Search

Basalt fiber–reinforced polymer (BFRP) is widely used to reinforce concrete due to its high strength, lightweight nature, good corrosion resistance, and low cost. Previous studies have shown that the double-helix BFRP macrofiber has better bond behavior with concrete compared with other types of BFRP fibers. This is attributed to its irregular geometry. The bond-slip behavior between double-helix BFRP macrofiber and concrete is further numerically studied in this study. The corresponding finite-element model is established, and the accuracy of the numerical method is validated by the experimental results based on fiber-matrix pullout tests. The effects of twisted pitches, bundle numbers, and cross-section shapes of the fiber on the bond-slip behavior are extensively investigated and discussed. It is shown by the numerical results that the bond stress and energy-dissipating capacity increase with the decrease of twisted pitches (30, 20, 10, and 5 mm). The bond stress of the fiber with a twisted pitch of 5 mm can be increased by 17.0% at most compared with the fiber with a twisted pitch of 30 mm. Furthermore, it is found that the double-helix BFRP fiber has higher bond stress than the fiber with three or four bundles, with corresponding increases of 11.9% and 16.9%, respectively. [ABSTRACT FROM AUTHOR]

The folding of oligomeric strands is the method that nature has selected to generate ordered assemblies presenting spectacular functions. In the purpose to mimic these biomacromolecules and extend their properties and functions, chemists make important efforts to prepare artificial secondary, tertiary, and even quarternary structures based on folded abiotic backbones. A large variety of oligomers and polymers, encoded with chemical informations, were designed, synthesized and characterized, and the establishment of non‐covalent interactions lead to complex and functional supramolecular architectures resulting from a spontaneous self‐assembly process. The association of complementary molecular strands into double helical structures is a common structural pattern of nucleic acids and proteins, so the synthesis of bio‐inspired double helices has emerged as an important subject. In recent years, a number of synthetic oligomers have been reported to form stable double helices and it was shown that the equilibrium between single and double helices can be controlled via different stimuli like the modification of the solvent or the temperature. This kind of structure presents highly interesting functions, such as molecular recognition within the cavity of double helices, and some other potential applications will emerge in the future. [ABSTRACT FROM AUTHOR]

Purine stretches, sequences of adenine (A) and guanine (G) in DNA, play critical roles in binding regulatory protein factors and influence gene expression by affecting DNA folding. This study investigates the relationship between purine stretches and cancer development, considering the aromaticity of purines, quantified by methods like Hückel's rule and NICS calculations, and the importance of the flanking sequence context. A pronounced avoidance of long purine stretches by typical cancer mutations was observed in public data on the intergenic regions of cancer patients, suggesting a role of intergenic sequences in chromatin reorganization and gene regulation. A statistically significant shortening of purine stretches in cancerous tumors (p value < 0.0001) was found. The insights into the aromatic nature of purines and their stacking energies explain the role of purine stretches in DNA structure, contributing to their role in cancer progression. This research lays the groundwork for understanding the nature of purine stretches, emphasizing their importance in gene regulation and chromatin restructuring, and offers potential avenues for novel cancer therapies and insights into cancer etiology. [ABSTRACT FROM AUTHOR]

This document provides a concise summary of an article discussing the synthesis and analysis of 5,7,8,10-tetraphenyl-1,14-dianilinotripyrrins. The study explores the structural changes and properties of these compounds in response to different environments and substituents. The article provides detailed information on the synthesis, structures, and spectroscopic analysis of the synthesized compounds. The findings suggest potential applications as near-infrared emitters and further research on the photophysical dynamics of tripyrrins is ongoing. The document also acknowledges funding support and provides access to additional supporting information online. [Extracted from the article]

Achieving high luminescence dissymmetry factors and quantum yields in the solid state remains a significant challenge in developing circularly polarized luminescence (CPL) materials. This study presents the synthesis of double helices based on planar chiral [2.2]paracyclophane ([2.2]PCP) and tetraphenylethylene (TPE), which exhibit chiroptical and aggregation‐induced emission (AIE) properties. In particular, the double helix with long alkyl chains demonstrates tunable CPL activity driven by self‐assembly, exhibiting dissymmetry factors ranging from 10−4 to 10−2. Notably, doped PMMA films show an amplified dissymmetry factor of 0.058 and a high quantum yield of up to 51%. The designed molecules represent an ideal molecular functional material for generating efficient CPL with controllable dissymmetry factor and high emission efficiency in the solid state. This opens up possibilities for applications in chiroptical sensing, data storage, and light‐emitting devices based on solid‐state materials. [ABSTRACT FROM AUTHOR]

