Chirality Differentiation by Diffusion in Chiral Nematic Liquid Crystals

NASA Astrophysics Data System (ADS)

Jiang, Jinghua; Yang, Deng-Ke

2017-01-01

Chirality is of great importance in the living world. It helps differentiate biochemical reactions such as those that take place during digestion. It may also help differentiate physical processes such as diffusion. Aiming to study the latter effect, we investigate the diffusion of guest chiral molecules in chiral nematic (cholesteric) liquid-crystal hosts. We discover that the diffusion dramatically depends on the handedness of the guest and host molecules and the chiral differentiation is greatly enhanced by the proper alignment of the liquid-crystal host. The diffusion of a guest chiral molecule in a chiral host with the same handedness is much faster than in a chiral host with opposite handedness. We also observe that the differentiation of chirality depends on the diffusion direction with respect to the twisting direction (helical axis). These results might be important in understanding effects of chirality on physical processes that take place in biological organisms. In addition, this effect could be utilized for enantiomer separation.

Photoexcitation circular dichroism in chiral molecules

NASA Astrophysics Data System (ADS)

Beaulieu, S.; Comby, A.; Descamps, D.; Fabre, B.; Garcia, G. A.; Géneaux, R.; Harvey, A. G.; Légaré, F.; Mašín, Z.; Nahon, L.; Ordonez, A. F.; Petit, S.; Pons, B.; Mairesse, Y.; Smirnova, O.; Blanchet, V.

2018-05-01

Chiral effects appear in a wide variety of natural phenomena and are of fundamental importance in science, from particle physics to metamaterials. The standard technique of chiral discrimination—photoabsorption circular dichroism—relies on the magnetic properties of a chiral medium and yields an extremely weak chiral response. Here, we propose and demonstrate an orders of magnitude more sensitive type of circular dichroism in neutral molecules: photoexcitation circular dichroism. This technique does not rely on weak magnetic effects, but takes advantage of the coherent helical motion of bound electrons excited by ultrashort circularly polarized light. It results in an ultrafast chiral response and the efficient excitation of a macroscopic chiral density in an initially isotropic ensemble of randomly oriented chiral molecules. We probe this excitation using linearly polarized laser pulses, without the aid of further chiral interactions. Our time-resolved study of vibronic chiral dynamics opens a way to the efficient initiation, control and monitoring of chiral chemical change in neutral molecules at the level of electrons.

Cell Chirality Drives Left-Right Asymmetric Morphogenesis.

PubMed

Inaki, Mikiko; Sasamura, Takeshi; Matsuno, Kenji

2018-01-01

Most macromolecules found in cells are chiral, meaning that they cannot be superimposed onto their mirror image. However, cells themselves can also be chiral, a subject that has received little attention until very recently. In our studies on the mechanisms of left-right (LR) asymmetric development in Drosophila , we discovered that cells can have an intrinsic chirality to their structure, and that this "cell chirality" is generally responsible for the LR asymmetric development of certain organs in this species. The actin cytoskeleton plays important roles in the formation of cell chirality. In addition, Myosin31DF ( Myo31DF ), which encodes Drosophila Myosin ID, was identified as a molecular switch for cell chirality. In other invertebrate species, including snails and Caenorhabditis elegans , chirality of the blastomeres, another type of cell chirality, determines the LR asymmetry of structures in the body. Thus, chirality at the cellular level may broadly contribute to LR asymmetric development in various invertebrate species. Recently, cell chirality was also reported for various vertebrate cultured cells, and studies suggested that cell chirality is evolutionarily conserved, including the essential role of the actin cytoskeleton. Although the biological roles of cell chirality in vertebrates remain unknown, it may control LR asymmetric development or other morphogenetic events. The investigation of cell chirality has just begun, and this new field should provide valuable new insights in biology and medicine.

Cell chirality: its origin and roles in left–right asymmetric development

PubMed Central

Inaki, Mikiko; Liu, Jingyang

2016-01-01

An item is chiral if it cannot be superimposed on its mirror image. Most biological molecules are chiral. The homochirality of amino acids ensures that proteins are chiral, which is essential for their functions. Chirality also occurs at the whole-cell level, which was first studied mostly in ciliates, single-celled protozoans. Ciliates show chirality in their cortical structures, which is not determined by genetics, but by ‘cortical inheritance’. These studies suggested that molecular chirality directs whole-cell chirality. Intriguingly, chirality in cellular structures and functions is also found in metazoans. In Drosophila, intrinsic cell chirality is observed in various left–right (LR) asymmetric tissues, and appears to be responsible for their LR asymmetric morphogenesis. In other invertebrates, such as snails and Caenorhabditis elegans, blastomere chirality is responsible for subsequent LR asymmetric development. Various cultured cells of vertebrates also show intrinsic chirality in their cellular behaviours and intracellular structural dynamics. Thus, cell chirality may be a general property of eukaryotic cells. In Drosophila, cell chirality drives the LR asymmetric development of individual organs, without establishing the LR axis of the whole embryo. Considering that organ-intrinsic LR asymmetry is also reported in vertebrates, this mechanism may contribute to LR asymmetric development across phyla. This article is part of the themed issue ‘Provocative questions in left–right asymmetry’. PMID:27821533

Cell chirality: its origin and roles in left-right asymmetric development.

PubMed

Inaki, Mikiko; Liu, Jingyang; Matsuno, Kenji

2016-12-19

An item is chiral if it cannot be superimposed on its mirror image. Most biological molecules are chiral. The homochirality of amino acids ensures that proteins are chiral, which is essential for their functions. Chirality also occurs at the whole-cell level, which was first studied mostly in ciliates, single-celled protozoans. Ciliates show chirality in their cortical structures, which is not determined by genetics, but by 'cortical inheritance'. These studies suggested that molecular chirality directs whole-cell chirality. Intriguingly, chirality in cellular structures and functions is also found in metazoans. In Drosophila, intrinsic cell chirality is observed in various left-right (LR) asymmetric tissues, and appears to be responsible for their LR asymmetric morphogenesis. In other invertebrates, such as snails and Caenorhabditis elegans, blastomere chirality is responsible for subsequent LR asymmetric development. Various cultured cells of vertebrates also show intrinsic chirality in their cellular behaviours and intracellular structural dynamics. Thus, cell chirality may be a general property of eukaryotic cells. In Drosophila, cell chirality drives the LR asymmetric development of individual organs, without establishing the LR axis of the whole embryo. Considering that organ-intrinsic LR asymmetry is also reported in vertebrates, this mechanism may contribute to LR asymmetric development across phyla.This article is part of the themed issue 'Provocative questions in left-right asymmetry'. © 2016 The Authors.

Selectively transporting small chiral particles with circularly polarized Airy beams.

PubMed

Lu, Wanli; Chen, Huajin; Guo, Sandong; Liu, Shiyang; Lin, Zhifang

2018-05-01

Based on the full wave simulation, we demonstrate that a circularly polarized vector Airy beam can selectively transport small chiral particles along a curved trajectory via the chirality-tailored optical forces. The transverse optical forces can draw the chiral particles with different particle chirality towards or away from the intensity maxima of the beam, leading to the selective trapping in the transverse plane. The transversely trapped chiral particles are then accelerated along a curved trajectory of the Airy beam by the chirality-tailored longitudinal scattering force, rendering an alternative way to sort and/or transport chiral particles with specified helicity. Finally, the underlying physics of the chirality induced transverse trap and de-trap phenomena are examined by the analytical theory within the dipole approximation.

Silver Films with Hierarchical Chirality.

PubMed

Ma, Liguo; Cao, Yuanyuan; Duan, Yingying; Han, Lu; Che, Shunai

2017-07-17

Physical fabrication of chiral metallic films usually results in singular or large-sized chirality, restricting the optical asymmetric responses to long electromagnetic wavelengths. The chiral molecule-induced formation of silver films prepared chemically on a copper substrate through a redox reaction is presented. Three levels of chirality were identified: primary twisted nanoflakes with atomic crystal lattices, secondary helical stacking of these nanoflakes to form nanoplates, and tertiary micrometer-sized circinates consisting of chiral arranged nanoplates. The chiral Ag films exhibited multiple plasmonic absorption- and scattering-based optical activities at UV/Vis wavelengths based on their hierarchical chirality. The Ag films showed chiral selectivity for amino acids in catalytic electrochemical reactions, which originated from their primary atomic crystal lattices. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Maltodextrins as chiral selectors in CE: molecular structure effect of basic chiral compounds on the enantioseparation.

PubMed

Tabani, Hadi; Fakhari, Ali Reza; Nojavan, Saeed

2014-10-01

Prediction of chiral separation for a compound using a chiral selector is an interesting and debatable work. For this purpose, in this study 23 chiral basic drugs with different chemical structures were selected as model solutes and the influence of their chemical structures on the enantioseparation in the presence of maltodextrin (MD) as chiral selector was investigated. For chiral separation, a 100-mM phosphate buffer solution (pH 3.0) containing 10% (w/v) MD with dextrose equivalent (DE) of 4-7 as chiral selector at the temperature of 25°C and voltage of 20 kV was used. Under this condition, baseline separation was achieved for nine chiral compounds and partial separation was obtained for another six chiral compounds while no enantioseparation was obtained for the remaining eight compounds. The results showed that the existence of at least two aromatic rings or cycloalkanes and an oxygen or nitrogen atom or -CN group directly bonded to the chiral center are necessary for baseline separation. With the obtained results in this study, chiral separation of a chiral compound can be estimated with MD-modified capillary electrophoresis before analysis. This prediction will minimize the number of preliminary experiments required to resolve enantiomers and will save time and cost. © 2014 Wiley Periodicals, Inc.

Switching chiral solitons for algebraic operation of topological quaternary digits

NASA Astrophysics Data System (ADS)

Kim, Tae-Hwan; Cheon, Sangmo; Yeom, Han Woong

2017-02-01

Chiral objects can be found throughout nature; in condensed matter chiral objects are often excited states protected by a system's topology. The use of chiral topological excitations to carry information has been demonstrated, where the information is robust against external perturbations. For instance, reading, writing, and transfer of binary information have been demonstrated with chiral topological excitations in magnetic systems, skyrmions, for spintronic devices. The next step is logic or algebraic operations of such topological bits. Here, we show experimentally the switching between chiral topological excitations or chiral solitons of different chirality in a one-dimensional electronic system with Z4 topological symmetry. We found that a fast-moving achiral soliton merges with chiral solitons to switch their handedness. This can lead to the realization of algebraic operation of Z4 topological charges. Chiral solitons could be a platform for storage and operation of robust topological multi-digit information.

Chirality-controlled crystallization via screw dislocations.

PubMed

Sung, Baeckkyoung; de la Cotte, Alexis; Grelet, Eric

2018-04-11

Chirality plays an important role in science from enantiomeric separation in chemistry to chiral plasmonics in nanotechnology. However, the understanding of chirality amplification from chiral building blocks to ordered helical superstructures remains a challenge. Here, we demonstrate that topological defects, such as screw dislocations, can drive the chirality transfer from particle to supramolecular structure level during the crystallization process. By using a model system of chiral particles, which enables direct imaging of single particle incorporation into growing crystals, we show that the crystallization kinetic pathway is the key parameter for monitoring, via the defects, the chirality amplification of the crystalline structures from racemic to predominantly homohelical. We provide an explanation based on the interplay between geometrical frustration, racemization induced by thermal fluctuations, and particle chirality. Our results demonstrate that screw dislocations not only promote the growth, but also control the chiral morphology and therefore the functionality of crystalline states.

Influence of Chirality in Ordered Block Copolymer Phases

NASA Astrophysics Data System (ADS)

Prasad, Ishan; Grason, Gregory

2015-03-01

Block copolymers are known to assemble into rich spectrum of ordered phases, with many complex phases driven by asymmetry in copolymer architecture. Despite decades of study, the influence of intrinsic chirality on equilibrium mesophase assembly of block copolymers is not well understood and largely unexplored. Self-consistent field theory has played a major role in prediction of physical properties of polymeric systems. Only recently, a polar orientational self-consistent field (oSCF) approach was adopted to model chiral BCP having a thermodynamic preference for cholesteric ordering in chiral segments. We implement oSCF theory for chiral nematic copolymers, where segment orientations are characterized by quadrupolar chiral interactions, and focus our study on the thermodynamic stability of bi-continuous network morphologies, and the transfer of molecular chirality to mesoscale chirality of networks. Unique photonic properties observed in butterfly wings have been attributed to presence of chiral single-gyroid networks, this has made it an attractive target for chiral metamaterial design.

Chiral permselectivity in surface-modified nanoporous opal films.

PubMed

Cichelli, Julie; Zharov, Ilya

2006-06-28

Nanoporous 7 mum thin opal films comprising 35 layers of 200 nm diameter SiO2 spheres were assembled on Pt electrodes and modified with chiral selector moieties on the silica surface. Diffusion of chiral redox species through the opals was studied by cyclic voltammetry. The chiral opal films demonstrate high selectivity for transport of one enantiomer over the other. This chiral permselectivity is attributed to the surface-facilitated transport utilizing noncovalent interactions between the chiral permeant molecules and surface-bound chiral selectors.

Chiral filtration-induced spin/valley polarization in silicene line defects

NASA Astrophysics Data System (ADS)

Ren, Chongdan; Zhou, Benhu; Sun, Minglei; Wang, Sake; Li, Yunfang; Tian, Hongyu; Lu, Weitao

2018-06-01

The spin/valley polarization in silicene with extended line defects is investigated according to the chiral filtration mechanism. It is shown that the inner-built quantum Hall pseudo-edge states with identical chirality can serve as a chiral filter with a weak magnetic field and that the transmission process is restrained/strengthened for chiral states with reversed/identical chirality. With two parallel line defects, which act as natural chiral filtration, the filter effect is greatly enhanced, and 100% spin/valley polarization can be achieved.

Chiral magnetic effect without chirality source in asymmetric Weyl semimetals

NASA Astrophysics Data System (ADS)

Kharzeev, Dmitri E.; Kikuchi, Yuta; Meyer, René

2018-05-01

We describe a new type of the chiral magnetic effect (CME) that should occur in Weyl semimetals (WSMs) with an asymmetry in the dispersion relations of the left- and right-handed (LH and RH) chiral Weyl fermions. In such materials, time-dependent pumping of electrons from a non-chiral external source can generate a non-vanishing chiral chemical potential. This is due to the different capacities of the LH and RH chiral Weyl cones arising from the difference in the density of states in the LH and RH cones. The chiral chemical potential then generates, via the chiral anomaly, a current along the direction of an applied magnetic field even in the absence of an external electric field. The source of chirality imbalance in this new setup is thus due to the band structure of the system and the presence of (non-chiral) electron source, and not due to the parallel electric and magnetic fields. We illustrate the effect by an argument based on the effective field theory, and by the chiral kinetic theory calculation for a rotationally invariant WSM with different Fermi velocities in the left and right chiral Weyl cones; we also consider the case of a WSM with Weyl nodes at different energies. We argue that this effect is generically present in WSMs with different dispersion relations for LH and RH chiral Weyl cones, such as SrSi2 recently predicted as a WSM with broken inversion and mirror symmetries, as long as the chiral relaxation time is much longer than the transport scattering time.

Nanoscale chirality in metal and semiconductor nanoparticles

PubMed Central

Thomas, K. George

2016-01-01

The field of chirality has recently seen a rejuvenation due to the observation of chirality in inorganic nanomaterials. The advancements in understanding the origin of nanoscale chirality and the potential applications of chiroptical nanomaterials in the areas of optics, catalysis and biosensing, among others, have opened up new avenues toward new concepts and design of novel materials. In this article, we review the concept of nanoscale chirality in metal nanoclusters and semiconductor quantum dots, then focus on recent experimental and theoretical advances in chiral metal nanoparticles and plasmonic chirality. Selected examples of potential applications and an outlook on the research on chiral nanomaterials are additionally provided. PMID:27752651

Nanoscale chirality in metal and semiconductor nanoparticles.

PubMed

Kumar, Jatish; Thomas, K George; Liz-Marzán, Luis M

2016-10-18

The field of chirality has recently seen a rejuvenation due to the observation of chirality in inorganic nanomaterials. The advancements in understanding the origin of nanoscale chirality and the potential applications of chiroptical nanomaterials in the areas of optics, catalysis and biosensing, among others, have opened up new avenues toward new concepts and design of novel materials. In this article, we review the concept of nanoscale chirality in metal nanoclusters and semiconductor quantum dots, then focus on recent experimental and theoretical advances in chiral metal nanoparticles and plasmonic chirality. Selected examples of potential applications and an outlook on the research on chiral nanomaterials are additionally provided.

A chiroptical switch based on supramolecular chirality transfer through alkyl chain entanglement and dynamic covalent bonding.

PubMed

Lv, Kai; Qin, Long; Wang, Xiufeng; Zhang, Li; Liu, Minghua

2013-12-14

Chirality transfer is an interesting phenomenon in Nature, which represents an important step to understand the evolution of chiral bias and the amplification of the chirality. In this paper, we report the chirality transfer via the entanglement of the alkyl chains between chiral gelator molecules and achiral amphiphilic Schiff base. We have found that although an achiral Schiff base amphiphile could not form organogels in any kind of organic solvents, it formed co-organogels when mixed with a chiral gelator molecule. Interestingly, the chirality of the gelator molecules was transferred to the Schiff base chromophore in the mixed co-gels and there was a maximum mixing ratio for the chirality transfer. Furthermore, the supramolecular chirality was also produced based on a dynamic covalent chemistry of an imine formed by the reaction between an aldehyde and an amine. Such a covalent bond of imine was formed reversibly depending on the pH variation. When the covalent bond was formed the chirality transfer occurred, when it was destroyed, the transfer stopped. Thus, a supramolecular chiroptical switch is obtained based on supramolecular chirality transfer and dynamic covalent chemistry.

Chemical synthesis of water-soluble, chiral conducting-polymer complexes

DOEpatents

Wang, Hsing-Lin; McCarthy, Patrick A.; Yang, Sze Cheng

2003-01-01

The template-guided synthesis of water-soluble, chiral conducting polymer complexes is described. Synthesis of water-soluble polyaniline complexes is achieved by carefully controlling the experimental parameters such as; acid concentration, ionic strength, monomer/template ratio, total reagent concentration, and order of reagent addition. Chiral (helical) polyaniline complexes can be synthesized by addition of a chiral inducing agent (chiral acid) prior to polymerization, and the polyaniline helix can be controlled by the addition of the (+) or (-) form of the chiral acid. Moreover the quantity of chiral acid and the salt content has a significant impact on the degree of chirality in the final polymer complexes. The polyaniline and the template have been found to be mixed at the molecular level which results in chiral complexes that are robust through repeated doping and dedoping cycles.

Significant Enhancement of the Chiral Correlation Length in Nematic Liquid Crystals by Gold Nanoparticle Surfaces Featuring Axially Chiral Binaphthyl Ligands.

PubMed

Mori, Taizo; Sharma, Anshul; Hegmann, Torsten

2016-01-26

Chirality is a fundamental scientific concept best described by the absence of mirror symmetry and the inability to superimpose an object onto its mirror image by translation and rotation. Chirality is expressed at almost all molecular levels, from single molecules to supramolecular systems, and present virtually everywhere in nature. Here, to explore how chirality propagates from a chiral nanoscale surface, we study gold nanoparticles functionalized with axially chiral binaphthyl molecules. In particular, we synthesized three enantiomeric pairs of chiral ligand-capped gold nanoparticles differing in size, curvature, and ligand density to tune the chirality transfer from nanoscale solid surfaces to a bulk anisotropic liquid crystal medium. Ultimately, we are examining how far the chirality from a nanoparticle surface reaches into a bulk material. Circular dichroism spectra of the gold nanoparticles decorated with binaphthyl thiols confirmed that the binaphthyl moieties form a cisoid conformation in isotropic organic solvents. In the chiral nematic liquid crystal phase, induced by dispersing the gold nanoparticles into an achiral anisotropic nematic liquid crystal solvent, the binaphthyl moieties on the nanoparticle surface form a transoid conformation as determined by imaging the helical twist direction of the induced cholesteric phase. This suggests that the ligand density on the nanoscale metal surfaces provides a dynamic space to alter and adjust the helicity of binaphthyl derivatives in response to the ordering of the surrounding medium. The helical pitch values of the induced chiral nematic phase were determined, and the helical twisting power (HTP) of the chiral gold nanoparticles calculated to elucidate the chirality transfer efficiency of the binaphthyl ligand capped gold nanoparticles. Remarkably, the HTP increases with increasing diameter of the particles, that is, the efficiency of the chirality transfer of the binaphthyl units bound to the nanoparticle surface is diminished as the size of the particle is reduced. However, in comparison to the free ligands, per chiral molecule all tested gold nanoparticles induce helical distortions in a 10- to 50-fold larger number of liquid crystal host molecules surrounding each particle, indicating a significantly enhanced chiral correlation length. We propose that both the helicity and the chirality transfer efficiency of axially chiral binaphthyl derivatives can be controlled at metal nanoparticle surfaces by adjusting the particle size and curvature as well as the number and density of the chiral ligands to ultimately measure and tune the chiral correlation length.

Homochiral Evolution in Self-Assembled Chiral Polymers and Block Copolymers.

PubMed

Wen, Tao; Wang, Hsiao-Fang; Li, Ming-Chia; Ho, Rong-Ming

2017-04-18

The significance of chirality transfer is not only involved in biological systems, such as the origin of homochiral structures in life but also in man-made chemicals and materials. How the chiral bias transfers from molecular level (molecular chirality) to helical chain (conformational chirality) and then to helical superstructure or phase (hierarchical chirality) from self-assembly is vital for the chemical and biological processes in nature, such as communication, replication, and enzyme catalysis. In this Account, we summarize the methodologies for the examination of homochiral evolution at different length scales based on our recent studies with respect to the self-assembly of chiral polymers and chiral block copolymers (BCPs*). A helical (H*) phase to distinguish its P622 symmetry from that of normal hexagonally packed cylinder phase was discovered in the self-assembly of BCPs* due to the chirality effect on BCP self-assembly. Enantiomeric polylactide-containing BCPs*, polystyrene-b-poly(l-lactide) (PS-PLLA) and polystyrene-b-poly(d-lactide) (PS-PDLA), were synthesized for the examination of homochiral evolution. The optical activity (molecular chirality) of constituted chiral repeating unit in the chiral polylactide is detected by electronic circular dichroism (ECD) whereas the conformational chirality of helical polylactide chain can be explicitly determined by vibrational circular dichroism (VCD). The H* phases of the self-assembled polylactide-containing BCPs* can be directly visualized by 3D transmission electron microscopy (3D TEM) technique at which the handedness (hierarchical chirality) of the helical nanostructure is thus determined. The results from the ECD, VCD, and 3D TEM for the investigated chirality at different length scales suggest the homochiral evolution in the self-assembly of the BCPs*. For chiral polylactides, twisted lamellae in crystalline banded spherulite can be formed by dense packing scheme and effective interactions upon helical chains from self-assembly. The handedness of the twisted lamella can be determined by using rotation experiment of polarized light microscopy (PLM). Similar to the self-assembly of BCPs*, the examined results suggest the homochiral evolution in the crystallized chiral polylactides. The results presented in this Account demonstrate the notable progress in the spectral and morphological determination for the examination of molecular, conformational, and hierarchical chirality in self-assembled twisted superstructures of chiral polymers and helical phases of block copolymers and suggest the attainability of homochiral evolution in the self-assembly of chiral homopolymers and BCPs*. The suggested methodologies for the understanding of the mechanisms of the chirality transfer at different length scales provide the approaches to give Supporting Information for disclosing the mysteries of the homochiral evolution from molecular level.

Spin Chirality of Cu3 and V3 Nanomagnets. 1. Rotation Behavior of Vector Chirality, Scalar Chirality, and Magnetization in the Rotating Magnetic Field, Magnetochiral Correlations.

PubMed

Belinsky, Moisey I

2016-05-02

The rotation behavior of the vector chirality κ, scalar chirality χ, and magnetization M in the rotating magnetic field H1 is considered for the V3 and Cu3 nanomagnets, in which the Dzialoshinsky-Moriya coupling is active. The polar rotation of the field H1 of the given strength H1 results in the energy spectrum characterized by different vector and scalar chiralities in the ground and excited states. The magnetochiral correlations between the vector and scalar chiralities, energy, and magnetization in the rotating field were considered. Under the uniform polar rotation of the field H1, the ground-state chirality vector κI performs sawtooth oscillations and the magnetization vector MI performs the sawtooth oscillating rotation that is accompanied by the correlated transformation of the scalar chirality χI. This demonstrates the magnetochiral effect of the joint rotation behavior and simultaneous frustrations of the spin chiralities and magnetization in the rotating field, which are governed by the correlation between the chiralities and magnetization.

Timoshenko beam model for chiral materials

NASA Astrophysics Data System (ADS)

Ma, T. Y.; Wang, Y. N.; Yuan, L.; Wang, J. S.; Qin, Q. H.

2017-12-01

Natural and artificial chiral materials such as deoxyribonucleic acid (DNA), chromatin fibers, flagellar filaments, chiral nanotubes, and chiral lattice materials widely exist. Due to the chirality of intricately helical or twisted microstructures, such materials hold great promise for use in diverse applications in smart sensors and actuators, force probes in biomedical engineering, structural elements for absorption of microwaves and elastic waves, etc. In this paper, a Timoshenko beam model for chiral materials is developed based on noncentrosymmetric micropolar elasticity theory. The governing equations and boundary conditions for a chiral beam problem are derived using the variational method and Hamilton's principle. The static bending and free vibration problem of a chiral beam are investigated using the proposed model. It is found that chirality can significantly affect the mechanical behavior of beams, making materials more flexible compared with nonchiral counterparts, inducing coupled twisting deformation, relatively larger deflection, and lower natural frequency. This study is helpful not only for understanding the mechanical behavior of chiral materials such as DNA and chromatin fibers and characterizing their mechanical properties, but also for the design of hierarchically structured chiral materials.

Timoshenko beam model for chiral materials

NASA Astrophysics Data System (ADS)

Ma, T. Y.; Wang, Y. N.; Yuan, L.; Wang, J. S.; Qin, Q. H.

2018-06-01

Natural and artificial chiral materials such as deoxyribonucleic acid (DNA), chromatin fibers, flagellar filaments, chiral nanotubes, and chiral lattice materials widely exist. Due to the chirality of intricately helical or twisted microstructures, such materials hold great promise for use in diverse applications in smart sensors and actuators, force probes in biomedical engineering, structural elements for absorption of microwaves and elastic waves, etc. In this paper, a Timoshenko beam model for chiral materials is developed based on noncentrosymmetric micropolar elasticity theory. The governing equations and boundary conditions for a chiral beam problem are derived using the variational method and Hamilton's principle. The static bending and free vibration problem of a chiral beam are investigated using the proposed model. It is found that chirality can significantly affect the mechanical behavior of beams, making materials more flexible compared with nonchiral counterparts, inducing coupled twisting deformation, relatively larger deflection, and lower natural frequency. This study is helpful not only for understanding the mechanical behavior of chiral materials such as DNA and chromatin fibers and characterizing their mechanical properties, but also for the design of hierarchically structured chiral materials.

Some recent experimental results related to nuclear chirality

NASA Astrophysics Data System (ADS)

Timár, J.; Kuti, I.; Sohler, D.; Starosta, K.; Koike, T.; Paul, E. S.

2014-09-01

Detailed band structures of three chiral-candidate nuclei, 134Pr, 132La and 103Rh have been studied. The aim of the study was twofold. First, to try to explore the reasons behind the contradiction between the theoretically predicted chirality in these nuclei and the recently observed fingerprints that suggest non-chiral interpretation for the previous chiral candidate band doublets. Second, to search for multiple chiral bands of different types in these nuclei. In 134Pr a new πh11/2vh11/2 band has been observed besides the previously known chiral-candidate πh11/2vh11/2 doublet. This new band and the yrare πh11/2vh11/2 band show the expected features of a chiral doublet structure. This fact combined with the observed similarity between the band structures of 134Pr and 132La suggests that chirality might exist in these nuclei. The detailed study of the 103Rh band structure resulted in the observation of two new chiral-doublet looking structures besides the previously known one. This is indicative of possible existence of multiple chiral doublet structure in this nucleus.

An efficient and highly stereoselective synthesis of new P-chiral 1,5-diphosphanylferrocene ligands and their use in enantioselective hydrogenation.

PubMed

Chen, Weiping; Roberts, J Stanley M; Whittall, John; Steiner, Alexander

2006-07-21

An efficient and highly stereoselective synthesis of P-chiral 1,5-diphosphanylferrocene ligands has been developed, and the introduction of P-chirality in ferrocene-based phosphine ligands enhances the enantioselective discrimination produced by the corresponding catalyst when matching of the planar chirality, the chirality at carbon and the chirality at phosphorus occurs.

Cell Chirality Drives Left-Right Asymmetric Morphogenesis

PubMed Central

Inaki, Mikiko; Sasamura, Takeshi; Matsuno, Kenji

2018-01-01

Most macromolecules found in cells are chiral, meaning that they cannot be superimposed onto their mirror image. However, cells themselves can also be chiral, a subject that has received little attention until very recently. In our studies on the mechanisms of left-right (LR) asymmetric development in Drosophila, we discovered that cells can have an intrinsic chirality to their structure, and that this “cell chirality” is generally responsible for the LR asymmetric development of certain organs in this species. The actin cytoskeleton plays important roles in the formation of cell chirality. In addition, Myosin31DF (Myo31DF), which encodes Drosophila Myosin ID, was identified as a molecular switch for cell chirality. In other invertebrate species, including snails and Caenorhabditis elegans, chirality of the blastomeres, another type of cell chirality, determines the LR asymmetry of structures in the body. Thus, chirality at the cellular level may broadly contribute to LR asymmetric development in various invertebrate species. Recently, cell chirality was also reported for various vertebrate cultured cells, and studies suggested that cell chirality is evolutionarily conserved, including the essential role of the actin cytoskeleton. Although the biological roles of cell chirality in vertebrates remain unknown, it may control LR asymmetric development or other morphogenetic events. The investigation of cell chirality has just begun, and this new field should provide valuable new insights in biology and medicine. PMID:29666795

FATE AND EFFECTS OF THE ENANTIOMERS OF CHIRAL ENVIRONMENTAL POLLUTANTS

EPA Science Inventory

Enantiomers, the mirror image isomers of chiral compounds, are known to be selective in their interaction with other chiral molecules, including enzymes and other biochemicals. This holds true for pesticides, about 25% of which are chiral molecules, and other chiral environmental...

Chiral magnetic effect in lattice QCD with a chiral chemical potential.

PubMed

Yamamoto, Arata

2011-07-15

We perform a first lattice QCD simulation including a two-flavor dynamical fermion with a chiral chemical potential. Because the chiral chemical potential gives rise to no sign problem, we can exactly analyze a chirally imbalanced QCD matter by Monte Carlo simulation. By applying an external magnetic field to this system, we obtain a finite induced current along the magnetic field, which corresponds to the chiral magnetic effect. The obtained induced current is proportional to the magnetic field and to the chiral chemical potential, which is consistent with an analytical prediction.

[Influence of mobile phase composition on chiral separation of organic selenium racemates].

PubMed

Han, Xiao-qian; Qi, Bang-feng; Dun, Hui-juan; Zhu, Xin-yi; Na, Peng-jun; Jiang, Sheng-xiang; Chen, Li-ren

2002-05-01

The chiral separation of some chiral compounds with similar structure on the cellulose tris (3,5-dimethylphenylcarbamate) chiral stationary phase prepared by us was obtained. Ternary mobile phases influencing chiral recognition were investigated. A mode of interaction between the structural character of samples and chiral stationary phase is discussed. The results indicated that the retention and chiral separation of the analytes had a bigger change with minute addition of alcohols or acetonitrile as modifier in n-hexane/2-propanol (80/20, volume ratio) binary mobile phase.

A very simple, highly stereoselective and modular synthesis of ferrocene-based P-chiral phosphine ligands.

PubMed

Chen, Weiping; Mbafor, William; Roberts, Stanley M; Whittall, John

2006-03-29

A very simple, highly stereoselective and modular synthesis of ferrocene-based P-chiral phosphine ligands has been developed. On the basis of this new methodology, several new families of ferrocene-based phosphine ligands have been prepared coupling chirality at phosphorus with other, more standard stereogenic features. The introduction of P-chirality into ferrocene-based phosphine ligands enhances the enantioselective discrimination produced by the corresponding Rh catalyst when a matching among the planar chirality, carbon chirality, and the chirality of phosphorus is achieved.

A web site for calculating the degree of chirality.

PubMed

Zayit, Amir; Pinsky, Mark; Elgavi, Hadassah; Dryzun, Chaim; Avnir, David

2011-01-01

The web site, http://www.csm.huji.ac.il/, uses the Continuous Chirality Measure to evaluate quantitatively the degree of chirality of a molecule, a structure, a fragment. The value of this measure ranges from zero, the molecule is achiral, to higher values (the upper limit is 100); the higher the chirality value, the more chiral the molecule is. The measure is based on the distance between the chiral molecule and the nearest structure that is achiral. Questions such as the following can be addressed: by how much is one molecule more chiral than the other? how does chirality change along conformational motions? is there a correlation between chirality and enantioselectivity in a series of molecules? Both elementary and advanced features are offered. Related calculation options are the symmetry measures and shape measures. Copyright © 2009 Wiley-Liss, Inc.

Thermal chiral vortical and magnetic waves: New excitation modes in chiral fluids

DOE PAGES

Kalaydzhyan, Tigran; Murchikova, Elena

2017-03-24

In certain circumstances, chiral (parity-violating) medium can be described hydrodynamically as a chiral fluid with microscopic quantum anomalies. Possible examples of such systems include strongly coupled quark–gluon plasma, liquid helium 3He-A, neutron stars and the Early Universe. Here, we study first-order hy-drodynamics of a chiral fluid on a vortex background and in an external magnetic field. We show that there are two previously undiscovered modes describing heat waves propagating along the vortex and magnetic field. We call them the Thermal Chiral Vortical Wave and Thermal Chiral Magnetic Wave. We also identify known gapless excitations of density (chiral vortical and chiralmore » magnetic waves) and transverse velocity (chiral Alfvén wave). We also demonstrate that the velocity of the chiral vortical wave is zero, when the full hydrodynamic framework is applied, and hence the wave is absent and the excitation reduces to the charge diffusion mode. We also comment on the frame-dependent contributions to the obtained propagation velocities.« less

Spin-Selective Transmission and Devisable Chirality in Two-Layer Metasurfaces.

PubMed

Li, Zhancheng; Liu, Wenwei; Cheng, Hua; Chen, Shuqi; Tian, Jianguo

2017-08-15

Chirality is a nearly ubiquitous natural phenomenon. Its minute presence in most naturally occurring materials makes it incredibly difficult to detect. Recent advances in metasurfaces indicate that they exhibit devisable chirality in novel forms; this finding offers an effective opening for studying chirality and its features in such nanostructures. These metasurfaces display vast possibilities for highly sensitive chirality discrimination in biological and chemical systems. Here, we show that two-layer metasurfaces based on twisted nanorods can generate giant spin-selective transmission and support engineered chirality in the near-infrared region. Two designed metasurfaces with opposite spin-selective transmission are proposed for treatment as enantiomers and can be used widely for spin selection and enhanced chiral sensing. Specifically, we demonstrate that the chirality in these proposed metasurfaces can be adjusted effectively by simply changing the orientation angle between the twisted nanorods. Our results offer simple and straightforward rules for chirality engineering in metasurfaces and suggest intriguing possibilities for the applications of such metasurfaces in spin optics and chiral sensing.

Biomarkers of Oxidative Stress in the Assessment of Enantioselective Toxicity of Chiral Pesticides.

PubMed

Ye, Xiaoqing; Liu, Ying; Li, Feixue

2017-01-01

In biological systems, the individual stereoisomers of chiral substances possess significantly different biochemical properties because the specific structure-activity relationships are required for a common site on biomolecules. In the past decade, there has been increasing concern over the enantioselective toxicity of environmental chiral pollutants, especially chiral pesticides. Different responses and activities of a pair of enantiomers of chiral pesticides were often observed. Therefore, assessment of the enantioselective toxicological properties of chiral pesticides is a prerequisite in application of single-isomer products and particularly important for environmental protection. The development of biomarkers that can predict enantioselective effects from chiral pesticides has recently been gained more and more attention. The biomarkers of oxidative stress have become a topic of significant interest for toxic assessments. In this review, we summarized current knowledge and advances in the understanding of enantiomeric oxidative processes in biological systems in response to chiral pesticides. The consistent results in two types of chiral insecticides (synthetic pyrethroids and organochlorine pesticides) showed the significant difference in cytotoxicity of enantiomers, suggesting the antioxidant enzymes are reliable biomarkers for the assessment of toxicity of chiral chemicals. Results indicate that antioxidant enzymes are sensitive and valid biomarkers to assess the oxidative damage caused by chiral herbicides. In addition, it can be inferred that the enantioselectivity of chiral herbicides on antioxidant enzymes exists in other species. Compared with insecticides and herbicides, researches about the enantioselectivity of oxidative stress caused by chiral fungicides are quite limited. Only two kinds of chiral fungicides has been used to study the enantioselectivity of oxidative stress by now. The current knowledge that enantioselective processes of oxidative damage occur in organisms or cells extends toxicological studies of environmental contamination by chiral chemicals. These studies indicate that oxidative biomarkers can be useful for monitoring enantioselective toxicity of chiral contaminates, while comparing enantiomer-induced responses in different species should be approached with caution because of differences in uptake, target sites, biotransformation and pharmacokinetics of the enantiomers.

Conjugated Gammadion Chiral Metamaterial with Uniaxial Optical Activity and Negative Refractive Index

DTIC Science & Technology

2011-01-10

in Fig. 4, we discuss a procedure of transmutation from the simple -particle chiral element to the conjugated gammadion chiral metamaterial. The...the transmutation from the simple -particle chiral element to the conjugated gammadion chiral metamaterial. The procedure shows how the magnetic or

Enantiomer analysis of chiral carboxylic acids by AIE molecules bearing optically pure aminol groups.

PubMed

Zheng, Yan-Song; Hu, Yu-Jian; Li, Dong-Mi; Chen, Yi-Chang

2010-01-15

Pure enantiomers of carboxylic acids are a class of important biomolecules, chiral drugs, chiral reagents, etc. Analysis of the enantiomers usually needs expensive instrument or complex chiral receptors. However, to develop simple and reliable methods for the enantiomer analysis of acids is difficult. In this paper, chiral recognition of 2,3-dibenzoyltartaric acid and mandelic acid was first carried out by aggregation-induced emission molecules bearing optically pure aminol group, which was easily synthesized. The chiral recognition is not only seen by naked eyes but also measured by fluorophotometer. The difference of fluorescence intensity between the two enantiomers of the acids aroused by the aggregation-induced emission molecules was up to 598. The chiral recognition could be applied to quantitative analysis of enantiomer content of chiral acids. More chiral AIE amines need to be developed for enantiomer analysis of more carboxylic acids.

Chiral ionic liquids in chromatographic and electrophoretic separations.

PubMed

Kapnissi-Christodoulou, Constantina P; Stavrou, Ioannis J; Mavroudi, Maria C

2014-10-10

This report provides an overview of the application of chiral ionic liquids (CILs) in separation technology, and particularly in capillary electrophoresis and both gas and liquid chromatography. There is a large number of CILs that have been synthesized and designed as chiral agents. However, only a few have successfully been applied in separation technology. Even though this application of CILs is still in its early stages, the scientific interest is increasing dramatically. This article is focused on the use of CILs as chiral selectors, background electrolyte additives, chiral ligands and chiral stationary phases in electrophoretic and chromatographic techniques. Different examples of CILs, which contain either a chiral cation, a chiral anion or both, are presented in this review article, and their major advantages along with their potential applications in chiral electrophoretic and chromatographic recognition are discussed. Copyright © 2014 Elsevier B.V. All rights reserved.

Chiral photonic crystal fibers with single mode and single polarization

NASA Astrophysics Data System (ADS)

Li, She; Li, Junqing

2015-12-01

Chiral photonic crystal fiber (PCF) with a solid core is numerically investigated by a modified chiral plane-wave expansion method. The effects of structural parameters and chirality strength are analyzed on single-polarization single-mode range and polarization states of guided modes. The simulation demonstrates that the chiral photonic crystal fiber compared to its achiral counterpart possesses another single-circular-polarization operation range, which is located in the short-wavelength region. The original single-polarization operation range in the long-wavelength region extends to the short wavelength caused by introducing chirality. Then this range becomes a broadened one with elliptical polarization from linear polarization. With increase of chirality, the two single-polarization single-mode ranges may fuse together. By optimizing the structure, an ultra-wide single-circular-polarization operation range from 0.5 μm to 1.67 μm for chiral PCF can be realized with moderate chirality strength.

Tailoring the chirality of light emission with spherical Si-based antennas.

PubMed

Zambrana-Puyalto, Xavier; Bonod, Nicolas

2016-05-21

Chirality of light is of fundamental importance in several enabling technologies with growing applications in life sciences, chemistry and photodetection. Recently, some attention has been focused on chiral quantum emitters. Consequently, optical antennas which are able to tailor the chirality of light emission are needed. Spherical nanoresonators such as colloids are of particular interest to design optical antennas since they can be synthesized at a large scale and they exhibit good optical properties. Here, we show that these colloids can be used to tailor the chirality of a chiral emitter. To this purpose, we derive an analytic formalism to model the interaction between a chiral emitter and a spherical resonator. We then compare the performances of metallic and dielectric spherical antennas to tailor the chirality of light emission. It is seen that, due to their strong electric dipolar response, metallic spherical nanoparticles spoil the chirality of light emission by yielding achiral fields. In contrast, thanks to the combined excitation of electric and magnetic modes, dielectric Si-based particles feature the ability to inhibit or to boost the chirality of light emission. Finally, it is shown that dual modes in dielectric antennas preserve the chirality of light emission.

Chiral magnetic microspheres purified by centrifugal field flow fractionation and microspheres magnetic chiral chromatography for benzoin racemate separation

PubMed Central

Tian, Ailin; Qi, Jing; Liu, Yating; Wang, Fengkang; Ito, Yoichiro; Wei, Yun

2013-01-01

Separation of enantiomers still remains a challenge due to their identical physical and chemical properties in a chiral environment, and the research on specific chiral selector along with separation techniques continues to be conducted to resolve individual enantiomers. In our laboratory the promising magnetic chiral microspheres Fe3O4@SiO2@cellulose-2, 3-bis (3, 5-dimethylphenylcarbamate) have been developed to facilitate the resolution using both its magnetic property and chiral recognition ability. In our present studies this magnetic chiral selector was first purified by centrifuge field flow fractionation, and then used to separate benzoin racemate by a chromatographic method. Uniform-sized and masking-impurity-removed magnetic chiral selector was first obtained by field flow fractionation with ethanol through a spiral column mounted on the type-J planetary centrifuge, and using the purified magnetic chiral selector, the final chromatographic separation of benzoin racemate was successfully performed by eluting with ethanol through a coiled tube (wound around the cylindrical magnet to retain the magnetic chiral selector as a stationary phase) submerged in dry ice. In addition, an external magnetic field facilitates the recycling of the magnetic chiral selector. PMID:23891368

Molecular-Level Design of Heterogeneous Chiral Catalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Francisco Zaera

2012-03-21

The following is a proposal to continue our multi-institutional research on heterogeneous chiral catalysis. Our team combines the use of surface-sensitive analytical techniques for the characterization of model systems with quantum and statistical mechanical calculations to interpret experimental data and guide the design of future research. Our investigation focuses on the interrelation among the three main mechanisms by which enantioselectivity can be bestowed to heterogeneous catalysts, namely: (1) by templating chirality via the adsorption of chiral supramolecular assemblies, (2) by using chiral modifiers capable of forming chiral complexes with the reactant and force enantioselective surface reactions, and (3) by formingmore » naturally chiral surfaces using imprinting chiral agents. Individually, the members of our team are leaders in these various aspects of chiral catalysis, but the present program provides the vehicle to generate and exploit the synergies necessary to address the problem in a comprehensive manner. Our initial work has advanced the methodology needed for these studies, including an enantioselective titration procedure to identify surface chiral sites, infrared spectroscopy in situ at the interface between gases or liquids and solids to mimic realistic catalytic conditions, and DFT and Monte Carlo algorithms to simulate and understand chirality on surfaces. The next step, to be funded by the monies requested in this proposal, is to apply those methods to specific problems in chiral catalysis, including the identification of the requirements for the formation of supramolecular surface structures with enantioselective behavior, the search for better molecules to probe the chiral nature of the modified surfaces, the exploration of the transition from supramolecular to one-to-one chiral modification, the correlation of the adsorption characteristics of one-to-one chiral modifiers with their physical properties, in particular with their configuration, and the development of ways to imprint chiral centers on achiral solid surfaces. Chiral catalysis is not only a problem of great importance in its own right, but also the ultimate test of how to control selectivity in catalysis. The time is ripe for fundamental work in heterogeneous chiral catalysis to provide the U.S. with a leadership role in developing the next generation of catalytic processes for medicinal and agrochemical manufacturing. Our team provides the required expertise for a synergistic and comprehensive integration of physical and chemical experimentation with solid state and molecular reactivity theories to solve this problem.« less

Induction of Chirality in Two-Dimensional Nanomaterials: Chiral 2D MoS2 Nanostructures.

PubMed

Purcell-Milton, Finn; McKenna, Robert; Brennan, Lorcan J; Cullen, Conor P; Guillemeney, Lilian; Tepliakov, Nikita V; Baimuratov, Anvar S; Rukhlenko, Ivan D; Perova, Tatiana S; Duesberg, Georg S; Baranov, Alexander V; Fedorov, Anatoly V; Gun'ko, Yurii K

2018-02-27

Two-dimensional (2D) nanomaterials have been intensively investigated due to their interesting properties and range of potential applications. Although most research has focused on graphene, atomic layered transition metal dichalcogenides (TMDs) and particularly MoS 2 have gathered much deserved attention recently. Here, we report the induction of chirality into 2D chiral nanomaterials by carrying out liquid exfoliation of MoS 2 in the presence of chiral ligands (cysteine and penicillamine) in water. This processing resulted in exfoliated chiral 2D MoS 2 nanosheets showing strong circular dichroism signals, which were far past the onset of the original chiral ligand signals. Using theoretical modeling, we demonstrated that the chiral nature of MoS 2 nanosheets is related to the presence of chiral ligands causing preferential folding of the MoS 2 sheets. There was an excellent match between the theoretically calculated and experimental spectra. We believe that, due to their high aspect ratio planar morphology, chiral 2D nanomaterials could offer great opportunities for the development of chiroptical sensors, materials, and devices for valleytronics and other potential applications. In addition, chirality plays a key role in many chemical and biological systems, with chiral molecules and materials critical for the further development of biopharmaceuticals and fine chemicals, and this research therefore should have a strong impact on relevant areas of science and technology such as nanobiotechnology, nanomedicine, and nanotoxicology.

Enantioselectively controlled release of chiral drug (metoprolol) using chiral mesoporous silica materials

NASA Astrophysics Data System (ADS)

Guo, Zhen; Du, Yu; Liu, Xianbin; Ng, Siu-Choon; Chen, Yuan; Yang, Yanhui

2010-04-01

Chiral porous materials have attracted burgeoning attention on account of their potential applications in many areas, such as enantioseparation, chiral catalysis, chemical sensors and drug delivery. In this report, chiral mesoporous silica (CMS) materials with various pore sizes and structures were prepared using conventional achiral templates (other than chiral surfactant) and a chiral cobalt complex as co-template. The synthesized CMS materials were characterized by x-ray diffraction, nitrogen physisorption, scanning electron microscope and transmission electron microscope. These CMS materials, as carriers, were demonstrated to be able to control the enantioselective release of a representative chiral drug (metoprolol). The release kinetics, as modeled by the power law equation, suggested that the release profiles of metoprolol were remarkably dependent on the pore diameter and pore structure of CMS materials. More importantly, R- and S-enantiomers of metoprolol exhibited different release kinetics on CMS compared to the corresponding achiral mesoporous silica (ACMS), attributable to the existence of local chirality on the pore wall surface of CMS materials. The chirality of CMS materials on a molecular level was further substantiated by vibrational circular dichroism measurements.

Five chiral Cd(II) complexes with dual chiral components: Effect of positional isomerism, luminescence and SHG response

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Lin, E-mail: lcheng@seu.edu.cn; Jiangsu Province Hi-Tech Key Laboratory for Bio-medical Research, Southeast University, Nanjing 211189; Wang, Jun

2015-01-15

Five chiral Cd(II) complexes with dual chiral components have been synthesized by using a series of (1R,2R)–N{sup 1},N{sup 2}-bis(pyridinylmethyl)cyclohexane-1,2-diamine ligands with different N-positions of pyridyl rings and Cd(NO{sub 3}){sub 2}. The circular dichroism (CD) spectra and second-harmonic generation (SHG) efficiency measurements confirmed that they are of structural chirality in the bulk samples. The luminescent properties indicated that they may have potential applications as optical materials. The formation of discrete mononuclear and binuclear complexes, and one-dimensional chains may be attributed to positional isomerism of the ligands. - Graphical abstract: Five chiral Cd(II) complexes with dual chiral components have been synthesized bymore » using a series of chiral ligands with different N-positions of pyridyl rings. - Highlights: • Five chiral Cd(II) complexes with dual chiral components have been synthesized. • CD spectra and SHG efficiency of the bulk samples have been measured. • The complexes display luminescent properties.« less

Chirality and energy transfer amplified circularly polarized luminescence in composite nanohelix

PubMed Central

Yang, Dong; Duan, Pengfei; Zhang, Li; Liu, Minghua

2017-01-01

Transfer of both chirality and energy information plays an important role in biological systems. Here we show a chiral donor π-gelator and assembled it with an achiral π-acceptor to see how chirality and energy can be transferred in a composite donor–acceptor system. It is found that the individual chiral gelator can self-assemble into nanohelix. In the presence of the achiral acceptor, the self-assembly can also proceed and lead to the formation of the composite nanohelix. In the composite nanohelix, an energy transfer is realized. Interestingly, in the composite nanohelix, the achiral acceptor can both capture the supramolecular chirality and collect the circularly polarized energy from the chiral donor, showing both supramolecular chirality and energy transfer amplified circularly polarized luminescence (ETACPL). PMID:28585538

Chirality and energy transfer amplified circularly polarized luminescence in composite nanohelix

NASA Astrophysics Data System (ADS)

Yang, Dong; Duan, Pengfei; Zhang, Li; Liu, Minghua

2017-06-01

Transfer of both chirality and energy information plays an important role in biological systems. Here we show a chiral donor π-gelator and assembled it with an achiral π-acceptor to see how chirality and energy can be transferred in a composite donor-acceptor system. It is found that the individual chiral gelator can self-assemble into nanohelix. In the presence of the achiral acceptor, the self-assembly can also proceed and lead to the formation of the composite nanohelix. In the composite nanohelix, an energy transfer is realized. Interestingly, in the composite nanohelix, the achiral acceptor can both capture the supramolecular chirality and collect the circularly polarized energy from the chiral donor, showing both supramolecular chirality and energy transfer amplified circularly polarized luminescence (ETACPL).

Tunable Chiroptical Properties from the Plasmonic Band to Metal-Ligand Charge Transfer Band of the Cysteine Capped Molybdenum Oxide Nanoparticles.

PubMed

Li, Yiwen; Cheng, Jiaji; Li, Jiagen; Zhu, Xi; He, TingChao; Chen, Rui; Tang, Zikang

2018-06-25

Understanding the interactions between a semiconducting nanocrystal surface and chiral anchoring molecules could resolve the mechanism of chirality induction in nanoscale and facilitate the rational design of chiral semiconducting materials for chiroptics. Herein, we present chiral molybdenum oxide nanoparticles in which chirality is transferred via a bio-to-nano approach. With facile controlling on the amount of chiral cysteine molecules under redox treatment, circular dichroism (CD) signals are generated in plasmon region and metal-ligand charge transfer band. The obtained enhanced CD signals with tunable line-shapes illustrate the possibility of using chiral molybdenum oxide nanoparticles as potentials for chiral semiconductor nanosensors, optoelectronics and photocatalysts. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chirality in molecular collision dynamics

NASA Astrophysics Data System (ADS)

Lombardi, Andrea; Palazzetti, Federico

2018-02-01

Chirality is a phenomenon that permeates the natural world, with implications for atomic and molecular physics, for fundamental forces and for the mechanisms at the origin of the early evolution of life and biomolecular homochirality. The manifestations of chirality in chemistry and biochemistry are numerous, the striking ones being chiral recognition and asymmetric synthesis with important applications in molecular sciences and in industrial and pharmaceutical chemistry. Chiral discrimination phenomena, due to the existence of two enantiomeric forms, very well known in the case of interaction with light, but still nearly disregarded in molecular collision studies. Here we review some ideas and recent advances about the role of chirality in molecular collisions, designing and illustrating molecular beam experiments for the demonstration of chiral effects and suggesting a scenario for a stereo-directional origin of chiral selection.

Field redefinitions and Plebanski formalism for GR

NASA Astrophysics Data System (ADS)

Krasnov, Kirill

2018-07-01

We point out that there exists a family of transformations acting on BF-type Lagrangians of gravity, with Lagrangians related by such a transformation corresponding to classically equivalent theories. A transformation of this type corresponds to a particular field redefinition. We discuss both the chiral and non-chiral cases. In the chiral case there is a one-parameter, and in the non-chiral case a two-parameter family of such transformations. In the chiral setup, we use these transformations to give an alternative derivation of the chiral BF plus potential formulation of general relativity that was proposed recently. In the non-chiral case, we show that there is a new BF plus potential type formulation of GR. We also make some remarks on the non-chiral pure connection formulation.

Chiral discrimination of α-hydroxy acids and N-Ts-α-amino acids induced by tetraaza macrocyclic chiral solvating agents by using 1H NMR spectroscopy.

PubMed

Lv, Caixia; Feng, Lei; Zhao, Hongmei; Wang, Guo; Stavropoulos, Pericles; Ai, Lin

2017-02-21

In the field of chiral recognition, reported chiral discrimination by 1 H NMR spectroscopy has mainly focused on various chiral analytes with a single chiral center, regarded as standard chiral substrates to evaluate the chiral discriminating abilities of a chiral auxiliary. Among them, chiral α-hydroxy acids, α-amino acids and their derivatives are chiral organic molecules involved in a wide variety of biological processes, and also play an important role in the area of preparation of pharmaceuticals, as they are part of the synthetic process in the production of chiral drug intermediates and protein-based drugs. In this paper, several α-hydroxy acids and N-Ts-α-amino acids were used to evaluate the chiral discriminating abilities of tetraaza macrocyclic chiral solvating agents (TAMCSAs) 1a-1d by 1 H NMR spectroscopy. The results indicate that α-hydroxy acids and N-Ts-α-amino acids were successfully discriminated in the presence of TAMCSAs 1a-1d by 1 H NMR spectroscopy in most cases. The enantiomers of the α-hydroxy acids and N-Ts-α-amino acids were assigned based on the change of integration of the 1 H NMR signals of the corresponding protons. The enantiomeric excesses (ee) of N-Ts-α-amino acids 11 with different optical compositions were calculated based on the integration of the 1 H NMR signals of the CH 3 protons (Ts group) of the enantiomers of (R)- and (S)-11 in the presence of TAMCSA 1b. At the same time, the possible chiral discriminating behaviors have been discussed by means of the Job plots of (±)-2 with TAMCSAs 1b and proposed theoretical models of the enantiomers of 2 and 6 with TAMCSA 1a, respectively.

Deep-Subwavelength Resolving and Manipulating of Hidden Chirality in Achiral Nanostructures.

PubMed

Zu, Shuai; Han, Tianyang; Jiang, Meiling; Lin, Feng; Zhu, Xing; Fang, Zheyu

2018-04-24

The chiral state of light plays a vital role in light-matter interactions and the consequent revolution of nanophotonic devices and advanced modern chiroptics. As the light-matter interaction goes into the nano- and quantum world, numerous chiroptical technologies and quantum devices require precise knowledge of chiral electromagnetic modes and chiral radiative local density of states (LDOS) distributions in detail, which directly determine the chiral light-matter interaction for applications such as chiral light detection and emission. With classical optical techniques failing to directly measure the chiral radiative LDOS, deep-subwavelength imaging and control of circular polarization (CP) light associated phenomena are introduced into the agenda. Here, we simultaneously reveal the hidden chiral electromagnetic mode and acquire its chiral radiative LDOS distribution of a single symmetric nanostructure at the deep-subwavelength scale by using CP-resolved cathodoluminescence (CL) microscopy. The chirality of the symmetric nanostructure under normally incident light excitation, resulting from the interference between the symmetric and antisymmetric modes of the V-shaped nanoantenna, is hidden in the near field with a giant chiral distribution (∼99%) at the arm-ends, which enables the circularly polarized CL emission from the radiative LDOS hot-spot and the following active helicity control at the deep-subwavelength scale. The proposed V-shaped nanostructure as a functional unit is further applied to the helicity-dependent binary encoding and the two-dimensional display applications. The proposed physical principle and experimental configuration can promote the future chiral characterization and manipulation at the deep-subwavelength scale and provide direct guidelines for the optimization of chiral light-matter interactions for future quantum studies.

Analyzing intrinsic plasmonic chirality by tracking the interplay of electric and magnetic dipole modes.

PubMed

Hu, Li; Huang, Yingzhou; Pan, Lujun; Fang, Yurui

2017-09-11

Plasmonic chirality represents significant potential for novel nanooptical devices due to its association with strong chiroptical responses. Previous reports on plasmonic chirality mechanism mainly focus on phase retardation and coupling. In this paper, we propose a model similar to the chiral molecules for explaining the intrinsic plasmonic chirality mechanism of varies 3D chiral structures quantitatively based on the interplay and mixing of electric and magnetic dipole modes (directly from electromagnetic field numerical simulations), which forms mixed electric and magnetic polarizability.

Chiral corrections to the Adler-Weisberger sum rule

NASA Astrophysics Data System (ADS)

Beane, Silas R.; Klco, Natalie

2016-12-01

The Adler-Weisberger sum rule for the nucleon axial-vector charge, gA , offers a unique signature of chiral symmetry and its breaking in QCD. Its derivation relies on both algebraic aspects of chiral symmetry, which guarantee the convergence of the sum rule, and dynamical aspects of chiral symmetry breaking—as exploited using chiral perturbation theory—which allow the rigorous inclusion of explicit chiral symmetry breaking effects due to light-quark masses. The original derivations obtained the sum rule in the chiral limit and, without the benefit of chiral perturbation theory, made various attempts at extrapolating to nonvanishing pion masses. In this paper, the leading, universal, chiral corrections to the chiral-limit sum rule are obtained. Using PDG data, a recent parametrization of the pion-nucleon total cross sections in the resonance region given by the SAID group, as well as recent Roy-Steiner equation determinations of subthreshold amplitudes, threshold parameters, and correlated low-energy constants, the Adler-Weisberger sum rule is confronted with experimental data. With uncertainty estimates associated with the cross-section parametrization, the Goldberger-Treimann discrepancy, and the truncation of the sum rule at O (Mπ4) in the chiral expansion, this work finds gA=1.248 ±0.010 ±0.007 ±0.013 .

Chiral magnetic microspheres purified by centrifugal field flow fractionation and microspheres magnetic chiral chromatography for benzoin racemate separation.

PubMed

Tian, Ailin; Qi, Jing; Liu, Yating; Wang, Fengkang; Ito, Yoichiro; Wei, Yun

2013-08-30

Separation of enantiomers still remains a challenge due to their identical physical and chemical properties in a chiral environment, and the research on specific chiral selector along with separation techniques continues to be conducted to resolve individual enantiomers. In our laboratory the promising magnetic chiral microspheres Fe3O4@SiO2@cellulose-2, 3-bis (3,5-dimethylphenylcarbamate) have been developed to facilitate the resolution using both its magnetic property and chiral recognition ability. In our present studies this magnetic chiral selector was first purified by centrifuge field flow fractionation, and then used to separate benzoin racemate by a chromatographic method. Uniform-sized and masking-impurity-removed magnetic chiral selector was first obtained by field flow fractionation with ethanol through a spiral column mounted on the type-J planetary centrifuge, and using the purified magnetic chiral selector, the final chromatographic separation of benzoin racemate was successfully performed by eluting with ethanol through a coiled tube (wound around the cylindrical magnet to retain the magnetic chiral selector as a stationary phase) submerged in dry ice. In addition, an external magnetic field facilitates the recycling of the magnetic chiral selector. Copyright © 2013 Elsevier B.V. All rights reserved.

Broadband reflection of polymer-stabilized chiral nematic liquid crystals induced by a chiral azobenzene compound.

PubMed

Chen, Xingwu; Wang, Ling; Chen, Yinjie; Li, Chenyue; Hou, Guoyan; Liu, Xin; Zhang, Xiaoguang; He, Wanli; Yang, Huai

2014-01-21

A chiral nematic liquid crystal-photopolymerizable monomer-chiral azobenzene compound composite was prepared and then polymerized under UV irradiation. The reflection wavelength of the composite can be extended to cover the 1000-2400 nm range and also be adjusted to the visible light region by controlling the concentration of chiral compounds.

Theoretical Foundation for Electric-Dipole-Allowed Chiral-Specific Fluorescence Optical Rotary Dispersion (F-ORD) from Interfacial Assemblies.

PubMed

Deng, Fengyuan; Ulcickas, James R W; Simpson, Garth J

2016-11-03

Fluorescence optical rotary dispersion (F-ORD) is proposed as a novel chiral-specific and interface-specific spectroscopic method. F-ORD measurements of uniaxial assemblies are predicted to be fully electric-dipole-allowed, with corresponding increases in sensitivity to chirality relative to chiral-specific measurements in isotropic assemblies that are commonly interpreted through coupling between electric and magnetic dynamic dipoles. Observations of strong chiral sensitivity in prior single-molecule fluorescence measurements of chiral interfacial molecules are in excellent qualitative agreement with the predictions of the F-ORD mechanism and challenging to otherwise explain. F-ORD may provide methods to suppress background fluorescence in studies of biological interfaces, as the detected signal requires both polar local order and interfacial chirality. In addition, the molecular-level descriptions of the mechanisms underpinning F-ORD may also potentially apply to aid in interpreting chiral-specific Raman and surface-enhanced Raman spectroscopy measurements of uniaxially oriented assemblies, opening up opportunities for chiral-specific and interface-specific vibrational spectroscopy.

Role of Achiral Nucleobases in Multicomponent Chiral Self-Assembly: Purine-Triggered Helix and Chirality Transfer.

