Formation Of Supramolecular Structures Research Articles

Studying the structural organization of non-membranous protein hemoglobin in a lipid environment after reconstitution

In our current work we have developed a supported 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayer with embedded hemoglobin, reconstituted via detergent-mediated method. Microscopic studies revealed that the hemoglobin molecules could be visualized without any labelling agents. The reconstituted proteins assemble themselves as supramolecular structures to adapt to lipid bilayer environment. The nonionic detergent, n-octyl-β-d-glucoside (NOG) used for insertion of hemoglobin played an important role in formation of these structures. When concentrations of lipid, protein and detergent were raised by four folds, we observed phase separation by protein molecules within bilayer via protein-protein assembly. This phase separation process exhibited extremely slow kinetics to form large stable domains with correlation times in the order of minutes. Confocal Z-scanning images showed that these supramolecular structures generated membrane deformities. UV–Vis, Fluorescence and Circular Dichroism (CD) measurement indicated minor structural change to expose the hydrophobic regions of the protein to adjust the hydrophobic stress of the lipid environment whilst Small Angle Neutron Scattering (SANS) results indicated that the hemoglobin molecules retained their overall tetrameric form in the system. In conclusion, we state that this investigation allowed us to closely inspect some rare but noteworthy phenomena like the formation of supramolecular structures, large domain formation and membrane deformation etc.

Sуnthesis of terpene–methacrylic acid copolymers and their effect on the stability of inorganic dispersions in the presence of cationic surfactants

Copolymers of methacrylic acid and natural terpene monomers (α-pinene; β-pinene; ∆3-karene) with the molecular weight of (0.3–0.5)∙104 and a content of carboxyl groups of 14.5–16.3 % were synthesized. For the synthesized copolymers, hydrodynamic radius and the Kuhn segment, which characterizes flexibility of a polymer chain, were determined, as well as the Huggins constant in aqueous and saline solutions, and concentration regions for formation of supramolecular structures. In the presence of a cationic surfactant (benzetonium chloride, Hyamine), depending on the concentration of copolymers in the system, polymer-surfactant complexes were formed in soluble and insoluble forms. It has been shown that the effectiveness of the stabilizing action of soluble complexes with respect to an aqueous dispersion of calcium carbonate increases with an increase in the content of nonpolar groups in the polymer chain. A cationic surfactant (Hyamine) has been proposed as a precipitant in the method for the quantitative determination of carboxyl-containing polymers in aqueous and saline media.

In-situ growth of low-dimensional perovskite-based insular nanocrystals for highly efficient light emitting diodes

Regulation of perovskite growth plays a critical role in the development of high-performance optoelectronic devices. However, judicious control of the grain growth for perovskite light emitting diodes is elusive due to its multiple requirements in terms of morphology, composition, and defect. Herein, we demonstrate a supramolecular dynamic coordination strategy to regulate perovskite crystallization. The combined use of crown ether and sodium trifluoroacetate can coordinate with A site and B site cations in ABX3 perovskite, respectively. The formation of supramolecular structure retard perovskite nucleation, while the transformation of supramolecular intermediate structure enables the release of components for slow perovskite growth. This judicious control enables a segmented growth, inducing the growth of insular nanocrystal consist of low-dimensional structure. Light emitting diode based on this perovskite film eventually brings a peak external quantum efficiency up to 23.9%, ranking among the highest efficiency achieved. The homogeneous nano-island structure also enables high-efficiency large area (1 cm2) device up to 21.6%, and a record high value of 13.6% for highly semi-transparent ones.

