New pentacoordinated rhodium species as unexpected products during the in situ generation of dimeric diphosphine-rhodium neutral catalysts.

PubMed

Meissner, Antje; König, Anja; Drexler, Hans-Joachim; Thede, Richard; Baumann, Wolfgang; Heller, Detlef

2014-11-03

Dimeric rhodium complexes of the type [Rh(PP)(μ2 -Cl)]2 (PP=diphosphine) are often used as precatalysts and are generated "in situ" from the corresponding diolefin complexes by exchange of the diene with the desired diphosphine. Herein, we report that the "in situ" procedure also leads to unexpected monomeric pentacoordinated neutral complexes of the type [RhCl(PP)(diolefin)], for the first time herein characterized by NMR spectroscopy and X-ray crystallography for the ligands 1,4-bis(diphenylphosphino)propane (DPPP), 1,4-bis(diphenylphosphino)butane (DPPB), and 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP). The pentacoordinated complexes are in equilibrium with the dimeric target compound [Rh(PP)(μ2 -Cl)]2 . The equilibrium is influenced by the rhodium-diolefin precursor, the solvent and the temperature. Based on the results of NMR and UV/Vis spectroscopic analysis (kinetics) it could be shown that the pentacoordinated complex [RhCl(PP)(diolefin)] may arise both from the "in situ"-generated neutral complex [Rh(PP)(μ2 -Cl)] by reaction with the free diolefin and, more surprisingly, directly from [Rh(diolefin)(μ2 -Cl)]2 and the diphosphine. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

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 and achiral phosphine derivatives of alkylidyne tricobalt carbonyl clusters as catalyst precursors for (asymmetric) inter- and intramolecular Pauson-Khand reactions.

PubMed

Moberg, Viktor; Mottalib, M Abdul; Sauer, Désirée; Poplavskaya, Yulia; Craig, Donald C; Colbran, Stephen B; Deeming, Antony J; Nordlander, Ebbe

2008-05-14

Phosphine derivatives of alkylidyne tricobalt carbonyl clusters have been tested as catalysts/catalyst precursors in intermolecular and (asymmetric) intramolecular Pauson-Khand reactions. A number of new phosphine derivatives of the tricobalt alkylidyne clusters [Co3(micro3-CR)(CO)9] (R = H, CO2Et) were prepared and characterised. The clusters [Co3(micro3-CR)(CO)9-x(PR'3)x] (PR'3 = achiral or chiral monodentate phosphine, x = 1-3) and [Co3(micro3-CR)(CO)7)(P-P)] (P-P = chiral diphosphine; 1,1'- and 1,2-structural isomers) were assayed as catalysts for intermolecular and (asymmetric) intramolecular Pauson-Khand reactions. The phosphine-substituted tricobalt clusters proved to be viable catalysts/catalyst precursors that gave moderate to very good product yields (up to approximately 90%), but the enantiomeric excesses were too low for the clusters to be of practical use in the asymmetric reactions.

Influence of pendant chiral C(γ)-(alkylideneamino/guanidino) cationic side-chains of PNA backbone on hybridization with complementary DNA/RNA and cell permeability.

PubMed

Jain, Deepak R; Anandi V, Libi; Lahiri, Mayurika; Ganesh, Krishna N

2014-10-17

Intrinsically cationic and chiral C(γ)-substituted peptide nucleic acid (PNA) analogues have been synthesized in the form of γ(S)-ethyleneamino (eam)- and γ(S)-ethyleneguanidino (egd)-PNA with two carbon spacers from the backbone. The relative stabilization (ΔTm) of duplexes from modified cationic PNAs as compared to 2-aminoethylglycyl (aeg)-PNA is better with complementary DNA (PNA:DNA) than with complementary RNA (PNA:RNA). Inherently, PNA:RNA duplexes have higher stability than PNA:DNA duplexes, and the guanidino PNAs are superior to amino PNAs. The cationic PNAs were found to be specific toward their complementary DNA target as seen from their significantly lower binding with DNA having single base mismatch. The differential binding avidity of cationic PNAs was assessed by the displacement of DNA duplex intercalated ethidium bromide and gel electrophoresis. The live cell imaging of amino/guanidino PNAs demonstrated their ability to penetrate the cell membrane in 3T3 and MCF-7 cells, and cationic PNAs were found to be accumulated in the vicinity of the nuclear membrane in the cytoplasm. Fluorescence-activated cell sorter (FACS) analysis of cell permeability showed the efficiency to be dependent upon the nature of cationic functional group, with guanidino PNAs being better than the amino PNAs in both cell lines. The results are useful to design new biofunctional cationic PNA analogues that not only bind RNA better but also show improved cell permeability.

Steric and electronic ligand perturbations in catalysis: asymmetric allylic substitution reactions using C2-symmetrical phosphorus-chiral (bi)ferrocenyl donors.

PubMed

Nettekoven, U; Widhalm, M; Kalchhauser, H; Kamer, P C; van Leeuwen, P W; Lutz, M; Spek, A L

2001-02-09

Three series of P-chiral diphosphines based on ferrocene (1a-f, 2a-c) and biferrocenyl skeletons (3a-c), including novel ligands 1f and 3c, were employed in palladium-catalyzed allylic substitution reactions. Steric effects imposed by the phosphine residues were studied using C2-symmetrical donors 1 (1 = 1,1'-bis(arylphenylphosphino)ferrocene with aryl groups a = 1-naphthyl, b = 2-naphthyl, c = 2-anisyl, d = 2-biphenylyl, e = 9-phenanthryl, and f = ferrocenyl), whereas para-methoxy- and/or para-trifluoromethyl substitution of the phenyl moieties in 1a enabled investigation of ligand electronic effects applying ferrocenyl diphosphines 2a-c. Ligands 3 (3 = 2,2'-bis- (arylphenylphosphino)-1,1'-biferrocenyls with aryl substituents a,c = 1-naphthyl (diastereomers) and b = 2-biphenylyl) allowed for comparison of backbone structure effects (bite angle variation) in catalysis. Linear and cyclic allylic acetates served as substrates in typical test reactions; upon attack of soft carbon and nitrogen nucleophiles on (E)-1,3-diphenylprop-2-ene-1-yl acetate the respective malonate, amine, or imide products were obtained in enantioselectivities of up to 99% ee. A crystal structure analysis of a palladium 1,3-diphenyl-eta 3-allyl complex incorporating ligand (S,S)-1a revealed a marked distortion of the allyl fragment, herewith defining the regioselectivity of nucleophile addition.

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.

Stabilizing subnanometer Ag(0) nanoclusters by thiolate and diphosphine ligands and their crystal structures

NASA Astrophysics Data System (ADS)

Yang, Huayan; Wang, Yu; Zheng, Nanfeng

2013-03-01

The combined use of thiolate and diphosphine as surface ligands helps to stabilize subnanometer Ag(0) nanoclusters, resulting in the successful crystallization of two Ag(0)-containing nanoclusters (Ag16 and Ag32) for X-ray single crystal analysis. Both clusters have core-shell structures with Ag86+ and Ag2212+ as their cores, which are not simply either fragments of face-centered cubic metals or their five-fold twinned counterparts. The clusters display UV-Vis absorption spectra consisting of molecule-like optical transitions.The combined use of thiolate and diphosphine as surface ligands helps to stabilize subnanometer Ag(0) nanoclusters, resulting in the successful crystallization of two Ag(0)-containing nanoclusters (Ag16 and Ag32) for X-ray single crystal analysis. Both clusters have core-shell structures with Ag86+ and Ag2212+ as their cores, which are not simply either fragments of face-centered cubic metals or their five-fold twinned counterparts. The clusters display UV-Vis absorption spectra consisting of molecule-like optical transitions. Electronic supplementary information (ESI) available: Experimental details, more pictures of the structure and XPS spectra of the clusters. CCDC 916463 and 916464. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c3nr34328f

Systematic Introduction of Aromatic Rings to Diphosphine Ligands for Emission Color Tuning of Dinuclear Copper(I) Iodide Complexes.

PubMed

Okano, Yuka; Ohara, Hiroki; Kobayashi, Atsushi; Yoshida, Masaki; Kato, Masako

2016-06-06

We have newly synthesized two solution-stable luminescent dinuclear copper(I) complexes, [Cu2(μ-I)2(dpppy)2] (Cu-py) and [Cu2(μ-I)2(dpppyz)2] (Cu-pyz), where dpppy = 2,3-bis(diphenylphosphino)pyridine and dpppyz = 2,3-bis(diphenylphosphino)pyrazine, using chelating diphosphine ligands composed of N-heteroaromatic rings. X-ray analysis clearly indicates that the molecular structures of Cu-py and Cu-pyz are almost identical with that of the parent complex, [Cu2(μ-I)2(dppb)2] [Cu-bz; dppb = 2,3-bis(diphenylphosphino)benzene]. Complexes Cu-py and Cu-pyz exhibit luminescence [emission quantum yield (Φem) = 0.48 and 0.02, respectively] in the solid state at 298 K. A wide emission color tuning, from 497 to 638 nm (energy = 0.55 eV, with an emission color ranging from green to reddish-orange), was achieved in the solid state by the introduction of pyridinic N atoms into the bridging phenyl group between the two diphenylphosphine groups. Density functional theory calculations suggest that the emission could originate from the effective combination of the metal-to-ligand charge-transfer excited state with the halide-to-ligand charge-transfer excited state. Thus, the emission color change is due to stabilization of the π* levels of the central aryl group in the diphosphine ligand. Furthermore, these copper(I) complexes exhibit thermally activated delayed fluorescence at 298 K because of the small singlet-triplet energy difference (ΔE = 523 and 564 cm(-1) for Cu-py and Cu-pyz, respectively). The stability of these complexes in chloroform, due to the rigid bonds between the diphosphine ligands and the Cu(I) ions, enables the preparation of emissive poly(methyl methacrylate) films by the solution-doping technique.

Highly efficient hydrogenation of carbon dioxide to formate catalyzed by iridium(iii) complexes of imine-diphosphine ligands.

PubMed

Liu, Chong; Xie, Jian-Hua; Tian, Gui-Long; Li, Wei; Zhou, Qi-Lin

2015-05-01

A new iridium catalyst containing an imine-diphosphine ligand has been developed, which showed high efficiency for the hydrogenation of CO 2 to formate (yield up to 99%, TON up to 450 000). A possible catalytic mechanism is proposed, in which the imine group of the catalyst plays a key role in the cleavage of H 2 and the activation of CO 2 .

Double interpenetration in a chiral three-dimensional magnet with a (10,3)-a structure.

PubMed

Grancha, Thais; Mon, Marta; Lloret, Francesc; Ferrando-Soria, Jesús; Journaux, Yves; Pasán, Jorge; Pardo, Emilio

2015-09-21

A unique chiral three-dimensional magnet with an overall racemic double-interpenetrated (10,3)-a structure of the formula [(S)-(1-PhEt)Me3N]4[Mn4Cu6(Et2pma)12](DMSO)3]·3DMSO·5H2O (1; Et2pma = N-2,6-diethylphenyloxamate) has been synthesized by the self-assembly of a mononuclear copper(II) complex acting as a metalloligand toward Mn(II) ions in the presence of a chiral cationic auxiliary, constituting the first oxamato-based chiral coordination polymer exhibiting long-range magnetic ordering.

Synthesis, Structures, and Reactions of Manganese Complexes Containing Diphosphine Ligands With Pendant Amines

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

Welch, Kevin D.; Dougherty, William G.; Kassel, W. S.

2010-10-01

Addition of the pendant amine ligand PNRP (PNRP = Et2PCH2NRCH2PEt2; R = Me, Ph, n-Bu) to Mn(CO)5Br gives fac-Mn(PNRP)(CO)3Br. Photolysis of fac-Mn(PNRP)(CO)3Br with dppm [dppm = 1,2-bis(diphenylphosphino)methane] provides mixed bis(diphosphine) complexes, trans-Mn(PNRP)(dppm)(CO)(Br). Reaction of trans-Mn(PNRP)(dppm)(CO)(Br) with LiAlH4 leads to trans-Mn(PNRP)(dppm)(CO)(H). The crystal structure of trans-Mn(PNMeP)(dppm)(CO)(H) determined by x-ray diffraction shows an unusual distortion of the Mn-H towards one C-H of the dppm ligand, resulting in an H Mn CO angle of 155(1)° and C H • • • H Mn distance of 2.10(3) Å. Mn(P2PhN2Bn)(dppm)(CO)(H) [P2PhN2Bn = 1, 5-diphenyl-3,7-dibenzyl-1,5-diaza-3,7-diphosphacyclooctane] can be prepared in a similar manner; its structure has onemore » chelate ring in a chair conformation and the second in a boat conformation. The boat-conformer ring directs the nitrogen of the ring towards the carbonyl ligand, and the N • • • C distance between one N of the P2PhN2Bn ligand and CO is 3.171(4) Å, indicating a weak interaction between the N of the pendant amine and the CO ligand. Reaction of NaBArF4 (ArF = = 3,5-bis(trifluoromethyl)phenyl) with Mn(P P)(dppm)(CO)(Br) produces the cations [Mn(P P)(dppm)(CO)]+. The crystal structure of [Mn(PNMeP)(dppm)(CO)][BArF4] shows two very weak agostic interactions between C-H bonds on the phenyl ring and the Mn. The cationic complexes [Mn(P P)(dppm)(CO)]+ react with H2 to form dihydrogen complexes [Mn(H2)(P P)(dppm)(CO)]+ (Keq = 1 - 90 atm-1 in fluorobenzene, for a series of different P P ligands). Similar equilibria with N2 produce [Mn(N2)(P P)(dppm)(CO)]+ (Keq generally 1-3.5 atm-1 in fluorobenzene). This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.« less

A Carbon Dioxide Bubble-Induced Vortex Triggers Co-Assembly of Nanotubes with Controlled Chirality.

PubMed

Zhang, Ling; Zhou, Laicheng; Xu, Na; Ouyang, Zhenjie

2017-07-03

It is challenging to prepare co-organized nanotube systems with controlled nanoscale chirality in an aqueous liquid flow field. Such systems are responsive to a bubbled external gas. A liquid vortex induced by bubbling carbon dioxide (CO 2 ) gas was used to stimulate the formation of nanotubes with controlled chirality; two kinds of achiral cationic building blocks were co-assembled in aqueous solution. CO 2 -triggered nanotube formation occurs by formation of metastable intermediate structures (short helical ribbons and short tubules) and by transition from short tubules to long tubules in response to chirality matching self-assembly. Interestingly, the chirality sign of these assemblies can be selected for by the circulation direction of the CO 2 bubble-induced vortex during the co-assembly process. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cation-enhanced capillary electrophoresis separation of atropoisomer anions.

PubMed

Na, Yun-Cheol; Berthod, Alain; Armstrong, Daniel W

2015-12-01

CE was used to study the separation of the atropoisomers of four phosphoric acids and two sulfonic acids and the enantiomers of two phosphoric acids. All solutes are in their anionic forms in aqueous electrolytes. The chiral additives were two hydroxypropyl cyclodextrins (CDs) and cyclofructan 6 (CF6). The CDs were able to separate four solutes and the CF6 additive could separate only one: 1,1'-binaphthyl-2,2'-diyl hydrogenphosphate (BHP). Since CF6 is able to bind with cations, nitrate of alkaline metals, Ba(2+) , and Pb(2+) were added, greatly improving the BHP separation at the expense of longer migration times. There seems to be a link between CF6-cation-binding constants and BHP resolution factors. Cation additions were also performed with CD selectors that are less prone to form complexes with cations. Significant improvements of enantiomer or atropoisomer separations were observed also associated with longer migration times. It is speculated that the anionic solutes associate with the added cations forming larger entities better differentiated by CDs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Computational Design of Iron Diphosphine Complexes with Pendant Amines for Hydrogenation of CO2 to Methanol: A Mimic of [NiFe] Hydrogenase.

PubMed

Chen, Xiangyang; Jing, Yuanyuan; Yang, Xinzheng

2016-06-20

Inspired by the active-site structure of the [NiFe] hydrogenase, we have computationally designed the iron complex [P(tBu) 2 N(tBu) 2 )Fe(CN)2 CO] by using an experimentally ready-made diphosphine ligand with pendant amines for the hydrogenation of CO2 to methanol. Density functional theory calculations indicate that the rate-determining step in the whole catalytic reaction is the direct hydride transfer from the Fe center to the carbon atom in the formic acid with a total free energy barrier of 28.4 kcal mol(-1) in aqueous solution. Such a barrier indicates that the designed iron complex is a promising low-cost catalyst for the formation of methanol from CO2 and H2 under mild conditions. The key role of the diphosphine ligand with pendent amine groups in the reaction is the assistance of the cleavage of H2 by forming a Fe-H(δ-) ⋅⋅⋅H(δ+) -N dihydrogen bond in a fashion of frustrated Lewis pairs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Biferrocene-Based Diphosphine Ligands: Synthesis and Application of Walphos Analogues in Asymmetric Hydrogenations

PubMed Central

2013-01-01

A total of four biferrocene-based Walphos-type ligands have been synthesized, structurally characterized, and tested in the rhodium-, ruthenium- and iridium-catalyzed hydrogenation of alkenes and ketones. Negishi coupling conditions allowed the biferrocene backbone of these diphosphine ligands to be built up diastereoselectively from the two nonidentical and nonracemic ferrocene fragments (R)-1-(N,N-dimethylamino)ethylferrocene and (SFc)-2-bromoiodoferrocene. The molecular structures of (SFc)-2-bromoiodoferrocene, the coupling product, two ligands, and the two complexes ([PdCl2(L)] and [RuCl(p-cymene)(L)]PF6) were determined by X-ray diffraction. The structural features of complexes and the catalysis results obtained with the newly synthesized biferrocene-based ligands were compared with those of the corresponding Walphos ligands. PMID:23457421

Competitive chiral induction in a 2D molecular assembly: Intrinsic chirality versus coadsorber-induced chirality.