PubMed

Deng, Ming; Zhang, Li; Jiang, Yuqian; Liu, Minghua

2016-11-21

Chiral self-assembly is a basic process in biological systems, where many chiral biomolecules such as amino acids and sugars play important roles. Achiral nucleobases usually covalently bond to saccharides and play a significant role in the formation of the double helix structure. However, it remains unclear how the achiral nucleobases can function in chiral self-assembly without the sugar modification. Herein, we have clarified that purine nucleobases could trigger N-(9-fluorenylmethox-ycarbonyl) (Fmoc)-protected glutamic acid to self-assemble into helical nanostructures. Moreover, the helical nanostructure could serve as a matrix and transfer the chirality to an achiral fluorescence probe, thioflavin T (ThT). Upon chirality transfer, the ThT showed not only supramolecular chirality but also circular polarized fluorescence (CPL). Without the nucleobase, the self-assembly processes cannot happen, thus providing an example where achiral molecules played an essential role in the expression and transfer of the chirality. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chiral superconductors.

PubMed

Kallin, Catherine; Berlinsky, John

2016-05-01

Chiral superconductivity is a striking quantum phenomenon in which an unconventional superconductor spontaneously develops an angular momentum and lowers its free energy by eliminating nodes in the gap. It is a topologically non-trivial state and, as such, exhibits distinctive topological modes at surfaces and defects. In this paper we discuss the current theory and experimental results on chiral superconductors, focusing on two of the best-studied systems, Sr2RuO4, which is thought to be a chiral triplet p-wave superconductor, and UPt3, which has two low-temperature superconducting phases (in zero magnetic field), the lower of which is believed to be chiral triplet f-wave. Other systems that may exhibit chiral superconductivity are also discussed. Key signatures of chiral superconductivity are surface currents and chiral Majorana modes, Majorana states in vortex cores, and the possibility of half-flux quantum vortices in the case of triplet pairing. Experimental evidence for chiral superconductivity from μSR, NMR, strain, polar Kerr effect and Josephson tunneling experiments are discussed.

Acylation of Chiral Alcohols: A Simple Procedure for Chiral GC Analysis.

PubMed

Oromí-Farrús, Mireia; Torres, Mercè; Canela, Ramon

2012-01-01

The use of iodine as a catalyst and either acetic or trifluoroacetic acid as a derivatizing reagent for determining the enantiomeric composition of acyclic and cyclic aliphatic chiral alcohols was investigated. Optimal conditions were selected according to the molar ratio of alcohol to acid, the reaction time, and the reaction temperature. Afterwards, chiral stability of chiral carbons was studied. Although no isomerization was observed when acetic acid was used, partial isomerization was detected with the trifluoroacetic acid. A series of chiral alcohols of a widely varying structural type were then derivatized with acetic acid using the optimal conditions. The resolution of the enantiomeric esters and the free chiral alcohols was measured using a capillary gas chromatograph equipped with a CP Chirasil-DEX CB column. The best resolutions were obtained with 2-pentyl acetates (α = 3.00) and 2-hexyl acetates (α = 1.95). This method provides a very simple and efficient experimental workup procedure for analyzing chiral alcohols by chiral-phase GC.

Enantiomeric Profiling of Chiral Pharmacologically Active Compounds in the Environment with the Usage of Chiral Liquid Chromatography 
Coupled with Tandem Mass Spectrometry

PubMed Central

Camacho-Muñoz, Dolores; Petrie, Bruce; Castrignanò, Erika; Kasprzyk-Hordern, Barbara

2016-01-01

The issue of drug chirality is attracting increasing attention among the scientific community. The phenomenon of chirality has been overlooked in environmental research (environmental occurrence, fate and toxicity) despite the great impact that chiral pharmacologically active compounds (cPACs) can provoke on ecosystems. The aim of this paper is to introduce the topic of chirality and its implications in environmental contamination. Special attention has been paid to the most recent advances in chiral analysis based on liquid chromatography coupled with mass spectrometry and the most popular protein based chiral stationary phases. Several groups of cPACs of environmental relevance, such as illicit drugs, human and veterinary medicines were discussed. The increase in the number of papers published in the area of chiral environmental analysis indicates that researchers are actively pursuing new opportunities to provide better understanding of environmental impacts resulting from the enantiomerism of cPACs. PMID:27713682

Topological chiral phonons in center-stacked bilayer triangle lattices

NASA Astrophysics Data System (ADS)

Xu, Xifang; Zhang, Wei; Wang, Jiaojiao; Zhang, Lifa

2018-06-01

Since chiral phonons were found in an asymmetric two-dimensional hexagonal lattice, there has been growing interest in the study of phonon chirality, which were experimentally verified very recently in monolayer tungsten diselenide (2018 Science 359 579). In this work, we find chiral phonons with nontrivial topology in center-stacked bilayer triangle lattices. At the Brillouin-zone corners, (), circularly polarized phonons and nonzero phonon Berry curvature are observed. Moreover, we find that the phonon chirality remain robust with changing sublattice mass ratio and interlayer coupling. The chiral phonons at the valleys are demonstrated in doubler-layer sodium chloride along the [1 1 1] direction. We believe that the findings on topological chiral phonons in triangle lattices will give guidance in the study of chiral phonons in real materials and promote the phononic applications.

Enhanced Chiral Discriminatory van der Waals Interactions Mediated by Chiral Surfaces

NASA Astrophysics Data System (ADS)

Barcellona, Pablo; Safari, Hassan; Salam, A.; Buhmann, Stefan Yoshi

2017-05-01

We predict a discriminatory interaction between a chiral molecule and an achiral molecule which is mediated by a chiral body. To achieve this, we generalize the van der Waals interaction potential between two ground-state molecules with electric, magnetic, and chiral response to nontrivial environments. The force is evaluated using second-order perturbation theory with an effective Hamiltonian. Chiral media enhance or reduce the free interaction via many-body interactions, making it possible to measure the chiral contributions to the van der Waals force with current technology. The van der Waals interaction is discriminatory with respect to enantiomers of different handedness and could be used to separate enantiomers. We also suggest a specific geometric configuration where the electric contribution to the van der Waals interaction is zero, making the chiral component the dominant effect.

No chiral truncation of quantum log gravity?

NASA Astrophysics Data System (ADS)

Andrade, Tomás; Marolf, Donald

2010-03-01

At the classical level, chiral gravity may be constructed as a consistent truncation of a larger theory called log gravity by requiring that left-moving charges vanish. In turn, log gravity is the limit of topologically massive gravity (TMG) at a special value of the coupling (the chiral point). We study the situation at the level of linearized quantum fields, focussing on a unitary quantization. While the TMG Hilbert space is continuous at the chiral point, the left-moving Virasoro generators become ill-defined and cannot be used to define a chiral truncation. In a sense, the left-moving asymptotic symmetries are spontaneously broken at the chiral point. In contrast, in a non-unitary quantization of TMG, both the Hilbert space and charges are continuous at the chiral point and define a unitary theory of chiral gravity at the linearized level.

Micropatterning of cells reveals chiral morphogenesis

PubMed Central

2013-01-01

Invariant left-right (LR) patterning or chirality is critical for embryonic development. The loss or reversal of LR asymmetry is often associated with malformations and disease. Although several theories have been proposed, the exact mechanism of the initiation of the LR symmetry has not yet been fully elucidated. Recently, chirality has been detected within single cells as well as multicellular structures using several in vitro approaches. These studies demonstrated the universality of cell chirality, its dependence on cell phenotype, and the role of physical boundaries. In this review, we discuss the theories for developmental LR asymmetry, compare various in vitro cell chirality model systems, and highlight possible roles of cell chirality in stem cell differentiation. We emphasize that the in vitro cell chirality systems have great promise for helping unveil the nature of chiral morphogenesis in development. PMID:23672821

Cooperative expression of atomic chirality in inorganic nanostructures.

PubMed

Wang, Peng-Peng; Yu, Shang-Jie; Govorov, Alexander O; Ouyang, Min

2017-02-02

Cooperative chirality phenomena extensively exist in biomolecular and organic systems via intra- and inter-molecular interactions, but study of inorganic materials has been lacking. Here we report, experimentally and theoretically, cooperative chirality in colloidal cinnabar mercury sulfide nanocrystals that originates from chirality interplay between the crystallographic lattice and geometric morphology at different length scales. A two-step synthetic scheme is developed to allow control of critical parameters of these two types of handedness, resulting in different chiral interplays expressed as observables through materials engineering. Furthermore, we adopt an electromagnetic model with the finite element method to elucidate cooperative chirality in inorganic systems, showing excellent agreement with experimental results. Our study enables an emerging class of nanostructures with tailored cooperative chirality that is vital for fundamental understanding of nanoscale chirality as well as technology applications based on new chiroptical building blocks.

Cooperative expression of atomic chirality in inorganic nanostructures

PubMed Central

Wang, Peng-peng; Yu, Shang-Jie; Govorov, Alexander O; Ouyang, Min

2017-01-01

Cooperative chirality phenomena extensively exist in biomolecular and organic systems via intra- and inter-molecular interactions, but study of inorganic materials has been lacking. Here we report, experimentally and theoretically, cooperative chirality in colloidal cinnabar mercury sulfide nanocrystals that originates from chirality interplay between the crystallographic lattice and geometric morphology at different length scales. A two-step synthetic scheme is developed to allow control of critical parameters of these two types of handedness, resulting in different chiral interplays expressed as observables through materials engineering. Furthermore, we adopt an electromagnetic model with the finite element method to elucidate cooperative chirality in inorganic systems, showing excellent agreement with experimental results. Our study enables an emerging class of nanostructures with tailored cooperative chirality that is vital for fundamental understanding of nanoscale chirality as well as technology applications based on new chiroptical building blocks. PMID:28148957

Application of L-proline derivatives as chiral shift reagents for enantiomeric recognition of carboxylic acids.

PubMed

Naziroglu, Hayriye Nevin; Durmaz, Mustafa; Bozkurt, Selahattin; Sirit, Abdulkadir

2011-07-01

Four proline-derived chiral receptors 5-8 were readily synthesized starting from L-proline. The enantiomeric recognition ability of chiral receptors was examined with a series of carboxylic acids by (1) H NMR spectroscopy. The molar ratio and the association constants of the chiral compounds with each of the enantiomers of guest molecules were determined by using Job plots and a nonlinear least-squares fitting method, respectively. The Job plots indicate that the hosts form 1:1 instantaneous complexes with all guests. The receptors exhibited different chiral recognition abilities toward the enantiomers of racemic guests. Among the chiral receptors used in this study, prolinamide 6 was found to be the best chiral shift reagent and is effective for the determination of the enantiomeric excess of chiral carboxylic acids. Copyright © 2011 Wiley-Liss, Inc.

Chirality-dependent cellular uptake of chiral nanocarriers and intracellular delivery of different amounts of guest molecules

NASA Astrophysics Data System (ADS)

Kehr, Nermin Seda; Jose, Joachim

2017-12-01

We demonstrate the organic molecules loaded and chiral polymers coated periodic mesoporous organosilica (PMO) to generate chiral nanocarriers that we used to study chirality-dependent cellular uptake in serum and serum-free media and the subsequent delivery of different amounts of organic molecules into cells. Our results show that the amount of internalized PMO and thus the transported amount of organic molecules by nanocarrier PMO into cells was chirality dependent and controlled by hard/soft protein corona formation on the PMO surfaces. Therefore, this study demonstrate that chiral porous nanocarriers could potentially be used as advanced drug delivery systems which are able to use the specific chiral surface-protein interactions to influence/control the amount of (bio)active molecules delivered to cells in drug delivery and/or imaging applications.

More on asymptotically anti-de Sitter spaces in topologically massive gravity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henneaux, Marc; Physique theorique et mathematique, Universite Libre de Bruxelles and International Solvay Institutes, ULB Campus Plaine C.P. 231, B-1050 Bruxelles; Martinez, Cristian

2010-09-15

Recently, the asymptotic behavior of three-dimensional anti-de Sitter (AdS) gravity with a topological mass term was investigated. Boundary conditions were given that were asymptotically invariant under the two dimensional conformal group and that included a falloff of the metric sufficiently slow to consistently allow pp-wave type of solutions. Now, pp waves can have two different chiralities. Above the chiral point and at the chiral point, however, only one chirality can be considered, namely, the chirality that has the milder behavior at infinity. The other chirality blows up faster than AdS and does not define an asymptotically AdS spacetime. By contrast,more » both chiralities are subdominant with respect to the asymptotic behavior of AdS spacetime below the chiral point. Nevertheless, the boundary conditions given in the earlier treatment only included one of the two chiralities (which could be either one) at a time. We investigate in this paper whether one can generalize these boundary conditions in order to consider simultaneously both chiralities below the chiral point. We show that this is not possible if one wants to keep the two-dimensional conformal group as asymptotic symmetry group. Hence, the boundary conditions given in the earlier treatment appear to be the best possible ones compatible with conformal symmetry. In the course of our investigations, we provide general formulas controlling the asymptotic charges for all values of the topological mass (not just below the chiral point).« less

Effect of molecular structure of tartrates on chiral recognition of tartrate-boric acid complex chiral selectors in chiral microemulsion electrokinetic chromatography.

PubMed

Hu, Shao-Qiang; Chen, Yong-Lei; Zhu, Hua-Dong; Shi, Hai-Jun; Yan, Na; Chen, Xing-Guo

2010-08-20

Eight l-tartrates and a d-tartrate with different alcohol moieties were used as chiral oils to prepare chiral microemulsions, which were utilized in conjunction with borate buffer to separate the enantiomers of beta-blockers or structurally related compounds by the chiral microemulsion electrokinetic chromatography (MEEKC) method. Among them, six were found to have a relatively good chiral separation performance and their chiral recognition effect in terms of both enantioselectivity and resolution increases linearly with the number of carbon atoms in the alkyl group of alcohol moiety. The tartrates containing alkyl groups of different structures but the same number of carbon atoms, i.e. one of straight chain and one of branched chain, provide similar enantioseparations. The trend was elucidated according to the changes in the difference of the steric matching between the molecules of two enantiomers and chiral selector. Furthermore, it was demonstrated for the first time that a water insoluble solid compound, di-i-butyl l-tartrate (mp. 73.5 degrees C), can be used as an oil to prepare a stable microemulsion to be used in the chiral MEEKC successfully. And a critical effect of the microemulsion for chiral separation, which has never been reported before, was found in this experiment, namely providing a hydrophobic environment to strengthen the interactions between the chiral selector and enantiomers. Copyright 2010 Elsevier B.V. All rights reserved.

Intelligent chiral sensing based on supramolecular and interfacial concepts.

PubMed

Ariga, Katsuhiko; Richards, Gary J; Ishihara, Shinsuke; Izawa, Hironori; Hill, Jonathan P

2010-01-01

Of the known intelligently-operating systems, the majority can undoubtedly be classed as being of biological origin. One of the notable differences between biological and artificial systems is the important fact that biological materials consist mostly of chiral molecules. While most biochemical processes routinely discriminate chiral molecules, differentiation between chiral molecules in artificial systems is currently one of the challenging subjects in the field of molecular recognition. Therefore, one of the important challenges for intelligent man-made sensors is to prepare a sensing system that can discriminate chiral molecules. Because intermolecular interactions and detection at surfaces are respectively parts of supramolecular chemistry and interfacial science, chiral sensing based on supramolecular and interfacial concepts is a significant topic. In this review, we briefly summarize recent advances in these fields, including supramolecular hosts for color detection on chiral sensing, indicator-displacement assays, kinetic resolution in supramolecular reactions with analyses by mass spectrometry, use of chiral shape-defined polymers, such as dynamic helical polymers, molecular imprinting, thin films on surfaces of devices such as QCM, functional electrodes, FET, and SPR, the combined technique of magnetic resonance imaging and immunoassay, and chiral detection using scanning tunneling microscopy and cantilever technology. In addition, we will discuss novel concepts in recent research including the use of achiral reagents for chiral sensing with NMR, and mechanical control of chiral sensing. The importance of integration of chiral sensing systems with rapidly developing nanotechnology and nanomaterials is also emphasized.

Anatomy of the chiral magnetic effect in and out of equilibrium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kharzeev, Dmitri; Stephanov, Mikhail; Yee, Ho-Ung

Here, we identify a new contribution to the chiral magnetic conductivity at finite frequencies—the magnetization current. This allows us to quantitatively reproduce the known field-theoretic time-dependent (AC) chiral magnetic response in terms of kinetic theory. We also evaluate the corresponding AC chiral magnetic conductivity in two-flavor QCD plasma at weak coupling. The magnetization current results from the spin response of chiral quasiparticles to magnetic field, and is thus proportional to the quasiparticle’s g -factor. Furthemrore, in condensed matter systems, where the chiral quasiparticles are emergent and the g -factor can significantly differ from 2, this opens up the possibility ofmore » tuning the AC chiral magnetic response.« less

Anatomy of the chiral magnetic effect in and out of equilibrium

DOE PAGES

Kharzeev, Dmitri; Stephanov, Mikhail; Yee, Ho-Ung

2017-03-28

Here, we identify a new contribution to the chiral magnetic conductivity at finite frequencies—the magnetization current. This allows us to quantitatively reproduce the known field-theoretic time-dependent (AC) chiral magnetic response in terms of kinetic theory. We also evaluate the corresponding AC chiral magnetic conductivity in two-flavor QCD plasma at weak coupling. The magnetization current results from the spin response of chiral quasiparticles to magnetic field, and is thus proportional to the quasiparticle’s g -factor. Furthemrore, in condensed matter systems, where the chiral quasiparticles are emergent and the g -factor can significantly differ from 2, this opens up the possibility ofmore » tuning the AC chiral magnetic response.« less

Active chiral fluids.

PubMed

Fürthauer, S; Strempel, M; Grill, S W; Jülicher, F

2012-09-01

Active processes in biological systems often exhibit chiral asymmetries. Examples are the chirality of cytoskeletal filaments which interact with motor proteins, the chirality of the beat of cilia and flagella as well as the helical trajectories of many biological microswimmers. Here, we derive constitutive material equations for active fluids which account for the effects of active chiral processes. We identify active contributions to the antisymmetric part of the stress as well as active angular momentum fluxes. We discuss four types of elementary chiral motors and their effects on a surrounding fluid. We show that large-scale chiral flows can result from the collective behavior of such motors even in cases where isolated motors do not create a hydrodynamic far field.

The kinetics of chirality assignment in catalytic single-walled carbon nanotube growth and the routes towards selective growth.

PubMed

Xu, Ziwei; Qiu, Lu; Ding, Feng

2018-03-21

Depending on its specific structure, or so-called chirality, a single-walled carbon nanotube (SWCNT) can be either a conductor or a semiconductor. This feature ensures great potential for building ∼1 nm sized electronics if chirality-selected SWCNTs could be achieved. However, due to the limited understanding of the growth mechanism of SWCNTs, reliable methods for chirality-selected SWCNTs are still pending. Here we present a theoretical model on the chirality assignment and control of SWCNTs during the catalytic growth. This study reveals that the chirality of a SWCNT is determined by the kinetic incorporation of pentagons, especially the last (6 th ) one, during the nucleation stage. Our analysis showed that the chirality of a SWCNT is randomly assigned on a liquid or liquid-like catalyst surface, and two routes of synthesizing chirality-selected SWCNTs, which are verified by recent experimental achievements, are demonstrated. They are (i) by using high melting point crystalline catalysts, such as Ta, W, Re, Os, or their alloys, and (ii) by frequently changing the chirality of SWCNTs during their growth. This study paves the way for achieving chirality-selective SWCNT growth for high performance SWCNT based electronics.

Chemical chiral pollution: Impact on the society and science and need of the regulations in the 21st century.

PubMed

Basheer, Al Arsh

2018-04-01

The chiral pollution is a serious issue for our health and environment due to the enantio-selective biodegradation of the chiral pollutants. It has adverse impact on our society and science. There is a big loss of our economy due to the use of racemic agrochemicals. The most notorious chiral pollutants are pesticides, polychloro biphenyls, polyaromatic hydrocarbons, brominated flame retardants, drugs, and pharmaceuticals. More than 1500 chiral pollutants are present in the environment. Unfortunately, there is no regulation and control of the chiral pollutants. Therefore, it is an urgent need of the present 21st century to develop a data bank on the chiral pollutants, guidelines for controlling the production, sale and use of the racemic agrochemicals and the other industrial products. The Governments of the different countries should come forward to initiate the regulations. US, FDA, US EPA, and WHO are the most important regulatory authorities and should think about the chiral pollutants. The present article highlights the impact of the chiral pollution on the society and science. Besides, the efforts have also been made to emphasize the need of the regulations to control the chiral pollution. © 2017 Wiley Periodicals, Inc.

Laminar and Turbulent Dynamos in Chiral Magnetohydrodynamics. I. Theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rogachevskii, Igor; Kleeorin, Nathan; Ruchayskiy, Oleg

2017-09-10

The magnetohydrodynamic (MHD) description of plasmas with relativistic particles necessarily includes an additional new field, the chiral chemical potential associated with the axial charge (i.e., the number difference between right- and left-handed relativistic fermions). This chiral chemical potential gives rise to a contribution to the electric current density of the plasma ( chiral magnetic effect ). We present a self-consistent treatment of the chiral MHD equations , which include the back-reaction of the magnetic field on a chiral chemical potential and its interaction with the plasma velocity field. A number of novel phenomena are exhibited. First, we show that themore » chiral magnetic effect decreases the frequency of the Alfvén wave for incompressible flows, increases the frequencies of the Alfvén wave and of the fast magnetosonic wave for compressible flows, and decreases the frequency of the slow magnetosonic wave. Second, we show that, in addition to the well-known laminar chiral dynamo effect, which is not related to fluid motions, there is a dynamo caused by the joint action of velocity shear and chiral magnetic effect. In the presence of turbulence with vanishing mean kinetic helicity, the derived mean-field chiral MHD equations describe turbulent large-scale dynamos caused by the chiral alpha effect, which is dominant for large fluid and magnetic Reynolds numbers. The chiral alpha effect is due to an interaction of the chiral magnetic effect and fluctuations of the small-scale current produced by tangling magnetic fluctuations (which are generated by tangling of the large-scale magnetic field by sheared velocity fluctuations). These dynamo effects may have interesting consequences in the dynamics of the early universe, neutron stars, and the quark–gluon plasma.« less

Determining the orientation of a chiral substrate using full-hemisphere angle-resolved photoelectron spectroscopy.

PubMed

Tadich, A; Riley, J; Thomsen, L; Cowie, B C C; Gladys, M J

2011-10-21

Chiral interfaces and substrates are of increasing importance in the field of enantioselective chemistry. To fully understand the enantiospecific interactions between chiral adsorbate molecules and the chiral substrate, it is vital that the chiral orientation of the substrate is known. In this Letter we demonstrate that full-hemisphere angle-resolved photoemission permits straightforward identification of the orientation of a chiral surface. The technique can be applied to any solid state system for which photoemission measurements are possible. © 2011 American Physical Society

Disordered two-dimensional electron systems with chiral symmetry

NASA Astrophysics Data System (ADS)

Markoš, P.; Schweitzer, L.

2012-10-01

We review the results of our recent numerical investigations on the electronic properties of disordered two dimensional systems with chiral unitary, chiral orthogonal, and chiral symplectic symmetry. Of particular interest is the behavior of the density of states and the logarithmic scaling of the smallest Lyapunov exponents in the vicinity of the chiral quantum critical point in the band center at E=0. The observed peaks or depressions in the density of states, the distribution of the critical conductances, and the possible non-universality of the critical exponents for certain chiral unitary models are discussed.

Chiral Symmetry Breaking and Complete Chiral Purity by Thermodynamic-Kinetic Feedback Near Equilibrium: Implications for the Origin of Biochirality

NASA Astrophysics Data System (ADS)

Viedma, Cristobal

2007-05-01

Chiral symmetry breaking occurs when a physical or chemical process spontaneously generates a large excess of one of the two enantiomers-left-handed (L) or right-handed (D)--with no preference as to which of the two enantiomers is produced. From the viewpoint of energy, these two enantiomers can exist with an equal probability, and inorganic processes that involve chiral products commonly yield a racemic mixture of both. The fact that biologically relevant molecules exist only as one of the two enantiomers is a fascinating example of complete symmetry breaking in chirality and has long intrigued the science community. The origin of this selective chirality has remained a fundamental enigma with regard to the origin of life since the time of Pasteur, some 140 years ago. Here, it is shown that two populations of chiral crystals of left and right hand cannot coexist in solution: one of the chiral populations disappears in an irreversible autocatalytic process that nurtures the other one. Final and complete chiral purity seems to be an inexorable fate in the course of the common process of growth-dissolution. This unexpected chiral symmetry breaking can be explained by the feedback between the thermodynamic control of dissolution and the kinetics of the growth process near equilibrium. This ``thermodynamic-kinetic feedback near equilibrium'' is established as a mechanism to achieve complete chiral purity in solid state from a previously solid racemic medium. The way in which this mechanism could operate in solutions of chiral biomolecules is described. Finally, based on this mechanism, experiments designed to search for chiral purity in a new way are proposed: chiral purity of amino acids or biopolymers is predicted in solid phase from a previously solid racemic medium. This process may have played a key role in the origin of biochirality.

Free-standing mesoporous silica films with tunable chiral nematic structures.

PubMed

Shopsowitz, Kevin E; Qi, Hao; Hamad, Wadood Y; Maclachlan, Mark J

2010-11-18

Chirality at the molecular level is found in diverse biological structures, such as polysaccharides, proteins and DNA, and is responsible for many of their unique properties. Introducing chirality into porous inorganic solids may produce new types of materials that could be useful for chiral separation, stereospecific catalysis, chiral recognition (sensing) and photonic materials. Template synthesis of inorganic solids using the self-assembly of lyotropic liquid crystals offers access to materials with well-defined porous structures, but only recently has chirality been introduced into hexagonal mesostructures through the use of a chiral surfactant. Efforts to impart chirality at a larger length scale using self-assembly are almost unknown. Here we describe the development of a photonic mesoporous inorganic solid that is a cast of a chiral nematic liquid crystal formed from nanocrystalline cellulose. These materials may be obtained as free-standing films with high surface area. The peak reflected wavelength of the films can be varied across the entire visible spectrum and into the near-infrared through simple changes in the synthetic conditions. To the best of our knowledge these are the first materials to combine mesoporosity with long-range chiral ordering that produces photonic properties. Our findings could lead to the development of new materials for applications in, for example, tuneable reflective filters and sensors. In addition, this type of material could be used as a hard template to generate other new materials with chiral nematic structures.

ENANTIOMER-SPECIFIC EFFECTS OF CHIRAL POLLUTANTS

EPA Science Inventory

Enantiomers, the mirror image isomers of chiral pollutants, are known to be selective in their interaction with other chiral molecules, including enzymes and other biochemicals. Considerable research has shown, for example, that chiral pesticides are degraded selectively by micr...

Coordinative Alignment of Chiral Molecules to Control over the Chirality Transfer in Spontaneous Resolution and Asymmetric Catalysis.

PubMed

Xia, Zhengqiang; Jing, Xu; He, Cheng; Wang, Xiaoge; Duan, Chunying

2017-11-13

The production and availability of enantiomerically pure compounds that spurred the development of chiral technologies and materials are very important to the fine chemicals and pharmaceutical industries. By coordinative alignment of enantiopure guests in the metal‒organic frameworks, we reported an approach to control over the chirality of homochiral crystallization and asymmetric transformation. Synthesized by achiral triphenylamine derivatives, the chirality of silver frameworks was determined by the encapsulated enantiopure azomethine ylides, from which clear interaction patterns were observed to explore the chiral induction principles. With the changing of addition sequence of substrates, the enantioselectivity of asymmetric cycloaddition was controlled to verify the determinant on the chirality of the bulky MOF materials. The economical chirality amplification that merges a series of complicated self-inductions, bulk homochiral crystallization and enantioselective catalysis opens new avenues for enantiopure chemical synthesis and provides a promising path for the directional design and development of homochiral materials.

[From symmetries to the laws of evolution. I. Chirality as a means of active media stratification].

PubMed

Tverdislov, V A; Sidorova, A É; Iakovenko, L V

2012-01-01

Features of the hypothetical evolution of a hierarchy of chiral objects formed by active media are discussed. On the basis of experimental facts a new synergetic generalization is made: an evolving system can repeatedly broaden the spectrum of its symmetry types within one level of organization which increases its complexity and change the sign of chirality during transition to a higher level. Switching the chirality sign of macroscopic objects provides irreversibility of stratification. The known chirality of biological structures at different levels suggests that the chiral L/D-stratification should be universal and the hierarchical paths are stable and determined. A high level enantiomorph with reciprocal chirality demonstrates a wider spectrum of functionality. A fractal description of natural hierarchical systems is pointed out to be inadequate because it implicates invariance of the chirality sign of the objects at different scales.

Chirality correlation in double-wall carbon nanotubes as studied by electron diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hirahara, Kaori; Bandow, Shunji; Kociak, Mathieu

2006-05-15

Structural correlation between two adjacent graphitic layers in double-wall carbon nanotubes (DWNTs) was systematically examined by using electron diffraction. Chiral angles and tube diameters were carefully measured, and the chiral indices of individual DWNTs were accurately determined. As a result, it was found that the interlayer distances of DWNTs were widely distributed in the range between 0.34 and 0.38 nm. Chiralities of the inner and outer tubes tended to be distributed at higher chiral angles, approaching 30 deg., for the tubes with diameter D<{approx}3 nm. On the other hand, for the tubes with D>{approx}3 nm, the chiral angles were widelymore » distributed, covering the chiral map entirely. Therefore, we consider that tubes with small diameters have a tendency to form armchair type. Correlation of chiralities between the inner and outer tubes was found to be random.« less

Chirality effect in disordered graphene ribbon junctions

NASA Astrophysics Data System (ADS)

Long, Wen

2012-05-01

We investigate the influence of edge chirality on the electronic transport in clean or disordered graphene ribbon junctions. By using the tight-binding model and the Landauer-Büttiker formalism, the junction conductance is obtained. In the clean sample, the zero-magnetic-field junction conductance is strongly chirality-dependent in both unipolar and bipolar ribbons, whereas the high-magnetic-field conductance is either chirality-independent in the unipolar or chirality-dependent in the bipolar ribbon. Furthermore, we study the disordered sample in the presence of magnetic field and find that the junction conductance is always chirality-insensitive for both unipolar and bipolar ribbons with adequate disorders. In addition, the disorder-induced conductance plateaus can exist in all chiral bipolar ribbons provided the disorder strength is moderate. These results suggest that we can neglect the effect of edge chirality in fabricating electronic devices based on the magnetotransport in a disordered graphene ribbon.

Molecular description of the propagation of chirality from molecules to complex systems: different mechanisms controlled by hydrophobic interactions.

PubMed

Marinelli, Fabrizio; Sorrenti, Alessandro; Corvaglia, Valentina; Leone, Vanessa; Mancini, Giovanna

2012-11-12

In this work a combined theoretical and experimental approach was used to elucidate and describe at the molecular level the basic interactions that drive the transfer of the chiral information from chiral surfactant molecules to dye/surfactant assemblies. It was found that both hydrophobic interactions and relative concentrations strongly influence the chiroptical features of the heteroaggregates. In particular it was observed that, depending on the length of the surfactant hydrophobic chain, the chiral information is transferred to the dye by stabilizing an enantiomer either of a chiral conformer or of a chiral topological arrangement. These findings underline the role of hydrophobic interactions in the transfer of chirality and provide an example of the potential of in silico simulations for providing an accurate description of the process of chirality propagation. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chirality detection of enantiomers using twisted optical metamaterials

NASA Astrophysics Data System (ADS)

Zhao, Yang; Askarpour, Amir N.; Sun, Liuyang; Shi, Jinwei; Li, Xiaoqin; Alù, Andrea

2017-01-01

Many naturally occurring biomolecules, such as amino acids, sugars and nucleotides, are inherently chiral. Enantiomers, a pair of chiral isomers with opposite handedness, often exhibit similar physical and chemical properties due to their identical functional groups and composition, yet show different toxicity to cells. Detecting enantiomers in small quantities has an essential role in drug development to eliminate their unwanted side effects. Here we exploit strong chiral interactions with plasmonic metamaterials with specifically designed optical response to sense chiral molecules down to zeptomole levels, several orders of magnitude smaller than what is typically detectable with conventional circular dichroism spectroscopy. In particular, the measured spectra reveal opposite signs in the spectral regime directly associated with different chiral responses, providing a way to univocally assess molecular chirality. Our work introduces an ultrathin, planarized nanophotonic interface to sense chiral molecules with inherently weak circular dichroism at visible and near-infrared frequencies.

Transfer of chirality from light to a Disperse Red 1 molecular glass surface.

PubMed

Mazaheri, Leila; Lebel, Olivier; Nunzi, Jean-Michel

2017-12-01

Chiral structures and materials interact with light in well-documented ways, but light can also interact with achiral materials to generate chirality by inscribing its asymmetric configuration on photoresponsive materials, such as azobenzene derivatives. While it is thus possible to generate both two-dimensional (2D) and three-dimensional (3D) chirality, 2D chirality is especially attractive because of its non-reciprocity. Herein, 2D chirality is induced on the surface of a glass-forming Disperse Red 1 derivative by irradiation with a single laser beam, yielding crossed spontaneous surface relief gratings with different pitches. Azimuth rotations up to 10° have been observed, and the absence of 3D chirality has been confirmed. This method thus allows generating non-reciprocal planar chiral objects by a simple, single irradiation process on a thin film of a material that can easily be processed over large areas or onto small objects.

Chirality detection of enantiomers using twisted optical metamaterials

PubMed Central

Zhao, Yang; Askarpour, Amir N.; Sun, Liuyang; Shi, Jinwei; Li, Xiaoqin; Alù, Andrea

2017-01-01

Many naturally occurring biomolecules, such as amino acids, sugars and nucleotides, are inherently chiral. Enantiomers, a pair of chiral isomers with opposite handedness, often exhibit similar physical and chemical properties due to their identical functional groups and composition, yet show different toxicity to cells. Detecting enantiomers in small quantities has an essential role in drug development to eliminate their unwanted side effects. Here we exploit strong chiral interactions with plasmonic metamaterials with specifically designed optical response to sense chiral molecules down to zeptomole levels, several orders of magnitude smaller than what is typically detectable with conventional circular dichroism spectroscopy. In particular, the measured spectra reveal opposite signs in the spectral regime directly associated with different chiral responses, providing a way to univocally assess molecular chirality. Our work introduces an ultrathin, planarized nanophotonic interface to sense chiral molecules with inherently weak circular dichroism at visible and near-infrared frequencies. PMID:28120825

Chirality Transfer in Gold(I)-Catalysed Direct Allylic Etherifications of Unactivated Alcohols: Experimental and Computational Study

PubMed Central

Barker, Graeme; Johnson, David G; Young, Paul C; Macgregor, Stuart A; Lee, Ai-Lan

2015-01-01

Gold(I)-catalysed direct allylic etherifications have been successfully carried out with chirality transfer to yield enantioenriched, γ-substituted secondary allylic ethers. Our investigations include a full substrate-scope screen to ascertain substituent effects on the regioselectivity, stereoselectivity and efficiency of chirality transfer, as well as control experiments to elucidate the mechanistic subtleties of the chirality-transfer process. Crucially, addition of molecular sieves was found to be necessary to ensure efficient and general chirality transfer. Computational studies suggest that the efficiency of chirality transfer is linked to the aggregation of the alcohol nucleophile around the reactive π-bound Au–allylic ether complex. With a single alcohol nucleophile, a high degree of chirality transfer is predicted. However, if three alcohols are present, alternative proton transfer chain mechanisms that erode the efficiency of chirality transfer become competitive. PMID:26248980

Synergistic Enhancement of Microwave Absorption Using Hybridized Polyaniline@helical CNTs with Dual Chirality.

PubMed

Tian, Xin; Meng, Fanbin; Meng, Fanchen; Chen, Xiangnan; Guo, Yifan; Wang, Ying; Zhu, Wenjun; Zhou, Zuowan

2017-05-10

In this study, we designed a dual-chirality hierarchical structure to achieve a synergistically enhanced effect in microwave absorption via the hybridization of nanomaterials. Herein, polyaniline (PANi) nanorods with tunable chirality are grown on helical carbon nanotubes (HCNTs), a typical nanoscale chiral structure, through in situ polymerization. The experimental results show that the hierarchical hybrids (PANi@HCNTs) exhibit distinctly dual chirality and a significant enhancement in electromagnetic (EM) losses compared to those of either pure PANi or HCNTs. The maximum reflection loss of the as-prepared hybrids can reach -32.5 dB at 8.9 GHz. Further analysis demonstrates that combinations of chiral acid-doped PANi and coiled HCNTs with molecular and nanoscale chirality lead to synergistic effects resulting from the dual chirality. The so-called cross-polarization may result in additional interactions with induced EM waves in addition to multiscaled relaxations from functional groups and interfacial polarizations, which can benefit EM absorption.

Chiral recognition and selection during the self-assembly process of protein-mimic macroanions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yin, Panchao; Zhang, Zhi-Ming; Lv, Hongjin

The research on chiral recognition and chiral selection is not only fundamental in resolving the puzzle of homochirality, but also instructive in chiral separation and stereoselective catalysis. Here we report the chiral recognition and chiral selection during the self-assembly process of two enantiomeric wheel-shaped macroanions, [Fe28(μ3-O)8(Tart)16(HCOO)24]20- (Tart=D- or L-tartaric acid tetra-anion). The enantiomers are observed to remain self-sorted and self-assemble into their individual assemblies in their racemic mixture solution. The addition of chiral co-anions can selectively suppress the self-assembly process of the enantiomeric macroanions, which is further used to separate the two enantiomers from their mixtures on the basis ofmore » the size difference between the monomers and the assemblies. We believe that delicate long-range electrostatic interactions could be responsible for such high-level chiral recognition and selection.« less

Chiral Cliffs: Investigating the Influence of Chirality on Binding Affinity.

PubMed

Schneider, Nadine; Lewis, Richard A; Fechner, Nikolas; Ertl, Peter

2018-05-11

Chirality is understood by many as a binary concept: a molecule is either chiral or it is not. In terms of the action of a structure on polarized light, this is indeed true. When examined through the prism of molecular recognition, the answer becomes more nuanced. In this work, we investigated chiral behavior on protein-ligand binding: when does chirality make a difference in binding activity? Chirality is a property of the 3D structure, so recognition also requires an appreciation of the conformation. In many situations, the bioactive conformation is undefined. We set out to address this by defining and using several novel 2D descriptors to capture general characteristic features of the chiral center. Using machine-learning methods, we built different predictive models to estimate if a chiral pair (a set of two enantiomers) might exhibit a chiral cliff in a binding assay. A set of about 3800 chiral pairs extracted from the ChEMBL23 database was used to train and test our models. By achieving an accuracy of up to 75 %, our models provide good performance in discriminating chiral cliffs from non-cliffs. More importantly, we were able to derive some simple guidelines for when one can reasonably use a racemate and when an enantiopure compound is needed in an assay. We critically discuss our results and show detailed examples of using our guidelines. Along with this publication we provide our dataset, our novel descriptors, and the Python code to rebuild the predictive models. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Blue phase liquid crystal phase transition for cyano compound chiral nematic liquid crystal mixtures with three two-ring core structures and chiral dopant concentrations

NASA Astrophysics Data System (ADS)

Shin, Jaesun; Kim, Beomjong; Jung, Wansu; Fahad, Mateen; Park, SangJin; Hong, Sung-Kyu

2017-05-01

Blue phase (BP) temperature range of a chiral nematic liquid crystal (LC) mixture is dependent upon the host nematic LC chemical structure and chiral dopant concentration. In this study, we investigated BP phase transition behaviour and helical twisting power (HTP) using three chiral dopant concentrations of cyano compound chiral nematic LC mixtures incorporating three two-ring core structures in the host nematic LCs. The effect of the host nematic LC core structure, HTP and chiral dopant concentrations were considered on BP temperature ranges, for two types of complete BPI and BPII without isotropic phase (Iso) and two types of coexistence state of BPI+Iso and BPII+Iso.

Chiralities of spiral waves and their transitions.

PubMed

Pan, Jun-ting; Cai, Mei-chun; Li, Bing-wei; Zhang, Hong

2013-06-01

The chiralities of spiral waves usually refer to their rotation directions (the turning orientations of the spiral temporal movements as time elapses) and their curl directions (the winding orientations of the spiral spatial geometrical structures themselves). Traditionally, they are the same as each other. Namely, they are both clockwise or both counterclockwise. Moreover, the chiralities are determined by the topological charges of spiral waves, and thus they are conserved quantities. After the inwardly propagating spirals were experimentally observed, the relationship between the chiralities and the one between the chiralities and the topological charges are no longer preserved. The chiralities thus become more complex than ever before. As a result, there is now a desire to further study them. In this paper, the chiralities and their transition properties for all kinds of spiral waves are systemically studied in the framework of the complex Ginzburg-Landau equation, and the general relationships both between the chiralities and between the chiralities and the topological charges are obtained. The investigation of some other models, such as the FitzHugh-Nagumo model, the nonuniform Oregonator model, the modified standard model, etc., is also discussed for comparison.

Effects of Fluctuations on Inhomogeneous Chiral Transitions

NASA Astrophysics Data System (ADS)

Lee, Tong-Gyu; Yoshiike, Ryo; Tatsumi, Toshitaka

We discuss the features of the order-parameter fluctuations in the normal phase near the phase boundary and their effects on the phase transition from the normal to the inhomogeneous phase with spatially modulated order parameter. Focusing on the chiral symmetry breaking, i.e., inhomogeneous chiral transition, we consider the fluctuation of the chiral pair consisting of quark-antiquark or quark-hole pair within the two-flavor Nambu-Jona-Lasinio model in the chiral limit. We clarify the roles of quantum and thermal fluctuations and also argue that anomalies for thermodynamic quantities in the inhomogeneous chiral transition should lead to phenomenological implications.

Dispersion relations for electromagnetic wave propagation in chiral plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, M. X.; Guo, B., E-mail: binguo@whut.edu.cn; Peng, L.

2014-11-15

The dispersion relations for electromagnetic wave propagation in chiral plasmas are derived using a simplified method and investigated in detail. With the help of the dispersion relations for each eignwave, we explore how the chiral plasmas exhibit negative refraction and investigate the frequency region for negative refraction. The results show that chirality can induce negative refraction in plasmas. Moreover, both the degree of chirality and the external magnetic field have a significant effect on the critical frequency and the bandwidth of the frequency for negative refraction in chiral plasmas. The parameter dependence of the effects is calculated and discussed.

Chiral helimagnetic state in a Kondo lattice model with the Dzyaloshinskii-Moriya interaction

NASA Astrophysics Data System (ADS)

Okumura, Shun; Kato, Yasuyuki; Motome, Yukitoshi

2018-05-01

Monoaxial chiral magnets can form a noncollinear twisted spin structure called the chiral helimagnetic state. We study magnetic properties of such a chiral helimagnetic state, with emphasis on the effect of itinerant electrons. Modeling a monoaxial chiral helimagnet by a one-dimensional Kondo lattice model with the Dzyaloshinskii-Moriya interaction, we perform a variational calculation to elucidate the stable spin configuration in the ground state. We obtain a chiral helimagnetic state as a candidate for the ground state, whose helical pitch is modulated by the model parameters: the Kondo coupling, the Dzyaloshinski-Moriya interaction, and electron filling.

Chirality-specific lift forces of helix under shear flows: Helix perpendicular to shear plane.

PubMed

Zhang, Qi-Yi

2017-02-01

Chiral objects in shear flow experience a chirality-specific lift force. Shear flows past helices in a low Reynolds number regime were studied using slender-body theory. The chirality-specific lift forces in the vorticity direction experienced by helices are dominated by a set of helix geometry parameters: helix radius, pitch length, number of turns, and helix phase angle. Its analytical formula is given. The chirality-specific forces are the physical reasons for the chiral separation of helices in shear flow. Our results are well supported by the latest experimental observations. © 2016 Wiley Periodicals, Inc.

Review on Polarization Selective Terahertz Metamaterials: from Chiral Metamaterials to Stereometamaterials

NASA Astrophysics Data System (ADS)

Philip, Elizabath; Zeki Güngördü, M.; Pal, Sharmistha; Kung, Patrick; Kim, Seongsin Margaret

2017-09-01

In this article, recent progress and development of terahertz chiral metamaterials including stereometamaterials are thoroughly reviewed. This review mainly focuses on the fundamental principles of design and arrangement of meta-atoms in metamaterials exhibiting chirality with various asymmetry and symmetry and 2D and 3D configuration. Related optical and propagation properties in chiral metamaterials, such as optical activity, circular dichroism, and negative refraction for each different chiral metamaterials, are compared and investigated. Finally, comparison between chiral metamaterials with stereometamaterials in terms of the polarization selective operation along with the similarity and the distinction is addressed as well.

Enantiomeric separation of six chiral pesticides that contain chiral sulfur/phosphorus atoms by supercritical fluid chromatography.

PubMed

Zhang, Lijun; Miao, Yelong; Lin, Chunmian

2018-03-01

Six chiral pesticides containing chiral sulfur/phosphorus atoms were separated by supercritical fluid chromatography with supercritical CO 2 as the main mobile phase component. The effect of the chiral stationary phase, different type and concentration of modifiers, column temperature, and backpressure on the separation efficiency was investigated to obtain the appropriate separation condition. Five chiral pesticides (isofenphos-methyl, isocarbophos, flufiprole, fipronil, and ethiprole) were baseline separated under experimental conditions, while isofenphos only obtained partial separation. The Chiralpak AD-3 column showed a better chiral separation ability than others for chiral pesticides containing chiral sulfur/phosphorus atoms. When different modifiers at the same concentration were used, the retention factor of pesticides except flufiprole decreased in the order of isopropanol, ethanol, methanol; meanwhile, the retention factor of flufiprole increased in the order of isopropanol, ethanol, methanol. For a given modifier, the retention factor and resolution decreased on the whole with the increase of its concentration. The enantiomer separation of five chiral pesticides was an "enthalpy-driven" process, and the separation factor decreased as the temperature increased. The backpressure of the mobile phase had little effect on the separation factor and resolution. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Corolla chirality does not contribute to directed pollen movement in Hypericum perforatum (Hypericaceae): mirror image pinwheel flowers function as radially symmetric flowers in pollination.

PubMed

Diller, Carolina; Fenster, Charles B

2016-07-01

Corolla chirality, the pinwheel arrangement of petals within a flower, is found throughout the core eudicots. In 15 families, different chiral type flowers (i.e., right or left rotated corolla) exist on the same plant, and this condition is referred to as unfixed/enantiomorphic corolla chirality. There are no investigations on the significance of unfixed floral chirality on directed pollen movement even though analogous mirror image floral designs, for example, enantiostyly, has evolved in response to selection to direct pollinator and pollen movement. Here, we examine the role of corolla chirality on directing pollen transfer, pollinator behavior, and its potential influence on disassortative mating. We quantified pollen transfer and pollinator behavior and movement for both right and left rotated flowers in two populations of Hypericum perforatum. In addition, we quantified the number of right and left rotated flowers at the individual level. Pollinators were indifferent to corolla chirality resulting in no difference in pollen deposition between right and left flowers. Corolla chirality had no effect on pollinator and pollen movement between and within chiral morphs. Unlike other mirror image floral designs, corolla chirality appears to play no role in promoting disassortative mating in this species.

Synergistic effects on enantioselectivity of zwitterionic chiral stationary phases for separations of chiral acids, bases, and amino acids by HPLC.

PubMed

Hoffmann, Christian V; Pell, Reinhard; Lämmerhofer, Michael; Lindner, Wolfgang

2008-11-15

In an attempt to overcome the limited applicability scope of earlier proposed Cinchona alkaloid-based chiral weak anion exchangers (WAX) and recently reported aminosulfonic acid-based chiral strong cation exchangers (SCX), which are conceptionally restricted to oppositely charged solutes, their individual chiral selector (SO) subunits have been fused in a combinatorial synthesis approach into single, now zwitterionic, chiral SO motifs. The corresponding zwitterionic ion-exchange-type chiral stationary phases (CSPs) in fact combined the applicability spectra of the parent chiral ion exchangers allowing for enantioseparations of chiral acids and amine-type solutes in liquid chromatography using polar organic mode with largely rivaling separation factors as compared to the parent WAX and SCX CSPs. Furthermore, the application spectrum could be remarkably expanded to various zwitterionic analytes such as alpha- and beta-amino acids and peptides. A set of structurally related yet different CSPs consisting of either a quinine or quinidine alkaloid moiety as anion-exchange subunit and various chiral or achiral amino acids as cation-exchange subunits enabled us to derive structure-enantioselectivity relationships, which clearly provided strong unequivocal evidence for synergistic effects of the two oppositely charged ion-exchange subunits being involved in molecular recognition of zwitterionic analytes by zwitterionic SOs driven by double ionic coordination.

Chiral pharmaceuticals: A review on their environmental occurrence and fate processes.

PubMed

Sanganyado, Edmond; Lu, Zhijiang; Fu, Qiuguo; Schlenk, Daniel; Gan, Jay

2017-11-01

More than 50% of pharmaceuticals in current use are chiral compounds. Enantiomers of the same pharmaceutical have identical physicochemical properties, but may exhibit differences in pharmacokinetics, pharmacodynamics and toxicity. The advancement in separation and detection methods has made it possible to analyze trace amounts of chiral compounds in environmental media. As a result, interest on chiral analysis and evaluation of stereoselectivity in environmental occurrence, phase distribution and degradation of chiral pharmaceuticals has grown substantially in recent years. Here we review recent studies on the analysis, occurrence, and fate of chiral pharmaceuticals in engineered and natural environments. Monitoring studies have shown ubiquitous presence of chiral pharmaceuticals in wastewater, surface waters, sediments, and sludge, particularly β-receptor antagonists, analgesics, antifungals, and antidepressants. Selective sorption and microbial degradation have been demonstrated to result in enrichment of one enantiomer over the other. The changes in enantiomer composition may also be caused by biologically catalyzed chiral inversion. However, accurate evaluation of chiral pharmaceuticals as trace environmental pollutants is often hampered by the lack of identification of the stereoconfiguration of enantiomers. Furthermore, a systematic approach including occurrence, fate and transport in various environmental matrices is needed to minimize uncertainties in risk assessment of chiral pharmaceuticals as emerging environmental contaminants. Copyright © 2017 Elsevier Ltd. All rights reserved.

Chirality transition in the epoxidation of (-)-alpha-pinene and successive hydrolysis studied by Raman optical activity and DFT.

PubMed

Qiu, Shi; Li, Guanna; Liu, Peng; Wang, Changhao; Feng, Zhaochi; Li, Can

2010-03-28

Characterization of the chirality evolution involved in chemical and biochemical reaction processes is extremely important to the understanding of the chiral catalysis mechanism. In this work, the chiral transition from the epoxidation of (-)-alpha-pinene to alpha-pinene oxide and successive hydrolysis to (-)-pinanediol has been studied as an archetype of the asymmetric catalysis by Raman optical activity (ROA) and the DFT calculation. Minor changes of the absolute configuration of the chiral products from (-)-alpha-pinene to (-)-pinanediol lead to the dramatic variation in ROA spectra indicating that the chirality is delocalized in the whole molecule rather than only concentrated on the chiral centers. The oxygen atom of alpha-pinene oxide contributes strong ROA signals while the two hydroxyl groups of (-)-pinanediol give no apparent contribution to the chirality in terms of ROA signals. Isolation of the two symmetric anisotropic invariants shows that the predominant contribution to the ROA signals stems from the electric dipole-magnetic dipole invariant, and the bond polarizability model is indeed found to be a good approximation for molecules composed of entirely axially-symmetric bonds in alpha-pinene oxide and (-)-pinanediol. This study demonstrates the feasibility of using ROA to sensitively monitor the variation of the chirality transition during the chiral reactions either in the chemical or biological system.

Natural terpene derivatives as new structural task-specific ionic liquids to enhance the enantiorecognition of acidic enantiomers on teicoplanin-based stationary phase by high-performance liquid chromatography.

PubMed

Flieger, Jolanta; Feder-Kubis, Joanna; Tatarczak-Michalewska, Małgorzata; Płazińska, Anita; Madejska, Anna; Swatko-Ossor, Marta

2017-06-01

We present the specific cooperative effect of a semisynthetic glycopeptide antibiotic teicoplanin and chiral ionic liquids containing the (1R,2S,5R)-(-)-menthol moiety on the chiral recognition of enantiomers of mandelic acid, vanilmandelic acid, and phenyllactic acid. Experiments were performed chromatographically on an Astec Chirobiotic T chiral stationary phase applying the mobile phase with the addition of the chiral ionic liquids. The stereoselective binding of enantiomers to teicoplanin in presence of new chiral ionic liquids were evaluated applying thermodynamic measurements and the docking simulations. Both the experimental and theoretical methods revealed that the chiral recognition of enantiomers in the presence of new chiral ionic liquids was enthalpy driven. The changes of the teicoplanin conformation occurring upon binding of the chiral ionic liquids are responsible for the differences in the standard changes in Gibbs energy (ΔG 0 ) values obtained for complexes formed by the R and S enantiomers and teicoplanin. Docking simulations revealed the steric adjustment between the chiral ionic liquids cyclohexane ring (chair conformation) and the β-d-glucosamine ring of teicoplanin and additionally hydrophobic interactions between the decanoic aliphatic chain of teicoplanin and the alkyl group of the tested salts. The obtained terpene derivatives can be considered as "structural task-specific ionic liquids" responsible for enhancing the chiral resolution in synergistic systems with two chiral selectors. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

ENANTIOMERIC RATIOS OF CHIRAL PCB ATROPISOMERS IN RADIODATED SEDIMENT CORES

EPA Science Inventory

Enantiomeric ratios (ERs)) of chiral polychlorinated biphenyl (PCB) atropisomers were quantified in radiodated sediment cores of Lake Hartwell SC, a reservoir heavily impacted by PCBS, to study spatial and temporal changes in chirality. A chiral analysis of cores showed accumulat...

Spectrum of the Wilson Dirac operator at finite lattice spacings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akemann, G.; Damgaard, P. H.; Splittorff, K.

2011-04-15

We consider the effect of discretization errors on the microscopic spectrum of the Wilson Dirac operator using both chiral perturbation theory and chiral random matrix theory. A graded chiral Lagrangian is used to evaluate the microscopic spectral density of the Hermitian Wilson Dirac operator as well as the distribution of the chirality over the real eigenvalues of the Wilson Dirac operator. It is shown that a chiral random matrix theory for the Wilson Dirac operator reproduces the leading zero-momentum terms of Wilson chiral perturbation theory. All results are obtained for a fixed index of the Wilson Dirac operator. The low-energymore » constants of Wilson chiral perturbation theory are shown to be constrained by the Hermiticity properties of the Wilson Dirac operator.« less

Chiral nanoparticles in singular light fields

PubMed Central

Vovk, Ilia A.; Baimuratov, Anvar S.; Zhu, Weiren; Shalkovskiy, Alexey G.; Baranov, Alexander V.; Fedorov, Anatoly V.; Rukhlenko, Ivan D.

2017-01-01

The studying of how twisted light interacts with chiral matter on the nanoscale is paramount for tackling the challenging task of optomechanical separation of nanoparticle enantiomers, whose solution can revolutionize the entire pharmaceutical industry. Here we calculate optical forces and torques exerted on chiral nanoparticles by Laguerre–Gaussian beams carrying a topological charge. We show that regardless of the beam polarization, the nanoparticles are exposed to both chiral and achiral forces with nonzero reactive and dissipative components. Longitudinally polarized beams are found to produce chirality densities that can be 109 times higher than those of transversely polarized beams and that are comparable to the chirality densities of beams polarized circularly. Our results and analytical expressions prove useful in designing new strategies for mechanical separation of chiral nanoobjects with the help of highly focussed beams. PMID:28378842

Chiral nanoparticles in singular light fields

NASA Astrophysics Data System (ADS)

Vovk, Ilia A.; Baimuratov, Anvar S.; Zhu, Weiren; Shalkovskiy, Alexey G.; Baranov, Alexander V.; Fedorov, Anatoly V.; Rukhlenko, Ivan D.

2017-04-01

The studying of how twisted light interacts with chiral matter on the nanoscale is paramount for tackling the challenging task of optomechanical separation of nanoparticle enantiomers, whose solution can revolutionize the entire pharmaceutical industry. Here we calculate optical forces and torques exerted on chiral nanoparticles by Laguerre-Gaussian beams carrying a topological charge. We show that regardless of the beam polarization, the nanoparticles are exposed to both chiral and achiral forces with nonzero reactive and dissipative components. Longitudinally polarized beams are found to produce chirality densities that can be 109 times higher than those of transversely polarized beams and that are comparable to the chirality densities of beams polarized circularly. Our results and analytical expressions prove useful in designing new strategies for mechanical separation of chiral nanoobjects with the help of highly focussed beams.

Chirality: a relational geometric-physical property.

PubMed

Gerlach, Hans

2013-11-01

The definition of the term chirality by Lord Kelvin in 1893 and 1904 is analyzed by taking crystallography at that time into account. This shows clearly that chirality is a relational geometric-physical property, i.e., two relations between isometric objects are possible: homochiral or heterochiral. In scientific articles the relational term chirality is often mistaken for the two valued measure for the individual (absolute) sense of chirality, an arbitrary attributive term. © 2013 Wiley Periodicals, Inc.

Study on the determination and chiral inversion of R-salbutamol in human plasma and urine by liquid chromatography-tandem mass spectrometry.

PubMed

Zhou, Ting; Zeng, Jing; Liu, Shan; Zhao, Ting; Wu, Jie; Lai, Wenshi; He, Mingzhi; Xu, Beining; Qu, Shanshan; Xu, Ling; Tan, Wen

2015-10-01

The chiral inversion has been a concerned issue during the research and development of a chiral drug. In this study, a sensitive chiral liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for determination of salbutamol enantiomers in human plasma and urine. The chiral inversion mechanism of R-salbutamol was fully investigated for the first time by studying the effects of physicochemical factors, including pH, temperature and time. A fitted model to predict the chiral inversion ratio of R-salbutamol was proposed using a Box-Behnken design. All the samples were separated on an Astec Chirobiotic T column and detected by a tandem mass spectrometer in multiple reaction monitoring mode. Lower limit of quantification of 0.100ng/mL was achieved under the optimized conditions. The method was fully validated and successfully applied to the clinical pharmacokinetic study of R-salbutamol in healthy volunteers. Chiral inversion of R-salbutamol to S-salbutamol has been detected in urine samples. The results indicated that pH and temperature were two dominant factors that caused the chiral inversion of R-salbutamol, which should be taken into consideration during the analysis of chiral drugs. The chiral inversion of R-salbutamol determined in this study was confirmed resulted from the gastric acid in stomach rather than caused by the analysis conditions. Moreover, the calculated results of the fitted model matched very well with the enantioselective pharmacokinetic study of R-salbutamol, and the individual difference of the chiral inversion ratio of R-salbutamol was related to the individual gastric environment. On the basis of the results, this study provides important and concrete information not only for the chiral analysis but also for the metabolism research of chiral drugs. Copyright © 2015 Elsevier B.V. All rights reserved.

Enantioselective Biotransformation of Chiral Persistent Organic Pollutants.

PubMed

Zhang, Ying; Ye, Jing; Liu, Min

2017-01-01

Enantiomers of chiral compounds commonly undergo enantioselective transformation in most biologically mediated processes. As chiral persistent organic pollutants (POPs) are extensively distributed in the environment, differences between enantiomers in biotransformation should be carefully considered to obtain exact enrichment and specific health risks. This review provides an overview of in vivo biotransformation of chiral POPs currently indicated in the Stockholm Convention and their chiral metabolites. Peer-reviewed journal articles focused on the research question were thoroughly searched. A set of inclusion and exclusion criteria were developed to identify relevant studies. We mainly compared the results from different animal models under controlled laboratory conditions to show the difference between enantiomers in terms of distinct transformation potential. Interactions with enzymes involved in enantioselective biotransformation, especially cytochrome P450 (CYP), were discussed. Further research areas regarding this issue were proposed. Limited evidence for a few POPs has been found in 30 studies. Enantioselective biotransformation of α-hexachlorocyclohexane (α-HCH), chlordane, dichlorodiphenyltrichloroethane (DDT), heptachlor, hexabromocyclododecane (HBCD), polychlorinated biphenyls (PCBs), and toxaphene, has been investigated using laboratory mammal, fish, bird, and worm models. Tissue and excreta distributions, as well as bioaccumulation and elimination kinetics after administration of racemate and pure enantiomers, have been analyzed in these studies. Changes in enantiomeric fractions have been considered as an indicator of enantioselective biotransformation of chiral POPs in most studies. Results of different laboratory animal models revealed that chiral POP biotransformation is seriously affected by chirality. Pronounced results of species-, tissue-, gender-, and individual-dependent differences are observed in in vivo biotransformation of chiral POPs. Enantioselective biotransformation of chiral POPs is dependent on enzyme amounts and activities. However, the role of cytochrome P450 in enantioselective biotransformation has not yet been confirmed. Currently available data on biotransformation of chiral POPs provide a preliminary understanding of the fate of chiral compounds in organisms. Further detailed studies of species-dependent biotransformation pathway and molecular mechanism in various animal models should be performed to comprehensively understand chiral POP biotransformation.

Investigating the nature of chiral near-field interactions

NASA Astrophysics Data System (ADS)

Barr, Lauren E.; Horsley, Simon A. R.; Hooper, Ian R.; Eager, Jake K.; Gallagher, Cameron P.; Hornett, Samuel M.; Hibbins, Alastair P.; Hendry, Euan

2018-04-01

In recent years, there have been reports of enhanced chiroptical interactions in the near-fields of antennas, postulated to be mediated by high spatial gradients in the electromagnetic fields. Here, using gigahertz experimentation, we investigate the nature of the chiral near-field generated by an array of staggered-rod antennas through its interaction with an array of aligned, subwavelength metallic helices. This allows us to eliminate many potential origins of enhancements, such as those associated with plasmon-exciton interactions, and search solely for enhancements due to the high spatial gradients in the chirality of the fields around chiral antennas (so-called `superchiral fields'). By comparing the strength of the chiral interaction with our helices to that of a homogeneous chiral layer with effective material parameters, we find that the strength of this chiral interaction can be predicted using a completely local effective medium approximation. This suggests no obvious enhancement in the chiral interaction in the near-field and indicates that nonlocal interactions are negligible in this system.

Industrial-scale separation of high-purity single-chirality single-wall carbon nanotubes for biological imaging

PubMed Central

Yomogida, Yohei; Tanaka, Takeshi; Zhang, Minfang; Yudasaka, Masako; Wei, Xiaojun; Kataura, Hiromichi

2016-01-01

Single-chirality, single-wall carbon nanotubes are desired due to their inherent physical properties and performance characteristics. Here, we demonstrate a chromatographic separation method based on a newly discovered chirality-selective affinity between carbon nanotubes and a gel containing a mixture of the surfactants. In this system, two different selectivities are found: chiral-angle selectivity and diameter selectivity. Since the chirality of nanotubes is determined by the chiral angle and diameter, combining these independent selectivities leads to high-resolution single-chirality separation with milligram-scale throughput and high purity. Furthermore, we present efficient vascular imaging of mice using separated single-chirality (9,4) nanotubes. Due to efficient absorption and emission, blood vessels can be recognized even with the use of ∼100-fold lower injected dose than the reported value for pristine nanotubes. Thus, 1 day of separation provides material for up to 15,000 imaging experiments, which is acceptable for industrial use. PMID:27350127

Transfer and Dynamic Inversion of Coassembled Supramolecular Chirality through 2D-Sheet to Rolled-Up Tubular Structure.

