Formation Mechanism and Stability Study of Konjac Glucomannan Helical Structure

The formation mechanism and stability of konjac glucomannan （KGM） helical structure were investigated by molecular dynamic simulation and experimental method. The results indicate that the molecular conformation of KGM is a non-typical helical structure. In detail, helical structure of KGM is mainly sustained by acetyl group, whose size and stability are affected by the molecular polymerization degree of KGM. In vacuum among the non-bonding interactions, electrostatic force is the greatest factor affecting its helical structure, but in water solution, hydrogen bond affects the helical arrangement greatly. To our interest, temperature exhibits a reversible destroying effect to some extent; the helical structure will disappear completely and present a ruleless clew-like arrangement till 341 K. This work suggests that the method of combining molecular dynamic simulation and experiment tools can be effective in the study of KGM helical structure.

Fixation for the helical structure of a glassy cholesteric liquid crystal reflective film

The planar texture of glassy cholesteric siloxane cyclic side-chain liquid crystals was fixed by quenching initially. Then the polymer network formed by the optically active polymerizable monomers imposed additional constraints on the motion of chain segments of the glassy liquid crystal and then further stabilized the molecule arrangement. A cholesteric liquid crystal film with stable optical properties was developed by this method.

Studies on the Relationship between the Helical Structure and Optical Activity of Some Chiral Cyclic Esters Ⅱ

A method for the analysis of the relationship between the helical structure and optical activity was proposed by the study of the conformations and X-ray diffraction structures of some cyclic esters prepared by esterification of L-(-)-2.3-O-methylidene threitol and L-(+)-2,3-O-isopropplidene threitol with alkanedioyl dichlorides and o-,m-,and p-phthaloyl dichlorides.

Fatigue behaviors and damage mechanisms for Nb_(3)Sn triple-helical structure at liquid nitrogen temperature

Nb_(3)Sn triple‐helical structure is the elementary structure in the superconducting cable of ITER magnets and undergoes prolonged fatigue loading in extreme environments leading to serious damage degradation.In this paper,the fatigue behaviors of the Nb_(3)Sn triple‐helical structure have been investigated by the strain cycling fatigue experiments at liquid nitrogen temperature.The results indicate that Nb_(3)Sn triple‐helical structures with short twist‐pitches possess excellent fatigue damage resistance than that of long twist‐pitches,such as longer fatigue life,slower damage degradation,and smaller energy dissipation.Meanwhile,a theoretical model of damage evolution has been established to reveal the effects of twist‐pitches on fatigue properties for triplehelical structures,which is also validated by the present experimental data.Furthermore,one can see that the Nb_(3)Sn superconducting wires in a triple‐helical structure with the shorter twist‐pitches have a larger elongation of helical structure and less cyclic deformation,which can be considered as the main mechanism of better fatigue damage properties for the triple‐helical structures during the strain cycling processes.These findings provide a better understanding of the fatigue properties and damage mechanisms for Nb_(3)Sn triple‐helical structures in superconducting cables of ITER magnets.

Crystal Structure and Solution Behavior of a Novel Enantiopure Helical Coordination Polymer Based on Binaphthyl-bisbipyridine Ligand

An enantiopure helical coordination polymer AgPF6·（R）-3 as crystalline solid was synthesized by the self-assembly of chiral binaphthyl-based ligand（R）-6,6＇-di[6-（2,2＇-bipyridyl）]-2,2＇-diethoxyl-1,1＇-binaphthalene [（R）-3] and Ag＋ ion.The single crystal structural analysis indicates that this polymer exhibits an infinite cylindric single-stranded M-helical structure with local Λ configuration at each tetrahedral metal center.However,the extended structure is dissociated into some oligomeric fragments in solution.The 1H NMR spectra of complex AgPF6·（R）-3 show that the ligand possesses a good C2 symmetry,and the chemical shifts of the protons depend on the concentration and temperature.In addition,there are rapid dynamic exchanges among some oligonuclear fragments in the solution of AgPF6·（R）-3.

