Coil Chain Research Articles

Influence of lactide vs glycolide composition of poly (lactic-co-glycolic acid) polymers on encapsulation of hydrophobic molecules: molecular dynamics and formulation studies

The work demonstrates the preparation of PLGA (PLGA 50:50, PLGA 75:25) nanoparticles, to encapsulate a hydrophobic molecule (coumarin-6), using the microreactor-based continuous process. The formulations were characterized using dynamic light scattering and transmission electron microscopy to determine their size, homogeneity, zeta potential, and surface morphology. The resulting nanoparticles were safe to the CHO cells (≈80% cell survival), at the concentration of ≤600 µg/mL and were successfully taken up by the cells, as demonstrated using confocal microscopy. Moreover, imaging flow cytometry confirmed that the nanoparticles were internalized in 73.96% of the cells. Furthermore, molecular dynamics simulation and docking studies were carried out to explore the effect of polymer chain length of PLGA and lactide vs glycolide (LA:GA) ratio on their compatibility with the coumarin-6 molecules and to study the coiling and flexibility of PLGA in the presence of coumarin-6 molecules. Flory–Huggins interaction parameter (χ) was calculated for polymer chains of varying lengths and LA:GA ratio, with respect to coumarin-6. χ parameter increased with increase in polymer chain length, which indicated superior interaction of coumarin-6 with the smaller chains. Amongst all the polymeric systems, PLGA55 exhibited the strongest interaction with coumarin-6, for all the chain lengths, possibly because of their homogeneous spatial arrangements and superior binding energy. PLGA27 showed better compatibility compared to PLGA72 and PGA, whereas PLA-based polymers exhibited the least compatibility. Analysis of the radius of gyration of the polymer chains in the polymer–coumarin-6 complexes, at the end of molecular dynamics run, exhibited that the polymer chains displayed varying coiling behavior and flexibility, depending upon the relative concentrations of the polymer and coumarin-6. Factors like intra-chain interactions, spatial arrangement, inter-chain binding energies, and polymer–coumarin-6 compatibility also influenced the coiling and flexibility of polymer chains.

Ferulated Pectins from Sugar Beet Bioethanol Solids: Extraction, Macromolecular Characteristics, and Enzymatic Gelling Properties

Pectin from sugar beet (Beta vulgaris L.) (SBP) was extracted from a sugar beet waste (SBW) registering a 4.4% (w/w) yield. SBP presented a weight-average molar mass of 459 kDa, galacturonic acid content of 52.2%, and a low esterification degree (30%). The macromolecular characteristics of SBP revealed a flexible and extended coil chain conformation. The main neutral sugars in SBP were galactose (20.7%), mannose (5.0%), and arabinose (3.60%) while ferulic acid (FA) content was 2.1 µg·mg−1 sample. FA remained in the SBP chain mainly in RG I region even after suffering both, industrial processing and harsh weathering conditions. Consequently, SBP formed covalent gels induced by laccase. Covalent cross-linking content (dimers and trimer of FA) was 0.97 mg·g−1 SBP. The 8-5′, 5-5′, and 8-O-4′ dimers of FA isomers proportions were 75, 17, and 8%, respectively. SBP gels at 4% (w/v ) registered storage (G′) and loss (G″) moduli final values of 44 and 0.66 Pa, respectively. SBP gels were soft and adhesive according to texture profile analysis. Scanning electron microscopy analysis of SBP lyophilized gels revealed an imperfect honeycomb-like structure with 4.5 ± 1.4 µm average cavities diameter.