PubMed

Choi, Heekyoung; Cho, Kang Jin; Seo, Hyowon; Ahn, Junho; Liu, Jinying; Lee, Shim Sung; Kim, Hyungjun; Feng, Chuanliang; Jung, Jong Hwa

2017-12-13

Transfer and inversion of supramolecular chirality from chiral calix[4]arene analogs (3D and 3L) with an alanine moiety to an achiral bipyridine derivative (1) with glycine moieties in a coassembled hydrogel are demonstrated. Molecular chirality of 3D and 3L could transfer supramolecular chirality to an achiral bipyridine derivative 1. Moreover, addition of 0.6 equiv of 3D or 3L to 1 induced supramolecular chirality inversion of 1. More interestingly, the 2D-sheet structure of the coassembled hydrogels formed with 0.2 equiv of 3D or 3L changed to a rolled-up tubular structure in the presence of 0.6 equiv of 3D or 3L. The chirality inversion and morphology change are mainly mediated by intermolecular hydrogen-bonding interactions between the achiral and chiral molecules, which might be induced by reorientations of the assembled molecules, confirmed by density functional theory calculations.

Strong-field control and enhancement of chiral response in bi-elliptical high-order harmonic generation: an analytical model

NASA Astrophysics Data System (ADS)

Ayuso, David; Decleva, Piero; Patchkovskii, Serguei; Smirnova, Olga

2018-06-01

The generation of high-order harmonics in a medium of chiral molecules driven by intense bi-elliptical laser fields can lead to strong chiroptical response in a broad range of harmonic numbers and ellipticities (Ayuso et al 2018 J. Phys. B: At. Mol. Opt. Phys. 51 06LT01). Here we present a comprehensive analytical model that can describe the most relevant features arising in the high-order harmonic spectra of chiral molecules driven by strong bi-elliptical fields. Our model recovers the physical picture underlying chiral high-order harmonic generation (HHG) based on ultrafast chiral hole motion and identifies the rotationally invariant molecular pseudoscalars responsible for chiral dynamics. Using the chiral molecule propylene oxide as an example, we show that one can control and enhance the chiral response in bi-elliptical HHG by tailoring the driving field, in particular by tuning its frequency, intensity and ellipticity, exploiting a suppression mechanism of achiral background based on the linear Stark effect.

Charge/spin supercurrent and the Fulde-Ferrell state induced by crystal deformation in Weyl/Dirac superconductors

NASA Astrophysics Data System (ADS)

Matsushita, Taiki; Liu, Tianyu; Mizushima, Takeshi; Fujimoto, Satoshi

2018-04-01

It has been predicted that emergent chiral magnetic fields can be generated by crystal deformation in Weyl/Dirac metals and superconductors. The emergent fields give rise to chiral anomaly phenomena as in the case of Weyl semimetals with usual electromagnetic fields. Here, we clarify effects of the chiral magnetic field on Cooper pairs in Weyl/Dirac superconductors on the basis of the Ginzburg-Landau equation microscopically derived from the quasiclassical Eilenberger formalism. It is found that Cooper pairs are affected by the emergent chiral magnetic field in a dramatic way, and the pseudo-Lorentz force due to the chiral magnetic field stabilizes the Fulde-Ferrell state and causes a charge/spin supercurrent, which flows parallel to the chiral magnetic field in the case of Weyl/Dirac superconductors. This effect is in analogy with the chiral magnetic effect of Weyl semimetals. In addition, we elucidate that neither Meissner effect nor vortex state due to chiral magnetic fields occurs.

Enantioseparation by Capillary Electrophoresis Using Ionic Liquids as Chiral Selectors.

PubMed

Greño, Maider; Marina, María Luisa; Castro-Puyana, María

2018-11-02

Capillary electrophoresis (CE) is one of the most widely employed analytical techniques to achieve enantiomeric separations. In spite of the fact that there are many chiral selectors commercially available to perform enantioseparations by CE, one of the most relevant topics in this field is the search for new selectors capable of providing high enantiomeric resolutions. Chiral ionic liquids (CILs) have interesting characteristics conferring them a high potential in chiral separations although only some of them are commercially available. The aim of this article is to review all the works published on the use of CILs as chiral selectors in the development of enantioselective methodologies by CE, covering the period from 2006 (when the first research work on this topic was published) to 2017. The use of CILs as sole chiral selectors, as chiral selectors in dual systems or as chiral ligands will be considered. This review also provides detailed analytical information on the experimental conditions used to carry out enantioseparations in different fields as well as on the separation mechanism involved.

Second-order dissipative hydrodynamics for plasma with chiral asymmetry and vorticity

NASA Astrophysics Data System (ADS)

Gorbar, E. V.; Rybalka, D. O.; Shovkovy, I. A.

2017-05-01

By making use of the chiral kinetic theory in the relaxation-time approximation, we derive an Israel-Stewart type formulation of the hydrodynamic equations for a chiral relativistic plasma made of neutral particles (e.g., neutrinos). The effects of chiral asymmetry are captured by including an additional continuity equation for the axial charge, as well as the leading-order quantum corrections due to the spin of particles. In a formulation of the chiral kinetic theory used, we introduce a symmetric form of the energy-momentum tensor that is suitable for the description of a weakly nonuniform chiral plasma. By construction, the energy and momentum are conserved to the same leading order in the Planck constant as the kinetic equation itself. By making use of such a chiral kinetic theory and the Chapman-Enskog approach, we obtain a set of second-order dissipative hydrodynamic equations. The effects of the fluid vorticity and velocity fluctuations on the dispersion relations of chiral vortical waves are analyzed.

Asymmetric Michael Addition Mediated by Chiral Ionic Liquids.

PubMed

Suzuki, Yumiko

2018-06-01

Chiral ionic liquids with a focus on their applications in asymmetric Michael additions and related reactions were reviewed. The examples were classified on the basis of the mode of asymmetric induction (e.g., external induction/non-covalent interaction or internal induction/covalent bond formation), the roles in reactions (as a solvent or catalyst), and their structural features (e.g., imidazolium-based chiral cations, other chiral oniums; proline derivatives). Most of the reactions with high chiral induction are Michael addition of ketones or aldehydes to chalcones or nitrostyrenes where proline-derived chiral ionic liquids catalyze the reaction through enamine/ iminium formation. Many reports demonstrate the recyclability of ionic liquid-tagged pyrrolidines.

Chiral-selective nonlinear optical generation and emission control with plasmonic metamaterials (Conference Presentation)

NASA Astrophysics Data System (ADS)

Cai, Wenshan

2016-09-01

Metamaterials can be designed to exhibit extraordinarily strong chiral responses. Here we present a chiral metamaterial that produces both distinguishable linear and nonlinear features in the visible to near-infrared range. In additional to the gigantic chiral effects in the linear regime, the metamaterial demonstrates a pronounced contrast between second harmonic responses from the two circular polarizations. Linear and nonlinear images probed with circularly polarized lights show strongly defined contrast. Moreover, the chiral centers of the nanometallic structures with enhanced hotspots can be purposely opened for direct access, where emitters occupying the light-confining regions produce chiral-selective enhancement of two-photon luminescence.

Chiral magnetic effect in condensed matter systems

DOE PAGES

Li, Qiang; Kharzeev, Dmitri E.

2016-12-01

The chiral magnetic effect is the generation of electrical current induced by chirality imbalance in the presence of magnetic field. It is a macroscopic manifestation of the quantum anomaly in relativistic field theory of chiral fermions. In the quark-gluon plasma, the axial anomaly induces topological charge changing transition that results in the generation of electrical current along the magnetic field. In condensed matter systems, the chiral magnetic effect was first predicted in the gapless semiconductors with tow energy bands having pointlike degeneracies. In addition, thirty years later after this prediction, the chiral magnetic effect was finally observed in the 3Dmore » Dirac/Weyl semimetals.« less

Split Octonion Reformulation for Electromagnetic Chiral Media of Massive Dyons

NASA Astrophysics Data System (ADS)

Chanyal, B. C.

2017-12-01

In an explicit, unified, and covariant formulation of an octonion algebra, we study and generalize the electromagnetic chiral fields equations of massive dyons with the split octonionic representation. Starting with 2×2 Zorn’s vector matrix realization of split-octonion and its dual Euclidean spaces, we represent the unified structure of split octonionic electric and magnetic induction vectors for chiral media. As such, in present paper, we describe the chiral parameter and pairing constants in terms of split octonionic matrix representation of Drude-Born-Fedorov constitutive relations. We have expressed a split octonionic electromagnetic field vector for chiral media, which exhibits the unified field structure of electric and magnetic chiral fields of dyons. The beauty of split octonionic representation of Zorn vector matrix realization is that, the every scalar and vector components have its own meaning in the generalized chiral electromagnetism of dyons. Correspondingly, we obtained the alternative form of generalized Proca-Maxwell’s equations of massive dyons in chiral media. Furthermore, the continuity equations, Poynting theorem and wave propagation for generalized electromagnetic fields of chiral media of massive dyons are established by split octonionic form of Zorn vector matrix algebra.

Emergence of Chiral Phases in Active Torque Dipole Systems

NASA Astrophysics Data System (ADS)

Fialho, Ana; Tjhung, Elsen; Cates, Michael; Marenduzzo, Davide

The common description of active particles as active force dipoles fails to take into account that active processes in biological systems often exhibit chiral asymmetries, generating active chiral processes and torque dipoles. Examples of such systems include cytoskeleton filaments which interact with motor proteins and beating cilia and flagella. In particular, the generation of active torques by the actomyosin cytoskeleton has been linked to the break of chiral symmetry at a cellular level. This phenomenon could constitute the primary determinant for the break of left-right symmetry in many living organisms, e.g. the position of the human heart within the human body. In order to account for the effects of chirality, we consider active torque dipoles which generate a chiral active stress. We characterize quasi-1D and 2D systems of torque dipoles, using a combination of linear stability analysis and numerical simulations (Lattice Boltzmann). Our results show that activity drives a spontaneous breaking of chiral symmetry, leading to the self-assembly of a chiral phase, in the absence of any thermodynamic interactions favoring cholesteric ordering. At high values of activity, we also observe labyrinthine patterns where the activity-induced chiral ordering is highly frustrated.

Circularly Polarized Luminescence from Inorganic Materials: Encapsulating Guest Lanthanide Oxides in Chiral Silica Hosts.

PubMed

Sugimoto, Masumi; Liu, Xin-Ling; Tsunega, Seiji; Nakajima, Erika; Abe, Shunsuke; Nakashima, Takuya; Kawai, Tsuyoshi; Jin, Ren-Hua

2018-05-02

Recently, circularly polarized luminescence (CPL)-active systems have become a very hot and interesting subject in chirality- and optics-related areas. The CPL-active systems are usually available by two approaches: covalently combining a luminescent centre to chiral motif or associating the guest of luminescent probe to a chiral host. However, all the chiral components in CPL materials were organic, although the luminescent components were alternatively organics or inorganics. Herein, the first totally inorganic CPL-active system by "luminescent guest-chiral host" strategy is proposed. Luminescent sub-10 nm lanthanide oxides (Eu 2 O 3 or Tb 2 O 3 ) nanoparticles (guests) were encapsulated into chiral non-helical SiO 2 nanofibres (host) through calcination of chiral SiO 2 hybrid nanofibres, trapping Eu 3+ (or Tb 3+ ). These lanthanide oxides display circular dichroism (CD) optical activity in the ultraviolet wavelength and CPL signals around at 615 nm for Eu 3+ and 545 nm for Tb 3+ . This work has implications for inorganic-based CPL-active systems by incorporation of various luminescent guests within chiral inorganic hosts. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fluorescent Phthalocyanine Assembly Distinguishes Chiral Isomers of Different Types of Amino Acids and Sugars.

PubMed

Jiang, Yuying; Liu, Chenxi; Wang, Xiqian; Wang, Tianyu; Jiang, Jianzhuang

2017-07-25

The functions of some natural supramolecular architectures, such as ribosomes, are dependent on the recognition of different types of chiral biomolecules. However, the recognition of different types of chiral molecules (multiobject chiral recognition), such as amino acids and sugars, by independent and identically artificial supramolecular assembly, was rarely achieved. In this article, simple amphiphilic achiral phthalocyanine was found to form supramolecular chiral assemblies with charged water-soluble polymers upon host-guest interactions at the air/water interface. Among these systems, one identical phthalocyanine/poly(l-lysine) assembly not only can distinguish enantiomers of different amino acids but also can recognize several epimers of monose. The chiral recognitions were achieved by comparing either the steady-state fluorescence intensity or fluorescence quenching rate of phthalocyanine/poly(l-lysine) assemblies, before and after interaction with different small chiral molecules. It was demonstrated that the interactions between poly(l-lysine) and different small chiral molecules could change the aggregation of phthalocyanines. And the sensitivity of fluorescence and the excellent multiobject chiral recognition properties of the phthalocyanine/poly(l-lysine) assembly are dependent on the subtle molecular packing mode and the cooperation of different noncovalent interactions.

Multiaxial Polarity Determines Individual Cellular and Nuclear Chirality

PubMed Central

Raymond, Michael J.; Ray, Poulomi; Kaur, Gurleen; Fredericks, Michael; Singh, Ajay V.; Wan, Leo Q.

2016-01-01

Intrinsic cell chirality has been implicated in the left-right (LR) asymmetry of embryonic development. Impaired cell chirality could lead to severe birth defects in laterality. Previously, we detected cell chirality with an in vitro micropatterning system. Here, we demonstrate for the first time that chirality can be quantified as the coordination of multiaxial polarization of individual cells and nuclei. Using an object labeling, connected component based method, we characterized cell chirality based on cell and nuclear shape polarization and nuclear positioning of each cell in multicellular patterns of epithelial cells. We found that the cells adopted a LR bias the boundaries by positioning the sharp end towards the leading edge and leaving the nucleus at the rear. This behavior is consistent with the directional migration observed previously on the boundary of micropatterns. Although the nucleus is chirally aligned, it is not strongly biased towards or away from the boundary. As the result of the rear positioning of nuclei, the nuclear positioning has an opposite chirality to that of cell alignment. Overall, our results have revealed deep insights of chiral morphogenesis as the coordination of multiaxial polarization at the cellular and subcellular levels. PMID:28360944

Multiaxial Polarity Determines Individual Cellular and Nuclear Chirality.

PubMed

Raymond, Michael J; Ray, Poulomi; Kaur, Gurleen; Fredericks, Michael; Singh, Ajay V; Wan, Leo Q

2017-02-01

Intrinsic cell chirality has been implicated in the left-right (LR) asymmetry of embryonic development. Impaired cell chirality could lead to severe birth defects in laterality. Previously, we detected cell chirality with an in vitro micropatterning system. Here, we demonstrate for the first time that chirality can be quantified as the coordination of multiaxial polarization of individual cells and nuclei. Using an object labeling, connected component based method, we characterized cell chirality based on cell and nuclear shape polarization and nuclear positioning of each cell in multicellular patterns of epithelial cells. We found that the cells adopted a LR bias the boundaries by positioning the sharp end towards the leading edge and leaving the nucleus at the rear. This behavior is consistent with the directional migration observed previously on the boundary of micropatterns. Although the nucleus is chirally aligned, it is not strongly biased towards or away from the boundary. As the result of the rear positioning of nuclei, the nuclear positioning has an opposite chirality to that of cell alignment. Overall, our results have revealed deep insights of chiral morphogenesis as the coordination of multiaxial polarization at the cellular and subcellular levels.

In situ synthesis of di-n-butyl l-tartrate-boric acid complex chiral selector and its application in chiral microemulsion electrokinetic chromatography.

PubMed

Hu, Shaoqiang; Chen, Yonglei; Zhu, Huadong; Zhu, Jinhua; Yan, Na; Chen, Xingguo

2009-11-06

A novel procedure for in situ assembling a complex chiral selector, di-n-butyl l-tartrate-boric acid complex, by the reaction of di-n-butyl l-tartrate with boric acid in a running buffer was reported and its application in the enantioseparation of beta-blockers and structural related compounds by chiral microemulsion electrokinetic chromatography (MEEKC) has been demonstrated. In order to achieve a good enantioseparation, the effect of dibutyl l-tartrate and sodium tetraborate concentration, surfactant identity and concentration, cosurfactant, buffer pH and composition, organic modifiers, as well as applied voltage and capillary length were investigated. Ten pairs of enantiomers that could not be separated with only dibutyl l-tartrate, obtained good chiral separation using the complex chiral selector; among them, seven pairs could be baseline resolved under optimized experimental conditions. The fixation of chiral centers by the formation of five-membered rings, and being oppositely charged with basic analytes were thought to be the key factors giving the complex chiral selector a superior chiral recognition capability. The effect of the molecular structure of analytes on enantioseparation was discussed in terms of molecular interaction.

ENANTIOMERIC OCCURRENCE AND DISTRIBUTION OF CHIRAL ORGANOCHLORINE COMPOUNDS IN U.S. RIVER SEDIMENT AND BIOTA

EPA Science Inventory

River sediment and biota (fish, bivalves) from throughout the continental U.S. were analyzed for chiral organochlorine compounds (o,p'-DDT and DDD, some chlordane compounds, PCB atropisomers) to assess spatial trends in environmental chirality. Chiral PCB enantiomers were racemic...

Corrigendum to "Co-occurrence of linear and circular dichroism in chiral sculptured ZrO2 thin films" [Opt. Mater. 75 (January 2018) 319-324

NASA Astrophysics Data System (ADS)

Muhammad, Zahir; Wali, Faiz; Song, Li

2018-05-01

The authors regret .

Enantiomeric distribution of some linalool containing essential oils and their biological activities

USDA-ARS?s Scientific Manuscript database

The enantiomeric composition of linalool was determined in 42 essential oils using chiral columns. Essential oils were analyzed by multidimentional gas chromatography-mass spectrometry using a non-chiral and chiral FSC column combination with modified '-cyclodextrine (Lipodex E) as the chiral statio...

Magnetic fields and chiral asymmetry in the early hot universe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sydorenko, Maksym; Shtanov, Yuri; Tomalak, Oleksandr, E-mail: maxsydorenko@gmail.com, E-mail: tomalak@uni-mainz.de, E-mail: shtanov@bitp.kiev.ua

In this paper, we study analytically the process of external generation and subsequent free evolution of the lepton chiral asymmetry and helical magnetic fields in the early hot universe. This process is known to be affected by the Abelian anomaly of the electroweak gauge interactions. As a consequence, chiral asymmetry in the fermion distribution generates magnetic fields of non-zero helicity, and vice versa. We take into account the presence of thermal bath, which serves as a seed for the development of instability in magnetic field in the presence of externally generated lepton chiral asymmetry. The developed helical magnetic field andmore » lepton chiral asymmetry support each other, considerably prolonging their mutual existence, in the process of 'inverse cascade' transferring magnetic-field power from small to large spatial scales. For cosmologically interesting initial conditions, the chiral asymmetry and the energy density of helical magnetic field are shown to evolve by scaling laws, effectively depending on a single combined variable. In this case, the late-time asymptotics of the conformal chiral chemical potential reproduces the universal scaling law previously found in the literature for the system under consideration. This regime is terminated at lower temperatures because of scattering of electrons with chirality change, which exponentially washes out chiral asymmetry. We derive an expression for the termination temperature as a function of the chiral asymmetry and energy density of helical magnetic field.« less

Laminar and Turbulent Dynamos in Chiral Magnetohydrodynamics. II. Simulations

NASA Astrophysics Data System (ADS)

Schober, Jennifer; Rogachevskii, Igor; Brandenburg, Axel; Boyarsky, Alexey; Fröhlich, Jürg; Ruchayskiy, Oleg; Kleeorin, Nathan

2018-05-01

Using direct numerical simulations (DNS), we study laminar and turbulent dynamos in chiral magnetohydrodynamics with an extended set of equations that accounts for an additional contribution to the electric current due to the chiral magnetic effect (CME). This quantum phenomenon originates from an asymmetry between left- and right-handed relativistic fermions in the presence of a magnetic field and gives rise to a chiral dynamo. We show that the magnetic field evolution proceeds in three stages: (1) a small-scale chiral dynamo instability, (2) production of chiral magnetically driven turbulence and excitation of a large-scale dynamo instability due to a new chiral effect (α μ effect), and (3) saturation of magnetic helicity and magnetic field growth controlled by a conservation law for the total chirality. The α μ effect becomes dominant at large fluid and magnetic Reynolds numbers and is not related to kinetic helicity. The growth rate of the large-scale magnetic field and its characteristic scale measured in the numerical simulations agree well with theoretical predictions based on mean-field theory. The previously discussed two-stage chiral magnetic scenario did not include stage (2), during which the characteristic scale of magnetic field variations can increase by many orders of magnitude. Based on the findings from numerical simulations, the relevance of the CME and the chiral effects revealed in the relativistic plasma of the early universe and of proto-neutron stars are discussed.

Magnetic fields and chiral asymmetry in the early hot universe

NASA Astrophysics Data System (ADS)

Sydorenko, Maksym; Tomalak, Oleksandr; Shtanov, Yuri

2016-10-01

In this paper, we study analytically the process of external generation and subsequent free evolution of the lepton chiral asymmetry and helical magnetic fields in the early hot universe. This process is known to be affected by the Abelian anomaly of the electroweak gauge interactions. As a consequence, chiral asymmetry in the fermion distribution generates magnetic fields of non-zero helicity, and vice versa. We take into account the presence of thermal bath, which serves as a seed for the development of instability in magnetic field in the presence of externally generated lepton chiral asymmetry. The developed helical magnetic field and lepton chiral asymmetry support each other, considerably prolonging their mutual existence, in the process of `inverse cascade' transferring magnetic-field power from small to large spatial scales. For cosmologically interesting initial conditions, the chiral asymmetry and the energy density of helical magnetic field are shown to evolve by scaling laws, effectively depending on a single combined variable. In this case, the late-time asymptotics of the conformal chiral chemical potential reproduces the universal scaling law previously found in the literature for the system under consideration. This regime is terminated at lower temperatures because of scattering of electrons with chirality change, which exponentially washes out chiral asymmetry. We derive an expression for the termination temperature as a function of the chiral asymmetry and energy density of helical magnetic field.

Chirality in distorted square planar Pd(O,N)2 compounds.

PubMed

Brunner, Henri; Bodensteiner, Michael; Tsuno, Takashi

2013-10-01

Salicylidenimine palladium(II) complexes trans-Pd(O,N)2 adopt step and bowl arrangements. A stereochemical analysis subdivides 52 compounds into 41 step and 11 bowl types. Step complexes with chiral N-substituents and all the bowl complexes induce chiral distortions in the square planar system, resulting in Δ/Λ configuration of the Pd(O,N)2 unit. In complexes with enantiomerically pure N-substituents ligand chirality entails a specific square chirality and only one diastereomer assembles in the lattice. Dimeric Pd(O,N)2 complexes with bridging N-substituents in trans-arrangement are inherently chiral. For dimers different chirality patterns for the Pd(O,N)2 square are observed. The crystals contain racemates of enantiomers. In complex two independent molecules form a tight pair. The (RC) configuration of the ligand induces the same Δ chirality in the Pd(O,N)2 units of both molecules with varying square chirality due to the different crystallographic location of the independent molecules. In complexes and atrop isomerism induces specific configurations in the Pd(O,N)2 bowl systems. The square chirality is largest for complex [(Diop)Rh(PPh3 )Cl)], a catalyst for enantioselective hydrogenation. In the lattice of two diastereomers with the same (RC ,RC) configuration in the ligand Diop but opposite Δ and Λ square configurations co-crystallize, a rare phenomenon in stereochemistry. © 2013 Wiley Periodicals, Inc.

The chiral magnetic effect and chiral symmetry breaking in SU(3) quenched lattice gauge theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Braguta, V. V., E-mail: braguta@mail.ru; Buividovich, P. V., E-mail: buividovich@itep.ru; Kalaydzhyan, T., E-mail: tigran.kalaydzhyan@desy.de

2012-04-15

We study some properties of the non-Abelian vacuum induced by strong external magnetic field. We perform calculations in the quenched SU(3) lattice gauge theory with tadpole-improved Luescher-Weisz action and chirally invariant lattice Dirac operator. The following results are obtained: The chiral symmetry breaking is enhanced by the magnetic field. The chiral condensate depends on the strength of the applied field as a power function with exponent {nu} = 1.6 {+-} 0.2. There is a paramagnetic polarization of the vacuum. The corresponding susceptibility and other magnetic properties are calculated and compared with the theoretical estimations. There are nonzero local fluctuations ofmore » the chirality and electromagnetic current, which grow with the magnetic field strength. These fluctuations can be a manifestation of the Chiral Magnetic Effect.« less

Spin-Wave Chirality and Its Manifestations in Antiferromagnets

NASA Astrophysics Data System (ADS)

Proskurin, Igor; Stamps, Robert L.; Ovchinnikov, Alexander S.; Kishine, Jun-ichiro

2017-10-01

As first demonstrated by Tang and Cohen in chiral optics, the asymmetry in the rate of electromagnetic energy absorption between left and right enantiomers is determined by an optical chirality density. Here, we demonstrate that this effect can exist in magnetic spin systems. By constructing a formal analogy with electrodynamics, we show that in antiferromagnets with broken chiral symmetry, the asymmetry in local spin-wave energy absorption is proportional to a spin-wave chirality density, which is a direct counterpart of optical zilch. We propose that injection of a pure spin current into an antiferromagnet may serve as a chiral symmetry breaking mechanism, since its effect in the spin-wave approximation can be expressed in terms of additional Lifshitz invariants. We use linear response theory to show that the spin current induces a nonequilibrium spin-wave chirality density.

Stoichiometry-Controlled Inversion of Supramolecular Chirality in Nanostructures Co-assembled with Bipyridines.

PubMed

Wang, Fang; Feng, Chuan-Liang

2018-02-01

To control supramolecular chirality of the co-assembled nanostructures, one of the remaining issues is how stoichiometry of the different molecules involved in co-assembly influence chiral transformation. Through co-assembly of achiral 1,4-bis(pyrid-4-yl)benzene and chiral phenylalanine-glycine derivative hydrogelators, stoichiometry is found to be an effective tool for controlling supramolecular chirality inversion processes. This inversion is mainly mediated by a delicate balance between intermolecular hydrogen bonding interactions and π-π stacking of the two components, which may subtly change the stacking of the molecules, in turn, the self-assembled nanostructures. This study exemplifies a simplistic way to invert the handedness of chiral nanostructures and provide fundamental understanding of the inherent principles of supramolecular chirality. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chiral Responsive Liquid Quantum Dots.

PubMed

Zhang, Jin; Ma, Junkai; Shi, Fangdan; Tian, Demei; Li, Haibing

2017-08-01

How to convert the weak chiral-interaction into the macroscopic properties of materials remains a huge challenge. Here, this study develops highly fluorescent, selectively chiral-responsive liquid quantum dots (liquid QDs) based on the hydrophobic interaction between the chiral chains and the oleic acid-stabilized QDs, which have been designated as (S)-1810-QDs. The fluorescence spectrum and liquidity of thermal control demonstrate the fluorescence properties and the fluidic behavior of (S)-1810-QDs in the solvent-free state. Especially, (S)-1810-QDs exhibit a highly chiral-selective response toward (1R, 2S)-2-amino-1,2-diphenyl ethanol. It is anticipated that this study will facilitate the construction of smart chiral fluidic sensors. More importantly, (S)-1810-QDs can become an attractive material for chiral separation. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Application of Δ- and λ-isomerism of octahedral metal complexes for inducing chiral nematic phases.

PubMed

Sato, Hisako; Yamagishi, Akihiko

2009-11-20

The Delta- and Lambda-isomerism of octahedral metal complexes is employed as a source of chirality for inducing chiral nematic phases. By applying a wide range of chiral metal complexes as a dopant, it has been found that tris(beta-diketonato)metal(III) complexes exhibit an extremely high value of helical twisting power. The mechanism of induction of the chiral nematic phase is postulated on the basis of a surface chirality model. The strategy for designing an efficient dopant is described, together with the results using a number of examples of Co(III), Cr(III) and Ru(III) complexes with C(2) symmetry. The development of photo-responsive dopants to achieve the photo-induced structural change of liquid crystal by use of photo-isomerization of chiral metal complexes is also described.

Application of Δ- and Λ-Isomerism of Octahedral Metal Complexes for Inducing Chiral Nematic Phases

PubMed Central

Sato, Hisako; Yamagishi, Akihiko

2009-01-01

The Δ- and Λ-isomerism of octahedral metal complexes is employed as a source of chirality for inducing chiral nematic phases. By applying a wide range of chiral metal complexes as a dopant, it has been found that tris(β-diketonato)metal(III) complexes exhibit an extremely high value of helical twisting power. The mechanism of induction of the chiral nematic phase is postulated on the basis of a surface chirality model. The strategy for designing an efficient dopant is described, together with the results using a number of examples of Co(III), Cr(III) and Ru(III) complexes with C2 symmetry. The development of photo-responsive dopants to achieve the photo-induced structural change of liquid crystal by use of photo-isomerization of chiral metal complexes is also described. PMID:20057959

Chirality controlled responsive self-assembled nanotubes in water† †Electronic supplementary information (ESI) available: Detailed experimental procedures and analyses, UV-vis absorption and CD spectroscopy, cryo-TEM and widefield microscopy. See DOI: 10.1039/c6sc02935c Click here for additional data file.

PubMed Central

van Dijken, D. J.; Štacko, P.; Stuart, M. C. A.; Browne, W. R.

2017-01-01

The concept of using chirality to dictate dimensions and to store chiral information in self-assembled nanotubes in a fully controlled manner is presented. We report a photoresponsive amphiphile that co-assembles with its chiral counterpart to form nanotubes and demonstrate how chirality can be used to effect the formation of either micrometer long, achiral nanotubes or shorter (∼300 nm) chiral nanotubes that are bundled. The nature of these assemblies is studied using a variety of spectroscopic and microscopic techniques and it is shown that the tubes can be disassembled with light, thereby allowing the chiral information to be erased. PMID:28451300

Asymmetric synthesis using chiral-encoded metal

NASA Astrophysics Data System (ADS)

Yutthalekha, Thittaya; Wattanakit, Chularat; Lapeyre, Veronique; Nokbin, Somkiat; Warakulwit, Chompunuch; Limtrakul, Jumras; Kuhn, Alexander

2016-08-01

The synthesis of chiral compounds is of crucial importance in many areas of society and science, including medicine, biology, chemistry, biotechnology and agriculture. Thus, there is a fundamental interest in developing new approaches for the selective production of enantiomers. Here we report the use of mesoporous metal structures with encoded geometric chiral information for inducing asymmetry in the electrochemical synthesis of mandelic acid as a model molecule. The chiral-encoded mesoporous metal, obtained by the electrochemical reduction of platinum salts in the presence of a liquid crystal phase and the chiral template molecule, perfectly retains the chiral information after removal of the template. Starting from a prochiral compound we demonstrate enantiomeric excess of the (R)-enantiomer when using (R)-imprinted electrodes and vice versa for the (S)-imprinted ones. Moreover, changing the amount of chiral cavities in the material allows tuning the enantioselectivity.

Chiral electroweak currents in nuclei

DOE PAGES

Riska, D. O.; Schiavilla, R.

2017-01-10

Here, the development of the chiral dynamics based description of nuclear electroweak currents is reviewed. Gerald E. (Gerry) Brown’s role in basing theoretical nuclear physics on chiral Lagrangians is emphasized. Illustrative examples of the successful description of electroweak observables of light nuclei obtained from chiral effective field theory are presented.

Chiral pesticides: identification, description, and environmental implications.

PubMed

Ulrich, Elin M; Morrison, Candice N; Goldsmith, Michael R; Foreman, William T

2012-01-01

Of the 1,693 pesticides considered in this review, 1,594 are organic chemicals, 47 are inorganic chemicals, 53 are of biological origin (largely non chemical; insect,fungus, bacteria, virus, etc.), and 2 have an undetermined structure. Considering that the EPA's Office of Pesticide Programs found 1,252 pesticide active ingredients(EPA Pesticides Customer Service 2011), we consider this dataset to be comprehensive; however, no direct comparison of the compound lists was undertaken. Of all pesticides reviewed, 482 (28%) are chiral; 30% are chiral when considering only the organic chemical pesticides. A graph of this distribution is shown in Fig. 7a. Each pesticide is classified with up to three pesticidal utilities (e.g., fungicide, plant growth regulator, rodenticide, etc.), taken first from the Pesticide Manual as a primary source, and the Compendium of Common Pesticide Names website as a secondary source. Of the chiral pesticides, 195 (34%) are insecticides (including attractants, pheromones, and repellents), 150 (27%) are herbicides (including plant growth regulators and herbicide safeners), 104 (18%) are fungicides, and 55 (10%)are acaricides. The distribution of chiral pesticides by utility is shown in Fig. 7b,including categories of pesticides that make up 3%t or less of the usage categories.Figure 7c shows a similar distribution of non chiral pesticide usage categories. Of the chiral pesticides, 270 (56%) have one chiral feature, 105 (22%) have two chiral features, 30 (6.2%) have three chiral features, and 29 (6.0%) have ten or more chiral features.Chiral chemicals pose many difficulties in stereospecific synthesis, characterization, and analysis. When these compounds are purposely put into the environment,even more interesting complications arise in tracking, monitoring, and predicting their fate and risks. More than 475 pesticides are chiral, as are other chiral contaminants such as pharmaceuticals, polychlorinated biphenyls, brominated flame retardants, synthetic musks, and their degradates (Kallenborn and Hiihnerfuss 2001;Heeb et al. 2007; Hihnerfuss and Shah 2009). The stereoisomers of pesticides can have widely different efficacy, toxicity to nontarget organisms, and metabolic rates in biota. For these reasons, it is important to first be aware of likely fate and effect differences, to incorporate molecular asymmetry insights into research projects, and to study the individual stereoisomers of the applied pesticide material.With the advent of enantioselective chromatography techniques, the chirality of pesticides has been increasingly studied. While the ChirBase (Advanced ChemistryDevelopment 1997-2010) database does not include all published chiral analytical separations, it does contain more than 3,500 records for 146 of the 482 chiral pesticides (30%). The majority of the records are found in the liquid chromatography database (2,677 or 76%), followed by the gas chromatography database (652 or 18%),and the capillary electrophoresis database (203 or 6%). The finding that only 30% of the chiral pesticides covered in this review have entries in ChirBase highlights the need for expanded efforts to develop additional enantioselective chromatographic methods. Other techniques (e.g., nuclear magnetic resonance and other spectroscopy)are available for investigation of chiral compounds, but often are not utilized because of cost, complexity, or simply not recognizing that a pesticide is chiral.In this review, we have listed and have briefly described the general nature of chiral fungicides, herbicides, insecticides, and other miscellaneous classes. A data-set generated for this review contains 1,693 pesticides, the number of enantioselective separation records in ChirBase, pesticide usage class, SMILES structure string and counts of stereogenic centers. This dataset is publically available for download at the following website: http://www.epa.gov/heasd/products/products.html. With the information herein coupled to the publically accessible dataset, we can begin to develop the tools to handle molecular asymmetry as it applies to agrochemicals.Additional structure-based resources would allow further analysis of key parameters (e.g., exposure, toxicity, environmental fate, degradation, and risks) for individual stereoisomers of chiral compounds.

A novel aggregation-induced emission enhancement triggered by the assembly of a chiral gelator: from non-emissive nanofibers to emissive micro-loops.

PubMed

Chen, Wenrui; Qing, Guangyan; Sun, Taolei

2016-12-22

In this study, a novel aggregation-induced emission (AIE) enhancement triggered by the self-assembly of chiral gelator is described. Tuning of molecular chirality in situ triggers different assemblies of superstructures exhibiting fluorescence. This novel AIE material can constitute an emerging library of chiral supramolecules for turn-on fluorescent sensors. It will also help in better understanding the effects of chiral factors on the photophysical process.

Construction of axial chirality by rhodium-catalyzed asymmetric dehydrogenative Heck coupling of biaryl compounds with alkenes.

PubMed

Zheng, Jun; You, Shu-Li

2014-11-24

Enantioselective construction of axially chiral biaryls by direct C-H bond functionalization reactions has been realized. Novel axially chiral biaryls were synthesized by the direct C-H bond olefination of biaryl compounds, using a chiral [Cp*Rh(III)] catalyst, in good to excellent yields and enantioselectivities. The obtained axially chiral biaryls were found as suitable ligands for rhodium-catalyzed asymmetric conjugate additions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterizing optical chirality

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bliokh, Konstantin Y.; Advanced Science Institute, RIKEN, Wako-shi, Saitama 351-0198; Nori, Franco

We examine the recently introduced measure of chirality of a monochromatic optical field [Y. Tang and A. E. Cohen, Phys. Rev. Lett. 104, 163901 (2010)] using the momentum (plane-wave) representation and helicity basis. Our analysis clarifies the physical meaning of the measure of chirality and unveils its close relation to the polarization helicity, spin angular momentum, energy density, and Poynting energy flow. We derive the operators of the optical chirality and of the corresponding chiral momentum, which acquire remarkably simple forms in the helicity representation.

Theory of magnetoelastic resonance in a monoaxial chiral helimagnet

NASA Astrophysics Data System (ADS)

Tereshchenko, A. A.; Ovchinnikov, A. S.; Proskurin, Igor; Sinitsyn, E. V.; Kishine, Jun-ichiro

2018-05-01

We study magnetoelastic resonance phenomena in a monoaxial chiral helimagnet belonging to the hexagonal crystal class. By computing the spectrum of a coupled elastic wave and spin wave, it is demonstrated how hybridization occurs depending on their chirality. Specific features of the magnetoelastic resonance are discussed for the conical phase and the soliton lattice phase stabilized in the monoaxial chiral helimagnet. The former phase exhibits appreciable nonreciprocity of the spectrum, and the latter is characterized by a multiresonance behavior. We propose that the nonreciprocal spin wave around the forced-ferromagnetic state has potential capability to convert the linearly polarized elastic wave to a circularly polarized one with the chirality opposite to the spin-wave chirality.

Asymmetric Michael Addition Mediated by Chiral Ionic Liquids

PubMed Central

Suzuki, Yumiko

2018-01-01

Chiral ionic liquids with a focus on their applications in asymmetric Michael additions and related reactions were reviewed. The examples were classified on the basis of the mode of asymmetric induction (e.g., external induction/non-covalent interaction or internal induction/covalent bond formation), the roles in reactions (as a solvent or catalyst), and their structural features (e.g., imidazolium-based chiral cations, other chiral oniums; proline derivatives). Most of the reactions with high chiral induction are Michael addition of ketones or aldehydes to chalcones or nitrostyrenes where proline-derived chiral ionic liquids catalyze the reaction through enamine/ iminium formation. Many reports demonstrate the recyclability of ionic liquid-tagged pyrrolidines. PMID:29861702

A complex-polarization-propagator protocol for magneto-chiral axial dichroism and birefringence dispersion.

PubMed

Cukras, Janusz; Kauczor, Joanna; Norman, Patrick; Rizzo, Antonio; Rikken, Geert L J A; Coriani, Sonia

2016-05-21

A computational protocol for magneto-chiral dichroism and magneto-chiral birefringence dispersion is presented within the framework of damped response theory, also known as complex polarization propagator theory, at the level of time-dependent Hartree-Fock and time-dependent density functional theory. Magneto-chiral dichroism and magneto-chiral birefringence spectra in the (resonant) frequency region below the first ionization threshold of R-methyloxirane and l-alanine are presented and compared with the corresponding results obtained for both the electronic circular dichroism and the magnetic circular dichroism. The additional information content yielded by the magneto-chiral phenomena, as well as their potential experimental detectability for the selected species, is discussed.

Chiroptical studies on supramolecular chirality of molecular aggregates.

PubMed

Sato, Hisako; Yajima, Tomoko; Yamagishi, Akihiko

2015-10-01

The attempts of applying chiroptical spectroscopy to supramolecular chirality are reviewed with a focus on vibrational circular dichroism (VCD). Examples were taken from gels, solids, and monolayers formed by low-molecular mass weight chiral gelators. Particular attention was paid to a group of gelators with perfluoroalkyl chains. The effects of the helical conformation of the perfluoroalkyl chains on the formation of chiral architectures are reported. It is described how the conformation of a chiral gelator was determined by comparing the experimental and theoretical VCD spectra together with a model proposed for the molecular aggregation in fibrils. The results demonstrate the potential utility of the chiroptical method in analyzing organized chiral aggregates. © 2015 Wiley Periodicals, Inc.

Visualization of Stereoselective Supramolecular Polymers by Chirality-Controlled Energy Transfer.

PubMed

Sarkar, Aritra; Dhiman, Shikha; Chalishazar, Aditya; George, Subi J

2017-10-23

Chirality-driven self-sorting is envisaged to efficiently control functional properties in supramolecular materials. However, the challenge arises because of a lack of analytical methods to directly monitor the enantioselectivity of the resulting supramolecular assemblies. Presented herein are two fluorescent core-substituted naphthalene-diimide-based donor and acceptor molecules with minimal structural mismatch and they comprise strong self-recognizing chiral motifs to determine the self-sorting process. As a consequence, stereoselective supramolecular polymerization with an unprecedented chirality control over energy transfer has been achieved. This chirality-controlled energy transfer has been further exploited as an efficient probe to visualize microscopically the chirality driven self-sorting. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Metal-Ion-Mediated Supramolecular Chirality of l-Phenylalanine Based Hydrogels.

PubMed

Wang, Fang; Feng, Chuan-Liang

2018-05-14

For chiral hydrogels and related applications, one of the critical issues is how to control the chirality of supramolecular systems in an efficient way, including easy operation, efficient transfer of chirality, and so on. Herein, supramolecular chirality of l-phenylalanine based hydrogels can be effectively controlled by using a broad range of metal ions. The degree of twisting (twist pitch) and the diameter of the chiral nanostructures can also be efficiently regulated. These are ascribed to the synergic effect of hydrogen bonding and metal ion coordination. This study may develop a method to design a new class of electronically, optically, and biologically active materials. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Observation of chiral phonons

NASA Astrophysics Data System (ADS)

Zhu, Hanyu; Yi, Jun; Li, Ming-Yang; Xiao, Jun; Zhang, Lifa; Yang, Chih-Wen; Kaindl, Robert A.; Li, Lain-Jong; Wang, Yuan; Zhang, Xiang

2018-02-01

Chirality reveals symmetry breaking of the fundamental interaction of elementary particles. In condensed matter, for example, the chirality of electrons governs many unconventional transport phenomena such as the quantum Hall effect. Here we show that phonons can exhibit intrinsic chirality in monolayer tungsten diselenide. The broken inversion symmetry of the lattice lifts the degeneracy of clockwise and counterclockwise phonon modes at the corners of the Brillouin zone. We identified the phonons by the intervalley transfer of holes through hole-phonon interactions during the indirect infrared absorption, and we confirmed their chirality by the infrared circular dichroism arising from pseudoangular momentum conservation. The chiral phonons are important for electron-phonon coupling in solids, phonon-driven topological states, and energy-efficient information processing.

Enantioselective Synthesis of 5,7-Bicyclic Ring Systems from Axially Chiral Allenes Using a Rh(I)-Catalyzed Cyclocarbonylation Reaction

PubMed Central

Grillet, Francois; Brummond, Kay M.

2013-01-01

A transfer of chirality in an intramolecular Rh(I)-catalyzed allenic Pauson-Khand reaction (APKR) to access tetrahydroazulenones, tetrahydrocyclopenta[c]azepinones and dihydrocyclopenta[c]oxepinones enantioselectively (22 – 99% ee) is described. The substitution pattern of the allene affected the transfer of chiral information. Complete transfer of chirality was obtained for all trisubstituted allenes, but loss of chiral information was observed for disubstituted allenes. This work constitutes the first demonstration of a transfer of chiral information from an allene to the 5-position of a cyclopentenone using a cyclocarbonylation reaction. The absolute configuration of the corresponding cyclocarbonylation product was also established, something that is rarely done. PMID:23485149

Through-space transfer of chiral information mediated by a plasmonic nanomaterial

NASA Astrophysics Data System (ADS)

Ostovar Pour, Saeideh; Rocks, Louise; Faulds, Karen; Graham, Duncan; Parchaňský, Václav; Bouř, Petr; Blanch, Ewan W.

2015-07-01

The ability to detect chirality gives stereochemically attuned nanosensors the potential to revolutionize the study of biomolecular processes. Such devices may structurally characterize the mechanisms of protein-ligand binding, the intermediates of amyloidogenic diseases and the effects of phosphorylation and glycosylation. We demonstrate that single nanoparticle plasmonic reporters, or nanotags, can enable a stereochemical response to be transmitted from a chiral analyte to an achiral benzotriazole dye molecule in the vicinity of a plasmon resonance from an achiral metallic nanostructure. The transfer of chirality was verified by the measurement of mirror image surface enhanced resonance Raman optical activity spectra for the two enantiomers of both ribose and tryptophan. Computational modelling confirms these observations and reveals the novel chirality transfer mechanism responsible. This is the first report of colloidal metal nanoparticles in the form of single plasmonic substrates displaying an intrinsic chiral sensitivity once attached to a chiral molecule.

Molecular chirality: language, history, and significance.

PubMed

Gal, Joseph

2013-01-01

In this chapter some background material concerning molecular chirality and enantiomerism is presented. First some basic chemical-molecular aspects of chirality are reviewed, after which certain relevant terminology whose use in the literature has been problematic is discussed. Then an overview is provided of some of the early discoveries that laid the foundations of the science of molecular chirality in chemistry and biology, including the discovery of the phenomenon of molecular chirality by L. Pasteur, the proposals for the asymmetric carbon atom by J.H. van 't Hoff and J.A. Lebel, Pasteur's discovery of biological enantioselectivity, the discovery of enantioselectivity at biological receptors by A. Piutti, the studies of enzymatic stereoselectivity by E. Fischer, and the work on enantioselectivity in pharmacology by A. Cushny. Finally, the role of molecular chirality in pharmacotherapy and new-drug development, arguably one of the main driving forces for the current intense interest in the phenomenon of molecular chirality, is discussed.

Stable Pentaquarks from Strange Chiral Multiplets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silas Beane

2004-12-01

The assumption of strong diquark correlations in the QCD spectrum suggests flavor multiplets of hadrons that are degenerate in the chiral limit. Generally it would be unnatural for there to be degeneracy in the hadron spectrum that is not protected by a QCD symmetry. Here we show--for pentaquarks constructed from diquarks--that these degeneracies can be naturally protected by the full chiral symmetry of QCD. The resulting chiral multiplet structure recovers the ideally-mixed pentaquark mass spectrum of the diquark model, and interestingly, requires that the axial couplings of the pentaquarks to states outside the degenerate multiplets vanish in the chiral limit.more » This result suggests that if these hadrons exist, they are stable in the chiral limit and therefore have widths that scale as the fourth power of the kaon mass over the chiral symmetry breaking scale. Natural-size widths are of order a few MeV.« less

A molecular propeller effect for chiral separation and analysis

PubMed Central

Clemens, Jonathon B.; Kibar, Osman; Chachisvilis, Mirianas

2015-01-01

Enantiomers share nearly identical physical properties but have different chiral geometries, making their identification and separation difficult. Here we show that when exposed to a rotating electric field, the left- and right-handed chiral molecules rotate with the field and act as microscopic propellers; moreover, owing to their opposite handedness, they propel along the axis of field rotation in opposite directions. We introduce a new molecular parameter called hydrodynamic chirality to characterize the coupling of rotational motion of a chiral molecule into its translational motion and quantify the direction and velocity of such motion. We demonstrate >80% enrichment level of counterpart enantiomers in solution without using chiral selectors or circularly polarized light. We expect our results to have an impact on multiple applications in drug discovery, analytical and chiral chemistry, including determination of absolute configuration, as well as in influencing the understanding of artificial and natural molecular systems where rotational motion of the molecules is involved. PMID:26216219

One-Dimensional Chirality: Strong Optical Activity in Epsilon-Near-Zero Metamaterials.

PubMed

Rizza, Carlo; Di Falco, Andrea; Scalora, Michael; Ciattoni, Alessandro

2015-07-31

We suggest that electromagnetic chirality, generally displayed by 3D or 2D complex chiral structures, can occur in 1D patterned composites whose components are achiral. This feature is highly unexpected in a 1D system which is geometrically achiral since its mirror image can always be superposed onto it by a 180 deg rotation. We analytically evaluate from first principles the bianisotropic response of multilayered metamaterials and we show that the chiral tensor is not vanishing if the system is geometrically one-dimensional chiral; i.e., its mirror image cannot be superposed onto it by using translations without resorting to rotations. As a signature of 1D chirality, we show that 1D chiral metamaterials support optical activity and we prove that this phenomenon undergoes a dramatic nonresonant enhancement in the epsilon-near-zero regime where the magnetoelectric coupling can become dominant in the constitutive relations.

Enantioselective recognition at mesoporous chiral metal surfaces.

PubMed

Wattanakit, Chularat; Côme, Yémima Bon Saint; Lapeyre, Veronique; Bopp, Philippe A; Heim, Matthias; Yadnum, Sudarat; Nokbin, Somkiat; Warakulwit, Chompunuch; Limtrakul, Jumras; Kuhn, Alexander

2014-01-01

Chirality is widespread in natural systems, and artificial reproduction of chiral recognition is a major scientific challenge, especially owing to various potential applications ranging from catalysis to sensing and separation science. In this context, molecular imprinting is a well-known approach for generating materials with enantioselective properties, and it has been successfully employed using polymers. However, it is particularly difficult to synthesize chiral metal matrices by this method. Here we report the fabrication of a chirally imprinted mesoporous metal, obtained by the electrochemical reduction of platinum salts in the presence of a liquid crystal phase and chiral template molecules. The porous platinum retains a chiral character after removal of the template molecules. A matrix obtained in this way exhibits a large active surface area due to its mesoporosity, and also shows a significant discrimination between two enantiomers, when they are probed using such materials as electrodes.

Chirality-Discriminated Conductivity of Metal-Amino Acid Biocoordination Polymer Nanowires.

PubMed

Zheng, Jianzhong; Wu, Yijin; Deng, Ke; He, Meng; He, Liangcan; Cao, Jing; Zhang, Xugang; Liu, Yaling; Li, Shunxing; Tang, Zhiyong

2016-09-27

Biocoordination polymer (BCP) nanowires are successfully constructed through self-assembly of chiral cysteine amino acids and Cd cations in solution. The varied chirality of cysteine is explored to demonstrate the difference of BCP nanowires in both morphology and structure. More interestingly and surprisingly, the electrical property measurement reveals that, although all Cd(II)/cysteine BCP nanowires behave as semiconductors, the conductivity of the Cd(II)/dl-cysteine nanowires is 4 times higher than that of the Cd(II)/l-cysteine or Cd(II)/d-cysteine ones. The origin of such chirality-discriminated characteristics registered in BCP nanowires is further elucidated by theoretical calculation. These findings demonstrate that the morphology, structure, and property of BCP nanostructures could be tuned by the chirality of the bridging ligands, which will shed light on the comprehension of chirality transcription as well as construction of chirality-regulated functional materials.

Chiral magnetic effect of light

NASA Astrophysics Data System (ADS)

Hayata, Tomoya

2018-05-01

We study a photonic analog of the chiral magnetic (vortical) effect. We discuss that the vector component of magnetoelectric tensors plays a role of "vector potential," and its rotation is understood as "magnetic field" of a light. Using the geometrical optics approximation, we show that "magnetic fields" cause an anomalous shift of a wave packet of a light through an interplay with the Berry curvature of photons. The mechanism is the same as that of the chiral magnetic (vortical) effect of a chiral fermion, so that we term the anomalous shift "chiral magnetic effect of a light." We further study the chiral magnetic effect of a light beyond geometric optics by directly solving the transmission problem of a wave packet at a surface of a magnetoelectric material. We show that the experimental signal of the chiral magnetic effect of a light is the nonvanishing of transverse displacements for the beam normally incident to a magnetoelectric material.

Real-Space Mapping of the Chiral Near-Field Distributions in Spiral Antennas and Planar Metasurfaces.

PubMed

Schnell, M; Sarriugarte, P; Neuman, T; Khanikaev, A B; Shvets, G; Aizpurua, J; Hillenbrand, R

2016-01-13

Chiral antennas and metasurfaces can be designed to react differently to left- and right-handed circularly polarized light, which enables novel optical properties such as giant optical activity and negative refraction. Here, we demonstrate that the underlying chiral near-field distributions can be directly mapped with scattering-type scanning near-field optical microscopy employing circularly polarized illumination. We apply our technique to visualize, for the first time, the circular-polarization selective nanofocusing of infrared light in Archimedean spiral antennas, and explain this chiral optical effect by directional launching of traveling waves in analogy to antenna theory. Moreover, we near-field image single-layer rosette and asymmetric dipole-monopole metasurfaces and find negligible and strong chiral optical near-field contrast, respectively. Our technique paves the way for near-field characterization of optical chirality in metal nanostructures, which will be essential for the future development of chiral antennas and metasurfaces and their applications.

High-performance liquid chromatographic separations of stereoisomers of chiral basic agrochemicals with polysaccharide-based chiral columns and polar organic mobile phases.

PubMed

Matarashvili, Iza; Shvangiradze, Iamze; Chankvetadze, Lali; Sidamonidze, Shota; Takaishvili, Nino; Farkas, Tivadar; Chankvetadze, Bezhan

2015-12-01

The separation of the stereoisomers of 23 chiral basic agrochemicals was studied on six different polysaccharide-based chiral columns in high-performance liquid chromatography with various polar organic mobile phases. Along with the successful separation of analyte stereoisomers, emphasis was placed on the effect of the chiral selector and mobile phase composition on the elution order of stereoisomers. The interesting phenomenon of reversal of enantiomer/stereoisomer elution order function of the polysaccharide backbone (cellulose or amylose), type of derivative (carbamate or benzoate), nature, and position of the substituent(s) in the phenylcarbamate moiety (methyl or chloro) and the nature of the mobile phase was observed. For several of the analytes containing two chiral centers all four stereoisomers were resolved with at least one chiral selector/mobile phase combination. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chiral metamirrors for broadband spin-selective absorption

NASA Astrophysics Data System (ADS)

Jing, Liqiao; Wang, Zuojia; Yang, Yihao; Zheng, Bin; Liu, Yongmin; Chen, Hongsheng

2017-06-01

Chiral metamirrors are recently proposed metadevices that have the ability of selective reflection for the designated circularly polarized waves. However, previous chiral metamirrors only work in a narrow band, which would limit their potential applications in engineering. Here, we propose an approach towards broadband spin-selective absorption. By combining the chiral resonant modes of two asymmetric split-ring resonators, we design and construct a chiral metamirror that absorbs only the left-handed circularly waves over a broad frequency range. The measured results show a bandwidth of 5.1%, almost 96% larger than that of the narrowband metamirror. Furthermore, the proposed chiral metamirror exhibits prominent performance at oblique incidence, even when high-order diffraction appears. The total thickness of the metamirror is only one-ninth of the wavelength, highly suitable for on-chip integration. Our findings may provide an efficient approach to boost the working bandwidth of the chiral metamirror and could advance its applications in optical instruments.

Advances in chiral separations by nonaqueous capillary electrophoresis in pharmaceutical and biomedical analysis.

PubMed

Ali, Imran; Sanagi, Mohd Marsin; Aboul-Enein, Hassan Y

2014-04-01

NACE is an alternative technique to aqueous CE in the chiral separations of partially soluble racemates. Besides, partially water-soluble or insoluble chiral selectors may be exploited in the enantiomeric resolution in NACE. The high reproducibility due to low Joule heat generation and no change in BGE concentration may make NACE a routine analytical technique. These facts attracted scientists to use NACE for the chiral resolution. The present review describes the advances in the chiral separations by NACE and its application in pharmaceutical and biomedical analysis. The emphasis has been given to discuss the selection of the chiral selectors and organic solvents, applications of NACE, comparison between NACE and aqueous CE, and chiral recognition mechanism. Besides, efforts have also been made to predict the future perspectives of NACE. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A molecular propeller effect for chiral separation and analysis

NASA Astrophysics Data System (ADS)

Clemens, Jonathon B.; Kibar, Osman; Chachisvilis, Mirianas

2015-07-01

Enantiomers share nearly identical physical properties but have different chiral geometries, making their identification and separation difficult. Here we show that when exposed to a rotating electric field, the left- and right-handed chiral molecules rotate with the field and act as microscopic propellers; moreover, owing to their opposite handedness, they propel along the axis of field rotation in opposite directions. We introduce a new molecular parameter called hydrodynamic chirality to characterize the coupling of rotational motion of a chiral molecule into its translational motion and quantify the direction and velocity of such motion. We demonstrate >80% enrichment level of counterpart enantiomers in solution without using chiral selectors or circularly polarized light. We expect our results to have an impact on multiple applications in drug discovery, analytical and chiral chemistry, including determination of absolute configuration, as well as in influencing the understanding of artificial and natural molecular systems where rotational motion of the molecules is involved.

Quantized Chiral Magnetic Current from Reconnections of Magnetic Flux.

PubMed

Hirono, Yuji; Kharzeev, Dmitri E; Yin, Yi

2016-10-21

We introduce a new mechanism for the chiral magnetic effect that does not require an initial chirality imbalance. The chiral magnetic current is generated by reconnections of magnetic flux that change the magnetic helicity of the system. The resulting current is entirely determined by the change of magnetic helicity, and it is quantized.

Quantized Chiral Magnetic Current from Reconnections of Magnetic Flux

DOE PAGES

Hirono, Yuji; Kharzeev, Dmitri E.; Yin, Yi

2016-10-20

We introduce a new mechanism for the chiral magnetic e ect that does not require an initial chirality imbalance. The chiral magnetic current is generated by reconnections of magnetic ux that change the magnetic helicity of the system. The resulting current is entirely determined by the change of magnetic helicity, and it is quantized.

Cell chirality: emergence of asymmetry from cell culture.

PubMed

Wan, Leo Q; Chin, Amanda S; Worley, Kathryn E; Ray, Poulomi

2016-12-19

Increasing evidence suggests that intrinsic cell chirality significantly contributes to the left-right (LR) asymmetry in embryonic development, which is a well-conserved characteristic of living organisms. With animal embryos, several theories have been established, but there are still controversies regarding mechanisms associated with embryonic LR symmetry breaking and the formation of asymmetric internal organs. Recently, in vitro systems have been developed to determine cell chirality and to recapitulate multicellular chiral morphogenesis on a chip. These studies demonstrate that chirality is indeed a universal property of the cell that can be observed with well-controlled experiments such as micropatterning. In this paper, we discuss the possible benefits of these in vitro systems to research in LR asymmetry, categorize available platforms for single-cell chirality and multicellular chiral morphogenesis, and review mathematical models used for in vitro cell chirality and its applications in in vivo embryonic development. These recent developments enable the interrogation of the intracellular machinery in LR axis establishment and accelerate research in birth defects in laterality.This article is part of the themed issue 'Provocative questions in left-right asymmetry'. © 2016 The Author(s).

Inversion of Supramolecular Chirality by Sonication-Induced Organogelation

PubMed Central

Maity, Sibaprasad; Das, Priyadip; Reches, Meital

2015-01-01

Natural helical structures have inspired the formation of well-ordered peptide-based chiral nanostructures in vitro. These structures have drawn much attention owing to their diverse applications in the area of asymmetric catalysts, chiral photonic materials, and nanoplasmonics. The self-assembly of two enantiomeric fluorinated aromatic dipeptides into ordered chiral fibrillar nanostructures upon sonication is described. These fibrils form organogels. Our results clearly indicate that fluorine-fluorine interactions play an important role in self-assembly. Circular dichroism analysis revealed that both peptides (peptides 1 and 2), containing two fluorines, depicted opposite cotton effects in their monomeric form compared with their aggregated form. This shows that supramolecular chirality inversion took place during the stimuli-responsive self-aggregation process. Conversely, peptide 3, containing one fluorine, did not exhibit chirality inversion in sonication-induced organogelation. Therefore, our results clearly indicate that fluorination plays an important role in the organogelation process of these aromatic dipeptides. Our findings may have broad implications regarding the design of chiral nanostructures for possible applications such as chiroptical switches, asymmetric catalysis, and chiral recognitions. PMID:26553508

From cosmic chirality to protein structure: Lord Kelvin's legacy.

PubMed

Barron, Laurence D

2012-11-01

A selection of my work on chirality is sketched in two distinct parts of this lecture. Symmetry and Chirality explains how the discrete symmetries of parity P, time reversal T, and charge conjugation C may be used to characterize the properties of chiral systems. The concepts of true chirality (time-invariant enantiomorphism) and false chirality (time-noninvariant enantiomorphism) that emerge provide an extension of Lord Kelvin's original definition of chirality to situations where motion is an essential ingredient thereby clarifying, inter alia, the nature of physical influences able to induce absolute enantioselection. Consideration of symmetry violations reveals that strict enantiomers (exactly degenerate) are interconverted by the combined CP operation. Raman optical activity surveys work, from first observation to current applications, on a new chiroptical spectroscopy that measures vibrational optical activity via Raman scattering of circularly polarized light. Raman optical activity provides incisive information ranging from absolute configuration and complete solution structure of smaller chiral molecules and oligomers to protein and nucleic acid structure of intact viruses. Copyright © 2012 Wiley Periodicals, Inc., A Wiley Company.

Cell chirality: emergence of asymmetry from cell culture

PubMed Central

Wan, Leo Q.; Chin, Amanda S.; Worley, Kathryn E.; Ray, Poulomi

2016-01-01

Increasing evidence suggests that intrinsic cell chirality significantly contributes to the left–right (LR) asymmetry in embryonic development, which is a well-conserved characteristic of living organisms. With animal embryos, several theories have been established, but there are still controversies regarding mechanisms associated with embryonic LR symmetry breaking and the formation of asymmetric internal organs. Recently, in vitro systems have been developed to determine cell chirality and to recapitulate multicellular chiral morphogenesis on a chip. These studies demonstrate that chirality is indeed a universal property of the cell that can be observed with well-controlled experiments such as micropatterning. In this paper, we discuss the possible benefits of these in vitro systems to research in LR asymmetry, categorize available platforms for single-cell chirality and multicellular chiral morphogenesis, and review mathematical models used for in vitro cell chirality and its applications in in vivo embryonic development. These recent developments enable the interrogation of the intracellular machinery in LR axis establishment and accelerate research in birth defects in laterality. This article is part of the themed issue ‘Provocative questions in left–right asymmetry’. PMID:27821525

Chirality Transfer in Gold(I)-Catalysed Direct Allylic Etherifications of Unactivated Alcohols: Experimental and Computational Study.