Bending Resistance and Anisotropy of Basalt Fibers Laminate Composite with Bionic Helical Structure

The appendages of mantis shrimp often bear bending loads from different directions during the in the process of preying on prey with its grazing limb.Hence,it has excellent bending resistance and isotropy to confront complex and changeable external load.The outstanding performance owes to the helical Bouligand structure with a certain interlayer corner,which is also widely found in other natural materials.Hence,the bio-inspired materials with basalt fiber are fabricated with outstanding bending resistance,isotropy and toughness.The research shows laminates with 18°interlayer corners exhibit relatively excellent bending resistance and isotropy,and the laminate with 11.25°interlayer corner has best toughness.Compared with traditional composites,average bending strength along different loading direction of bio-inspired materials increased by 28%,and anisotropy decreased by 86%.Besides,the maximum toughness of laminates can increase to 1.7 times of the original.Following the introduction of interlayer corners,the bio-inspired composite tends to be isotropic.To explore the reason for the change of the isotropic performance caused by diverse interlayer corners,the Finite Element Analysis based on classical laminate theory and Tsai–Wu and Tsai–Hill failure criterion.Besides,further experiments and observations are conducted to explore possible reasons.In conclusion,following the introduction of interlayer corners,the bio-inspired composites tend to be isotropic.This bio-inspired composites are expected to be applied to various complex modern engineering fields,such as vehicle,rail transit and aerospace.

Helical Coordination Polymer with a 3-Fold Interpenetration Structure Based on 5-(Hydroxymethyl)isophthalic Acid

5-（Hydroxymethyl） isophthalic acid （H2HIA） as a novel organic ligand was prepared from 3,5-bis（methoxycarbonyl）benzoic acid by a two-step method. And then, a 3D helical coor- dination polymer with a 3-fold interpenetration structure, namely [Zn1/2（HIA）1/2（DPEE）1/2]n （1）, was hydrothermally synthesized at 160 ℃, using H2HIA ligands to assemble with DPEE ligands and Zn2＋ ions. Complex 1 crystalizes in orthorhombic system, space group Pnna, with a = 8.2118（5）, b = 17.1698（7）, c =14.9922（7） ？, V = 2113.82（18） ？3, μ = 1.194 mm-1, Z = 4 and S = 0.967. Moreover, some physical characteristics of complex 1, such as powder X-ray diffraction （PXRD）, thermogravimetry analyses （TGA） and photoluminescent properties, were also investigated.

Synthesis, Crystal Structure and Properties of a New Cadmium Compound with(1,1？-(1,4-Butanediyl)bis(imidazole) and p-Hydroxybenzoic Acid

A new metal-organic framework based on bbi and PHBA（bbi = 1,1＇-（1, 4-butanediyl）bis（imidazole）, PHBA = p-hydroxybenzoic acid）, namely, [Cd（bbi）（PHBA）2]n（1） has been synthesized by the conventional method. Compound 1 displays a two-dimensional（2D） layer structure possessing the left-and right-handed helical chains and stabilized by intermolecular hydrogen-bonding to form a three-dimensional（3D） supramolecular structure. Topologically, the 2D layer belongs to well-known（4,4） network topology. The structure has been determined by single-crystal X-ray diffraction analyses, and further characterized by infrared spectra（IR）, elemental analyses and powder X-ray diffraction. In addition, the thermal behavior and luminescent properties of [Cd（bbi）（PHBA）2]n have been investigated in detail.