Clustering and Differentiation of glr-3 Gene Function and Its Homologous Proteins

In order to adapt to the low temperature environment, organisms transmitexcitement to the central system through the thermal sensing system, whichis a classic reflex reaction. The cold receptor GLR-3 perceives cold and produces cold avoidance behavior through peripheral sensory neurons ASER.In order to further understand the gene encoding of the cold sensing glr-3gene and the evolution of its homologous gene group function and proteinfunction, the nucleotide sequence and amino acid sequence of the glr-3gene and its homologous gene in 24 species were obtained and compared.By clustering with the GRIK2 gene sequence of Rana chensinensis, the bioinformatics method was used to predict and sequence analyze the change ofgene, evolution rate, physical and chemical properties of protein, glycosylation sites, phosphorylation sites, secondary structure and tertiary structureof protein. The analysis results show that the glr-3 gene and its homologousgene have obvious positive selection effect. The protein prediction analysisshowed that the glr-3 gene and its homologous genes encoded proteinsin these 25 species were hydrophilic proteins, and the proportion of sidechains of aliphatic amino acids was high. The transmembrane helix waswidespread and there were more N-glycosylation sites and O-glycosylationsites. The protein phosphorylation sites encoded were serine, threonine andtyrosine phosphorylation sites. Secondary structure prediction showed thatthe secondary structure units of the encoded protein were α-helix, β-turn,random coil and extended chain, and the proportion of α-helix was the largest. This study provides useful information on the evolution and function ofthe cold sensing gene glr-3 and its homologous genes.

Development of Functional Materials via Polymer Encapsulation into Metal–Organic Frameworks

Abstract Metal–organic frameworks (MOFs) composed of metal ions and organic ligands have been extensively studied over the last few decades owing to their versatile porous structures with controllable sizes and designable surface functionalities. The encapsulation of polymer chains into MOF pores is a powerful strategy for the preparation of functional materials. The nanochannels of MOFs disrupt the natural coiling of polymer chains and constrain them in extended conformations, facilitating the study of the properties of single polymer chains. The formation of nanocomposites between MOFs and polymers can provide unprecedented material platforms to accomplish several nanoscale functions. Furthermore, the use of regulated nanochannels in MOFs for polymer encapsulation allows the discrimination of the marginal structural differences in individual polymer chains, providing the separation of polymers from complex mixtures.

Macromolecular and thermokinetic properties of a galactomannan from Sophora alopecuroides L. seeds: A study of molecular aggregation

The molecular aggregation of a galactomannan (NSAP-25) from Sophora alopecuroides L. seeds was investigated, where three polydisperse systems were confirmed during particle size analysis, indicating existence of different aggregates composed of random coil chains revealed by circular dichroism. Morphologically, NSAP-25 aggregate of various sizes (200–1200 nm) was possibly multi-stranded and formed by ellipsoid-like particles (20–60 nm) composed of compact coil chain, exhibiting extended amorphous structure with chain-like branches intertwined. Hence, NSAP-25 aggregation was inevitable, which exerted an unignorable effect on augmenting flexibility (β↓, γ↓, α↓ and Lp/ML↓) and compactness (ρ↓, df↑ and C∞↓) of branched random coil chain based on macromolecular analysis, especially when concentration increased. Moreover, it could be relevant to thermokinetic behavior of random nucleation and subsequent growth (A2 model and negative ΔS*) as well as good thermal stability (IPDT, ITS, t0.05, Tm and Tp), thus conferring potential applications for NSAP-25 in food and pharmaceutical industries.

Characterization of exopolysaccharides produced by Weissella confusa XG-3 and their potential biotechnological applications

In this study, exopolysaccharides (EPSs) produced by Weissella confusa XG-3 were characterized. The monosaccharide composition of XG-3 EPS was determined to include glucose according to GC data, and its molecular weight was 3.19 × 106 Da, as determined by HPLC. Scanning electron microscopy (SEM) revealed a smooth, porous, and branched structure, and atomic force microscopy (AFM) confirmed the presence of round lumps and chains on irregular surfaces of XG-3 EPS. The results of the Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) analyses suggested that XG-3 EPS is a linear α-(1,6)-linked dextran. X-ray diffraction (XRD) data confirmed the noncrystalline amorphous structure, and the results of the Congo red assay corresponded to the random coiled chain conformation of XG-3 dextran. XG-3 dextran exhibited good radical scavenging activity and reducing power and possessed high thermal stability, with a degradation temperature (Td) of 306.8 °C. The absolute value of the zeta potential and particle size of XG-3 dextran continually increased with increasing dextran concentration. The water contact angle showed that XG-3 dextran had relatively high hydrophobicity in the presence of sucrose. XG-3 dextran stimulated the growth of Lactobacillus spp. and Bifidobacterium spp. These findings indicate that XG-3 dextran has unique characteristics and can be potentially applied as a food additive and an antioxidant.