NaDES as a green technological approach for the solubility improvement of BCS class II APIs: An insight into the molecular interactions

Recently, Natural Deep Eutectic Solvents (NaDES) have emerged as potential solvents for boosting drug bioavailability. In this work, the mechanism of solubility enhancement of some APIs belonging to BCS class II (tolbutamide, nimesulide, domperidone and cinnarizine) in these eutectic bio-solvents was investigated in order to get deeper insights into the molecular interactions between the NaDES components and the selected drugs. Different NaDES formulations based on choline chloride, proline, solid organic acids (citric, tartaric and malic acid), sugars (glucose and xylitol) and water were prepared by mild heating (70 °C). Characterization of unloaded NaDES (pH, Karl Fisher titration, viscosity and FTIR analysis) indicated that the type of Hydrogen Bond Acceptor (HBA) and Hydrogen Bond Donor (HBD), their molar ratio as well as water amount strongly affect the extent of H-bonding interactions. Hard gelatin capsules filled with NaDES maintained their integrity until 6 months, proving that all water molecules participate in H-bond network. APIs’ solubility enhancement was significant in all NaDES with respect to buffer solutions (pH 1.2 and 6.8). Analysing NaDES having Choline as HBA, it was found that the solubility of smaller molecules increased using larger HBD, while higher molecular weight APIs can be better inserted into the network formed by smaller HBD. NOE experiments demonstrated the formation of a robust supramolecular structure among the protons of choline, those of organic acid and water. In addition, 1D ROESY spectra revealed for the first time the crucial role of choline (methyl groups) in establishing hydrophobic interactions with the relative aliphatic or aromatic portion of the drugs. These data suggest the complex structure of the API-NaDES supramolecular assembly and underline that drug solubility is dependent on a balance network of H-bonds and hydrophobic interactions as well. Understanding the type of interactions between the API and NaDES is essential for their use as effective solubilisation aid.

Entropically-Driven Co-assembly of l-Histidine and l-Phenylalanine to Form Supramolecular Materials.

Molecular self- and co-assembly allow the formation of diverse and well-defined supramolecular structures with notable physical properties. Among the associating molecules, amino acids are especially attractive due to their inherent biocompatibility and simplicity. The biologically active enantiomer of l-histidine (l-His) plays structural and functional roles in proteins but does not self-assemble to form discrete nanostructures. In order to expand the structural space to include l-His-containing materials, we explored the co-assembly of l-His with all aromatic amino acids, including phenylalanine (Phe), tyrosine (Tyr), and tryptophan (Trp), all in both enantiomeric forms. In contrast to pristine l-His, the combination of this building block with all aromatic amino acids resulted in distinct morphologies including fibers, rods, and flake-like structures. Electrospray ionization mass spectrometry (ESI-MS) indicated the formation of supramolecular co-assemblies in all six combinations, but time-of-flight secondary-ion mass spectrometry (ToF-SIMS) indicated the best seamless co-assembly occurs between l-His and l-Phe while in the other cases, different degrees of phase separation could be observed. Indeed, isothermal titration calorimetry (ITC) suggested the highest affinity between l-His and l-Phe where the formation of co-assembled structures was driven by entropy. In accordance, among all the combinations, the co-assembly of l-His and l-Phe produced single crystals. The structure revealed the formation of a 3D network with nanocavities stabilized by hydrogen bonding between -N (l-His) and -NH (l-Phe). Taken together, using the co-assembly approach we expanded the field of amino acid nanomaterials and showed the ability to obtain discrete supramolecular nanostructures containing l-His based on its specific interactions with l-Phe.

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.

Influence of cutting ceramics on the formation of the thermoplastics supramolecular structure

The question of the efficiency of turning processing of thermoplastic polymer materials with cutting ceramics is considered. The fact of a decrease in the values of the cutting force when turning the investigated thermoplastics with a tool made of ceramic material KNT16 was experimentally established. It has been experimentally proven that turning caprolon and fluoroplastic using a KNT16 cermet cutting insert leads to the formation of a supramolecular structure of a high degree of homogeneity.