PubMed

Barker, Graeme; Johnson, David G; Young, Paul C; Macgregor, Stuart A; Lee, Ai-Lan

2015-09-21

Gold(I)-catalysed direct allylic etherifications have been successfully carried out with chirality transfer to yield enantioenriched, γ-substituted secondary allylic ethers. Our investigations include a full substrate-scope screen to ascertain substituent effects on the regioselectivity, stereoselectivity and efficiency of chirality transfer, as well as control experiments to elucidate the mechanistic subtleties of the chirality-transfer process. Crucially, addition of molecular sieves was found to be necessary to ensure efficient and general chirality transfer. Computational studies suggest that the efficiency of chirality transfer is linked to the aggregation of the alcohol nucleophile around the reactive π-bound Au-allylic ether complex. With a single alcohol nucleophile, a high degree of chirality transfer is predicted. However, if three alcohols are present, alternative proton transfer chain mechanisms that erode the efficiency of chirality transfer become competitive. © 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

On stability, chirality measures, and theoretical VCD spectra of the chiral C58X2 fullerenes (X = N, B).

PubMed

Ostrowski, Sławomir; Jamróz, Michał H; Rode, Joanna E; Dobrowolski, Jan Cz

2012-01-12

The stability of all 23 C(58)N(2) and C(58)B(2) heterofullerenes in the singlet and triplet states was determined at the B3LYP/6-31G** level. In equilibrium mixture the achiral (1,4) C(58)N(2) isomer would be populated in ca. 95.8%, the chiral (1,16) one in ca. 3.3%, and the achiral (1,4) C(58)B(2) in 100%, whereas all triplet state isomers are less stable. Fourteen out of 23 C(58)X(2) are chiral. Four different chirality measures were calculated by our own CHIMEA program: pure geometrical, labeled, mass, and charge. Intercorrelations between the measures for all chiral compounds indicate that the pure geometrical chirality measure is unstable and should not be used in QSAR predictions of the other molecular properties, while the labeled and mass-weighted ones are promising QSAR descriptors. For each chiral C(58)N(2) molecule, some very strong VCD bands, of intensity comparable with that in the IR spectra, can serve in identification and characterization of the isomers.

Spin chirality and polarised neutron scattering

NASA Astrophysics Data System (ADS)

Plakhty, V. P.; Maleyev, S. V.; Kulda, J.; Visser, E. D.; Wosnitza, J.; Moskvin, E. V.; Brückel, Th.; Kremer, R. K.

2001-03-01

Possibilities of polarised neutrons in studies of chiral criticality are discussed. The critical exponents β C of the average chirality below TN, as well as φ C=β C+γ C and, therefore, γ C of the chiral susceptibility above TN are determined for a XY triangular lattice antiferromagnet (TLA) CsMnBr3: β C=0.44(2) , γ C=0.84(7) . The critical behaviour of the chirality that orders at TN with a relative precision of 5×10 -4 proves that the phase transition belongs to a new chiral universality class. For the TLA CsNiCl 3 ( S=1) we found in the XY region ( B=3 T) φ C=1.24(7) in agreement with the Monte-Carlo value φ C=1.22(6) for the chiral universality class. In the easy-axis region at B=1 T, φ C=0.54(4) , and the Haldane excitations are observed in the polarisation-dependent inelastic cross section above TN. The helimagnet holmium exhibits a different chiral criticality with φ C=1.56(5) , essentially higher than for TLAs.

Structure Study of the Chiral Lactide Molecules by Chirped-Pulse Ftmw Spectroscopy

NASA Astrophysics Data System (ADS)

Zaleski, Daniel P.; Neill, Justin L.; Pate, Brooks H.; Bialkowska-Jaworska, Ewa; Kisiel, Zbigniew

2011-06-01

Lactide is a six member cyclic diester with two chiral centers that forms from lactic acid in the presence of heat and an acid catalyst. It can form either a homo-chiral (RR) structure with both methyl groups equatorial or a hetero-chiral (RS) structure where one methyl group is equatorial and the other methyl group is axial. Structurally lactide is similar to lactic acid dimer; however, the kinked ring is covalently bonded and two waters are lost. And unlike lactic acid dimer, which has a very small dipole moment, the dipole moment of lactide is on the order of 3 Debye. Here the microwave spectra of the highly rigid homo- and hetero-chiral lactides are presented, which were first assigned in a heated lactic acid spectrum where the chemistry took place in the reservoir nozzles. Further isotopic information from a commercial sample of predominately homo-chiral lactide was obtained leading to a Kraitchman substitution structure of the homo-chiral lactide. Preliminary results of the cluster of homo-chiral lactide with one water molecule attached are also presented.

Minimally doubled fermions and spontaneous chiral symmetry breaking

NASA Astrophysics Data System (ADS)

Osmanaj (Zeqirllari), Rudina; Hyka (Xhako), Dafina

2018-03-01

Chiral symmetry breaking in massless QCD is a very important feature in the current understanding of low energy physics. Low - lying Dirac modes are suitable to help us understand the spontaneous chiral symmetry breaking, since the formation of a non zero chiral condensate is an effect of their accumulation near zero. The Banks - Casher relation links the spectral density of the Dirac operator to the condensate with an identity that can be read in both directions. In this work we propose a spectral method to achieve a reliable determination of the density of eigenvalues of Dirac operator near zero using the Gauss - Lanczos quadrature. In order to understand better the dynamical chiral symmetry breaking and use the method we propose, we have chosen to work with minimally doubled fermions. These kind of fermions have been proposed as a strictly local discretization of the QCD fermions action, which preserves chiral symmetry at finite cut-off. Being chiral fermions, is easier to work with them and their low - lying Dirac modes and to understand the dynamical spontaneous chiral symmetry breaking.

Neuronal growth on L- and D-cysteine self-assembled monolayers reveals neuronal chiral sensitivity.

PubMed

Baranes, Koby; Moshe, Hagay; Alon, Noa; Schwartz, Shmulik; Shefi, Orit

2014-05-21

Studying the interaction between neuronal cells and chiral molecules is fundamental for the design of novel biomaterials and drugs. Chirality influences all biological processes that involve intermolecular interaction. One common method used to study cellular interactions with different enantiomeric targets is the use of chiral surfaces. Based on previous studies that demonstrated the importance of cysteine in the nervous system, we studied the effect of L- and D-cysteine on single neuronal growth. L-Cysteine, which normally functions as a neuromodulator or a neuroprotective antioxidant, causes damage at elevated levels, which may occur post trauma. In this study, we grew adult neurons in culture enriched with L- and D-cysteine as free compounds or as self-assembled monolayers of chiral surfaces and examined the effect on the neuronal morphology and adhesion. Notably, we have found that exposure to the L-cysteine enantiomer inhibited, and even prevented, neuronal attachment more severely than exposure to the D-cysteine enantiomer. Atop the L-cysteine surfaces, neuronal growth was reduced and degenerated. Since the cysteine molecules were attached to the surface via the thiol groups, the neuronal membrane was exposed to the molecular chiral site. Thus, our results have demonstrated high neuronal chiral sensitivity, revealing chiral surfaces as indirect regulators of neuronal cells and providing a reference for studying chiral drugs.

Chirality as a tool in nucleic acid recognition: principles and relevance in biotechnology and in medicinal chemistry.

PubMed

Corradini, Roberto; Sforza, Stefano; Tedeschi, Tullia; Marchelli, Rosangela

2007-05-05

The understanding of the interaction of chiral species with DNA or RNA is very important for the development of new tools in biology and of new drugs. Several cases in which chirality is a crucial point in determining the DNA binding mode are reviewed and discussed, with the aim of illustrating how chirality can be considered as a tool for improving the understanding of mechanisms and the effectiveness of nucleic acid recognition. The review is divided into two parts: the former describes examples of chiral species interacting with DNA: intercalators, metal complexes, and groove binders; the latter part is dedicated to chirality in DNA analogs, with discussion of phosphate stereochemistry and chirality of ribose substitutes, in particular of peptide nucleic acids (PNAs) for which a number of works have been published recently dealing with the effect of chirality in DNA recognition. The discussion is intended to show how enantiomeric recognition originates at the molecular level, by exploiting the enormous progresses recently achieved in the field of structural characterization of complexes formed by nucleic acid with their ligands by crystallographic and spectroscopic methods. Examples of application of the DNA binding molecules described and the role of chirality in DNA recognition relevant for biotechnology or medicinal chemistry are reported. (c) 2007 Wiley-Liss, Inc.

Increments to chiral recognition facilitating enantiomer separations of chiral acids, bases, and ampholytes using Cinchona-based zwitterion exchanger chiral stationary phases.

PubMed

Wernisch, Stefanie; Pell, Reinhard; Lindner, Wolfgang

2012-07-01

The intramolecular distances of anion and cation exchanger sites of zwitterionic chiral stationary phases represent potential tuning sites for enantiomer selectivity. In this contribution, we investigate the influence of alkanesulfonic acid chain length and flexibility on enantiomer separations of chiral acids, bases, and amphoteric molecules for six Cinchona alkaloid-based chiral stationary phases in comparison with structurally related anion and cation exchangers. Employing polar-organic elution conditions, we observed an intramolecular counterion effect for acidic analytes which led to reduced retention times but did not impair enantiomer selectivities. Retention of amphoteric analytes is based on simultaneous double ion pairing of their charged functional groups with the acidic and basic sites of the zwitterionic selectors. A chiral center in the vicinity of the strong cation exchanger site is vital for chiral separations of bases. Sterically demanding side chains are beneficial for separations of free amino acids. Enantioseparations of free (un-derivatized) peptides were particularly successful in stationary phases with straight-chain alkanesulfonic acid sites, pointing to a beneficial influence of more flexible moieties. In addition, we observed pseudo-enantiomeric behavior of quinine and quinidine-derived chiral stationary phases facilitating reversal of elution orders for all analytes. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chiral Polychlorinated Biphenyl Transport, Metabolism and Distribution - A Review

PubMed Central

Lehmler, Hans-Joachim; Harrad, Stuart J.; Hühnerfuss, Heinrich; Kania-Korwel, Izabela; Lee, Cindy M.; Lu, Zhe; Wong, Charles S.

2009-01-01

Chirality can be exploited to gain insight into enantioselective fate processes that may otherwise remain undetected because only biological, but not physical and chemical transport and transformation processes in an achiral environment will change enantiomer compositions. This review provides an in-depth overview of the application of chirality to the study of chiral polychlorinated biphenyls (PCBs), an important group of legacy pollutants. Like other chiral compounds, individual PCB enantiomers may interact enantioselectively (or enantiospecifically) with chiral macromolecules, such as cytochrome P-450 enzymes or ryanodine receptors, leading to differences in their toxicological effects and the enantioselective formation of chiral biotransformation products. Species and congener-specific enantiomer enrichment has been demonstrated in environmental compartments, wildlife and mammals, including humans, typically due to a complex combination of biotransformation processes and uptake via the diet by passive diffusion. Changes in the enantiomer composition of chiral PCBs in the environment have been used to understand complex aerobic and anaerobic microbial transformation pathways, to delineate and quantify PCB sources and transport in the environment, to gain insight into the biotransformation of PCBs in aquatic food webs, and to investigate the enantioselective disposition of PCBs and their methylsulfonyl PCBs metabolites in rodents. Overall, changes in chiral signatures are powerful, but currently underutilized tools for studies of environmental and biological processes of PCBs. PMID:20384371

The kinetics of chirality assignment in catalytic single-walled carbon nanotube growth and the routes towards selective growth† †Electronic supplementary information (ESI) available: Details of density functional theory (DFT) calculations, definition of interfacial formation energy (IFE), cap formation energy and fitting equation, Fig. S1–S4 and Table S1. See DOI: 10.1039/c7sc04714b

PubMed Central

Xu, Ziwei; Qiu, Lu

2018-01-01

Depending on its specific structure, or so-called chirality, a single-walled carbon nanotube (SWCNT) can be either a conductor or a semiconductor. This feature ensures great potential for building ∼1 nm sized electronics if chirality-selected SWCNTs could be achieved. However, due to the limited understanding of the growth mechanism of SWCNTs, reliable methods for chirality-selected SWCNTs are still pending. Here we present a theoretical model on the chirality assignment and control of SWCNTs during the catalytic growth. This study reveals that the chirality of a SWCNT is determined by the kinetic incorporation of pentagons, especially the last (6th) one, during the nucleation stage. Our analysis showed that the chirality of a SWCNT is randomly assigned on a liquid or liquid-like catalyst surface, and two routes of synthesizing chirality-selected SWCNTs, which are verified by recent experimental achievements, are demonstrated. They are (i) by using high melting point crystalline catalysts, such as Ta, W, Re, Os, or their alloys, and (ii) by frequently changing the chirality of SWCNTs during their growth. This study paves the way for achieving chirality-selective SWCNT growth for high performance SWCNT based electronics. PMID:29732090

Rediscovering Chirality - Role of S-Metoprolol in Cardiovascular Disease Management.

PubMed

Mohan, Jagdish C; Shah, Siddharth N; Chinchansurkar, Sunny; Dey, Arindam; Jain, Rishi

2017-06-01

The process of drug discovery and development today encompass a myriad of paths for bringing a new therapeutic molecule that has minimal adverse effects and of optimal use to the patient. Chirality was proposed in the direction of providing a purer and safer form of drug [Ex- cetrizine and levocetrizine]. Decades have passed since the introduction of this concept and numerous chiral molecules are in existence in therapeutics, yet somehow this concept has been ignored. This review aims to rediscover the ignored facts about chirality, its benefits and clear some common myths considering the example of S-Metoprolol in the management of Hypertension and other cardiovascular diseases. Relevant articles from Pubmed, Embase, Medline and Google Scholar were searched using the terms "Chiral", "Chirality", "Enantiomers", "Isomers", "Isomerism", "Stereo-chemistry", and "S-Metoprolol". Out of 103 articles found 17 articles mentioning in general about the concept of chirality and articles on study of S-metoprolol in various cardiovascular diseases were then reviewed. Many articles mention about the importance of chirality yet the concept has not been highlighted much. Clear benefits with chiral molecules have been documented for various drug molecules few amongst them being anaesthetics, antihypertensives, antidepressants. Benefits of S-metoprolol over racemate are also clear in terms of responder rates, dose of administration and adverse effects profile in various cardiovascular diseases. Chirality is a good way forward in providing a new drug molecule which is safe with lesser pharmacokinetic and pharmacodynamics variability, lesser side effects and more potent action. S-metoprolol is chirally pure form of racemate metoprolol and has lesser side effects, is safer in patients of COPD and Diabetes who also have hypertension and comparable responder rates at half the doses when compared to racemate.

Chiral discrimination in nuclear magnetic resonance spectroscopy

NASA Astrophysics Data System (ADS)

Lazzeretti, Paolo

2017-11-01

Chirality is a fundamental property of molecules whose spatial symmetry is characterized by the absence of improper rotations, making them not superimposable to their mirror image. Chiral molecules constitute the elementary building blocks of living species and one enantiomer is favoured in general (e.g. L-aminoacids and D-sugars pervade terrestrial homochiral biochemistry) because most chemical reactions producing natural substances are enantioselective. Since the effect of chiral chemicals and drugs on living beings can be markedly different between enantiomers, the quest for practical spectroscopical methods to scrutinize chirality is an issue of great importance and interest. Nuclear magnetic resonance (NMR) is a topmost analytical technique, but spectrometers currently used are ‘blind’ to chirality, i.e. unable to discriminate the two mirror-image forms of a chiral molecule, because, in the absence of a chiral solvent, the spectral parameters, chemical shifts and spin-spin coupling constants are identical for enantiomers. Therefore, the development of new procedures for routine chiral recognition would offer basic support to scientists. However, in the presence of magnetic fields, a distinction between true and false chirality is mandatory. The former epitomizes natural optical activity, which is rationalized by a time-even pseudoscalar, i.e. the trace of a second-rank tensor, the mixed electric dipole/magnetic dipole polarizability. The Faraday effect, magnetic circular dichroism and magnetic optical activity are instead related to a time-odd axial vector. The present review summarizes recent theoretical and experimental efforts to discriminate enantiomers via NMR spectroscopy, with the focus on the deep connection between chirality and symmetry properties under the combined set of fundamental discrete operations, namely charge conjugation, parity (space inversion) and time (motion) reversal.

Crystallization-induced dynamic resolution of Fox chiral auxiliary and application to the diastereoselective electrophilic fluorination of amide enolates.

PubMed

Lubin, Hodney; Dupuis, Christophe; Pytkowicz, Julien; Brigaud, Thierry

2013-04-05

A highly efficient crystallization-induced dynamic resolution (CIDR) of trans-Fox (fluorinated oxazolidine) chiral auxiliary is reported. This chiral auxiliary was used for highly diastereoselective (>98% de) electrophilic fluorination of amide enolates. After removal of the chiral auxiliary, highly valuable enantiopure α-fluorocarboxylic acids and β-fluoroalcohols are obtained.

Use of Chiral Oxazolidinones for a Multi-Step Synthetic Laboratory Module

ERIC Educational Resources Information Center

Betush, Matthew P.; Murphree, S. Shaun

2009-01-01

Chiral oxazolidinone chemistry is used as a framework for an advanced multi-step synthesis lab. The cost-effective and robust preparation of chiral starting materials is presented, as well as the use of chiral auxiliaries in a synthesis scheme that is appropriate for students currently in the second semester of the organic sequence. (Contains 1…

Chiral selection on inorganic crystalline surfaces

NASA Technical Reports Server (NTRS)

Hazen, Robert M.; Sholl, David S.

2003-01-01

From synthetic drugs to biodegradable plastics to the origin of life, the chiral selection of molecules presents both daunting challenges and significant opportunities in materials science. Among the most promising, yet little explored, avenues for chiral molecular discrimination is adsorption on chiral crystalline surfaces - periodic environments that can select, concentrate and possibly even organize molecules into polymers and other macromolecular structures. Here we review experimental and theoretical approaches to chiral selection on inorganic crystalline surfaces - research that is poised to open this new frontier in understanding and exploiting surface-molecule interactions.

Heavy-light mesons in chiral AdS/QCD

NASA Astrophysics Data System (ADS)

Liu, Yizhuang; Zahed, Ismail

2017-06-01

We discuss a minimal holographic model for the description of heavy-light and light mesons with chiral symmetry, defined in a slab of AdS space. The model consists of a pair of chiral Yang-Mills and tachyon fields with specific boundary conditions that break spontaneously chiral symmetry in the infrared. The heavy-light spectrum and decay constants are evaluated explicitly. In the heavy mass limit the model exhibits both heavy-quark and chiral symmetry and allows for the explicit derivation of the one-pion axial couplings to the heavy-light mesons.

Phenomenology of anomalous chiral transports in heavy-ion collisions

NASA Astrophysics Data System (ADS)

Huang, Xu-Guang

2018-01-01

High-energy Heavy-ion collisions can generate extremely hot quark-gluon matter and also extremely strong magnetic fields and fluid vorticity. Once coupled to chiral anomaly, the magnetic fields and fluid vorticity can induce a variety of novel transport phenomena, including the chiral magnetic effect, chiral vortical effect, etc. Some of them require the environmental violation of parity and thus provide a means to test the possible parity violation in hot strongly interacting matter. We will discuss the underlying mechanism and implications of these anomalous chiral transports in heavy-ion collisions.

A chiral aluminum solvating agent (CASA) for 1H NMR chiral analysis of alcohols at low temperature.

PubMed

Seo, Min-Seob; Jang, Sumin; Kim, Hyunwoo

2018-03-16

A chiral aluminum solvating agent (CASA) was demonstrated to be a general and efficient reagent for 1H NMR chiral analysis of alcohols. The sodium salt of the CASA (CASA-Na) showed a complete baseline peak separation of the hydroxyl group for various chiral alcohols including primary, secondary, and tertiary alcohols with alkyl and aryl substituents in CD3CN. Due to the weak intermolecular interaction, 1H NMR measurement at low temperature (-40 to 10 °C) was required.

Rhodium-catalyzed Asymmetric Hydrogenation of α-Dehydroamino Ketones: A General Approach to Chiral α-amino Ketones.

PubMed

Gao, Wenchao; Wang, Qingli; Xie, Yun; Lv, Hui; Zhang, Xumu

2016-01-01

Rhodium/DuanPhos-catalyzed asymmetric hydrogenation of aliphatic α-dehydroamino ketones has been achieved and afforded chiral α-amino ketones in high yields and excellent enantioselectives (up to 99 % ee), which could be reduced further to chiral β-amino alcohols by LiAlH(tBuO)3 with good yields. This protocol provides a readily accessible route for the synthesis of chiral α-amino ketones and chiral β-amino alcohols. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

On consistency of hydrodynamic approximation for chiral media

NASA Astrophysics Data System (ADS)

Avdoshkin, A.; Kirilin, V. P.; Sadofyev, A. V.; Zakharov, V. I.

2016-04-01

We consider chiral liquids, that is liquids consisting of massless fermions and right-left asymmetric. In such media, one expects existence of electromagnetic current flowing along an external magnetic field, associated with the chiral anomaly. The current is predicted to be dissipation-free. We consider dynamics of chiral liquids, concentrating on the issues of possible instabilities and infrared sensitivity. Instabilities arise, generally speaking, already in the limit of vanishing electromagnetic constant, αel → 0. In particular, liquids with non-vanishing chiral chemical potential might decay into right-left asymmetric states containing vortices.

Chirality-induced negative refraction in magnetized plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, B.

2013-09-15

Characteristic equations in magnetized plasma with chirality are derived in simple formulations and the dispersion relations for propagation parallel and perpendicular to the external magnetic field are studied in detail. With the help of the dispersion relations of each eigenwave, the author explores chirality-induced negative refraction in magnetized plasma and investigates the effects of parameters (i.e., chirality degree, external magnetic field, etc.) on the negative refraction. The results show that the chirality is the necessary and only one factor which leads to negative refraction without manipulating electrical permittivity and magnetic permeability. Both increasing the degree of chirality and reducing themore » external magnetic field can result in greater range negative refraction. Parameter dependence of the effects is calculated and discussed.« less

Quark structure of chiral solitons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dmitri Diakonov

2004-05-01

There is a prejudice that the chiral soliton model of baryons is something orthogonal to the good old constituent quark models. In fact, it is the opposite: the spontaneous chiral symmetry breaking in strong interactions explains the appearance of massive constituent quarks of small size thus justifying the constituent quark models, in the first place. Chiral symmetry ensures that constituent quarks interact very strongly with the pseudoscalar fields. The ''chiral soliton'' is another word for the chiral field binding constituent quarks. We show how the old SU(6) quark wave functions follow from the ''soliton'', however, with computable relativistic corrections andmore » additional quark-antiquark pairs. We also find the 5-quark wave function of the exotic baryon Theta+.« less

A quantitative measure of chirality inside nucleic acid databank.

PubMed

Pietropaolo, Adriana; Parrinello, Michele

2011-08-01

We show the capability of a chirality index (Pietropaolo et al., Proteins 2008;70:667-677) to investigate nucleic acid structures because of its high sensitivity to helical conformations. By analyzing selected structures of DNA and RNA, we have found that sequences rich in cytosine and guanine have a tendency to left-handed chirality, in contrast to regions rich in adenine or thymine which show strong negative, right-handed, chirality values. We also analyze RNA structures, where specific loops and hairpin motifs are characterized by a well-defined chirality value. We find that in nucleosome the chirality is exalted, whereas in ribosome it is reduced. Our results illustrate the sensitivity of this descriptor for nucleic acid conformations. Copyright © 2011 Wiley-Liss, Inc.

Solvent polarity effects on supramolecular chirality of a polyfluorene-thiophene copolymer.

PubMed

Hirahara, Takashi; Yoshizawa-Fujita, Masahiro; Takeoka, Yuko; Rikukawa, Masahiro

2018-06-01

This study demonstrates the supramolecular chirality control of a conjugated polymer via solvent polarity. We designed and synthesized a chiral polyfluorene-thiophene copolymer having two different chiral side chains at the 9-position of the fluorene unit. Chiral cyclic and alkyl ethers with different polarities were selected as the chiral side chains. The sign of the circular dichroism spectra in the visible wavelength region was affected by the solvent system, resulting from the change of supramolecular structure. The estimation of the solubility parameter revealed that the solubility difference of the side chains contributed to the change of the circular dichroism sign, which was also observed in spin-coated films prepared from good solvents having different polarities. © 2018 Wiley Periodicals, Inc.

Enantiopure Ferrocene-Based Planar-Chiral Iridacycles: Stereospecific Control of Iridium-Centred Chirality.

PubMed

Arthurs, Ross A; Ismail, Muhammad; Prior, Christopher C; Oganesyan, Vasily S; Horton, Peter N; Coles, Simon J; Richards, Christopher J

2016-02-24

Reaction of [IrCp*Cl2 ]2 with ferrocenylimines (Fc=NAr, Ar=Ph, p-MeOC6 H4 ) results in ferrocene C-H activation and the diastereoselective synthesis of half-sandwich iridacycles of relative configuration Sp *,RIr *. Extension to (S)-2-ferrocenyl-4-(1-methylethyl)oxazoline gave highly diastereoselective control over the new elements of planar chirality and metal-based pseudo-tetrahedral chirality, to give both neutral and cationic half-sandwich iridacycles of absolute configuration Sc ,Sp ,RIr . Substitution reactions proceed with retention of configuration, with the planar chirality controlling the metal-centred chirality through an iron-iridium interaction in the coordinatively unsaturated cationic intermediate. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Experimental comparison of chiral metal-organic framework used as stationary phase in chromatography.

PubMed

Xie, Sheng-Ming; Zhang, Mei; Fei, Zhi-Xin; Yuan, Li-Ming

2014-10-10

Chiral metal-organic frameworks (MOFs) are a new class of multifunctional material, which possess diverse structures and unusual properties such as high surface area, uniform and permanent cavities, as well as good chemical and thermal stability. Their chiral functionality makes them attractive as novel enantioselective adsorbents and stationary phases in separation science. In this paper, the experimental comparison of a chiral MOF [In₃O(obb)₃(HCO₂)(H₂O)] solvent used as a stationary phase was investigated in gas chromatography (GC), high-performance liquid chromatography (HPLC) and capillary electrochromatography (CEC). The potential relationship between the structure and components of chiral MOFs with their chiral recognition ability and selectivity are presented. Copyright © 2014 Elsevier B.V. All rights reserved.

Chiral Plasmonic Nanostructures Fabricated by Circularly Polarized Light.

PubMed

Saito, Koichiro; Tatsuma, Tetsu

2018-05-09

The chirality of materials results in a wide variety of advanced technologies including image display, data storage, light management including negative refraction, and enantioselective catalysis and sensing. Here, we introduce chirality to plasmonic nanostructures by using circularly polarized light as the sole chiral source for the first time. Gold nanocuboids as precursors on a semiconductor were irradiated with circularly polarized light to localize electric fields at specific corners of the cuboids depending on the handedness of light and deposited dielectric moieties as electron oscillation boosters by the localized electric field. Thus, plasmonic nanostructures with high chirality were developed. The present bottom-up method would allow the large-scale and cost-effective fabrication of chiral materials and further applications to functional materials and devices.

Evidence of chiral bands in even-even nuclei

NASA Astrophysics Data System (ADS)

Petrache, C. M.; Lv, B. F.; Astier, A.; Dupont, E.; Wang, Y. K.; Zhang, S. Q.; Zhao, P. W.; Ren, Z. X.; Meng, J.; Greenlees, P. T.; Badran, H.; Cox, D. M.; Grahn, T.; Julin, R.; Juutinen, S.; Konki, J.; Pakarinen, J.; Papadakis, P.; Partanen, J.; Rahkila, P.; Sandzelius, M.; Saren, J.; Scholey, C.; Sorri, J.; Stolze, S.; Uusitalo, J.; Cederwall, B.; Aktas, Ö.; Ertoprak, A.; Liu, H.; Matta, S.; Subramaniam, P.; Guo, S.; Liu, M. L.; Zhou, X. H.; Wang, K. L.; Kuti, I.; Timár, J.; Tucholski, A.; Srebrny, J.; Andreoiu, C.

2018-04-01

Evidence for chiral doublet bands has been observed for the first time in the even-even nucleus 136Nd. One chiral band was firmly established. Four other candidates for chiral bands were also identified, which can contribute to the realization of the multiple pairs of chiral doublet bands (M χ D ) phenomenon. The observed bands are investigated by the constrained and tilted axis cranking covariant density functional theory (TAC-CDFT). Possible configurations have been explored. The experimental energy spectra, angular momenta, and B (M 1 )/B (E 2 ) values for the assigned configurations are globally reproduced by TAC-CDFT. Calculated results support the chiral interpretation of the observed bands, which correspond to shapes with maximum triaxiality induced by different multiquasiparticle configurations in 136Nd.

Enantioselective environmental toxicology of chiral pesticides.

PubMed

Ye, Jing; Zhao, Meirong; Niu, Lili; Liu, Weiping

2015-03-16

The enantioselective environmental toxic effect of chiral pesticides is becoming more important. As the industry develops, increasing numbers of chiral insecticides and herbicides will be introduced into use, potentially posing toxic effects on nontarget living beings. Chiral pesticides, including herbicides such as acylanilides, phenoxypropanoic acids, and imidazolinones, and insecticides such as synthetic pyrethroids, organophosphates, and DDT often behave enantioselectively during agricultural use. These compounds also pose unpredictable enantioselective ecological threats to nontarget living beings and/or humans, affecting the food chain and entire ecosystems. Thus, to investigate the enantioselective toxic effects of chiral insecticides and herbicides is necessary during environmental protection. The environmental toxicology of chiral pesticides, especially the findings obtained from studies conducted in our laboratory during the past 10 years, is reviewed.

Characteristics of chiral plasma plumes generated in the absence of external magnetic field

NASA Astrophysics Data System (ADS)

Nie, LanLan; Liu, FengWu; Zhou, XinCai; Lu, XinPei; Xian, YuBin

2018-05-01

A chiral plasma plume has recently been generated inside a dielectric tube without the use of an external magnetic field. In this paper, we seek to further study the key properties of such a chiral plume to improve our understanding of how this interesting structure is generated and controlled. The chiral plume is generated by externally mounting a stainless steel helical coil or a ring onto the dielectric tube. By changing the pitch of the helical coil, the pitch of the plasma plume can be controlled, with the shape of the plume following the shape of the helical coil. The addition of the helical coil significantly expands the range of parameters under which the chiral plasma plume appears. When the frequency of the applied voltage increases, additional stable discharge channels appear between the adjacent helices. The addition of two helical coils results in the formation of two chiral plasma plumes, which follow the shape of the helical coils. When a metal ring is placed on the outside of the tube, there is no chiral plasma plume between the high voltage electrode and the ring; however, a chiral plasma plume appears on the right side of the ring if the distance between the ring and the high voltage electrode is small. These findings suggest that the chiral plasma can be effectively modulated and guided using an externally mounted helical coil, which acts as the floating/actual ground to reduce the impedance of the discharge and as such contributes to the emergence of the chiral plasma plume behavior.

Criteria of backscattering in chiral one-way photonic crystals

NASA Astrophysics Data System (ADS)

Cheng, Pi-Ju; Chang, Shu-Wei

2016-03-01

Optical isolators are important devices in photonic circuits. To reduce the unwanted reflection in a robust manner, several setups have been realized using nonreciprocal schemes. In this study, we show that the propagating modes in a strongly-guided chiral photonic crystal (no breaking of the reciprocity) are not backscattering-immune even though they are indeed insensitive to many types of scatters. Without the protection from the nonreciprocity, the backscattering occurs under certain circumstances. We present a perturbative method to calculate the backscattering of chiral photonic crystals in the presence of chiral/achiral scatters. The model is, essentially, a simplified analogy to the first-order Born approximation. Under reasonable assumptions based on the behaviors of chiral photonic modes, we obtained the expression of reflection coefficients which provides criteria for the prominent backscattering in such chiral structures. Numerical examinations using the finite-element method were also performed and the results agree well with the theoretical prediction. From both our theory and numerical calculations, we find that the amount of backscattering critically depends on the symmetry of scatter cross sections. Strong reflection takes place when the azimuthal Fourier components of scatter cross sections have an order l of 2. Chiral scatters without these Fourier components would not efficiently reflect the chiral photonic modes. In addition, for these chiral propagating modes, disturbances at the most significant parts of field profiles do not necessarily result in the most effective backscattering. The observation also reveals what types of scatters or defects should be avoided in one-way applications of chiral structures in order to minimize the backscattering.

Enantiomeric separation of volatile organics by gas chromatography for the in situ analysis of extraterrestrial materials: kinetics and thermodynamics investigation of various chiral stationary phases.

PubMed

Freissinet, C; Buch, A; Szopa, C; Sternberg, R

2013-09-06

The performances of several commercial chiral capillary columns have been evaluated with the aim of determining the one most suitable for enantiomeric separation in a gas chromatograph onboard a space probe. We compared the GC-MS response of three capillary columns coated with different chiral stationary phases (CSP) using volatile chiral organic molecules which are potential markers of a prebiotic organic chemistry. The three different chiral capillary columns are Chirasil-Val, with an amino acid derivative CSP, ChiralDex-β-PM, with a CSP composed of dissolved permethylated β-cyclodextrins in polysiloxane, and Chirasil-Dex, with a CSP made of modified cyclodextrins chemically bonded to the polysiloxane backbone. Both kinetics and thermodynamics studies have been carried out to evaluate the chiral recognition potential in these different types of columns. The thermodynamic parameters also allow a better understanding of the driving forces affecting the retention and separation of the enantiomers. The Chirasil-Dex-CSP displays the best characteristics for an optimal resolution of the chiral compounds, without preliminary derivatization. This CSP had been chosen to be the only chiral column in the Sample Analysis at Mars (SAM) experiment onboard the current Mars Science Laboratory (MSL) mission, and is also part of the Mars Organic Molecules Analyzer (MOMA) gas chromatograph onboard the next Martian mission ExoMars. The use of this column could also be extended to all space missions aimed at studying chirality in space. Copyright © 2013 Elsevier B.V. All rights reserved.

Enantioselective potential of polysaccharide-based chiral stationary phases in supercritical fluid chromatography.

PubMed

Kucerova, Gabriela; Kalikova, Kveta; Tesarova, Eva

2017-06-01

The enantioselective potential of two polysaccharide-based chiral stationary phases for analysis of chiral structurally diverse biologically active compounds was evaluated in supercritical fluid chromatography using a set of 52 analytes. The chiral selectors immobilized on 2.5 μm silica particles were tris-(3,5-dimethylphenylcarmabate) derivatives of cellulose or amylose. The influence of the polysaccharide backbone, different organic modifiers, and different mobile phase additives on retention and enantioseparation was monitored. Conditions for fast baseline enantioseparation were found for the majority of the compounds. The success rate of baseline and partial enantioseparation with cellulose-based chiral stationary phase was 51.9% and 15.4%, respectively. Using amylose-based chiral stationary phase we obtained 76.9% of baseline enantioseparations and 9.6% of partial enantioseparations of the tested compounds. The best results on cellulose-based chiral stationary phase were achieved particularly with propane-2-ol and a mixture of isopropylamine and trifluoroacetic acid as organic modifier and additive to CO 2 , respectively. Methanol and basic additive isopropylamine were preferred on amylose-based chiral stationary phase. The complementary enantioselectivity of the cellulose- and amylose-based chiral stationary phases allows separation of the majority of the tested structurally different compounds. Separation systems were found to be directly applicable for analyses of biologically active compounds of interest. © 2017 Wiley Periodicals, Inc.

Electrochemical impedance based chiral analysis of anti-ascorbutic drug: l-Ascorbic acid and d-ascorbic acid using C-dots decorated conductive polymer nano-composite electrode.

PubMed

Pandey, Indu; Kant, Rama

2016-03-15

Clinical manifestations owing to l-ascorbic acid for scurvy as comparison to d-ascorbic acid and challenges of chiral purity are overcome by using chiral selective conductive polymer nanocomposite which mimics antibodies and enzymes. A novel chiral selective imprinted polyaniline-ferrocene-sulfonic acid film has been electrochemically fabricated on C-dots modified pencil graphite electrode. The performance of the obtained l-ascorbic acid or d-ascorbic acid chiral selective sensor was investigated by electrochemical impedance spectroscopy, cyclic and differential pulse voltammetry. The surface characteristics of the C-dots, chiral sensor before and after the de-doping of chiral d- and l-ascorbic acid were characterized by scanning electron microscopy, Raman spectroscopy and X-ray diffraction spectroscopy. Excellent recognition results were obtained by difference in electron transfer resistance. The proposed chiral sensor is capable of measuring d-ascorbic acid or l-ascorbic acid in aqueous as well as in real and commercial samples within the range of 0.020-0.187 nM and 0.003-0.232 nM with detection limit of 0.00073 nM and 0.00016 nM, respectively. The proposed method has also been examined for the chiral selective recognition of ascorbic acid isomers (d- and l-) quantitatively, in complicated matrices of real samples. Copyright © 2015 Elsevier B.V. All rights reserved.

Determination of the absolute configurations at stereogenic centers in the presence of axial chirality.

PubMed

Polavarapu, Prasad L; Jeirath, Neha; Kurtán, Tibor; Pescitelli, Gennaro; Krohn, Karsten

2009-01-01

Cephalochromin, a homodimeric naphthpyranone natural product, contains both axial chirality due to the hindered rotation along the biaryl axis and central chirality due to the C-2, C-2' stereogenic centers of the fused pyranone ring. For determining the absolute configurations (ACs) of central chirality elements, different chiroptical spectroscopic methods, namely vibrational circular dichroism (VCD), electronic circular dichroism (ECD), and optical rotation (OR), have been used. From these experimental data, in conjunction with corresponding quantum chemical predictions at B3LYP/6-311G* level, it is found that the ECD spectra of cephalochromin are dominated by its axial chirality and are not suitable to distinguish the (aS,2S,2'S) and (aS,2R,2'R) diastereomers and hence to determine the ACs of the central chirality elements. OR signs also did not distinguish the (aS,2S,2'S) and (aS,2R,2'R) diastereomers. On other hand, VCD spectrum of cephalochromin exhibited separate spectral features attributable to axial chirality and stereogenic centers, thereby allowing the determination of both types of chirality elements. This is the first investigation demonstrating that, because of vibrations specific to the studied stereogenic centers, VCD spectroscopy can be used to simultaneously determine the ACs of axial and central chirality elements whenever other chiroptical methods (ECD and OR) fail to report on them. (c) 2009 Wiley-Liss, Inc.

Chiral magnetic effect in condensed matter systems

NASA Astrophysics Data System (ADS)

Li, Qiang; Kharzeev, Dmitri E.

2016-12-01

The chiral magnetic effect (CME) is the generation of electrical current induced by chirality imbalance in the presence of magnetic field. It is a macroscopic manifestation of the quantum chiral anomaly [S. L. Adler. Axial-vector vertex in spinor electrodynamics. Physical Review, 177, 2426 (1969), J. S. Bell and R. Jackiw. A PCAC puzzle: π 0 γγin the σ-model. Il Nuovo Cimento A, 60, 47-61 (1969)] in systems possessing charged chiral fermions. In quark-gluon plasma containing nearly massless quarks, the chirality imbalance is sourced by the topological transitions. In condensed matter systems, the chiral quasiparticles emerge in gapless semiconductors with two energy bands having pointlike degeneracies opening the path to the study of chiral anomaly [H. B. Nielsen and M. Ninomiya. The Adler-Bell-Jackiw anomaly and Weyl fermions in a crystal. Physics Letters B, 130, 389-396 (1983)]. Recently, these novel materials - so-called Dirac and Weyl semimetals have been discovered experimentally, are suitable for the investigation of the CME in condensed matter experiments. Here we report on the first experimental observation of the CME in a 3D Dirac semimetal ZrTe5 [Q. Li, D. E. Kharzeev, C. Zhang, Y. Huang, I. Pletikosić, A. V. Fedorov, R. D. Zhong, J. A. Schneeloch, G. D. Gu, and T. Valla. Chiral magnetic effect in ZrTe5. Nature Physics (2016) doi:10.1038/nphys3648].

Chiral Polymers.

DTIC Science & Technology

1984-10-01

regardless of the method of polymerization. The styrene-bead copolymers were packed in HPLC columns, but none were especiall, effective in separating...enantiomers in a racemic mixture. The chiral butyrolactone polymer was coated on silica, but this material did not effect resolution of racemic mixtures in an...been effected utilizing chiral oxazolines3 prompted the initial efforts to synthesize various chiral 2-vinyl- oxazoline monomers for incorporation

THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS: Neutrino Oscillation Induced by Chiral Phase Transition

NASA Astrophysics Data System (ADS)

Mu, Cheng-Fu; Sun, Gao-Feng; Zhuang, Peng-Fei

2009-03-01

Electric charge neutrality provides a relationship between chiral dynamics and neutrino propagation in compact stars. Due to the sudden drop of the electron density at thefirst-order chiral phase transition, the oscillation for low energy neutrinos is significant and can be regarded as a signature of chiral symmetry restoration in the core of compact stars.

Investigation of Chirality Selection Mechanism of Single-Walled Carbon Nanotube

DTIC Science & Technology

2015-07-17

Final 3. DATES COVERED (From - To) 01-June-2014 to 31-May-2015 4. TITLE AND SUBTITLE Investigation of Chirality Selection Mechanism of...of two significant mechanistic aspects of carbon nanotube (CNT) array growth under chemical vapor deposition conditions: chirality selectivity and...affected by the morphological evolution of catalyst particles. 15. SUBJECT TERMS Carbon Nanotubes, Chirality , Processing, Catalysis

Periodic chiral structures

NASA Technical Reports Server (NTRS)

Jaggard, Dwight L.; Engheta, Nader; Pelet, Philippe; Liu, John C.; Kowarz, Marek W.; Kim, Yunjin

1989-01-01

The electromagnetic properties of a structure that is both chiral and periodic are investigated using coupled-mode equations. The periodicity is described by a sinusoidal perturbation of the permittivity, permeability, and chiral admittance. The coupled-mode equations are derived from physical considerations and used to examine bandgap structure and reflected and transmitted fields. Chirality is observed predominantly in transmission, whereas periodicity is present in both reflection and transmission.

Lock-in of a Chiral Soliton Lattice by Itinerant Electrons

NASA Astrophysics Data System (ADS)

Okumura, Shun; Kato, Yasuyuki; Motome, Yukitoshi

2018-03-01

Chiral magnets often show intriguing magnetic and transport properties associated with their peculiar spin textures. A typical example is a chiral soliton lattice, which is found in monoaxial chiral magnets, such as CrNb3S6 and Yb(Ni1-xCux)3Al9 in an external magnetic field perpendicular to the chiral axis. Here, we theoretically investigate the electronic and magnetic properties in the chiral soliton lattice by a minimal itinerant electron model. Using variational calculations, we find that the period of the chiral soliton lattice can be locked at particular values dictated by the Fermi wave number, in stark contrast to spin-only models. We discuss this behavior caused by the spin-charge coupling as a possible mechanism for the lock-in discovered in Yb(Ni1-xCux)3Al9 [T. Matsumura et al., J. Phys. Soc. Jpn. 86, 124702 (2017)]. We also show that the same mechanism leads to the spontaneous formation of the chiral soliton lattice even in the absence of the magnetic field.

Enantiospecific Detection of Chiral Nanosamples Using Photoinduced Force

NASA Astrophysics Data System (ADS)

Kamandi, Mohammad; Albooyeh, Mohammad; Guclu, Caner; Veysi, Mehdi; Zeng, Jinwei; Wickramasinghe, Kumar; Capolino, Filippo

2017-12-01

We propose a high-resolution microscopy technique for enantiospecific detection of chiral samples down to sub-100-nm size based on force measurement. We delve into the differential photoinduced optical force Δ F exerted on an achiral probe in the vicinity of a chiral sample when left and right circularly polarized beams separately excite the sample-probe interactive system. We analytically prove that Δ F is entangled with the enantiomer type of the sample enabling enantiospecific detection of chiral inclusions. Moreover, we demonstrate that Δ F is linearly dependent on both the chiral response of the sample and the electric response of the tip and is inversely related to the quartic power of probe-sample distance. We provide physical insight into the transfer of optical activity from the chiral sample to the achiral tip based on a rigorous analytical approach. We support our theoretical achievements by several numerical examples highlighting the potential application of the derived analytic properties. Lastly, we demonstrate the sensitivity of our method to enantiospecify nanoscale chiral samples with chirality parameter on the order of 0.01 and discuss how the sensitivity of our proposed technique can be further improved.

Chiral HPLC for a study of the optical purity of new liquid crystalline materials derived from lactic acid

NASA Astrophysics Data System (ADS)

Vojtylová, T.; Kašpar, M.; Hamplová, V.; Novotná, V.; Sýkora, D.

2014-08-01

New liquid crystalline (LC) materials were prepared by derivatization of lactic acid. First compound possesses the lactic acid unit as the only chiral center and the second group of LC materials contains two chiral centers. Mesomorphic properties of both the newly synthesized LC materials were studied and the presence of the SmA*-SmC* or exhibit the twist grain boundary (TGB) phases, namely TGBA and TGBC, in a wide range of temperatures down to the room temperature was established. The potential of high-performance liquid chromatography (HPLC) applying chiral stationary phases to separate enantiomers or diastereoisomers of the synthesized LC compounds was evaluated. Two different brands of commercial chiral sorbents, Lux Amylose-2 and Chiralpak AD-3, both based on modified silica with derivatized polysaccharide, were employed in the development of separation procedures. The optimized chiral HPLC method provided a baseline separation of the individual enantiomers for the LC material containing one chiral center. In the case of the more complex compound with two asymmetric carbon atoms, where four isomers exist, partial separation was reached only using the current chiral HPLC.

The combination of high Q factor and chirality in twin cavities and microcavity chain

PubMed Central

Song, Qinghai; Zhang, Nan; Zhai, Huilin; Liu, Shuai; Gu, Zhiyuan; Wang, Kaiyang; Sun, Shang; Chen, Zhiwei; Li, Meng; Xiao, Shumin

2014-01-01

Chirality in microcavities has recently shown its bright future in optical sensing and microsized coherent light sources. The key parameters for such applications are the high quality (Q) factor and large chirality. However, the previous reported chiral resonances are either low Q modes or require very special cavity designs. Here we demonstrate a novel, robust, and general mechanism to obtain the chirality in circular cavity. By placing a circular cavity and a spiral cavity in proximity, we show that ultra-high Q factor, large chirality, and unidirectional output can be obtained simultaneously. The highest Q factors of the non-orthogonal mode pairs are almost the same as the ones in circular cavity. And the co-propagating directions of the non-orthogonal mode pairs can be reversed by tuning the mode coupling. This new mechanism for the combination of high Q factor and large chirality is found to be very robust to cavity size, refractive index, and the shape deformation, showing very nice fabrication tolerance. And it can be further extended to microcavity chain and microcavity plane. We believe that our research will shed light on the practical applications of chirality and microcavities. PMID:25262881

Bulky melamine-based Zn-porphyrin tweezer as a CD probe of molecular chirality.

PubMed

Petrovic, Ana G; Vantomme, Ghislaine; Negrón-Abril, Yashira L; Lubian, Elisa; Saielli, Giacomo; Menegazzo, Ileana; Cordero, Roselynn; Proni, Gloria; Nakanishi, Koji; Carofiglio, Tommaso; Berova, Nina

2011-10-01

The transfer of chirality from a guest molecule to an achiral host is the subject of significant interest especially when, upon chiral induction, the chiroptical response of the host/guest complex can effectively report the absolute configuration (AC) of the guest. For more than a decade, dimeric metalloporphyrin hosts (tweezers) have been successfully applied as chirality probes for determination of the AC for a wide variety of chiral synthetic compounds and natural products. The objective of this study is to investigate the utility of a new class of melamine-bridged Zn-porphyrin tweezers as sensitive AC reporters. A combined approach based on an experimental CD analysis and a theoretical prediction of the prevailing interporphyrin helicity demonstrates that these tweezers display favorable properties for chiral recognition. Herein, we discuss the application of the melamine-bridged tweezer to the chiral recognition of a diverse set of chiral guests, such as 1,2-diamines, α-amino-esters and amides, secondary alcohols, and 1,2-amino-alcohols. The bulky periphery and the presence of a rigid porphyrin linkage lead, in some cases, to a more enhanced CD sensitivity than that reported earlier with other tweezers. Copyright © 2011 Wiley-Liss, Inc.

Broken chiral symmetry on a null plane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beane, Silas R., E-mail: silas@physics.unh.edu

2013-10-15

On a null-plane (light-front), all effects of spontaneous chiral symmetry breaking are contained in the three Hamiltonians (dynamical Poincaré generators), while the vacuum state is a chiral invariant. This property is used to give a general proof of Goldstone’s theorem on a null-plane. Focusing on null-plane QCD with N degenerate flavors of light quarks, the chiral-symmetry breaking Hamiltonians are obtained, and the role of vacuum condensates is clarified. In particular, the null-plane Gell-Mann–Oakes–Renner formula is derived, and a general prescription is given for mapping all chiral-symmetry breaking QCD condensates to chiral-symmetry conserving null-plane QCD condensates. The utility of the null-planemore » description lies in the operator algebra that mixes the null-plane Hamiltonians and the chiral symmetry charges. It is demonstrated that in a certain non-trivial limit, the null-plane operator algebra reduces to the symmetry group SU(2N) of the constituent quark model. -- Highlights: •A proof (the first) of Goldstone’s theorem on a null-plane is given. •The puzzle of chiral-symmetry breaking condensates on a null-plane is solved. •The emergence of spin-flavor symmetries in null-plane QCD is demonstrated.« less

Coupling mesodomain positional ordering to intra-domain orientational ordering in block copolymer assembly

NASA Astrophysics Data System (ADS)

Burke, Christopher; Reddy, Abhiram; Prasad, Ishan; Grason, Gregory

Block copolymer (BCP) melts form a number of symmetric microphases, e.g. columnar or double gyroid phases. BCPs with a block composed of chiral monomers are observed to form bulk phases with broken chiral symmetry e.g. a phase of hexagonally ordered helical mesodomains. Other new structures may be possible, e.g. double gyroid with preferred chirality which has potential photonic applications. One approach to understanding chirality transfer from monomer to the bulk is to use self consistent field theory (SCFT) and incorporate an orientational order parameter with a preference for handed twist in chiral block segments, much like the texture of cholesteric liquid crystal. Polymer chains in achiral BCPs exhibit orientational ordering which couples to the microphase geometry; a spontaneous preference for ordering may have an effect on the geometry. The influence of a preference for chiral polar (vectorial) segment order has been studied to some extent, though the influence of coupling to chiral tensorial (nematic) order has not yet been developed. We present a computational approach using SCFT with vector and tensor order which employs well developed pseudo-spectral methods. Using this we explore how tensor order influences which structures form, and if it can promote chiral phases.

Chiral stationary phase optimized selectivity liquid chromatography: A strategy for the separation of chiral isomers.

PubMed

Hegade, Ravindra Suryakant; De Beer, Maarten; Lynen, Frederic

2017-09-15

Chiral Stationary-Phase Optimized Selectivity Liquid Chromatography (SOSLC) is proposed as a tool to optimally separate mixtures of enantiomers on a set of commercially available coupled chiral columns. This approach allows for the prediction of the separation profiles on any possible combination of the chiral stationary phases based on a limited number of preliminary analyses, followed by automated selection of the optimal column combination. Both the isocratic and gradient SOSLC approach were implemented for prediction of the retention times for a mixture of 4 chiral pairs on all possible combinations of the 5 commercial chiral columns. Predictions in isocratic and gradient mode were performed with a commercially available and with an in-house developed Microsoft visual basic algorithm, respectively. Optimal predictions in the isocratic mode required the coupling of 4 columns whereby relative deviations between the predicted and experimental retention times ranged between 2 and 7%. Gradient predictions led to the coupling of 3 chiral columns allowing baseline separation of all solutes, whereby differences between predictions and experiments ranged between 0 and 12%. The methodology is a novel tool allowing optimizing the separation of mixtures of optical isomers. Copyright © 2017 Elsevier B.V. All rights reserved.

Chiral quantum dot based materials

NASA Astrophysics Data System (ADS)

Govan, Joseph; Loudon, Alexander; Baranov, Alexander V.; Fedorov, Anatoly V.; Gun'ko, Yurii

2014-05-01

Recently, the use of stereospecific chiral stabilising molecules has also opened another avenue of interest in the area of quantum dot (QD) research. The main goal of our research is to develop new types of technologically important quantum dot materials containing chiral defects, study their properties and explore their applications. The utilisation of chiral penicillamine stabilisers allowed the preparation of new water soluble white emitting CdS quantum nanostructures which demonstrated circular dichroism in the band-edge region of the spectrum. It was also demonstrated that all three types of QDs (D-, L-, and Rac penicillamine stabilised) show very broad emission bands between 400 and 700 nm due to defects or trap states on the surfaces of the nanocrystals. In this work the chiral CdS based quantum nanostructures have also been doped by copper metal ions and new chiral penicilamine stabilized CuS nanoparticles have been prepared and investigated. It was found that copper doping had a strong effect at low levels in the synthesis of chiral CdS nanostructures. We expect that this research will open new horizons in the chemistry of chiral nanomaterials and their application in biotechnology, sensing and asymmetric synthesis.

Experimental Evidence of Chiral Ferrimagnetism in Amorphous GdCo Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Streubel, Robert; Lambert, Charles-Henri; Kent, Noah

Inversion symmetry breaking has become a vital research area in modern magnetism with phenomena including the Rashba effect, spin Hall effect, and the Dzyaloshinskii-Moriya interaction (DMI)-a vector spin exchange. The latter one may stabilize chiral spin textures with topologically nontrivial properties, such as Skyrmions. So far, chiral spin textures have mainly been studied in helimagnets and thin ferromagnets with heavy-element capping. Here, the concept of chirality driven by interfacial DMI is generalized to complex multicomponent systems and demonstrated on the example of chiral ferrimagnetism in amorphous GdCo films. Utilizing Lorentz microscopy and X-ray magnetic circular dichroism spectroscopy, and tailoring thickness,more » capping, and rare-earth composition, reveal that 2 nm thick GdCo films preserve ferrimagnetism and stabilize chiral domain walls. Finally, the type of chiral domain walls depends on the rare-earth composition/saturation magnetization, enabling a possible temperature control of the intrinsic properties of ferrimagnetic domain walls.« less

Chiral symmetry breaking by spatial confinement in tactoidal droplets of lyotropic chromonic liquid crystals

PubMed Central

Tortora, Luana; Lavrentovich, Oleg D.

2011-01-01

In many colloidal systems, an orientationally ordered nematic (N) phase emerges from the isotropic (I) melt in the form of spindle-like birefringent tactoids. In cases studied so far, the tactoids always reveal a mirror-symmetric nonchiral structure, sometimes even when the building units are chiral. We report on chiral symmetry breaking in the nematic tactoids formed in molecularly nonchiral polymer-crowded aqueous solutions of low-molecular weight disodium cromoglycate. The parity is broken by twisted packing of self-assembled molecular aggregates within the tactoids as manifested by the observed optical activity. Fluorescent confocal microscopy reveals that the chiral N tactoids are located at the boundaries of cells. We explain the chirality induction as a replacement of energetically costly splay packing of the aggregates within the curved bipolar tactoidal shape with twisted packing. The effect represents a simple pathway of macroscopic chirality induction in an organic system with no molecular chirality, as the only requirements are orientational order and curved shape of confinement. PMID:21402929

In situ evidence for chirality-dependent growth rates of individual carbon nanotubes

NASA Astrophysics Data System (ADS)

Rao, Rahul; Liptak, David; Cherukuri, Tonya; Yakobson, Boris I.; Maruyama, Benji

2012-03-01

Chiral-selective growth of single-walled carbon nanotubes (SWNTs) remains a great challenge that hinders their use in applications such as electronics and medicine. Recent experimental and theoretical reports have begun to address this problem by suggesting that selectivity may be achieved during nucleation by changing the catalyst composition or structure. Nevertheless, to establish a rational basis for chiral-selective synthesis, the underlying mechanisms governing nucleation, growth, and termination of SWNTs must be better understood. To this end, we report the first measurements of growth rates of individual SWNTs through in situ Raman spectroscopy and correlate them with their chiral angles. Our results show that the growth rates are directly proportional to the chiral angles, in agreement with recent theoretical predictions. Importantly, the evidence singles out the growth stage as responsible for the chiral distribution—distinct from nucleation and termination which might also affect the final product distribution. Our results suggest a route to chiral-selective synthesis of SWNTs through rational synthetic design strategies based on kinetic control.

Dynamics of vortex domain walls in ferromagnetic nanowires - A possible method for chirality manipulation

NASA Astrophysics Data System (ADS)

Li, Y.; Lu, Z.; Chen, C.; Cheng, M.; Yin, H.; Wang, W.; Li, C.; Liu, Y.; Xiong, R.; Shi, J.

2018-06-01

The dynamic behaviors of vortex domain walls (VDWs) in ferromagnetic nanowires driven by a magnetic field above Walker breakdown field (Hw) were investigated using micromagnetic simulation. It was found when nanowire has proper geometrical dimensions, the VDW may oscillate in a chirality invariant mode or a chirality switching mode depending on applied field and damping constant. At fixed damping constant, the oscillation mode can be controlled by applied field - with the increase of applied field, the oscillation of VDW change from a chirality invariant mode to a variant one. As the oscillation of VDW changes from chirality invariant regime to chirality switching regime, the oscillation frequency and amplification will undergo an abnormal change, which may offer a fingerprint for the switch of oscillation mode. Our finding proposes a simple way to control the chirality of a VDW by properly manipulating nanowire geometry and applied field, which may have important applications in VDW-based devices.

Macdonald index and chiral algebra

NASA Astrophysics Data System (ADS)

Song, Jaewon

2017-08-01

For any 4d N = 2 SCFT, there is a subsector described by a 2d chiral algebra. The vacuum character of the chiral algebra reproduces the Schur index of the corresponding 4d theory. The Macdonald index counts the same set of operators as the Schur index, but the former has one more fugacity than the latter. We conjecture a prescription to obtain the Macdonald index from the chiral algebra. The vacuum module admits a filtration, from which we construct an associated graded vector space. From this grading, we conjecture a notion of refined character for the vacuum module of a chiral algebra, which reproduces the Macdonald index. We test this prescription for the Argyres-Douglas theories of type ( A 1 , A 2 n ) and ( A 1 , D 2 n+1) where the chiral algebras are given by Virasoro and \\widehat{su}(2) affine Kac-Moody algebra. When the chiral algebra has more than one family of generators, our prescription requires a knowledge of the generators from the 4d.

Novel electrochemical method for the characterization of the degree of chirality in chiral polyaniline.

PubMed

Feng, Zhang; Li, Ma; Yan, Yang; Jihai, Tang; Xiao, Li; Wanglin, Li

2013-01-01

A novel method to indicate the degree of chirality in polyaniline (PANI) was developed. The (D-camphorsulfonic acid)- and (HCl)-PANI-based electrodes exhibited significantly different electrochemical performances in D- and L-Alanine (Ala) aqueous solution, respectively, which can be used for the characterization the optical activity of chiral PANI. Cyclic voltammogram, tafel, and open circuit potential of PANI-based electrodes were measured within D- and L-Ala electrolyte solution, respectively. The open circuit potentials under different reacting conditions were analyzed by Doblhofer model formula, in which [C(+)](poly1)/[C(+)](poly2) was used as a parameter to characterize the degree of chirality in chiral PANI. The results showed that [C(+)](poly1)/[C(+)](poly2) can be increased with increasing concentrations of (1S)-(+)- and (1R)-(-)-10-camphorsulfonic acid. In addition, we detected that appropriate response time and lower temperature are necessary to improve the degree of chirality. Copyright © 2012 Wiley Periodicals, Inc.

Electromagnetic wave propagation through a dielectric-chiral interface and through a chiral slab

NASA Technical Reports Server (NTRS)

Bassiri, S.; Papas, C. H.; Engheta, N.

1988-01-01

The reflection from and transmission through a semiinfinite chiral medium are analyzed by obtaining the Fresnel equations in terms of parallel- and perpendicular-polarized modes, and a comparison is made with results reported previously. The chiral medium is described electromagnetically by the constitutive relations D = (epsilon)E+i(gamma)B and H = i(gamma)E+(1/mu)B. The constants epsilon, mu and gamma are real and have values that are fixed by the size, the shape, and the spatial distribution of the elements that collectively compose the medium. The conditions are obtained for the total internal reflection of the incident wave from the interface and for the existence of the Brewster angle. The effects of the chirality on the polarization and the intensity of the reflected wave from the chiral half-space are discussed and illustrated by using the Stokes parameters. The propagation of electromagnetic wave through an infinite slab of chiral medium is formulated for oblique incidence and solved analytically for the case of normal incidence.

Chiral geometry in multiple chiral doublet bands

NASA Astrophysics Data System (ADS)

Zhang, Hao; Chen, Qibo

2016-02-01

The chiral geometry of multiple chiral doublet bands with identical configuration is discussed for different triaxial deformation parameters γ in the particle rotor model with . The energy spectra, electromagnetic transition probabilities B(M1) and B(E2), angular momenta, and K-distributions are studied. It is demonstrated that the chirality still remains not only in the yrast and yrare bands, but also in the two higher excited bands when γ deviates from 30°. The chiral geometry relies significantly on γ, and the chiral geometry of the two higher excited partner bands is not as good as that of the yrast and yrare doublet bands. Supported by Plan Project of Beijing College Students’ Scientific Research and Entrepreneurial Action, Major State 973 Program of China (2013CB834400), National Natural Science Foundation of China (11175002, 11335002, 11375015, 11461141002), National Fund for Fostering Talents of Basic Science (NFFTBS) (J1103206), Research Fund for Doctoral Program of Higher Education (20110001110087) and China Postdoctoral Science Foundation (2015M580007)

Incommensurate Chirality Density Wave Transition in a Hybrid Molecular Framework.

PubMed

Hill, Joshua A; Christensen, Kirsten E; Goodwin, Andrew L

2017-09-15

Using single-crystal x-ray diffraction we characterize the 235 K incommensurate phase transition in the hybrid molecular framework tetraethylammonium silver(I) dicyanoargentate, [NEt_{4}]Ag_{3}(CN)_{4}. We demonstrate the transition to involve spontaneous resolution of chiral [NEt_{4}]^{+} conformations, giving rise to a state in which molecular chirality is incommensurately modulated throughout the crystal lattice. We refer to this state as an incommensurate chirality density wave (XDW) phase, which represents a fundamentally new type of chiral symmetry breaking in the solid state. Drawing on parallels to the incommensurate ferroelectric transition of NaNO_{2}, we suggest the XDW state arises through coupling between acoustic (shear) and molecular rotoinversion modes. Such coupling is symmetry forbidden at the Brillouin zone center but symmetry allowed for small but finite modulation vectors q=[0,0,q_{z}]^{*}. The importance of long-wavelength chirality modulations in the physics of this hybrid framework may have implications for the generation of mesoscale chiral textures, as required for advanced photonic materials.