PubMed

Chen, Ting; Li, Shu-Ying; Wang, Dong; Wan, Li-Jun

2017-11-01

Noncovalently introducing stereogenic information is a promising approach to embed chirality in achiral molecular systems. However, the interplay of the noncovalently introduced chirality with the intrinsic chirality of molecules or molecular aggregations has rarely been addressed. We report a competitive chiral expression of the noncovalent interaction-mediated chirality induction and the intrinsic stereogenic center-controlled chirality induction in a two-dimensional (2D) molecular assembly at the liquid/solid interface. Two enantiomorphous honeycomb networks are formed by the coassembly of an achiral 5-(benzyloxy)isophthalic acid (BIC) derivative and 1-octanol at the liquid/solid interface. The preferential formation of the globally homochiral assembly can be achieved either by using the chiral analog of 1-octanol, ( S )-6-methyl-1-octanol, as a chiral coadsorber to induce chirality to the BIC assembly via noncovalent hydrogen bonding or by covalently linking a chiral center in the side chain of BIC. Both the chiral coadsorber and the intrinsically chiral BIC derivative can act as a chiral seeds to induce a preferred handedness in the assembly of the achiral BIC derivatives. Furthermore, the noncovalent interaction-mediated chirality induction can restrain or even overrule the manifestation of the intrinsic chirality of the BIC molecule and dominate the handedness of the 2D molecular coassembly. This study provides insight into the interplay of intrinsically chiral centers and external chiral coadsorbers in the chiral induction, transfer, and amplification processes of 2D molecular assembly.

Competitive chiral induction in a 2D molecular assembly: Intrinsic chirality versus coadsorber-induced chirality

PubMed Central

Chen, Ting; Li, Shu-Ying; Wang, Dong; Wan, Li-Jun

2017-01-01

Noncovalently introducing stereogenic information is a promising approach to embed chirality in achiral molecular systems. However, the interplay of the noncovalently introduced chirality with the intrinsic chirality of molecules or molecular aggregations has rarely been addressed. We report a competitive chiral expression of the noncovalent interaction–mediated chirality induction and the intrinsic stereogenic center–controlled chirality induction in a two-dimensional (2D) molecular assembly at the liquid/solid interface. Two enantiomorphous honeycomb networks are formed by the coassembly of an achiral 5-(benzyloxy)isophthalic acid (BIC) derivative and 1-octanol at the liquid/solid interface. The preferential formation of the globally homochiral assembly can be achieved either by using the chiral analog of 1-octanol, (S)-6-methyl-1-octanol, as a chiral coadsorber to induce chirality to the BIC assembly via noncovalent hydrogen bonding or by covalently linking a chiral center in the side chain of BIC. Both the chiral coadsorber and the intrinsically chiral BIC derivative can act as a chiral seeds to induce a preferred handedness in the assembly of the achiral BIC derivatives. Furthermore, the noncovalent interaction–mediated chirality induction can restrain or even overrule the manifestation of the intrinsic chirality of the BIC molecule and dominate the handedness of the 2D molecular coassembly. This study provides insight into the interplay of intrinsically chiral centers and external chiral coadsorbers in the chiral induction, transfer, and amplification processes of 2D molecular assembly. PMID:29119137

Copper chalcogenide clusters stabilized with ferrocene-based diphosphine ligands.

PubMed

Khadka, Chhatra B; Najafabadi, Bahareh Khalili; Hesari, Mahdi; Workentin, Mark S; Corrigan, John F

2013-06-17

The redox-active diphosphine ligand 1,1'-bis(diphenylphosphino)ferrocene (dppf) has been used to stabilize the copper(I) chalcogenide clusters [Cu12(μ4-S)6(μ-dppf)4] (1), [Cu8(μ4-Se)4(μ-dppf)3] (2), [Cu4(μ4-Te)(μ4-η(2)-Te2)(μ-dppf)2] (3), and [Cu12(μ5-Te)4(μ8-η(2)-Te2)2(μ-dppf)4] (4), prepared by the reaction of the copper(I) acetate coordination complex (dppf)CuOAc (5) with 0.5 equiv of E(SiMe3)2 (E = S, Se, Te). Single-crystal X-ray analyses of complexes 1-4 confirm the presence of {Cu(2x)E(x)} cores stabilized by dppf ligands on their surfaces, where the bidentate ligands adopt bridging coordination modes. The redox chemistry of cluster 1 was examined using cyclic voltammetry and compared to the electrochemistry of the free ligand dppf and the corresponding copper(I) acetate coordination complex 5. Cluster 1 shows the expected consecutive oxidations of the ferrocene moieties, Cu(I) centers, and phosphine of the dppf ligand.

Chiral Gold Nanoclusters: Atomic Level Origins of Chirality.

PubMed

Zeng, Chenjie; Jin, Rongchao

2017-08-04

Chiral nanomaterials have received wide interest in many areas, but the exact origin of chirality at the atomic level remains elusive in many cases. With recent significant progress in atomically precise gold nanoclusters (e.g., thiolate-protected Au n (SR) m ), several origins of chirality have been unveiled based upon atomic structures determined by using single-crystal X-ray crystallography. The reported chiral Au n (SR) m structures explicitly reveal a predominant origin of chirality that arises from the Au-S chiral patterns at the metal-ligand interface, as opposed to the chiral arrangement of metal atoms in the inner core (i.e. kernel). In addition, chirality can also be introduced by a chiral ligand, manifested in the circular dichroism response from metal-based electronic transitions other than the ligand's own transition(s). Lastly, the chiral arrangement of carbon tails of the ligands has also been discovered in a very recent work on chiral Au 133 (SR) 52 and Au 246 (SR) 80 nanoclusters. Overall, the origins of chirality discovered in Au n (SR) m nanoclusters may provide models for the understanding of chirality origins in other types of nanomaterials and also constitute the basis for the development of various applications of chiral nanoparticles. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Brilliant Sm, Eu, Tb and Dy chiral lanthanide complexes withstrong circularly polarized luminescence

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

Petoud, Stephane; Muller, Gilles; Moore, Evan G.

The synthesis, characterization and luminescent behavior of trivalent Sm, Eu, Dy and Tb complexes of two enantiomeric, octadentate, chiral, 2-hydroxyisophthalamide ligands are reported. These complexes are highly luminescent in solution. Functionalization of the achiral parent ligand with a chiral 1-phenylethylamine substituent on the open face of the complex in close proximity to the metal center yields complexes with strong circularly polarized luminescence (CPL) activity. This appears to be the first example of a system utilizing the same ligand architecture to sensitize four different lanthanide cations and display CPL activity. The luminescence dissymmetry factor, g{sub lum}, recorded for the Eu(III) complexmore » is one of the highest values reported, and this is the first time the CPL effect has been demonstrated for a Sm(III) complex with a chiral ligand. The combination of high luminescence intensity with CPL activity should enable new bioanalytical applications of macromolecules in chiral environments.« less

Catalytic enantioselective synthesis of atropisomeric biaryls by a cation-directed O-alkylation

NASA Astrophysics Data System (ADS)

Jolliffe, John D.; Armstrong, Roly J.; Smith, Martin D.

2017-06-01

Axially chiral biaryls, as exemplified by 1,1‧-bi-2-naphthol (BINOL), are key components of catalysts, natural products and medicines. These materials are synthesized conventionally in enantioenriched form through metal-mediated cross coupling, de novo construction of an aromatic ring, point-to-axial chirality transfer or an atropselective transformation of an existing biaryl. Here, we report a highly enantioselective organocatalytic method for the synthesis of atropisomeric biaryls by a cation-directed O-alkylation. Treatment of racemic 1-aryl-2-tetralones with a chiral quinidine-derived ammonium salt under basic conditions in the presence of an alkylating agent leads to atropselective O-alkylation with e.r. up to 98:2. Oxidation with DDQ gives access to C2-symmetric and non-symmetric BINOL derivatives without compromising e.r. We propose that the chiral ammonium counterion differentiates between rapidly equilibrating atropisomeric enolates, leading to highly atropselective O-alkylation. This dynamic kinetic resolution process offers a general approach to the synthesis of enantioenriched atropisomeric materials.

Brilliant Sm, Eu, Tb, and Dy Chiral Lanthanide Complexes with Strong Circularly Polarized Luminescence

PubMed Central

Petoud, Stéphane; Muller, Gilles; Moore, Evan G.; Xu, Jide; Sokolnicki, Jurek; Riehl, James P.; Le, Uyen N.; Cohen, Seth M.; Raymond, Kenneth N.

2009-01-01

The synthesis, characterization, and luminescent behavior of trivalent Sm, Eu, Dy, and Tb complexes of two enantiomeric, octadentate, chiral, 2-hydroxyisophthalamide ligands are reported. These complexes are highly luminescent in solution. Functionalization of the achiral parent ligand with a chiral 1-phenylethylamine substituent on the open face of the complex in close proximity to the metal center yields complexes with strong circularly polarized luminescence (CPL) activity. This appears to be the first example of a system utilizing the same ligand architecture to sensitize four different lanthanide cations and display CPL activity. The luminescence dissymmetry factor, glum, recorded for the Eu(III) complex is one of the highest values reported, and this is the first time the CPL effect has been demonstrated for a Sm(III) complex with a chiral ligand. The combination of high luminescence intensity with CPL activity should enable new bioanalytical applications of macromolecules in chiral environments. PMID:17199285

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.

Gelation induced supramolecular chirality: chirality transfer, amplification and application.

PubMed

Duan, Pengfei; Cao, Hai; Zhang, Li; Liu, Minghua

2014-08-14

Supramolecular chirality defines chirality at the supramolecular level, and is generated from the spatial arrangement of component molecules assembling through non-covalent interactions such as hydrogen bonding, van der Waals interactions, π-π stacking, hydrophobic interactions and so on. During the formation of low molecular weight gels (LMWGs), one kind of fascinating soft material, one frequently encounters the phenomenon of chirality as well as chiral nanostructures, either from chiral gelators or even achiral gelators. A view of gelation-induced supramolecular chirality will be very helpful to understand the self-assembly process of the gelator molecules as well as the chiral structures, the regulation of the chirality in the gels and the development of the "smart" chiral materials such as chiroptical devices, catalysts and chiral sensors. It necessitates fundamental understanding of chirality transfer and amplification in these supramolecular systems. In this review, recent progress in gelation-induced supramolecular chirality is discussed.

Chiral Separations

NASA Astrophysics Data System (ADS)

Stalcup, A. M.

2010-07-01

The main goal of this review is to provide a brief overview of chiral separations to researchers who are versed in the area of analytical separations but unfamiliar with chiral separations. To researchers who are not familiar with this area, there is currently a bewildering array of commercially available chiral columns, chiral derivatizing reagents, and chiral selectors for approaches that span the range of analytical separation platforms (e.g., high-performance liquid chromatography, gas chromatography, supercritical-fluid chromatography, and capillary electrophoresis). This review begins with a brief discussion of chirality before examining the general strategies and commonalities among all of the chiral separation techniques. Rather than exhaustively listing all the chiral selectors and applications, this review highlights significant issues and differences between chiral and achiral separations, providing salient examples from specific classes of chiral selectors where appropriate.

Counteranion Driven Homochiral Assembly of a Cationic C3-Symmetric Gelator through Ion-Pair Assisted Hydrogen Bond.

PubMed

Maity, Arunava; Gangopadhyay, Monalisa; Basu, Arghya; Aute, Sunil; Babu, Sukumaran Santhosh; Das, Amitava

2016-09-07

The helical handedness in achiral self-assemblies is mostly complex due to spontaneous symmetry breaking or kinetically controlled random assembly formation. Here an attempt has been made to address this issue through chiral anion exchange. A new class of cationic achiral C3-symmetric gelator devoid of any conventional gelation assisting functional units is found to form both right- and left-handed helical structures. A chiral counteranion exchange-assisted approach is successfully introduced to control the chirality sign and thereby to obtain preferred homochiral assemblies. Formation of anion-assisted chiral assembly was confirmed by circular dichroism (CD) spectroscopy, microscopic images, and crystal structure. The X-ray crystal structure reveals the construction of helical assemblies with opposite handedness for (+)- and (-)-chiral anion reformed gelators. The appropriate counteranion driven ion-pair-assisted hydrogen-bonding interactions are found responsible for the helical bias control in this C3-symmetric gelator.

Electric field effects on nuclear magnetic shielding of the 1:1 and 2:1 (homo and heterochiral) complexes of XOOX' (X, X' = H, CH3) with lithium cation and their chiral discrimination.

PubMed

Alkorta, Ibon; Elguero, José; Provasi, Patricio F; Pagola, Gabriel I; Ferraro, Marta B

2011-09-14

The set of 1:1 and 2:1 complexes of XOOX' (X, X' = H, CH(3)) with lithium cation has been studied to determine if they are suitable candidates for chiral discrimination in an isotropic medium via nuclear magnetic resonance spectroscopy. Conventional nuclear magnetic resonance is unable to distinguish between enantiomers in the absence of a chiral solvent. The criterion for experimental detection is valuated by the isotropic part of nuclear shielding polarisability tensors, related to a pseudoscalar of opposite sign for two enantiomers. The study includes calculations at coupled Hartree-Fock and density functional theory schemes for (17)O nucleus in each compound. Additional calculations for (1)H are also included for some compounds. A huge static homogeneous electric field, perpendicular to the magnetic field of the spectromer, as big as ≈1.7 × 10(8) V m(-1) should be applied to observe a shift of ≈1 ppm for (17)O magnetic shielding in the proposed set of complexes. © 2011 American Institute of Physics

Phosphinocyclodextrins as confining units for catalytic metal centres. Applications to carbon–carbon bond forming reactions

PubMed Central

Jouffroy, Matthieu; Gramage-Doria, Rafael; Sémeril, David; Oberhauser, Werner; Toupet, Loïc

2014-01-01

Summary The capacity of two cavity-shaped ligands, HUGPHOS-1 and HUGPHOS-2, to generate exclusively singly phosphorus-ligated complexes, in which the cyclodextrin cavity tightly wraps around the metal centre, was explored with a number of late transition metal cations. Both cyclodextrin-derived ligands were assessed in palladium-catalysed Mizoroki–Heck coupling reactions between aryl bromides and styrene on one hand, and the rhodium-catalysed asymmetric hydroformylation of styrene on the other hand. The inability of both chiral ligands to form standard bis(phosphine) complexes under catalytic conditions was established by high-pressure NMR studies and shown to have a deep impact on the two carbon–carbon bond forming reactions both in terms of activity and selectivity. For example, when used as ligands in the rhodium-catalysed hydroformylation of styrene, they lead to both high isoselectivity and high enantioselectivity. In the study dealing with the Mizoroki–Heck reactions, comparative tests were carried out with WIDEPHOS, a diphosphine analogue of HUGPHOS-2. PMID:25383109

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.

Bite angle effects of diphosphines in C-C and C-X bond forming cross coupling reactions.

PubMed

Birkholz, Mandy-Nicole; Freixa, Zoraida; van Leeuwen, Piet W N M

2009-04-01

Catalytic reactions of C-C and C-X bond formation are discussed in this critical review with particular emphasis on cross coupling reactions catalyzed by palladium and wide bite angle bidentate diphosphine ligands. Especially those studies have been collected that allow comparison of the ligand bite angles for the selected ligands: dppp, BINAP, dppf, DPEphos and Xantphos. Similarities with hydrocyanation and CO/ethene/MeOH reactions have been highlighted, while rhodium hydroformylation has been mentioned as a contrasting example, in which predictability is high and steric and electronic effects follow smooth trends. In palladium catalysis wide bite angles and bulkiness of the ligands facilitate generally the reductive elimination thus giving more efficient cross coupling catalysis (174 references).

Hydrogenation of CO 2 in Water Using a Bis(diphosphine) Ni–H Complex

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

Burgess, Samantha A.; Kendall, Alexander J.; Tyler, David R.

2017-03-17

The water soluble Ni bis(diphosphine) complex [NiL2](BF4)2 (L = 1,2- bis(di(methoxypropyl)phosphino)ethane) and the corresponding hydride, [HNiL2]BF4, were synthesized and characterized. For HNiL2+, the hydricity was determined to be 23.2(3) kcal/mol in aqueous solution. Based on the hydricity of formate of 24.1 kcal/mol, the transfer of a hydride from HNiL2 + to CO2 to produce formate is favorable by 1 kcal/mol. Starting from either NiL2 2+ or HNiL2 + in water, catalytic hydrogenation of CO2 was observed with NaHCO3 (0.8 M) as the only additive. A maximum turnover frequency of 3.6(8) h–1 was observed at 80 °C and 51 atm ofmore » a 1:1 mixture of CO2 and H2.« less

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.