Tuzaklamalı İyon Hareketliliği-Kütle Spektrometrisi Tekniği Kullanılarak İnsülinin Bakır ve Alkali Metal Komplekslerinin Konformasyonel Farklılıklarının Analizi

Molecular recognition, protein folding, and formation of supramolecular structures that occur at the molecular level of biological processes are based on noncovalent interactions. Interactions between metal atoms and proteins are based on noncovalent interactions that underlie the mechanisms involved in many cellular processes. The activities of enzymes are highly dependent on the interactions of such protein groups with cofactors, substrates, metal ions, and other proteins. The compositions and binding stoichiometry of protein-metal complexes can be determined with high accuracy performing mass spectrometry (MS) analysis. The conformational features of protein-metal complexes can be studied additionally using a mass spectrometer with ion mobility spectrometry (IMS) capability. This study focuses the monitoring the differences in the conformational changes of insulin protein during the formation of its complex with copper and alkali metals using trapped ion mobility spectrometry – time-of-flight (TIMS–TOF) mass spectrometer instrument. The compaction of the insulin structure by the formation of the insulin-copper complexes in the gas phase was determined with TIMS-TOF-MS analyses. However, no change was observed in the insulin structure with the addition of H, Na, and K atoms as adducts at the same analysis conditions.

Rational synthesis of elusive organic-inorganic hybrid metal-oxo clusters: formation and post-functionalization of hexavanadates.

Paving the way towards new functional materials relies increasingly on the challenging task of forming organic-inorganic hybrid compounds. In that regard, discrete atomically-precise metal-oxo nanoclusters have received increasing attention due to the wide range of organic moieties that can be grafted onto them through functionalization reactions. The Lindqvist hexavanadate family of clusters, such as [V6O13{(OCH2)3C-R}2]2- (V6-R), is particularly interesting due to the magnetic, redox, and catalytic properties of these clusters. However, compared to other metal-oxo cluster types, V6-R clusters have been less extensively explored, which is mainly due to poorly understood synthetic challenges and the limited number of viable post-functionalization strategies. In this work, we present an in-depth investigation of the factors that influence the formation of hybrid hexavanadates (V6-R HPOMs) and leverage this knowledge to develop [V6O13{(OCH2)3CNHCOCH2Cl}2]2- (V6-Cl) as a new and tunable platform for the facile formation of discrete hybrid structures based on metal-oxo clusters in relatively high yields. Moreover, we showcase the versatility of the V6-Cl platform through its post-functionalization via nucleophilic substitution with various carboxylic acids of differing complexity and with functionalities that are relevant in multiple disciplines, such as supramolecular chemistry and biochemistry. Hence, V6-Cl was shown to be a straightforward and versatile starting point for the formation of functional supramolecular structures or other hybrid materials, thereby enabling their exploration in various fields.

Syntheses, Structural Insight and HirshFeld Surface Analysis of Two Heteroleptic Coordination Polymer of Cu(II)

Using a solvothermal method, we have synthesized two coordination polymers of Cu(II). One is a 1D polymer {[Cu(bpy)(NDC)(H 2 O)].2H 2 O} n (1, 1D) formed with 1,8-naphthalene dicarboxylic acid (H 2 NDC) and 2,2′ -bipyridine (bpy) as an auxiliary ligand, while the other is a 2D polymer {[Cu 3 (TMA)(Imd) 3 ].5H 2 O.2DMF} n (2, 2D) formed with trimellitic acid (H 3TMA) and imidazole (Imd) as an auxiliary ligand. Both coordination polymers 1 and 2 were formed through an in situ hydrolytic ring opening reaction of 1,8-naphthalic anhydride and trimelitic anhydride with bipyridine and imidazole ligands, respectively. The asymmetric unit of polymer 1 contains asymmetric η 1 binding mode (one of the carboxylate) linking distorted square-pyramidal [Cu(NDC)(bpy)(H 2 O)] 2+ coordination units. The syn-syn-η 1 :η 1 linear polymer conformation exist in the 1D coordination polymer with adjacent Cu…Cu distance is 6.849Å. A chain of cyclic tetrameric water clusters is present between the stacked layers of the 3D supramolecular structure. The formation of the 3D supramolecular structure is guided by various weak interactions such as OH…O, CH…O, CH…π and π…π interactions. The coordination polymers 2 forms 3D supramolecular architecture guided by various weak interactions such as OH…O, CH…O and NH…O interactions. The crystal structures of both coordination polymers have been determined using single crystal X-ray diffraction and their structural features are described.