Purification, structure and conformation characterization of a novel glucogalactan from Anoectochilus roxburghii

Anoectochilus roxburghii (AR) has been used in food, medicine and ornamental industries for a long time. Anion exchange resin was proposed to purify the sub-fraction of water-extracted AR polysaccharide (ARPP-70), and a homogeneous polysaccharide ARPP-70a was obtained. The structural features of ARPP-70a were characterized using gas chromatography–mass spectrometry (GC–MS), nuclear magnetic resonance (NMR) spectroscopy, and high performance size exclusion chromatograph coupled with multi-angle laser light scattering (HPSEC-MALLS). The relative weight average molecular weight for ARPP-70a was determined to be 14.8 kDa, and the molar ratio of glucose to galactose was 1.0:3.2. The structure of ARPP-70a was elucidated to be glucogalactan, with backbone comprising β-1,4-linked Galp and some α-1,4-linked Glcp. The conformation characteristics of ARPP-70a were supposed to exist as a random coil chain in 0.1 M NaNO3 solution. Moreover, in vitro antioxidant activity assays revealed ARPP-70a exhibited appreciable antioxidant potential. To the best of our knowledge, this is the first study to obtain this type of glucogalactan, and provide systematic information on its structural and conformational properties. This study improved the understanding of the physicochemical characteristics of AR polysaccharide, which is beneficial for its further application in food and medicinal industry.

Structural elucidation of an immunological arabinan from the rhizomes of Ligusticum chuanxiong, a traditional Chinese medicine

In the present study, an immunological arabinan, LCP70-2A, was isolated from Ligusticum chuanxiong for the first time. The absolute molecular weight of LCP70-2A was determined to be 6.46 × 104 g/mol using the HPSEC-MALLS-RID method. The absolute configuration of arabinose in LCP70-2A was determined to be L-configuration. Physicochemical characterization revealed that LCP70-2A was a homogeneous polysaccharide and had a backbone of (1 → 5)-linked α-L-Araf with terminal α-L-arabinose residues at position O-2 and O-3. Molecular conformation analysis showed that LCP70-2A was a branching polysaccharide with a compact coil chain conformation in 0.1 M NaCl solution. In addition, in vitro cell assays showed that LCP70-2A can activate macrophages by enhancing the phagocytosis and potentiating the secretion of immunoregulatory factors including NO, TNF-α, IL-6, and IL-1β. Furthermore, LCP70-2A was proved to promote the production of ROS and NO using the zebrafish model, suggesting that LCP70-2A can be further developed as a candidate supplement for immunological enhancement.

Understanding fracture behavior of epoxy-based polymer using molecular dynamics simulation

With a network structure formed by cross-linking process, epoxy resins possess excellent mechanical properties. Among them, SU-8 photoresist (bisphenol-A epoxy resin) is widely used as coatings in microelectronic applications. This paper reports molecular dynamics simulations of the cross-linking process of SU-8 photoresist with detailed scripts and illustrates fracture behaviors of cross-linked network with in situ visualizations of atomistic details. The epoxy molecular models with the cross-linking degree of 20%, 40%, 60% and 80% are constructed, which possess density, glass transition temperature, and mechanical properties in a good agreement with existing experimental studies on SU-8. For the models with cross-linking degree of 60% and 80%, uncoiling phenomena observed during large-strain tensile deformations are proved to be associated with significant drops of stress and the dissipation of local concentrated energy developed within the stretched structure, which indicates that the coiling of molecular chains is a critical structure for strength of epoxy molecules. The findings from this paper enrich our understandings of molecular details of SU-8 photoresist upon fracture and contribute as a useful reference to atomistic modeling database of cross-linked polymers.

Modulating Orientational Order to Organize Polyhedral Nanoparticles into Plastic Crystals and Uniform Metacrystals.

