarn results in a 27.3% increase in the force needed to pull the yarn from the soil matrix.

Classification of helical polymers with deep-learning language models

Many macromolecules in biological systems exist in the form of helical polymers. However, the inherent polymorphism and heterogeneity of samples complicate the reconstruction of helical polymers from cryo-EM images. Currently, available 2D classification methods are effective at separating particles of interest from contaminants, but they do not effectively differentiate between polymorphs, resulting in heterogeneity in the 2D classes. As such, it is crucial to develop a method that can computationally divide a dataset of polymorphic helical structures into homogenous subsets. In this work, we utilized deep-learning language models to embed the filaments as vectors in hyperspace and group them into clusters. Tests with both simulated and experimental datasets have demonstrated that our method – HLM (Helical classification with Language Model) can effectively distinguish different types of filaments, in the presence of many contaminants and low signal-to-noise ratios. We also demonstrate that HLM can isolate homogeneous subsets of particles from a publicly available dataset, resulting in the discovery of a previously unreported filament variant with an extra density around the tau filaments.

Ultra-wideband chiroptical response by tri-layer anisotropic plasmonic metamaterial

The use of plasmonic chiral metamaterials for the control of circular polarization has the potential to replace conventional optical equipment for polarization-related applications. The ultra-broadband chiroptic response using plasmonic constituents is delivered by elaborate three-dimensional (3D) helical structures, nevertheless, their implementation is complicated, time-consuming, and poses a significant scaling difficulty at the nano level. Ultra-broadband response from planar constituents is particularly necessary as a means to circumvent the challenges of 3D metamaterials. Here we present a planar plasmonic structure composed of tri-layer anisotropic arrays constituting nanowires and cut-wires to generate dual overlapped chiral bands. Based on this tri-layer approach, we numerically realized ultra-broadband planar plasmonic metamaterials to function in the near- and mid-infrared regions with a bandwidth range of 1.38–3.07 µm and 4.00–8.10 µm, and maximum circular dichroism performance of 0.90 and 0.92 respectively. The structures are ultracompact, misalignments tolerant, and can be extended to additional spectral regions through structural engineering. The proposed metamaterial has the potential to be used in the creation of ultra-compact, high-performance devices for a wide variety of uses, such as those in the fields of optical communication, biological diagnosis, high-contrast polarization imaging, high-accuracy polarimetric measurements, and spectroscopy.

Single‐Crystal‐to‐Single‐Crystal Topochemical Synthesis of a Collagen‐inspired Covalent Helical Polymer

AbstractThere is much demand for crystalline covalent helical polymers. Inspired by the helical structure of collagen, we synthesized a covalent helical polymer wherein the repeating dipeptide Gly‐Pro units are connected by triazole linkages. We synthesized an azide and alkyne‐modified dipeptide monomer made up of the repeating amino acid sequence of collagen. In its crystals, the monomer molecules aligned in head‐to‐tail fashion with proximally placed azide and alkyne forming supramolecular helices. At 60 °C, the monomer underwent single‐crystal‐to‐single‐crystal (SCSC) topochemical azide‐alkyne cycloaddition polymerization, yielding a covalent helical polymer as confirmed by single‐crystal X‐ray diffraction (SCXRD) analysis. Compared to the monomer crystals, the polymer single‐crystals were very strong and showed three‐fold increase in Young's modulus, which is higher than collagen, many synthetic polymers and other materials. The crystals of this covalent helical polymer could bear loads as high as 1.5 million times of their own weight without deformation. These crystals could also withstand high compression force and did not disintegrate even at an applied force of 98 kN. Such light‐weight strong materials are in demand for various technological applications.

Single-Crystal-to-Single-Crystal Topochemical Synthesis of a Collagen-inspired Covalent Helical Polymer.