Three New Zn(Ⅱ) Coordination Compounds Based on the in-situ Formed Tetrazolate Ligand: Syntheses, Crystal Structures and Luminescence Properties

Reactions of 2-（2-benzoimidazolyl）acetonitrile and Na N3 with Zn SO4 or Zn Cl2 in the presence of nicotinic acid in the mixture of Et OH/H2 O afforded a mononuclear compound [Zn（L1）2]（1） and a 1-D polymer [Zn（L1）Cl]n（2）, respectively（L1 = 5-[（benzoimidazolyl）methyl]-1H-tetrazolate）. However, in the similar condition except that imidazole was added instead of nicotinic acid, the reaction afforded a 1-D compound [Zn（L1）2]n（3） featuring triply helical chains via the π-π stacking of ligands. They are characterized by elemental analysis and IR, and their structures have been determined by X-ray crystallography. Thermal stability of these compounds was measured by TGA and their luminescent properties were investigated at room temperature.

Helioal Structure and Optical Activity of Two New Derivatives of R(+)-1,1'-Binaphthyl-2,2'-diol

Correlation between the belieal structure and optical activity of two derivatives of R(+)- 1, 1'-binaphthyl-2,2'-diol was derived from a study of their optical rotations, CD curves and Xray crystal structures.

The atomic path for constructing single-helical superstructure of AuCu bimetallic nanoclusters

Single-helical or double-helical structures are common in living organisms.Helical assembly has been found in the artificial nanoparticles,but how they do so remains poorly understood.Here,we exploit atomically precise Au_(6)Cu_(6)bimetallic nanoparticles(or called nanoclusters)as building blocks to construct a single-helical Au_(12)Cu_(12)superstructure in an operative path,thereby providing access to currently elusive mechanistic pathways.We propose that the thermodynamically viable linearto-bent process at a couple of Au_(6)Cu_(6)nanoclusters imparted by the organic ligands seems to be critical for the helical-nanostructured arrangement of Au_(12)Cu_(12).This study could help to offer a new design rule for the exquisitely helical structure assembled from the artificial nanoparticles.

Formation Sites and Microscopic Conformation Study on the Konjac Glucomannan Molecular Helices

In this work, the formation sites, helical parameters and hydrogen bond positions of Konjac glucomannan molecular helices were investigated using molecular dynamic simulation method. To our interest, the KGM chain is mainly composed by local left and right helix struetttres. The formation sites of KGM chain might locate at the chain-segments containing acetyl groups, and the left helix is the favorable conformation of KGM. Temperature-dependent molecule conformation study indicates that the right helix is dominant when the temperature is lower than 343 K, above which, however, the left helix is dominating （right helix disappears）. In addition, intramolecular hydrogen bonds in the left helix can be found at the -OH groups on C（2）, C（4） and C（6） of mannose residues; comparably, the intramolecular hydrogen bonds in the right helix can be mainly observed at the -OH groups on C（4） and C（6） of the mannose residues and C（3） of the glucose residues. In conclusion, molecular dynamic simulation is an efficient method for the microscopic conformation study of glucomannan molecular helices.

TEXTURES OF ETHYL-ACETYL CELLULOSE MESOPHASE

There was phase separation between the anisotropic and isotropic phases in the ethyl-acetyl cellulose/dichloroacetic acid cholesteric liquid crystalline solutions .The textures of mesophase varied with the concentration. The mesophases could form the disc-like texture, oily streaks texture and texture of domains gathered randomly. In the first two textures the layers of the ordered molecular chain were perpendicular to the slide surface and the axes of the helical structure were parallel to the slide surface.

Novel 1D Copper（ll） Helical Chain Formed by Weak Coordination-driven Self-assembly： Synthesis, Structure, and Magnetic Property

A novel 1D copper（II） helical chain is constructed through the connection of tetranuclear copper（ll） units [Cu4（L）（Py）4] （H8L=N,N＇-（BINOL-3,3＇-dicarboxyl）-disalicylhydrazide, where BINOL is 1,l＇-binaphthalenyl-2,2＇- diol, py=pyridine） by weak coordination-driven self-assembly, and characterized by IR, single crystal X-ray dif- fraction, thermogravimetric analysis, and X-ray power diffraction analysis. Interestingly, the helical chains are packed in an alternating left-（M） and right-handed （P） chirality, the orientation of the helices was determined by the axial chirality of the ligand. The complex shows antiferromagnetic interactions between the copper centers.