In nanoparticle self-assembly, the current lack of strategy to modulate orientational order creates challenges in isolating large-area plastic crystals. Here, we achieve two orientationally distinct supercrystals using one nanoparticle shape, including plastic crystals and uniform metacrystals. Our approach integrates multi-faceted Archimedean polyhedra with molecular-level surface polymeric interactions to tune nanoparticle orientational order during self-assembly. Experiments and simulations show that coiled surface polymer chains limit interparticle interactions, creating various geometrical configurations among Archimedean polyhedra to form plastic crystals. In contrast, brush-like polymer chains enable molecular interdigitation between neighboring particles, favoring consistent particle configurations and result in uniform metacrystals. Our strategy enhances supercrystal diversity for polyhedra comprising multiple nondegenerate facets.

Modulating Orientational Order to Organize Polyhedral Nanoparticles into Plastic Crystals and Uniform Metacrystals

AbstractIn nanoparticle self‐assembly, the current lack of strategy to modulate orientational order creates challenges in isolating large‐area plastic crystals. Here, we achieve two orientationally distinct supercrystals using one nanoparticle shape, including plastic crystals and uniform metacrystals. Our approach integrates multi‐faceted Archimedean polyhedra with molecular‐level surface polymeric interactions to tune nanoparticle orientational order during self‐assembly. Experiments and simulations show that coiled surface polymer chains limit interparticle interactions, creating various geometrical configurations among Archimedean polyhedra to form plastic crystals. In contrast, brush‐like polymer chains enable molecular interdigitation between neighboring particles, favoring consistent particle configurations and result in uniform metacrystals. Our strategy enhances supercrystal diversity for polyhedra comprising multiple nondegenerate facets.

Insensitivity of Sterically Defined Helical Chain Conformations to Solvent Quality in Dilute Solution.

The interplay between polymer-polymer and polymer-solvent interactions as well as interactions that impose secondary structures determines the conformation of polymer chains in dilute solution. Polypeptoids-poly(N-substituted glycines) have been shown to form helical secondary structures primarily driven by steric interactions from chiral, bulky side chains, while polypeptoids with a racemic mixture of the same side chains lead to unstructured coil chains with a shorter Kuhn length. Small-angle neutron scattering (SANS) of the polypeptoids in dilute solution reveals that the helical polypeptoids are only locally stiffer than the coil chains formed from the racemic analogue, but exhibit overall flexibility. We show that chain conformations of both helical and coil polypeptoids (in terms of radius of gyration, Rg) are insensitive to solvent quality (parametrized by the second virial coefficient, A2). Potential effects from the bulky, chiral/racemic side chains dominating chain conformations are excluded by comparison with an achiral polypeptoid lacking side chain chirality. The specific interactions between polypeptoid segments are likely dominating the chain conformations in this type of polypeptoids as opposed to polymer-solvent interactions or energetic contributions from the helical secondary structure.

Entropic bonding of the type 1 pilus from experiment and simulation.

The type 1 pilus is a bacterial filament consisting of a long coiled proteic chain of subunits joined together by non-covalent bonding between complementing -strands. Its strength and structural stability are critical for its anchoring function in uropathogenic Escherichia coli bacteria. The pulling and unravelling of the FimG subunit of the pilus was recently studied by atomic force microscopy experiments and steered molecular dynamics simulations (Alonso-Caballero et al. 2018 Nat. Commun. 9, 2758. (doi:10.1038/s41467-018-05107-6)). In this work, we perform a quantitative comparison between experiment and simulation, showing a good agreement in the underlying work values for the unfolding. The simulation results are then used to estimate the free energy difference for the detachment of FimG from the complementing strand of the neighbouring subunit in the chain, FimF. Finally, we show that the large free energy difference for the unravelling and detachment of the subunits which leads to the high stability of the chain is entirely entropic in nature.