Incommensurate Chirality Density Wave Transition in a Hybrid Molecular Framework

NASA Astrophysics Data System (ADS)

Hill, Joshua A.; Christensen, Kirsten E.; Goodwin, Andrew L.

2017-09-01

Using single-crystal x-ray diffraction we characterize the 235 K incommensurate phase transition in the hybrid molecular framework tetraethylammonium silver(I) dicyanoargentate, [NEt4]Ag3(CN )4 . We demonstrate the transition to involve spontaneous resolution of chiral [NEt4]+ conformations, giving rise to a state in which molecular chirality is incommensurately modulated throughout the crystal lattice. We refer to this state as an incommensurate chirality density wave (XDW) phase, which represents a fundamentally new type of chiral symmetry breaking in the solid state. Drawing on parallels to the incommensurate ferroelectric transition of NaNO2 , we suggest the XDW state arises through coupling between acoustic (shear) and molecular rotoinversion modes. Such coupling is symmetry forbidden at the Brillouin zone center but symmetry allowed for small but finite modulation vectors q =[0 ,0 ,qz]* . The importance of long-wavelength chirality modulations in the physics of this hybrid framework may have implications for the generation of mesoscale chiral textures, as required for advanced photonic materials.

On vibrational circular dichroism chirality transfer in electron donor-acceptor complexes: a prediction for the quinine···BF3 system.

PubMed

Rode, Joanna E; Jamróz, Michał H; Dobrowolski, Jan Cz; Sadlej, Joanna

2012-08-02

Vibrational circular dichroism (VCD) chirality transfer occurs when an achiral molecule interacts with a chiral one and becomes VCD-active. Unlike for H-bonds, for organic electron donor-acceptor (EDA) complexes this phenomenon remains almost unknown. Here, the VCD chirality transfer from chiral quinine to achiral BF3 is studied at the B3LYP/aug-cc-pVDZ level. Accessibility of four quinine electron donor sites changes with conformation. Therefore, the quinine conformational landscape was explored and a considerable agreement between X-ray and the most stable conformer geometries was achieved. The BF3 complex through the aliphatic quinuclidine N atom is definitely dominating and is predicted to be easily recognizable in the VCD spectrum. Out of several VCD chirality transfer modes, the ν(s)(BF3) mode, the most intense in the entire VCD spectrum, satisfies the VCD mode robustness criterion and can be used for monitoring the chirality transfer phenomenon in quinine···BF3 system.

Experimental Evidence of Chiral Ferrimagnetism in Amorphous GdCo Films

DOE PAGES

Streubel, Robert; Lambert, Charles-Henri; Kent, Noah; ...

2018-05-23

Inversion symmetry breaking has become a vital research area in modern magnetism with phenomena including the Rashba effect, spin Hall effect, and the Dzyaloshinskii-Moriya interaction (DMI)-a vector spin exchange. The latter one may stabilize chiral spin textures with topologically nontrivial properties, such as Skyrmions. So far, chiral spin textures have mainly been studied in helimagnets and thin ferromagnets with heavy-element capping. Here, the concept of chirality driven by interfacial DMI is generalized to complex multicomponent systems and demonstrated on the example of chiral ferrimagnetism in amorphous GdCo films. Utilizing Lorentz microscopy and X-ray magnetic circular dichroism spectroscopy, and tailoring thickness,more » capping, and rare-earth composition, reveal that 2 nm thick GdCo films preserve ferrimagnetism and stabilize chiral domain walls. Finally, the type of chiral domain walls depends on the rare-earth composition/saturation magnetization, enabling a possible temperature control of the intrinsic properties of ferrimagnetic domain walls.« less

Macdonald index and chiral algebra

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Jaewon

For any 4dN = 2 SCFT, there is a subsector described by a 2d chiral algebra. The vacuum character of the chiral algebra reproduces the Schur index of the corresponding 4d theory. The Macdonald index counts the same set of operators as the Schur index, but the former has one more fugacity than the latter. Here, we conjecture a prescription to obtain the Macdonald index from the chiral algebra. The vacuum module admits a filtration, from which we construct an associated graded vector space. From this grading, we conjecture a notion of refined character for the vacuum module of a chiral algebra, which reproduces the Macdonald index. We test this prescription for the Argyres-Douglas theories of type (A 1, A 2n) and (A 1, D 2n+1) where the chiral algebras are given by Virasoro andmore » $$ˆ\\atop{su}$$(2) affine Kac-Moody algebra. When the chiral algebra has more than one family of generators, our prescription requires a knowledge of the generators from the 4d.« less

Macdonald index and chiral algebra

DOE PAGES

Song, Jaewon

2017-08-10

For any 4dN = 2 SCFT, there is a subsector described by a 2d chiral algebra. The vacuum character of the chiral algebra reproduces the Schur index of the corresponding 4d theory. The Macdonald index counts the same set of operators as the Schur index, but the former has one more fugacity than the latter. Here, we conjecture a prescription to obtain the Macdonald index from the chiral algebra. The vacuum module admits a filtration, from which we construct an associated graded vector space. From this grading, we conjecture a notion of refined character for the vacuum module of a chiral algebra, which reproduces the Macdonald index. We test this prescription for the Argyres-Douglas theories of type (A 1, A 2n) and (A 1, D 2n+1) where the chiral algebras are given by Virasoro andmore » $$ˆ\\atop{su}$$(2) affine Kac-Moody algebra. When the chiral algebra has more than one family of generators, our prescription requires a knowledge of the generators from the 4d.« less

First-order chiral to non-chiral transition in the angular dependence of the upper critical induction of the Scharnberg-Klemm p-wave pair state

NASA Astrophysics Data System (ADS)

Klemm, Richard; Zhang, Jingchuan; Lorscher, Christopher; Gu, Qiang

2014-03-01

We calculate the temperature T and angular (θ , ϕ) dependence of the upper critical induction Bc 2(θ , ϕ , T) for parallel-spin superconductors with an axially symmetric p-wave pairing interaction pinned to the lattice and a dominant ellipsoidal Fermi surface (FS). When both parallel-spin states are allowed, the chiral Scharnberg-Klemm state Bc 2(θ , ϕ , T) exceeds that of the chiral Anderson-Brinkman-Morel state for all FS anisotropies, and exhibits a kink at θ =θ*(T , ϕ) , indicative of a first-order transition from its chiral, nodal-direction behavior to its non-chiral, antinodal-direction behavior. Potential applicability to Sr2RuO4, UCoGe, and topological superconductors is discussed.

Application of classical models of chirality to optical rectification

NASA Astrophysics Data System (ADS)

Wang, Xiao-Ou; Gong, Li-Jing; Li, Chun-Fei

2008-08-01

Classical models of chirality are used to investigate the optical rectification effect in chiral molecular media. Calculation of the zero frequency first hyperpolarizabilities of chiral molecules with different structures is performed and applied to the derivation of a dc electric-dipole polarization. The expression of second-order nonlinear static-electric-dipole susceptibilities is obtained by theoretical derivation in the isotropic chiral thin films. The microscopic mechanism producing optical rectification is analyzed in view of this calculation. We find that optical rectification is derived from interaction between the electric field gradient (spatial dispersion) and chiral molecules in optically active liquids and solution by our calculation, which is consistent with the result given by Woźniak and Wagnière [Opt. Commun. 114, 131 (1995)]: The optical rectification depends on the fourth-order electric-dipole susceptibilities.

Topologically massive higher spin gravity

NASA Astrophysics Data System (ADS)

Bagchi, Arjun; Lal, Shailesh; Saha, Arunabha; Sahoo, Bindusar

2011-10-01

We look at the generalisation of topologically massive gravity (TMG) to higher spins, specifically spin-3. We find a special "chiral" point for the spin-three, analogous to the spin-two example, which actually coincides with the usual spin-two chiral point. But in contrast to usual TMG, there is the presence of a non-trivial trace and its logarithmic partner at the chiral point. The trace modes carry energy opposite in sign to the traceless modes. The logarithmic partner of the traceless mode carries negative energy indicating an instability at the chiral point. We make several comments on the asymptotic symmetry and its possible deformations at this chiral point and speculate on the higher spin generalisation of LCFT2 dual to the spin-3 massive gravity at the chiral point.

Shape selection of twist-nematic-elastomer ribbons

PubMed Central

Sawa, Yoshiki; Ye, Fangfu; Urayama, Kenji; Takigawa, Toshikazu; Gimenez-Pinto, Vianney; Selinger, Robin L. B.; Selinger, Jonathan V.

2011-01-01

How microscopic chirality is reflected in macroscopic scale to form various chiral shapes, such as straight helicoids and spiral ribbons, and how the degree of macroscopic chirality can be controlled are a focus of studies on the shape formation of many biomaterials and supramolecular systems. This article investigates both experimentally and theoretically how the chiral arrangement of liquid crystal mesogens in twist-nematic-elastomer films induces the formation of helicoids and spiral ribbons because of the coupling between the liquid crystalline order and the elasticity. It is also shown that the pitch of the formed ribbons can be tuned by temperature variation. The results of this study will facilitate the understanding of physics for the shape formation of chiral materials and the designing of new structures on basis of microscopic chirality. PMID:21464276

Controlling Chirality of Entropic Crystals

NASA Astrophysics Data System (ADS)

Damasceno, Pablo F.; Karas, Andrew S.; Schultz, Benjamin A.; Engel, Michael; Glotzer, Sharon C.

2015-10-01

Colloidal crystal structures with complexity and diversity rivaling atomic and molecular crystals have been predicted and obtained for hard particles by entropy maximization. However, thus far homochiral colloidal crystals, which are candidates for photonic metamaterials, are absent. Using Monte Carlo simulations we show that chiral polyhedra exhibiting weak directional entropic forces self-assemble either an achiral crystal or a chiral crystal with limited control over the crystal handedness. Building blocks with stronger faceting exhibit higher selectivity and assemble a chiral crystal with handedness uniquely determined by the particle chirality. Tuning the strength of directional entropic forces by means of particle rounding or the use of depletants allows for reconfiguration between achiral and homochiral crystals. We rationalize our findings by quantifying the chirality strength of each particle, both from particle geometry and potential of mean force and torque diagrams.

Phase behavior of thermotropic chiral liquid crystal with wide blue phase

NASA Astrophysics Data System (ADS)

Jessy, P. J.; Radha, S.; Nainesh, Patel

2018-04-01

We modified the phase transitions of a thermotropic chiral nematic liquid crystal system with various concentrations of chiral component and investigated their phase behavior and optical properties. The study shows that coupling between chirality and nematicity of liquid crystals lead to changes in phase morphology with extended temperature window of blue phase including human body temperatures and enhanced thermochromism performance. The temperature dependent refractive index analysis in the visible spectral region reveals that the optical modulation due to pitch variation of helical pattern results in the creation of new mesophases and more pronounced chirality in mixtures leading to blue phase which can be controlled by the chiral concentration. The appearance of extended blue phases with primary colors will pave way for the development of new photonic devices.

Chiral tunneling in a twisted graphene bilayer.

PubMed

He, Wen-Yu; Chu, Zhao-Dong; He, Lin

2013-08-09

The perfect transmission in a graphene monolayer and the perfect reflection in a Bernal graphene bilayer for electrons incident in the normal direction of a potential barrier are viewed as two incarnations of the Klein paradox. Here we show a new and unique incarnation of the Klein paradox. Owing to the different chiralities of the quasiparticles involved, the chiral fermions in a twisted graphene bilayer show an adjustable probability of chiral tunneling for normal incidence: they can be changed from perfect tunneling to partial or perfect reflection, or vice versa, by controlling either the height of the barrier or the incident energy. As well as addressing basic physics about how the chiral fermions with different chiralities tunnel through a barrier, our results provide a facile route to tune the electronic properties of the twisted graphene bilayer.

Remote Central-to-Axial Chirality Conversion: Direct Atroposelective Ester to Biaryl Transformation.

PubMed

Link, Achim; Sparr, Christof

2018-05-16

A strategy for the remote central-to-axial chirality conversion by simultaneous planarization of an encoding and a transient stereocenter is presented. Based on a diastereoselective double addition of a chiral 1,5-bifunctional organomagnesium alkoxide reagent to a broad range of aryl ester substrates, axially chiral biaryls are directly obtained upon in situ reduction. Various structurally distinct atropisomeric biaryl silanes that serve as valuable chiral biaryl anion surrogates are accessible in one step with e.r. values of up to 98:2. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Origin of chiral interactions in cellulose supra-molecular microfibrils.

PubMed

Khandelwal, Mudrika; Windle, Alan

2014-06-15

The formation of a chiral-nematic phase from cellulose nanowhiskers has been frequently reported in the literature. The most popular theory used to explain the chiral interactions is that of twisted morphology of cellulose nanowhiskers. Two possible origins of twist have been suggested: the intrinsic chirality of cellulose chains and result of interaction of chiral surfaces. High resolution SEM and AFM have been used to locate twists in cellulose microfibrils and nanowhiskers. The origin of the twisted morphology in cellulose microfibrils has been studied with reference to the protein aggregation theory. Copyright © 2014 Elsevier Ltd. All rights reserved.

Experimental Overview of the Search for Chiral Effects at RHIC

NASA Astrophysics Data System (ADS)

Wang, Gang

2017-01-01

In high-energy heavy-ion collisions, various novel transport phenomena in local chiral domains result from the interplay of quantum anomalies with magnetic field and vorticity, and could survive the expansion of the fireball and be detected in experiments. Among these phenomena are the chiral magnetic effect, the chiral vortical effect and the chiral magnetic wave, the experimental searches for which have aroused extensive interest. This review will describe the current status of experimental studies at Relativistic Heavy Ion Collider at BNL, and outline the future work in experiment needed to eliminate the existing uncertainties in the interpretation of the data.

Multiple Chirality in Nuclear Rotation: A Microscopic View

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, P. W.

Covariant density functional theory and three-dimensional tilted axis cranking are used to investigate multiple chirality in nuclear rotation for the first time in a fully self-consistent and microscopic way. Two distinct sets of chiral solutions with negative and positive parities, respectively, are found in the nucleus 106Rh. The negative-parity solutions reproduce well the corresponding experimental spectrum as well as the B(M1)/B(E2) ratios of the transition strengths. Finally, this indicates that a predicted positive-parity chiral band should also exist. Therefore, it provides a further strong hint that multiple chirality is realized in nuclei.

Circularly polarized guided modes in dielectrically chiral photonic crystal fiber.

PubMed

Li, Junqing; Su, Qiyao; Cao, Yusheng

2010-08-15

The effect of dielectric chirality on the polarization states and mode indices of guided modes in photonic crystal fiber (PCF) is investigated by a modified plane-wave expansion (PWE) method. Using a solid-core chiral PCF as a numerical example, we show that circular polarization is the eigenstate of the fundamental mode. Mode index divergence between right-handed circularly polarized (RCP) and left-handed circularly polarized (LCP) states is demonstrated. Chirality's effect on mode index and circular birefringence (CB) in such a PCF is found to be similar to that in bulk chiral media.

Multiple Chirality in Nuclear Rotation: A Microscopic View

DOE PAGES

Zhao, P. W.

2017-10-10

Covariant density functional theory and three-dimensional tilted axis cranking are used to investigate multiple chirality in nuclear rotation for the first time in a fully self-consistent and microscopic way. Two distinct sets of chiral solutions with negative and positive parities, respectively, are found in the nucleus 106Rh. The negative-parity solutions reproduce well the corresponding experimental spectrum as well as the B(M1)/B(E2) ratios of the transition strengths. Finally, this indicates that a predicted positive-parity chiral band should also exist. Therefore, it provides a further strong hint that multiple chirality is realized in nuclei.

The interplay of covalency, hydrogen bonding, and dispersion leads to a long range chiral network: The example of 2-butanol

NASA Astrophysics Data System (ADS)

Liriano, Melissa L.; Carrasco, Javier; Lewis, Emily A.; Murphy, Colin J.; Lawton, Timothy J.; Marcinkowski, Matthew D.; Therrien, Andrew J.; Michaelides, Angelos; Sykes, E. Charles H.

2016-03-01

The assembly of complex structures in nature is driven by an interplay between several intermolecular interactions, from strong covalent bonds to weaker dispersion forces. Understanding and ultimately controlling the self-assembly of materials requires extensive study of how these forces drive local nanoscale interactions and how larger structures evolve. Surface-based self-assembly is particularly amenable to modeling and measuring these interactions in well-defined systems. This study focuses on 2-butanol, the simplest aliphatic chiral alcohol. 2-butanol has recently been shown to have interesting properties as a chiral modifier of surface chemistry; however, its mode of action is not fully understood and a microscopic understanding of the role non-covalent interactions play in its adsorption and assembly on surfaces is lacking. In order to probe its surface properties, we employed high-resolution scanning tunneling microscopy and density functional theory (DFT) simulations. We found a surprisingly rich degree of enantiospecific adsorption, association, chiral cluster growth and ultimately long range, highly ordered chiral templating. Firstly, the chiral molecules acquire a second chiral center when adsorbed to the surface via dative bonding of one of the oxygen atom lone pairs. This interaction is controlled via the molecule's intrinsic chiral center leading to monomers of like chirality, at both chiral centers, adsorbed on the surface. The monomers then associate into tetramers via a cyclical network of hydrogen bonds with an opposite chirality at the oxygen atom. The evolution of these square units is surprising given that the underlying surface has a hexagonal symmetry. Our DFT calculations, however, reveal that the tetramers are stable entities that are able to associate with each other by weaker van der Waals interactions and tessellate in an extended square network. This network of homochiral square pores grows to cover the whole Au(111) surface. Our data reveal that the chirality of a simple alcohol can be transferred to its surface binding geometry, drive the directionality of hydrogen-bonded networks and ultimately extended structure. Furthermore, this study provides the first microscopic insight into the surface properties of this important chiral modifier and provides a well-defined system for studying the network's enantioselective interaction with other molecules.

The interplay of covalency, hydrogen bonding, and dispersion leads to a long range chiral network: The example of 2-butanol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liriano, Melissa L.; Lewis, Emily A.; Murphy, Colin J.

The assembly of complex structures in nature is driven by an interplay between several intermolecular interactions, from strong covalent bonds to weaker dispersion forces. Understanding and ultimately controlling the self-assembly of materials requires extensive study of how these forces drive local nanoscale interactions and how larger structures evolve. Surface-based self-assembly is particularly amenable to modeling and measuring these interactions in well-defined systems. This study focuses on 2-butanol, the simplest aliphatic chiral alcohol. 2-butanol has recently been shown to have interesting properties as a chiral modifier of surface chemistry; however, its mode of action is not fully understood and a microscopicmore » understanding of the role non-covalent interactions play in its adsorption and assembly on surfaces is lacking. In order to probe its surface properties, we employed high-resolution scanning tunneling microscopy and density functional theory (DFT) simulations. We found a surprisingly rich degree of enantiospecific adsorption, association, chiral cluster growth and ultimately long range, highly ordered chiral templating. Firstly, the chiral molecules acquire a second chiral center when adsorbed to the surface via dative bonding of one of the oxygen atom lone pairs. This interaction is controlled via the molecule’s intrinsic chiral center leading to monomers of like chirality, at both chiral centers, adsorbed on the surface. The monomers then associate into tetramers via a cyclical network of hydrogen bonds with an opposite chirality at the oxygen atom. The evolution of these square units is surprising given that the underlying surface has a hexagonal symmetry. Our DFT calculations, however, reveal that the tetramers are stable entities that are able to associate with each other by weaker van der Waals interactions and tessellate in an extended square network. This network of homochiral square pores grows to cover the whole Au(111) surface. Our data reveal that the chirality of a simple alcohol can be transferred to its surface binding geometry, drive the directionality of hydrogen-bonded networks and ultimately extended structure. Furthermore, this study provides the first microscopic insight into the surface properties of this important chiral modifier and provides a well-defined system for studying the network’s enantioselective interaction with other molecules.« less

Enantioselective Cobalt-Catalyzed Sequential Nazarov Cyclization/Electrophilic Fluorination: Access to Chiral α-Fluorocyclopentenones.

PubMed

Zhang, Heyi; Cheng, Biao; Lu, Zhan

2018-06-20

A newly designed thiazoline iminopyridine ligand for enantioselective cobalt-catalyzed sequential Nazarov cyclization/electrophilic fluorination was developed. Various chiral α-fluorocyclopentenones were prepared with good yields and diastereo- and enantioselectivities. Further derivatizations could be easily carried out to provide chiral cyclopentenols with three contiguous stereocenters. Furthermore, a direct deesterification of fluorinated products could afford chiral α-single fluorine-substituted cyclopentenones.

Influence of a change in helical twisting power of photoresponsive chiral dopants on rotational manipulation of micro-objects on the surface of chiral nematic liquid crystalline films.

PubMed

Thomas, Reji; Yoshida, Yohei; Akasaka, Takehito; Tamaoki, Nobuyuki

2012-09-24

Herein we report a group of five planar chiral molecules as photon-mode chiral switches for the reversible control of the self-assembled superstructures of doped chiral nematic liquid crystals. The chiral switches are composed of an asymmetrically substituted aromatic moiety and a photoisomerizing azobenzene unit connected in a cyclic manner through methylene spacers of varying lengths. All the molecules show conformational restriction in the rotation of the asymmetrically substituted aromatic moiety in both the E and Z states of the azobenzene units resulting in planar chirality with separable enantiomers. Our newly synthesized compounds in pure enantiomeric form show high helical twisting power (HTP) in addition to an improved change in HTP between the E and Z states. The molecule with a diphenylnaphthalene unit shows the highest ever known initial helical twisting power among chiral dopants with planar chirality. In addition to the reversible tuning of reflection colors, we employed the enantiomers of these five compounds in combination with four nematic liquid crystalline hosts to study their properties as molecular machines; the change in HTP of the chiral dopant upon photoisomerization induces rotation of the texture of the liquid crystal surfaces. Importantly, this study has revealed a linear dependence of the ratio of the difference between HTPs before and after irradiation against the absolute value of the initial HTP, not the absolute value of the change in helical twisting power between two states, on the angle of rotation of micro-objects on chiral nematic liquid crystalline films. This study has also revealed that a change in irradiation intensity does not affect the maximum angle of rotation, but it does affect the speed of rotational reorganization of the cholesteric helix. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of molecular chirality on self-assembly and switching in liquid crystals at the cross-over between rod-like and bent shapes.

PubMed

Ocak, Hale; Poppe, Marco; Bilgin-Eran, Belkız; Karanlık, Gürkan; Prehm, Marko; Tschierske, Carsten

2016-09-21

A bent-core compound derived from a 4-cyanoresorcinol core unit with two terephthalate based rod-like wings and carrying chiral 3,7-dimethyloctyloxy side chains has been synthesized in racemic and enantiomerically pure form and characterized by polarizing microscopy, differential scanning calorimetry, X-ray diffraction and electro-optical investigations to study the influence of molecular chirality on the superstructural chirality and polar order in lamellar liquid crystalline phases. Herein we demonstrate that the coupling of molecular chirality with superstructural layer chirality in SmCsPF domain phases (forming energetically distinct diastereomeric pairs) can fix the tilt direction and thus stabilize synpolar order, leading to bistable ferroelectric switching in the SmC* phases of the (S)-enantiomer, whereas tristable modes determine the switching of the racemate. Moreover, the mechanism of electric field induced molecular reorganization changes from a rotation around the molecular long axis in the racemate to a rotation on the tilt-cone for the (S)-enantiomer. At high temperature the enantiomer behaves like a rod-like molecule with a chirality induced ferroelectric SmC* phase and an electroclinic effect in the SmA'* phase. At reduced temperature sterically induced polarization, due to the bent molecular shape, becomes dominating, leading to much higher polarization values, thus providing access to high polarization ferroelectric materials with weakly bent compounds having only "weakly chiral" stereogenic units. Moreover, the field induced alignment of the SmCsPF(()*()) domains gives rise to a special kind of electroclinic effect appearing even in the absence of molecular chirality. Comparison with related compounds indicates that the strongest effects of chirality appear for weakly bent molecules with a relatively short coherence length of polar order, whereas for smectic phases with long range polar order the effects of the interlayer interfaces can override the chirality effects.

Stereochemical vocabulary for structures that are chiral but not asymmetric: History, analysis, and proposal for a rational terminology.

PubMed

Gal, Joseph

2011-09-01

Asymmetric objects are necessarily chiral, but a structure may be chiral and not asymmetric if it possesses one or more proper rotation axes. Chiral but not asymmetric molecules are important in chemistry and its applications, but no suitable term exists for the designation of such structures, and their terminology in the literature is confused and chaotic. Dissymmetric has been redefined by some authors as "chiral but not asymmetric," in conflict both with Pasteur's definition of the term as "not superposable on its mirror image" (without other restrictions, i.e., chiral) and the understanding of the term in stereochemistry. Moreover, dissymmetric and asymmetric are frequently confused because of their similar forms. Furthermore, dissymmetric is widely used in many other definitions in chemistry, physics, and other disciplines. Thus, dissymmetric is unsuitable in the new definition of "chiral but not asymmetric," and a new term is needed. The adjective "symmanumorphous" is therefore proposed for "chiral but not asymmetric". "Sym" (from symmetry) indicates the presence of some symmetry in the structure, and "manu" (from "manus," Latin for hand, e.g., manual, manuscript) refers to its handedness. "Morphous," from the Greek "morphē," that is, form, is widely used, for example, anthropomorphous, enantiomorphous, etc. Symmanumorphous is convenient and euphonious and at 15 characters (same as enantiomorphous) is not unduly long. The nouns "a symmanumorph" (a structure that is chiral but not asymmetric) and "symmanumorphism" (the phenomenon of chirality without asymmetry) are also proposed. The new terminology is adaptable in other languages and would contribute to creating order out of linguistic chaos. Copyright © 2011 Wiley-Liss, Inc.

Can the chirality of the ISM be measured

NASA Technical Reports Server (NTRS)

Pendleton, Y.; Sandford, S. A.; Werner, Michael W.; Lauer, J.; Chang, Sherwood

1990-01-01

Many moderately complex carbon-based molecules of the type associated with biological systems can exist in one of two mirror-image forms (left-handed and right-handed), which can be distinguished on the basis of their influence on the state of polarization of a light beam. Both forms are possible in nature; yet in living organisms it is invariably the rule that one of these two species predominates. This gives rise to a net chirality. One possible explanation for the net chirality is that the early earth was somehow seeded from the ISM with an excess of chiral organic compounds which led to the development of life forms which are based on left-handed amino acids and right-handed sugars. Molecular spectroscopy of the interstellar medium (ISM) has revealed a complex variety of molecular species similar to those thought to have been available in the oceans and atmospheres of the earth at the time life formed. The detection of such molecules demonstrates the generality of the chemical processes occurring in both environments. If this generality extends to the processes which produce chirality, it may be possible to detect a net chirality in the ISM. This is of particular interest because determining whether or not net chirality exists elsewhere in the universe is an essential aspect of understanding how life developed on earth and how widely distributed it might be. Researchers report preliminary results of a feasibility study to determine whether or not a net chirality in the ISM can be measured. If laboratory results identify candidate chiral molecules that might exist in the ISM, the next step in this feasibility study will be to estimate the detectability of the chiral signature in astrophysical environments.

Chiral Sugars Drive Enantioenrichment in Prebiotic Amino Acid Synthesis.

PubMed

Wagner, Alexander J; Zubarev, Dmitry Yu; Aspuru-Guzik, Alán; Blackmond, Donna G

2017-04-26

Chiral pentose sugars mediate the enantioselective synthesis of amino acid precursors, with the magnitude of the chiral induction dictated by a subtle cooperativity between sugar hydroxyl groups. Ribose and lyxose give opposite chiral preferences, and theoretical calculations reveal the pseudoenantiomeric nature of transition state structures from the two sugars. Prebiotically plausible mixtures of natural d-sugars lead to enantioenrichment of natural l-amino acid precursors. Temporal monitoring and kinetic modeling of the reaction reveal an unusual dynamic kinetic resolution that shifts toward an enantioselective pathway over time, providing an amplification mechanism for the transfer of chiral information. This work adds to growing evidence for synergy in the etiology of the single chirality of the two most important classes of biological molecules, the sugars that make up DNA and RNA and the amino acids that form proteins.

Measuring the electromagnetic chirality of 2D arrays under normal illumination.

PubMed

Garcia-Santiago, X; Burger, S; Rockstuhl, C; Fernandez-Corbaton, I

2017-10-15

We present an electromagnetic chirality measure for 2D arrays of subwavelength periodicities under normal illumination. The calculation of the measure uses only the complex reflection and transmission coefficients from the array. The measure allows the ordering of arrays according to their electromagnetic chirality, which further allows a quantitative comparison of different design strategies. The measure is upper bounded, and the extreme properties of objects with high values of electromagnetic chirality make them useful in both near- and far-field applications. We analyze the consequences that different possible symmetries of the array have on its electromagnetic chirality. We use the measure to study four different arrays. The results indicate the suitability of helices for building arrays of high electromagnetic chirality, and the low effectiveness of a substrate for breaking the transverse mirror symmetry.

On the origin of biological chirality via natural beta-decay

NASA Technical Reports Server (NTRS)

Noyes, H. P.; Bonner, W. A.; Tomlin, J. A.

1977-01-01

An hypothesis to account for the chirality (handedness) of some biological molecules is given. Experimental evidence suggests that longitudinally polarized electrons having the chirality of terrestrial beta-decay electrons remove dextro-leucine from a racemic mixture. If, by a similar mechanism, the terrestrial environment provided more levo- than dextro-amino acids, that would account for the chirality now observed in organic molecules. An isotope of potassium has been proposed as the natural beta-emitter responsible for biomolecular chirality; however, Carbon 14 may be an even more plausible candidate. Ready availability of the carbon isotope in the terrestrial environment of 4.5 aeons ago, and the role of leucine in protein synthesis indicate that these two agents may have been chief factors in the evolution of biomolecular chirality. Suggestions for further research in this area are made.

Observation of chiral phonons.

PubMed

Zhu, Hanyu; Yi, Jun; Li, Ming-Yang; Xiao, Jun; Zhang, Lifa; Yang, Chih-Wen; Kaindl, Robert A; Li, Lain-Jong; Wang, Yuan; Zhang, Xiang

2018-02-02

Chirality reveals symmetry breaking of the fundamental interaction of elementary particles. In condensed matter, for example, the chirality of electrons governs many unconventional transport phenomena such as the quantum Hall effect. Here we show that phonons can exhibit intrinsic chirality in monolayer tungsten diselenide. The broken inversion symmetry of the lattice lifts the degeneracy of clockwise and counterclockwise phonon modes at the corners of the Brillouin zone. We identified the phonons by the intervalley transfer of holes through hole-phonon interactions during the indirect infrared absorption, and we confirmed their chirality by the infrared circular dichroism arising from pseudoangular momentum conservation. The chiral phonons are important for electron-phonon coupling in solids, phonon-driven topological states, and energy-efficient information processing. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Chiral Drug Analysis in Forensic Chemistry: An Overview.

PubMed

Ribeiro, Cláudia; Santos, Cristiana; Gonçalves, Valter; Ramos, Ana; Afonso, Carlos; Tiritan, Maria Elizabeth

2018-01-28

Many substances of forensic interest are chiral and available either as racemates or pure enantiomers. Application of chiral analysis in biological samples can be useful for the determination of legal or illicit drugs consumption or interpretation of unexpected toxicological effects. Chiral substances can also be found in environmental samples and revealed to be useful for determination of community drug usage (sewage epidemiology), identification of illicit drug manufacturing locations, illegal discharge of sewage and in environmental risk assessment. Thus, the purpose of this paper is to provide an overview of the application of chiral analysis in biological and environmental samples and their relevance in the forensic field. Most frequently analytical methods used to quantify the enantiomers are liquid and gas chromatography using both indirect, with enantiomerically pure derivatizing reagents, and direct methods recurring to chiral stationary phases.

Controlling Chirality of Entropic Crystals.

PubMed

Damasceno, Pablo F; Karas, Andrew S; Schultz, Benjamin A; Engel, Michael; Glotzer, Sharon C

2015-10-09

Colloidal crystal structures with complexity and diversity rivaling atomic and molecular crystals have been predicted and obtained for hard particles by entropy maximization. However, thus far homochiral colloidal crystals, which are candidates for photonic metamaterials, are absent. Using Monte Carlo simulations we show that chiral polyhedra exhibiting weak directional entropic forces self-assemble either an achiral crystal or a chiral crystal with limited control over the crystal handedness. Building blocks with stronger faceting exhibit higher selectivity and assemble a chiral crystal with handedness uniquely determined by the particle chirality. Tuning the strength of directional entropic forces by means of particle rounding or the use of depletants allows for reconfiguration between achiral and homochiral crystals. We rationalize our findings by quantifying the chirality strength of each particle, both from particle geometry and potential of mean force and torque diagrams.

Chiral resolution of spin angular momentum in linearly polarized and unpolarized light

PubMed Central

Hernández, R. J.; Mazzulla, A.; Provenzano, C.; Pagliusi, P.; Cipparrone, G.

2015-01-01

Linearly polarized (LP) and unpolarized (UP) light are racemic entities since they can be described as superposition of opposite circularly polarized (CP) components of equal amplitude. As a consequence they do not carry spin angular momentum. Chiral resolution of a racemate, i.e. separation of their chiral components, is usually performed via asymmetric interaction with a chiral entity. In this paper we provide an experimental evidence of the chiral resolution of linearly polarized and unpolarized Gaussian beams through the transfer of spin angular momentum to chiral microparticles. Due to the interplay between linear and angular momentum exchange, basic manipulation tasks, as trapping, spinning or orbiting of micro-objects, can be performed by light with zero helicity. The results might broaden the perspectives for development of miniaturized and cost-effective devices. PMID:26585284

Chiral Sugars Drive Enantioenrichment in Prebiotic Amino Acid Synthesis

PubMed Central

2017-01-01

Chiral pentose sugars mediate the enantioselective synthesis of amino acid precursors, with the magnitude of the chiral induction dictated by a subtle cooperativity between sugar hydroxyl groups. Ribose and lyxose give opposite chiral preferences, and theoretical calculations reveal the pseudoenantiomeric nature of transition state structures from the two sugars. Prebiotically plausible mixtures of natural d-sugars lead to enantioenrichment of natural l-amino acid precursors. Temporal monitoring and kinetic modeling of the reaction reveal an unusual dynamic kinetic resolution that shifts toward an enantioselective pathway over time, providing an amplification mechanism for the transfer of chiral information. This work adds to growing evidence for synergy in the etiology of the single chirality of the two most important classes of biological molecules, the sugars that make up DNA and RNA and the amino acids that form proteins. PMID:28470050

Mixing and demixing of binary mixtures of polar chiral active particles.

PubMed

Ai, Bao-Quan; Shao, Zhi-Gang; Zhong, Wei-Rong

2018-05-17

We study a binary mixture of polar chiral (counterclockwise or clockwise) active particles in a two-dimensional box with periodic boundary conditions. Besides the excluded volume interactions between particles, the particles are also subjected to the polar velocity alignment. From the extensive Brownian dynamics simulations, it is found that the particle configuration (mixing or demixing) is determined by the competition between the chirality difference and the polar velocity alignment. When the chirality difference competes with the polar velocity alignment, the clockwise particles aggregate in one cluster and the counterclockwise particles aggregate in the other cluster; thus, the particles are demixed and can be separated. However, when the chirality difference or the polar velocity alignment is dominant, the particles are mixed. Our findings could be used for the experimental pursuit of the separation of binary mixtures of chiral active particles.

Catalytic Enantioselective Olefin Metathesis in Natural Product Synthesis. Chiral Metal-Based Complexes that Deliver High Enantioselectivity and More

PubMed Central

Malcolmson, Steven J.; Meek, Simon J.; Zhugralin, Adil R.

2012-01-01

Chiral olefin metathesis catalysts enable chemists to access enantiomerically enriched small molecules with high efficiency; synthesis schemes involving such complexes can be substantially more concise than those that would involve enantiomerically pure substrates and achiral Mo alkylidenes or Ru-based carbenes. The scope of research towards design and development of chiral catalysts is not limited to discovery of complexes that are merely the chiral versions of the related achiral variants. A chiral olefin metathesis catalyst, in addition to furnishing products of high enantiomeric purity, can offer levels of efficiency, product selectivity and/or olefin stereoselectivity that are unavailable through the achiral variants. Such positive attributes of chiral catalysts (whether utilized in racemic or enantiomerically enriched form) should be considered as general, applicable to other classes of transformations. PMID:19967680

Catalysis of partial chiral symmetry restoration by Δ matter

NASA Astrophysics Data System (ADS)

Takeda, Yusuke; Kim, Youngman; Harada, Masayasu

2018-06-01

We study the phase structure of dense hadronic matter including Δ (1232 ) as well as N (939 ) based on the parity partner structure, where the baryons have their chiral partners with a certain amount of chiral invariant masses. We show that, in symmetric matter, Δ enters into matter in the density region of about one to four times normal nuclear matter density, ρB˜1 -4 ρ0 . The onset density of Δ matter depends on the chiral invariant mass of Δ ,mΔ 0 : As mΔ 0 increases, the onset density becomes bigger. The stable Δ -nucleon matter is realized for ρB≳1.5 ρ0 , i.e., the phase transition from nuclear matter to Δ -nucleon matter is of first order for small mΔ 0, and it is of second order for large mΔ 0. We find that, associated with the phase transition, the chiral condensate changes very rapidly; i.e., the chiral symmetry restoration is accelerated by Δ matter. As a result of the accelerations, there appear N*(1535 ) and Δ (1700 ) , which are the chiral partners to N (939 ) and Δ (1232 ) , in high-density matter, signaling the partial chiral symmetry restoration. Furthermore, we find that complete chiral symmetry restoration itself is delayed by Δ matter. We also calculate the effective masses, pressure, and symmetry energy to study how the transition to Δ matter affects such physical quantities. We observe that the physical quantities change drastically at the transition density.

Electric-field-induced assembly and propulsion of chiral colloidal clusters.

PubMed

Ma, Fuduo; Wang, Sijia; Wu, David T; Wu, Ning

2015-05-19

Chiral molecules with opposite handedness exhibit distinct physical, chemical, or biological properties. They pose challenges as well as opportunities in understanding the phase behavior of soft matter, designing enantioselective catalysts, and manufacturing single-handed pharmaceuticals. Microscopic particles, arranged in a chiral configuration, could also exhibit unusual optical, electric, or magnetic responses. Here we report a simple method to assemble achiral building blocks, i.e., the asymmetric colloidal dimers, into a family of chiral clusters. Under alternating current electric fields, two to four lying dimers associate closely with a central standing dimer and form both right- and left-handed clusters on a conducting substrate. The cluster configuration is primarily determined by the induced dipolar interactions between constituent dimers. Our theoretical model reveals that in-plane dipolar repulsion between petals in the cluster favors the achiral configuration, whereas out-of-plane attraction between the central dimer and surrounding petals favors a chiral arrangement. It is the competition between these two interactions that dictates the final configuration. The theoretical chirality phase diagram is found to be in excellent agreement with experimental observations. We further demonstrate that the broken symmetry in chiral clusters induces an unbalanced electrohydrodynamic flow surrounding them. As a result, they rotate in opposite directions according to their handedness. Both the assembly and propulsion mechanisms revealed here can be potentially applied to other types of asymmetric particles. Such kinds of chiral colloids will be useful for fabricating metamaterials, making model systems for both chiral molecules and active matter, or building propellers for microscale transport.

Computationally Aided Absolute Stereochemical Determination of Enantioenriched Amines.

PubMed

Zhang, Jun; Gholami, Hadi; Ding, Xinliang; Chun, Minji; Vasileiou, Chrysoula; Nehira, Tatsuo; Borhan, Babak

2017-03-17

A simple and efficient protocol for sensing the absolute stereochemistry and enantiomeric excess of chiral monoamines is reported. Preparation of the sample requires a single-step reaction of the 1,1'-(bromomethylene)dinaphthalene (BDN) with the chiral amine. Analysis of the exciton coupled circular dichroism generated from the BDN-derivatized chiral amine sample, along with comparison to conformational analysis performed computationally, yields the absolute stereochemistry of the parent chiral monoamine.

Photoremovable chiral auxiliary.

PubMed

Kammath, Viju Balachandran; Sebej, Peter; Slanina, Tomáš; Kříž, Zdeněk; Klán, Petr

2012-03-01

A new concept of a photoremovable chiral auxiliary (PCA), based on the chiral benzoin chromophore, is introduced. This moiety can control the asymmetric formation of a Diels-Alder adduct, and then be removed in a subsequent photochemical step in high chemical and quantum yields. Selective formation of the products at up to 96% ee was observed in the presence of a Lewis acid catalyst in the case of a 2-methoxybenzoinyl chiral auxiliary.

Chiral anomaly, Berry phase, and chiral kinetic theory from worldlines in quantum field theory

NASA Astrophysics Data System (ADS)

Mueller, Niklas; Venugopalan, Raju

2018-03-01

In previous work, we outlined a worldline framework that can be used for systematic computations of the chiral magnetic effect (CME) in ultrarelativistic heavy-ion collisions. Towards this end, we first expressed the real part of the fermion determinant in the QCD effective action as a supersymmetric worldline action of spinning, colored, Grassmanian point particles in background gauge fields, with equations of motion that are covariant generalizations of the Bargmann-Michel-Telegdi and Wong equations. The chiral anomaly, in contrast, arises from the phase of the fermion determinant. Remarkably, the latter too can be expressed as a point particle worldline path integral, which can be employed to derive the anomalous axial vector current. We will show here how Berry's phase can be obtained in a consistent nonrelativistic adiabatic limit of the real part of the fermion determinant. Our work provides a general first principles demonstration that the topology of Berry's phase is distinct from that of the chiral anomaly confirming prior arguments by Fujikawa in specific contexts. This suggests that chiral kinetic treatments of the CME in heavy-ion collisions that include Berry's phase alone are incomplete. We outline the elements of a worldline covariant relativistic chiral kinetic theory that captures the physics of how the chiral current is modified by many-body scattering and topological fluctuations.

Molecular dynamics simulation of a nanofluidic energy absorption system: effects of the chiral vector of carbon nanotubes.

PubMed

Ganjiani, Sayed Hossein; Hossein Nezhad, Alireza

2018-02-14

A Nanofluidic Energy Absorption System (NEAS) is a novel nanofluidic system with a small volume and weight. In this system, the input mechanical energy is converted to surface tension energy during liquid infiltration in the nanotube. The NEAS is made of a mixture of nanoporous material particles in a functional liquid. In this work, the effects of the chiral vector of a carbon nanotube (CNT) on the performance characteristics of the NEAS are investigated by using molecular dynamics simulation. For this purpose, six CNTs with different diameters for each type of armchair, zigzag and chiral, and several chiral CNTs with different chiral vectors (different values of indices (m,n)) are selected and studied. The results show that in the chiral CNTs, the contact angle shows the hydrophobicity of the CNT, and infiltration pressure is reduced by increasing the values of m and n (increasing the CNT diameter). Contact angle and infiltration pressure are decreased by almost 1.4% and 9% at all diameters, as the type of CNT is changed from chiral to zigzag and then to armchair. Absorbed energy density and efficiency are also decreased by increasing m and n and by changing the type of CNT from chiral to zigzag and then to armchair.

Quantitative Surface Chirality Detection with Sum Frequency Generation Vibrational Spectroscopy: Twin Polarization Angle Approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wei, Feng; Xu, Yanyan; Guo, Yuan

2009-12-27

Here we report a novel twin polarization angle (TPA) approach in the quantitative chirality detection with the surface sum-frequency generation vibrational spectroscopy (SFG-VS). Generally, the achiral contribution dominates the surface SFG-VS signal, and the pure chiral signal is usually two or three orders of magnitude smaller. Therefore, it has been difficult to make quantitative detection and analysis of the chiral contributions to the surface SFG- VS signal. In the TPA method, by varying together the polarization angles of the incoming visible light and the sum frequency signal at fixed s or p polarization of the incoming infrared beam, the polarizationmore » dependent SFG signal can give not only direct signature of the chiral contribution in the total SFG-VS signal, but also the accurate measurement of the chiral and achiral components in the surface SFG signal. The general description of the TPA method is presented and the experiment test of the TPA approach is also presented for the SFG-VS from the S- and R-limonene chiral liquid surfaces. The most accurate degree of chiral excess values thus obtained for the 2878 cm⁻¹ spectral peak of the S- and R-limonene liquid surfaces are (23.7±0.4)% and ({25.4±1.3)%, respectively.« less

Relating quark confinement and chiral symmetry breaking in QCD

NASA Astrophysics Data System (ADS)

Suganuma, Hideo; Doi, Takahiro M.; Redlich, Krzysztof; Sasaki, Chihiro

2017-12-01

We study the relation between quark confinement and chiral symmetry breaking in QCD. Using lattice QCD formalism, we analytically express the various ‘confinement indicators’, such as the Polyakov loop, its fluctuations, the Wilson loop, the inter-quark potential and the string tension, in terms of the Dirac eigenmodes. In the Dirac spectral representation, there appears a power of the Dirac eigenvalue {λ }n such as {λ }n{Nt-1}, which behaves as a reduction factor for small {λ }n. Consequently, since this reduction factor cannot be cancelled, the low-lying Dirac eigenmodes give negligibly small contribution to the confinement quantities, while they are essential for chiral symmetry breaking. These relations indicate that there is no direct one-to-one correspondence between confinement and chiral symmetry breaking in QCD. In other words, there is some independence of quark confinement from chiral symmetry breaking, which can generally lead to different transition temperatures/densities for deconfinement and chiral restoration. We also investigate the Polyakov loop in terms of the eigenmodes of the Wilson, the clover and the domain-wall fermion kernels, and find similar results. The independence of quark confinement from chiral symmetry breaking seems to be natural, because confinement is realized independently of quark masses and heavy quarks are also confined even without the chiral symmetry.

Zwitterionic chiral stationary phases based on cinchona and chiral sulfonic acids for the direct stereoselective separation of amino acids and other amphoteric compounds.

PubMed

Zhang, Tong; Holder, Emilie; Franco, Pilar; Lindner, Wolfgang

2014-06-01

An extensive series of free amino acids and analogs were directly resolved into enantiomers (and stereoisomers where appropriate) by HPLC on zwitterionic chiral stationary phases (Chiralpak ZWIX(+) and Chiralpak ZWIX(-)). The interaction and chiral recognition mechanisms were based on the synergistic double ion-paring process between the analyte and the chiral selectors. The chiral separation and elution order were found to be predictable for primary α-amino acids with apolar aliphatic side chains. A systematic investigation was undertaken to gain an insight into the influence of the structural features on the enantiorecognition. The presence of polar and/or aromatic groups in the analyte structure is believed to tune the double ion-paring equilibrium by the involvement of the secondary interaction forces such as hydrogen bonding, Van der Waals forces and π-π stacking in concert with steric parameters. The ZWIX chiral columns were able to separate enantiomers and stereoisomers of various amphoteric compounds with no need for precolumn derivatization. Column switching between ZWIX(+) and ZWIX(-) is believed to be an instrumental tool to reverse or control the enantiomers elution order, due to the complementarity of the applied chiral selectors. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chiral amplification and sensing of chirality with lyotropic chromonic liquid crystals

NASA Astrophysics Data System (ADS)

Srinivasarao, Mohan; Park, Jung Ok; Fu, Jinxin; Nayani, Karthik; Chang, Rui

Due to the anisotropic elastic properties of lyotropic chromonic liquid crystals (LCLCs), a spontaneously twisted chiral structure has been reported in the achiral LCLCs system under cylindrical confinement. It is found that the handedness of chirality could be biased with a minute amount of a chiral additive. The entire system becomes ``homochiral'' and takes on the handedness of the additive. When 1% by weight of L-glutamic acid was added to LCLCs in a cylinder, the LCLC sbecomes homochiral and possesses giant optical rotation. We explore the mechanism for this based on the ``sergeants-and-soldiers'' and the ``majority-rule'' principles known for organic molecular systems.

Staggered chiral perturbation theory in the two-flavor case

DOE Office of Scientific and Technical Information (OSTI.GOV)

Du Xining

2010-07-01

I study two-flavor staggered chiral perturbation theory in the light pseudoscalar sector. The pion mass and decay constant are calculated through next-to-leading order in the partially-quenched case. In the limit where the strange quark mass is large compared to the light quark masses and the taste splittings, I show that the SU(2) staggered chiral theory emerges from the SU(3) staggered chiral theory, as expected. Explicit relations between SU(2) and SU(3) low energy constants and taste-violating parameters are given. The results are useful for SU(2) chiral fits to asqtad data and allow one to incorporate effects from varying strange quark masses.

Chiral plasmonics

PubMed Central

Hentschel, Mario; Schäferling, Martin; Duan, Xiaoyang; Giessen, Harald; Liu, Na

2017-01-01

We present a comprehensive overview of chirality and its optical manifestation in plasmonic nanosystems and nanostructures. We discuss top-down fabricated structures that range from solid metallic nanostructures to groupings of metallic nanoparticles arranged in three dimensions. We also present the large variety of bottom-up synthesized structures. Using DNA, peptides, or other scaffolds, complex nanoparticle arrangements of up to hundreds of individual nanoparticles have been realized. Beyond this static picture, we also give an overview of recent demonstrations of active chiral plasmonic systems, where the chiral optical response can be controlled by an external stimulus. We discuss the prospect of using the unique properties of complex chiral plasmonic systems for enantiomeric sensing schemes. PMID:28560336

Chiral dynamics with (non)strange quarks

NASA Astrophysics Data System (ADS)

Kubis, Bastian; Meißner, Ulf-G.

2017-01-01

We review the results and achievements of the project B.3. Topics addressed include pion photoproduction off the proton and off deuterium, three-flavor chiral perturbation theory studies, chiral symmetry tests in Goldstone boson decays, the development of unitarized chiral perturbation theory to next-to-leading order, the two-pole structure of the Λ(1405), the dynamical generation of the lowest S11 resonances, the theory of hadronic atoms and its application to various systems, precision studies in light-meson decays based on dispersion theory, the Roy-Steiner analysis of pion-nucleon scattering, a high-precision extraction of the elusive pion-nucleon σ-term, and aspects of chiral dynamics in few-nucleon systems.

METHODS DEVELOPMENT FOR THE ANALYSIS OF CHIRAL PESTICIDES

EPA Science Inventory

Chiral compounds exist as a pair of nonsuperimposable mirror images called enantiomers. Enantiomers have identical physical-chemical properties, but their interactions with other chiral molecules, toxicity, biodegradation, and fate are often different. Many pharmaceutical com...

Contractile and chiral activities codetermine the helicity of swimming droplet trajectories

NASA Astrophysics Data System (ADS)

Tjhung, Elsen; Cates, Michael E.; Marenduzzo, Davide

2017-05-01

Active fluids are a class of nonequilibrium systems where energy is injected into the system continuously by the constituent particles themselves. Many examples, such as bacterial suspensions and actomyosin networks, are intrinsically chiral at a local scale, so that their activity involves torque dipoles alongside the force dipoles usually considered. Although many aspects of active fluids have been studied, the effects of chirality on them are much less known. Here, we study by computer simulation the dynamics of an unstructured droplet of chiral active fluid in three dimensions. Our model considers only the simplest possible combination of chiral and achiral active stresses, yet this leads to an unprecedented range of complex motilities, including oscillatory swimming, helical swimming, and run-and-tumble motion. Strikingly, whereas the chirality of helical swimming is the same as the microscopic chirality of torque dipoles in one regime, the two are opposite in another. Some of the features of these motility modes resemble those of some single-celled protozoa, suggesting that underlying mechanisms may be shared by some biological systems and synthetic active droplets.

Bioinspired Mesoporous Chiral Nematic Graphitic Carbon Nitride Photocatalysts modulated by Polarized Light.

PubMed

Lin, Wensheng; Hong, Wei; Sun, Lu; Yu, Di; Yu, Dingshan; Chen, Xudong

2018-01-10

Endowing materials with chirality and exploring the responses of the material under circularly polarized light (CPL) can enable further insight into the physical and chemical properties of the semiconductors to be gained, thus expanding on optoelectronic applications. Herein a bioinspired mesoporous chiral nematic graphitic carbon nitride (g-C 3 N 4 ) for efficient hydrogen evolution with polarized light modulation based on chiral nematic cellulose nanocrystal films prepared through silica templating is described. The mesoporous nematic chiral g-C 3 N 4 exhibits an ultrahigh hydrogen evolution rate of 219.9 μmol h -1 (for 20 mg catalyst), corresponding to a high enhancement factor of 55 when compared to the bulk g-C 3 N 4 under λ>420 nm irradiation. Furthermore, the chiral g-C 3 N 4 material exhibits unique photocatalytic activity modulated by CPL within the absorption region. This CPL-assisted photocatalytic regulation strategy holds great promise for a wide range of applications including optical devices, asymmetric photocatalysis, and chiral recognition/separation. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Controllable rotational inversion in nanostructures with dual chirality.

PubMed

Dai, Lu; Zhu, Ka-Di; Shen, Wenzhong; Huang, Xiaojiang; Zhang, Li; Goriely, Alain

2018-04-05

Chiral structures play an important role in natural sciences due to their great variety and potential applications. A perversion connecting two helices with opposite chirality creates a dual-chirality helical structure. In this paper, we develop a novel model to explore quantitatively the mechanical behavior of normal, binormal and transversely isotropic helical structures with dual chirality and apply these ideas to known nanostructures. It is found that both direction and amplitude of rotation can be finely controlled by designing the cross-sectional shape. A peculiar rotational inversion of overwinding followed by unwinding, observed in some gourd and cucumber tendril perversions, not only exists in transversely isotropic dual-chirality helical nanobelts, but also in the binormal/normal ones when the cross-sectional aspect ratio is close to 1. Beyond this rotational inversion region, the binormal and normal dual-chirality helical nanobelts exhibit a fixed directional rotation of unwinding and overwinding, respectively. Moreover, in the binormal case, the rotation of these helical nanobelts is nearly linear, which is promising as a possible design for linear-to-rotary motion converters. The present work suggests new designs for nanoscale devices.

Surface-anchored poly(acryloyl-L(D)-valine) with enhanced chirality-selective effect on cellular uptake of gold nanoparticles

PubMed Central

Deng, Jun; Wu, Sai; Yao, Mengyun; Gao, Changyou

2016-01-01

Chirality is one of the ubiquitous phenomena in biological systems. The left handed (L-) amino acids and right handed (D-) sugars are normally found in proteins, and in RNAs and DNAs, respectively. The effect of chiral surfaces at the nanoscale on cellular uptake has, however, not been explored. This study reveals for the first time the molecular chirality on gold nanoparticles (AuNPs) functions as a direct regulator for cellular uptake. Monolayers of 2-mercaptoacetyl-L(D)-valine (L(D)-MAV) and poly(acryloyl-L(D)-valine (L(D)-PAV) chiral molecules were formed on AuNPs surface, respectively. The internalized amount of PAV-AuNPs was several times larger than that of MAV-AuNPs by A549 and HepG2 cells, regardless of the chirality difference. However, the D-PAV-AuNPs were internalized with significantly larger amount than the L-PAV-AuNPs. This chirality-dependent uptake effect is likely attributed to the preferable interaction between the L-phospholipid-based cell membrane and the D-enantiomers. PMID:27531648

Transmission of chirality through space and across length scales

NASA Astrophysics Data System (ADS)

Morrow, Sarah M.; Bissette, Andrew J.; Fletcher, Stephen P.

2017-05-01

Chirality is a fundamental property and vital to chemistry, biology, physics and materials science. The ability to use asymmetry to operate molecular-level machines or macroscopically functional devices, or to give novel properties to materials, may address key challenges at the heart of the physical sciences. However, how chirality at one length scale can be translated to asymmetry at a different scale is largely not well understood. In this Review, we discuss systems where chiral information is translated across length scales and through space. A variety of synthetic systems involve the transmission of chiral information between the molecular-, meso- and macroscales. We show how fundamental stereochemical principles may be used to design and understand nanoscale chiral phenomena and highlight important recent advances relevant to nanotechnology. The survey reveals that while the study of stereochemistry on the nanoscale is a rich and dynamic area, our understanding of how to control and harness it and dial-up specific properties is still in its infancy. The long-term goal of controlling nanoscale chirality promises to be an exciting journey, revealing insight into biological mechanisms and providing new technologies based on dynamic physical properties.

Illuminating the chirality of Weyl fermions

NASA Astrophysics Data System (ADS)

Ma, Qiong; Xu, Su-Yang; Chan, Ching-Kit; Zhang, Cheng-Long; Chang, Guoqing; Lin, Hsin; Jia, Shuang; Lee, Patrick; Gedik, Nuh; Jarillo-Herrero, Pablo

In particle physics, Weyl fermions (WF) are elementary particles that travel at the speed of light and have a definite chirality. In condensed matter, it has been recently realized that WFs can arise as magnetic monopoles in the momentum space of a novel topological metal, the Weyl semimetal (WSM). Their chirality, given by the sign of the monopole charge, is the defining property of a WSM, since it directly serves as the topological number and gives rise to exotic properties such as Fermi arcs and the chiral anomaly. Moreover, the two chiralities, analogous to the two valleys in 2D materials, lead to a new degree of freedom in a 3D crystal, suggesting novel pathways to store and carry information. By shining circularly polarized light on the WSM TaAs, we illuminate the chirality of the WFs and achieve an electrical current that is highly controllable based on the WFs' chirality. Our results open up a wide range of new possibilities for experimentally studying and controlling the WFs and their associated quantum anomalies by optical and electrical means, which suggest the exciting prospect of ``Weyltronics''.

Surface-anchored poly(acryloyl-L(D)-valine) with enhanced chirality-selective effect on cellular uptake of gold nanoparticles

NASA Astrophysics Data System (ADS)

Deng, Jun; Wu, Sai; Yao, Mengyun; Gao, Changyou

2016-08-01

Chirality is one of the ubiquitous phenomena in biological systems. The left handed (L-) amino acids and right handed (D-) sugars are normally found in proteins, and in RNAs and DNAs, respectively. The effect of chiral surfaces at the nanoscale on cellular uptake has, however, not been explored. This study reveals for the first time the molecular chirality on gold nanoparticles (AuNPs) functions as a direct regulator for cellular uptake. Monolayers of 2-mercaptoacetyl-L(D)-valine (L(D)-MAV) and poly(acryloyl-L(D)-valine (L(D)-PAV) chiral molecules were formed on AuNPs surface, respectively. The internalized amount of PAV-AuNPs was several times larger than that of MAV-AuNPs by A549 and HepG2 cells, regardless of the chirality difference. However, the D-PAV-AuNPs were internalized with significantly larger amount than the L-PAV-AuNPs. This chirality-dependent uptake effect is likely attributed to the preferable interaction between the L-phospholipid-based cell membrane and the D-enantiomers.

Surface-anchored poly(acryloyl-L(D)-valine) with enhanced chirality-selective effect on cellular uptake of gold nanoparticles.

PubMed

Deng, Jun; Wu, Sai; Yao, Mengyun; Gao, Changyou

2016-08-17

Chirality is one of the ubiquitous phenomena in biological systems. The left handed (L-) amino acids and right handed (D-) sugars are normally found in proteins, and in RNAs and DNAs, respectively. The effect of chiral surfaces at the nanoscale on cellular uptake has, however, not been explored. This study reveals for the first time the molecular chirality on gold nanoparticles (AuNPs) functions as a direct regulator for cellular uptake. Monolayers of 2-mercaptoacetyl-L(D)-valine (L(D)-MAV) and poly(acryloyl-L(D)-valine (L(D)-PAV) chiral molecules were formed on AuNPs surface, respectively. The internalized amount of PAV-AuNPs was several times larger than that of MAV-AuNPs by A549 and HepG2 cells, regardless of the chirality difference. However, the D-PAV-AuNPs were internalized with significantly larger amount than the L-PAV-AuNPs. This chirality-dependent uptake effect is likely attributed to the preferable interaction between the L-phospholipid-based cell membrane and the D-enantiomers.

Chiral transcription in self-assembled tetrahedral Eu 4L 6 chiral cages displaying sizable circularly polarized luminescence

DOE PAGES

Yeung, Chi -Tung; Yim, King -Him; Wong, Ho -Yin; ...

2017-10-24

Predictable stereoselective formation of supramolecular assembly is generally believed to be an important but complicated process. Here, we show that point chirality of a ligand decisively influences its supramolecular assembly behavior. We designed three closely related chiral ligands with different point chiralities, and observe their self-assembly into europium (Eu) tetrametallic tetrahedral cages. One ligand exhibits a highly diastereoselective assembly into homochiral (either ΔΔΔΔ or ΛΛΛΛ) Eu tetrahedral cages whereas the two other ligands, with two different approaches of loosened point chirality, lead to a significant breakdown of the diastereoselectivity to generate a mixture of (ΔΔΔΔ and ΛΛΛΛ) isomers. The cagesmore » are highly emissive (luminescence quantum yields of 16(1) to 18(1)%) and exhibit impressive circularly polarized luminescence properties (|g lum |: up to 0.16). With in-depth studies, we present an example that correlates the nonlinear enhancement of the chiroptical response to the nonlinearity dependence on point chirality.« less

CHIRAL PESTICIDES: OCCURRENCE AND SIGNIFICANCE

EPA Science Inventory

Like amino acids, certain pesticides exist in "left-handed" and "right-handed" (chiral) forms. Commercially available chiral pesticides are produced as racemic mixtures in which the ratio of the two forms (or enantiomers) is 1:1. Enantiomers have the same ...

Chiral Chlordane Components in Environmental Matrices

EPA Science Inventory

Chlordane, a persistent, bioaccumulative and toxic organochlorine pesticide, has been studied for many years. Since the advent of chiral analysis for environmental samples, over 2,400 measurements have been made of various chiral chlordane components. Chlordane enantiomer fractio...

ENZYME DEGRADATION OF CHIRAL ORGANIC PHOSPHORUS INSECTICIDES

EPA Science Inventory

Chiral organic phosphorus pesticides (OPs) are expected to be biologically degraded enantioselectively by endogenous enzymes. Various chiral Ops were treated with the enzyme phosphotriesterase (PTE) obtained from partially purified extracts of Escherichia coli strain DH-5- carryi...

Diastereoselective synthesis of chiral 1,3-cyclohexadienals

PubMed Central

de la Granja, Ángela P.; Capitán, M. Carmen; Moro, R. F.; Marcos, Isidro S.; Garrido, Narciso M.; Sanz, Francisca; Calle, Emilio

2018-01-01

A novel approach to the production of chiral 1,3-cyclohexadienals has been developed. The organocatalysed asymmetric reaction of different β-disubstituted-α,β-unsaturated aldehydes with a chiral α,β-unsaturated aldehyde in the presence of a Jørgensen-Hayashi organocatalyst provides easy and stereocontrolled access to the cyclohexadienal backbone. This method allows for the synthesis of potential photoprotective chiral 1,3-cyclohexadienals and extra extended conjugation compounds in a simple manner. PMID:29438416

Deracemization of bilirubin as the marker of the chirality of micellar aggregates.