Two Coordination Novel Polymers Based on a Flexible Ligand N,N'-diacetic Acid Imidazolium

{[Cu_3（cis-DAM）_4（OH）_2]·12H_2O}_n 1 and [Ag_3（trans-DAM）_2（NO_3）]_n 2 with a flexible ligand N,NA-diacetic acid imidazolium（HDAM） were synthesized and characterized by single-crystal X-ray diffraction. Compound 1 crystallizes in the orthorhombic I222 space group with a = 12.033（2）,b = 12.498（3）,c = 14.963（3） A,V = 2250.4（8） A^3,Z = 8,C_7H_（13.5）N_2O_（7.5）Cu_（0.75）,M_r = 293.35,D_c = 1.732 g·cm^-3,F（000） = 1210,GOF = 1.087,the final R（I 〉 2σ（I）） = 0.0521 and w R（all data） = 0.1386. Compound 2 crystallizes in the monoclinic C2/c space group with a = 21.601（4）,b = 8.321（2）,c = 13.589（3） A,β = 126.95（3）°,V = 1951.9（7） A^3,Z = 8,C_7H_7N_（2.5）O_（5.5）Ag_（1.5）,M_r = 375.96,D_c = 2.559 g·cm^-3,F（000） = 1448,GOF = 1.017,R（I 〉 2σ（I）） = 0.0222 and w R（all data） = 0.0633. Compound 1 displays a novel 2D layer,consisting of a couple of left-helical chains with a pitch of 12.498（3） A formed by μ_3-cis-DAM~– ligands and Cu（1） ions,which are stabilized by hydrogen bonding interactions to give a 3D supramolecular framework. As for 2,Ag（1） ions are doubly bridged by trans-DAM~– and NO_3~– to form [Ag（1）_2O_4] chains,which are further connected by Ag（2） and trans-DAM~– to build a 3D framework. Additionally,thermogravimetric analyses,FT-IR spectroscopy,UV-visible spectroscopy,and the fluorescent properties were discussed.

Highly sensitive torsion sensor based on Mach–Zehnder interference in helical seven-core fiber taper

We propose a high-sensitivity bidirectional torsion sensor using a helical seven-core fiber taper embedded in multimode fiber(MHSTM).Sensors with different taper waists and helical pitches are fabricated,and their transmission spectra are obtained and analyzed.The waist and length of the sandwiched seven-core fiber are finally determined to be 68 μm and3 mm,respectively.The experimental results show that the clockwise and counterclockwise torsion sensitivities of the proposed sensor are 2.253 nm/(rad/m) and-1.123 nm/(rad/m),respectively.When tapered waist diameter reduces to48 μm,a superior torsion sensitivity of 5.391 nm/(rad/m) in the range of 0-4.24 nm/(rad/m) is obtained,which is 46 times as large as the traditional helical seven-core fiber structure.In addition,the MHSTM structure is also relatively stable to temperature variations.

Spin waves and transverse domain walls driven by spin waves: Role of damping

Based on the uniform,helical and spiral domain-wall magnetic configurations,the excited spin waves are studied with emphasis on the role of damping.We find that the damping closes the gap of dispersion,and greatly influences the dispersion in the long-wave region for the spin waves of spiral wall and helical structure.For the uniform configuration,the Dzyaloshinskii-Moriya interaction determines the modification of dispersion by the damping.Furthermore,we investigate the interaction between spin waves and a moving spiral domain wall.In the presence of damping,the amplitude of spin wave can increase after running across the wall for small wave numbers.Driving by the spin waves,the wall propagates towards the spin-wave source with an increasing velocity.Unlike the case without damping,the relation between the wall velocity and the spin-wave frequency depends on the position of wall.