An active heteropolysaccharide from the rinds of Garcinia mangostana Linn.: Structural characterization and immunomodulation activity evaluation

A previously undescribed polysaccharide, GMP70-1, was isolated from the rinds of Garcinia mangostana Lin. Physicochemical characterization analysis showed that GMP70-1 (absolute molecular weight: 2.01 × 104 g/mol) is a multi-branched acidic heteropolysaccharide with a compact coil chain conformation in sodium chloride solution. The repeated unit of GMP70-1 was mainly composed of (1 → 5)-linked α-L-Araf, (1 → 3, 5)-linked α-L-Araf, (1 → 2, 4)-linked α-L-Rhap, (1 → 4)-linked β-D-Galp, terminating with t-α-L-Araf, t-α-D-GalpA, and t-β-D-Galp. To explore the medicinal potential responsible for the bioactivity of G. mangostana, an immunomodulatory assay was performed. The in vitro cell test showed that GMP70-1 possessed a prominent immunoregulatory activity by enhancing the phagocytic uptake of neutral red and promoting the secretion of nitric oxide (NO), reactive oxygen species (ROS), tumor necrosis factor-α (TNF-α), interleukin (IL)-6, and IL-1β of macrophages. Furthermore, an in vivo zebrafish evaluation revealed that the production of ROS and NO was significantly increased after treated with GMP70-1.

Convex optimization of coil spacing in cascaded multi-coil wireless power transfer

AbstractIn this paper, we use convex optimization to maximize power efficiency through cascaded multi-coil wireless power transfer systems and investigate the resulting characteristic spacing. We show that although the efficiency is generally a non-convex function of the coil spacing, it can be approximated by a convex function when the effects of higher-order couplings are small. We present a method to optimize the spacing of cascaded coils for maximum efficiency by perturbing the solution of the convex approximation to account for higher-order interactions. The method relies on two consecutive applications of a local optimization algorithm in order to enable fast convergence to the global optimum. We present the optimal configurations of coil systems containing up to 20 identical coils that transfer power over distances up to 4.0 m. We show that when spacing alone is optimized, there exist an optimal number of coils that maximize transfer efficiency across a given distance. We also demonstrate the use of this method in optimizing the placement of a select number of high-Q coils within a system of low-Q relay coils, with the highest efficiencies occurring when the high-Q coils are placed on either side of the largest gaps within the relay coil chain.

Highly efficient extraction of large molecular-weight keratin from wool in a water/ethanol co-solvent

A large number of wool fiber by-products, short and coarse wool fibers are difficult to spin and are disposed of by the wool industry, creating a burden on the environment. In this study, L-cysteine hydrochloride and sodium sulfite were used as reducing agents to extract keratin from natural wool in an ethanol-water mixed system. The molecular weight of the extracted keratin is up to 130 kDa with a high yield of 67%. It has been proven that the reducing agent destroyed partial disulfide bonds, ethanol destroyed partial hydrogen bonds and hydrophobic interactions, and the α-helix chain was converted into a β-folded chain and random coil after extraction by instrumental analysis using a Fourier transform infrared spectrometer and X-ray diffraction. The recombination of small keratin molecules can be proven by the increase in protein particle size and molecular weight via a particle size analyzer and SDS-PAGE respectively.

Chain conformation and rheological properties of an acid-extracted polysaccharide from peanut sediment of aqueous extraction process

A polysaccharide (PPS) in peanut sediment of aqueous extraction process was obtained at pH4.0, purified via anion-exchange chromatography. The composition, chain conformation and rheological properties were investigated. PPS mainly consisted of arabinose, galacturonic acid, xylose, and rhamnose. The intrinsic viscosity [η] was 0.71 dL/g in 0.1 M NaNO3 solution. The weight-average molar mass Mw and polydispersity index were 3.77 × 105 g/mol and 1.25, suggesting high homogeneity. The average radius of gyration (Rg), hydrodynamic radius (Rh), Rg/Rh ratio and conformation parameter v were 25.5, 18.2, 1.40 and 0.21, respectively, indicating compact coil chain conformation with branched structure. Molecular morphology revealed that PPS displayed chain shape comprised of spheres with a diameter range of 15–50 nm and apparent length of chains mainly ranged from 100 to 300 nm. The aggregation caused by molecular self-association enhanced with concentration increasing. Additionally, Newtonian behavior was observed at various concentrations. Increase in temperature effectively broke this behavior. 10.0 wt.% PPS possessed activation energy of 21.7 KJ/mol, was structured liquid and almost fitted Cox-Merz rule. These closely related with its conformation and molecular self-association behavior.