Dynamic responsiveness of self‐assembling peptide‐based nano‐drug systems

AbstractDynamic‐responsive self‐assembly is the process of ordered supramolecular structure formation or reversible decomposition from building blocks. This process is driven by non‐covalent interactions based on complex stimulus‐responsive systems comprising different components within a microenvironment. Furthermore, stimuli‐responsive assembly‐disassembly is an intrinsic interaction process in organisms, indispensable in maintaining life activities and functions. However, the dynamic interactions between dynamically responsive nano‐drug systems (DRNSs) and biological systems remain unpredictable, which are a challenge for the precisely targeted therapy and controlled drug release of DRNSs in vivo. This review highlights novel self‐assembling peptide‐based nano‐drug systems and their biological interactions. By precisely controlling the shape and size of self‐assembled peptide nanomaterials, biologically simulated components with diverse biological functions and precise transport at the subcellular level can be achieved. We have also summarized the limitations and challenges of responsive self‐assembling peptide nanomaterials in clinical translation. Additionally, we have discussed the future perspectives of supramolecular therapeutics using signaling molecule gradient concentrations and efficiencies and highlighted the direction for developing clinically translatable smart nanomedicines.

Structural and Thermodynamic Control of Supramolecular Polymers and DNA Assemblies with Cyanuric Acid: Influence of Substituents and Intermolecular Interactions.

Understanding the interactions and thermodynamic parameters that govern the structure and stability of supramolecular polymers is challenging because of their flexible nature and high sensitivity to weak intermolecular interactions. The application of both experimental and computational analyses reveals the role that substituents on cyanuric acid (Cy), and other nitrogen-containing heterocycles, play in the formation of novel helical supramolecular structures. In this report, we focus on how noncovalent interactions, including steric and stacking interactions, modulate the structural and physical properties of these assemblies. In-depth analyses and several examples of critical steric and electrostatic effects provide insight into the relationship between intermolecular interactions of Cy with nucleic acids and the structure and thermodynamic stability of the supramolecular polymers they form.

Bio-inspired supramolecular metallopeptide hydrogel promotes recovery from cutaneous wound

Inspired by the regulation of protein structure and function by metal ions in life, the role of metal coordination in the folding and assembly of peptides has been gradually studied. However, the construction of bioactive supramolecular metallopeptides with synergism between metal coordination and peptide self-assembly remains challenging. This paper reports a bio-inspired peptide derivative (Supra GHK (glycyl-l-histidyl-l-lysine)) bearing a natural-derived GHK tri-peptide motif, which could self-assemble into supramolecular metallopeptide hydrogel (Supra GHK-Cu) after adding Cu2+. The addition of Cu2+ prompts the allosteric effects on the folded structure of Supra GHK, resulting from the participation of atoms on the backbone of the peptide in the chelation. Cu2+ has a stronger affinity for Supra GHK by bridging two peptide molecules or interacting with one peptide molecule, as confirmed by experimental results and molecular dynamics simulation. Remarkably, due to the formation of supramolecular structures, Supra GHK-Cu possesses excellent resistance against protease degradation. Moreover, it accelerates wound healing more significantly than GHK-Cu by promoting collagen deposition, angiogenesis and cell proliferation. This work not only exemplifies a successful bio-inspired supramolecular metallopeptide hydrogel but also provides a promising alternative strategy to overcome the limitations of traditional bioactive peptides in various biomedical fields.