Chiral Recognition and Separation by Chirality-Enriched Metal-Organic Frameworks.

PubMed

Das, Saikat; Xu, Shixian; Ben, Teng; Qiu, Shilun

2018-05-16

Endowed with chiral channels and pores, chiral metal-organic frameworks (MOFs) are highly useful; however, their synthesis remains a challenge given that most chiral building blocks are expensive. Although MOFs with induced chirality have been reported to avoid this shortcoming, no study providing evidence for the ee value of such MOFs has yet been reported. We herein describe the first study on the efficiency of chiral induction in MOFs using inexpensive achiral building blocks and fully recoverable chiral dopants to control the handedness of racemic MOFs. This method yielded chirality-enriched MOFs with accessible pores. The ability of the materials to form host-guest complexes was probed with enantiomers of varying size and coordination and in solvents with varying polarity. Furthermore, mixed-matrix membranes (MMMs) composed of chirality-enriched MOF particles dispersed in a polymer matrix demonstrated a new route for chiral separation. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Diphosphine is an intermediate in the photolysis of phosphine to phosphorus and hydrogen. [Jupiter atmospheric chemistry

NASA Technical Reports Server (NTRS)

Ferris, J. P.; Benson, R.

1980-01-01

The photolysis of phosphine to red phosphorus (P4) and hydrogen is investigated in light of the potential significance of the reaction in the atmospheric chemistry of Jupiter. It is reported that the photolysis of PH3 at room temperature by a 206.2-nm light source gave rise to a product identified by its UV and IR spectra and gas chromatographic retention time as P2H4, the yield of which is found to increase to a maximum and then decrease to 20% of the maximum value with illumination time. A mechanism for phosphine photolysis including diphosphine formation as an intermediate step is proposed, and it is concluded that P2H4 is a likely constituent of the atmospheres of the Jovian planets.

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)

Chiral acidic amino acids induce chiral hierarchical structure in calcium carbonate

PubMed Central

Jiang, Wenge; Pacella, Michael S.; Athanasiadou, Dimitra; Nelea, Valentin; Vali, Hojatollah; Hazen, Robert M.; Gray, Jeffrey J.; McKee, Marc D.

2017-01-01

Chirality is ubiquitous in biology, including in biomineralization, where it is found in many hardened structures of invertebrate marine and terrestrial organisms (for example, spiralling gastropod shells). Here we show that chiral, hierarchically organized architectures for calcium carbonate (vaterite) can be controlled simply by adding chiral acidic amino acids (Asp and Glu). Chiral, vaterite toroidal suprastructure having a ‘right-handed' (counterclockwise) spiralling morphology is induced by L-enantiomers of Asp and Glu, whereas ‘left-handed' (clockwise) morphology is induced by D-enantiomers, and sequentially switching between amino-acid enantiomers causes a switch in chirality. Nanoparticle tilting after binding of chiral amino acids is proposed as a chiral growth mechanism, where a ‘mother' subunit nanoparticle spawns a slightly tilted, consequential ‘daughter' nanoparticle, which by amplification over various length scales creates oriented mineral platelets and chiral vaterite suprastructures. These findings suggest a molecular mechanism for how biomineralization-related enantiomers might exert hierarchical control to form extended chiral suprastructures. PMID:28406143

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.

Electric line source illumination of a chiral cylinder placed in another chiral background medium

NASA Astrophysics Data System (ADS)

Aslam, M.; Saleem, A.; Awan, Z. A.

2018-05-01

An electric line source illumination of a chiral cylinder embedded in a chiral background medium is considered. The field expressions inside and outside of a chiral cylinder have been derived using the wave field decomposition approach. The effects of various chiral cylinders, chiral background media and source locations upon the scattering gain pattern have been investigated. It is observed that the chiral background reduces the backward scattering gain as compared to the free space background for a dielectric cylinder. It is also studied that by moving a line source away from a cylinder reduces the backward scattering gain for a chiral cylinder placed in a chiral background under some specific conditions. A unique phenomenon of reduced scattering gain has been observed at a specific observation angle for a chiral cylinder placed in a chiral background having an electric line source location of unity free space wavelength. An isotropic scattering gain pattern is observed for a chiral nihility background provided that if cylinder is chiral or chiral nihility type. It is also observed that this isotropic behaviour is independent of background and cylinder chirality.

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.

Syntheses and structures of ruthenium(II) N,S-heterocyclic carbene diphosphine complexes and their catalytic activity towards transfer hydrogenation.

PubMed

Ding, Nini; Hor, T S Andy

2011-06-06

Phosphine exchange of [Ru(II) Br(MeCOO)(PPh(3))(2)(3-RBzTh)] (3-RBzTh=3-benzylbenzothiazol-2-ylidene) with a series of diphosphines (bis(diphenylphosphino)methane (dppm), 1,2-bis(diphenylphosphino)ethylene (dppv), 1,1'-bis(diphenylphosphino)ferrocene (dppf), 1,4-bis(diphenylphosphino)butane (dppb), and 1,3-(diphenylphosphino)propane (dppp)) gave mononuclear and neutral octahedral complexes [RuBr(MeCOO)(η(2)-P(2))(3-RBzTh)] (P(2)=dppm (2), dppv (3), dppf (4), dppb (5), or dppp (6)), the coordination spheres of which contained four different ligands, namely, a chelating diphosphine, carboxylate, N,S-heterocyclic carbene (NSHC), and a bromide. Two geometric isomers of 6 (6a and 6b) have been isolated. The structures of these products, which have been elucidated by single-crystal X-ray crystallography, show two structural types, I and II, depending on the relative dispositions of the ligands. Type I structures contain a carbenic carbon atom trans to the oxygen atom, whereas two phosphorus atoms are trans to bromine and oxygen atoms. The type II system comprises a carbene carbon atom trans to one of the phosphorus atoms, whereas the other phosphorus is trans to the oxygen atom, with the bromine trans to the remaining oxygen atom. Complexes 2, 3, 4, and 6a belong to type I, whereas 5 and 6b are of type II. The kinetic product 6b eventually converts into 6a upon standing. These complexes are active towards catalytic reduction of para-methyl acetophenone by 2-propanol at 82 °C under 1% catalyst load giving the corresponding alcohols. The dppm complex 2 shows the good yields (91-97%) towards selected ketones. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

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.

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

Can a Non-Chiral Object Be Made of Two Identical Chiral Moieties?

ERIC Educational Resources Information Center

LeMarechal, Jean Francois

2008-01-01

Several pedagogical objects can be used to discuss chirality. Here, we use the cut of an apple to show that the association of identical chiral moieties can form a non-chiral object. Octahedral chirality is used to find situations equivalent to the cut of the apple. (Contains 5 figures.)

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.

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

Eu2P7X and Ba2As7X (X = Br, I): Chiral double-Zintl salts containing heptapnictotricyclane clusters

NASA Astrophysics Data System (ADS)

Dolyniuk, Juli-Anna; Lee, Shannon; Tran, Nhon; Wang, Jian; Wang, Lin-Lin; Kovnir, Kirill

2018-07-01

Chiral double Zintl salts present tunable crystal structures with enhanced structural flexibilities and potential for applications requiring chiral control and enantioselectivity. To accompany the chiral Sr2P7I and Sr2P7Br double Zintl salts reported by us previously, six new chiral Zintl salts of the form Ba2-ySryAs7I (y = 0, 0.23, 2), Eu2P7I, Eu2P7Br, and Eu1.3Ba0.7P7Br have been synthesized and characterized by single crystal X-ray diffraction and SEM-EDS analyses. All new compounds crystallize in the Sohncke space group P213 (No. 198) with variations of P73- (heptaphosphanortricyclane) or As73- (heptaarsanortricyclane) clusters surrounded by alkaline-earth or Eu cations and halogen anions. Band structure calculations predict semiconducting properties for all synthesized compounds. Diffuse reflectance UV-vis spectroscopy indicates that Eu2P7I is a direct bandgap semiconductor with Eg of 1.7 eV.

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.

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

Chiral supramolecular organization from a sheet-like achiral gel: a study of chiral photoinduction.

PubMed

Royes, Jorge; Polo, Víctor; Uriel, Santiago; Oriol, Luis; Piñol, Milagros; Tejedor, Rosa M

2017-05-31

Chiral photoinduction in a photoresponsive gel based on an achiral 2D architecture with high geometric anisotropy and low roughness has been investigated. Circularly polarized light (CPL) was used as a chiral source and an azobenzene chromophore was employed as a chiral trigger. The chiral photoinduction was studied by evaluating the preferential excitation of enantiomeric conformers of the azobenzene units. Crystallographic data and density functional theory (DFT) calculations show how chirality is transferred to the achiral azomaterials as a result of the combination of chiral photochemistry and supramolecular interactions. This procedure could be applied to predict and estimate chirality transfer from a chiral physical source to a supramolecular organization using different light-responsive units.

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.

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.

Synthesis and redox properties of fac-BrRe(CO)3[1,2-(PPh2)2-closo-1,2-C2B10H10]: The first structurally characterized rhenium carbonyl containing a carboranyl-based diphosphine ligand

NASA Astrophysics Data System (ADS)

Lin, Chen-Hao; Nesterov, Vladimir N.; Richmond, Michael G.

2018-03-01

The diphosphine 1,2-(PPh2)2-closo-1,2-C2B10H10 reacts with BrRe(CO)5 and fac-BrRe(CO)3(THF)2 to give fac-BrRe(CO)3[1,2-(PPh2)2-closo-1,2-C2B10H10] (1) in high yields (>80%). Compound 1 is the first structurally characterized rhenium carbonyl that contains an ancillary carborane-based diphosphine ligand. 1 has been characterized in solution by IR and NMR spectroscopies (1H and 31P), and the solid-state structure has been determined by X-ray diffraction analysis. The electrochemical properties of 1 have been investigated by cyclic voltammetry, and the composition of the DFT-computed HOMO and LUMO levels are discussed relative to the electrochemical data. The thermodynamics for the formation of 1 from the rhenium precursors BrRe(CO)5 and fac-BrRe(CO)3(THF)2 have been evaluated by DFT calculations.

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.

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.

Nonbonded interactions in membrane active cyclic biopolymers. IV - Cation dependence

NASA Technical Reports Server (NTRS)

Radhakrishnan, R.; Srinivasan, S.; Prasad, C. V.; Brinda, S. R.; Macelroy, R. D.; Sundaram, K.

1980-01-01

Interactions of valinomycin and form of its analogs in several conformations with the central ions Li(+), Na(+), K(+), Rb(+) and Cs(+) are investigated as part of a study of the specific preference of valinomycin for potassium and the mechanisms of carrier-mediated ion transport across membranes. Ion binding energies and conformational potential energies are calculated taking into account polarization energy formulas and repulsive energy between the central ion and the ligand atoms for conformations representing various stages in ion capture and release for each of the two ring chiralities of valinomycin and its analogs. Results allow the prediction of the chirality and conformation most likely to be observed for a given analog, and may be used to synthesize analogs with a desired rigidity or flexibility. The binding energies with the alkali metal cations are found to decrease with increasing ion size, and to be smaller than the corresponding ion hydration energies. It is pointed out that the observed potassium preference may be explainable in terms of differences between binding and hydration energies. Binding energies are also noted to depend on ligand conformation.

Colloidal chirality in wormlike micellar systems exclusively originated from achiral species: Role of secondary assembly and stimulus responsivity.

PubMed

Zhao, Wenrong; Hao, Jingcheng

2016-09-15

Colloidal chirality in wormlike micellar systems exclusively originated from achiral species and discussion of the role of secondary assembly of fiber-like aggregates in chirality generation were presented in this paper. Herein, formation of colloidal wormlike micelles for the first time incorporated chirality and redox-responsiveness into one design via noncovalent interaction. A dual-stimuli-responsive gel of wormlike micelles which were designed by employing a dual-responsive cationic surfactant (FTMA) and a strong gelator (AzoNa4) and regulated by redox reaction and host-guest inclusion is presented. Both the redox and host-guest interaction play an important role in regulating the viscosity and supramolecular chirality of gels of the wormlike micelles. The supramolecular chirality and viscosity of the wormlike micelle gels were switched reversibly by exerting chemical redox onto the ferrocenyl groups. For the amphiphile FTMA containing redox-active ferrocenyl group, reversible control of the oxidation state of ferrocenyl groups leads to the charge and hydrophobicity changes of FTMA, therefore change its self-assembly behavior. Of equal interest, β-CD successfully detached the wormlike micelles via the recognition-inclusion behavior with FTMA and invalidate the H-bond and hydrophobic interaction between FTMA and AzoH4. This designed system provides a new strategy to tune the supramolecular chirality of colloidal aggregates and explore the specific packing mode detail within the micelles or the secondary assembly of the inter-micelles. We anticipate this dual-responsive H-bond-directed chiral gel switch could propose a new strategy when researchers designing new, multi-responsive functional gel materials. Copyright © 2016 Elsevier Inc. All rights reserved.

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.

Chirality in adsorption on solid surfaces.

PubMed

Zaera, Francisco

2017-12-07

In the present review we survey the main advances made in recent years on the understanding of chemical chirality at solid surfaces. Chirality is an important topic, made particularly relevant by the homochiral nature of the biochemistry of life on Earth, and many chiral chemical reactions involve solid surfaces. Here we start our discussion with a description of surface chirality and of the different ways that chirality can be bestowed on solid surfaces. We then expand on the studies carried out to date to understand the adsorption of chiral compounds at a molecular level. We summarize the work published on the adsorption of pure enantiomers, of enantiomeric mixtures, and of prochiral molecules on chiral and achiral model surfaces, especially on well-defined metal single crystals but also on other flat substrates such as highly ordered pyrolytic graphite. Several phenomena are identified, including surface reconstruction and chiral imprinting upon adsorption of chiral agents, and the enhancement or suppression of enantioselectivity seen in some cases upon adsorption of enantiomixtures of chiral compounds. The possibility of enhancing the enantiopurity of adsorbed layers upon the addition of chiral seeds and the so-called "sergeants and soldiers" phenomenon are presented. Examples are provided where the chiral behavior has been associated with either thermodynamic or kinetic driving forces. Two main approaches to the creation of enantioselective surface sites are discussed, namely, via the formation of supramolecular chiral ensembles made out of small chiral adsorbates, and by adsorption of more complex chiral molecules capable of providing suitable chiral environments for reactants by themselves, via the formation of individual adsorbate:modifier adducts on the surface. Finally, a discussion is offered on the additional effects generated by the presence of the liquid phase often required in practical applications such as enantioselective crystallization, chiral

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.

Chiral Magnetic Effect in Condensed Matters

NASA Astrophysics Data System (ADS)

Li, Qiang

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 chiral anomaly 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 the 3D Dirac and Weyl semimetals having a linear dispersion relation. Recently, the chiral magnetic effect was discovered in a 3D Dirac semimetal - zirconium pentatelluride, ZrTe5, in which a large negative magnetoresistance is observed when magnetic field is parallel with the current. It is now reported in more than a dozen Dirac and Weyl semimetals. Broadly speaking, the chiral magnetic effect can exist in a variety of condensed matters. In some cases, a material may be transformed into a Weyl semimetal by magnetic field, exhibiting the chiral magnetic effect. In other cases, the chiral magnetic current may be generated in magnetic Dirac semimetals without external magnetic field, or in asymmetric Weyl semimetals without electric field where only a magnetic field and the source of chiral quasipartiles would be necessary. In the limit of conserved quasiparticle chirality, charge transport by the chiral magnetic current is non-dissipative. The powerful notion of chirality, originally discovered in high-energy and nuclear physics, holds promise in new ways of transmitting and processing information and energy. At the same time, chiral materials have opened a fascinating possibility to study the quantum dynamics of relativistic field theory in condensed matter experiments.

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.

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.

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.

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.

Meta-Chirality: Fundamentals, Construction and Applications

PubMed Central

Ma, Xiaoliang; Pu, Mingbo; Li, Xiong; Guo, Yinghui; Gao, Ping; Luo, Xiangang

2017-01-01

Chiral metamaterials represent a special type of artificial structures that cannot be superposed to their mirror images. Due to the lack of mirror symmetry, cross-coupling between electric and magnetic fields exist in chiral mediums and present unique electromagnetic characters of circular dichroism and optical activity, which provide a new opportunity to tune polarization and realize negative refractive index. Chiral metamaterials have attracted great attentions in recent years and have given rise to a series of applications in polarization manipulation, imaging, chemical and biological detection, and nonlinear optics. Here we review the fundamental theory of chiral media and analyze the construction principles of some typical chiral metamaterials. Then, the progress in extrinsic chiral metamaterials, absorbing chiral metamaterials, and reconfigurable chiral metamaterials are summarized. In the last section, future trends in chiral metamaterials and application in nonlinear optics are introduced. PMID:28513560

New rhenium(I) compounds containing the donor-acceptor diphosphine ligands 2-(ferrocenylidene)-4,5-bis(diphenylphosphino)4-cyclopenten-1,3-dione (fbpcd) and 2-(3-ferrocenylprop-2-ynylidene)-4,5-bis(diphenylphosphino)4-cyclopenten-1,3-dione (fpbpcd): Electrochemical behavior, MO properties, and X-ray diffraction structure of fac-BrRe(CO)(3)(fpbpcd)

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

Poola, Bhaskar; Richmond, Michael G.