On the entanglement-based mechanism in thermal degradation of vinyl polymers

In thermal degradation of the main-chain-scission type of vinyl polymers as a polymer reaction in melt, we propose that each subsequent elementary reaction of terminal macroradicals generated by the initiation is significantly influenced by entanglement constraint of molten polymer chain which is a reaction field. First, the intermolecular hydrogen abstraction followed by β-scission occurs dominantly at other molecules forming the entanglement constraint tube. As a result, the reaction field becomes rapidly drop in the molecular weight M of molten polymer to the region of M < Mc (characteristic molecular weight) and furthermore M < Me (entanglement molecular weight). Thus, in the reaction field constituted by isolated random coil chain that the entanglement is disentangled and entanglement constraint is released, the intramolecular hydrogen abstraction occurs predominantly because it is controlled by the activation energy and the frequency factor. On the other hand, the direct β-scission (depolymerization) of the macroradicals also takes place in tubes independent of entanglement constraints.

Ionomer Aggregation in Dispersions: Revealing the Role of Solvent By a Fully Atomistic MD Study

Ionomer dispersions are a key ingredient for fabrication of fuel cell catalyst layers. The structural characteristics of ionomer (e.g. Nafion) in dispersions and thereby in the colloidal catalyst ink (comprising Pt/C catalyst and ionomer in a solvent/media) has been speculated to play an influential role in the structure, property and performance of CLs made thereof [1-5]. How or why the chains of the sulphonic acid containing perfluorinated ionomers interact with each other in organic solvents or water or water-alcohol mixtures to form aggregates is not understood. The shape and size of aggregates are still under debate [6]. Furthermore, the commonly deployed x-ray, neutron and light scattering techniques for characterization of ionomer dispersion are limited in their capabilities to shed light on the internal structure of the aggregates, i.e. chain entanglement and coiling, solvent induced swelling, as well as the clustering or dissociation of sulphonic acid. Our all-atom Molecular Dynamics (MD) study aims to reveal the role of solvents on the aforementioned aggregation behavior and aggregate characteristics. Nafion ionomer in common lab solvents such as toluene, IPA, ethanol, glycerol, formic acid, formamide and water was simulated. The results reveal that depending on the solvent ionomers aggregate either due to ionic interactions between protonated sulphonate ion pairs (Figure 1a) or due to hydrophobic effects (Figure 1b). Interesting structure is observed for mixture of alcohol and water (Figure 1c), consistent with the structure proposed by Los Alamos researchers (Welch et al)[6]. The presentation will discuss the results in further details including aggregate shape/size, chain conformation, ionic cluster shape/size, and acid deprotonation for various solvents. A new aggregation phase diagram will be introduced.

Water wire clusters in isostructural Cu(II) and Ni(II) complexes: Synthesis, characterization, and thermal analyses

Hydrogen bonding (HB) interactions are well known to impact the properties of bulk water and within hydrated materials. Most notably, 1D water wires are involved in proton and water transport. Therefore, the design and synthesis of efficient proton conductors in terms of cost and performance are of great interest. In this work, isostructural Cu(II) and Ni(II) complexes based on N,N'-(ethane-1,2-diyl)bis(1-methyl-1H-imidazole-2-carboxamide) (H2L) have been synthesized and fully characterized by single crystal X-ray diffraction, spectroscopic methods, and thermal analysis. Both complexes crystalize in the monoclinic space group P21/c. The asymmetric unit of 1 and 2 contain two equivalents of CuL or NiL and four molecules of water of hydration. In the solid state packing of both complexes, the extended hydrogen bonding (HB) networks form 1D coiled zig-zag chains of water along the crystallographic b-axis. For both complexes, the identical ligand framework, coordination geometries, and solid state packing result in formation of similar HB expansion motifs, which result in analogous thermal stabilities and phase transitions at elevated temperature.