Syntheses, Crystal Structures and Magnetic Properties of Two New Low-dimensional Manganese (Ⅱ) Coordination Compounds

Two new low-dimensional Mn(Ⅱ)coordination compounds of Mn(H2pimdc)2(phen)(compound 1)and[Mn(Hpimdc)(phen)]n·nH2O(compound 2)were synthesized,where H3pimdc is a 2-propyl-imidazole-4,5-dicarboxylic acid and phen is 1,10-phenanthroline.Both compounds were thoroughly analyzed by X-ray single-crystal diffraction,element analysis,IR spectra,PXRD and thermal analysis.X-ray single-crystal diffraction analyses indicate that the phen ligands terminate metal ions on two sides to prevent the linkage between the neighboring metal ions into a higher dimensional structure in compounds 1 and 2.Compound 1 is constructed from mononuclear molecules which form the 1D helical supramolecular chain by N-H···O hydrogen bonds.In compound 2,Hpimdc is a tetradentate bridging ligand,which binds Mn(Ⅱ)ions to generate a single-stranded right helical chain parallel to the b axis.These 1D chains are additionally coupled by H-bonds as well asπ···πstacking interactions,which formed a 3D supramolecular structure.Additionally,compound 2 demonstrated temperature-dependent magnetic susceptibility and negative value ofθ(equal to-9.09 K),which is indicative of weak antiferromagnetic interactions between Mn(Ⅱ)ions.

α/Sulfono-γ-AA peptide hybrids agonist of GLP-1R with prolonged action both in vitro and in vivo

Peptides are increasingly important resources for biological and therapeutic development,however,their intrinsic susceptibility to proteolytic degradation represents a big hurdle.As a natural agonist for GLP-1R,glucagon-like peptide 1(GLP-1)is of significant clinical interest for the treatment of type-2 diabetes mellitus,but its in vivo instability and short half-life have largely prevented its therapeutic application.Here,we describe the rational design of a series of a/sulfono-γ-AA peptide hybrid analogues of GLP-1 as the GLP-1R agonists.Certain GLP-1 hybrid analogues exhibited enhanced stability(t_(1/2)>14 days)compared to t_(1/2)(<1 day)of GLP-1 in the blood plasma and in vivo.These newly developed peptide hybrids may be viable alternative of semaglutide for type-2 diabetes treatment.Additionally,our findings suggest that sulfono-γ-AA residues could be adopted to substitute canonical amino acids residues to improve the pharmacological activity of peptide-based drugs.

Hydrogen-bonding regulated supramolecular chirality with controllable biostability

The regulation of natural helical nanostructures is principally supported and actuated by hydrogen bonds(H-bonds)formed from hydrogen-bonding groups(peptide bonds and base pairs)to realize biological activities and specific biofunctional transformations.However,studying the role of H-bonding patterns on the handedness of supramolecular assemblies is still challenging,since supramolecular assemblies will be disassembled or destabilized with slightly varying H-bonding groups for most supramolecules.To circumvent this issue,herein,two types of self-assembled C2-symmetric phenylalanine derivatives differed by a single H-bonding group(ester or amide)are systematically designed for deciphering the role of H-bonding pattern on the chirality of supramolecular assemblies and their related biostability.Opposite handedness nanofibrous structures with tailorable diameter and helical pitch are achieved with the transition from ester to amide groups in the gelators.Experimental and theoretical evidence suggests that helical orientation of ester-containing gelators ascribes to intermolecular H-bonds.In contrast,the helical direction for the amide-counterparts is mainly due to intra-and intermolecular H-bonds.Moreover,these H-bonding groups greatly influence their stability,as revealed by in vitro and in vivo degradation experiments and the left-handed assemblies are more stable than the right-handed ones.Thus,the study offers a feasible model to have valuable insight into understanding the role of H-bonding patterns in biological folding.