2009-01-01

Displacement of the labile THF molecules in BrRe(CO){sub 3}(THF){sub 2} (1) by the diphosphine ligands 2-(ferrocenylidene)-4,5-bis(diphenylphosphino)4-cyclopenten-1,3-dione (fbpcd) and 2-(3-ferrocenylprop-2-ynylidene)-4,5-bis(diphenylphosphino)4-cyclopenten- 1,3-dione (fpbpcd) yields the mononuclear compounds fac-BrRe(CO){sub 3}(fbpcd) (2) and fac-BrRe(CO){sub 3}(fpbpcd) (3), respectively. The new ligand fpbpcd ligand has been synthesized from 3-ferrocenylpropynal and the parent diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) through a Knoevenagel condensation. 2 and 3 have been isolated and fully characterized by IR and NMR spectroscopies ({sup 1}H and {sup 31}P), ESI mass spectrometry, and X-ray diffraction analysis in the case of 3. The electrochemical properties of compounds 2 and 3 have been examined by cyclic voltammetry, andmore » the nature of the HOMO and LUMO levels in these systems has been confirmed by MO calculations at the extended Hueckel level. The redox and MO data are discussed relative to the redox and orbital properties of related functionalized diphosphines based on the bpcd platform.« less

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.

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.

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.

Molecular structure of self-assembled chiral nanoribbons and nanotubules revealed in the hydrated state.

PubMed

Oda, Reiko; Artzner, Franck; Laguerre, Michel; Huc, Ivan

2008-11-05

A detailed molecular organization of racemic 16-2-16 tartrate self-assembled multi-bilayer ribbons in the hydrated state is proposed where 16-2-16 amphiphiles, tartrate ions, and water molecules are all accurately positioned by comparing experimental X-ray powder diffraction and diffraction patterns derived from modeling studies. X-ray diffuse scattering studies show that molecular organization is not fundamentally altered when comparing the flat ribbons of the racemate to chirally twisted or helical ribbons of the pure tartrate enantiomer. Essential features of the three-dimensional molecular organizations of these structures include interdigitation of alkyl chains within each bilayer and well-defined networks of ionic and hydrogen bonds between cations, anions, and water molecules between bilayers. The detailed study of diffraction patterns also indicated that the gemini headgroups are oriented parallel to the long edge of the ribbons. The structure thus possesses a high cohesion and good crystallinity, and for the first time, we could relate the packing of the chiral molecules to the expression of the chirality at a mesoscopic scale. The organization of the ribbons at the molecular level sheds light on a number of their macroscopic features. Among these are the reason why enantiomerically pure 16-2-16 tartrate forms ribbons that consist of exactly two bilayers, and a plausible mechanism by which a chirally twisted or helical shape may emerge from the packing of chiral tartrate ions. Importantly, the distinction between commonly observed helical and twisted morphologies could be related to a subtle symmetry breaking. These results demonstrate that accurately solving the molecular structure of self-assembled soft materials--a process rarely achieved--is within reach, that it is a valid approach to correlate molecular parameters to macroscopic properties, and thus that it offers opportunities to modulate properties through molecular design.

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.

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.

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.

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.

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.

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.

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.

Comparison of Positively and Negatively Charged Achiral Co-Monomers Added to Cyclodextrin Monolith: Improved Chiral Separations in Capillary Electrochromatography

PubMed Central

Lu, Yang; Shamsi, Shahab A.

2014-01-01

Cyclodextrins (CDs) and their derivatives have been one of the most popular and successful chiral additives used in electrokinetic chromatography because of the presence of multiple chiral centers, which leads to multiple chiral interactions. However, there has been relatively less published work on the use of CDs as monolithic media for capillary electrochromatography (CEC). The goal of this study was to show how the addition of achiral co-monomer to a polymerizable CD such as glycidyl methacrylate β-cyclodextrin (GMA/β-CD) can affect the enantioselective separations in monolithic CEC. To achieve this goal, polymeric monoliths columns were prepared by co-polymerizing GMA/β-CD with cationic or anionic achiral co-monomers [(2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and vinyl benzyltrimethyl-ammonium (VBTA)] in the presence of conventional crosslinker (ethylene dimethacrylate) and ternary porogen system including butanediol, propanol and water. A total of 34 negatively charged compounds, 30 positively charged compounds and 33 neutral compounds were screened to compare the enantioresolution capability on the GMA/β-CD, GMA/β-CD-VBTA and GMA/β-CD-AMPS monolithic columns. PMID:24108813

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.

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.

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.

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.

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

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.

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.

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

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

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.

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

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.

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.

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.

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.

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.

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

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.

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.

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

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.

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

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.

Electronic structure of monodentate-coordinated diphosphine complexes. Photoelectron spectra of Mo(CO)[sub 5](P(CH[sub 3])[sub 2]CH[sub 2]P(CH[sub 3])[sub 2]) and Mo(CO)[sub 5](P(CH[sub 3])[sub 2]CH[sub 2]CH[sub 2]P(CH[sub 3])[sub 2])

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

Lichtenberger, D.L.; Jatcko, M.E.

1992-02-05

Photoelectron spectroscopy is used to study the electronic structure of molybdenum carbonyl complexes that contain diphosphine ligands bound to the metal through only one of the two phosphorus atoms. Photoelectron spectra are reported for Mo(CO)[sub 5]DMPE and Mo(CO)[sub 5]DMPM and compared to the spectra of Mo(CO)[sub 5]PMe[sub 3] and the corresponding free phosphine and diphosphine ligands (PMe[sub 3] is trimethylphosphine, DMPE is 1,2-bis(dimethylphosphino)ethane, and DMPM is bis(dimethylphosphino)methane). The energy splittings between the d[sup 6] metal-based ionizations of these complexes indicate that the [pi]-back-bonding ability is the same for each of these phosphine ligands and is relatively small, about 25% thatmore » of carbon monoxide. The metal-based ionizations shift only slightly to lower binding energy from the PMe[sub 3] to the DMPE to the DMPM complex due to a slightly increasing negative charge potential at the metal along this series. This would normally be interpreted as slightly increasing [sigma]-donor strength in the order PMe[sub 3] < DMPE < DMPM. However, the difference between the ionization energy of the coordinated lone pair (CLP) of the phosphine and the ionization energy of the lone pair of the free ligand indicates an opposite trend in [sigma]-donor strength with PMe[sub 3] (1.28 eV) > DMPE (1.27 eV) > DMPM (1.23 eV). The shift of the uncoordinated phosphine lone-pair ionization (ULP) of the monocoordinated diphosphine complexes, which is affected primarily by charge potential effects, reveals that the important factor is a transfer of negative charge from the uncoordinated end of the phosphine through the alkyl linkage to the coordinated phosphine. Aside from these subtle details of charge distribution, the primary conclusion is that the diphosphine ligands, DMPE and DMPM, have [sigma]-donor and [pi]-acceptor strengths extremely similar to those of PMe[sub 3].« less

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.

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.

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.

Triple Halide Bridges in Chiral MnII2MnIII6NaI2 Cages: Structural and Magnetic Characterization.

PubMed

Mayans, Júlia; Font-Bardia, Mercè; Escuer, Albert

2018-02-05

A family of decanuclear chiral clusters with a Mn II 2 Mn III 6 Na I 2 core have been synthesized from enantiomerically pure Schiff bases. The new systems consist of two Mn II Mn III 3 Na I units linked by rare triple chloro or bromo bridges between the divalent Mn cations. Susceptibility measurements point out the weak antiferromagnetic interaction mediated by these kinds of bridges and afford the first magnetic measurements for the (μ-Br) 3 case.

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

The synthesis and structure of a chiral 1D aluminophosphate chain compound: d-Co(en) 3[AlP 2O 8]·6.5H 2O

NASA Astrophysics Data System (ADS)

Chen, Peng; Li, Jiyang; Yu, Jihong; Wang, Yu; Pan, Qinhe; Xu, Ruren

2005-06-01

A new chiral one-dimensional (1D) aluminophosphate chain compound [ d-Co(en) 3][AlP 2O 8]·6.5H 2O (designated AlPO-CJ22) has been hydrothermally synthesized by using the optically pure d-Co(en) 3I 3 complex as the template. Single-crystal structural analysis reveals that its structure is built up from alternating connection of AlO 4 and PO 2(=O 2) tetrahedra to form corner-shared Al 2P 2 four-membered ring (4-MR) chains. The d-Co(en) 33+ complex cations extended along the 2 1 screw axis interact with the inorganic chains through hydrogen-bonds of N⋯O atoms in a helical fashion. Optical rotation measurement shows that AlPO-CJ22 is chiral as with d-Co(en) 33+ complex cations. Crystal data: orthorhombic, I2 12 12 1, a=8.5573(8) Å, b=22.613(2) Å, c=22.605(2) Å, Z=8, R1=0.067, wR2=0.1291, and Flack parameter: -0.02(3). CCDC number: 254179.

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.

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.

Chiral Graphene Quantum Dots

DOE PAGES

Suzuki, Nozomu; Wang, Yichun; Elvati, Paolo; ...

2016-01-15

Chiral nanostructures from metals and semiconductors attract wide interest as components for polarization-enabled optoelectronic devices. Similarly to other fields of nanotechnology, graphene-based materials can greatly enrich physical and chemical phenomena associated with optical and electronic properties of chiral nanostructures and facilitate their applications in biology as well as other areas. Here, we report that covalent attachment of l/d-cysteine moieties to the edges of graphene quantum dots (GQDs) leads to their helical buckling due to chiral interactions at the “crowded” edges. Circular dichroism (CD) spectra of the GQDs revealed bands at ca. 210–220 and 250–265 nm that changed their signs formore » different chirality of the cysteine edge ligands. The high-energy chiroptical peaks at 210–220 nm correspond to the hybridized molecular orbitals involving the chiral center of amino acids and atoms of graphene edges. Diverse experimental and modeling data, including density functional theory calculations of CD spectra with probabilistic distribution of GQD isomers, indicate that the band at 250–265 nm originates from the three-dimensional twisting of the graphene sheet and can be attributed to the chiral excitonic transitions. The positive and negative low-energy CD bands correspond to the left and right helicity of GQDs, respectively. Exposure of liver HepG2 cells to l/d-GQDs reveals their general biocompatibility and a noticeable difference in the toxicity of the stereoisomers. Molecular dynamics simulations demonstrated that d-GQDs have a stronger tendency to accumulate within the cellular membrane than l-GQDs. Finally, emergence of nanoscale chirality in GQDs decorated with biomolecules is expected to be a general stereochemical phenomenon for flexible sheets of nanomaterials.« 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

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.

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...

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

Rhodium-Catalyzed Asymmetric N-H Functionalization of Quinazolinones with Allenes and Allylic Carbonates: The First Enantioselective Formal Total Synthesis of (-)-Chaetominine.

PubMed

Zhou, Yirong; Breit, Bernhard

2017-12-22

An unprecedented asymmetric N-H functionalization of quinazolinones with allenes and allylic carbonates was successfully achieved by rhodium catalysis with the assistance of chiral bidentate diphosphine ligands. The high efficiency and practicality of this method was demonstrated by a low catalyst loading of 1 mol % as well as excellent chemo-, regio-, and enantioselectivities with broad functional group compatibility. Furthermore, this newly developed strategy was applied as key step in the first enantioselective formal total synthesis of (-)-chaetominine. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

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.

Enhancing and reducing chirality by opposite circularly-polarized light irradiation on crystalline chiral domains consisting of nonchiral photoresponsive W-shaped liquid crystal molecules.

PubMed

Choi, Suk-Won; Takezoe, Hideo

2016-09-28

We found possible chirality enhancement and reduction in chiral domains formed by photoresponsive W-shaped molecules by irradiation with circularly polarized light (CPL). The W-shaped molecules exhibit a unique smectic phase with spontaneously segregated chiral domains, although the molecules are nonchiral. The chirality control was generated in the crystalline phase, which shows chiral segregation as in the upper smectic phase, and the result appeared to be as follows: for a certain chiral domain, right-CPL stimuli enhanced the chirality, while left-CPL stimuli reduced the chirality, and vice versa for another chiral domain. Interestingly, no domain-size change could be observed after CPL irradiation, suggesting some changes in the causes of chirality. In this way, the present system can recognize the handedness of the applied chiral stimuli. In other words, the present material can be used as a sensitive chiral-stimuli-recognizing material and should find invaluable applications, including in chiroptical switches, sensors, and memories as well as in chiral recognition.

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.

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.

Direct Detection of Hardly Detectable Hidden Chirality of Hydrocarbons and Deuterated Isotopomers by a Helical Polyacetylene through Chiral Amplification and Memory.

PubMed

Maeda, Katsuhiro; Hirose, Daisuke; Okoshi, Natsuki; Shimomura, Kouhei; Wada, Yuya; Ikai, Tomoyuki; Kanoh, Shigeyoshi; Yashima, Eiji

2018-03-07

We report the first direct chirality sensing of a series of chiral hydrocarbons and isotopically chiral compounds (deuterated isotopomers), which are almost impossible to detect by conventional optical spectroscopic methods, by a stereoregular polyacetylene bearing 2,2'-biphenol-derived pendants. The polyacetylene showed a circular dichroism due to a preferred-handed helix formation in response to the hardly detectable hidden chirality of saturated tertiary or chiroptical quaternary hydrocarbons, and deuterated isotopomers. In sharp contrast to the previously reported sensory systems, the chirality detection by the polyacetylene relies on an excess one-handed helix formation induced by the chiral hydrocarbons and deuterated isotopomers via significant amplification of the chirality followed by its static memory, through which chiral information on the minute and hidden chirality can be stored as an excess of a single-handed helix memory for a long time.

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.

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.

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

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.

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 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.

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.

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.

Asymmetric cooperative catalysis of strong Brønsted acid-promoted reactions using chiral ureas.

PubMed

Xu, Hao; Zuend, Stephan J; Woll, Matthew G; Tao, Ye; Jacobsen, Eric N

2010-02-19

Cationic organic intermediates participate in a wide variety of useful synthetic transformations, but their high reactivity can render selectivity in competing pathways difficult to control. Here, we describe a strategy for inducing enantioselectivity in reactions of protio-iminium ions, wherein a chiral catalyst interacts with the highly reactive intermediate through a network of noncovalent interactions. This interaction leads to an attenuation of the reactivity of the iminium ion and allows high enantioselectivity in cycloadditions with electron-rich alkenes (the Povarov reaction). A detailed experimental and computational analysis of this catalyst system has revealed the precise nature of the catalyst-substrate interactions and the likely basis for enantioinduction.

Asymmetric Cooperative Catalysis of Strong Brønsted Acid-Promoted Reactions Using Chiral Ureas

PubMed Central

Xu, Hao; Zuend, Stephan J.; Woll, Matthew G.; Tao, Ye; Jacobsen, Eric N.

2010-01-01

Cationic organic intermediates participate in a wide variety of useful synthetic transformations, but their high reactivity can render selectivity in competing pathways difficult to control. We describe a strategy for inducing enantioselectivity in reactions of protio-iminium ions, wherein a chiral catalyst interacts with the highly reactive intermediate through a network of non-covalent interactions. This leads to an attenuation of the reactivity of the iminium ion, and allows high enantioselectivity in cycloadditions with electron-rich alkenes (the Povarov reaction). A detailed experimental and computational analysis of this catalyst system has revealed the precise nature of the catalyst-substrate interactions and the likely basis for enantioinduction. PMID:20167783

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.

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.

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.

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.

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

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.

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.

High Catalytic Rates for Hydrogen Production Using Nickel Electrocatalysts with Seven-Membered Diphosphine Ligands Containing One Pendent Amine

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

Stewart, Michael P.; Ho, Ming-Hsun; Wiese, Stefan

2013-04-24

A series of Ni-based electrocatalysts, [Ni(7PPh2NC6H4X)2](BF4)2, featuring seven-membered cyclic diphosphine ligands incorporating a single amine base, 1-para-X-phenyl-3,6-triphenyl-1-aza-3,6-diphosphacycloheptane (7PPh2NC6H4X where X = OMe, Me, Br, Cl or CF3), have been synthesized and characterized. X-ray diffraction studies have established that the [Ni(7PPh2NC6H4X)2]2+ complexes have a square planar geometry, with bonds to four phosphorus atoms of the two bidentate diphosphine ligands. Coordination of the bidentate phosphine ligands to Ni result in one six-membered ring containing a pendent amine, and one five membered ring. Each of the complexes is an efficient electrocatalyst for hydrogen production at the potential of the Ni(II/I) couple, with turnovermore » frequencies ranging from 2,400 to 27,000 s-1 with [(DMF)H]+ in acetonitrile. Addition of water (up to 1.0 M) accelerates the catalysis, giving turnover frequencies ranging from 4,100 - 96,000 s-1. Computational studies carried out on the [Ni(7PPh2NC6H4X)2]2+ family indicate the catalytic rates reach a maximum when the electron-donating character of X results in the pKa of the pendent amine matching that of the acid used for proton delivery. Additionally, the fast catalytic rates for hydrogen production by the [Ni(7PPh2NC6H4X)2]2+ family relative to the analogous [Ni(PPh2NC6H4X2)2]2+ family are attributed to preferred formation of endo protonated isomers with respect to the metal center in the former, which is essential for the protons to attain suitable proximity to the reduced metal center to generate H2. The results of this work highlight the importance of the necessity for precise pKa matching with the acid for proton delivery to the metal center, and the mechanistic details described herein will be used to guide future catalyst design. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office

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

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 .