Helices are ubiquitous in art and nature. Independent of their pitch and sense of rotation (handedness), helices in sculpture, painting, architecture, scientific illustrations, conference announcements, logos, and advertising are eye-catching and aesthetically pleasing. Helices can turn either clockwise (right-handed helix) or anti-clockwise (left-handed helix). The [Formula: see text]-helix formed by l-amino acids and the double helices formed by [Formula: see text]-d-2′-deoxyribonucleic acid (A- and B-form DNA) and [Formula: see text]-d-ribonucleic acid (A-form RNA) are all right-handed. Artistic license provides the freedom to create helices of any shape and sense; indeed, many helical sculptures do not follow the natural convention observed in proteins and DNA. What is more surprising, given that models of the [Formula: see text]-helix and the DNA double helix were published over 70 years ago, is how common left-handed DNA double helices are in the context of scientific papers and books as well as in popular science writing and reporting. In all cases except for left-handed Z-DNA, the use of left-handed helices in scientific illustrations or models is incorrect. Here, we revisit the helix types adopted by peptides, DNA, and RNA, and review examples of right and wrong helical models in science, art, and elsewhere.

Chirality is ubiquitous in nature, and homochirality is manifested in many biomolecules. Although β‐double helices are rare in peptides and proteins, they consist of alternating L‐ and D‐amino acids. No peptide double helices with homochiral amino acids have been observed. Here, we report chiral β‐double helices constructed from γ‐peptides consisting of alternating achiral (E)‐α,β‐unsaturated 4,4‐dimethyl γ‐amino acids and chiral (E)‐α,β‐unsaturated γ‐amino acids in both single crystals and in solution. The two independent strands of the same peptide intertwine to form a β‐double helix structure, and it is stabilized by inter‐strand hydrogen bonds. The peptides with chiral (E)‐α,β‐unsaturated γ‐amino acids derived from α‐L‐amino acids adopt a (P)‐β‐double helix, whereas peptides consisting of (E)‐α,β‐unsaturated γ‐amino acids derived from α‐D‐amino acids adopt an (M)‐β‐double helix conformation. The circular dichroism (CD) signature of the (P) and (M)‐β‐double helices and the stability of these peptides at higher temperatures were examined. Furthermore, ion transport studies suggested that these peptides transport ions across membranes. Even though the structural analogy suggests that these new β‐double helices are structurally different from those of the α‐peptide β‐double helices, they retain ion transport activity. The results reported here may open new avenues in the design of functional foldamers. [ABSTRACT FROM AUTHOR]

We prepared a series of water‐soluble aromatic oligoamide sequences all composed of a segment prone to form a single helix and a segment prone to dimerize into a double helix. These sequences exclusively assemble as antiparallel duplexes. The modification of the duplex inner rim by varying the nature of the substituents borne by the aromatic monomers allowed us to identify sequences that can hybridize by combining two chemically different strands, with high affinity and complete selectivity in water. X‐ray crystallography confirmed the expected antiparallel configuration of the duplexes whereas NMR spectroscopy and mass spectrometry allowed us to assess precisely the extent of the hybridization. The hybridization kinetics of the aromatic strands was shown to depend on both the nature of the substituents responsible for strand complementarity and the length of the aromatic strand. These results highlight the great potential of aromatic hetero‐duplex as a tool to construct non‐symmetrical dynamic supramolecular assemblies. [ABSTRACT FROM AUTHOR]

In 1954, the seminal short paper in the Nature from James Watson and Francis Crick proposed the double helix model of deoxyribose nucleic acid. This amateur-looking concept changed the way molecular biology is now perceived. We are now celebrating the 70 years of the phenomenon discovery of the modern science that has revolutionized life sciences with a huge impact on many other related scientific disciplines. Fifty years later, the Human Genome Project offered the nearly complete draft sequence of the human genome that is now fully sequenced in the 70th year of the double helix. Technological advances have led to a rapid reduction in the cost of whole genome sequencing. It is now possible for anyone to get the personal genome sequenced for