There is much demand for crystalline covalent helical polymers. Inspired by the helical structure of collagen, we synthesized a covalent helical polymer wherein the repeating dipeptide Gly-Pro units are connected by triazole linkages. We synthesized an azide and alkyne-modified dipeptide monomer made up of the repeating amino acid sequence of collagen. In its crystals, the monomer molecules aligned in head-to-tail fashion with proximally placed azide and alkyne forming supramolecular helices. At 60 °C, the monomer underwent single-crystal-to-single-crystal (SCSC) topochemical azide-alkyne cycloaddition polymerization, yielding a covalent helical polymer as confirmed by single-crystal X-ray diffraction (SCXRD) analysis. Compared to the monomer crystals, the polymer single-crystals were very strong and showed three-fold increase in Young's modulus, which is higher than collagen, many synthetic polymers and other materials. The crystals of this covalent helical polymer could bear loads as high as 1.5 million times of their own weight without deformation. These crystals could also withstand high compression force and did not disintegrate even at an applied force of 98 kN. Such light-weight strong materials are in demand for various technological applications.

Liquid Crystals Doped with Chiral Fluorescent Polymer: Multi-Color Circularly Polarized Fluorescence and Room-Temperature Phosphorescence with High Dissymmetry Factor and Anti-Counterfeiting Application.

Chiral nematic liquid crystals (N*-LCs) can tremendously amplify circular polarized luminescence (CPL) signals. Doped emissive N*-LCs have been substantially explored. However, their CPL performances still need to be improved, majorly due to the unsatisfying helical twisting power (HTP) of commonly used chiral fluorescent dopants. Chiral fluorescent helical polymers (CFHPs) have outstanding optical activity and CPL performance. The present contribution reports the first success in constructing emissive N*-LCs by doping CFHP into nematic liquid crystals (5CB, N-LCs). The helical assembly structures of N*-LCs effectively amplify CPL signals of the CFHP. Owing to the high HTP of CFHP, selective reflection band of N*-LC can be adjusted to fully cover its emission band. A nearly pure CPL with dissymmetry factor (glum ) up to -1.87 is realized at 9 wt% doping concentration. Taking advantage of selective reflection mechanism, multi-color CPL-active N*-LCs with high glum are fabricated via further adding achiral fluorophores. Also noticeably, circularly polarized room-temperature phosphorescence (CPRTP) with glum up to -1.57 is achieved. Anti-counterfeiting application is demonstrated exploiting multi-mode optical characteristics of the created N*-LCs. The established strategy for constructing emissive N*-LCs provides a platform for future exploring CPL-active N*-LCs. This article is protected by copyright. All rights reserved.

Mesoscale dislocation dynamics modeling of incipient plasticity under nanoindentation

A mesoscale dislocation dynamics model which couples three-dimensional dislocation dynamics (DD), and finite element method (FEM) was used to investigate the mechanical response of Aluminum (Al) single crystal under spherical nanoindentation. Together with an atomistically informed nucleation model, the dislocation dynamics model can capture both the dynamic evolution of dislocations under the complex stress state of indentation and the corresponding constitutive response of material. The resulting load-displacement curves and the evolution of dislocation microstructures were analyzed to provide insights into the underlying deformation mechanism for incipient plasticity under nanoindentation. Our model could show the transition of the governing mechanism for plasticity from nucleation-controlled plasticity to pre-existing source-driven plasticity with increasing indenter size, as shown in recent experiments. In addition, it could capture a clear picture on incipient plasticity including the formation of prismatic loops through successive cross-slips of nucleated dislocations, such as rhombus loop and prismatic helical structures, which agrees well with atomistic modeling results.

Fate of pulse globulin proteins molecular Structure and composition on high moisture extrusion

Mungbean and lentil proteins are gaining attention for the production of high moisture extrusion (HME)-based meat- and dairy-analogues. However, understanding the mechanism of fibrous structure formation and molecular and higher-order changes in HME remains limited. Globulin protein isolates from mungbean (MBPI), green lentil (GLPI) and yellow pea (YPPI) along with commercial soy (CSPI) and yellow pea (CPPI) protein were investigated for their pasting properties using high-pressure rapid visco analyser (RVA), and the formation of anisotropic structures and molecular changes at constant HME conditions. Vicilin-rich MBPI showed higher viscosity on RVA, consumed higher specific mechanical energy (SME) during extrusion, and developed extrudates with higher textural strength and cutting force than proteins with both legumin and vicilin-like globulins, i.e. GLPI and YPPI. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and size-exclusion chromatography (SEC) of extrudates' soluble proteins showed dissociation of vicilin-like globulins into their smaller subunits. In contrast, legumin-like globulins were reaggregated into higher molecular weight soluble macromolecules. Further, SDS-PAGE of extrudates’ total protein revealed the involvement of legumin-like globulin in the macrostructure network of the extrudates. During HME, native unfolded structures were destroyed with conversion, predominately driving changes in the tertiary structure (thermal denaturation) and secondary structure with loss of helical structure to formation of random coil and beta-sheet structures. Protein extractability in different solvents was greatly reduced, with covalent and non-covalent interactions being majorly involved in the stabilisation of extrudates structure. Protein composition, and in particular vicilin-legumin ratio and protein conformation, determined the structural development and molecular changes in HME.