PubMed

Sorrenti, Alessandro; Altieri, Barbara; Ceccacci, Francesca; Di Profio, Pietro; Germani, Raimondo; Giansanti, Luisa; Savelli, Gianfranco; Mancini, Giovanna

2012-01-01

The deracemization of bilirubin in micellar aggregates of structurally correlated chiral surfactants was studied by circular dichroism experiments and exploited as the marker of the expression of chirality of the aggregates. The obtained results suggest that the hydrophobic interactions control the transfer of chirality from the monomers to the aggregates, and that different regions of the same aggregate might feature opposite enantiorecognition capabilities. Copyright © 2011 Wiley-Liss, Inc.

Diastereoselective synthesis of chiral 1,3-cyclohexadienals.

PubMed

Urosa, Aitor; Tobal, Ignacio E; de la Granja, Ángela P; Capitán, M Carmen; Moro, R F; Marcos, Isidro S; Garrido, Narciso M; Sanz, Francisca; Calle, Emilio; Díez, David

2018-01-01

A novel approach to the production of chiral 1,3-cyclohexadienals has been developed. The organocatalysed asymmetric reaction of different β-disubstituted-α,β-unsaturated aldehydes with a chiral α,β-unsaturated aldehyde in the presence of a Jørgensen-Hayashi organocatalyst provides easy and stereocontrolled access to the cyclohexadienal backbone. This method allows for the synthesis of potential photoprotective chiral 1,3-cyclohexadienals and extra extended conjugation compounds in a simple manner.

Confinement-induced liquid crystalline transitions in amyloid fibril cholesteric tactoids

NASA Astrophysics Data System (ADS)

Nyström, Gustav; Arcari, Mario; Mezzenga, Raffaele

2018-04-01

Chirality is ubiquitous in nature and plays crucial roles in biology, medicine, physics and materials science. Understanding and controlling chirality is therefore an important research challenge with broad implications. Unlike other chiral colloids, such as nanocellulose or filamentous viruses, amyloid fibrils form nematic phases but appear to miss their twisted form, the cholesteric or chiral nematic phases, despite a well-defined chirality at the single fibril level. Here we report the discovery of cholesteric phases in amyloids, using β-lactoglobulin fibrils shortened by shear stresses. The physical behaviour of these new cholesteric materials exhibits unprecedented structural complexity, with confinement-driven ordering transitions between at least three types of nematic and cholesteric tactoids. We use energy functional theory to rationalize these results and observe a chirality inversion from the left-handed amyloids to right-handed cholesteric droplets. These findings deepen our understanding of cholesteric phases, advancing their use in soft nanotechnology, nanomaterial templating and self-assembly.

Inducing Axial Chirality in a Supramolecular Catalyst.

PubMed

Wenz, Katharina Marie; Leonhardt-Lutterbeck, Günter; Breit, Bernhard

2018-03-06

A new type of ligand, which is able to form axially chiral, supramolecular complexes was designed using DFT calculations. Two chiral monomers, each featuring a covalently bound chiral auxiliary, form a bidentate phosphine ligand with a twisted, hydrogen-bonded backbone upon coordination to a transition metal center which results in two diastereomeric, tropos complexes. The ratio of the diastereomers in solution is very temperature- and solvent-dependent. Rhodium and platinum complexes were analyzed through a combination of NMR studies, ESI-MS measurements, as well as UV-VIS and circular dichroism spectroscopy. The chiral self-organized ligands were evaluated in the rhodium-catalyzed asymmetric hydrogenation of α-dehydrogenated amino acids and resulted in good conversion and high enantioselectivity. This research opens the way for new ligand designs based on stereocontrol of supramolecular assemblies through stereodirecting chiral centers. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Switchable Chiral Selection of Aspartic Acids by Dynamic States of Brushite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Wenge; Pan, Haihua; Zhang, Zhisen

Here, we show the chiral recognition and separation of aspartic acid (Asp) enantiomers by achiral brushite due to the asymmetries of their dynamical steps in its nonequilibrium states. Growing brushite has a higher adsorption affinity to d-Asp, while l-Asp is predominant on the dissolving brushite surface. Microstructural characterization reveals that chiral selection is mainly attributed to brushite [101] steps, which exhibit two different configurations during crystal growth and dissolution, respectively, with each preferring a distinct enantiomer due to this asymmetry. Because these transition step configurations have different stabilities, they subsequently result in asymmetric adsorption. Furthermore, by varying free energy barriersmore » through solution thermodynamic driving force (i.e., supersaturation), the dominant nonequilibrium intermediate states can be switched and chiral selection regulated. This finding highlights that the dynamic steps can be vital for chiral selection, which may provide a potential pathway for chirality generation through the dynamic nature.« less

Switchable Chiral Selection of Aspartic Acids by Dynamic States of Brushite

DOE PAGES

Jiang, Wenge; Pan, Haihua; Zhang, Zhisen; ...

2017-06-15

Here, we show the chiral recognition and separation of aspartic acid (Asp) enantiomers by achiral brushite due to the asymmetries of their dynamical steps in its nonequilibrium states. Growing brushite has a higher adsorption affinity to d-Asp, while l-Asp is predominant on the dissolving brushite surface. Microstructural characterization reveals that chiral selection is mainly attributed to brushite [101] steps, which exhibit two different configurations during crystal growth and dissolution, respectively, with each preferring a distinct enantiomer due to this asymmetry. Because these transition step configurations have different stabilities, they subsequently result in asymmetric adsorption. Furthermore, by varying free energy barriersmore » through solution thermodynamic driving force (i.e., supersaturation), the dominant nonequilibrium intermediate states can be switched and chiral selection regulated. This finding highlights that the dynamic steps can be vital for chiral selection, which may provide a potential pathway for chirality generation through the dynamic nature.« less

Exotic meson decays in the environment with chiral imbalance

NASA Astrophysics Data System (ADS)

Andrianov, A. A.; Andrianov, V. A.; Espriu, D.; Iakubovich, A. V.; Putilova, A. E.

2017-10-01

An emergence of Local Parity Breaking (LPB) in central heavy-ion collisions (HIC) at high energies is discussed. LPB in the fireball can be produced by a difference between the number densities of right- and left-handed chiral fermions (Chiral Imbalance) which is implemented by a chiral (axial) chemical potential. The effective meson lagrangian induced by QCD is extended to the medium with Chiral Imbalance and the properties of light scalar and pseudoscalar mesons (π, α0) are analyzed. It is shown that exotic decays of scalar mesons arise as a result of mixing of π and α0 vacuum states in the presence of chiral imbalance. The pion electromagnetic formfactor obtains an unusual parity-odd supplement which generates a photon polarization asymmetry in pion polarizability. We hope that the above pointed indications of LPB can be identified in experiments on LHC, RHIC, CBM FAIR and NICA accelerators.

Chiral optical response of planar and symmetric nanotrimers enabled by heteromaterial selection.

PubMed

Banzer, Peter; Woźniak, Paweł; Mick, Uwe; De Leon, Israel; Boyd, Robert W

2016-10-13

Chirality is an intriguing property of certain molecules, materials or artificial nanostructures, which allows them to interact with the spin angular momentum of the impinging light field. Due to their chiral geometry, they can distinguish between left- and right-hand circular polarization states or convert them into each other. Here we introduce an approach towards optical chirality, which is observed in individual two-dimensional and geometrically mirror-symmetric nanostructures. In this scheme, the chiral optical response is induced by the chosen heterogeneous material composition of a particle assembly and the corresponding resonance behaviour of the constituents it is built from, which breaks the symmetry of the system. As a proof of principle, we investigate such a structure composed of individual silicon and gold nanoparticles both experimentally, as well as numerically. Our proposed concept constitutes an approach for designing two-dimensional chiral media tailored at the nanoscale, allowing for high tunability of their optical response.

Chiral liquid crystal colloids

NASA Astrophysics Data System (ADS)

Yuan, Ye; Martinez, Angel; Senyuk, Bohdan; Tasinkevych, Mykola; Smalyukh, Ivan I.

2018-01-01

Colloidal particles disturb the alignment of rod-like molecules of liquid crystals, giving rise to long-range interactions that minimize the free energy of distorted regions. Particle shape and topology are known to guide this self-assembly process. However, how chirality of colloidal inclusions affects these long-range interactions is unclear. Here we study the effects of distortions caused by chiral springs and helices on the colloidal self-organization in a nematic liquid crystal using laser tweezers, particle tracking and optical imaging. We show that chirality of colloidal particles interacts with the nematic elasticity to predefine chiral or racemic colloidal superstructures in nematic colloids. These findings are consistent with numerical modelling based on the minimization of Landau-de Gennes free energy. Our study uncovers the role of chirality in defining the mesoscopic order of liquid crystal colloids, suggesting that this feature may be a potential tool to modulate the global orientated self-organization of these systems.

Dynamic Covalent Chemistry within Biphenyl Scaffolds: Reversible Covalent Bonding, Control of Selectivity, and Chirality Sensing with a Single System.

PubMed

Ni, Cailing; Zha, Daijun; Ye, Hebo; Hai, Yu; Zhou, Yuntao; Anslyn, Eric V; You, Lei

2018-01-26

Axial chirality is a prevalent and important phenomenon in chemistry. Herein we report a combination of dynamic covalent chemistry and axial chirality for the development of a versatile platform for the binding and chirality sensing of multiple classes of mononucleophiles. An equilibrium between an open aldehyde and its cyclic hemiaminal within biphenyl derivatives enabled the dynamic incorporation of a broad range of alcohols, thiols, primary amines, and secondary amines with high efficiency. Selectivity toward different classes of nucleophiles was also achieved by regulating the distinct reactivity of the system with external stimuli. Through induced helicity as a result of central-to-axial chirality transfer, the handedness and ee values of chiral monoalcohol and monoamine analytes were reported by circular dichroism. The strategies introduced herein should find application in many contexts, including assembly, sensing, and labeling. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cosmic chirality both true and false.

PubMed

Barron, Laurence D

2012-12-01

The discrete symmetries of parity P, time reversal T, and charge conjugation C may be used to characterize the properties of chiral systems. It is well known that parity violation infiltrates into ordinary matter via an interaction between the nucleons and electrons, mediated by the Z(0) particle, that lifts the degeneracy of the mirror-image enantiomers of a chiral molecule. Being odd under P but even under T, this P-violating interaction exhibits true chirality and so may induce absolute enantioselection under all circumstances. It has been suggested that CP violation may also infiltrate into ordinary matter via a P-odd, T-odd interaction mediated by the (as yet undetected) axion. This CP-violating interaction exhibits false chirality and so may induce absolute enantioselection in processes far from equilibrium. Both true and false cosmic chirality should be considered together as possible sources of homochirality in the molecules of life. Copyright © 2012 Wiley Periodicals, Inc.

Patterns and partners for chiral symmetry restoration

NASA Astrophysics Data System (ADS)

Gómez Nicola, A.; Ruiz de Elvira, J.

2018-04-01

We present and analyze a new set of Ward Identities which shed light on the distinction between different patterns of chiral symmetry restoration in QCD, namely O (4 ) vs O (4 )×U (1 )A. The degeneracy of chiral partners for all scalar and pseudoscalar meson nonet members is studied through their corresponding correlators. Around chiral symmetry degeneration of O (4 ) partners, our analysis predicts that U (1 )A partners are also degenerated. Our analysis also leads to I =1 /2 scalar-pseudoscalar partner degeneration at exact chiral restoration and supports ideal mixing between the η - η' and the f0(500 )- f0(980 ) mesons at O (4 )×U (1 )A restoration, with a possible range where the pseudoscalar mixing vanishes if the two transitions are well separated. We test our results with lattice data and provide further relevant observables regarding chiral and U (1 )A restoration for future lattice and model analyses.

Thermodynamic properties of the S =1 /2 twisted triangular spin tube

NASA Astrophysics Data System (ADS)

Ito, Takuya; Iino, Chihiro; Shibata, Naokazu

2018-05-01

Thermodynamic properties of the twisted three-leg spin tube under magnetic field are studied by the finite-T density-matrix renormalization group method. The specific heat, spin, and chiral susceptibilities of the infinite system are calculated for both the original and its low-energy effective models. The obtained results show that the presence of the chirality is observed as a clear peak in the specific heat at low temperature and the contribution of the chirality dominates the low-temperature part of the specific heat as the exchange coupling along the spin tube decreases. The peak structures in the specific heat, spin, and chiral susceptibilities are strongly modified near the quantum phase transition where the critical behaviors of the spin and chirality correlations change. These results confirm that the chirality plays a major role in characteristic low-energy behaviors of the frustrated spin systems.

Centre vortex removal restores chiral symmetry

NASA Astrophysics Data System (ADS)

Trewartha, Daniel; Kamleh, Waseem; Leinweber, Derek B.

2017-12-01

The influence of centre vortices on dynamical chiral symmetry breaking is investigated through the light hadron spectrum on the lattice. Recent studies of the quark propagator and other quantities have provided evidence that centre vortices are the fundamental objects underpinning dynamical chiral symmetry breaking in {SU}(3) gauge theory. For the first time, we use the chiral overlap fermion action to study the low-lying hadron spectrum on lattice ensembles consisting of Monte Carlo, vortex-removed, and vortex-projected gauge fields. We find that gauge field configurations consisting solely of smoothed centre vortices are capable of reproducing all the salient features of the hadron spectrum, including dynamical chiral symmetry breaking. The hadron spectrum on vortex-removed fields shows clear signals of chiral symmetry restoration at light values of the bare quark mass, while at heavy masses the spectrum is consistent with a theory of weakly interacting constituent quarks.

Two-stages of chiral selectivity in the molecular self-assembly of tryptophan

NASA Astrophysics Data System (ADS)

Guisinger, Nathan

Both chirality and molecular assembly are essential and key components to life. In this study we explore the molecular assembly of the amino acid tryptophan (both L- and D- chiralities) on Cu(111). Our investigation utilizes low temperature scanning tunneling microscopy to observe resulting assemblies at the molecular scale. We find that depositing a racemic mixture of both L- and D- tryptophan results in the assembly of basic 6 molecule ``Lego'' structures that are enantiopure. These enantiopure ``Legos'' further assemble into 1-dimensional chains one block at a time. These resulting chains are also enantiopure with chiral selectivity occurring at two stages of assembly. Utilizing scanning tunneling spectroscopy we are able to probe the electronic structure of the chiral Legos that give insight into the root of the observed selectivity. Two-stages of chiral selectivity in the molecular self-assembly of tryptophan.

Enhanced Circular Dichroism via Symmetry Breaking in a Chiral Plasmonic Nanoparticle Oligomer

NASA Astrophysics Data System (ADS)

Le, Khai Q.

2018-02-01

A chiral plasmonic nanoparticle oligomer, consisting of four symmetrically arranged nanodisks of different heights and having different optical absorption responses to left and right-handed circularly polarized light illumination, has been experimentally reported in the literature. The resulting circular dichroism (CD) signal was detectable with state of the art CD spectrometers but was much weaker than those of existing chiral nanostructures, i.e., three-dimensional (3-D) chiral metamaterials. In this letter, via symmetry breaking in such an oligomer, the author demonstrates that the CD can be enhanced up to six times compared to that of a symmetric oligomer, and is in the range of a relevant 3-D chiral metamolecule. Through investigation of geometrical parameters including particle size, asymmetric and symmetric gaps, the CD evolution was reported, which provides a useful guideline for design of two-dimensional chiral oligomers adopted as efficient probes for CD spectroscopic applications.

Dynamic control of chirality in phosphine ligands for enantioselective catalysis

PubMed Central

Zhao, Depeng; Neubauer, Thomas M.; Feringa, Ben L.

2015-01-01

Chirality plays a fundamental role in biology and chemistry and the precise control of chirality in a catalytic conversion is a key to modern synthesis most prominently seen in the production of pharmaceuticals. In enantioselective metal-based catalysis, access to each product enantiomer is commonly achieved through ligand design with chiral bisphosphines being widely applied as privileged ligands. Switchable phosphine ligands, in which chirality is modulated through an external trigger signal, might offer attractive possibilities to change enantioselectivity in a catalytic process in a non-invasive manner avoiding renewed ligand synthesis. Here we demonstrate that a photoswitchable chiral bisphosphine based on a unidirectional light-driven molecular motor, can be used to invert the stereoselectivity of a palladium-catalysed asymmetric transformation. It is shown that light-induced changes in geometry and helicity of the switchable ligand enable excellent selectivity towards the racemic or individual enantiomers of the product in a Pd-catalysed desymmetrization reaction. PMID:25806856

DNA-bridged Chiroplasmonic Assemblies of Nanoparticles

NASA Astrophysics Data System (ADS)

Kotov, Nicholas

2015-03-01

Chirality at nanoscale attracts a lot of attention during the last decade. A number of chiral nanoscale systems had been discovered ranging from individual nanoparticles to helical nanowires and from lithographically defined substrates. DNA bridges make possible in-silico engineering and practical construction of complex assemblies of nanoparticles with of both plasmonic and excitonic nature. In this presentation, expected and unexpected optical effects that we observed in chiral plasmonic and excitonic systems will be demonstrated. Special effort will be placed on the transitioning of theoretical and experimental knowledge about chiral nanoscale systems to applications. The most obvious direction for practical targets was so far, the design of metamaterials for negative refractive index optics. The results describing the 3D materials with the highest experimentally observed chiral anisotropy factor will be presented. It will be followed by the discussion of the recent developments in analytical application of chiral assemblies for detection of cancer and bacterial contamination.

Mass-Selective Chiral Analysis

NASA Astrophysics Data System (ADS)

Boesl, Ulrich; Kartouzian, Aras

2016-06-01

Three ways of realizing mass-selective chiral analysis are reviewed. The first is based on the formation of diastereomers that are of homo- and hetero- type with respect to the enantiomers of involved chiral molecules. This way is quite well-established with numerous applications. The other two ways are more recent developments, both based on circular dichroism (CD). In one, conventional or nonlinear electronic CD is linked to mass spectrometry (MS) by resonance-enhanced multiphoton ionization. The other is based on CD in the angular distribution of photoelectrons, which is measured in combination with MS via photoion photoelectron coincidence. Among the many important applications of mass-selective chiral analysis, this review focuses on its use as an analytical tool for the development of heterogeneous enantioselective chemical catalysis. There exist other approaches to combine chiral analysis and mass-selective detection, such as chiral chromatography MS, which are not discussed here.

Centre vortex removal restores chiral symmetry

DOE PAGES

Trewartha, Daniel; Kamleh, Waseem; Leinweber, Derek B.

2017-11-15

The influence of centre vortices on dynamical chiral symmetry breaking is investigated through the light hadron spectrum on the lattice. Recent studies of the quark propagator and other quantities have provided evidence that centre vortices are the fundamental objects underpinning dynamical chiral symmetry breaking in SU(3) gauge theory. For the first time, we use the chiral overlap fermion action to study the low-lying hadron spectrum on lattice ensembles consisting of Monte Carlo, vortex-removed, and vortex-projected gauge fields. We find that gauge field configurations consisting solely of smoothed centre vortices are capable of reproducing all the salient features of the hadronmore » spectrum, including dynamical chiral symmetry breaking. In conclusion, the hadron spectrum on vortex-removed fields shows clear signals of chiral symmetry restoration at light values of the bare quark mass, while at heavy masses the spectrum is consistent with a theory of weakly-interacting constituent quarks.« less

Spin-Dependent Transport through Chiral Molecules Studied by Spin-Dependent Electrochemistry

PubMed Central

2016-01-01

Conspectus Molecular spintronics (spin + electronics), which aims to exploit both the spin degree of freedom and the electron charge in molecular devices, has recently received massive attention. Our recent experiments on molecular spintronics employ chiral molecules which have the unexpected property of acting as spin filters, by way of an effect we call “chiral-induced spin selectivity” (CISS). In this Account, we discuss new types of spin-dependent electrochemistry measurements and their use to probe the spin-dependent charge transport properties of nonmagnetic chiral conductive polymers and biomolecules, such as oligopeptides, L/D cysteine, cytochrome c, bacteriorhodopsin (bR), and oligopeptide-CdSe nanoparticles (NPs) hybrid structures. Spin-dependent electrochemical measurements were carried out by employing ferromagnetic electrodes modified with chiral molecules used as the working electrode. Redox probes were used either in solution or when directly attached to the ferromagnetic electrodes. During the electrochemical measurements, the ferromagnetic electrode was magnetized either with its magnetic moment pointing “UP” or “DOWN” using a permanent magnet (H = 0.5 T), placed underneath the chemically modified ferromagnetic electrodes. The spin polarization of the current was found to be in the range of 5–30%, even in the case of small chiral molecules. Chiral films of the l- and d-cysteine tethered with a redox-active dye, toludin blue O, show spin polarizarion that depends on the chirality. Because the nickel electrodes are susceptible to corrosion, we explored the effect of coating them with a thin gold overlayer. The effect of the gold layer on the spin polarization of the electrons ejected from the electrode was investigated. In addition, the role of the structure of the protein on the spin selective transport was also studied as a function of bias voltage and the effect of protein denaturation was revealed. In addition to “dark” measurements, we also describe photoelectrochemical measurements in which light is used to affect the spin selective electron transport through the chiral molecules. We describe how the excitation of a chromophore (such as CdSe nanoparticles), which is attached to a chiral working electrode, can flip the preferred spin orientation of the photocurrent, when measured under the identical conditions. Thus, chirality-induced spin polarization, when combined with light and magnetic field effects, opens new avenues for the study of the spin transport properties of chiral molecules and biomolecules and for creating new types of spintronic devices in which light and molecular chirality provide new functions and properties. PMID:27797176

Chirality and protein biosynthesis.

PubMed

Banik, Sindrila Dutta; Nandi, Nilashis

2013-01-01

Chirality is present at all levels of structural hierarchy of protein and plays a significant role in protein biosynthesis. The macromolecules involved in protein biosynthesis such as aminoacyl tRNA synthetase and ribosome have chiral subunits. Despite the omnipresence of chirality in the biosynthetic pathway, its origin, role in current pathway, and importance is far from understood. In this review we first present an introduction to biochirality and its relevance to protein biosynthesis. Major propositions about the prebiotic origin of biomolecules are presented with particular reference to proteins and nucleic acids. The problem of the origin of homochirality is unresolved at present. The chiral discrimination by enzymes involved in protein synthesis is essential for keeping the life process going. However, questions remained pertaining to the mechanism of chiral discrimination and concomitant retention of biochirality. We discuss the experimental evidence which shows that it is virtually impossible to incorporate D-amino acids in protein structures in present biosynthetic pathways via any of the two major steps of protein synthesis, namely aminoacylation and peptide bond formation reactions. Molecular level explanations of the stringent chiral specificity in each step are extended based on computational analysis. A detailed account of the current state of understanding of the mechanism of chiral discrimination during aminoacylation in the active site of aminoacyl tRNA synthetase and peptide bond formation in ribosomal peptidyl transferase center is presented. Finally, it is pointed out that the understanding of the mechanism of retention of enantiopurity has implications in developing novel enzyme mimetic systems and biocatalysts and might be useful in chiral drug design.

[Topological models of retention index of thin-layer chromatogram for chiral organic acids].

PubMed

Li, Mingjian; Wang, Yuxiao; Feng, Hui; Feng, Changjun

2014-03-01

On the basis of Kier's molecular connectivity indices and conjugated matrix, novel molecular connectivity indices ((m) G(t)(v)) were defined and calculated for 18 chiral hydroxyl acids and amino acids. The chiral connectivity indices ((m)C(t)(v)) were introduced by extending (m)G(t)(v): (m)C(t)(v) = (m)G(t)(v) x w(j), where w(j) is the chiral index. The quantitative structure-retention index relationship (QSRR) between the retention index (R(M)) of thin-layer chromatogram for the chiral organic acids and (m)C(t)(v) was studied by multivariate statistical regression. By leaps-and-bounds regression analysis, the best four-parameter QSRR model was set up, and the traditional correlation coefficient (R2) and the cross-validation correlation coefficient (Q2) of leave-one-out (LOO) were 0.973 and 0.950, respectively. The results demonstrated that the model was highly reliable and had good predictive ability from the point of view of statistics. From the four parameters (0C(p)(v), 2C(p)(v), C(ch),(v), 5C(p)(v)) of the model, it is known that the dominant influence factors of the retention index were the molecular structure characteristics of two-dimensional and the space factors: the chiral characteristics, the flexibility and the puckered degree of molecules for the chiral organic acids. The results showed that the new parameter mC(t)(v) had good rationality and efficiency for the retention indices of the chiral organic acids. Therefore, an effective method was provided to predict the retention indices of the chiral organic acids.

Electric-field–induced assembly and propulsion of chiral colloidal clusters

PubMed Central

Ma, Fuduo; Wang, Sijia; Wu, David T.; Wu, Ning

2015-01-01

Chiral molecules with opposite handedness exhibit distinct physical, chemical, or biological properties. They pose challenges as well as opportunities in understanding the phase behavior of soft matter, designing enantioselective catalysts, and manufacturing single-handed pharmaceuticals. Microscopic particles, arranged in a chiral configuration, could also exhibit unusual optical, electric, or magnetic responses. Here we report a simple method to assemble achiral building blocks, i.e., the asymmetric colloidal dimers, into a family of chiral clusters. Under alternating current electric fields, two to four lying dimers associate closely with a central standing dimer and form both right- and left-handed clusters on a conducting substrate. The cluster configuration is primarily determined by the induced dipolar interactions between constituent dimers. Our theoretical model reveals that in-plane dipolar repulsion between petals in the cluster favors the achiral configuration, whereas out-of-plane attraction between the central dimer and surrounding petals favors a chiral arrangement. It is the competition between these two interactions that dictates the final configuration. The theoretical chirality phase diagram is found to be in excellent agreement with experimental observations. We further demonstrate that the broken symmetry in chiral clusters induces an unbalanced electrohydrodynamic flow surrounding them. As a result, they rotate in opposite directions according to their handedness. Both the assembly and propulsion mechanisms revealed here can be potentially applied to other types of asymmetric particles. Such kinds of chiral colloids will be useful for fabricating metamaterials, making model systems for both chiral molecules and active matter, or building propellers for microscale transport. PMID:25941383

Emergent chirality in the electric polarization texture of titanate superlattices.

PubMed

Shafer, Padraic; García-Fernández, Pablo; Aguado-Puente, Pablo; Damodaran, Anoop R; Yadav, Ajay K; Nelson, Christopher T; Hsu, Shang-Lin; Wojdeł, Jacek C; Íñiguez, Jorge; Martin, Lane W; Arenholz, Elke; Junquera, Javier; Ramesh, Ramamoorthy

2018-01-30

Chirality is a geometrical property by which an object is not superimposable onto its mirror image, thereby imparting a handedness. Chirality determines many important properties in nature-from the strength of the weak interactions according to the electroweak theory in particle physics to the binding of enzymes with naturally occurring amino acids or sugars, reactions that are fundamental for life. In condensed matter physics, the prediction of topologically protected magnetic skyrmions and related spin textures in chiral magnets has stimulated significant research. If the magnetic dipoles were replaced by their electrical counterparts, then electrically controllable chiral devices could be designed. Complex oxide BaTiO 3 /SrTiO 3 nanocomposites and PbTiO 3 /SrTiO 3 superlattices are perfect candidates, since "polar vortices," in which a continuous rotation of ferroelectric polarization spontaneously forms, have been recently discovered. Using resonant soft X-ray diffraction, we report the observation of a strong circular dichroism from the interaction between circularly polarized light and the chiral electric polarization texture that emerges in PbTiO 3 /SrTiO 3 superlattices. This hallmark of chirality is explained by a helical rotation of electric polarization that second-principles simulations predict to reside within complex 3D polarization textures comprising ordered topological line defects. The handedness of the texture can be topologically characterized by the sign of the helicity number of the chiral line defects. This coupling between the optical and novel polar properties could be exploited to encode chiral signatures into photon or electron beams for information processing.

Enantioselective induction of cytotoxicity by o,p'-DDD in PC12 cells: implications of chirality in risk assessment of POPs metabolites.

PubMed

Wang, Cui; Li, Zhuoyu; Zhang, Quan; Zhao, Meirong; Liu, Weiping

2013-04-16

The increased release of chiral persistent organic pollutants (POPs) into the environment has resulted in more attention to the role of enantioselectivity in the fate and ecotoxicological effects of these compounds. Although the enantioselectivity of chiral POPs has been considered in previous studies, little effort has been expended to discern the enantiospecific effects of chiral POPs metabolites, which may impede comprehensive risk assessments of these chemicals. In the present study, o,p'-DDD, the chiral metabolite of o,p'-DDT, was used as a model chiral metabolite. First, a preferential chiral separation at 100% ethanol was employed to obtain a pure enantiomer. The enantioselective cytotoxicity of o,p'-DDD in rat cells (PC12) was evaluated by detecting activation of the cellular apoptosis and oxidative stress systems and microarray analysis. We have documented for the first time that R-(+)-o,p'-DDD increases apoptosis by selectively disturbing the oxidative system (enzymes and molecules) and regulating the transcription of Aven, Bid, Cideb and Tp53. By comparing the data from the present study to data derived from the parent compound, we concluded that the R-enantiomer is the more detrimental stereostructure for both o,p'-DDT and o,p'-DDD. This observed stereostructural effect is in line with the structure-activity relationship formulated at other structural levels. Biological activities of the chiral metabolites are likely to occur in the same absolute configuration between chiral POPs and their metabolites provided that they have the similar stereostructures.

Chiral nematic porous germania and germanium/carbon films

NASA Astrophysics Data System (ADS)

Xu, Jing; Nguyen, Thanh-Dinh; Xie, Kai; Hamad, Wadood Y.; MacLachlan, Mark J.

2015-07-01

We report our extensive attempts and, ultimately, success to produce crack-free, chiral nematic GeO2/cellulose nanocrystal (CNC) composite films with tunable photonic properties from the controlled assembly of germanium(iv) alkoxides with the lyotropic liquid-crystalline CNCs in a mixed solvent of water/DMF. With different pyrolysis conditions, the photonic GeO2/CNC composites can be converted into freestanding chiral nematic films of amorphous GeO2, and semiconducting mesoporous GeO2/C and Ge/C replicas. These new materials are promising for chiral separation, enantioselective adsorption, catalysis, sensing, optoelectronics, and lithium ion batteries. Furthermore, the new, reproducible synthesis strategies developed may be applicable for constructing other composites and porous materials with chiral nematic ordering.We report our extensive attempts and, ultimately, success to produce crack-free, chiral nematic GeO2/cellulose nanocrystal (CNC) composite films with tunable photonic properties from the controlled assembly of germanium(iv) alkoxides with the lyotropic liquid-crystalline CNCs in a mixed solvent of water/DMF. With different pyrolysis conditions, the photonic GeO2/CNC composites can be converted into freestanding chiral nematic films of amorphous GeO2, and semiconducting mesoporous GeO2/C and Ge/C replicas. These new materials are promising for chiral separation, enantioselective adsorption, catalysis, sensing, optoelectronics, and lithium ion batteries. Furthermore, the new, reproducible synthesis strategies developed may be applicable for constructing other composites and porous materials with chiral nematic ordering. Electronic supplementary information (ESI) available: TGA, IR, Raman, TEM, SEM, BET. See DOI: 10.1039/c5nr02520f

Application of cyanuric chloride-based six new chiral derivatizing reagents having amino acids and amino acid amides as chiral auxiliaries for enantioresolution of proteinogenic amino acids by reversed-phase high-performance liquid chromatography.

PubMed

Bhushan, Ravi; Dixit, Shuchi

2012-04-01

Six dichloro-s-triazine (DCT) reagents having L-Leu, D-Phg, L-Val, L-Met, L-Ala and L-Met-NH(2) as chiral auxiliaries in cyanuric chloride were introduced for enantioseparation of 13 proteinogenic amino acids. Four other DCTs and six monochloro-s-triazine (MCT) reagents having amino acid amides as chiral auxiliaries were also synthesized. These 16 chiral derivatizing reagents (CDRs) were used for synthesis of diastereomers of all the 13 analytes using microwave irradiation, which were resolved by reversed-phase high-performance liquid chromatography (RP-HPLC) using C18 column and gradient eluting mixture of aqueous TFA and acetonitrile with UV detection at 230 nm. It required only 60-90 s for derivatization using microwave irradiation. Better resolution and lower retention times were observed for the diastereomers prepared with CDRs having amino acids as chiral auxiliaries as compared to counterparts prepared with reagents having amino acid amides as chiral auxiliaries. As the best resolution of all the 13 analytes was observed for their diastereomers prepared using the DCT reagent having L-Leu as chiral auxiliary, this CDR was further employed for derivatization of Lys, Tyr, His and Arg followed by RP-HPLC analysis of resulting diastereomers. The results are discussed in light of acid and amide groups of chiral auxiliaries constituting CDRs, electronegativities of the atoms of achiral moieties constituting CDRs and hydrophobicities of side chains of amino acids constituting CDRs and analytes.

HPLC SEPARATION OF CHIRAL ORGANOPHOSPHORUS PESTICIDES ON POLYSACCHARIDE CHIRAL STATIONARY PHASES

EPA Science Inventory

High-performance liquid chromatographic separation of the individual enantiomers of 12 organophosphorus pesticides (OPs) were obtained on polysaccharide chiral HPLC columns using an alkane-alcohol mobile phase. The OP pesticides were crotoxyphos, dialifor, dyfonate, fenamiphos, ...

PESTICIDE EXPOSURE AND CHIRAL CHEMISTRY: THE PYRETHROID FAMILY

EPA Science Inventory

Advances in chiral chromatography significantly advanced the ability to analyze individual enantiomers of chiral compounds. These techniques are being employed at the U.S. EPA for human exposure and ecological research studies. Enantiomer fractions (EFs) were measured for cisp...

Enantiopure heterobimetallic single-chain magnets from the chiral Ru(III) building block.

PubMed

Ru, Jing; Gao, Feng; Wu, Tao; Yao, Min-Xia; Li, Yi-Zhi; Zuo, Jing-Lin

2014-01-21

A pair of one-dimensional enantiomers based on the versatile chiral dicyanoruthenate(III) building block have been synthesized and they are chiral single-chain magnets with the effective spin-reversal barrier of 28.2 K.

Furo-fused BINOL based crown as a fluorescent chiral sensor for enantioselective recognition of phenylethylamine and ethyl ester of valine.

PubMed

Upadhyay, Sunil P; Pissurlenkar, Raghuvir R S; Coutinho, Evans C; Karnik, Anil V

2007-07-20

A furo-fused BINOL based chiral crown was developed as an enantioselective chiral sensor for phenylethylamine and ethyl ester of valine. Fusion of furan to BINOL has resulted in a highly stereo-discriminating backbone for the chiral crown developed. This chiral crown exhibited a fluorescence enhancement difference of 2.97 times between two enantiomers of phenylethylamine and 2.55 times between two enantiomers of ethyl ester of valine. The ratio of association constants for two diastereomeric complexes of two enantiomers of phenylethylamine was found to be 11.30, and the ratio for two enantiomers of ethyl ester of valine was 7.02.

Chiral Magnetic Effect in Heavy Ion Collisions

DOE PAGES

Liao, Jinfeng

2016-12-01

The Chiral Magnetic Effect (CME) is a remarkable phenomenon that stems from highly nontrivial interplay of QCD chiral symmetry, axial anomaly, and gluonic topology. We show it is of fundamental importance to search for the CME in experiments. The heavy ion collisions provide a unique environment where a hot chiral-symmetric quark-gluon plasma is created, gluonic topological fluctuations generate chirality imbalance, and very strong magnetic fields |Β →|~m 2 π are present during the early stage of such collisions. Significant efforts have been made to look for CME signals in heavy ion collision experiments. Lastly, in this contribution we give amore » brief overview on the status of such efforts.« less

Self-organized internal architectures of chiral micro-particles

NASA Astrophysics Data System (ADS)

Provenzano, Clementina; Mazzulla, Alfredo; Pagliusi, Pasquale; De Santo, Maria P.; Desiderio, Giovanni; Perrotta, Ida; Cipparrone, Gabriella

2014-02-01

The internal architecture of polymeric self-assembled chiral micro-particles is studied by exploring the effect of the chirality, of the particle sizes, and of the interface/surface properties in the ordering of the helicoidal planes. The experimental investigations, performed by means of different microscopy techniques, show that the polymeric beads, resulting from light induced polymerization of cholesteric liquid crystal droplets, preserve both the spherical shape and the internal self-organized structures. The method used to create the micro-particles with controlled internal chiral architectures presents great flexibility providing several advantages connected to the acquired optical and photonics capabilities and allowing to envisage novel strategies for the development of chiral colloidal systems and materials.

Optimized fan-shaped chiral metamaterial as an ultrathin narrow-band circular polarizer at visible frequencies

NASA Astrophysics Data System (ADS)

He, Yizhuo; Wang, Xinghai; Ingram, Whitney; Ai, Bin; Zhao, Yiping

2018-04-01

Chiral metamaterials have the great ability to manipulate the circular polarizations of light, which can be utilized to build ultrathin circular polarizers. Here we build a narrow-band circular polarizer at visible frequencies based on plasmonic fan-shaped chiral nanostructures. In order to achieve the best optical performance, we systematically investigate how different fabrication factors affect the chiral optical response of the fan-shaped chiral nanostructures, including incident angle of vapor depositions, nanostructure thickness, and post-deposition annealing. The optimized fan-shaped nanostructures show two narrow bands for different circular polarizations with the maximum extinction ratios 7.5 and 6.9 located at wavelength 687 nm and 774 nm, respectively.

Chirality-induced magnon transport in AA-stacked bilayer honeycomb chiral magnets.

PubMed

Owerre, S A

2016-11-30

In this Letter, we study the magnetic transport in AA-stacked bilayer honeycomb chiral magnets coupled either ferromagnetically or antiferromagnetically. For both couplings, we observe chirality-induced gaps, chiral protected edge states, magnon Hall and magnon spin Nernst effects of magnetic spin excitations. For ferromagnetically coupled layers, thermal Hall and spin Nernst conductivities do not change sign as function of magnetic field or temperature similar to single-layer honeycomb ferromagnetic insulator. In contrast, for antiferromagnetically coupled layers, we observe a sign change in the thermal Hall and spin Nernst conductivities as the magnetic field is reversed. We discuss possible experimental accessible honeycomb bilayer quantum materials in which these effects can be observed.

Experimental results on chiral magnetic and vortical effects

DOE PAGES

Wang, Gang; Wen, Liwen

2017-01-12

Various novel transport phenomena in chiral systems result from the interplay of quantum anomalies with magnetic field and vorticity in high-energy heavy-ion collisions and could survive the expansion of the fireball and be detected in experiments. Among them are the chiral magnetic effect, the chiral vortical effect, and the chiral magnetic wave, the experimental searches for which have aroused extensive interest. As a result, the goal of this review is to describe the current status of experimental studies at Relativistic Heavy-Ion Collider at BNL and the Large Hadron Collider at CERN and to outline the future work in experiment neededmore » to eliminate the existing uncertainties in the interpretation of the data.« less

Mueller matrix spectroscopic ellipsometry study of chiral nanocrystalline cellulose films

NASA Astrophysics Data System (ADS)

Mendoza-Galván, Arturo; Muñoz-Pineda, Eloy; Ribeiro, Sidney J. L.; Santos, Moliria V.; Järrendahl, Kenneth; Arwin, Hans

2018-02-01

Chiral nanocrystalline cellulose (NCC) free-standing films were prepared through slow evaporation of aqueous suspensions of cellulose nanocrystals in a nematic chiral liquid crystal phase. Mueller matrix (MM) spectroscopic ellipsometry is used to study the polarization and depolarization properties of the chiral films. In the reflection mode, the MM is similar to the matrices reported for the cuticle of some beetles reflecting near circular left-handed polarized light in the visible range. The polarization properties of light transmitted at normal incidence for different polarization states of incident light are discussed. By using a differential decomposition of the MM, the structural circular birefringence and dichroism of a NCC chiral film are evaluated.

Simulating Chiral Magnetic and Separation Effects with Spin-Orbit Coupled Atomic Gases

PubMed Central

Huang, Xu-Guang

2016-01-01

The chiral magnetic and chiral separation effects—quantum-anomaly-induced electric current and chiral current along an external magnetic field in parity-odd quark-gluon plasma—have received intense studies in the community of heavy-ion collision physics. We show that analogous effects occur in rotating trapped Fermi gases with Weyl-Zeeman spin-orbit coupling where the rotation plays the role of an external magnetic field. These effects can induce a mass quadrupole in the atomic cloud along the rotation axis which may be tested in future experiments. Our results suggest that the spin-orbit coupled atomic gases are potential simulators of the chiral magnetic and separation effects. PMID:26868084

Pure chiral optical fibres.

PubMed

Poladian, L; Straton, M; Docherty, A; Argyros, A

2011-01-17

We investigate the properties of optical fibres made from chiral materials, in which a contrast in optical activity forms the waveguide, rather than a contrast in the refractive index; we refer to such structures as pure chiral fibres. We present a mathematical formulation for solving the modes of circularly symmetric examples of such fibres and examine the guidance and polarisation properties of pure chiral step-index, Bragg and photonic crystal fibre designs. Their behaviour is shown to differ for left- and right-hand circular polarisation, allowing circular polarisations to be isolated and/or guided by different mechanisms, as well as differing from equivalent non-chiral fibres. The strength of optical activity required in each case is quantified.

The Origin and Limit of Asymmetric Transmission in Chiral Resonators.

PubMed

Parappurath, Nikhil; Alpeggiani, Filippo; Kuipers, L; Verhagen, Ewold

2017-04-19

We observe that the asymmetric transmission (AT) through photonic systems with a resonant chiral response is strongly related to the far-field properties of eigenmodes of the system. This understanding can be used to predict the AT for any resonant system from its complex eigenmodes. We find that the resonant chiral phenomenon of AT is related to, and is bounded by, the nonresonant scattering properties of the system. Using the principle of reciprocity, we determine a fundamental limit to the maximum AT possible for a single mode in any chiral resonator. We propose and follow a design route for a highly chiral dielectric photonic crystal structure that reaches this fundamental limit for AT.

The Origin and Limit of Asymmetric Transmission in Chiral Resonators

PubMed Central

2017-01-01

We observe that the asymmetric transmission (AT) through photonic systems with a resonant chiral response is strongly related to the far-field properties of eigenmodes of the system. This understanding can be used to predict the AT for any resonant system from its complex eigenmodes. We find that the resonant chiral phenomenon of AT is related to, and is bounded by, the nonresonant scattering properties of the system. Using the principle of reciprocity, we determine a fundamental limit to the maximum AT possible for a single mode in any chiral resonator. We propose and follow a design route for a highly chiral dielectric photonic crystal structure that reaches this fundamental limit for AT. PMID:28470027

Boundary states in the chiral symmetric systems with a spatial symmetry

NASA Astrophysics Data System (ADS)

Xiao, Jinpeng; An, Jin

2018-02-01

We study topological systems with both a chiral and a spatial symmetry which result in an additional spatial chiral symmetry. We distinguish the topologically nontrivial states according to the chiral symmetries protecting them and study several models in 1D and 3D systems. The perturbations breaking the spatial symmetry can break only one of the two chiral symmetries while the perturbations preserving the spatial symmetry always break or preserve both of them. In 3D systems, besides the 3D symmetries, the topologically nontrivial boundary modes may also be protected by the hidden lower dimensional symmetries. We then figure out the corresponding topological invariants and connect them with the 3D invariants.

Novel Chiral Magnetic Domain Wall Structure in Fe/Ni/Cu(001) Films

NASA Astrophysics Data System (ADS)

Chen, G.; Zhu, J.; Quesada, A.; Li, J.; N'Diaye, A. T.; Huo, Y.; Ma, T. P.; Chen, Y.; Kwon, H. Y.; Won, C.; Qiu, Z. Q.; Schmid, A. K.; Wu, Y. Z.

2013-04-01

Using spin-polarized low energy electron microscopy, we discovered a new type of domain wall structure in perpendicularly magnetized Fe/Ni bilayers grown epitaxially on Cu(100). Specifically, we observed unexpected Néel-type walls with fixed chirality in the magnetic stripe phase. Furthermore, we find that the chirality of the domain walls is determined by the film growth order with the chirality being right handed in Fe/Ni bilayers and left handed in Ni/Fe bilayers, suggesting that the underlying mechanism is the Dzyaloshinskii-Moriya interaction at the film interfaces. Our observations may open a new route to control chiral spin structures using interfacial engineering in transition metal heterostructures.

Homochiral 3D Metal-Organic Frameworks from Chiral 1D Rods: 6 – Way Helical Packing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shin, Sung M.; Moon, Dohyun; Jeong, Kyung S.

2011-07-20

The chiral 3D MOFs resulted from the packing of chiral 1D SBBs were studied. It was demonstrated that the final packing pattern is dependent on the dimension of SBB's. In addition, we were able to identify a new plywood-like network from ligand 2H2 exhibiting an unprecedented six-way chiral helical packing motif, which can be added on the list of invariant rod packings.

Towards noninvasive drug distribution in tissues: coherent Raman microspectroscopy of chiral molecules

NASA Astrophysics Data System (ADS)

Petrov, Georgi I.; Yakovlev, Vladislav V.

2017-02-01

Many biologically active molecules are chiral. Many drugs, which are currently in use, are supplied as an equimolar mixture of enantiomers. Although they have the same chemical structure, i.e. are not distinguishable by conventional Raman spectroscopy, most isomers of chiral drugs exhibit marked differences in biological activities such as pharmacology, toxicology, pharmacokinetics, metabolism, etc. In this report we introduced a new spectroscopic tool to extend nonlinear Raman spectroscopy to chiral substances.

Chiral phases of fundamental and adjoint quarks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Natale, A. A.; Instituto de Física Teórica - UNESP Rua Dr. Bento T. Ferraz, 271, Bl.II - 01140-070, São Paulo, SP

2016-01-22

We consider a QCD chiral symmetry breaking model where the gap equation contains an effective confining propagator and a dressed gluon propagator with a dynamically generated mass. This model is able to explain the ratios between the chiral transition and deconfinement temperatures in the case of fundamental and adjoint quarks. It also predicts the recovery of the chiral symmetry for a large number of quarks (n{sub f} ≈ 11 – 13) in agreement with lattice data.

Spontaneously amplified homochiral organic-inorganic nano-helix complexes via self-proliferation.

PubMed

Zhai, Halei; Quan, Yan; Li, Li; Liu, Xiang-Yang; Xu, Xurong; Tang, Ruikang

2013-04-07

Most spiral coiled biomaterials in nature, such as gastropod shells, are homochiral, and the favoured chiral feature can be precisely inherited. This inspired us that selected material structures, including chirality, could be specifically replicated into the self-similar populations; however, a physicochemical understanding of the material-based heritage is unknown. We study the homochirality by using calcium phosphate mineralization in the presence of racemic amphiphilic molecules and biological protein. The organic-inorganic hybrid materials with spiral coiling characteristics are produced at the nanoscale. The resulted helixes are chiral with the left- and right-handed characteristics, which are agglomerated hierarchically to from clusters and networks. It is interesting that each cluster or network is homochiral so that the enantiomorphs can be separated readily. Actually, each homochiral architecture is evolved from an original chiral helix, demonstrating the heritage of the matrix chirality during the material proliferation under a racemic condition. By using the Ginzburg-Landaue expression we find that the chiral recognition in the organic-inorganic hybrid formation may be determined by a spontaneous chiral separation and immobilization of asymmetric amphiphilic molecules on the mineral surface, which transferred the structural information from the mother matrix to the descendants by an energetic control. This study shows how biomolecules guide the selective amplification of chiral materials via spontaneous self-replication. Such a strategy can be applied generally in the design and production of artificial materials with self-similar structure characteristics.

Chiral Superstructure Mesophases of Achiral Bent-Shaped Molecules - Hierarchical Chirality Amplification and Physical Properties.

PubMed

Le, Khoa V; Takezoe, Hideo; Araoka, Fumito

2017-07-01

Chiral mesophases in achiral bent-shaped molecules have attracted particular attention since their discovery in the middle 1990s, not only because of their homochirality and polarity, but also due to their unique physical/physicochemical properties. Here, the most intriguing results in the studies of such symmetry-broken states, mainly helical-nanofilament (HNF) and dark-conglomerate (DC) phases, are reviewed. Firstly, basic information on the typical appearance and optical activity in these phases is introduced. In the following section, the formation of mesoscopic chiral superstructures in the HNF and DC phases is discussed in terms of hierarchical chirality. Nanoscale phase segregation in mixture systems and gelation ability in the HNF phase are also described. In addition, some other related chiral phases of bent-shaped molecules are shown. Recent attempts to control such mesoscopic chiral structure and the alignment/confinement of HNFs are also discussed, along with several examples of their fascinating advanced physical properties, i.e. huge enhancement of circular dichroism, electro- and photo-tunable optical activities, chirality-induced nonlinear optics (second-harmonic-generation circular difference and electrogyration effect), enhanced hydrophobicity through the dual-scale surface morphological modulation, and photoconductivity in the HNF/fullerene binary system. Future prospects from basic science and application viewpoints are also indicated in the concluding section. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stability of topological defects in chiral superconductors: London theory.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vakaryuk, V.

2011-12-22

This paper examines the thermodynamic stability of chiral domain walls and vortices-topological defects which can exist in chiral superconductors. Using London theory it is demonstrated that at sufficiently small applied and chiral fields the existence of domain walls and vortices in the sample is not favored and the sample's configuration is a single domain. The particular chirality of the single-domain configuration is neither favored nor disfavored by the applied field. Increasing the field leads to an entry of a domain-wall loop or a vortex into the sample. The formation of a straight domain wall is never preferred in equilibrium. Valuesmore » of the entry (critical) fields for both types of defects, as well as the equilibrium size of the domain-wall loop, are calculated. We also consider a mesoscopic chiral sample and calculate its zero-field magnetization, susceptibility, and a change in the magnetic moment due to a vortex or a domain-wall entry. We show that in the case of a soft domain wall whose energetics is dominated by the chiral current (and not by the surface tension) its behavior in mesoscopic samples is substantially different from that in the bulk case and can be used for a controllable transfer of edge excitations. The applicability of these results to Sr{sub 2}RuO{sub 4} - a tentative chiral superconductor - is discussed.« less

Stability of topological defects in chiral superconductors: London theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vakaryuk, Victor

2011-12-01

This paper examines the thermodynamic stability of chiral domain walls and vortices—topological defects which can exist in chiral superconductors. Using London theory it is demonstrated that at sufficiently small applied and chiral fields the existence of domain walls and vortices in the sample is not favored and the sample's configuration is a single domain. The particular chirality of the single-domain configuration is neither favored nor disfavored by the applied field. Increasing the field leads to an entry of a domain-wall loop or a vortex into the sample. The formation of a straight domain wall is never preferred in equilibrium. Valuesmore » of the entry (critical) fields for both types of defects, as well as the equilibrium size of the domain-wall loop, are calculated. We also consider a mesoscopic chiral sample and calculate its zero-field magnetization, susceptibility, and a change in the magnetic moment due to a vortex or a domain-wall entry. We show that in the case of a soft domain wall whose energetics is dominated by the chiral current (and not by the surface tension) its behavior in mesoscopic samples is substantially different from that in the bulk case and can be used for a controllable transfer of edge excitations. The applicability of these results to Sr 2 RuO 4 —a tentative chiral superconductor—is discussed.« less

Specific heat of the chiral-soliton-lattice phase in Yb(Ni0.94Cu0.06)3Al9

NASA Astrophysics Data System (ADS)

Ninomiya, Hiroki; Sato, Takaaki; Inoue, Katsuya; Ohara, Shigeo

2018-05-01

We have studied the monoaxial-chiral helimagnet YbNi3Al9 and its-substituted analogue Yb(Ni0.94Cu0.06)3Al9. These compounds belong to a chiral space group R32. In Yb(Ni0.94Cu0.06)3Al9 with the magnetic ordering temperature TM = 6.4 K , only when the magnetic field is applied perpendicular to the helical axis, the chiral soliton lattice is observed below Hc = 10 kOe . YbNi3Al9 with TM = 3.4 K exhibits a metamagnetic transition at Hc = 1 kOe in 2 K. To study the formation of chiral helimagnetic state and chiral soliton lattice, we have measured the specific heat in magnetic fields applied parallel and perpendicular to the helical axis. In zero field, with decreasing temperature, specific heat shows λ-type phase transition from paramagnetic state to chiral helimagnetic one. At the temperature where the chiral soliton lattice emerges, we have found that the specific heat shows a sharp peak. In addition, at around the crossover between paramagnetic state and forced-ferromagnetic one, a broad maximum has been observed. We have determined the magnetic phase diagrams of YbNi3Al9 and Yb(Ni0.94Cu0.06)3Al9.

Chirality Relay in 2,2'-Substituted 1,1'-Binaphthyl: Access to Propeller Chirality of the Tricoordinate Boron Center.

PubMed

Wang, Chen; Sun, Zuo-Bang; Xu, Qing-Wen; Zhao, Cui-Hua

2016-11-14

It is a challenging issue to achieve propeller chirality for triarylboranes owing to the low transition barrier between the P and M forms of the boron center. Herein, we report a new strategy to achieve propeller chirality of triarylboranes. It was found that the chirality relay from axially chiral 1,1'-binaphthyl to propeller chirality of the trivalent boron center can be realized when a Me 2 N and a Mes 2 B group (Mes=mesityl) are introduced at the 2,2'-positions of the 1,1'-binaphthyl skeleton (BN-BNaph) owing to the strong π-π interaction between the Me 2 N-bonded naphthyl ring and the phenyl ring of one adjacent Mes group, which not only exerts great steric hindrance on the rotation of the two Mes groups but also gives unequal stability to the two configurations of the boron center for a given configuration of the binaphthyl moiety. The stereostructures of the boron center were fully characterized through 1 H NMR spectroscopy, X-ray crystal analyses, and theoretical calculations. Detailed comparisons with the analog BN-Ph-BNaph, in which the Mes 2 B group is separated from 1,1'-binaphthyl by a para-phenylene spacer, confirmed the essential role of π-π interaction for the successful chirality relay in BN-BNaph. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Separation mechanism of chiral impurities, ephedrine and pseudoephedrine, found in amphetamine-type substances using achiral modifiers in the gas phase.

PubMed

Holness, Howard K; Jamal, Adeel; Mebel, Alexander; Almirall, José R

2012-11-01

A new mechanism is proposed that describes the gas-phase separation of chiral molecules found in amphetamine-type substances (ATS) by the use of high-resolution ion mobility spectrometry (IMS). Straight-chain achiral alcohols of increasing carbon chain length, from methanol to n-octanol, are used as drift gas modifiers in IMS to highlight the mechanism proposed for gas-phase separations of these chiral molecules. The results suggest the possibility of using these achiral modifiers to separate the chiral molecules (R,S) and (S,R)-ephedrine and (S,S) and (R,R)-pseudoephedrine which contain an internal hydroxyl group at the first chiral center and an amino group at the other chiral center. Ionization was achieved with an electrospray source, the ions were introduced into an IMS with a resolving power of 80, and the resulting ion clusters were characterized with a coupled quadrupole mass spectrometer detector. A complementary computational study conducted at the density functional B3LYP/6-31g level of theory for the electronic structure of the analyte-modifier clusters was also performed, and showed either "bridged" or "independent" binding. The combined experimental and simulation data support the proposed mechanism for gas-phase chiral separations using achiral modifiers in the gas phase, thus enhancing the potential to conduct fast chiral separations with relative ease and efficiency.

Visualizing the chiral anomaly in Dirac and Weyl semimetals with photoemission spectroscopy

NASA Astrophysics Data System (ADS)

Behrends, Jan; Grushin, Adolfo G.; Ojanen, Teemu; Bardarson, Jens H.

2016-02-01

Quantum anomalies are the breaking of a classical symmetry by quantum fluctuations. They dictate how physical systems of diverse nature, ranging from fundamental particles to crystalline materials, respond topologically to external perturbations, insensitive to local details. The anomaly paradigm was triggered by the discovery of the chiral anomaly that contributes to the decay of pions into photons and influences the motion of superfluid vortices in 3He-A. In the solid state, it also fundamentally affects the properties of topological Weyl and Dirac semimetals, recently realized experimentally. In this work we propose that the most identifying consequence of the chiral anomaly, the charge density imbalance between fermions of different chirality induced by nonorthogonal electric and magnetic fields, can be directly observed in these materials with the existing technology of photoemission spectroscopy. With angle resolution, the chiral anomaly is identified by a characteristic note-shaped pattern of the emission spectra, originating from the imbalanced occupation of the bulk states and a previously unreported momentum dependent energy shift of the surface state Fermi arcs. We further demonstrate that the chiral anomaly likewise leaves an imprint in angle averaged emission spectra, facilitating its experimental detection. Thereby, our work provides essential theoretical input to foster the direct visualization of the chiral anomaly in condensed matter, in contrast to transport properties, such as negative magnetoresistance, which can also be obtained in the absence of a chiral anomaly.

Enantioselective column coupled electrophoresis employing large bore capillaries hyphenated with tandem mass spectrometry for ultra-trace determination of chiral compounds in complex real samples.

PubMed

Piešťanský, Juraj; Maráková, Katarína; Kovaľ, Marián; Havránek, Emil; Mikuš, Peter

2015-12-01

A new multidimensional analytical approach for the ultra-trace determination of target chiral compounds in unpretreated complex real samples was developed in this work. The proposed analytical system provided high orthogonality due to on-line combination of three different methods (separation mechanisms), i.e. (1) isotachophoresis (ITP), (2) chiral capillary zone electrophoresis (chiral CZE), and (3) triple quadrupole mass spectrometry (QqQ MS). The ITP step, performed in a large bore capillary (800 μm), was utilized for the effective sample pretreatment (preconcentration and matrix clean-up) in a large injection volume (1-10 μL) enabling to obtain as low as ca. 80 pg/mL limits of detection for the target enantiomers in urine matrices. In the chiral CZE step, the different chiral selectors (neutral, ionizable, and permanently charged cyclodextrins) and buffer systems were tested in terms of enantioselectivity and influence on the MS detection response. The performance parameters of the optimized ITP - chiral CZE-QqQ MS method were evaluated according to the FDA guidance for bioanalytical method validation. Successful validation and application (enantioselective monitoring of renally eliminated pheniramine and its metabolite in human urine) highlighted great potential of this chiral approach in advanced enantioselective biomedical applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chiral Crystallization of Ethylenediamine Sulfate

ERIC Educational Resources Information Center

Koby, Lawrence; Ningappa, Jyothi B.; Dakesssian, Maria; Cuccia, Louis A.

2005-01-01

The optimal conditions for the crystallization of achiral ethylenediamine sulfate into large chiral crystals that are ideal for polarimetry studies and observation using Polaroid sheets are presented. This experiment is an ideal undergraduate experiment, which clearly demonstrates the chiral crystallization of an achiral molecule.

Lattice modes of the chirally pure and racemic phases of tyrosine crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belyanchikov, M. A.; Gorelik, V. S., E-mail: gorelik@sci.lebedev.ru; Gorshunov, B. P.

High-Q librational modes have been found to be present in the infrared absorption and Raman spectra of chirally pure L-tyrosine. Such modes can serve as terahertz radiation detectors and generators in chirally pure biostructures.

GLOBAL EFFECTS OF VARIOUS SOIL TREATMENTS ON TRANSFORMATIONS OF CHIRAL PESTICIDES

EPA Science Inventory

Many pesticides and other organic pollutants are chiral, and their enantiomers exhibit differences in biological properties, including rates of microbial degradation. We have measured by chiral GC and capillary electrophoresis the enantioselectivity of biodegradation of three pe...

Highly convergent synthesis of chiral bicyclophosphinates by domino hydrophosphinylation/Michael/Michael reaction.

PubMed

Fourgeaud, Pierre; Daydé, Bénédicte; Volle, Jean-Noël; Vors, Jean-Pierre; Van der Lee, Arie; Pirat, Jean-Luc; Virieux, David

2011-10-07

Diastereoselective domino reactions of iminoalcohols and allenyl H-phosphinates produce chiral phosphorus bicycles in a regio- and stereoselective fashion. A predictive model for diastereoselection is used for these new chiral phosphinic esters. © 2011 American Chemical Society

Directing the phase behavior of polyelectrolyte complexes using chiral patterned peptides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pacalin, Naomi M.; Leon, Lorraine; Tirrell, Matthew

Polyelectrolyte complexes (PECs) have a broad range of promising applications as soft materials due to their self-assembly and diversity of structure and chemical composition. Peptide polymer PECs are highly biocompatible and biodegradable, making them particularly useful for encapsulation of food additives and flavors, micellar drug delivery, medical and underwater adhesives, fetal membrane patches, and scaffolds for cell growth in tissue engineering. While parameters affecting PEC formation and stability in regards to charge effects are well researched, little is known about the effects of van der Waals interactions, hydrogen bonding, and secondary structure in these materials. Peptide chirality provides a uniquemore » opportunity to manipulate PEC phase to modulate the amount of solid-like (precipitate) or liquid-like (coacervate) character by influencing hydrogen bonding interactions among peptide chains. In previous work, we showed that chiral peptides form solid complexes, while complexes with even one racemic peptide were fluid. This raised the interesting question of how long a homochiral sequence must be to result in solid phase formation. In this work, we designed chiral patterned peptides of polyglutamic acid and polylysine ranging from 50 to 90% L-chiral residues with increasing numbers of sequential L-chiral residues before a chirality change. These polymers were mixed together to form PECs. We observed that 8 or more sequential L-chiral residues are necessary to achieve both the appearance of a precipitate phase and sustained beta-sheets in the complex, as determined by optical imaging and FTIR Spectroscopy. Less homochiral content results in formation of a coacervate phase. Thus, we show that chiral sequence can be used to control the phase transition of PECs. Understanding how to manipulate PEC phase using chiral sequence as presented here may enable tuning of the material properties to achieve the desired mechanical strength for coatings and polymer brushes, or the most effective molecular release kinetics for drug delivery applications, for example.« less

Chiral Symmetry Breaking in Peptide Systems During Formation of Life on Earth.