As a rule, helical structures at the molecular level are formed by non‐planar units. This makes the design of helices, starting from planar building blocks via self‐assembly, even more fascinating. Until now, however, this has only been achieved in rare cases, where hydrogen and halogen bonds were involved. Here, we show that the carbonyl‐tellurium interaction motif is suitable to assemble even small planar units into helical structures in solid phase. We found two different types of helices: both single and double helices, depending on the substitution pattern. In the double helix, the strands are connected by additional Te⋅⋅⋅Te chalcogen bonds. In the case of the single helix, a spontaneous enantiomeric resolution occurs in the crystal. This underlines the potential of the carbonyl‐tellurium chalcogen bond to generate complex three‐dimensional patterns. [ABSTRACT FROM AUTHOR]

In 1954, the seminal short paper in the Nature from James Watson and Francis Crick proposed the double helix model of deoxyribose nucleic acid. This amateur-looking concept changed the way molecular biology is now perceived. We are now celebrating the 70 years of the phenomenon discovery of the modern science that has revolutionized life sciences with a huge impact on many other related scientific disciplines. Fifty years later, the Human Genome Project offered the nearly complete draft sequence of the human genome that is now fully sequenced in the 70th year of the double helix. Technological advances have led to a rapid reduction in the cost of whole genome sequencing. It is now possible for anyone to get the personal genome sequenced for

We demonstrate that nucleic acid (NA) mononucleotide triphosphates (dNTPs and rNTPs), at sufficiently high concentration and low temperature in aqueous solution, can exhibit a phase transition in which chromonic columnar liquid crystal ordering spontaneously appears. Remarkably, this polymer-free state exhibits, in a self-assembly of NA monomers, the key structural elements of biological nucleic acids, including: long-ranged duplex stacking of base pairs, complementarity-dependent partitioning of molecules, and Watson-Crick selectivity, such that, among all solutions of adenosine, cytosine, guanine, and thymine NTPs and their binary mixtures, duplex columnar ordering is most stable in the A-T and C-G combinations.

Control of the association behavior by molecular design is one of the most essential benefits in artificial supramolecular systems. 1,14‐Dianilinotripyrrin has recently emerged as a novel conjugated molecule which forms a double helix in non‐polar solvents with the aid of multiple interstrand hydrogen bonding interactions. In this work, we investigated the substituent effects at the 5,10‐positions of tripyrrin on their association thermodynamics. This study illuminated two key findings; 1) electronic tuning by the para‐substituents reduce the entropic costs thereby slightly improve the association constants, and 2) ortho‐substituents force the tripyrrin core to be relatively planar, which significantly decreases the association constant due to less feasible π‐stacking. [ABSTRACT FROM AUTHOR]

We propose an axiomatic formulation of physics by avoiding paradoxes, by the “simplest” possible axioms. A previous paper deals with the general perspective, the present paper with axioms, subsequent papers with equations. We abandon forces and potentials, which have a “statistical” meaning. Electromagnetic and gravitational interactions are explained by one discrete “carrier” (Feynman graph), without Newton’s principles. A photon is composed of miniphotons (of positive parity) and anti-miniphotons (of negative parity). Phenomena occur inside a timeless β-world, where no speed is defined. Occasionally, some emp in the β-world materializes into particle/antiparticle, composed of “degraded” emp that moves at a speed less than the speed of light. Materialization is endemic inside the β- world. Matter and antimatter - in the α- and γ-world, respectively – move with regular and with reversed time arrow, and eventually annihilate into ”upgraded” emp, returning inside the β-world. Every emp sample in the α-world (matter) and in the γ-world (antimatter) - complex conjugate of each other - releases a “rubber band” of miniphotons and antiminiphotons, captured by emp samples (in the γ-world miniphotons are captured; in the α-world anti-miniphotons). The humans can detect phenomena either the α-world, or in the γ-world, compatibly with the empirical constraint. [ABSTRACT FROM AUTHOR]