Thermoresponsive Helical Dendronized Poly(phenylacetylene)s: Remarkable Stabilization of Their Helicity via Photo-Dimerization of the Dendritic Pendants.

Dynamic helical polymers can change their helicity according to external stimuli due to the low helix-inversion barriers, while helicity stabilization for polymers is important for applications in chiral recognition or chiral separations. Here, we present a convenient methodology to stabilize dynamic helical conformations of polymers through intramolecular cross-linking. Thermoresponsive dendronized poly(phenylacetylene)s (PPAs) carrying 3-fold dendritic oligoethylene glycol pendants containing cinnamate moieties were synthesized. These polymers exhibit typical features of dynamic helical structures in different solvents, that is, racemic contracted conformations in less polar organic solvents and predominantly one-handed stretched helical conformations in highly polar solvents. This dynamic helicity can be enhanced through selective solvation by increasing the polarity of the organic solvents or simply via their thermally mediated dehydration in water. However, through photocycloaddition of the cinnamate moieties between the neighboring pendants via UV irradiation, these dendronized PPAs adopt stable helical conformations either below or above their phase transition temperatures in water, and their helical conformations can even be retained in less polar organic solvents. Spectroscopic and atomic force microscopy measurements demonstrate that photocycloaddition between the cinnamate moieties occurs on the individual molecular level, and this is found to be helpful in restraining the photodegradation of the PPA backbones. Molecular dynamics simulations reveal that the spatial orientation of the pendants along the rigid polyene backbone is crucial for the photodimerization of cinnamates within one helix pitch.

Purification, Structural Characterization, and Antitumor Activity of a Polysaccharide from Perilla Seeds.

A previous study found that a crude Perilla seed polysaccharide (PFSP) fraction exhibited obviously antitumor activity; however, the structural characterization and antitumor properties of this polysaccharide remain unclear. In this study, the PFSP was extracted and purified via combined column chromatography, and the structure of a single polysaccharide fraction was characterized by methylation, IC, GC-MS, NMR, and AFM. The results demonstrated that the efficient antitumor polysaccharide fraction PFSP-2-1 was screened from PFSP with a relative molecular weight of 8.81 × 106 Da. The primary structure of the PFSP main chain was →1)-Araf-(5→, →1,3)-Galp-(6→, →1)-Galp-(6→, →1,3)-Araf-(5→ and →1)-Xylp-(4→, and that of the side chains was →1)-Arap, →1,3)-Galp-(6→, →1)-Araf and →1)-Glcp-(4→, →1)-Galp-(3→ and →1)-Glcp, leading to a three-dimensional helical structure. CCK-8 experiments revealed that PFSP-2-1 significantly inhibited the growth of human hepatocellular carcinoma cells in vitro (p < 0.05), and its inhibitory effect positively correlation with the concentration of PFSP-2-1, and when the concentration of PFSP-2-1 was 1600 µg/mL, it showed the highest inhabitation rate on three hepatocellular carcinoma cells (HepG-2, Hep3b, and SK-Hep-1), for which the survival rates of HepG-2, Hep3b, and SK-Hep-1 were 53.34%, 70.33%, and 71.06%. This study clearly elucidated the structure and antitumor activity of PFSP-2-1, which lays a theoretical foundation for revealing the molecular mechanism of antitumor activity of Perilla seed polysaccharides and provides an important theoretical basis for the development of high-value Perilla.