Synthesis and Utilization of Trialkylammonium-Substituted Cyclodextrins as Water-Soluble Chiral NMR Solvating Agents for Anionic Compounds.

PubMed

Dowey, Alison E; Puentes, Cira Mollings; Carey-Hatch, Mira; Sandridge, Keyana L; Krishna, Nikhil B; Wenzel, Thomas J

2016-04-01

Cationic trialkylammonium-substituted α-, β-, and γ-cyclodextrins containing trimethyl-, triethyl-, and tri-n-propylammonium substituent groups were synthesized and analyzed for utility as water-soluble chiral nuclear magnetic resonance (NMR) solvating agents. Racemic and enantiomerically pure (3-chloro-2-hydroxypropyl)trimethyl-, triethyl-, and tri-n-propyl ammonium chloride were synthesized from the corresponding trialkyl amine hydrochloride and either racemic or enantiomerically pure epichlorohydrin. The ammonium salts were then reacted with α-, β-, and γ-cyclodextrins at basic pH to provide the corresponding randomly substituted cationic cyclodextrins. The (1) H NMR spectra of a range of anionic, aromatic compounds was recorded with the cationic cyclodextrins. Cyclodextrins with a single stereochemistry at the hydroxy group on the (2-hydroxypropyl)trialkylammonium chloride substituent were often but not always more effective than the corresponding cyclodextrin in which the C-2 position was racemic. In several cases, the larger triethyl or tri-n-propyl derivatives were more effective than the corresponding trimethyl derivative at causing enantiomeric differentiation. None of the cyclodextrin derivatives were consistently the most effective for all of the anionic compounds studied. © 2016 Wiley Periodicals, Inc.

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.

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

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''.

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.

Controlling Chirality of Entropic Crystals

NASA Astrophysics Data System (ADS)

Damasceno, Pablo; Karas, Andrew; Schultz, Benjamin; Engel, Michael; Glotzer, Sharon

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. Work supported by the National Science Foundation, Division of Materials Research Award No. DMR 1120923, U.S. Army Research Office under Grant Award No. W911NF-10-1-0518, and also by the DOD/ASD (R&E) under Award No. N00244-09-1-0062.

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.

Chiral fiber sensors

NASA Astrophysics Data System (ADS)

Kopp, Victor I.; Churikov, Victor M.; Singer, Jonathan; Neugroschl, Daniel; Genack, Azriel Z.

2010-04-01

We have fabricated a variety of chiral fiber sensors by twisting one or more standard or custom optical fibers with noncircular or nonconcentric core as they pass though a miniature oven. The resulting structures are as stable as the glass material and can be produced with helical pitch ranging from microns to hundreds of microns. The polarization selectivity of the chiral gratings is determined by the geometry of the fiber cross section. Single helix structures are polarization insensitive, while double helix gratings interact only with a single optical polarization component. Both single and double helix gratings may function as a fiber long period grating, coupling core and cladding modes or as a diffraction grating scattering light from the fiber core out of the fiber. The resulting dips in the transmission spectrum are sensitive to fiber elongation, twist and temperature, and (in the case of the long period gratings) to the refractive index of the surrounding medium. The suitability of chiral gratings for sensing temperature, elongation, twist and liquid levels will be discussed. Gratings made of radiation sensitive glass can be used to measure the cumulative radiation dose, while gratings made of radiation-hardened glass are suitable for stable sensing of the environment in nuclear power plants. Excellent temperature stability up to 900°C is found in pure silica chiral diffraction grating sensors.

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

Chiral Dynamics 2006

NASA Astrophysics Data System (ADS)

Ahmed, Mohammad W.; Gao, Haiyan; Weller, Henry R.; Holstein, Barry

2007-10-01

pt. A. Plenary session. Opening remarks: experimental tests of chiral symmetry breaking / A. M. Bernstein. [Double pie symbols] scattering / H. Leutwyler. Chiral effective field theory in a [Triangle]-resonance region / V. Pascalutsa. Some recent developments in chiral perturbation theory / Ulf-G. Mei ner. Chiral extrapolation and nucleon structure from the lattice / R.D. Young. Recent results from HAPPEX / R. Michaels. Chiral symmetries and low energy searches for new physics / M.J. Ramsey-Musolf. Kaon physics: recent experimental progress / M. Moulson. Status of the Cabibbo angle / V. Cirigliano. Lattice QCD and nucleon spin structure / J.W. Negele. Spin sum rules and polarizabilities: results from Jefferson lab / J-P Chen. Compton scattering and nucleon polarisabilities / Judith A. McGovern. Virtual compton scattering at MIT-bates / R. Miskimen. Physics results from the BLAST detector at the BATES accelerator / R.P. Redwine. The [Pie sympbol]NN system, recent progress / C. Hanhart. Application of chiral nuclear forces to light nuclei / A. Nogga. New results on few-body experiments at low energy / Y. Nagai. Few-body lattice calculations / M.J. Savage. Research opportunities at the upgraded HI?S facility / H.R. Weller -- pt. B. Goldstone boson dynamics. Working group summary: Goldstone Boson dynamics / G. Colangelo and S. Giovannella. Recent results on radiative Kaon decays from NA48 and NA48/2 / S.G. López. Cusps in K-->3 [Pie symbol] decays / B. Kubis. Recent KTeV results on radiative Kaon decays / M.C. Ronquest. The [Double pie symbols] scattering amplitude / J.R. Peláez. Determination of the Regge parameters in the [Double pie symbols] scattering amplitude / I. Caprini. e+e- Hadronic cross section measurement at DA[symbol]NE with the KLOE detector / P. Beltrame. Measurement of the form factors of e+e- -->2([Pie symbol]+[Pie symbol]-), pp and the resonant parameters of the heavy charmonia at BES / H. Hu. Measurement of e+e- multihadronic cross section below 4

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 ...

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.

Ester versus polyketone formation in the palladium-diphosphine catalyzed carbonylation of ethene.

PubMed

Zuidema, Erik; Bo, Carles; van Leeuwen, Piet W N M

2007-04-04

The origin of the chemoselectivity of palladium catalysts containing bidentate phosphine ligands toward either methoxycarbonylation of ethene or the copolymerization of ethene and carbon monoxide was investigated using density functional theory based calculations. For a palladium catalyst containing the electron-donating bis(dimethylphosphino)ethane (dmpe) ligand, the rate determining step for chain propagation is shown to be the insertion of ethene into the metal-acyl bond. The high barrier for chain propagation is attributed to the low stability of the ethene intermediate, (dmpe)Pd(ethene)(C(O)CH3). For the competing methanolysis process, the most likely pathway involves the formation of (dmpe)Pd(CH3OH)(C(O)CH3) via dissociative ligand exchange, followed by a solvent mediated proton-transfer/reductive- elimination process. The overall barrier for this process is higher than the barrier for ethene insertion into the palladium-acetyl bond, in line with the experimentally observed preference of this type of catalyst toward the formation of polyketone. Electronic bite angle effects on the rates of ethene insertion and ethanoyl methanolysis were evaluated using four electronically and sterically related ligands (Me)2P(CH2)nP(Me)2 (n = 1-4). Steric effects were studied for larger tert-butyl substituted ligands using a QM/MM methodology. The results show that ethene coordination to the metal center and subsequent insertion into the palladium-ethanoyl bond are disfavored by the addition of steric bulk around the metal center. Key intermediates in the methanolysis mechanism, on the other hand, are stabilized because of electronic effects caused by increasing the bite angle of the diphosphine ligand. The combined effects explain successfully which ligands give polymer and which ones give methyl propionate as the major products of the reaction.

Chirality-Controlled Synthesis and Applications of Single-Wall Carbon Nanotubes.

PubMed

Liu, Bilu; Wu, Fanqi; Gui, Hui; Zheng, Ming; Zhou, Chongwu

2017-01-24

Preparation of chirality-defined single-wall carbon nanotubes (SWCNTs) is the top challenge in the nanotube field. In recent years, great progress has been made toward preparing single-chirality SWCNTs through both direct controlled synthesis and postsynthesis separation approaches. Accordingly, the uses of single-chirality-dominated SWCNTs for various applications have emerged as a new front in nanotube research. In this Review, we review recent progress made in the chirality-controlled synthesis of SWCNTs, including metal-catalyst-free SWCNT cloning by vapor-phase epitaxy elongation of purified single-chirality nanotube seeds, chirality-specific growth of SWCNTs on bimetallic solid alloy catalysts, chirality-controlled synthesis of SWCNTs using bottom-up synthetic strategy from carbonaceous molecular end-cap precursors, etc. Recent major progresses in postsynthesis separation of single-chirality SWCNT species, as well as methods for chirality characterization of SWCNTs, are also highlighted. Moreover, we discuss some examples where single-chirality SWCNTs have shown clear advantages over SWCNTs with broad chirality distributions. We hope this review could inspire more research on the chirality-controlled preparation of SWCNTs and equally important inspire the use of single-chirality SWCNT samples for more fundamental studies and practical applications.

Formation of Enhanced Uniform Chiral Fields in Symmetric Dimer Nanostructures

PubMed Central

Tian, Xiaorui; Fang, Yurui; Sun, Mengtao

2015-01-01

Chiral fields with large optical chirality are very important in chiral molecules analysis, sensing and other measurements. Plasmonic nanostructures have been proposed to realize such super chiral fields for enhancing weak chiral signals. However, most of them cannot provide uniform chiral near-fields close to the structures, which makes these nanostructures not so efficient for applications. Plasmonic helical nanostructures and blocked squares have been proved to provide uniform chiral near-fields, but structure fabrication is a challenge. In this paper, we show that very simple plasmonic dimer structures can provide uniform chiral fields in the gaps with large enhancement of both near electric fields and chiral fields under linearly polarized light illumination with polarization off the dimer axis at dipole resonance. An analytical dipole model is utilized to explain this behavior theoretically. 30 times of volume averaged chiral field enhancement is gotten in the whole gap. Chiral fields with opposite handedness can be obtained simply by changing the polarization to the other side of the dimer axis. It is especially useful in Raman optical activity measurement and chiral sensing of small quantity of chiral molecule. PMID:26621558

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.

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

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.

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.

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

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 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.

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

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.

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

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

Enantiomeric separations of chiral pharmaceuticals using chirally modified tetrahexahedral Au nanoparticles

NASA Astrophysics Data System (ADS)

Shukla, N.; Yang, D.; Gellman, A. J.

2016-06-01

Tetrahexahedral (THH, 24-sided) Au nanoparticles modified with D- or L-cysteine (Cys) have been used as enantioselective separators of the chiral pharmaceutical propranolol (PLL) in solution phase. Polarimetry has been used to measure the rotation of linearly polarized light by solutions containing mixtures of PLL and Cys/THH-Au NPs with varying enantiomeric excesses of each. Polarimetry yields clear evidence of enantiospecific adsorption of PLL onto the Cys/THH-Au NPs. This extends prior work using propylene oxide as a test chiral probe, by using the crystalline THH Au NPs with well-defined facets to separate a real pharmaceutical. This work suggests that chiral nanoparticles, coupled with a density separation method such as centrifugation, could be used for enantiomeric purification of real pharmaceuticals. A simple robust model developed earlier has also been used to extract the enantiospecific equilibrium constants for R- and S-PLL adsorption onto the D- and L-Cys/THH-Au NPs.

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.

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.

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].

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.

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

Hierarchical chirality transfer in the growth of Towel Gourd tendrils

PubMed Central

Wang, Jian-Shan; Wang, Gang; Feng, Xi-Qiao; Kitamura, Takayuki; Kang, Yi-Lan; Yu, Shou-Wen; Qin, Qing-Hua

2013-01-01

Chirality plays a significant role in the physical properties and biological functions of many biological materials, e.g., climbing tendrils and twisted leaves, which exhibit chiral growth. However, the mechanisms underlying the chiral growth of biological materials remain unclear. In this paper, we investigate how the Towel Gourd tendrils achieve their chiral growth. Our experiments reveal that the tendrils have a hierarchy of chirality, which transfers from the lower levels to the higher. The change in the helical angle of cellulose fibrils at the subcellular level induces an intrinsic torsion of tendrils, leading to the formation of the helical morphology of tendril filaments. A chirality transfer model is presented to elucidate the chiral growth of tendrils. This present study may help understand various chiral phenomena observed in biological materials. It also suggests that chirality transfer can be utilized in the development of hierarchically chiral materials having unique properties. PMID:24173107

Studies of the structural and magnetic properties of an unsymmetrical ligand 1,2,4-benzenetricarboxylic acid based chiral 3-D trinickel coordination polymer as an alkali base-influenced hydrothermal reaction product

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

Peng, Yi-Ru; Chien, Po-Hsiu; Chung, Huey-Ting

2014-04-01

The reaction of 1,2,4-benzenetricarboxylic acid (H{sub 3}btc), as a ligand, under pH-controlled hydrothermal conditions with nickel salts leads to the formation of a coordination polymer of (CsNi{sub 3}(OH)(H{sub 2}O){sub 3}[C{sub 6}H{sub 3}(CO{sub 2}){sub 3}]{sub 2}·3H{sub 2}O){sub n} (1). The subunit of compound 1 contains a hydroxide- and carboxylate-bridged trinickel clusters that are linked by an unsymmetrical organic carboxylate spacer to form a chiral three-dimensional anionic framework, in which cesium cations and guest water molecules are located in one-dimensional channels. The presence of a hydroxide ion serves both as a deprotonation agent and a cation source during the hydrothermal reaction, thusmore » permitting the extent of deprotonation of the unsymmetrical ligand H{sub 3}btc to be controlled, which is essential for the successful formation of compound 1. The magnetic properties of compound 1 were analyzed. Both dc and ac magnetic susceptibility as well as reduced magnetization measurements confirmed the spin-frustration nature of 1. - Graphical abstract: A chiral three-dimension MOF compound and its magnetic properties are described. - Highlights: • A new chiral three-dimension coordination polymer were made. • An un-symmetric bridging ligand was used. • Alkali metal ion Cs{sup +} was incorporated in the structure. • Magnetic properties were studied.« less

Gyroscope-like molecules consisting of PdX₂/PtX₂ rotators within three-spoke dibridgehead diphosphine stators: syntheses, substitution reactions, structures, and dynamic properties.

PubMed

Nawara-Hultzsch, Agnieszka J; Stollenz, Michael; Barbasiewicz, Michał; Szafert, Sławomir; Lis, Tadeusz; Hampel, Frank; Bhuvanesh, Nattamai; Gladysz, John A

2014-04-14

Threefold intramolecular ring-closing metatheses of trans-[MCl2(P{(CH2)(m)CH=CH2}3)2] are effected with Grubbs' catalyst. Following hydrogenation catalyzed by [RhCl(PPh3)3], the title complexes trans-[MCl2(P((CH2)n)3P)] (n=2m+2; M/n=Pt/14, 4 c; Pt/16, 4 d; Pt/18, 4 e; Pd/14, 5 c; Pd/18, 5 e) and sometimes isomers partly derived from intraligand metathesis, trans-[MCl2{P(CH2)n(CH2)n}P(CH2)n)] (4'c-e, 5'e), are isolated. These react with LiBr, NaI, and KCN to give the corresponding MBr2, MI2, and M(CN)2 species (58-99%). (13)C NMR data show that the MX2 moieties rapidly rotate within the diphosphine cage on the NMR timescale, even at -120 °C. The reaction of 4 c and KSCN gives separable Pt(NCS)2 and Pt(NCS)(SCN) adducts (13 c, 28%; 14 c, 20%), and those of 4 c,e and Ph2Zn give PtPh2 species (15 c, 61%; 15 e, 90%). (13)C NMR spectra of 13 c-15 c show two sets of CH2 signals (ca. 2:1 intensity ratios), indicating that MX2 rotation is no longer rapid. Reactions of 4 c or 4'c and excess NaC≡CH afford the free diphosphines P{(CH2)14}3P (91%) and (CH2)14P(CH2)14P(CH2)14 (90%). The latter has been crystallographically characterized as a bis(BH3) adduct. The crystal structures of eight complexes with P(CH2)14P linkages (PtCl2, PtBr2, PtI2, Pt(NCS)2, PtPh2, PdCl2, PdBr2, PdI2) and 15 e have been determined, and intramolecular distances analyzed with respect to MX2 rotation. The conformations of the (CH2)14 moieties and features of the crystal lattices are also discussed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

DOE PAGES

Mueller, Niklas; Venugopalan, Raju

2018-03-21

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

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

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.

Chirality measures of α-amino acids.