Developing chiral assemblies that mimic biological secondary structures, e.g., protein β-sheet, α-helix, and DNA double helix, is a captivating goal in supramolecular chemistry. Here, we create a family of biomimetic chiral assemblies from alanine-based peptidomimetics, wherein the incorporation of N -terminal 2,1,3-benzoselenadiazole groups enables the rarely utilized chalcogen bonding as the adhesive interaction. While the alanine-based acylhydrazine molecule 1L was designed as a building unit with an extended conformation, simple derivatization of 1L affords folded unilateral N -amidothiourea 2L with one β-turn and bilateral N -amidothiourea 3L with two β-turns. This derivatization leads to the evolution of molecular assemblies from β-sheet organization ( 1L ) to single helix (α-helix mimic, 2L ) and ultimately to double helix ( 3L ), illustrating an evolutionary route relating the structures and superstructures. In the case of the double helix formed by 3L , an unexpected cis -form that brings the two β-turns into one side was observed, stabilized via the π···π interaction between two N -terminal 2,1,3-benzoselenadiazole groups. This conformation allows double-crossed N-Se···S═C chalcogen bonds to support a DNA-like P -double helix featuring intrastrand noncovalent interactions and interstrand covalent linkages, surviving in both the solid state and in dilute acetonitrile solution phase.

The transition metal pnictide CrAs exhibits superconductivity in the vicinity of a helimagnetic phase, where it has been found that the propagation vector is parallel to the c-axis and the magnetic moments lie in the a-b plane. Here we use ab initio calculations to study the magnetic interactions in the material. Mapping onto a Heisenberg Hamiltonian, we calculate the magnetic exchanges with LDA+U calculations and we unveil the origin of the magnetic frustration. Finally, we reproduce the double helix magnetic order with the propagation vector Q = (0, 0, 0.456) and we obtain the magnetic transition temperature TN through Monte Carlo simulations of the specific heat. Due to the limitations of the use of the Heisenberg Hamiltonian for itinerant magnetic systems, the theoretical TN underestimated the experimental value of the pure CrAs. However, our results are in good agreement with those found for the alloy CrAs0.5Sb0.5 belonging to the same space group, showing that our result can describe this material class. [ABSTRACT FROM AUTHOR]

After a short introduction to her life and work, we construct Rosalind Franklin’s citation environment in the sense of Howard White. This environment consists of four groups of authors related to Franklin: her co-authors, those cited by Franklin, those co-cited with Franklin, and those citing Franklin. We further found two of her articles that can be considered as suffering from delayed recognition. The article ends with a complete bibliography of Franklin. Although she never received the Nobel Prize, she most certainly was “of Nobel Class.” [ABSTRACT FROM AUTHOR]

In this paper, three tetrahedral nanocages, composed of six DNA double helix edges with all having the twist number 1, 2 or 3, have been characterized using classical molecular dynamics simulation to measure the specific structural and conformational features produced by only changing the twisting number of each double helix. The simulation result indicates that three tetrahedral cages are relatively stable and are maintained along the entire trajectory. Each double helix is more inclined to behave as a whole in the 2TD and 3TD cages than in the 1TD cage according to the cross-correlation maps for three nanocages, and also their local motions are more easily induced by the conformational variability of the thymidine linkers due to the increased flexibility of each helix. Hence, the double helices become the important factors on the structural stability of total cages with the DNA twisting number, and also give the signification contributions to the sizes of these cages conferring the larger spaces of the 2TD and 3TD cages than the 1TD cage. Our result provides an insight into which roles the double helix edges play in assembling DNA polyhedron, and also contribute to improving the loading capacity of DNA tetrahedron in drug delivery. Three tetrahedral nanocages produced by changing the twisting number of each dsDNA edge are characterized by MD simulations. The local motions of dsDNA edges are more easily induced by the conformational variations of ssDNA linkers in cages 2TD and 3TD than in cage 1TD. DNA double-helical edges play the important roles in deciding the structural stability of total nanocages as well as in amplifying their spatial capacity. [ABSTRACT FROM AUTHOR]