PubMed

Konstantinov, Konstantin K; Konstantinova, Alisa F

2018-03-01

Chiral symmetry breaking in complex chemical systems with a large number of amino acids and a large number of similar reactions was considered. It was shown that effective averaging over similar reaction channels may result in very weak effective enantioselectivity of forward reactions, which does not allow most of the known models to result in chiral symmetry breaking during formation of life on Earth. Models with simple and catalytic synthesis of a single amino acid, formation of peptides up to length five, and sedimentation of insoluble pair of substances were considered. It was shown that depending on the model and the values of the parameters, chiral symmetry breaking may occur in up to about 10% out of all possible unique insoluble pair combinations even in the absence of any catalytic synthesis and that minimum total number of amino acids in the pair is 5. If weak enantioselective forward catalytic synthesis of amino acids is present, then the number of possible variants, in which chiral symmetry breaking may occur, increases substantially. It was shown that that the most interesting catalysts have zero or one amino acid of "incorrect" chirality. If the parameters of the model are adjusted in such a way to result in an increase of concentration of longer peptides, then catalysts with two amino acids of incorrect chirality start to appear at peptides of length five. Models of chiral symmetry breaking in the presence of epimerization were considered for peptides up to length three. It was shown that the range of parameters in which chiral symmetry breaking could occur significantly shrinks in comparison to previously considered models with peptides up to length two. An experiment of chiral symmetry breaking was proposed. The experiment consists of a three-step cycle: reversible catalytic synthesis of amino acids, reversible synthesis of peptides, and irreversible sedimentation of insoluble substances.

Chiral dynamos and magnetogenesis induced by torsionful Maxwell-Chern Simons electrodynamics

NASA Astrophysics Data System (ADS)

de Andrade, L. C. Garcia

2018-03-01

Recently chiral anomalous currents have been investigated by Boyarsky et al. and Brandenburg et al. with respect to applications to the early universe. In this paper we show that these magnetic field anomalies, which can give rise to dynamo magnetic field amplification can also be linked to spacetime torsion through the use of a chemical potential and Maxwell electrodynamics with torsion firstly proposed by de Sabbata and Gasperini. When the axial torsion is constant this electrodynamics acquires the form of a Maxwell-Chern-Simmons (MCS) equations where the chiral current appears naturally and the zero component of torsion plays the role of a chemical potential, while the other components play the role of anisotropic conductivity. The chiral dynamo equation in torsionful spacetime is derived here from MSC electrodynamics. Here we have used a recently derived a torsion LV bound of T0˜ {10^{-26}} GeV and the constraint that this chiral magnetic field is a seed for galactic dynamo. This estimate is weaker than the one obtained from the chiral battery seed of ˜ {10^{30}} G without making use of Cartan torsion. The torsion obtained here was derived at 500 pc coherence scale. When a chiral MF is forced to seed a galactic dynamo one obtains a yet weaker MF, of the order of B˜ {10^{12}} G, which is the value of a MF at nucleosynthesis. By the use of chiral dynamo equations from parity-violating torsion one obtains a seed field of B˜ {10^{27}} G, which is a much stronger MF closer to the one obtained by making use of chiral batteries. Chiral vortical currents in non-Riemannian spacetimes derived in Riemannian spaces previously by Flaschi and Fukushima are extended to include minimal coupling with torsion. The present universe yields B˜ {10^{-24}} G, still sufficient to seed galactic dynamos.

Directing the phase behavior of polyelectrolyte complexes using chiral patterned peptides

NASA Astrophysics Data System (ADS)

Pacalin, Naomi M.; Leon, Lorraine; Tirrell, Matthew

2016-10-01

Polyelectrolyte complexes (PECs) have a broad range of promising applications as soft materials due to their self-assembly and diversity of structure and chemical composition. Peptide polymer PECs are highly biocompatible and biodegradable, making them particularly useful for encapsulation of food additives and flavors, micellar drug delivery, medical and underwater adhesives, fetal membrane patches, and scaffolds for cell growth in tissue engineering. While parameters affecting PEC formation and stability in regards to charge effects are well researched, little is known about the effects of van der Waals interactions, hydrogen bonding, and secondary structure in these materials. Peptide chirality provides a unique opportunity to manipulate PEC phase to modulate the amount of solid-like (precipitate) or liquid-like (coacervate) character by influencing hydrogen bonding interactions among peptide chains. In previous work, we showed that chiral peptides form solid complexes, while complexes with even one racemic peptide were fluid. This raised the interesting question of how long a homochiral sequence must be to result in solid phase formation. In this work, we designed chiral patterned peptides of polyglutamic acid and polylysine ranging from 50 to 90% L-chiral residues with increasing numbers of sequential L-chiral residues before a chirality change. These polymers were mixed together to form PECs. We observed that 8 or more sequential L-chiral residues are necessary to achieve both the appearance of a precipitate phase and sustained β-sheets in the complex, as determined by optical imaging and FTIR Spectroscopy. Less homochiral content results in formation of a coacervate phase. Thus, we show that chiral sequence can be used to control the phase transition of PECs. Understanding how to manipulate PEC phase using chiral sequence as presented here may enable tuning of the material properties to achieve the desired mechanical strength for coatings and polymer brushes, or the most effective molecular release kinetics for drug delivery applications, for example.

Chiral Symmetry Breaking in Peptide Systems During Formation of Life on Earth

NASA Astrophysics Data System (ADS)

Konstantinov, Konstantin K.; Konstantinova, Alisa F.

2018-03-01

Chiral symmetry breaking in complex chemical systems with a large number of amino acids and a large number of similar reactions was considered. It was shown that effective averaging over similar reaction channels may result in very weak effective enantioselectivity of forward reactions, which does not allow most of the known models to result in chiral symmetry breaking during formation of life on Earth. Models with simple and catalytic synthesis of a single amino acid, formation of peptides up to length five, and sedimentation of insoluble pair of substances were considered. It was shown that depending on the model and the values of the parameters, chiral symmetry breaking may occur in up to about 10% out of all possible unique insoluble pair combinations even in the absence of any catalytic synthesis and that minimum total number of amino acids in the pair is 5. If weak enantioselective forward catalytic synthesis of amino acids is present, then the number of possible variants, in which chiral symmetry breaking may occur, increases substantially. It was shown that that the most interesting catalysts have zero or one amino acid of "incorrect" chirality. If the parameters of the model are adjusted in such a way to result in an increase of concentration of longer peptides, then catalysts with two amino acids of incorrect chirality start to appear at peptides of length five. Models of chiral symmetry breaking in the presence of epimerization were considered for peptides up to length three. It was shown that the range of parameters in which chiral symmetry breaking could occur significantly shrinks in comparison to previously considered models with peptides up to length two. An experiment of chiral symmetry breaking was proposed. The experiment consists of a three-step cycle: reversible catalytic synthesis of amino acids, reversible synthesis of peptides, and irreversible sedimentation of insoluble substances.

New thermotropic chiral nematic polymers. 3. Copolymers containing a cyanobiphenyl group and (S)-(-)-1-phenylethanol or (S)-(-)-1-phenylethylamine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mastrangelo, J.C.; Chen, S.H.

Thermotropic chiral nematics in thin films on the order of 10 [mu]m possess a unique optical property, selective wavelength reflection, that forms the basis of a number of potential applications including circular polarizers, notch filters, beamsplitters, and so on. Instead of low molar mass chiral nematics, thermotropic copolymers have been actively pursued as an alternative in view of the possibility of achieving long-term mesophase stability and optical characteristics desired for passive device applications. Cyanobiphenyl is a relatively high birefringent group which is known to contribute to the formation of low molar mass liquid crystals; it was found to exhibit amore » nematic mesophase between the glass transition and clearing temperatures in side-chain polyacrylates with spacer lengths in the 2-6 range. However, there exists only one report on the formation of a chiral nematic copolymer with cholesterol as the chiral moiety. Since several chiral building blocks other than cholesterol have been found to possess strong helical twisting powers with selected nematogenic monomers, it would be of interest to explore a cyanobiphenyl group as a building block for the synthesis of new chiral nematic copolymers.« less

Quantitatively analyzing the mechanism of giant circular dichroism in extrinsic plasmonic chiral nanostructures by tracking the interplay of electric and magnetic dipoles.

PubMed

Hu, Li; Tian, Xiaorui; Huang, Yingzhou; Fang, Liang; Fang, Yurui

2016-02-14

Plasmonic chirality has drawn much attention because of tunable circular dichroism (CD) and the enhancement for chiral molecule signals. Although various mechanisms have been proposed to explain the plasmonic CD, a quantitative explanation like the ab initio mechanism for chiral molecules, is still unavailable. In this study, a mechanism similar to the mechanisms associated with chiral molecules was analyzed. The giant extrinsic circular dichroism of a plasmonic splitting rectangle ring was quantitatively investigated from a theoretical standpoint. The interplay of the electric and magnetic modes of the meta-structure is proposed to explain the giant CD. We analyzed the interplay using both an analytical coupled electric-magnetic dipole model and a finite element method model. The surface charge distributions showed that the circular current yielded by the splitting rectangle ring causes the ring to behave like a magneton at some resonant modes, which then interact with the electric modes, resulting in a mixing of the two types of modes. The strong interplay of the two mode types is primarily responsible for the giant CD. The analysis of the chiral near-field of the structure shows potential applications for chiral molecule sensing.

A chiral sensor based on weak measurement for the determination of Proline enantiomers in diverse measuring circumstances.

PubMed

Li, Dongmei; Guan, Tian; He, Yonghong; Liu, Fang; Yang, Anping; He, Qinghua; Shen, Zhiyuan; Xin, Meiguo

2018-07-01

A new chiral sensor based on weak measurement to accurately measure the optical rotation (OR) has been developed for the estimation of a trace amount of chiral molecule. With the principle of optical weak measurement in frequency domain, the central wavelength shift of output spectra is quantitatively relative to the angle of preselected polarization. Hence, a chiral molecule (e.g., L-amino acid, or D-amino acid) can be enantioselectively determined by modifying the preselection angle with the OR, which will cause the rotation of a polarization plane. The concentration of the chiral sample, corresponding to its optical activity, is quantitatively analyzed with the central wavelength shift of output spectra, which can be collected in real time. Immune to the refractive index change, the proposed chiral sensor is valid in complicated measuring circumstance. The detections of Proline enantiomer concentration in different solvents were implemented. The results demonstrated that weak measurement acted as a reliable method to chiral recognition of Proline enantiomers in diverse circumstance with the merits of high precision and good robustness. In addition, this real-time monitoring approach plays a crucial part in asymmetric synthesis and biological systems. Copyright © 2018. Published by Elsevier B.V.

Theoretical model of chirality-induced helical self-propulsion

NASA Astrophysics Data System (ADS)

Yamamoto, Takaki; Sano, Masaki

2018-01-01

We recently reported the experimental realization of a chiral artificial microswimmer exhibiting helical self-propulsion [T. Yamamoto and M. Sano, Soft Matter 13, 3328 (2017), 10.1039/C7SM00337D]. In the experiment, cholesteric liquid crystal (CLC) droplets dispersed in surfactant solutions swam spontaneously, driven by the Marangoni flow, in helical paths whose handedness is determined by the chirality of the component molecules of CLC. To study the mechanism of the emergence of the helical self-propelled motion, we propose a phenomenological model of the self-propelled helical motion of the CLC droplets. Our model is constructed by symmetry argument in chiral systems, and it describes the dynamics of CLC droplets with coupled time-evolution equations in terms of a velocity, an angular velocity, and a tensor variable representing the symmetry of the helical director field of the droplet. We found that helical motions as well as other chiral motions appear in our model. By investigating bifurcation behaviors between each chiral motion, we found that the chiral coupling terms between the velocity and the angular velocity, the structural anisotropy of the CLC droplet, and the nonlinearity of model equations play a crucial role in the emergence of the helical motion of the CLC droplet.

Staggered heavy baryon chiral perturbation theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bailey, Jon A.

2008-03-01

Although taste violations significantly affect the results of staggered calculations of pseudoscalar and heavy-light mesonic quantities, those entering staggered calculations of baryonic quantities have not been quantified. Here I develop staggered chiral perturbation theory in the light-quark baryon sector by mapping the Symanzik action into heavy baryon chiral perturbation theory. For 2+1 dynamical quark flavors, the masses of flavor-symmetric nucleons are calculated to third order in partially quenched and fully dynamical staggered chiral perturbation theory. To this order the expansion includes the leading chiral logarithms, which come from loops with virtual decuplet-like states, as well as terms of O(m{sub {pi}}{supmore » 3}), which come from loops with virtual octet-like states. Taste violations enter through the meson propagators in loops and tree-level terms of O(a{sup 2}). The pattern of taste symmetry breaking and the resulting degeneracies and mixings are discussed in detail. The resulting chiral forms are appropriate to lattice results obtained with operators already in use and could be used to study the restoration of taste symmetry in the continuum limit. I assume that the fourth root of the fermion determinant can be incorporated in staggered chiral perturbation theory using the replica method.« less

Chirality and chiroptical properties of amyloid fibrils.

PubMed

Dzwolak, Wojciech

2014-09-01

Chirality of amyloid fibrils-linear beta-sheet-rich aggregates of misfolded protein chains-often manifests in morphological traits such as helical twist visible in atomic force microscopy and in chiroptical properties accessible to vibrational circular dichroism (VCD). According to recent studies the relationship between molecular chirality of polypeptide building blocks and superstructural chirality of amyloid fibrils may be more intricate and less deterministic than previously assumed. Several puzzling experimental findings have put into question earlier intuitive ideas on: 1) the bottom-up chirality transfer upon amyloidogenic self-assembly, and 2) the structural origins of chiroptical properties of protein aggregates. For example, removal of a single amino acid residue from an amyloidogenic all-L peptide was shown to reverse handedness of fibrils. On the other hand, certain types of amyloid aggregates revealed surprisingly strong VCD spectra with the sign and shape dependent on the conditions of fibrillation. Hence, microscopic and chiroptical studies have highlighted chirality as one more aspect of polymorphism of amyloid fibrils. This brief review is intended to outline the current state of research on amyloid-like fibrils from the perspective of their structural and superstructural chirality and chiroptical properties. © 2014 Wiley Periodicals, Inc.

Mirror Symmetry Breaking by Chirality Synchronisation in Liquids and Liquid Crystals of Achiral Molecules.

PubMed

Tschierske, Carsten; Ungar, Goran

2016-01-04

Spontaneous mirror symmetry breaking is an efficient way to obtain homogeneously chiral agents, pharmaceutical ingredients and materials. It is also in the focus of the discussion around the emergence of uniform chirality in biological systems. Tremendous progress has been made by symmetry breaking during crystallisation from supercooled melts or supersaturates solutions and by self-assembly on solid surfaces and in other highly ordered structures. However, recent observations of spontaneous mirror symmetry breaking in liquids and liquid crystals indicate that it is not limited to the well-ordered solid state. Herein, progress in the understanding of a new dynamic mode of symmetry breaking, based on chirality synchronisation of transiently chiral molecules in isotropic liquids and in bicontinuous cubic, columnar, smectic and nematic liquid crystalline phases is discussed. This process leads to spontaneous deracemisation in the liquid state under thermodynamic control, giving rise to long-term stable symmetry-broken fluids, even at high temperatures. These fluids form conglomerates that are capable of extraordinary strong chirality amplification, eventually leading to homochirality and providing a new view on the discussion of emergence of uniform chirality in prebiotic systems. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An implemented method of asymmetric transmission for arbitrary polarization base in multi-layered chiral meta-surface

NASA Astrophysics Data System (ADS)

Xiao, Zhong-yin; Zou, Huan-ling; Xu, Kai-Kai; Tang, Jing-yao

2018-03-01

Asymmetric transmission of linearly or circularly polarized waves is a well-established property not only for three-layered chiral structures but for multi-layered ones. Here we show a method which can simultaneously implement asymmetric transmission for arbitrary base vector polarized wave in multi-layered chiral meta-surface. We systematically study the implemented method based on a multi-layered chiral structure consisting of a y-shape, a half gammadion and an S-shape in the terahertz gap. A numerical simulation was carried out, followed by an explanation of the asymmetric transmission mechanism in these structures proposed in this work. The simulated results indicate that the multi-layered chiral structure can realize a maximum asymmetric transmission of 0.89 and 0.28 for circularly and linearly polarized waves, respectively, which exhibit magnitude improvement over previous chiral metamaterials. Specifically, the maximum asymmetric transmitted coefficient of the multi-layered chiral structure is insensitivity to the incident angles from 0° to 45° for circularly polarized components. Additionally, we also study the influence of structural parameters on the asymmetric transmission effect for both linearly and circularly polarized waves in detail.

Observation of the chiral magnetic effect in ZrTe₅

DOE PAGES

Li, Qiang; Kharzeev, Dmitri E.; Zhang, Cheng; ...

2015-02-08

The chiral magnetic effect is the generation of electric current induced by chirality imbalance in the presence of magnetic field. It is a macroscopic manifestation of the quantum anomaly in relativistic field theory of chiral fermions (massless spin 1/2 particles with a definite projection of spin on momentum) – a dramatic phenomenon arising from a collective motion of particles and antiparticles in the Dirac sea. The recent discovery of Dirac semimetals with chiral quasi-particles opens a fascinating possibility to study this phenomenon in condensed matter experiments. Here we report on the first observation of chiral magnetic effect through the measurementmore » of magneto-transport in zirconium pentatelluride, ZrTe₅. Our angle-resolved photoemission spectroscopy experiments show that this material’s electronic structure is consistent with a 3D Dirac semimetal. We observe a large negative magnetoresistance when magnetic field is parallel with the current. The measured quadratic field dependence of the magnetoconductance is a clear indication of the chiral magnetic effect. Furthermore, the observed phenomenon stems from the effective transmutation of Dirac semimetal into a Weyl semimetal induced by the parallel electric and magnetic fields that represent a topologically nontrivial gauge field background.« less

Chiral Anomalous Dispersion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sadofyev, Andrey; Sen, Srimoyee

The linearized Einstein equation describing graviton propagation through a chiral medium appears to be helicity dependent. We analyze features of the corresponding spectrum in a collision-less regime above a flat background. In the long wave-length limit, circularly polarized metric perturbations travel with a helicity dependent group velocity that can turn negative giving rise to a new type of an anomalous dispersion. We further show that this chiral anomalous dispersion is a general feature of polarized modes propagating through chiral plasmas extending our result to the electromagnetic sector.

Combining the bi-Yang-Baxter deformation, the Wess-Zumino term and TsT transformations in one integrable σ-model

NASA Astrophysics Data System (ADS)

Delduc, F.; Hoare, B.; Kameyama, T.; Magro, M.

2017-10-01

A multi-parameter integrable deformation of the principal chiral model is presented. The Yang-Baxter and bi-Yang-Baxter σ-models, the principal chiral model plus a Wess-Zumino term and the TsT transformation of the principal chiral model are all recovered when the appropriate deformation parameters vanish. When the Lie group is SU(2), we show that this four-parameter integrable deformation of the SU(2) principal chiral model corresponds to the Lukyanov model.

Hawking radiation, covariant boundary conditions, and vacuum states

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banerjee, Rabin; Kulkarni, Shailesh

2009-04-15

The basic characteristics of the covariant chiral current and the covariant chiral energy-momentum tensor are obtained from a chiral effective action. These results are used to justify the covariant boundary condition used in recent approaches of computing the Hawking flux from chiral gauge and gravitational anomalies. We also discuss a connection of our results with the conventional calculation of nonchiral currents and stress tensors in different (Unruh, Hartle-Hawking and Boulware) states.

Isotope chirality in long-armed multifunctional organosilicon ("Cephalopod") molecules.

PubMed

Barabás, Béla; Kurdi, Róbert; Zucchi, Claudia; Pályi, Gyula

2018-07-01

Long-armed multifunctional organosilicon molecules display self-replicating and self-perfecting behavior in asymmetric autocatalysis (Soai reaction). Two representatives of this class were studied by statistical methods aiming at determination of probabilities of natural abundance chiral isotopomers. The results, reported here, show an astonishing richness of possibilities of the formation of chiral isotopically substituted derivatives. This feature could serve as a model for the evolution of biological chirality in prebiotic and early biotic stereochemistry. © 2018 Wiley Periodicals, Inc.

Chiral Anomalous Dispersion

DOE PAGES

Sadofyev, Andrey; Sen, Srimoyee

2018-02-16

The linearized Einstein equation describing graviton propagation through a chiral medium appears to be helicity dependent. We analyze features of the corresponding spectrum in a collision-less regime above a flat background. In the long wave-length limit, circularly polarized metric perturbations travel with a helicity dependent group velocity that can turn negative giving rise to a new type of an anomalous dispersion. We further show that this chiral anomalous dispersion is a general feature of polarized modes propagating through chiral plasmas extending our result to the electromagnetic sector.

Chirality and the angular momentum of light

PubMed Central

Götte, Jörg B.; Barnett, Stephen M.; Yao, Alison M.

2017-01-01

Chirality is exhibited by objects that cannot be rotated into their mirror images. It is far from obvious that this has anything to do with the angular momentum of light, which owes its existence to rotational symmetries. There is nevertheless a subtle connection between chirality and the angular momentum of light. We demonstrate this connection and, in particular, its significance in the context of chiral light–matter interactions. This article is part of the themed issue ‘Optical orbital angular momentum’. PMID:28069764

Chiral vortical effect generated by chiral anomaly in vortex-skyrmions

NASA Astrophysics Data System (ADS)

Volovik, G. E.

2017-03-01

We discuss the type of the general macroscopic parity-violating effects, when there is the current along the vortex, which is concentrated in the vortex core. We consider vortices in chiral superfluids with Weyl points. In the vortex core, the positions of the Weyl points form the skyrmion structure. We show that the mass current concentrated in such a core is provided by the spectral flow through the Weyl points according to the Adler-Bell-Jackiw equation for chiral anomaly.

Regular scanning tunneling microscope tips can be intrinsically chiral.

PubMed

Tierney, Heather L; Murphy, Colin J; Sykes, E Charles H

2011-01-07

We report our discovery that regular scanning tunneling microscope tips can themselves be chiral. This chirality leads to differences in electron tunneling efficiencies through left- and right-handed molecules, and, when using the tip to electrically excite molecular rotation, large differences in rotation rate were observed which correlated with molecular chirality. As scanning tunneling microscopy is a widely used technique, this result may have unforeseen consequences for the measurement of asymmetric surface phenomena in a variety of important fields.

Fluorescence Turn-on Enantioselective Recognition of both Chiral Acidic Compounds and α-Amino Acids by a Chiral Tetraphenylethylene Macrocycle Amine.

PubMed

Feng, Hai-Tao; Zhang, Xing; Zheng, Yan-Song

2015-08-21

New chiral tetraphenylethylene (TPE) macrocycles bearing optically pure amine groups were synthesized and found to have a discriminating ability between the two enantiomers of not only chiral acidic compounds but also α-amino acids by enantioselective aggregation and aggregation-induced emission (AIE) effects. NMR spectra, including 2D-NOESY, disclosed that the host-guest interaction of the macrocycle receptor played a key role in addition to the acid-base interactions.

Regular Scanning Tunneling Microscope Tips can be Intrinsically Chiral

NASA Astrophysics Data System (ADS)

Tierney, Heather L.; Murphy, Colin J.; Sykes, E. Charles H.

2011-01-01

We report our discovery that regular scanning tunneling microscope tips can themselves be chiral. This chirality leads to differences in electron tunneling efficiencies through left- and right-handed molecules, and, when using the tip to electrically excite molecular rotation, large differences in rotation rate were observed which correlated with molecular chirality. As scanning tunneling microscopy is a widely used technique, this result may have unforeseen consequences for the measurement of asymmetric surface phenomena in a variety of important fields.

Impact of pyrrolidine-bispyrrole DNA minor groove binding agents and chirality on global proteomic profile in Escherichia Coli.

PubMed

Yang, Ya-Ting; Lin, Chun-Yu; Jeng, Jingyueh; Ong, Chi-Wi

2013-05-23

There is great interest in the design of small molecules that selectively target minor grooves of duplex DNA for controlling specific gene expression implicated in a disease. The design of chiral small molecules for rational drug design has attracted increasing attention due to the chirality of DNA. Yet, there is limited research on the chirality effect of minor groove binders on DNA interaction, especially at the protein expression level. This paper is an attempt to illustrate that DNA binding affinity might not provide a full picture on the biological activities. Drug interacting at the genomic level can be translated to the proteomic level. Here we have illustrated that although the chiral bispyrrole-pyrrolidine-oligoamides, PySSPy and PyRSPy, showed low binding affinity to DNA, their influence at the proteomic level is significant. More importantly, the chirality also plays a role. Two-dimensional proteomic profile to identify the differentially expressed protein in Escherichia coli DH5α (E coli DH5α) were investigated. E coli DH5α incubated with the chiral PySSPy and PyRSPy, diastereomeric at the pyrrolidine ring, showed differential expression of eighteen proteins as observed through two dimensional proteomic profiling. These eighteen proteins identified by MALDI_TOF/TOF MS include antioxidant defense, DNA protection, protein synthesis, chaperone, and stress response proteins. No statistically significant toxicity was observed at the tested drug concentrations as measured via MTT assay. The current results showed that the chiral PySSPy and PyRSPy impact on the proteomic profiling of E coli DH5α, implicating the importance of drug chirality on biological activities at the molecular level.

Adsorption of lactic acid on chiral Pt surfaces—A density functional theory study

NASA Astrophysics Data System (ADS)

Franke, J.-H.; Kosov, D. S.

2013-02-01

The adsorption of the chiral molecule lactic acid on chiral Pt surfaces is studied by density functional theory calculations. First, we study the adsorption of L-lactic acid on the flat Pt(111) surface. Using the optimed PBE - van der Waals (oPBE-vdW) functional, which includes van der Waals forces on an ab initio level, it is shown that the molecule has two binding sites, a carboxyl and the hydroxyl oxygen atoms. Since real chiral surfaces are (i) known to undergo thermal roughening that alters the distribution of kinks and step edges but not the overall chirality and (ii) kink sites and edge sites are usually the energetically most favored adsorption sites, we focus on two surfaces that allow qualitative sampling of the most probable adsorption sites. We hereby consider chiral surfaces exhibiting (111) facets, in particular, Pt(321) and Pt(643). The binding sites are either both on kink sites—which is the case for Pt(321) or on one kink site—as on Pt(643). The binding energy of the molecule on the chiral surfaces is much higher than on the Pt(111) surface. We show that the carboxyl group interacts more strongly than the hydroxyl group with the kink sites. The results indicate the possible existence of very small chiral selectivities of the order of 20 meV for the Pt(321) and Pt(643) surfaces. L-lactic acid is more stable on Pt(321)S than D-lactic acid, while the chiral selectivity is inverted on Pt(643)S. The most stable adsorption configurations of L- and D-lactic acid are similar for Pt(321) but differ for Pt(643). We explore the impact of the different adsorption geometries on the work function, which is important for field ion microscopy.

Unusual dimeric tetrahydroxanthone derivatives from Aspergillus lentulus and the determination of their axial chiralities

NASA Astrophysics Data System (ADS)

Li, Tian-Xiao; Yang, Ming-Hua; Wang, Ying; Wang, Xiao-Bing; Luo, Jun; Luo, Jian-Guang; Kong, Ling-Yi

2016-12-01

The research on secondary metabolites of Aspergillus lentulus afforded eight unusual heterodimeric tetrahydroxanthone derivatives, lentulins A-H (2-9), along with the known compound neosartorin (1). Compounds 1-6 exhibited potent antimicrobial activities especially against methicillin-resistant Staphylococci. Their absolute configurations, particularly the axial chiralities, were unambiguously demonstrated by a combination of electronic circular dichroism (ECD), Rh2(OCOCF3)4-induced ECD experiments, modified Mosher methods, and chemical conversions. Interestingly, compounds 1-4 were the first samples of atropisomers within the dimeric tetrahydroxanthone class. Further investigation of the relationships between their axial chiralities and ECD Cotton effects led to the proposal of a specific CD Exciton Chirality rule to determine the axial chiralities in dimeric tetrahydroxanthones and their derivatives.

Dense baryon matter with isospin and chiral imbalance in the framework of a NJL4 model at large Nc: Duality between chiral symmetry breaking and charged pion condensation

NASA Astrophysics Data System (ADS)

Khunjua, T. G.; Klimenko, K. G.; Zhokhov, R. N.

2018-03-01

In this paper the phase structure of dense quark matter has been investigated at zero temperature in the presence of baryon, isospin and chiral isospin chemical potentials in the framework of massless (3 +1 )-dimensional Nambu-Jona-Lasinio model with two quark flavors. It has been shown that in the large-Nc limit (Nc is the number of colors of quarks) there exists a duality correspondence between the chiral symmetry breaking phase and the charged pion condensation one. The key conclusion of our studies is the fact that chiral isospin chemical potential generates charged pion condensation in dense quark matter with isotopic asymmetry.

Taming instability of magnetic field in chiral medium

NASA Astrophysics Data System (ADS)

Tuchin, Kirill

2018-01-01

Magnetic field is unstable in a medium with time-independent chiral conductivity. Owing to the chiral anomaly, the electromagnetic field and the medium exchange helicity which results in time-evolution of the chiral conductivity. Using the fastest growing momentum and helicity state of the vector potential as an ansatz, the time-evolution of the chiral conductivity and magnetic field is solved analytically. The solution for the hot and cold equations of state shows that the magnetic field does not develop an instability due to helicity conservation. Moreover, as a function of time, it develops a peak only if a significant part of the initial helicity is stored in the medium. The initial helicity determines the height and position of the peak.

Lanthanide tris(β-diketonates) as useful probes for chirality determination of biological amino alcohols in vibrational circular dichroism: ligand to ligand chirality transfer in lanthanide coordination sphere.

PubMed

Miyake, Hiroyuki; Terada, Keiko; Tsukube, Hiroshi

2014-06-01

A series of lanthanide tris(β-diketonates) functioned as useful chirality probes in the vibrational circular dichroism (VCD) characterization of biological amino alcohols. Various chiral amino alcohols induced intense VCD signals upon ternary complexation with racemic lanthanide tris(β-diketonates). The VCD signals observed around 1500 cm(-1) (β-diketonate IR absorption region) correlated well with the stereochemistry and enantiomeric purity of the targeted amino alcohol, while the corresponding monoalcohol, monoamine, and diol substrates induced very weak VCD signals. The high-coordination number and dynamic property of the lanthanide complex offer an effective chirality VCD probing of biological substrates. © 2014 Wiley Periodicals, Inc.

Chiral and deconfinement phase transition in the Hamiltonian approach to QCD in Coulomb gauge

NASA Astrophysics Data System (ADS)

Reinhardt, H.; Vastag, P.

2016-11-01

The chiral and deconfinement phase transitions are investigated within the variational Hamiltonian approach to QCD in Coulomb gauge. The temperature β-1 is introduced by compactifying a spatial dimension. Thereby the whole temperature dependence is encoded in the vacuum state on the spatial manifold R2×S1(β ) . The chiral quark condensate and the dual quark condensate (dressed Polyakov loop) are calculated as a function of the temperature. From their inflection points the pseudocritical temperatures for the chiral and deconfinement crossover transitions are determined. Using the zero-temperature quark and gluon propagators obtained within the variational approach as input, we find 170 and 198 MeV, respectively, for the chiral and deconfinement transition.

Chiral topological insulator of magnons

NASA Astrophysics Data System (ADS)

Li, Bo; Kovalev, Alexey A.

2018-05-01

We propose a magnon realization of 3D topological insulator in the AIII (chiral symmetry) topological class. The topological magnon gap opens due to the presence of Dzyaloshinskii-Moriya interactions. The existence of the topological invariant is established by calculating the bulk winding number of the system. Within our model, the surface magnon Dirac cone is protected by the sublattice chiral symmetry. By analyzing the magnon surface modes, we confirm that the backscattering is prohibited. By weakly breaking the chiral symmetry, we observe the magnon Hall response on the surface due to opening of the gap. Finally, we show that by changing certain parameters, the system can be tuned between the chiral topological insulator, three-dimensional magnon anomalous Hall, and Weyl magnon phases.

Chiral capillary electrophoresis and nuclear magnetic resonance investigation on the structure-enantioselectivity relationship in synthetic cyclopeptides as chiral selectors.

PubMed

De Lorenzi, E; Massolini, G; Molinari, P; Galbusera, C; Longhi, R; Marinzi, C; Consonni, R; Chiari, M

2001-04-01

In the present work, synthetic cyclohexa- and cycloheptapeptides previously singled out by a combinatorial chemistry approach have been evaluated as chiral selectors in capillary electrophoresis. By applying the countercurrent migration technique and employing a new adsorbed coating, a series of dinitrophenyl amino acids as well as some chiral compounds of pharmaceutical interest have been evaluated for enantiorecognition. The results thus obtained led to a deeper investigation of the chiral discrimination process, by carrying out nuclear magnetic resonance (NMR) studies on selected cyclopeptide-analyte complexes. These studies shed light on the chemical groups involved in the analyte-selector interaction and provided useful information for a wider application of these cyclopeptides in the separation of other drug enantiomers.

Proposal for chiral-boson search at LHC via their unique new signature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chizhov, M. V.; Bednyakov, V. A.; Budagov, J. A.

The resonance production of new chiral spin-1 bosons and their detection through the Drell-Yan process at the CERN LHC is considered. Quantitative evaluations of various differential cross sections of the chiral-boson production are made within the CalcHEP package. The new neutral chiral bosons can be observed as a Breit-Wigner resonance peak in the invariant-dilepton-mass distribution, as usual. However, unique new signatures of the chiral bosons exist. First, there is no Jacobian peak in the lepton transverse-momentum distribution. Second, the lepton angular distribution in the Collins-Soper frame for the high on-peak invariant masses of the lepton pairs has a peculiar 'swallowtail'more » shape.« less

APPLICATION OF ELECTROPHORESIS TO STUDY THE ENANTIOSELECTIVE TRANSFORMATION OF FIVE CHIRAL PESTICIDES IN AEROBIC SOIL SLURRIES

EPA Science Inventory

The enantiomers of five chiral pesticides of environmental interest, metalaxyl, imazaquin, fonofos (dyfonate), ruelene (cruformate) and dichlorprop, were separated analytically using capillary electrophoresis (CE) with cyclodextrin chiral selectors. CE is shown to be a simple, ef...

Two-Dimensional Chirality in Three-Dimensional Chemistry.

ERIC Educational Resources Information Center

Wintner, Claude E.

1983-01-01

The concept of two-dimensional chirality is used to enhance students' understanding of three-dimensional stereochemistry. This chirality is used as a key to teaching/understanding such concepts as enaniotropism, diastereotopism, pseudoasymmetry, retention/inversion of configuration, and stereochemical results of addition to double bonds. (JN)

CAPILLARY ELECTROPHORESIS FOR ENANTIOMER SEPARATION AND MEASUREMENT OF ENANTIOSELECTIVITY OF CHIRAL POLLUTANTS IN THE ENVIRONMENT

EPA Science Inventory

Chiral pollutants exist as 2 species, -- enantiomers - that have identical physical and chemical properties except when they interact with enzymes or other chiral molecules; then they usually react selectively. This enantioselectivity results in different rates of microbial trans...

Chiral phase structure of three flavor QCD at vanishing baryon number density

DOE PAGES

Bazavov, A.; Ding, H. -T.; Hegde, P.; ...

2017-04-12

In this paper, we investigate the phase structure of QCD with three degenerate quark flavors as a function of the degenerate quark masses at vanishing baryon number density. We use the highly improved staggered quarks on lattices with temporal extent N τ = 6 and perform calculations for six values of quark masses, which in the continuum limit correspond to pion masses in the range 80 MeV ≲ m π ≲ 230 MeV. By analyzing the volume and temperature dependence of the chiral condensate and chiral susceptibility, we find no direct evidence for a first-order phase transition in this rangemore » of pion mass values. Finally, relying on the universal scaling behaviors of the chiral observables near an anticipated chiral critical point, we estimate an upper bound for the critical pion mass m c π ≲ 50 MeV, below which a region of first-order chiral phase transition is favored.« less

Chiromagnetic nanoparticles and gels

NASA Astrophysics Data System (ADS)

Yeom, Jihyeon; Santos, Uallisson S.; Chekini, Mahshid; Cha, Minjeong; de Moura, André F.; Kotov, Nicholas A.

2018-01-01

Chiral inorganic nanostructures have high circular dichroism, but real-time control of their optical activity has so far been achieved only by irreversible chemical changes. Field modulation is a far more desirable path to chiroptical devices. We hypothesized that magnetic field modulation can be attained for chiral nanostructures with large contributions of the magnetic transition dipole moments to polarization rotation. We found that dispersions and gels of paramagnetic Co3O4 nanoparticles with chiral distortions of the crystal lattices exhibited chiroptical activity in the visible range that was 10 times as strong as that of nonparamagnetic nanoparticles of comparable size. Transparency of the nanoparticle gels to circularly polarized light beams in the ultraviolet range was reversibly modulated by magnetic fields. These phenomena were also observed for other nanoscale metal oxides with lattice distortions from imprinted amino acids and other chiral ligands. The large family of chiral ceramic nanostructures and gels can be pivotal for new technologies and knowledge at the nexus of chirality and magnetism.

Chiral EFT based nuclear forces: achievements and challenges

NASA Astrophysics Data System (ADS)

Machleidt, R.; Sammarruca, F.

2016-08-01

During the past two decades, chiral effective field theory has become a popular tool to derive nuclear forces from first principles. Two-nucleon interactions have been worked out up to sixth order of chiral perturbation theory and three-nucleon forces up to fifth order. Applications of some of these forces have been conducted in nuclear few- and many-body systems—with a certain degree of success. But in spite of these achievements, we are still faced with great challenges. Among them is the issue of a proper uncertainty quantification of predictions obtained when applying these forces in ab initio calculations of nuclear structure and reactions. A related problem is the order by order convergence of the chiral expansion. We start this review with a pedagogical introduction and then present the current status of the field of chiral nuclear forces. This is followed by a discussion of representative examples for the application of chiral two- and three-body forces in the nuclear many-body system including convergence issues.

Enzymes useful for chiral compound synthesis: structural biology, directed evolution, and protein engineering for industrial use.

PubMed

Kataoka, Michihiko; Miyakawa, Takuya; Shimizu, Sakayu; Tanokura, Masaru

2016-07-01

Biocatalysts (enzymes) have many advantages as catalysts for the production of useful compounds as compared to chemical catalysts. The stereoselectivity of the enzymes is one advantage, and thus the stereoselective production of chiral compounds using enzymes is a promising approach. Importantly, industrial application of the enzymes for chiral compound production requires the discovery of a novel useful enzyme or enzyme function; furthermore, improving the enzyme properties through protein engineering and directed evolution approaches is significant. In this review, the significance of several enzymes showing stereoselectivity (quinuclidinone reductase, aminoalcohol dehydrogenase, old yellow enzyme, and threonine aldolase) in chiral compound production is described, and the improvement of these enzymes using protein engineering and directed evolution approaches for further usability is discussed. Currently, enzymes are widely used as catalysts for the production of chiral compounds; however, for further use of enzymes in chiral compound production, improvement of enzymes should be more essential, as well as discovery of novel enzymes and enzyme functions.

Self-Assembled Chiral Photonic Crystals from a Colloidal Helix Racemate.

PubMed

Lei, Qun-Li; Ni, Ran; Ma, Yu-Qiang

2018-06-20

Chiral crystals consisting of microhelices have many optical properties, while presently available fabrication processes limit their large-scale applications in photonic devices. Here, by using a simplified simulation method, we investigate a bottom-up self-assembly route to build up helical crystals from the smectic monolayer of a colloidal helix racemate. With increasing the density, the system undergoes an entropy-driven cocrystallization by forming crystals of various symmetries with different helical shapes. In particular, we identify two crystals of helices arranged in binary honeycomb and square lattices, which are essentially composed of two sets of opposite-handed chiral crystals. Photonic calculations show that these chiral structures can have large complete photonic band gaps. In addition, in the self-assembled chiral square crystal, we also find dual polarization band gaps that selectively forbid the propagation of circularly polarized light of a specific handedness along the helical axis direction. The self-assembly process in our proposed system is robust, suggesting possibilities of using chiral colloids to assemble photonic metamaterials.

Direct organocatalytic enantioselective functionalization of SiOx surfaces.

PubMed

Parkin, John David; Chisholm, Ross; Frost, Aileen B; Bailey, Richard G; Smith, Andrew David; Hähner, Georg

2018-06-05

Traditional methods to prepare chiral surfaces involve either the adsorption of a chiral molecule onto an achiral surface, or adsorption of a species that forms a chiral template creating lattices with long range order. To date only limited alternative strategies to prepare chiral surfaces have been studied. In this manuscript a "bottom up" approach is developed that allows the preparation of chiral surfaces by direct enantioselective organocatalysis on a functionalized Si-oxide supported self-assembled monolayer (SAM). The efficient catalytic generation of enantiomerically enriched organic surfaces is achieved using a commercially available homogeneous isothiourea catalyst (HyperBTM) that promotes an enantioselective Michael-lactonization process upon a Si-oxide supported self-assembled monolayer functionalized with a reactive trifluoroenone group. Chiral atomic force microscopy (chi-AFM) is used to probe the enantiomeric enrichment of the organic films by measurement of the force distributions arising from interaction of D- or L-cysteine modified AFM tips and the organic films. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chiral optical response of planar and symmetric nanotrimers enabled by heteromaterial selection

PubMed Central

Banzer, Peter; Woźniak, Paweł; Mick, Uwe; De Leon, Israel; Boyd, Robert W.

2016-01-01

Chirality is an intriguing property of certain molecules, materials or artificial nanostructures, which allows them to interact with the spin angular momentum of the impinging light field. Due to their chiral geometry, they can distinguish between left- and right-hand circular polarization states or convert them into each other. Here we introduce an approach towards optical chirality, which is observed in individual two-dimensional and geometrically mirror-symmetric nanostructures. In this scheme, the chiral optical response is induced by the chosen heterogeneous material composition of a particle assembly and the corresponding resonance behaviour of the constituents it is built from, which breaks the symmetry of the system. As a proof of principle, we investigate such a structure composed of individual silicon and gold nanoparticles both experimentally, as well as numerically. Our proposed concept constitutes an approach for designing two-dimensional chiral media tailored at the nanoscale, allowing for high tunability of their optical response. PMID:27734960

Lithium Enolates in the Enantioselective Construction of Tetrasubstituted Carbon Centers with Chiral Lithium Amides as Noncovalent Stereodirecting Auxiliaries.

PubMed

Yu, Kai; Lu, Ping; Jackson, Jeffrey J; Nguyen, Thuy-Ai D; Alvarado, Joseph; Stivala, Craig E; Ma, Yun; Mack, Kyle A; Hayton, Trevor W; Collum, David B; Zakarian, Armen

2017-01-11

Lithium enolates derived from carboxylic acids are ubiquitous intermediates in organic synthesis. Asymmetric transformations with these intermediates, a central goal of organic synthesis, are typically carried out with covalently attached chiral auxiliaries. An alternative approach is to utilize chiral reagents that form discrete, well-defined aggregates with lithium enolates, providing a chiral environment conducive of asymmetric bond formation. These reagents effectively act as noncovalent, or traceless, chiral auxiliaries. Lithium amides are an obvious choice for such reagents as they are known to form mixed aggregates with lithium enolates. We demonstrate here that mixed aggregates can effect highly enantioselective transformations of lithium enolates in several classes of reactions, most notably in transformations forming tetrasubstituted and quaternary carbon centers. Easy recovery of the chiral reagent by aqueous extraction is another practical advantage of this one-step protocol. Crystallographic, spectroscopic, and computational studies of the central reactive aggregate, which provide insight into the origins of selectivity, are also reported.

Polyoxometalates-based chiral frameworks involving helical motifs generated by spontaneous resolution

NASA Astrophysics Data System (ADS)

Li, Ning; Jiang, Dingding; Pan, Qiliang; Zhao, Jianguo; Zhang, Sufang; Xing, Baoyan; Du, Yaqin; Zhang, Zhong; Liu, Shuxia

2018-05-01

Two enantiomerically 3D chiral polyoxometalate frameworks L,D-[K(H2O)]6[H2GeMo2W10O40]3ṡ40H2O (1a and 1b), were conventionally synthesized and characterized by X-ray single-crystal diffraction, IR spectrum, elemental analysis, powder X-ray diffraction, thermogravimetric analysis, UV-Vis spectroscopy, circular dichroism spectra. Structural analysis indicates that 1a and 1b are enantiomers. The terminal O and μ2-O atoms of Keggin-type polyanion [GeMo2W10O40]4- and {K(H2O)}n segments are connected one another to form 1D chiral helical chains, which are further extended by the achiral Keggin-type [GeMo2W10O40]4- anion to construct 3D 4,8-connected chiral frameworks. The enantiomers were isolated by spontaneous resolution during crystallization without any chiral auxiliary. They represent rare examples of enantiomerically pure chiral polyoxometalate-based inorganic porous frameworks.

Loading direction-dependent shear behavior at different temperatures of single-layer chiral graphene sheets

NASA Astrophysics Data System (ADS)

Zhao, Yang; Dong, Shuhong; Yu, Peishi; Zhao, Junhua

2018-06-01

The loading direction-dependent shear behavior of single-layer chiral graphene sheets at different temperatures is studied by molecular dynamics (MD) simulations. Our results show that the shear properties (such as shear stress-strain curves, buckling strains, and failure strains) of chiral graphene sheets strongly depend on the loading direction due to the structural asymmetry. The maximum values of both the critical buckling shear strain and the failure strain under positive shear deformation can be around 1.4 times higher than those under negative shear deformation. For a given chiral graphene sheet, both its failure strain and failure stress decrease with increasing temperature. In particular, the amplitude to wavelength ratio of wrinkles for different chiral graphene sheets under shear deformation using present MD simulations agrees well with that from the existing theory. These findings provide physical insights into the origins of the loading direction-dependent shear behavior of chiral graphene sheets and their potential applications in nanodevices.

Quantification of Magnetic Surface and Edge States in an FeGe Nanostripe by Off-Axis Electron Holography

NASA Astrophysics Data System (ADS)

Song, Dongsheng; Li, Zi-An; Caron, Jan; Kovács, András; Tian, Huanfang; Jin, Chiming; Du, Haifeng; Tian, Mingliang; Li, Jianqi; Zhu, Jing; Dunin-Borkowski, Rafal E.

2018-04-01

Whereas theoretical investigations have revealed the significant influence of magnetic surface and edge states on Skyrmonic spin texture in chiral magnets, experimental studies of such chiral states remain elusive. Here, we study chiral edge states in an FeGe nanostripe experimentally using off-axis electron holography. Our results reveal the magnetic-field-driven formation of chiral edge states and their penetration lengths at 95 and 240 K. We determine values of saturation magnetization MS by analyzing the projected in-plane magnetization distributions of helices and Skyrmions. Values of MS inferred for Skyrmions are lower by a few percent than those for helices. We attribute this difference to the presence of chiral surface states, which are predicted theoretically in a three-dimensional Skyrmion model. Our experiments provide direct quantitative measurements of magnetic chiral boundary states and highlight the applicability of state-of-the-art electron holography for the study of complex spin textures in nanostructures.

IR properties of chiral effects in pionic matter

NASA Astrophysics Data System (ADS)

Avdoshkin, A.; Sadofyev, A. V.; Zakharov, V. I.

2018-04-01

Chiral effects exhibit peculiar universality in idealized theoretical limits. However, they are known to be infrared sensitive and get modified in more realistic settings. In this work we study how the corresponding conductivities vary with the constituent mass. We concentrate on a pionic realization of chiral effects which provides a better control over infrared properties of the theory. The pionic medium is considered at finite vector and axial isospin chemical potentials in the presence of an external magnetic field. This system supports electric and axial isospin currents along the magnetic field which correspond to chiral magnetic and chiral separation effects. We show that these currents are sensitive to the finite mass of the constituents but the conductivities follow a simple scaling with the corresponding charge densities as one would expect for polarization effects. It is argued that this relation can capture the dependence of chiral effects on other infrared parameters. Finally, we briefly comment on the realization of the 't Hooft matching condition in pionic media at finite densities.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stauber, Mark; Yeshiva University, 2495 Amsterdam Avenue, New York, NY 10033-3312; Jakoncic, Jean

Crystallization of lysozyme with (R)-2-methyl-2, 4-pentanediol produces more ordered crystals and a higher resolution protein structure than crystallization with (S)-2-methyl-2, 4-pentanediol. The results suggest that chiral interactions with chiral additives are important in protein crystal formation. Chiral control of crystallization has ample precedent in the small-molecule world, but relatively little is known about the role of chirality in protein crystallization. In this study, lysozyme was crystallized in the presence of the chiral additive 2-methyl-2, 4-pentanediol (MPD) separately using the R and S enantiomers as well as with a racemic RS mixture. Crystals grown with (R)-MPD had the most order andmore » produced the highest resolution protein structures. This result is consistent with the observation that in the crystals grown with (R)-MPD and (RS)-MPD the crystal contacts are made by (R)-MPD, demonstrating that there is preferential interaction between lysozyme and this enantiomer. These findings suggest that chiral interactions are important in protein crystallization.« less

Chirality of nanophotonic waveguide with embedded quantum emitter for unidirectional spin transfer

NASA Astrophysics Data System (ADS)

Coles, R. J.; Price, D. M.; Dixon, J. E.; Royall, B.; Clarke, E.; Kok, P.; Skolnick, M. S.; Fox, A. M.; Makhonin, M. N.

2016-03-01

Scalable quantum technologies may be achieved by faithful conversion between matter qubits and photonic qubits in integrated circuit geometries. Within this context, quantum dots possess well-defined spin states (matter qubits), which couple efficiently to photons. By embedding them in nanophotonic waveguides, they provide a promising platform for quantum technology implementations. In this paper, we demonstrate that the naturally occurring electromagnetic field chirality that arises in nanobeam waveguides leads to unidirectional photon emission from quantum dot spin states, with resultant in-plane transfer of matter-qubit information. The chiral behaviour occurs despite the non-chiral geometry and material of the waveguides. Using dot registration techniques, we achieve a quantum emitter deterministically positioned at a chiral point and realize spin-path conversion by design. We further show that the chiral phenomena are much more tolerant to dot position than in standard photonic crystal waveguides, exhibit spin-path readout up to 95+/-5% and have potential to serve as the basis of spin-logic and network implementations.

Direct optical detection of Weyl fermion chirality in a topological semimetal

NASA Astrophysics Data System (ADS)

Ma, Qiong; Xu, Su-Yang; Chan, Ching-Kit; Zhang, Cheng-Long; Chang, Guoqing; Lin, Yuxuan; Xie, Weiwei; Palacios, Tomás; Lin, Hsin; Jia, Shuang; Lee, Patrick A.; Jarillo-Herrero, Pablo; Gedik, Nuh

2017-09-01

A Weyl semimetal is a novel topological phase of matter, in which Weyl fermions arise as pseudo-magnetic monopoles in its momentum space. The chirality of the Weyl fermions, given by the sign of the monopole charge, is central to the Weyl physics, since it directly serves as the sign of the topological number and gives rise to exotic properties such as Fermi arcs and the chiral anomaly. Here, we directly detect the chirality of the Weyl fermions by measuring the photocurrent in response to circularly polarized mid-infrared light. The resulting photocurrent is determined by both the chirality of Weyl fermions and that of the photons. Our results pave the way for realizing a wide range of theoretical proposals for studying and controlling the Weyl fermions and their associated quantum anomalies by optical and electrical means. More broadly, the two chiralities, analogous to the two valleys in two-dimensional materials, lead to a new degree of freedom in a three-dimensional crystal with potential novel pathways to store and carry information.

Chirality of nanophotonic waveguide with embedded quantum emitter for unidirectional spin transfer

PubMed Central

Coles, R. J.; Price, D. M.; Dixon, J. E.; Royall, B.; Clarke, E.; Kok, P.; Skolnick, M. S.; Fox, A. M.; Makhonin, M. N.

2016-01-01

Scalable quantum technologies may be achieved by faithful conversion between matter qubits and photonic qubits in integrated circuit geometries. Within this context, quantum dots possess well-defined spin states (matter qubits), which couple efficiently to photons. By embedding them in nanophotonic waveguides, they provide a promising platform for quantum technology implementations. In this paper, we demonstrate that the naturally occurring electromagnetic field chirality that arises in nanobeam waveguides leads to unidirectional photon emission from quantum dot spin states, with resultant in-plane transfer of matter-qubit information. The chiral behaviour occurs despite the non-chiral geometry and material of the waveguides. Using dot registration techniques, we achieve a quantum emitter deterministically positioned at a chiral point and realize spin-path conversion by design. We further show that the chiral phenomena are much more tolerant to dot position than in standard photonic crystal waveguides, exhibit spin-path readout up to 95±5% and have potential to serve as the basis of spin-logic and network implementations. PMID:27029961

Chirality of nanophotonic waveguide with embedded quantum emitter for unidirectional spin transfer.

PubMed

Coles, R J; Price, D M; Dixon, J E; Royall, B; Clarke, E; Kok, P; Skolnick, M S; Fox, A M; Makhonin, M N

2016-03-31

Scalable quantum technologies may be achieved by faithful conversion between matter qubits and photonic qubits in integrated circuit geometries. Within this context, quantum dots possess well-defined spin states (matter qubits), which couple efficiently to photons. By embedding them in nanophotonic waveguides, they provide a promising platform for quantum technology implementations. In this paper, we demonstrate that the naturally occurring electromagnetic field chirality that arises in nanobeam waveguides leads to unidirectional photon emission from quantum dot spin states, with resultant in-plane transfer of matter-qubit information. The chiral behaviour occurs despite the non-chiral geometry and material of the waveguides. Using dot registration techniques, we achieve a quantum emitter deterministically positioned at a chiral point and realize spin-path conversion by design. We further show that the chiral phenomena are much more tolerant to dot position than in standard photonic crystal waveguides, exhibit spin-path readout up to 95±5% and have potential to serve as the basis of spin-logic and network implementations.

Molecular dynamics simulation and NMR investigation of the association of the β-blockers atenolol and propranolol with a chiral molecular micelle

NASA Astrophysics Data System (ADS)

Morris, Kevin F.; Billiot, Eugene J.; Billiot, Fereshteh H.; Hoffman, Charlene B.; Gladis, Ashley A.; Lipkowitz, Kenny B.; Southerland, William M.; Fang, Yayin

2015-08-01

Molecular dynamics simulations and NMR spectroscopy were used to compare the binding of two β-blocker drugs to the chiral molecular micelle poly-(sodium undecyl-(L)-leucine-valine). The molecular micelle is used as a chiral selector in capillary electrophoresis. This study is part of a larger effort to understand the mechanism of chiral recognition in capillary electrophoresis by characterizing the molecular micelle binding of chiral compounds with different geometries and charges. Propranolol and atenolol were chosen because their structures are similar, but their chiral interactions with the molecular micelle are different. Molecular dynamics simulations showed both propranolol enantiomers inserted their aromatic rings into the molecular micelle core and that (S)-propranolol associated more strongly with the molecular micelle than (R)-propranolol. This difference was attributed to stronger molecular micelle hydrogen bonding interactions experienced by (S)-propranolol. Atenolol enantiomers were found to bind near the molecular micelle surface and to have similar molecular micelle binding free energies.

Structural insights into two inorganic-organic hybrids based on chiral amino acids and polyoxomolybdates

NASA Astrophysics Data System (ADS)

Arefian, Mina; Mirzaei, Masoud; Eshtiagh-Hosseini, Hossein

2018-03-01

A new chiral inorganic-organic hybrid with the formula (L-His)2(H7CoMo6O24)·6H2O (1), based on natural amino acid and Anderson type polyoxomolybdate was synthesized through mild condition. The chiral L-histidine molecules induced chirality to the whole structure through various types of strong and unconventional hydrogen bond (HB) interactions (CH⋯O, NH⋯O and CH···π interactions), as well as bifurcated hydrogen bonds (BHBs) between L-histidine amino acid, hexamer water cluster molecules, and H7CoMo6O24·xH2O. Following, important non-covalent CH⋯O interactions is investigated in another chiral inorganic-organic hybrid structure, (L-Pro)3(PMo12O40).4.5H2O (2), in detail. The CH⋯O hydrogen bonds lead to a chiral network similar to the DNA strands affording a promising candidate to bio-inorganic studies.

Mechanisms for the inversion of chirality: global reaction route mapping of stereochemical pathways in a probable chiral extraterrestrial molecule, 2-aminopropionitrile.

PubMed

Kaur, Ramanpreet; Vikas

2015-02-21

2-Aminopropionitrile (APN), a probable candidate as a chiral astrophysical molecule, is a precursor to amino-acid alanine. Stereochemical pathways in 2-APN are explored using Global Reaction Route Mapping (GRRM) method employing high-level quantum-mechanical computations. Besides predicting the conventional mechanism for chiral inversion that proceeds through an achiral intermediate, a counterintuitive flipping mechanism is revealed for 2-APN through chiral intermediates explored using the GRRM. The feasibility of the proposed stereochemical pathways, in terms of the Gibbs free-energy change, is analyzed at the temperature conditions akin to the interstellar medium. Notably, the stereoinversion in 2-APN is observed to be more feasible than the dissociation of 2-APN and intermediates involved along the stereochemical pathways, and the flipping barrier is observed to be as low as 3.68 kJ/mol along one of the pathways. The pathways proposed for the inversion of chirality in 2-APN may provide significant insight into the extraterrestrial origin of life.

Broad-Bandwidth Chiral Sum Frequency Generation Spectroscopy for Probing the Kinetics of Proteins at Interfaces

PubMed Central

2016-01-01

The kinetics of proteins at interfaces plays an important role in biological functions and inspires solutions to fundamental problems in biomedical sciences and engineering. Nonetheless, due to the lack of surface-specific and structural-sensitive biophysical techniques, it still remains challenging to probe protein kinetics in situ and in real time without the use of spectroscopic labels at interfaces. Broad-bandwidth chiral sum frequency generation (SFG) spectroscopy has been recently developed for protein kinetic studies at interfaces by tracking the chiral vibrational signals of proteins. In this article, we review our recent progress in kinetic studies of proteins at interfaces using broad-bandwidth chiral SFG spectroscopy. We illustrate the use of chiral SFG signals of protein side chains in the C–H stretch region to monitor self-assembly processes of proteins at interfaces. We also present the use of chiral SFG signals from the protein backbone in the N–H stretch region to probe the real-time kinetics of proton exchange between protein and water at interfaces. In addition, we demonstrate the applications of spectral features of chiral SFG that are typical of protein secondary structures in both the amide I and the N–H stretch regions for monitoring the kinetics of aggregation of amyloid proteins at membrane surfaces. These studies exhibit the power of broad-bandwidth chiral SFG to study protein kinetics at interfaces and the promise of this technique in research areas of surface science to address fundamental problems in biomedical and material sciences. PMID:26196215

Spontaneous Planar Chiral Symmetry Breaking in Cells

NASA Astrophysics Data System (ADS)

Hadidjojo, Jeremy; Lubensky, David

Recent progress in animal development has highlighted the central role played by planar cell polarity (PCP) in epithelial tissue morphogenesis. Through PCP, cells have the ability to collectively polarize in the plane of the epithelium by localizing morphogenetic proteins along a certain axis. This allows direction-dependent modulation of tissue mechanical properties that can translate into the formation of complex, non-rotationally invariant shapes. Recent experimental observations[1] show that cells, in addition to being planar-polarized, can also spontaneously develop planar chirality, perhaps in the effort of making yet more complex shapes that are reflection non-invariant. In this talk we will present our work in characterizing general mechanisms that can lead to spontaneous chiral symmetry breaking in cells. We decompose interfacial concentration of polarity proteins in a hexagonal cell packing into irreducible representations. We find that in the case of polar concentration distributions, a chiral state can only be reached from a secondary instability after the cells are polarized. However in the case of nematic distributions, we show that a finite-amplitude (subcritical, or ``first-order'') nematic transition can send the system from disorder directly to a chiral state. In addition, we find that perturbing the system by stretching the hexagonal packing enables direct (supercritical, or ``second-order'') chiral transition in the nematic case. Finally, we do a Landau expansion to study competition between stretch-induced chirality and the tendency towards a non-chiral state in packings that have retained the full 6-fold symmetry.

Homochiral drugs: a demanding tendency of the pharmaceutical industry.

PubMed

Núñez, María C; García-Rubiño, M Eugenia; Conejo-García, Ana; Cruz-López, Olga; Kimatrai, María; Gallo, Miguel A; Espinosa, Antonio; Campos, Joaquín M

2009-01-01

The issue of drug chirality is now a major theme in the design and development of new drugs, underpinned by a new understanding of the role of molecular recognition in many pharmacologically relevant events. In general, three methods are utilized for the production of a chiral drug: the chiral pool, separation of racemates, and asymmetric synthesis. Although the use of chiral drugs predates modern medicine, only since the 1980's has there been a significant increase in the development of chiral pharmaceutical drugs. An important commercial reason is that as patents on racemic drugs expire, pharmaceutical companies have the opportunity to extend patent coverage through development of the chiral switch enantiomers with desired bioactivity. Stimulated by the new policy statements issued by the regulatory agencies, the pharmaceutical industry has systematically begun to develop chiral drugs in enantiometrically enriched pure forms. This new trend has caused a tremendous change in the industrial small- and large-scale production to enantiomerically pure drugs, leading to the revisiting and updating of old technologies, and to the development of new methodologies of their large-scale preparation (as the use of stereoselective syntheses and biocatalyzed reactions). The final decision whether a given chiral drug will be marketed in an enantiomerically pure form, or as a racemic mixture of both enantiomers, will be made weighing all the medical, financial and social proficiencies of one or other form. The kinetic, pharmacological and toxicological properties of individual enantiomers need to be characterized, independently of a final decision.

Chiral stability of an extemporaneously prepared clopidogrel bisulfate oral suspension.

PubMed

Tynes, Clay R; Livingston, Brad; Patel, Hetesh; Arnold, John J

2014-01-01

The purpose of this study was to evaluate the chiral stability of clopidogrel bisulfate in an extemporaneously compounded oral suspension for a period of 60 days. A 5 mg/mL oral suspension of clopidogrel bisulfate was prepared from commercially available Plavix tablets. The clopidogrel suspension was then evenly divided between two light-resistant prescription bottles and stored either under refrigeration (4°C) or at room temperature (25°C). Samples were drawn from the stored suspensions immediately after preparation and on days 7, 14, 28, and 60. Samples were subsequently analyzed at each time point by high-performance liquid chromatography using a reversed-phase column, with chemical stability defined as the retention of at least 90% of the initial intact clopidogrel concentration measured. To determine the chiral stability of the suspension, samples were also analyzed by high-performance liquid chromatography using a chiral column to investigate possible enantiomeric inversion. Chiral stability was defined as the retention of at least 90% of the initial concentration of the suspension as the S-enantiomer, the active moiety of Plavix. Regardless of storage conditions, the oral suspension of clopidogrel retained at least 98% of the active S-enantiomer for 60 days after preparation. Compared with the clopidogrel suspension stored in the refrigerator, more chiral inversion was noted in the clopidogrel suspension stored at room temperature. Our investigation of chiral stability indicates that a 5 mg/mL clopidogrel oral suspension stored under refrigeration and at room temperature maintains chiral stability as the active S-enantiomer.