Substances explosive properties formation

Formation mechanisms of substances explosive properties based on the supramolecular structure prediction were studied and the appropriate analytical index was developed. The explosiveness index Kр was introduced based on the "melting ease" parameter, taking into account the equivalent length nСeq of the smallest supramolecular structure in the cluster form. The model performance was tested for the simplest explosive – nitromethane and similar compounds. It is shown that for values of the index Kр<1, combustible substances are not capable of the detonation, and for Kр>1, this index is proportional to the explosives detonation velocity. According to the presence of the explosive properties oscillation, using the example of alkanes homologous series, a connection was established with supramolecular structure features of the substance in the solid state. It is explained that such oscillation is the phenomenon consequence of molecules "evenity-oddity" in a homologous series and indicates the transition in the flame front of a substance to a solid state. It is proposed to consider the spread of the defla-gration and detonation combustion as different mechanisms of clustering in the flame front. A model is considered that for combustible substances due to the pressures in the flame front, the condensation or peroxide clustering can occur in a similar way to their clustering during the phase transition to the solid state at the melting temperature, which involves the formation of supramolecular polymer-like structures that are easier to condense under increased pressure in flame front. It has been proven that the difference between the detonation process of combustible mixtures and the detonation of explosive compounds is the need for a phase transition to a condensed state in the substance clusters form or its peroxides.

Iridium(III) and Rhodium(III) Half-Sandwich Coordination Compounds with 11H-Indeno[1,2-b]quinoxalin-11-one Oxime: A Case of Spontaneous Resolution of Rh(III) Complex

Two half-sandwich iridium(III) and rhodium(III) complexes with 11H-indeno[1,2-b]quinoxalin-11-one oxime (IQ-1) ligand were prepared by the reaction of the proligand with [M(Cp*)Cl2]2 (M = Ir, Rh) dimers. The reaction between IQ-1 and [Ir(Cp*)Cl2]2 in methanol gave the complex [Ir(Cp*)(IQ-1)Cl] (1), which crystallized in a centrosymmetric space group as a true racemate. Whereas complex [Rh(Cp*)(IQ-1)Cl] (2) in the form of a racemic conglomerate was obtained by the reaction of [Rh(Cp*)Cl2]2 and IQ-1 in methanol. The crystal structures of complexes 1 and 2 (R and S enantiomers) were determined by X-ray diffraction analysis, and the structural features were compared in order to understand the structural factors leading to the spontaneous enantiomer resolution of the rhodium(III) complex. In the crystal packing of 1, intermolecular C–H···C contacts between a pair of enantiomers link the molecules into centrosymmetric dimers and lead to the formation of heterochiral crystals of 1. In contrast, the intramolecular contacts CH···Cl and CH···C in complex 2 bind all three ligands around the chiral Rh(III) metal center. In addition, a combination of intermolecular CH···O and CH···C contacts leads to the formation of a homochiral supramolecular structure. These interactions altogether reinforce the spontaneous resolution in complex 2.

Supramolecular and theoretical investigation of copper(II) complexes containing 2,2′-bipyridine and substituted chalcone ligands: Estimation of non-covalent interactions

Copper complexes of type [Cu(L)(bpy)(NO3)] {1, L = L1; 2, L = L2; L1H= 3-(4-benzyloxyphenyl)-1-(2-hydroxylphenyl)-prop-2-en-1-one, L2H= 1-(2-hydroxyphenyl)-3-(4-chlorophenyl) prop-2-en-1-one, bpy=2,2′-bipyridine} have been synthesized and characterized using elemental analysis, spectroscopic (IR, UV–Vis) and single crystal X-ray diffraction techniques. In both complexes, Cu(II) adopts distorted square pyramidal geometry. The crystal packing of complex 1 displays an infinite 1D supramolecular architecture using C–H⋯O and π-π stacking interactions. The C–H⋯O and π⋯π interactions together with weak C–H⋯Cl interaction facilitate formation of a 2D supramolecular net like structure in complex 2. The comprehensive studies of these interactions have been made using hirshfeld surface, fingerprint plots analyses and energy frameworks. The molecular electrostatic potential (MEP) surface analysis shows the larger values of negatively charged nitrate and larger positive values at aromatic ring in both complexes. It implies that C–H⋯O and π⋯π interactions are dominant. Additionally, the combination of non-covalent interaction (NCI) plot index and QTAIM analysis computational tools are used to explore energetic features of the synthons involving different non-covalent interactions such as C–H⋯O, π⋯π and C–H⋯Cl interactions. Both analyses show that the combined π⋯π and CH⋯π interactions are dominant in the complex 1 for the dimer stabilization and construction of supramolecular structure. Whereas, complex 2 dimerization is prominently due to π⋯π interaction. The complexes 1 and 2 display emissions λmax 524 and 533 nm at λexcit 438 and 440 nm, respectively. It indicates small bathochromic shift in emission of complex 2 to complex 1 due to substituted chalcone ligands.