Basalt fiber is more cost-effective than carbon fiber and has superior mechanical and chemical properties than glass fiber. Most existing studies considered the use of micro basalt fibers in concrete matrix to reduce shrinkage and control micro cracks. However, macro fibers are often required to reinforce concrete material when large deformation and macro cracks in structural elements are of concern. Very few studies have been reported for macro Basalt Fiber Reinforced Polymer (BFRP) fibers to improve mechanical properties of concrete. The geometric characteristics of macro fibers are critical for concrete reinforcement. It is known that macro fibers with smooth surface possess poor bond strength. To enhance the bonding properties between macro BFRP fibers and concrete, in this experimental study, pullout tests on macro BFRP fibers with various geometric forms from different grades of mortar matrix were carried out. Smooth fiber, etched fiber and double-helix fiber were manufactured and evaluated. The effects of embedded length and matrix strength are also investigated through pullout behavior of single BFRP fiber. The variation of etched intervals of etched fibers on bond strength was also taken into account. It was found that the double-helix fiber outperformed other types of fibers in terms of strength utilization ratio and energy absorption capability. An empirical model for interfacial bond-slip relation was proposed based on the test results. Based on results of pullout tests, the outstanding performance of double-helix BFRP fiber was further verified by examining the mechanical properties of normal-strength concrete specimens reinforced with different types of macro BFRP fibers. [ABSTRACT FROM AUTHOR]

To better understand the electrochemical behavior of deoxyribonucleic acid (DNA) on carbon electrodes, the oxidation of synthetic oligonucleotides of 4 to 72 nucleotides long, their thermally stable duplexes, polymerase chain reaction amplicons of 141 base pairs long, and samples of double- and single-stranded DNA (dsDNA and ssDNA) of natural origin was studied on carbon screen printed electrodes by square wave and cycling voltammetry within the potential range of 0.5–1.5 V (vs. Ag/AgCl). In square wave voltammograms, ssDNA of natural origin produced two distinct signals at approximately 0.75 V and 1.05 V (at the nucleotide concentration of 1 mM; phosphate buffer, pH 7.4), attributed to the oxidation of guanine (Gua) and adenine (Ade) residues, respectively. The oxidation reactions of both residues of ssDNA were found diffusion-controlled. Similar to that, synthetic DNA oligonucleotides exhibited the oxidation peaks at potentials of either around 0.85 V or 1.15 V (at the nucleotide concentration of 1 mM), or both, depending on their sequence. In contrast to ssDNA, dsDNA molecules showed no sign of oxidation on carbon electrodes. The low molecular weight ssDNA fragments were found as the main contributors to the overall electrooxidation currents generated via oxidation of Gua and Ade residues of DNA from a natural source. Oxidation signals of Gua and Ade residues exponentially decreased with the oligonucleotide length. In the thermally stable duplex DNA molecules even as short as those of 24 base pairs long, Gua and Ade restudies were shown to be inaccessible for oxidation on carbon electrodes.

In the late 1860s, DNA was first identified by the Swiss physician and biochemist Friedrich Miescher. Since this time, we have solved its structure, learned how DNA divides in our cells, and elucidated molecular mechanisms for the transmission of our hereditary information. Fundamental to all these discoveries is the ability to extract our DNA in high purity. In laboratories today, DNA extraction is a routine practice performed from readily available commercial kits. However, in the late 1800s, DNA extraction was an emerging method that required tedious laboratory approaches.

A chiral urea compound, N,N'-bis(4-(3,4,5-trialkoxyphenylmethyl)phenyl)urea (1a), possessing a long core and six chiral alkyl chains ((S)-citronellyl groups) was designed to construct a double helix supramolecular structure in a liquid crystal phase. As a result, the urea compounds exhibited a hexagonal columnar liquid crystal phase, and the molecules were self-organised into a double helix structure by intermolecular interactions (dipole-dipole interactions, hydrogen bonds, and π-π interactions). Furthermore, the compound's responsive behaviour to an applied external electric field was investigated, and its phase transition behaviour, column alignment, columnar structures, and electro-responsiveness were compared with those of an achiral urea compound (1b) possessing six n-decyl groups to investigate the effect on introducing the chirality. These results indicated that higher-order structures such as double helices are effective in suppressing thermal motion and delaying polarisation relaxation. [ABSTRACT FROM AUTHOR]