PubMed

Jamróz, Michał H; Rode, Joanna E; Ostrowski, Sławomir; Lipiński, Piotr F J; Dobrowolski, Jan Cz

2012-06-25

To measure molecular chirality, the molecule is treated as a finite set of points in the Euclidean R(3) space supplemented by k properties, p(1)((i)), p(2)((i)), ..., p(k)((i)) assigned to the ith atom, which constitute a point in the Property P(k) space. Chirality measures are described as the distance between a molecule and its mirror image minimized over all its arbitrary orientation-preserving isometries in the R(3) × P(k) Cartesian product space. Following this formalism, different chirality measures can be estimated by taking into consideration different sets of atomic properties. Here, for α-amino acid zwitterionic structures taken from the Cambridge Structural Database and for all 1684 neutral conformers of 19 biogenic α-amino acid molecules, except glycine and cystine, found at the B3LYP/6-31G** level, chirality measures have been calculated by a CHIMEA program written in this project. It is demonstrated that there is a significant correlation between the measures determined for the α-amino acid zwitterions in crystals and the neutral forms in the gas phase. Performance of the studied chirality measures with changes of the basis set and computation method was also checked. An exemplary quantitative structure–activity relationship (QSAR) application of the chirality measures was presented by an introductory model for the benchmark Cramer data set of steroidal ligands of the sex-hormone binding globulin.

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.

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.

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

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.

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.

Structural and energetic study of cation-π-cation interactions in proteins.

PubMed

Pinheiro, Silvana; Soteras, Ignacio; Gelpí, Josep Lluis; Dehez, François; Chipot, Christophe; Luque, F Javier; Curutchet, Carles

2017-04-12

Cation-π interactions of aromatic rings and positively charged groups are among the most important interactions in structural biology. The role and energetic characteristics of these interactions are well established. However, the occurrence of cation-π-cation interactions is an unexpected motif, which raises intriguing questions about its functional role in proteins. We present a statistical analysis of the occurrence, composition and geometrical preferences of cation-π-cation interactions identified in a set of non-redundant protein structures taken from the Protein Data Bank. Our results demonstrate that this structural motif is observed at a small, albeit non-negligible frequency in proteins, and suggest a preference to establish cation-π-cation motifs with Trp, followed by Tyr and Phe. Furthermore, we have found that cation-π-cation interactions tend to be highly conserved, which supports their structural or functional role. Finally, we have performed an energetic analysis of a representative subset of cation-π-cation complexes combining quantum-chemical and continuum solvation calculations. Our results point out that the protein environment can strongly screen the cation-cation repulsion, leading to an attractive interaction in 64% of the complexes analyzed. Together with the high degree of conservation observed, these results suggest a potential stabilizing role in the protein fold, as demonstrated recently for a miniature protein (Craven et al., J. Am. Chem. Soc. 2016, 138, 1543). From a computational point of view, the significant contribution of non-additive three-body terms challenges the suitability of standard additive force fields for describing cation-π-cation motifs in molecular simulations.

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.

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.

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

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.

Doped Chiral Polymer Metamaterials

NASA Technical Reports Server (NTRS)

Kang, Jin Ho (Inventor); Gordon, Keith L. (Inventor); Sauti, Godfrey (Inventor); Bryant, Robert G. (Inventor); Park, Cheol (Inventor); Lowther, Sharon E. (Inventor)

2017-01-01

Some implementations provide a composite material that includes a first material and a second material. In some implementations, the composite material is a metamaterial. The first material includes a chiral polymer (e.g., crystalline chiral helical polymer, poly-.gamma.-benzyl-L-glutamate (PBLG), poly-L-lactic acid (PLA), polypeptide, and/or polyacetylene). The second material is within the chiral polymer. The first material and the second material are configured to provide an effective index of refraction value for the composite material of 1 or less. In some implementations, the effective index of refraction value for the composite material is negative. In some implementations, the effective index of refraction value for the composite material of 1 or less is at least in a wavelength of one of at least a visible spectrum, an infrared spectrum, a microwave spectrum, and/or an ultraviolet spectrum.

Evaluation of C4 diphosphine ligands in rhodium catalysed methanol carbonylation under a syngas atmosphere: synthesis, structure, stability and reactivity of rhodium(I) carbonyl and rhodium(III) acetyl intermediates.

PubMed

Lamb, Gareth; Clarke, Matthew; Slawin, Alexandra M Z; Williams, Bruce; Key, Lesley

2007-12-21

The carbonylation of methanol to acetic acid is a hugely important catalytic process, and there are considerable cost and environmental advantages if a process could be designed that was tolerant of hydrogen impurities in the CO feed gas, while eliminating by-products such as propionic acid and acetaldehyde altogether. This paper reports on an investigation into the application of rhodium complexes of several C(4) bridged diphosphines, namely BINAP, 1,4-bis(diphenylphosphino)butane (dppb), bis(diphenylphosphino)xylene (dppx) and 1,4-bis(dicyclohexylphosphino)butane (dcpb) as catalysts for hydrogen tolerant methanol carbonylation. An investigation into the structure, reactivity and stability of pre-catalysts and catalyst resting states of these complexes has also been carried out in order to understand the observations in catalysis. Rh(I) carbonyl halide complexes of each of the ligands have been prepared from both [Rh(2)(CO)(4)Cl(2)] and dimeric mu-Cl-[Rh(L)Cl](2) complexes. These Rh(I) carbonyl complexes are either dimeric with bridging phosphine ligands (dppb, dcpb, dppx) or monomeric chelate complexes. The reaction of the complexes with methyl iodide at 140 degrees C has been studied, which has revealed clear differences in the stability of the corresponding Rh(III) complexes. Surprisingly, the dimeric Rh(I) carbonyls react cleanly with MeI with rearrangement of the diphosphine to a chelate co-ordination mode to give stable Rh(III) acetyl complexes. The Rh acetyls for L=dppb and dppx have been fully characterised by X-ray crystallography. During the catalytic studies, the more rigid dppx and BINAP ligands were found to be nearly 5 times more hydrogen tolerant than [Rh(CO)(2)I(2)](-), as revealed by by-product analysis. The origin of this hydrogen tolerance is explained based on the differing reactivities of the Rh acetyls with hydrogen gas, and by considering the structure of the complexes.

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.

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

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.

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

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.

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.

Stereospecific ring expansion from orthocyclophanes with central chirality to metacyclophanes with planar chirality.

PubMed

Ishida, Naoki; Sawano, Shota; Murakami, Masahiro

2014-01-01

Carbon-carbon bonds constitute the major framework of organic molecules and carbon-hydrogen bonds are abundant in their peripheries. Such nonpolar σ-bonds are thermodynamically stable and kinetically inert in general. Nonetheless, selective activation of those ubiquitous bonds may offer a straightforward method to construct and/or functionalize organic skeletons. Herein we describe ring expansion from orthocyclophanes to metacyclophanes occurring upon sequential action of light and a metal catalyst. Formally, specific non-strained carbon-hydrogen and carbon-carbon bonds are cleaved and exchanged without elimination of any leaving groups. Notably, the product is energetically uphill from the starting material, but the endergonic photocyclization step makes it possible to drive the transformation forward. The ring expansion is extended to the stereospecific synthesis of metacyclophanes possessing planar chirality, during which central chirality on a tertiary carbon is transferred to planar chirality.

Intrinsic Chirality Origination in Carbon Nanotubes.

PubMed

Pierce, Neal; Chen, Gugang; P Rajukumar, Lakshmy; Chou, Nam Hawn; Koh, Ai Leen; Sinclair, Robert; Maruyama, Shigeo; Terrones, Mauricio; Harutyunyan, Avetik R

2017-10-24

Elucidating the origin of carbon nanotube chirality is key for realizing their untapped potential. Currently, prevalent theories suggest that catalyst structure originates chirality via an epitaxial relationship. Here we studied chirality abundances of carbon nanotubes grown on floating liquid Ga droplets, which excludes the influence of catalyst features, and compared them with abundances grown on solid Ru nanoparticles. Results of growth on liquid droplets bolsters the intrinsic preference of carbon nuclei toward certain chiralities. Specifically, the abundance of the (11,1)/χ = 4.31° tube can reach up to 95% relative to (9,4)/χ = 17.48°, although they have exactly the same diameter, (9.156 Å). However, the comparative abundances for the pair, (19,3)/χ = 7.2° and (17,6)/χ = 14.5°, with bigger diameter, (16.405 Å), fluctuate depending on synthesis temperature. The abundances of the same pairs of tubes grown on floating solid polyhedral Ru nanoparticles show completely different trends. Analysis of abundances in relation to nucleation probability, represented by a product of the Zeldovich factor and the deviation interval of a growing nuclei from equilibrium critical size, explain the findings. We suggest that the chirality in the nanotube in general is a result of interplay between intrinsic preference of carbon cluster and induction by catalyst structure. This finding can help to build the comprehensive theory of nanotube growth and offers a prospect for chirality-preferential synthesis of carbon nanotubes by the exploitation of liquid catalyst droplets.

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 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...

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.

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).

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

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.

Divalent cation shrinks DNA but inhibits its compaction with trivalent cation.

PubMed

Tongu, Chika; Kenmotsu, Takahiro; Yoshikawa, Yuko; Zinchenko, Anatoly; Chen, Ning; Yoshikawa, Kenichi

2016-05-28

Our observation reveals the effects of divalent and trivalent cations on the higher-order structure of giant DNA (T4 DNA 166 kbp) by fluorescence microscopy. It was found that divalent cations, Mg(2+) and Ca(2+), inhibit DNA compaction induced by a trivalent cation, spermidine (SPD(3+)). On the other hand, in the absence of SPD(3+), divalent cations cause the shrinkage of DNA. As the control experiment, we have confirmed the minimum effect of monovalent cation, Na(+) on the DNA higher-order structure. We interpret the competition between 2+ and 3+ cations in terms of the change in the translational entropy of the counterions. For the compaction with SPD(3+), we consider the increase in translational entropy due to the ion-exchange of the intrinsic monovalent cations condensing on a highly charged polyelectrolyte, double-stranded DNA, by the 3+ cations. In contrast, the presence of 2+ cation decreases the gain of entropy contribution by the ion-exchange between monovalent and 3+ ions.

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

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.

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...

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.

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.

Synthesis and Structure of Vanadium Halide Complexes Containing Diphosphine Ligands with Pendant Amines

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

Egbert, Jonathan D.; Labios, Liezel A.; Darmon, Jonathan M.

2016-02-18

A series of vanadium(III) diiodide complexes of the formula CpV(P RN R'P R)I 2 (Cp = 5-C 5H 5; P RN R'P R = (R 2PCH 2) 2N(R)), where R = Et, R = Me (1a), R = Ph (1b); R = Ph, R = Me (1c)) is reported. The corresponding vanadium(II) monoiodide complexes of the formula CpV(P RN R' PR)I, where R = Et, R = Me (2a), R = Ph (2b); R = Ph, R = Me (2c)) were prepared in THF by reduction of 1a-c with Zn powder. The paramagnetic complexes 1a-c and 2a-c are characterized bymore » elemental analysis, 1H NMR spectroscopy, and by cyclic voltammetry for complexes 2b and 4b. Complexes 1c and 2a-c were also characterized in the single crystal by X-ray crystallography. We report the preparation of the vanadium(II) complexes CpV(P Ph 2N Ph 2)I (3) (P Ph 2N Ph 2 = 1,5-diphenyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane) and trans-[VCl 2(PEtNMePEt)2] (4a) and trans-[VCl 2(PEtNPhPEt) 2] (4b). These complexes represent initial coordination chemistry of vanadium complexes with P RN R'P R and P Ph 2N Ph 2 diphosphine ligands, which contain a pendant amine in the second coordination sphere. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.« less

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.

Chiral drag force

DOE PAGES

Rajagopal, Krishna; Sadofyev, Andrey V.

2015-10-05

Here, we provide a holographic evaluation of novel contributions to the drag force acting on a heavy quark moving through strongly interacting plasma. The new contributions are chiral in the sense that they act in opposite directions in plasmas containing an excess of left- or right-handed quarks. The new contributions are proportional to the coefficient of the axial anomaly, and in this sense also are chiral. These new contributions to the drag force act either parallel to or antiparallel to an external magnetic field or to the vorticity of the fluid plasma. In all these respects, these contributions to themore » drag force felt by a heavy quark are analogous to the chiral magnetic effect (CME) on light quarks. However, the new contribution to the drag force is independent of the electric charge of the heavy quark and is the same for heavy quarks and antiquarks, meaning that these novel effects do not in fact contribute to the CME current. We show that although the chiral drag force can be non-vanishing for heavy quarks that are at rest in the local fluid rest frame, it does vanish for heavy quarks that are at rest in a suitably chosen frame. In this frame, the heavy quark at rest sees counterpropagating momentum and charge currents, both proportional to the axial anomaly coefficient, but feels no drag force. This provides strong concrete evidence for the absence of dissipation in chiral transport, something that has been predicted previously via consideration of symmetries. Along the way to our principal results, we provide a general calculation of the corrections to the drag force due to the presence of gradients in the flowing fluid in the presence of a nonzero chemical potential. We close with a consequence of our result that is at least in principle observable in heavy ion collisions, namely an anticorrelation between the direction of the CME current for light quarks in a given event and the direction of the kick given to the momentum of all the heavy

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.

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

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.

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.

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.

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.

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.

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.

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

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.

Understanding Cooperative Chirality at the Nanoscale

NASA Astrophysics Data System (ADS)

Yu, Shangjie; Wang, Pengpeng; Govorov, Alexander; Ouyang, Min

Controlling chirality of organic and inorganic structures plays a key role in many physical, chemical and biochemical processes, and may offer new opportunity to create technology applications based on chiroptical effect. In this talk, we will present a theoretical model and simulation to demonstrate how to engineer nanoscale chirality in inorganic nanostructures via synergistic control of electromagnetic response of both lattice and geometry, leading to rich tunability of chirality at the nanoscale. Our model has also been applied to understand recent materials advancement of related control with excellent agreement, and can elucidate physical origins of circular dichroism features in the experiment.

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 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.

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.

Role of the Diphosphine Chelate in Emissive, Charge-Neutral Iridium(III) Complexes.

PubMed

Liao, Jia-Ling; Devereux, Leon R; Fox, Mark A; Yang, Chun-Chieh; Chiang, Yu-Cheng; Chang, Chih-Hao; Lee, Gene-Hsiang; Chi, Yun

2018-01-12

A class of neutral tris-bidentate Ir III metal complexes incorporating a diphosphine as a chelate is prepared and characterized here for the first time. Treatment of [Ir(dppBz)(tht)Cl 3 ] (1, dppBz=1,2-bis(diphenylphosphino)benzene, tht=tetrahydrothiophene) with fppzH (3-trifluoromethyl-5-(2'-pyridyl)-1H-pyrazole) afforded the dichloride complexes, trans-(Cl,Cl)[Ir(dppBz)(fppz)Cl 2 ] (2) and cis-(Cl,Cl)[Ir(dppBz)(fppz)Cl 2 ] (3). The reaction of 3 with the dianionic chelate precursor, 5,5'-di(trifluoromethyl)-3,3'-bipyrazole (bipzH 2 ) or 5,5'-(1-methylethylidene)-bis(3-trifluoromethyl-1H-pyrazole) (mepzH 2 ), in DMF gave the tris-bidentate complex [Ir(dppBz)(fppz)(bipz)] (4) or [Ir(dppBz)(fppz)(mepz)] (5), respectively. In contrast, a hydride complex [Ir(dppBz)(fppz)(bipzH)H] (6) was isolated instead of 4 in protic solvent, namely: diethylene glycol monomethyl ether (DGME). All complexes 2-6 are luminescent in powder form and thin films where the dichlorides (2, 3) emit with maxima at 590-627 nm (orange) and quantum yields (QYs) up to 90 % whereas the tris-bidentate (4, 5) and hydride (6) complexes emit at 455-458 nm (blue) with QYs up to 70 %. Hybrid (time-dependent) DFT calculations showed considerable metal-to-ligand charge transfer contribution to the orange-emitting 2 and 3 but substantial ligand-centered 3 π-π* transition character in the blue-emitting 4-6. The dppBz does not participate in the radiative transitions in 4-6, but it provides the rigidity and steric bulk needed to promote the luminescence by suppressing the self-quenching in the solid state. Fabrication of an organic light-emitting diode (OLED) with dopant 5 gave a deep-blue CIE chromaticity of (0.16, 0.15). Superior blue emitters, which are vital in OLED applications, may be found in other neutral Ir III complexes containing phosphine chelates. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

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.

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

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.

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.

Chromatographic Studies of Protein-Based Chiral Separations

PubMed Central

Bi, Cong; Zheng, Xiwei; Azaria, Shiden; Beeram, Sandya; Li, Zhao; Hage, David S.

2016-01-01

The development of separation methods for the analysis and resolution of chiral drugs and solutes has been an area of ongoing interest in pharmaceutical research. The use of proteins as chiral binding agents in high-performance liquid chromatography (HPLC) has been an approach that has received particular attention in such work. This report provides an overview of proteins that have been used as binding agents to create chiral stationary phases (CSPs) and in the use of chromatographic methods to study these materials and protein-based chiral separations. The supports and methods that have been employed to prepare protein-based CSPs will also be discussed and compared. Specific types of CSPs that are considered include those that employ serum transport proteins (e.g., human serum albumin, bovine serum albumin, and alpha1-acid glycoprotein), enzymes (e.g., penicillin G acylase, cellobiohydrolases, and α-chymotrypsin) or other types of proteins (e.g., ovomucoid, antibodies, and avidin or streptavidin). The properties and applications for each type of protein and CSP will also be discussed in terms of their use in chromatography and chiral separations. PMID:28344977

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.