ENANTIOMERIC COMPOSITION OF CHIRAL PESTICIDES IN HUMAN ADIPOSE TISSUE AND BREAST MILK

EPA Science Inventory

Examining the enantiomeric patterns of pesticides can provide a sensitive indicator of biological degradation. However, little work has been done to date on chiral pesticides in the human body. This study looks at the enantiomeric patterns of chiral pesticides and their chira...

CHIRAL CHEMISTRY OF PESTICIDES IN THE ENVIRONMENT WITH IMPLICATIONS FOR POLLUTION PREVENTION

EPA Science Inventory

Upwards of 25% of pesticides and other toxic pollutants are chiral; that is, they exist as two mirror image species called enantiomers. The enantiomers of a chiral compound have identical physical and abiotic chemical properties, but differ in biological properties such as microb...

ANALYSIS OF CHIRAL PESTICIDES AND POLYCHLORINATED BIPHENYL CONGENERS IN ENVIRONMENTAL SAMPLES

EPA Science Inventory

Over 25 % of pesticides and other toxic organic pollutants are chiral, as are 19 of the 209 polychlorinated biphenyl (PCB) congeners; that is, they exist as two mirror image species called enantiomers (PCB enantiomers are called atropisomers). The enantiomers of a chiral compound...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koch, Volker

These lectures are an attempt to a pedagogical introduction into the elementary concepts of chiral symmetry in nuclear physics. We will also discuss some effective chiral models such as the linear and nonlinear sigma model as well as the essential ideas of chiral perturbation theory. We will present some applications to the physics of ultrarelativistic heavy ion collisionsd.

CHIRAL METHODS AND ANALYSIS OF PCB 95 AND CIS -PERMETHRIN IN ENVIRONMENTAL SAMPLES FROM THE CTEPP STUDY

EPA Science Inventory

The creation of chiral chromatography techniques significantly advanced the development of methods for the analysis of individual enantiomers of chiral compounds. These techniques are being employed at the US EPA for human exposure and ecological research studies with indoor samp...

Optically Reconfigurable Chiral Microspheres of Self-Organized Helical Superstructures with Handedness Inversion.

PubMed

Wang, Ling; Chen, Dong; Gutierrez-Cuevas, Karla G; Bisoyi, Hari Krishna; Fan, Jing; Zola, Rafael S; Li, Guoqiang; Urbas, Augustine M; Bunning, Timothy J; Weitz, David A; Li, Quan

2017-01-01

Optically reconfigurable monodisperse chiral microspheres of self-organized helical superstructures with dynamic chirality were fabricated via a capillary-based microfluidic technique. Light-driven handedness-invertible transformations between different configurations of microspheres were vividly observed and optically tunable RGB photonic cross-communications among the microspheres were demonstrated.

X-ray circular dichroism signals: a unique probe of local molecular chirality

DOE PAGES

Zhang, Yu; Rouxel, Jeremy R.; Autschbach, Jochen; ...

2017-06-26

Core-resonant circular dichroism (CD) signals are induced by molecular chirality and vanish for achiral molecules and racemic mixtures. The highly localized nature of core excitations makes them ideal probes of local chirality within molecules. Simulations of the circular dichroism spectra of several molecular families illustrate how these signals vary with the electronic coupling to substitution groups, the distance between the X-ray chromophore and the chiral center, geometry, and chemical structure. As a result, clear insight into the molecular structure is obtained through analysis of the X-ray CD spectra.

Declining availability of outdoor skating in Canada

NASA Astrophysics Data System (ADS)

Brammer, Jeremy R.; Samson, Jason; Humphries, Murray M.

2015-01-01

We find a mixed chirality $d$-wave superconducting state in the coexistence region between antiferromagnetism and interaction-driven superconductivity in lightly doped honeycomb materials. This state has a topological chiral $d+id$-wave symmetry in one Dirac valley but $d-id$-wave symmetry in the other valley and hosts two counter-propagating edge states, protected in the absence of intervalley scattering. A first-order topological phase transition, with no bulk gap closing, separates the chiral $d$-wave state at small magnetic moments from the mixed chirality $d$-wave phase.

Process for the preparation of protected dihydroxypropyl trialkylammonium salts and derivatives thereof

DOEpatents

Hollingsworth, Rawle I.; Wang, Guijun

2000-01-01

A process for the preparation of protected dihydroxypropyl trialkylammonium salts, particularly in chiral form is described. In particular, a process for the preparation of (2,2-dimethyl-1,3-dioxolan-4-ylmethyl)trialkylammonium salts, particularly in chiral form is described. Furthermore, a process is described wherein the (2,2-dimethyl-1,3-dioxolan-4ylmethyl)trialkylammonium salts is a 2,2-dimethyl-1,3-dioxolan-4-ylmethyl trimethylammonium salt, preferably in chiral form. The protected dihydroxypropyl trialkylammonium salts lead to L-carnitine (9) when in chiral form (5).

Molecular recognition in chiral smectic liquid crystals: the effect of core-core interactions and chirality transfer on polar order.

PubMed

Lemieux, Robert P

2007-12-01

This critical review focuses on the induction of polar order in smectic liquid crystal phases by dopants with axially chiral cores, and should be of interest to all practitioners of supramolecular chemistry. The variations in polarization power of these dopants with the core structure of the liquid crystal hosts is a manifestation of molecular recognition that reflects the nanosegregation of aromatic cores from paraffinic side-chains in smectic phases, and the collective effect of core-core interactions that enable the propagation of chiral perturbations.

Gold(I)-Catalysed Hydroarylation of 1,3-Disubstituted Allenes with Efficient Axial-to-Point Chirality Transfer.

PubMed

Sutherland, Daniel R; Kinsman, Luke; Angiolini, Stuart M; Rosair, Georgina M; Lee, Ai-Lan

2018-05-11

Hydroarylation of enantioenriched 1,3-disubstituted allenes has the potential to proceed with axial-to-point chirality transfer to yield enantioenriched allylated (hetero)aryl compounds. However, the gold-catalysed intermolecular reaction was previously reported to occur with no chirality transfer owing to competing allene racemisation. Herein, we describe the development of the first intermolecular hydroarylations of allenes to proceed with efficient chirality transfer and summarise some of the key criteria for achieving high regio- and stereoselectivity. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Separation of piracetam derivatives on polysaccharide-based chiral stationary phases.

PubMed

Kažoka, H; Koliškina, O; Veinberg, G; Vorona, M

2013-03-15

High-performance liquid chromatography was used for the enantiomeric separation of two chiral piracetam derivatives. The suitability of six commercially available polysaccharide-based chiral stationary phases (CSPs) under normal phase mode for direct enantioseparation has been investigated. The influence of the CSPs as well the nature and content of an alcoholic modifier in the mobile phase on separation and elution order was studied. It was established that CSP Lux Amylose-2 shows high chiral recognition ability towards 4-phenylsubstituted piracetam derivatives. Copyright © 2013 Elsevier B.V. All rights reserved.

Dichlorido[(S,R(S))-1-diphenylphosphino-2-(ethylsulfanylmethyl)ferrocene]palladium(II).

PubMed

Diab, Lisa; Daran, Jean-Claude; Gouygou, Maryse; Manoury, Eric; Urrutigoïty, Martine

2007-12-01

The reaction of enantiomerically pure planar chiral ferrocene phosphine thioether with bis(acetonitrile)dichloridopalladium yields the title square-planar mononuclear palladium complex as an enantiomerically pure single diastereoisomer, [PdFe(C5H5)(C20H20PS)Cl2]. The planar chirality of the ligand is retained in the complex and fully controls the central chirality on the S atom. The absolute configuration, viz. S for the planar chirality and R for the S atom, is unequivocally determined by refinement of the Flack parameter.

X-ray circular dichroism signals: a unique probe of local molecular chirality

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yu; Rouxel, Jeremy R.; Autschbach, Jochen

Core-resonant circular dichroism (CD) signals are induced by molecular chirality and vanish for achiral molecules and racemic mixtures. The highly localized nature of core excitations makes them ideal probes of local chirality within molecules. Simulations of the circular dichroism spectra of several molecular families illustrate how these signals vary with the electronic coupling to substitution groups, the distance between the X-ray chromophore and the chiral center, geometry, and chemical structure. As a result, clear insight into the molecular structure is obtained through analysis of the X-ray CD spectra.

Uncertainty analysis of 208Pb neutron skin predictions with chiral interactions

DOE PAGES

Sammarruca, Francesca

2015-09-14

Here, we report predictions for the neutron skin in 208Pb using chiral two- and three-body interactions at increasing orders of chiral effective field theory and varying resolution scales. Closely related quantities, such as the slope of the symmetry energy, are also discussed. As a result, the sensitivity of the skin to just pure neutron matter pressure when going from order 2 to order 4 of chiral effective theory is singled out in a set of calculations that employ an empirical equation of state for symmetric nuclear matter.

Drag suppression in anomalous chiral media

DOE PAGES

Sadofyev, Andrey V.; Yin, Yi

2016-06-01

We study a heavy impurity moving longitudinal with the direction of an external magnetic field in an anomalous chiral medium. Such system would carry a non-dissipative current of chiral magnetic effect associated with the anomaly. We show, by generalizing Landau's criterion for super fluidity, that the "anomalous component" which gives rise to the anomalous transport will not contribute to the drag experienced by an impurity. We argue on a very general basis that those systems with a strong magnetic field would exhibit an interesting transport phenomenon$-$the motion of the heavy impurity is frictionless, in analogy to the case of amore » super fluid. Finally, we demonstrate and confirm our general results with two complementary examples: weakly coupled chiral fermion gases and strongly interacting chiral liquids.« less

Stereoisomers Separation

NASA Astrophysics Data System (ADS)

Wieczorek, Piotr

The use of capillary electrophoresis for enantiomer separation and optical purity determination is presented. The contents start with basic information about the nature of stereoizomers and the mechanism of enantioseparation using capillary electrophoresis techniques. The molecules to be separated show identical chemical structure and electrochemical behavior. Therefore, the chiral recognition of enantiomers is possible only by bonding to chiral selector and the separation based on very small differences in complexation energies of diastereomer complexes formed. This method is useful for this purpose due to the fact that different compounds can be used as chiral selectors. The mostly used chiral selectors like cyclodextrins, crown ethers, chiral surfactants, macrocyclic antibiotics, transition metal complexes, natural, and synthetic polymers and their application for this purpose is also discussed. Finally, examples of practical applications of electromigration techniques for enantiomers separation and determination are presented.

Matching Pion-Nucleon Roy-Steiner Equations to Chiral Perturbation Theory.

PubMed

Hoferichter, Martin; Ruiz de Elvira, Jacobo; Kubis, Bastian; Meissner, Ulf-G

2015-11-06

We match the results for the subthreshold parameters of pion-nucleon scattering obtained from a solution of Roy-Steiner equations to chiral perturbation theory up to next-to-next-to-next-to-leading order, to extract the pertinent low-energy constants including a comprehensive analysis of systematic uncertainties and correlations. We study the convergence of the chiral series by investigating the chiral expansion of threshold parameters up to the same order and discuss the role of the Δ(1232) resonance in this context. Results for the low-energy constants are also presented in the counting scheme usually applied in chiral nuclear effective field theory, where they serve as crucial input to determine the long-range part of the nucleon-nucleon potential as well as three-nucleon forces.

Organocatalytic atroposelective synthesis of axially chiral styrenes

NASA Astrophysics Data System (ADS)

Zheng, Sheng-Cai; Wu, San; Zhou, Qinghai; Chung, Lung Wa; Ye, Liu; Tan, Bin

2017-05-01

Axially chiral compounds are widespread in biologically active compounds and are useful chiral ligands or organocatalysts in asymmetric catalysis. It is well-known that styrenes are one of the most abundant and principal feedstocks and thus represent excellent prospective building blocks for chemical synthesis. Driven by the development of atroposelective synthesis of axially chiral styrene derivatives, we discovered herein the asymmetric organocatalytic approach via direct Michael addition reaction of substituted diones/ketone esters/malononitrile to alkynals. The axially chiral styrene compounds were produced with good chemical yields, enantioselectivities and almost complete E/Z-selectivities through a secondary amine-catalysed iminium activation strategy under mild conditions. Such structural motifs are important precursors for further transformations into biologically active compounds and synthetic useful intermediates and may have potential applications in asymmetric synthesis as olefin ligands or organocatalysts.

Matching Pion-Nucleon Roy-Steiner Equations to Chiral Perturbation Theory

NASA Astrophysics Data System (ADS)

Hoferichter, Martin; Ruiz de Elvira, Jacobo; Kubis, Bastian; Meißner, Ulf-G.

2015-11-01

We match the results for the subthreshold parameters of pion-nucleon scattering obtained from a solution of Roy-Steiner equations to chiral perturbation theory up to next-to-next-to-next-to-leading order, to extract the pertinent low-energy constants including a comprehensive analysis of systematic uncertainties and correlations. We study the convergence of the chiral series by investigating the chiral expansion of threshold parameters up to the same order and discuss the role of the Δ (1232 ) resonance in this context. Results for the low-energy constants are also presented in the counting scheme usually applied in chiral nuclear effective field theory, where they serve as crucial input to determine the long-range part of the nucleon-nucleon potential as well as three-nucleon forces.

Chirality, Metallicity, and Transition Dependent Asymmetries in Resonance Raman Excitation Profiles of Chirality-Enriched Carbon Nanotubes

NASA Astrophysics Data System (ADS)

Doorn, Stephen; Duque, Juan; Telg, Hagen; Haroz, Erik; Tu, Xiaomin; Zheng, Ming

2014-03-01

Access to carbon nanotube samples enriched in single chiralities allows the observation of new photophysical behaviors obscured or difficult to demonstrate in mixed-chirality ensembles. Recent examples include the observation of strongly asymmetric G-band excitation profiles resulting from non-Condon effects1 and the unambiguous demonstration of Raman interference effects.2 We present here our most recent results demonstrating the generality of the non-Condon behavior to include metallic species (specifically several armchair chiralities). Additionally, the Eii dependence in non-Condon behavior with excitations from E11 thru E44 for both RBM and G modes will be discussed. 1. J.G. Duque, et. al., ACS Nano, 5, 5233 (2011). 2. J.G. Duque, et. al., Phys. Rev. Lett. 108, 117404 (2012).

Active chiral control of GHz acoustic whispering-gallery modes

NASA Astrophysics Data System (ADS)

Mezil, Sylvain; Fujita, Kentaro; Otsuka, Paul H.; Tomoda, Motonobu; Clark, Matt; Wright, Oliver B.; Matsuda, Osamu

2017-10-01

We selectively generate chiral surface-acoustic whispering-gallery modes in the gigahertz range on a microscopic disk by means of an ultrafast time-domain technique incorporating a spatial light modulator. Active chiral control is achieved by making use of an optical pump spatial profile in the form of a semicircular arc, positioned on the sample to break the symmetry of clockwise- and counterclockwise-propagating modes. Spatiotemporal Fourier transforms of the interferometrically monitored two-dimensional acoustic fields measured to micron resolution allow individual chiral modes and their azimuthal mode order, both positive and negative, to be distinguished. In particular, for modes with 15-fold rotational symmetry, we demonstrate ultrafast chiral control of surface acoustic waves in a micro-acoustic system with picosecond temporal resolution. Applications include nondestructive testing and surface acoustic wave devices.

Synthesis and anti-H5N1 activity of chiral gossypol derivatives and its analogs implicated by a viral entry blocking mechanism.

PubMed

Yang, Jian; Chen, Gang; Li, Long Long; Pan, Wei; Zhang, Fang; Yang, Jingxiang; Wu, Shuwen; Tien, Po

2013-05-01

A series of chiral gossypol derivatives and its analogs were synthesized and tested in vitro for their anti-H5N1 activity. Interestingly, (+)-gossypol derivatives and its analogs were more active against H5N1 than the corresponding (-)-gossypol derivatives and its analogs. Through a simple chemical modification with amino acids, less active chiral gossypol could be converted into more active derivatives, and most of chiral gossypol derivatives were more potent against H5N1 than 1-adamantylamine. With regard to the mechanism of action, chiral gossypol derivatives and its analogs might impair the virus entry step of cell infection, likely targeting to HA2 protein. Copyright © 2013 Elsevier Ltd. All rights reserved.

Light-front representation of chiral dynamics in peripheral transverse densities

DOE PAGES

Granados, Carlos G.; Weiss, Christian

2015-07-31

The nucleon's electromagnetic form factors are expressed in terms of the transverse densities of charge and magnetization at fixed light-front time. At peripheral transverse distances b = O(M_pi^{-1}) the densities are governed by chiral dynamics and can be calculated model-independently using chiral effective field theory (EFT). We represent the leading-order chiral EFT results for the peripheral transverse densities as overlap integrals of chiral light-front wave functions, describing the transition of the initial nucleon to soft pion-nucleon intermediate states and back. The new representation (a) explains the parametric order of the peripheral transverse densities; (b) establishes an inequality between the spin-independentmore » and -dependent densities; (c) exposes the role of pion orbital angular momentum in chiral dynamics; (d) reveals a large left-right asymmetry of the current in a transversely polarized nucleon and suggests a simple interpretation. The light-front representation enables a first-quantized, quantum-mechanical view of chiral dynamics that is fully relativistic and exactly equivalent to the second-quantized, field-theoretical formulation. It relates the charge and magnetization densities measured in low-energy elastic scattering to the generalized parton distributions probed in peripheral high-energy scattering processes. The method can be applied to nucleon form factors of other operators, e.g. the energy-momentum tensor.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fu, Li; Zhang, Yun; Wei, Zhehao

We report in this work detailed measurements on the chiral and achiral sum-frequency vibrational spectra in the C-H stretching vibration region (2800-3050cm-1) of the air/liquid interfaces of R-limonene and S-limonene, using the recently developed high-resolution broadband sum-frequency generation vibrational spectroscopy (HR-BB-SFG-VS). The achiral SFG spectra of R-limonene and S-limonene, as well as the equal amount (50/50) racemic mixture show that the enantiomers are with the same interfacial orientations. The interference chiral SFG spectra of the limonene enantiomers exhibit spectral signature from chiral response of the Cα-H stretching mode, and spectral signature from prochiral response of the CH2 asymmetric stretching mode,more » respectively. The chiral spectral feature of the Cα-H stretching mode changes sign from R-limonene to S-limonene, and disappears for the 50/50 racemic mixture. While the prochiral spectral feature of the CH2 asymmetric stretching mode is the same for R-limonene and S-limonene, and also surprisingly remains the same for the 50/50 racemic mixture. These results provided detail information in understanding the structure and chirality of molecular interfaces, and demonstrated the sensitivity and potential of SFG-VS as unique spectroscopic tool for chirality characterization and chiral recognition at the molecular interface.« less

Enantioselective Effects of Chiral Pesticides on their Primary Targets and Secondary Targets.

PubMed

Yang, Ye; Zhang, Jianyun; Yao, Yijun

2017-01-01

Enantioselectivity has been well recognized in the environmental fate and effects of chiral pesticides. Enantiospecific action of the optical enantiomers on the biological molecules establishes the mechanistic basis for the enantioselective toxicity of chiral pesticides to both target and non-target organisms. We undertook a structured search of bibliographic databases for research literature concerning the enantioselective effects of chiral pesticides, including insecticides, herbicides and fungicides, on biomolecules in various species by using some key words. The results of the relevant literatures were reviewed in the text and summarized in tables. Pesticides generally exert their activity on the target organisms via disrupting the primary target biomolecules. In non-target species, effects of pesticides on the secondary targets distinguished from the primary ones make great contribution to their toxicity. Recent investigations have provided convincing evidence of enantioselective toxicity of chiral pesticides to both target and non-target species which is recognized to result from their enantiospecific action on the primary or secondary targets in organisms. This review confirms that chiral pesticides have enantiospecific effects on both primary and secondary target biomolecules in organisms. Future studies regarding toxicological effects of chiral pesticides should focus on the relationship between the enantiomeric difference in the compound-biomolecules interaction and the enantioselectivity in their toxicity.

Four-dimensional analysis by high-speed holographic imaging reveals a chiral memory of sperm flagella.

PubMed

Muschol, Michael; Wenders, Caroline; Wennemuth, Gunther

2018-01-01

Here high-speed Digital Holographic Microscopy (DHM) records sperm flagellar waveforms and swimming paths in 4 dimensions (X, Z, and t). We find flagellar excursions into the Z-plane nearly as large as the envelope of the flagellar waveform projected onto the XY-plane. These Z-plane excursions travel as waves down the flagellum each beat cycle. DHM also tracks the heads of free-swimming sperm and the dynamics and chirality of rolling of sperm around their long axis. We find that mouse sperm roll CW at the maximum positive Z-plane excursion of the head, then roll CCW at the subsequent maximum negative Z-plane excursion. This alternating chirality of rolling indicates sperm have a chiral memory. Procrustes alignments of path trajectories for sequences of roll-counterroll cycles show that path chirality is always CW for the cells analyzed in this study. Human and bull sperm lack distinguishable left and right surfaces, but DHM still indicates coordination of Z-plane excursions and rolling events. We propose that sperm have a chiral memory that resides in a hypothetical elastic linkage within the flagellar machinery, which stores some of the torque required for a CW or CCW roll to reuse in the following counter-roll. Separate mechanisms control path chirality.

One-step hydrothermal synthesis of chiral carbon dots and their effects on mung bean plant growth.

PubMed

Zhang, Mengling; Hu, Lulu; Wang, Huibo; Song, Yuxiang; Liu, Yang; Li, Hao; Shao, Mingwang; Huang, Hui; Kang, Zhenhui

2018-06-27

Chiral compounds/materials have important effects on the growth of plants. Chiral carbon dots (CDs), as an emerging chiral carbon nanomaterial, have great potential in bio-application and bio-nanotechnology. Herein, we report a hydrothermal method to synthesize chiral CDs from cysteine (cys) and citric acid. These chiral CDs were further demonstrated to have systemic effects on the growth of mung bean plants, in which case both l- and d-CDs can promote the growth of the root in mung bean plants, stem length of mung bean sprouts and water absorption of bean seeds. The elongation of mung bean sprouts presented an increasing trend with the treatment of chiral CDs of increasing concentration (below 500 μg mL-1). Furthermore, in the optimal concentration (100 μg mL-1), the l-CDs can improve root vigor and the activity of the Rubisco enzyme of bean sprouts by 8.4% and 20.5%, while the d-CDs increased by 28.9% and 67.5%. Due to more superior properties in improving root vigor and the activity of the Rubisco enzyme of mung bean sprouts, d-CDs are able to enhance photosynthesis better and accumulate more carbohydrate in mung bean plants.

On exact correlation functions of chiral ring operators in 2 d N=(2, 2) SCFTs via localization

NASA Astrophysics Data System (ADS)

Chen, Jin

2018-03-01

We study the extremal correlation functions of (twisted) chiral ring operators via superlocalization in N=(2, 2) superconformal field theories (SCFTs) with central charge c ≥ 3, especially for SCFTs with Calabi-Yau geometric phases. We extend the method in arXiv: 1602.05971 with mild modifications, so that it is applicable to disentangle operators mixing on S 2 in nilpotent (twisted) chiral rings of 2 d SCFTs. With the extended algorithm and technique of localization, we compute exactly the extremal correlators in 2 d N=(2, 2) (twisted) chiral rings as non-holomorphic functions of marginal parameters of the theories. Especially in the context of Calabi-Yau geometries, we give an explicit geometric interpretation to our algorithm as the Griffiths transversality with projection on the Hodge bundle over Calabi-Yau complex moduli. We also apply the method to compute extremal correlators in Kähler moduli, or say twisted chiral rings, of several interesting Calabi-Yau manifolds. In the case of complete intersections in toric varieties, we provide an alternative formalism for extremal correlators via localization onto Higgs branch. In addition, as a spinoff we find that, from the extremal correlators of the top element in twisted chiral rings, one can extract chiral correlators in A-twisted topological theories.

Structure elucidation and absolute stereochemistry of isomeric monoterpene chromane esters.

PubMed

Batista, João M; Batista, Andrea N L; Mota, Jonas S; Cass, Quezia B; Kato, Massuo J; Bolzani, Vanderlan S; Freedman, Teresa B; López, Silvia N; Furlan, Maysa; Nafie, Laurence A

2011-04-15

Six novel monoterpene chromane esters were isolated from the aerial parts of Peperomia obtusifolia (Piperaceae) using chiral chromatography. This is the first time that chiral chromane esters of this kind, ones with a tethered chiral terpene, have been isolated in nature. Due to their structural features, it is not currently possible to assess directly their absolute stereochemistry using any of the standard classical approaches, such as X-ray crystallography, NMR, optical rotation, or electronic circular dichroism (ECD). Herein we report the absolute configuration of these molecules, involving four chiral centers, using vibrational circular dichroism (VCD) and density functional theory (DFT) (B3LYP/6-31G*) calculations. This work further reinforces the capability of VCD to determine unambiguously the absolute configuration of structurally complex molecules in solution, without crystallization or derivatization, and demonstrates the sensitivity of VCD to specify the absolute configuration for just one among a number of chiral centers. We also demonstrate the sufficiency of using the so-called inexpensive basis set 6-31G* compared to the triple-ζ basis set TZVP for absolute configuration analysis of larger molecules using VCD. Overall, this work extends our knowledge of secondary metabolites in plants and provides a straightforward way to determine the absolute configuration of complex natural products involving a chiral parent moiety combined with a chiral terpene adduct.

Chirality of Single-Handed Twisted Titania Tubular Nanoribbons Prepared Through Sol-gel Transcription.

PubMed

Wang, Sibing; Zhang, Chuanyong; Li, Yi; Li, Baozong; Yang, Yonggang

2015-08-01

Single-handed twisted titania tubular nanoribbons were prepared through sol-gel transcription using a pair of enantiomers. Handedness was controlled by that of the template. The obtained samples were characterized using field-emission electron microscopy, transmission electron microscopy, diffuse reflectance circular dichroism (DRCD), and X-ray diffraction. The DRCD spectra indicated that the titania nanotubes exhibit optical activity. Although the tubular structure was destroyed after being calcined at 700 °C for 2.0 h, DRCD signals were still identified. However, the DRCD signals disappeared after being calcined at 1000 °C for 2.0 h. The optical activity of titania was proposed to be due to chiral defects. Previous results showed that straight titania tubes could be used as asymmetric autocatalysts, indicating that titania exhibit chirality at the angstrom level. Herein, it was found that they also exhibit DRCD signals, indicating that there are no obvious relationships between morphology at the nano level and chirality at the angstrom level. The nanotube chirality should originate from the chiral defects on the nanotube inner surface. The Fourier transform infrared spectra indicated that the chirality of the titania was transferred from the gelators through the hydrogen bonding between N-H and Ti-OH. © 2015 Wiley Periodicals, Inc.

Fabrication of Supramolecular Chirality from Achiral Molecules at the Liquid/Liquid Interface Studied by Second Harmonic Generation.

PubMed

Lin, Lu; Zhang, Zhen; Guo, Yuan; Liu, Minghua

2018-01-09

We present the investigation into the supramolecular chirality of 5-octadecyloxy-2-(2-pyridylazo)phenol (PARC18) at water/1,2-dichloroethane interface by second harmonic generation (SHG). We observe that PARC18 molecules form supramolecular chirality through self-assembly at the liquid/liquid interface although they are achiral molecules. The bulk concentration of PARC18 in the organic phase has profound effects on the supramolecular chirality. By increasing bulk concentration, the enantiomeric excess at the interface first grows and then decreases until it eventually vanishes. Further analysis reveals that the enantiomeric excess is determined by the twist angle of PARC18 molecules at the interface rather than their orientational angle. At lower and higher bulk concentrations, the average twist angle of PARC18 molecules approaches zero, and the assemblies are achiral; whereas at medium bulk concentrations, the average twist angle is nonzero, so that the assemblies show supramolecular chirality. We also estimate the coverage of PARC18 molecules at the interface versus the bulk concentration and fit it to Langmuir adsorption model. The result indicates that PARC18 assemblies show strongest supramolecular chirality in a half-full monolayer. These findings highlight the opportunities for precise control of supramolecular chirality at liquid/liquid interfaces by manipulating the bulk concentration.

Circularly Polarized Light with Sense and Wavelengths To Regulate Azobenzene Supramolecular Chirality in Optofluidic Medium.

PubMed

Wang, Laibing; Yin, Lu; Zhang, Wei; Zhu, Xiulin; Fujiki, Michiya

2017-09-20

Circularly polarized light (CPL) as a massless physical force causes absolute asymmetric photosynthesis, photodestruction, and photoresolution. CPL handedness has long been believed to be the determining factor in the resulting product's chirality. However, product chirality as a function of the CPL handedness, irradiation wavelength, and irradiation time has not yet been studied systematically. Herein, we investigate this topic using achiral polymethacrylate carrying achiral azobenzene as micrometer-size aggregates in an optofluidic medium with a tuned refractive index. Azobenzene chirality with a high degree of dissymmetry ratio (±1.3 × 10 -2 at 313 nm) was generated, inverted, and switched in multiple cycles by irradiation with monochromatic incoherent CPL (313, 365, 405, and 436 nm) for 20 s using a weak incoherent light source (≈ 30 μW·cm -2 ). Moreover, the optical activity was retained for over 1 week in the dark. Photoinduced chirality was swapped by the irradiating wavelength, regardless of whether the CPL sense was the same. This scenario is similar to the so-called Cotton effect, which was first described in 1895. The tandem choice of both CPL sense and its wavelength was crucial for azobenzene chirality. Our experimental proof and theoretical simulation should provide new insight into the chirality of CPL-controlled molecules, supramolecules, and polymers.

Chiral analysis of UV nonabsorbing compounds by capillary electrophoresis using macrocyclic antibiotics: 1. Separation of aspartic and glutamic acid enantiomers.

PubMed

Bednar, P; Aturki, Z; Stransky, Z; Fanali, S

2001-07-01

Glycopeptide antibiotics, namely vancomycin or teicoplanin, were evaluated in capillary electrophoresis for the analysis of UV nonabsorbing compounds such as aspartic and glutamic acid enantiomers. Electrophoretic runs were performed in laboratory-made polyacrylamide-coated capillaries using the partial filling-counter current method in order to avoid the presence on the detector path of the absorbing chiral selector. The background electrolyte consisted of an aqueous or aqueous-organic buffer in the pH range of 4.5-6.5 of sorbic acid/histidine and the appropriate concentration of chiral selector. Several experimental parameters such as antibiotic concentration and type, buffer pH, organic modifier, type and concentration of absorbing co-ion (for the indirect UV detection) were studied in order to find the optimum conditions for the chiral resolution of the two underivatized amino acids in their enantiomers. Among the two investigated chiral selectors, vancomycin resulted to be the most useful chiral selector allowing relatively high chiral resolution of the studied compounds even at low concentration. The optimized method (10 mM sorbic acid/histidine, pH 5, and 10 mM of vancomycin) was used for the analysis of real samples such as teeth dentine and beer.

Paraxial propagation of the first-order chirped Airy vortex beams in a chiral medium.

PubMed

Xie, Jintao; Zhang, Jianbin; Ye, Junran; Liu, Haowei; Liang, Zhuoying; Long, Shangjie; Zhou, Kangzhu; Deng, Dongmei

2018-03-05

We introduce the propagation of the first-order chirped Airy vortex beams (FCAiV) in a chiral medium analytically. Results show that the FCAiV beams split into the left circularly polarized vortex (LCPV) beams and the right circularly polarized vortex (RCPV) beams, which have totally different propagation trajectories in the chiral medium. In this paper, we investigate the effects of the first-order chirped parameter β, the chiral parameter γ and the optical vortex on the propagation process of the FCAiV beams. It is shown that the propagation trajectory of the FCAiV beams declines with the chirped parameter increasing. Besides, the increase of the chiral parameter acting on the LCPV beams makes the relative position between the main lobe and the optical vortex further while the effect on the RCPV beams is the opposite. Furthermore, the relative position between the main lobe and the optical vortex contributes to the position of the intensity focusing. Meanwhile, with the chiral parameter increasing, the maximum gradient and scattering forces of the LCPV beams decrease but those of the RCPV beams will increase during the propagation. It is significant that we can control the propagation trajectory, the intensity focusing position and the radiation forces of the FCAiV beams by varying the chirped parameter and the chiral parameter.

Chirality plays critical roles in enhancing the aqueous solubility of nocathiacin I by block copolymer micelles.

PubMed

Feng, Kun; Wang, Shuzhen; Ma, Hairong; Chen, Yijun

2013-01-01

Although drug solubilization by block copolymer micelles has been extensively studied, the rationale behind the choice of appropriate block copolymer micelles for various poorly water-soluble drugs has been of relatively less concern. The objective of this study was to use methoxy-poly(ethylene glycol)-polylactate micelles (MPEG-PLA) to solubilize glycosylated antibiotic nocathiacin I and to compare the effects of chirality on the enhancement of aqueous solubility. Nocathiacin I-loaded MPEG-PLA micelles with opposite optical property in PLA were synthesized and characterized. The drug release profile, micelle stability and preliminary safety properties of MPEG-PLA micelles were evaluated. Meanwhile, three other poorly water-soluble chiral compound-loaded micelles were also prepared and compared.  The aqueous solubility of nocathiacin I was greatly enhanced by both L- and D-copolymers, with the degree of enhancement appearing to depend on the chirality of the copolymers. Comparison of different chiral compounds confirmed the trend that aqueous solubility of chiral compounds can be more effectively enhanced by block copolymer micelles with specific stereochemical configuration. The present study introduced chiral concept on the selection and preparation of block copolymer micelles for the enhancement of aqueous solubility of poorly water-soluble drugs. © 2012 The Authors. JPP © 2012 Royal Pharmaceutical Society.

Molecular self assembly and chiral recognition of copper octacyanophthalocyanine on Au(111): Interplay of intermolecular and molecule-substrate interactions.

NASA Astrophysics Data System (ADS)

Sk, Rejaul; Dhara, Barun; Miller, Joel; Deshpande, Aparna

Submolecular resolution scanning tunneling microscopy (STM) of copper octacyanophthalocyanine, CuPc(CN)8, at 77 K demonstrates that these achiral molecules form a two dimensional (2D) tetramer-based self-assembly upon evaporation onto an atomically flat Au(111) substrate. They assemble in two different structurally chiral configurations upon adsorption on Au(111). Scanning tunneling spectroscopy (STS),acquired at 77 K, unveils the HOMO and LUMO energy levels of this self-assembly. Voltage dependent STM images show that each molecule in both the structurally chiral configurations individually becomes chiral by breaking the mirror symmetry due to the enhanced intermolecular dipolar coupling interaction at the LUMO energy while the individual molecules remain achiral at the HOMO energy and within the HOMO-LUMO gap. At the LUMO energy, the handedness of the each chiral molecule is decided by the direction of the dipolar coupling interaction in the tetramer unit cell. This preference for LUMO energy indicates that this chirality is purely electronic in nature and it manifests on top of the organizational chirality that is present in the self-assembly independent of the orbital energy. Supported by IISER Pune and DAE-BRNS, India (Project No. 2011/20/37C/17/BRNS).

Chiral anomaly and longitudinal magnetotransport in type-II Weyl semimetals

NASA Astrophysics Data System (ADS)

Sharma, Girish; Goswami, Pallab; Tewari, Sumanta

2017-07-01

In the presence of parallel electric and magnetic fields, the violation of a separate number conservation laws for the three-dimensional left- and right-handed Weyl fermions is known as the chiral anomaly. The recent discovery of Weyl and Dirac semimetals has paved the way for experimentally testing the effects of chiral anomaly via magnetotransport measurements, since chiral anomaly can lead to negative longitudinal magnetoresistance (LMR) while the transverse magnetoresistance remains positive. More recently, a type-II Weyl semimetal (WSM) phase has been proposed, where the nodal points possess a finite density of states due to the touching between electron and hole pockets. It has been suggested that the main difference between the two types of WSMs (type I and type II) is that in the latter, chiral-anomaly-induced negative LMR (positive longitudinal magnetoconductance) is strongly anisotropic, vanishing when the applied magnetic field is perpendicular to the direction of tilt of Weyl fermion cones in a type-II WSM. We analyze chiral anomaly in a type-II WSM in a quasiclassical Boltzmann framework, and find that the chiral-anomaly-induced positive longitudinal magnetoconductivity is present along any arbitrary direction. Thus, our results are pertinent for uncovering transport signatures of type-II WSMs in different candidate materials.

Coexistence of both gyroid chiralities in individual butterfly wing scales of Callophrys rubi

PubMed Central

Winter, Benjamin; Butz, Benjamin; Dieker, Christel; Schröder-Turk, Gerd E.; Mecke, Klaus; Spiecker, Erdmann

2015-01-01

The wing scales of the Green Hairstreak butterfly Callophrys rubi consist of crystalline domains with sizes of a few micrometers, which exhibit a congenitally handed porous chitin microstructure identified as the chiral triply periodic single-gyroid structure. Here, the chirality and crystallographic texture of these domains are investigated by means of electron tomography. The tomograms unambiguously reveal the coexistence of the two enantiomeric forms of opposite handedness: the left- and right-handed gyroids. These two enantiomers appear with nonequal probabilities, implying that molecularly chiral constituents of the biological formation process presumably invoke a chiral symmetry break, resulting in a preferred enantiomeric form of the gyroid structure. Assuming validity of the formation model proposed by Ghiradella H (1989) J Morphol 202(1):69–88 and Saranathan V, et al. (2010) Proc Natl Acad Sci USA 107(26):11676–11681, where the two enantiomeric labyrinthine domains of the gyroid are connected to the extracellular and intra-SER spaces, our findings imply that the structural chirality of the single gyroid is, however, not caused by the molecular chirality of chitin. Furthermore, the wing scales are found to be highly textured, with a substantial fraction of domains exhibiting the <001> directions of the gyroid crystal aligned parallel to the scale surface normal. Both findings are needed to completely understand the photonic purpose of the single gyroid in gyroid-forming butterflies. More importantly, they show the level of control that morphogenesis exerts over secondary features of biological nanostructures, such as chirality or crystallographic texture, providing inspiration for biomimetic replication strategies for synthetic self-assembly mechanisms. PMID:26438839

Coexistence of both gyroid chiralities in individual butterfly wing scales of Callophrys rubi.

PubMed

Winter, Benjamin; Butz, Benjamin; Dieker, Christel; Schröder-Turk, Gerd E; Mecke, Klaus; Spiecker, Erdmann

2015-10-20

The wing scales of the Green Hairstreak butterfly Callophrys rubi consist of crystalline domains with sizes of a few micrometers, which exhibit a congenitally handed porous chitin microstructure identified as the chiral triply periodic single-gyroid structure. Here, the chirality and crystallographic texture of these domains are investigated by means of electron tomography. The tomograms unambiguously reveal the coexistence of the two enantiomeric forms of opposite handedness: the left- and right-handed gyroids. These two enantiomers appear with nonequal probabilities, implying that molecularly chiral constituents of the biological formation process presumably invoke a chiral symmetry break, resulting in a preferred enantiomeric form of the gyroid structure. Assuming validity of the formation model proposed by Ghiradella H (1989) J Morphol 202(1):69-88 and Saranathan V, et al. (2010) Proc Natl Acad Sci USA 107(26):11676-11681, where the two enantiomeric labyrinthine domains of the gyroid are connected to the extracellular and intra-SER spaces, our findings imply that the structural chirality of the single gyroid is, however, not caused by the molecular chirality of chitin. Furthermore, the wing scales are found to be highly textured, with a substantial fraction of domains exhibiting the <001> directions of the gyroid crystal aligned parallel to the scale surface normal. Both findings are needed to completely understand the photonic purpose of the single gyroid in gyroid-forming butterflies. More importantly, they show the level of control that morphogenesis exerts over secondary features of biological nanostructures, such as chirality or crystallographic texture, providing inspiration for biomimetic replication strategies for synthetic self-assembly mechanisms.

Origin of Stereodivergence in Cooperative Asymmetric Catalysis with Simultaneous Involvement of Two Chiral Catalysts.

PubMed

Bhaskararao, Bangaru; Sunoj, Raghavan B

2015-12-23

Accomplishing high diastereo- and enantioselectivities simultaneously is a persistent challenge in asymmetric catalysis. The use of two chiral catalysts in one-pot conditions might offer new avenues to this end. Chirality transfer from a catalyst to product gets increasingly complex due to potential chiral match-mismatch issues. The origin of high enantio- and diastereoselectivities in the reaction between a racemic aldehyde and an allyl alcohol, catalyzed by using axially chiral iridium phosphoramidites PR/S-Ir and cinchona amine is established through transition-state modeling. The multipoint contact analysis of the stereocontrolling transition state revealed how the stereodivergence could be achieved by inverting the configuration of the chiral catalysts that are involved in the activation of the reacting partners. While the enantiocontrol is identified as being decided in the generation of PR/S-Ir-π-allyl intermediate from the allyl alcohol, the diastereocontrol arises due to the differential stabilizations in the C-C bond formation transition states. The analysis of the weak interactions in the transition states responsible for chiral induction revealed that the geometric disposition of the quinoline ring at the C8 chiral carbon of cinchona-enamine plays an anchoring role. The quinolone ring is noted as participating in a π-stacking interaction with the phenyl ring of the Ir-π-allyl moiety in the case of PR with the (8R,9R)-cinchona catalyst combination, whereas a series of C-H···π interactions is identified as vital to the relative stabilization of the stereocontrolling transition states when PR is used with (8S,9S)-cinchona.

Visualizing Molecular Chirality in the Organic Chemistry Laboratory Using Cholesteric Liquid Crystals

ERIC Educational Resources Information Center

Popova, Maia; Bretz, Stacey Lowery; Hartley, C. Scott

2016-01-01

Although stereochemistry is an important topic in second-year undergraduate organic chemistry, there are limited options for laboratory activities that allow direct visualization of macroscopic chiral phenomena. A novel, guided-inquiry experiment was developed that allows students to explore chirality in the context of cholesteric liquid crystals.…

Multistep hierarchical self-assembly of chiral nanopore arrays

PubMed Central

Kim, Hanim; Lee, Sunhee; Shin, Tae Joo; Korblova, Eva; Walba, David M.; Clark, Noel A.; Lee, Sang Bok; Yoon, Dong Ki

2014-01-01

A series of simple hierarchical self-assembly steps achieve self-organization from the centimeter to the subnanometer-length scales in the form of square-centimeter arrays of linear nanopores, each one having a single chiral helical nanofilament of large internal surface area and interfacial interactions based on chiral crystalline molecular arrangements. PMID:25246585

IR properties of chiral effects in pionic matter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Avdoshkin, A.; Sadofyev, A. V.; Zakharov, V. I.

Chiral effects exhibit peculiar universality in idealized theoretical limits. However, they are known to be infrared sensitive and get modified in more realistic settings. In this work we study how the corresponding conductivities vary with the constituent mass. We concentrate on a pionic realization of chiral effects which provides a better control over infrared properties of the theory. The pionic medium is considered at finite vector and axial isospin chemical potentials in the presence of an external magnetic field. This system supports electric and axial isospin currents along the magnetic field which correspond to chiral magnetic and chiral separation effects.more » We show that these currents are sensitive to the finite mass of the constituents but the conductivities follow a simple scaling with the corresponding charge densities as one would expect for polarization effects. It is argued that this relation can capture the dependence of chiral effects on other infrared parameters. Finally, we briefly comment on the realization of the ’t Hooft matching condition in pionic media at finite densities.« less

Second Harmonic Generation Optical Rotation Solely Attributable to Chirality in Plasmonic Metasurfaces.

PubMed

Collins, Joel T; Hooper, David C; Mark, Andrew G; Kuppe, Christian; Valev, Ventsislav Kolev

2018-05-31

Chiral plasmonic nanostructures, those lacking mirror symmetry, can be designed to manipulate the polarization of incident light resulting in chiroptical (chiral optical) effects such as circular dichroism (CD) and optical rotation (OR). Due to high symmetry sensitivity, corresponding effects in second harmonic generation (SHG-CD and SHG-OR) are typically much stronger in comparison. These nonlinear effects have long been used for chiral molecular analysis and characterization, however both linear and nonlinear optical rotation can occur even in achiral structures, if the structure is birefringent due to anisotropy. Crucially, chiroptical effects resulting from anisotropy typically exhibit a strong dependence on structural orientation. Here we report large second-harmonic generation optical rotation of ±45°, due to intrinsic chirality in a highly anisotropic helical metamaterial. The SHG intensity is found to strongly relate to the structural anisotropy, however the angle of SHG-OR is invariant under sample rotation. We show that by tuning the geometry of anisotropic nanostructures, the interaction between anisotropy, chirality, and experiment geometry can allow even greater control over the chiroptical properties of plasmonic metamaterials.

Chirality in Magnetic Multilayers Probed by the Symmetry and the Amplitude of Dichroism in X-Ray Resonant Magnetic Scattering

NASA Astrophysics Data System (ADS)

Chauleau, Jean-Yves; Legrand, William; Reyren, Nicolas; Maccariello, Davide; Collin, Sophie; Popescu, Horia; Bouzehouane, Karim; Cros, Vincent; Jaouen, Nicolas; Fert, Albert

2018-01-01

Chirality in condensed matter has recently become a topic of the utmost importance because of its significant role in the understanding and mastering of a large variety of new fundamental physical mechanisms. Versatile experimental approaches, capable to reveal easily the exact winding of order parameters, are therefore essential. Here we report x-ray resonant magnetic scattering as a straightforward tool to reveal directly the properties of chiral magnetic systems. We show that it can straightforwardly and unambiguously determine the main characteristics of chiral magnetic distributions: i.e., its chiral nature, the quantitative winding sense (clockwise or counterclockwise), and its type, i.e., Néel [cycloidal] or Bloch [helical]. This method is model independent, does not require a priori knowledge of the magnetic parameters, and can be applied to any system with magnetic domains ranging from a few nanometers (wavelength limited) to several microns. By using prototypical multilayers with tailored magnetic chiralities driven by spin-orbit-related effects at Co |Pt interfaces, we illustrate the strength of this method.

Chiral symmetry breaking and the spin content of hadrons

NASA Astrophysics Data System (ADS)

Glozman, L. Ya.; Lang, C. B.; Limmer, M.

2012-04-01

From the parton distributions in the infinite momentum frame, one finds that only about 30% of the nucleon spin is carried by spins of the valence quarks, which gave rise to the term “spin crisis”. Similar results hold for the lowest mesons, as it follows from the lattice simulations. We define the spin content of a meson in the rest frame and use a complete and orthogonal q¯q chiral basis and a unitary transformation from the chiral basis to the 2LJ basis. Then, given a mixture of different allowed chiral representations in the meson wave function at a given resolution scale, one can obtain its spin content at this scale. To obtain the mixture of the chiral representations in the meson, we measure in dynamical lattice simulations a ratio of couplings of interpolators with different chiral structure. For the ρ meson, we obtain practically the 3S1 state with no trace of the spin crisis. Then a natural question arises: which definition does reflect the spin content of a hadron?

Pharmacokinetics of Chiral Dendrimer-Triamine-Coordinated Gd-MRI Contrast Agents Evaluated by in Vivo MRI and Estimated by in Vitro QCM.

PubMed

Miyake, Yuka; Ishikawa, Syungo; Kimura, Yu; Son, Aoi; Imai, Hirohiko; Matsuda, Tetsuya; Yamada, Hisatsugu; Toshimitsu, Akio; Kondo, Teruyuki

2015-12-18

Recently, we developed novel chiral dendrimer-triamine-coordinated Gd-MRI contrast agents (Gd-MRI CAs), which showed longitudinal relaxivity (r₁) values about four times higher than that of clinically used Gd-DTPA (Magnevist(®), Bayer). In our continuing study of pharmacokinetic differences derived from both the chirality and generation of Gd-MRI CAs, we found that the ability of chiral dendrimer Gd-MRI CAs to circulate within the body can be directly evaluated by in vitro MRI (7 T). In this study, the association constants (K(a)) of chiral dendrimer Gd-MRI CAs to bovine serum albumin (BSA), measured and calculated with a quartz crystal microbalance (QCM) in vitro, were found to be an extremely easy means for evaluating the body-circulation ability of chiral dendrimer Gd-MRI CAs. The K(a) values of S-isomeric dendrimer Gd-MRI CAs were generally greater than those of R-isomeric dendrimer Gd-MRI CAs, which is consistent with the results of our previous MRI study in vivo.

Influence of optical activity on rogue waves propagating in chiral optical fibers.

PubMed

Temgoua, D D Estelle; Kofane, T C

2016-06-01

We derive the nonlinear Schrödinger (NLS) equation in chiral optical fiber with right- and left-hand nonlinear polarization. We use the similarity transformation to reduce the generalized chiral NLS equation to the higher-order integrable Hirota equation. We present the first- and second-order rational solutions of the chiral NLS equation with variable and constant coefficients, based on the modified Darboux transformation method. For some specific set of parameters, the features of chiral optical rogue waves are analyzed from analytical results, showing the influence of optical activity on waves. We also generate the exact solutions of the two-component coupled nonlinear Schrödinger equations, which describe optical activity effects on the propagation of rogue waves, and their properties in linear and nonlinear coupling cases are investigated. The condition of modulation instability of the background reveals the existence of vector rogue waves and the number of stable and unstable branches. Controllability of chiral optical rogue waves is examined by numerical simulations and may bring potential applications in optical fibers and in many other physical systems.

Surface operators, chiral rings and localization in N =2 gauge theories

NASA Astrophysics Data System (ADS)

Ashok, S. K.; Billò, M.; Dell'Aquila, E.; Frau, M.; Gupta, V.; John, R. R.; Lerda, A.

2017-11-01

We study half-BPS surface operators in supersymmetric gauge theories in four and five dimensions following two different approaches. In the first approach we analyze the chiral ring equations for certain quiver theories in two and three dimensions, coupled respectively to four- and five-dimensional gauge theories. The chiral ring equations, which arise from extremizing a twisted chiral superpotential, are solved as power series in the infrared scales of the quiver theories. In the second approach we use equivariant localization and obtain the twisted chiral superpotential as a function of the Coulomb moduli of the four- and five-dimensional gauge theories, and find a perfect match with the results obtained from the chiral ring equations. In the five-dimensional case this match is achieved after solving a number of subtleties in the localization formulas which amounts to choosing a particular residue prescription in the integrals that yield the Nekrasov-like partition functions for ramified instantons. We also comment on the necessity of including Chern-Simons terms in order to match the superpotentials obtained from dual quiver descriptions of a given surface operator.

Chiral anomaly, Berry phase, and chiral kinetic theory from worldlines in quantum field theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mueller, Niklas; Venugopalan, Raju

Here, we outline a novel chiral kinetic theory framework for systematic computations of the Chiral Magnetic Effect (CME) in ultrarelativistic heavy-ion collisions. The real part of the fermion determinant in the QCD effective action is expressed as a supersymmetric world-line action of spinning, colored, Grassmanian point particles in background gauge fields, with equations of motion that are covariant generalizations of the Bargmann-Michel-Telegdi and Wong equations. Berry’s phase is obtained in a consistent non-relativistic adiabatic limit. The chiral anomaly, in contrast, arises from the phase of the fermion determinant; its topological properties are therefore distinct from those of the Berry phase.more » We show that the imaginary contribution to the fermion determinant too can be expressed as a point particle world-line path integral and derive the corresponding anomalous axial vector current. Our results can be used to derive a covariant relativistic chiral kinetic theory including the effects of topological fluctuations that has overlap with classical-statistical simulations of the CME at early times and anomalous hydrodynamics at late times.« less

Investigation of the chiral antiferromagnetic Heisenberg model using projected entangled pair states

NASA Astrophysics Data System (ADS)

Poilblanc, Didier

2017-09-01

A simple spin-1/2 frustrated antiferromagnetic Heisenberg model (AFHM) on the square lattice—including chiral plaquette cyclic terms—was argued [A. E. B. Nielsen, G. Sierra, and J. I. Cirac, Nat. Commun. 4, 2864 (2013), 10.1038/ncomms3864] to host a bosonic Kalmeyer-Laughlin (KL) fractional quantum Hall ground state [V. Kalmeyer and R. B. Laughlin, Phys. Rev. Lett. 59, 2095 (1987), 10.1103/PhysRevLett.59.2095]. Here, we construct generic families of chiral projected entangled pair states (chiral PEPS) with low bond dimension (D =3 ,4 ,5 ) which, upon optimization, provide better variational energies than the KL Ansatz. The optimal D =3 PEPS exhibits chiral edge modes described by the Wess-Zumino-Witten SU(2) 1 model, as expected for the KL spin liquid. However, we find evidence that, in contrast to the KL state, the PEPS spin liquids have power-law dimer-dimer correlations and exhibit a gossamer long-range tail in the spin-spin correlations. We conjecture that these features are genuine to local chiral AFHM on bipartite lattices.

Central-to-axial chirality transfer revealed by liquid crystals: a combined experimental and computational approach for the determination of absolute configuration of carboxylic acids with an α chirality centre.

PubMed

Ferrarini, Alberta; Ferroni, Fiammetta; Pieraccini, Silvia; Rosini, Carlo; Superchi, Stefano; Spada, Gian Piero

2011-10-01

The conversion into 6,7-dihydro-5H-dibenz[c,e]azepine (DAZ) N-protected amides is a viable route for the determination of the absolute configuration of chiral 2-substituted carboxylic acids. The biphenyl moiety of DAZ, besides being a probe of chirality for the electronic circular dichroism (ECD) spectroscopy, makes these systems suitable for configuration assignment by exploiting the chirality amplification which occurs in nematic liquid crystals. To assess the reliability of the liquid crystal method in detecting the absolute stereochemistry of chiral amides bound to a biphenyl group, we measured the helical twisting power of a series of DAZ-N-protected amides and compared these data with the results obtained from ECD measurements. We will show that the liquid crystal method, corroborated by HTP predictions, is trustworthy with our biphenyl derivatives, even when ECD spectra are ambiguous for the presence of aryl moieties displaying strong UV absorptions in the same range of the biphenyl chromophore. © 2011 Wiley-Liss, Inc.

Formation of Coaxial Nanocables with Amplified Supramolecular Chirality through an Interaction between Carbon Nanotubes and a Chiral π-Gelator.

PubMed

Vedhanarayanan, Balaraman; Nair, Vishnu S; Nair, Vijayakumar C; Ajayaghosh, Ayyappanpillai

2016-08-22

In an attempt to gather experimental evidence for the influence of carbon allotropes on supramolecular chirality, we found that carbon nanotubes (CNTs) facilitate amplification of the molecular chirality of a π-gelator (MC-OPV) to supramolecular helicity at a concentration much lower than that required for intermolecular interaction. For example, at a concentration 1.8×10(-4)  m, MC-OPV did not exhibit a CD signal; however, the addition of 0-0.6 mg of SWNTs resulted in amplified chirality as evident from the CD spectrum. Surprisingly, AFM analysis revealed the formation of thick helical fibers with a width of more than 100 nm. High-resolution TEM analysis and solid-state UV/Vis/NIR spectroscopy revealed that the thick helical fibers were cylindrical cables composed of individually wrapped and coaxially aligned SWNTs. Such an impressive effect of CNTs on supramolecular chirality and cylindrical-cable formation has not been reported previously. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development of Ar-BINMOL-Derived Atropisomeric Ligands with Matched Axial and sp(3) Central Chirality for Catalytic Asymmetric Transformations.

PubMed

Xu, Zheng; Xu, Li-Wen

2015-10-01

Recently, academic chemists have renewed their interest in the development of 1,1'-binaphthalene-2,2'-diol (BINOL)-derived chiral ligands. Six years ago, a working hypothesis, that the chirality matching of hybrid chirality on a ligand could probably lead to high levels of stereoselective induction, prompted us to use the axial chirality of BINOL derivatives to generate new stereogenic centers within the same molecule with high stereoselectivity, obtaining as a result sterically favorable ligands for applications in asymmetric catalysis. This Personal Account describes our laboratory's efforts toward the development of a novel class of BINOL-derived atropisomers bearing both axial and sp(3) central chirality, the so-called Ar-BINMOLs, for asymmetric synthesis. Furthermore, on the basis of the successful application of Ar-BINMOLs and their derivatives in asymmetric catalysis, the search for highly efficient and enantioselective processes also compelled us to give special attention to the BINOL-derived multifunctional ligands with multiple stereogenic centers for use in catalytic asymmetric reactions. Copyright © 2015 The Chemical Society of Japan and Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Patterns of symmetry breaking in chiral QCD

NASA Astrophysics Data System (ADS)

Bolognesi, Stefano; Konishi, Kenichi; Shifman, Mikhail

2018-05-01

We consider S U (N ) Yang-Mills theory with massless chiral fermions in a complex representation of the gauge group. The main emphasis is on the so-called hybrid ψ χ η model. The possible patterns of realization of the continuous chiral flavor symmetry are discussed. We argue that the chiral symmetry is broken in conjunction with a dynamical Higgsing of the gauge group (complete or partial) by bifermion condensates. As a result a color-flavor locked symmetry is preserved. The 't Hooft anomaly matching proceeds via saturation of triangles by massless composite fermions or, in a mixed mode, i.e. also by the "weakly" coupled fermions associated with dynamical Abelianization, supplemented by a number of Nambu-Goldstone mesons. Gauge-singlet condensates are of the multifermion type and, though it cannot be excluded, the chiral symmetry realization via such gauge invariant condensates is more contrived (requires a number of four-fermion condensates simultaneously and, even so, problems remain) and less plausible. We conclude that in the model at hand, chiral flavor symmetry implies dynamical Higgsing by bifermion condensates.

Out-of-equilibrium chiral magnetic effect from chiral kinetic theory

NASA Astrophysics Data System (ADS)

Huang, Anping; Jiang, Yin; Shi, Shuzhe; Liao, Jinfeng; Zhuang, Pengfei

2018-02-01

Recently there has been significant interest in the macroscopic manifestation of chiral anomaly in many-body systems of chiral fermions. A notable example is the Chiral Magnetic Effect (CME). Enthusiastic efforts have been made to search for the CME in the quark-gluon plasma created in heavy ion collisions. A crucial challenge is that the extremely strong magnetic field in such collisions may last only for a brief moment and the CME current may have to occur at so early a stage that the quark-gluon matter is still far from thermal equilibrium. This thus requires modeling of the CME in an out-of-equilibrium setting. With the recently developed theoretical tool of chiral kinetic theory, we make a first phenomenological study of the CME-induced charge separation during the pre-thermal stage in heavy ion collisions. The effect is found to be very sensitive to the time dependence of the magnetic field and also influenced by the initial quark momentum spectrum as well as the relaxation time of the system evolution toward thermal equilibrium. Within the present approach, such pre-thermal charge separation is found to be modest.

Chirality of the 1,4-phenylene-silica nanoribbons at the nano and angstrom levels

NASA Astrophysics Data System (ADS)

Li, Yi; Wang, Sibing; Xiao, Min; Wang, Mingliang; Huang, Zhibin; Li, Baozong; Yang, Yonggang

2013-01-01

We reported the preparation of chiral 1,4-phenylene-silicas, using a sol-gel transcription approach, by self-assembly using low-molecular-weight gelators as templates. The silicas exhibited chirality at both the nano and angstrom levels. However, the relation between the chirality at the nano level and that at the angstrom levels has not been well studied. In this study, chiral 1,4-phenylene-silica nanoribbons were prepared by the self-assemblies of three chiral cationic gelators derived from amino acids as templates. These samples were characterized using field-emission scanning electron microscopy, transmission electron microscopy, x-ray diffraction, and circular dichroism. The results indicated that the handedness of the nanoribbons and the stacking of the aromatic rings were controllable. Although the nanoribbons exhibited left-handedness at the nano level, the stacking of the aromatic rings could exhibit left- or right-handedness. The handedness of the nanoribbons at the nano level was controlled by the organic self-assembly of the gelator. However, the stacking of the aromatic rings seemed to be controlled by the gelator itself.

Quantum formulation for nanoscale optical and material chirality: symmetry issues, space and time parity, and observables

NASA Astrophysics Data System (ADS)

Andrews, D. L.

2018-03-01

To properly represent the interplay and coupling of optical and material chirality at the photon-molecule or photon-nanoparticle level invites a recognition of quantum facets in the fundamental aspects and mechanisms of light-matter interaction. It is therefore appropriate to cast theory in a general quantum form, one that is applicable to both linear and nonlinear optics as well as various forms of chiroptical interaction including chiral optomechanics. Such a framework, fully accounting for both radiation and matter in quantum terms, facilitates the scrutiny and identification of key issues concerning spatial and temporal parity, scale, dissipation and measurement. Furthermore it fully provides for describing the interactions of structured or twisted light beams with a vortex character, and it leads to the complete identification of symmetry conditions for materials to provide for chiral discrimination. Quantum considerations also lend a distinctive perspective to the very different senses in which other aspects of chirality are recognized in metamaterials. Duly attending to the symmetry principles governing allowed or disallowed forms of chiral discrimination supports an objective appraisal of the experimental possibilities and developing applications.

Chiral anomaly and anomalous finite-size conductivity in graphene

NASA Astrophysics Data System (ADS)

Shen, Shun-Qing; Li, Chang-An; Niu, Qian

2017-09-01

Graphene is a monolayer of carbon atoms packed into a hexagon lattice to host two spin degenerate pairs of massless two-dimensional Dirac fermions with different chirality. It is known that the existence of non-zero electric polarization in reduced momentum space which is associated with a hidden chiral symmetry will lead to the zero-energy flat band of a zigzag nanoribbon and some anomalous transport properties. Here it is proposed that the Adler-Bell-Jackiw chiral anomaly or non-conservation of chiral charges of Dirac fermions at different valleys can be realized in a confined ribbon of finite width, even in the absence of a magnetic field. In the laterally diffusive regime, the finite-size correction to conductivity is always positive and is inversely proportional to the square of the lateral dimension W, which is different from the finite-size correction inversely proportional to W from the boundary modes. This anomalous finite-size conductivity reveals the signature of the chiral anomaly in graphene, and it is measurable experimentally. This finding provides an alternative platform to explore the purely quantum mechanical effect in graphene.

IR properties of chiral effects in pionic matter

DOE PAGES

Avdoshkin, A.; Sadofyev, A. V.; Zakharov, V. I.

2018-04-27

Chiral effects exhibit peculiar universality in idealized theoretical limits. However, they are known to be infrared sensitive and get modified in more realistic settings. In this work we study how the corresponding conductivities vary with the constituent mass. We concentrate on a pionic realization of chiral effects which provides a better control over infrared properties of the theory. The pionic medium is considered at finite vector and axial isospin chemical potentials in the presence of an external magnetic field. This system supports electric and axial isospin currents along the magnetic field which correspond to chiral magnetic and chiral separation effects.more » We show that these currents are sensitive to the finite mass of the constituents but the conductivities follow a simple scaling with the corresponding charge densities as one would expect for polarization effects. It is argued that this relation can capture the dependence of chiral effects on other infrared parameters. Finally, we briefly comment on the realization of the ’t Hooft matching condition in pionic media at finite densities.« less