Penta-coordinated Cr(II) and Cu(II) complexes appended with 4′-(4-quinolyl)-2,2′:6′,2″-terpyridine: Crystal structure, Hirshfeld surface analysis, luminescence and thermal properties

Two new chromium and copper complexes containing 4′-(4-quinolyl)-2,2′:6′,2′'-terpyridine (qtpy) have been synthesized and characterized using elemental analysis, IR and X-ray crystal structure determination. The reaction of CrCl3.6H2O with qtpy in presence of granulated zinc as a reducing agent has been resulted in the formation of the new terpyridine chromium(II) complex [Cr(qtpy)Cl2] (1). Moreover, the reaction of CuBr2 with qtpy affords the new complex [Cu(qtpy)Br2] (2). Recrystallization of 1 from DMF and recrystallization of 2 from DMSO yield the respective solvates, [Cr(qtpy)Cl2].DMF (1.DMF) and [Cu(qtpy)Br2].2DMSO (2.2DMSO), confirmed by X-ray single crystal analysis. The crystal structures of isostructural complexes [Cr(qtpy)Cl2].DMF (1.DMF) and [Cu(qtpy)Br2].2DMSO (2.2DMSO) reveal that chromium(II) and copper(II) adopt the penta-coordinated square pyramidal geometry in which Cr and Cu are coordinated by three nitrogen atoms of qtpy and two Cl- for 1.DMF, and two Br- for 2.2DMSO. As well, the crystal packings of complex 1.DMF, and 2.2DMSO clearly show the formation of supramolecular structures through C-H…X (X = N, O, halide) hydrogen bond interactions. The 3D Hirshfeld surface analysis and 2D fingerprint maps were used for quantitative mapping out of the intermolecular interactions for 1.DMF, and 2.2DMSO. Luminescence properties of 1 and 2 displayed the ligand-based π–π* emission bands in solution. Thermal properties of 1 and 2 show that they undergo thermal decomposition and the corresponding metal oxide formed in each case.

Design of Acrylate-Terminated Polyurethane for Nylon Seamless Bonding Fabric Part I: Design of the End-Capping Thermoplastic Polyurethane Adhesive with Acrylate Copolymer.