The mathematics of DNA molecules is often studied as a double helix model. This paper focuses on the modelling of infinitesimal bending of DNA helices. The paper checks the flexibility of DNA molecule, i.e. the flexibility of double helix in infinitesimal bending theory. Actually, first, we find infinitesimal bending field of an arbitrary curve on the helicoid, that leaves bent curves on the helicoid, and show that helix bending on the helicoid is not possible. Finally, we deal with the infinitesimal bending of helicoid, using PDEs. Visualization of infinitesimal bending was done in Mathematica. [ABSTRACT FROM AUTHOR]

In this study, we design and synthesize double helix hollow nanotube polyaniline (DHPANI) using C18-L glutamic acid as a template. Then, DHPANI is acted as the substrate, and Pt@DHPANI nanocomposites are well prepared by using potassium chloroplatinate as the Pt source and formaldehyde as the reducing agent through adsorption reduction. Characterization results indicate that Pt@DHPANI nanocomposites have excellent and stable double helix morphology, and the hollow diameter is about 20 nm, which greatly increases the specific surface area of the polyaniline. Moreover, Pt nanoparticles (NPs) with an average particle size of about 50 nm are distributed on the surface of nanocomposites. Furthermore, it is found that the interaction between Pt NPs and DHPANI greatly increases, which makes the electron delocalization enhanced, causing more difficult for Pt NPs to lose/release electrons. In the catalytic reduction process of 4-NP, the catalytic efficiency of Pt@DHPANI nanocomposites is twice as much as Pt@PANI nanocomposites, showing excellent and stable catalytic performance. [ABSTRACT FROM AUTHOR]

The article offers information on sentiment analysis a lens for viewing chemistry narratives. Topics include the book was The Double Helix the then published reflections of one of the codiscoverers of the structure of DNA, and the few single-storeyed buildings on the street also had a link with the double helix story.

A novel model system for characterization of double helix in starch is developed using branched dextrin (BD) purified from Nägeli amylodextrin by repeated precipitation in 10% ethanol. The solution of one‐time precipitated BD (BD1, 3% in water) starts to develop turbidity in 8 h of incubation at 4 °C. Volume particle size distribution during the association of four‐time precipitated BD sample (BD4) is analyzed using dynamic light scattering. The mean diameter of the particles jumps from 3.8 to 170 nm between 2 and 2.5 h of incubation, suggesting a prerequisite lag time for maturation of intermolecular association of BD4. Flakes of BD4 in water exhibit a B‐type crystal by X‐ray diffraction analysis. A screening system of additives affecting turbidity development of BD1 in water is applied for 82 compounds, and sodium tetraborate (borax) significantly retards the development. Borax affects the rate of turbidity development and maximum turbidity at the plateau stage in a concentration‐dependent manner. Borax is also added to rice starch gel, which reduces the increase of hardness of the gel during retrogradation. This novel assay system with BD can be used for screening and evaluation of additives affecting starch gelation and retrogradation. [ABSTRACT FROM AUTHOR]

• Analyze long-range and short-range molecular order fully using a series of methods. • Direct comparisons of HHGS and HGS at similar gelatinization degrees were conducted. • The ordered structure of HHGS was close-packaged during HHP treatments. • HHP simultaneously induced annealing and partial gelatinization until a certain DG. This study mainly aimed to investigate the influents of high hydrostatic pressure (HHP) on the ordered structures of starch, for this purpose, we compared the ordered structure of rice starch treated by HHP and heat, including long- and short-range ordered structures and thermodynamic properties at similar levels of gelatinization degree (DG). X-ray diffractometer, Fourier transform infrared spectrometer (FTIR), 13C cross polarization magic angle spinning/NMR, and Differential scanning calorimeter were used to detect crystal structure, band height ratio in FTIR spectra (R), double helix structure, and thermodynamic behavior. Results showed that HHP-treated rice starch (HHGS) had greater crystallinity, larger R, and more double helix and V-type single helix structures as compared to heat-treated rice starch (HGS) at a similar DG. The thermodynamic analysis illustrated that T o of HHGS was lower as compared to HGS. The ordered structure of HHGS was close packaged. HHP simultaneously induced annealing and pressure-induced gelatinization until achieving a certain degree of gelatinization. [ABSTRACT FROM AUTHOR]

This year marks 70 years since the discovery of DNA, and this poem "DNA" is an attempt to make the general audience aware of the basic features of this macromolecule. [ABSTRACT FROM AUTHOR]