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.

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.

Chirality and gravitational parity violation.

PubMed

Bargueño, Pedro

2015-06-01

In this review, parity-violating gravitational potentials are presented as possible sources of both true and false chirality. In particular, whereas phenomenological long-range spin-dependent gravitational potentials contain both truly and falsely chiral terms, it is shown that there are models that extend general relativity including also coupling of fermionic degrees of freedom to gravity in the presence of torsion, which give place to short-range truly chiral interactions similar to that usually considered in molecular physics. Physical mechanisms which give place to gravitational parity violation together with the expected size of the effects and their experimental constraints are discussed. Finally, the possible role of parity-violating gravity in the origin of homochirality and a road map for future research works in quantum chemistry is presented. © 2015 Wiley Periodicals, Inc.

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

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.

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.

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.

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.

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

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.

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.

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.

The synthesis and structure of a chiral 1D aluminophosphate chain compound: d-Co(en){sub 3}[AlP{sub 2}O{sub 8}].6.5H{sub 2}O

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

Chen Peng; Li Jiyang; Yu Jihong

2005-06-15

A new chiral one-dimensional (1D) aluminophosphate chain compound [d-Co(en){sub 3}][AlP{sub 2}O{sub 8}].6.5H{sub 2}O (designated AlPO-CJ22) has been hydrothermally synthesized by using the optically pure d-Co(en){sub 3}I{sub 3} complex as the template. Single-crystal structural analysis reveals that its structure is built up from alternating connection of AlO{sub 4} and PO{sub 2}(=O{sub 2}) tetrahedra to form corner-shared Al{sub 2}P{sub 2} four-membered ring (4-MR) chains. The d-Co(en){sub 3}{sup 3+} complex cations extended along the 2{sub 1} screw axis interact with the inorganic chains through hydrogen-bonds of N...O atoms in a helical fashion. Optical rotation measurement shows that AlPO-CJ22 is chiral as with d-Co(en){submore » 3}{sup 3+} complex cations. Crystal data: orthorhombic, I2{sub 1}2{sub 1}2{sub 1}, a=8.5573(8)A, b=22.613(2)A, c=22.605(2)A, Z=8, R{sub 1}=0.067, wR{sub 2}=0.1291, and Flack parameter: -0.02(3). CCDC number: 254179. -0.02(3). CCDC number: 254179.« less

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...

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

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.

Implications of Chirality of Drugs and Excipients in Physical Pharmacy.

NASA Astrophysics Data System (ADS)

Duddu, Sarma P.

1993-01-01

The interactions of enantiomers of a chiral drug with other chemical entities, which may lead to changes and stereoselective differences in the physicochemical properties of the drug, were investigated. The various interactions described below employed ephedrine, pseudoephedrine and some of their salts, and to a minor extent, propranolol hydrochloride. The interaction of ephedrinium or pseudoephedrinium with the achiral anion, salicylate, yielded crystalline salts with the notable exception of homochiral ephedrine. Racemic ephedrinium salicylate exists as a centrosymmetric crystal (P2_1/n) whereas racemic pseudoephedrinium salicylate is a mixture of homochiral crystals (P2 _1). The inability of ephedrinium to exist as a homochiral salicylate salt is attributed to a high energy conformation of the ephedrinium cation, following conformational analysis. Arising from conformationally favorable interactions, the crystallization of racemic ephedrinium salicylate from aqueous solutions was utilized to improve the enantiomeric purity of a partially resolved mixture of ephedrine from 60% to 82% in one crystallization step. Interaction of the opposite enantiomers of ephedrine and pseudoephedrine in the solid, liquid, solution and vapor state produced the respective racemic compounds. The formation of racemic ephedrine in the solid state as predominantly second order (k = 392 mol^{-1} hr^{-1}), probably mediated by the vapor phase. The formation of racemic pseudoephedrine was predominantly diffusion-controlled in the solid state via an intermediate non-crystalline phase. The interaction with traces of the opposite enantiomer during crystallization of (RS)-(-)-ephedrinium 2-naphthalenesulfonate and (SS)-(+)-pseudoephedrinium salicylate changed pharmaceutically important solid state properties, including dissolution rate. Uptake of the enantiomeric impurity was measured by a new, sensitive HPLC method. The enantiomeric impurity, at mole fractions <= 0.0027 greatly increased the

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).

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.

Conducting Polymers in the Fields of Energy, Environmental Remediation, and Chemical-Chiral Sensors.

PubMed

Ibanez, Jorge G; Rincón, Marina E; Gutierrez-Granados, Silvia; Chahma, M'hamed; Jaramillo-Quintero, Oscar A; Frontana-Uribe, Bernardo A

2018-05-09

Conducting polymers (CPs), thanks to their unique properties, structures made on-demand, new composite mixtures, and possibility of deposit on a surface by chemical, physical, or electrochemical methodologies, have shown in the last years a renaissance and have been widely used in important fields of chemistry and materials science. Due to the extent of the literature on CPs, this review, after a concise introduction about the interrelationship between electrochemistry and conducting polymers, is focused exclusively on the following applications: energy (energy storage devices and solar cells), use in environmental remediation (anion and cation trapping, electrocatalytic reduction/oxidation of pollutants on CP based electrodes, and adsorption of pollutants) and finally electroanalysis as chemical sensors in solution, gas phase, and chiral molecules. This review is expected to be comprehensive, authoritative, and useful to the chemical community interested in CPs and their applications.

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.

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).

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.

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.

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.

Self-assembly of chiral molecular polygons.

PubMed

Jiang, Hua; Lin, Wenbin

2003-07-09

Treatment of 2,2'-diacetyl-1,1'-binaphthyl-6,6'-bis(ethyne), L-H2, with 1 equiv of trans-Pt(PEt3)2Cl2 led to a mixture of different sizes of chiral metallocycles [trans-(PEt3)2Pt(L)]n (n = 3-8, 1-6). Each of the chiral molecular polygons 1-6 was purified by silica gel column chromatography and characterized by 1H, 13C{1H}, and 31P{1H} NMR spectroscopy, MS, IR, UV-vis, and circular dichroism spectroscopies, and microanalysis. The presence of tunable cavities (1.4-4.3 nm) and chiral functionalities in these molecular polygons promises to make them excellent receptors for a variety of guests.

Exploring backbone-cation alkyl spacers for multi-cation side chain anion exchange membranes

NASA Astrophysics Data System (ADS)

Zhu, Liang; Yu, Xuedi; Hickner, Michael A.

2018-01-01

In order to systematically study how the arrangement of cations on the side chain and length of alkyl spacers between cations impact the performance of multi-cation AEMs for alkaline fuel cells, a series of polyphenylene oxide (PPO)-based AEMs with different cationic side chains were synthesized. This work resulted in samples with two or three cations in a side chain pendant to the PPO backbone. More importantly, the length of the spacer between cations varied from 3 methylene (-CH2-) (C3) groups to 8 methylene (C8) groups. The highest conductivity, up to 99 mS/cm in liquid water at room temperature, was observed for the triple-cation side chain AEM with pentyl (C5) or hexyl (C6) spacers. The multi-cation AEMs were found to have decreased water uptake and ionic conductivity when the spacer chains between cations were lengthened from pentyl (C5) or hexyl (C6) to octyl (C8) linking groups. The triple-cation membranes with pentyl (C5) or hexyl (C6) groups between cations showed greatest stability after immersion in 1 M NaOH at 80 °C for 500 h.

Chiral light intrinsically couples to extrinsic/pseudo-chiral metasurfaces made of tilted gold nanowires

PubMed Central

Belardini, Alessandro; Centini, Marco; Leahu, Grigore; Hooper, David C.; Li Voti, Roberto; Fazio, Eugenio; Haus, Joseph W.; Sarangan, Andrew; Valev, Ventsislav K.; Sibilia, Concita

2016-01-01

Extrinsic or pseudo-chiral (meta)surfaces have an achiral structure, yet they can give rise to circular dichroism when the experiment itself becomes chiral. Although these surfaces are known to yield differences in reflected and transmitted circularly polarized light, the exact mechanism of the interaction has never been directly demonstrated. Here we present a comprehensive linear and nonlinear optical investigation of a metasurface composed of tilted gold nanowires. In the linear regime, we directly demonstrate the selective absorption of circularly polarised light depending on the orientation of the metasurface. In the nonlinear regime, we demonstrate for the first time how second harmonic generation circular dichroism in such extrinsic/pseudo-chiral materials can be understood in terms of effective nonlinear susceptibility tensor elements that switch sign depending on the orientation of the metasurface. By providing fundamental understanding of the chiroptical interactions in achiral metasurfaces, our work opens up new perspectives for the optimisation of their properties. PMID:27553888

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.

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

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.

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.

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.

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.

Single-handed helical carbonaceous nanotubes prepared using a pair of cationic low molecular weight gelators

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

Sun, Huayan; Wang, Qing; Guo, Yongmin

Highlights: • 3-aminophenol-formaldeyde resins were prepared through a templating method. • A pair of cationic gelators have been used as the templates. • Single-handed helical carbonaceous nanotubes were obtained after carbonization. • The carbonaceous nanotubes showed optical activity. - Abstract: We design a facile route to obtain enantiopure carbonaceous nanostructures, which have potential application as chiral sensors, electromagnetic wave absorbers, and asymmetric catalysts. A pair of cationic low molecular weight gelators was synthesized, which were able to self-assemble into twisted nanoribbons in ethanol at a concentration of 20 g L{sup −1} at 25 °C. Single-handed helical 3-aminophenol-formaldehyde resin nanotubes withmore » optical activity were prepared using the self-assembly of the low molecular weight gelators as templates. After carbonization, single-handed helical carbonaceous nanotubes were obtained and characterized using circular dichroism, wide-angle X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The results indicate that the walls of the nanotubes are amorphous carbon. Moreover, the left- and right-handed helical nanotubes exhibit opposite optical activity.« less

Chirality, quantum mechanics, and biological determinism

NASA Astrophysics Data System (ADS)

Davies, P. C. W.

2006-08-01

The holy grail of astrobiology is the discovery of a second sample of life that has emerged de novo, independently of life on Earth (as opposed to extraterrestrial life that shares a common origin with terrestrial life via a panspermia process). It would then be possible to separate aspects of biology that are lawlike and expected from those that are accidental and contingent, and thus to address the question of whether the laws of nature are intrinsically bio-friendly. The popular assumption that life is an almost inevitable product of physics and chemistry, and therefore widespread in the universe, is known as biological determinism. It remains an open question whether biological determinism is correct, as there is little direct evidence in its favour from fundamental physics. Homochirality is a deep property of known life, and provides an important test case for the competing ideas of contingency versus lawfulness - or chance versus necessity. Conceivably, a chiral signature is imprinted on life by fundamental physics via parity-violating mixing of the weak and electromagnetic interactions. If so, homochirality would be universal and lawlike. On the other hand, it may be the result of chance: a random molecular accident during the pre-biotic phase. If the latter explanation is correct, one could expect that a second sample of life may have opposite chiral signature even if it resembled known life in its basic biochemistry. There is thus a curious obverse relationship between chirality and biogenesis in relation to biological determinism. If the chiral signature of life is the product of chance, we may hope to discover "mirror life" (i.e. organisms with opposite chiral signature) as evidence of a second genesis, and the latter would establish that life's emergence from non-life is quasi-deterministic. On the other hand, if the chiral signature is determined by fundamental physics, then it may be much harder to establish an independent origin for extraterrestrial

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.

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.

Leading order relativistic chiral nucleon-nucleon interaction

NASA Astrophysics Data System (ADS)

Ren, Xiu-Lei; Li, Kai-Wen; Geng, Li-Sheng; Long, Bingwei; Ring, Peter; Meng, Jie

2018-01-01

Motivated by the successes of relativistic theories in studies of atomic/molecular and nuclear systems and the need for a relativistic chiral force in relativistic nuclear structure studies, we explore a new relativistic scheme to construct the nucleon-nucleon interaction in the framework of covariant chiral effective field theory. The chiral interaction is formulated up to leading order with covariant power counting and a Lorentz invariant chiral Lagrangian. We find that the relativistic scheme induces all six spin operators needed to describe the nuclear force. A detailed investigation of the partial wave potentials shows a better description of the {}1S0 and {}3P0 phase shifts than the leading order Weinberg approach, and similar to that of the next-to-leading order Weinberg approach. For the other partial waves with angular momenta J≥slant 1, the relativistic results are almost the same as their leading order non-relativistic counterparts. )

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.

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

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.

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)

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.

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.

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...

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.

[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.

Recent progress of chiral stationary phases for separation of enantiomers in gas chromatography.

PubMed

Xie, Sheng-Ming; Yuan, Li-Ming

2017-01-01

Chromatography techniques based on chiral stationary phases are widely used for the separation of enantiomers. In particular, gas chromatography has developed rapidly in recent years due to its merits such as fast analysis speed, lower consumption of stationary phases and analytes, higher column efficiency, making it a better choice for chiral separation in diverse industries. This article summarizes recent progress of novel chiral stationary phases based on cyclofructan derivatives and chiral porous materials including chiral metal-organic frameworks, chiral porous organic frameworks, chiral inorganic mesoporous materials, and chiral porous organic cages in gas chromatography, covering original research papers published since 2010. The chiral recognition properties and mechanisms of separation toward enantiomers are also introduced. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

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

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

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

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.

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

Anion-π Catalysts with Axial Chirality.

PubMed

Wang, Chao; Matile, Stefan

2017-09-04

The idea of anion-π catalysis is to stabilize anionic transition states by anion-π interactions on aromatic surfaces. For asymmetric anion-π catalysis, π-acidic surfaces have been surrounded with stereogenic centers. This manuscript introduces the first anion-π catalysts that operate with axial chirality. Bifunctional catalysts with tertiary amine bases next to π-acidic naphthalenediimide planes are equipped with a bulky aromatic substituent in the imide position to produce separable atropisomers. The addition of malonic acid half thioesters to enolate acceptors is used for evaluation. In the presence of a chiral axis, the selective acceleration of the disfavored but relevant enolate addition was much better than with point chirality, and enantioselectivity could be observed for the first time for this reaction with small-molecule anion-π catalysts. Enantioselectivity increased with the π acidity of the π surface, whereas the addition of stereogenic centers around the aromatic plane did not cause further improvements. These results identify axial chirality of the active aromatic plane generated by atropisomerism as an attractive strategy for asymmetric anion-π catalysis. © 2017 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

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.

Chiral susceptibility and the scalar Ward identity.

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

Chang, L.; Liu, Y.-X.; Roberts, C. D.

2009-03-01

The chiral susceptibility is given by the scalar vacuum polarization at zero total momentum. This follows directly from the expression for the vacuum quark condensate so long as a nonperturbative symmetry preserving truncation scheme is employed. For QCD in-vacuum the susceptibility can rigorously be defined via a Pauli-Villars regularization procedure. Owing to the scalar Ward identity, irrespective of the form or Ansatz for the kernel of the gap equation, the consistent scalar vertex at zero total momentum can automatically be obtained and hence the consistent susceptibility. This enables calculation of the chiral susceptibility for markedly different vertex Ansaetze. For themore » two cases considered, the results were consistent and the minor quantitative differences easily understood. The susceptibility can be used to demarcate the domain of coupling strength within a theory upon which chiral symmetry is dynamically broken. Degenerate massless scalar and pseudoscalar bound-states appear at the critical coupling for dynamical chiral symmetry breaking.« less

Chiral susceptibility and the scalar Ward identity

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

Chang Lei; Liu Yuxin; Center of Theoretical Nuclear Physics, National Laboratory of Heavy Ion Accelerator, Lanzhou 730000

2009-03-15

The chiral susceptibility is given by the scalar vacuum polarization at zero total momentum. This follows directly from the expression for the vacuum quark condensate so long as a nonperturbative symmetry preserving truncation scheme is employed. For QCD in-vacuum the susceptibility can rigorously be defined via a Pauli-Villars regularization procedure. Owing to the scalar Ward identity, irrespective of the form or Ansatz for the kernel of the gap equation, the consistent scalar vertex at zero total momentum can automatically be obtained and hence the consistent susceptibility. This enables calculation of the chiral susceptibility for markedly different vertex Ansaetze. For themore » two cases considered, the results were consistent and the minor quantitative differences easily understood. The susceptibility can be used to demarcate the domain of coupling strength within a theory upon which chiral symmetry is dynamically broken. Degenerate massless scalar and pseudoscalar bound-states appear at the critical coupling for dynamical chiral symmetry breaking.« less

Chirality-dependent friction of bulk molecular solids.

PubMed

Yang, Dian; Cohen, Adam E

2014-08-26

We show that the solid-solid friction between bulk chiral molecular solids can depend on the relative chirality of the two materials. In menthol and 1-phenyl-1-butanol, heterochiral friction is smaller than homochiral friction, while in ibuprofen, heterochiral friction is larger. Chiral asymmetries in the coefficient of sliding friction vary with temperature and can be as large as 30%. In the three compounds tested, the sign of the difference between heterochiral and homochiral friction correlated with the sign of the difference in melting point between racemate (compound or conglomerate) and pure enantiomer. Menthol and ibuprofen each form a stable racemic compound, while 1-phenyl-1-butanol forms a racemic conglomerate. Thus, a difference between heterochiral and homochiral friction does not require the formation of a stable interfacial racemic compound. Measurements of chirality-dependent friction provide a unique means to distinguish the role of short-range intermolecular forces from all other sources of dissipation in the friction of bulk molecular solids.