This series of studies aims to design acrylate-terminated polyurethanes for use in nylon seamless bonded fabrics. The first part used N,N-dimethylacrylamide (DMAA) and methyl methacrylate (MMA) to replace the chain extender in polyurethane synthesis as end-capping agent to synthesize thermoplastic polyurethane (TPU) adhesive. The molecular weight of the TPU is controlled to further influence the mechanical and processing properties of the polyurethane. Here, polytetramethylene ether glycol (PTMG) and 4,4-methylene diphenyl diisocyanate (MDI) were polymerized, and then a blocking agent was added thereto. The results show that the characteristic peaks of benzene ring and carbamate of TPU adhesive are at 1596 cm−1 and 1413 cm−1, respectively, while the characteristic peaks of DMAA are at 1644 cm−1 and 1642 cm−1 in the FT-IR spectrum. There is an absorption peak –N=C=O– which is not shown near 2268 cm−1, which proves that the structure of TPU contains the molecular structure of capping agent, PTMG and MDI. When the DMAA concentration in the capping agent was increased from 3.0 wt% to 10 wt%, the –C=O (H-bond) area percentage of hydrogen bonds formed at 1711 cm−1 increased from 41.7% to 57.6%, while the –NH (H bond) produced at 3330 cm−1 increased from 70% to 81%. These phenomena suggest that increasing the concentration of DMAA capping agent can effectively promote the formation of complex supramolecular network structures by hydrogen bonding in TPU. The content and concentration of the capping agent affects the molecular weight of the TPU. Chain growth is terminated when molecular weight growth can be effectively controlled and reduced. It was observed in thermal analysis that with increasing DMAA concentration in the molecular structure, the concentration of capping agent in TPU, hydrogen bonding force between hard segments, melting point (Tmh) and melting enthalpy (ΔH) all increased the capping agent. The pyrolysis temperature of TPU is increased by 10–20 °C.

Modulating 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 a 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 the peptide sequence pattern, oligomer/nanodroplet morphology, and fibrillization pathway, kinetics, and structure may contribute to our understanding of pathogenic amyloidosis in aging, facilitate future efforts ameliorating amyloidosis through peptide engineering, and aid in the design of novel amyloid-based functional nanobiomaterials and nanocomposites.

Preparation of supramolecular viscoelastic polymers with shear, temperature, and salt resistance/sensitivity by amphiphilic functional monomer modification

To develop high-salinity, high-temperature reservoirs, a novel supramolecular viscoelastic polymer-based fracturing fluid modified with an amphiphilic functional monomer was developed. Investigation of the thickening ability, solubility, and rheology revealed that the as-developed gel system with a rigid hydrophobically associating space network structure and linear entanglement can improve the thickening ability, solubility, temperature adaptation range, and chemical environment resistance sensitivity of supramolecular polymers. The surface/interfacial tension test revealed that the modified polymers exhibit surface and interface activity. At an MHAP-15 concentration of 1500 mg/L, the surface tension was 39.29 Nm/m. At an MHAP-15 concentration of 800 mg/L, a minimum interfacial tension of 0.86 Nm/m was observed. The shear sensitivity test revealed that the copolymer fluid exhibits a high creep recovery performance and elastic response as well as a 100% viscosity recovery rate. In addition, the viscoelasticity and thixotropy of the copolymer solution were investigated. The results revealed that the higher the number of the oxyethylene groups in amphiphilic functional monomers, the higher the increase in the viscous modulus of the copolymer solution. In the modified polymer, the highest energy was required for the destruction of the MHAP-15 solution, reaching 66.5 Pa; this result confirmed the best synergistic effect of hydrophobic association and linear entanglement of the MHAP-15 solution molecules, as well as the best temperature and salt resistance. The viscosity of 0.6 wt% MHAP-15 was 120 mPa s after shearing for 50 min at 120 °C and at 170 s−1. At 160 °C and 100 s−1, the viscosity of the 0.8 wt% MHAP-15 polymer solution reached 153 mPa s after shearing for 50 min. At a NaCl concentration of 25 × 104 mg/L, the viscosities of the 0.6 wt% and 0.8 wt% MHAP-15 solutions were 203 and 245 mPa s, respectively, indicative of the stimulation response of salt thickening. At a CaCl2 concentration of 2 × 104 mg/L, the viscosity of 0.6 wt% MHAP-15 was 87 mPa s, and the viscosity retention rate was 47.9%. Finally, by X-ray diffraction, the particle size test in solution, and scanning electron microscopy, the higher the number of oxyethylene groups in the amphiphilic functional monomers, the higher the mixing entropy of copolymers, and the particle size in solution and multi-peak distribution were higher, as well as more clear linear entanglement between copolymers; all of these factors were conducive to the formation of large-scale supramolecular structures of super-bridged copolymers.