Objects of Maximum Electromagnetic Chirality

NASA Astrophysics Data System (ADS)

Fernandez-Corbaton, Ivan; Fruhnert, Martin; Rockstuhl, Carsten

2016-07-01

We introduce a definition of the electromagnetic chirality of an object and show that it has an upper bound. Reciprocal objects attain the upper bound if and only if they are transparent for all the fields of one polarization handedness (helicity). Additionally, electromagnetic duality symmetry, i.e., helicity preservation upon interaction, turns out to be a necessary condition for reciprocal objects to attain the upper bound. We use these results to provide requirements for the design of such extremal objects. The requirements can be formulated as constraints on the polarizability tensors for dipolar objects or on the material constitutive relations for continuous media. We also outline two applications for objects of maximum electromagnetic chirality: a twofold resonantly enhanced and background-free circular dichroism measurement setup, and angle-independent helicity filtering glasses. Finally, we use the theoretically obtained requirements to guide the design of a specific structure, which we then analyze numerically and discuss its performance with respect to maximal electromagnetic chirality.

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.

The development of chiral nematic mesoporous materials.

PubMed

Kelly, Joel A; Giese, Michael; Shopsowitz, Kevin E; Hamad, Wadood Y; MacLachlan, Mark J

2014-04-15

Cellulose nanocrystals (CNCs) are obtained from the sulfuric acid-catalyzed hydrolysis of bulk cellulose. The nanocrystals have diameters of ~5-15 nm and lengths of ~100-300 nm (depending on the cellulose source and hydrolysis conditions). This lightweight material has mostly been investigated to reinforce composites and polymers because it has remarkable strength that rivals carbon nanotubes. But CNCs have an additional, less explored property: they organize into a chiral nematic (historically referred to as cholesteric) liquid crystal in water. When dried into a thin solid film, the CNCs retain the helicoidal chiral nematic order and assemble into a layered structure where the CNCs have aligned orientation within each layer, and their orientation rotates through the stack with a characteristic pitch (repeating distance). The cholesteric ordering can act as a 1-D photonic structure, selectively reflecting circularly polarized light that has a wavelength nearly matching the pitch. During CNC self-assembly, it is possible to add sol-gel precursors, such as Si(OMe)4, that undergo hydrolysis and condensation as the solvent evaporates, leading to a chiral nematic silica/CNC composite material. Calcination of the material in air destroys the cellulose template, leaving a high surface area mesoporous silica film that has pore diameters of ~3-10 nm. Importantly, the silica is brilliantly iridescent because the pores in its interior replicate the chiral nematic structure. These films may be useful as optical filters, reflectors, and membranes. In this Account, we describe our recent research into mesoporous films with chiral nematic order. Taking advantage of the chiral nematic order and nanoscale of the CNC templates, new functional materials can be prepared. For example, heating the silica/CNC composites under an inert atmosphere followed by removal of the silica leaves highly ordered, mesoporous carbon films that can be used as supercapacitor electrodes. The composition

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.

Chemical synthesis of chiral conducting polymers

DOEpatents

Wang, Hsing-Lin [Los Alamos, NM; Li, Wenguang [Los Alamos, NM

2009-01-13

An process of forming a chiral conducting polymer, e.g., polyaniline, is provided including reacting a monomer, e.g., an aniline monomer, in the presence of a chiral dopant acid to produce a first reaction mixture by addition of a solution including a first portion of an oxidizing agent, the first portion of oxidizing agent characterized as insufficient to allow complete reaction of the monomer, and further reacting the first reaction mixture in the presence of the chiral dopant acid by addition of a solution including a second portion of the oxidizing agent, the second portion of oxidizing agent characterized as insufficient to allow complete reaction of the monomer, and repeating the reaction by addition of further portions of the oxidizing agent until the monomer reaction is complete to produce a chiral conducting polymer, e.g., polyaniline. A preferred process includes addition of a catalyst during the reaction, the catalyst selected from among the group consisting of phenylene diamine, aniline oligomers and amino-capped aniline oligomers and metal salts.The processes of the present invention further provide a resultant polyaniline product having a chirality level defined by a molar ellipticity of from about 40.times.10.sup.3 degree-cm.sup.2/decimole to about 700.times.10.sup.3 degree-cm.sup.2/decimole. The processes of the present invention further provide a resultant polyaniline product having a nanofiber structure with a diameter of from about 30 nanometers to about 120 nanometers and from about 1 micron to about 5 microns in length.

High-Performance Ultrathin Active Chiral Metamaterials.

PubMed

Wu, Zilong; Chen, Xiaodong; Wang, Mingsong; Dong, Jianwen; Zheng, Yuebing

2018-05-22

Ultrathin active chiral metamaterials with dynamically tunable and responsive optical chirality enable new optical sensors, modulators, and switches. Herein, we develop ultrathin active chiral metamaterials of highly tunable chiroptical responses by inducing tunable near-field coupling in the metamaterials and exploit the metamaterials as ultrasensitive sensors to detect trace amounts of solvent impurities. To demonstrate the active chiral metamaterials mediated by tunable near-field coupling, we design moiré chiral metamaterials (MCMs) as model metamaterials, which consist of two layers of identical Au nanohole arrays stacked upon one another in moiré patterns with a dielectric spacer layer between the Au layers. Our simulations, analytical fittings, and experiments reveal that spacer-dependent near-field coupling exists in the MCMs, which significantly enhances the spectral shift and line shape change of the circular dichroism (CD) spectra of the MCMs. Furthermore, we use a silk fibroin thin film as the spacer layer in the MCM. With the solvent-controllable swelling of the silk fibroin thin films, we demonstrate actively tunable near-field coupling and chiroptical responses of the silk-MCMs. Impressively, we have achieved the spectral shift over a wavelength range that is more than one full width at half-maximum and the sign inversion of the CD spectra in a single ultrathin (1/5 of wavelength in thickness) MCM. Finally, we apply the silk-MCMs as ultrasensitive sensors to detect trace amounts of solvent impurities down to 200 ppm, corresponding to an ultrahigh sensitivity of >10 5 nm/refractive index unit (RIU) and a figure of merit of 10 5 /RIU.

Chemical synthesis of chiral conducting polymers

DOEpatents

Wang, Hsing-Lin; Li, Wenguang

2006-07-11

An process of forming a chiral conducting polymer, e.g., polyaniline, is provided including reacting a monomer, e.g., an aniline monomer, in the presence of a chiral dopant acid to produce a first reaction mixture by addition of a solution including a first portion of an oxidizing agent, the first portion of oxidizing agent characterized as insufficient to allow complete reaction of the monomer, and further reacting the first reaction mixture in the presence of the chiral dopant acid by addition of a solution including a second portion of the oxidizing agent, the second portion of oxidizing agent characterized as insufficient to allow complete reaction of the monomer, and repeating the reaction by addition of further portions of the oxidizing agent until the monomer reaction is complete to produce a chiral conducting polymer, e.g., polyaniline. A preferred process includes addition of a catalyst during the reaction, the catalyst selected from among the group consisting of phenylene diamine, aniline oligomers and amino-capped aniline oligomers and metal salts. The processes of the present invention further provide a resultant polyaniline product having a chirality level defined by a molar ellipticity of from about 40.times.10³ degree-cm²/decimole to about 700.times.10³ degree-cm²/decimole. The processes of the present invention further provide a resultant polyaniline product having a nanofiber structure with a diameter of from about 30 nanometers to about 120 nanometers and from about 1 micron to about 5 microns in length.

Coupling of non-aqueous electrokinetic chromatography using cationic cyclodextrins with electrospray ionization mass spectrometry.

PubMed

Mol, Roelof; de Jong, Gerhardus J; Somsen, Govert W

2008-01-01

Non-aqueous electrokinetic chromatography (NAEKC) using cationic cyclodextrins (CDs) was coupled to electrospray ionization mass spectrometry (ESI-MS). A methanolic background electrolyte (BGE) was used which contained the hydrochloride salts of the single-isomer derivative cyclodextrins 6-monodeoxy-6-mono(2-hydroxy)propylamino-beta-cyclodextrin (IPA-beta-CD) or 6-monodeoxy-6-mono(3-hydroxy)propylamino-beta-cyclodextrin (PA-beta-CD). Applying a reversed capillary electrophoresis (CE) polarity (-30 kV), efficient separation of negatively charged compounds was achieved with plate numbers of up to 190,000. PA-beta-CD appeared to be the most suitable for the separation of various acidic drugs while also providing a high chiral selectivity. Analyte detection was achieved by ESI-MS in the negative-ion mode using a sheath-liquid interface. In order to prevent current drops caused by the cathodic electroosmotic flow, a pressure of 15 mbar was applied on the inlet vial during NAEKC/MS analysis. The effect of the cationic CDs on the MS signal intensities of acidic test drugs was thoroughly studied. When a voltage is applied across the CE capillary, the overall mobility of the cationic CDs is towards the inlet vial so that no CD molecules enter the ion source. The chloride counter ions of the CDs, which migrated towards the capillary outlet, were found to cause ionization suppression, although significant analyte signals could still be detected. Depending on the CD concentration in the BGE, limits of detection for acidic drugs were in the 50-400 ng/mL range in full-scan mode.

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.

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.

Chiral Molecules Revisited by Broadband Microwave Spectroscopy

NASA Astrophysics Data System (ADS)

Schnell, Melanie

2014-06-01

Chiral molecules have fascinated chemists for more than 150 years. While their physical properties are to a very good approximation identical, the two enantiomers of a chiral molecule can have completely different (bio)chemical activities. For example, the right-handed enantiomer of carvone smells of spearmint while the left-handed one smells of caraway. In addition, the active components of many drugs are of one specific handedness, such as in the case of ibuprofen. However, in nature as well as in pharmaceutical applications, chiral molecules often exist in mixtures with other chiral molecules. The analysis of these complex mixtures to identify the molecular components, to determine which enantiomers are present, and to measure the enantiomeric excesses (ee) remains a challenging task for analytical chemistry, despite its importance for modern drug development. We present here a new method of differentiating enantiomers of chiral molecules in the gas phase based on broadband rotational spectroscopy. The phase of the acquired signal bares the signature of the enantiomer, as it depends upon the combined quantity, μ_a μ_b μ_c, which is of opposite sign between enantiomers. It thus also provides information on the absolute configuration of the particular enantiomer. Furthermore, the signal amplitude is proportional to the ee. A significant advantage of our technique is its inherent mixture compatibility due to the fingerprint-like character of rotational spectra. In this contribution, we will introduce the technique and present our latest results on chiral molecule spectroscopy and enantiomer differentiation. D. Patterson, M. Schnell, J.M. Doyle, Nature 497 (2013) 475-477 V.A. Shubert, D. Schmitz, D. Patterson, J.M. Doyle, M. Schnell, Angewandte Chemie International Edition 53 (2014) 1152-1155

The cation-π interaction.

PubMed

Dougherty, Dennis A

2013-04-16

The chemistry community now recognizes the cation-π interaction as a major force for molecular recognition, joining the hydrophobic effect, the hydrogen bond, and the ion pair in determining macromolecular structure and drug-receptor interactions. This Account provides the author's perspective on the intellectual origins and fundamental nature of the cation-π interaction. Early studies on cyclophanes established that water-soluble, cationic molecules would forego aqueous solvation to enter a hydrophobic cavity if that cavity was lined with π systems. Important gas phase studies established the fundamental nature of the cation-π interaction. The strength of the cation-π interaction (Li(+) binds to benzene with 38 kcal/mol of binding energy; NH4(+) with 19 kcal/mol) distinguishes it from the weaker polar-π interactions observed in the benzene dimer or water-benzene complexes. In addition to the substantial intrinsic strength of the cation-π interaction in gas phase studies, the cation-π interaction remains energetically significant in aqueous media and under biological conditions. Many studies have shown that cation-π interactions can enhance binding energies by 2-5 kcal/mol, making them competitive with hydrogen bonds and ion pairs in drug-receptor and protein-protein interactions. As with other noncovalent interactions involving aromatic systems, the cation-π interaction includes a substantial electrostatic component. The six (four) C(δ-)-H(δ+) bond dipoles of a molecule like benzene (ethylene) combine to produce a region of negative electrostatic potential on the face of the π system. Simple electrostatics facilitate a natural attraction of cations to the surface. The trend for (gas phase) binding energies is Li(+) > Na(+) > K(+) > Rb(+): as the ion gets larger the charge is dispersed over a larger sphere and binding interactions weaken, a classical electrostatic effect. On other hand, polarizability does not define these interactions. Cyclohexane is

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

Examination of the potential for adaptive chirality of the nitrogen chiral center in aza-aspartame.

PubMed

Bouayad-Gervais, Samir H; Lubell, William D

2013-11-28

The potential for dynamic chirality of an azapeptide nitrogen was examined by substitution of nitrogen for the α-carbon of the aspartate residue in the sweetener S,S-aspartame. Considering that S,S- and R,S-aspartame possess sweet and bitter tastes, respectively, a bitter-sweet taste of aza-aspartame 9 could be indicative of a low isomerization barrier for nitrogen chirality inter-conversion. Aza-aspartame 9 was synthesized by a combination of hydrazine and peptide chemistry. Crystallization of 9 indicated a R,S-configuration in the solid state; however, the aza-residue chiral center was considerably flattened relative to its natural amino acid counterpart. On tasting, the authors considered aza-aspartame 9 to be slightly bitter or tasteless. The lack of bitter sweet taste of aza-aspartame 9 may be due to flattening from sp2 hybridization in the urea as well as a high barrier for sp3 nitrogen inter-conversion, both of which may interfere with recognition by taste receptors.

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.

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

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, ...

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.

Light-Nuclei Spectra from Chiral Dynamics

NASA Astrophysics Data System (ADS)

Piarulli, M.; Baroni, A.; Girlanda, L.; Kievsky, A.; Lovato, A.; Lusk, Ewing; Marcucci, L. E.; Pieper, Steven C.; Schiavilla, R.; Viviani, M.; Wiringa, R. B.

2018-02-01

In recent years local chiral interactions have been derived and implemented in quantum Monte Carlo methods in order to test to what extent the chiral effective field theory framework impacts our knowledge of few- and many-body systems. In this Letter, we present Green's function Monte Carlo calculations of light nuclei based on the family of local two-body interactions presented by our group in a previous paper in conjunction with chiral three-body interactions fitted to bound- and scattering-state observables in the three-nucleon sector. These interactions include Δ intermediate states in their two-pion-exchange components. We obtain predictions for the energy levels and level ordering of nuclei in the mass range A =4 - 12 , accurate to ≤2 % of the binding energy, in very satisfactory agreement with experimental data.

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...

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.

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

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.

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

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.

Synthetic cation-selective nanotube: permeant cations chaperoned by anions.

PubMed

Hilder, Tamsyn A; Gordon, Dan; Chung, Shin-Ho

2011-01-28

The ability to design ion-selective, synthetic nanotubes which mimic biological ion channels may have significant implications for the future treatment of bacteria, diseases, and as ultrasensitive biosensors. We present the design of a synthetic nanotube made from carbon atoms that selectively allows monovalent cations to move across and rejects all anions. The cation-selective nanotube mimics some of the salient properties of biological ion channels. Before practical nanodevices are successfully fabricated it is vital that proof-of-concept computational studies are performed. With this in mind we use molecular and stochastic dynamics simulations to characterize the dynamics of ion permeation across a single-walled (10, 10), 36 Å long, carbon nanotube terminated with carboxylic acid with an effective radius of 5.08 Å. Although cations encounter a high energy barrier of 7 kT, its height is drastically reduced by a chloride ion in the nanotube. The presence of a chloride ion near the pore entrance thus enables a cation to enter the pore and, once in the pore, it is chaperoned by the resident counterion across the narrow pore. The moment the chaperoned cation transits the pore, the counterion moves back to the entrance to ferry another ion. The synthetic nanotube has a high sodium conductance of 124 pS and shows linear current-voltage and current-concentration profiles. The cation-anion selectivity ratio ranges from 8 to 25, depending on the ionic concentrations in the reservoirs.

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.

Chiral cavity ring down polarimetry: Chirality and magnetometry measurements using signal reversals.

PubMed

Bougas, Lykourgos; Sofikitis, Dimitris; Katsoprinakis, Georgios E; Spiliotis, Alexandros K; Tzallas, Paraskevas; Loppinet, Benoit; Rakitzis, T Peter

2015-09-14

We present the theory and experimental details for chiral-cavity-ring-down polarimetry and magnetometry, based on ring cavities supporting counterpropagating laser beams. The optical-rotation symmetry is broken by the presence of both chiral and Faraday birefringence, giving rise to signal reversals which allow rapid background subtractions. We present the measurement of the specific rotation at 800 nm of vapors of α-pinene, 2-butanol, and α-phellandrene, the measurement of optical rotation of sucrose solutions in a flow cell, the measurement of the Verdet constant of fused silica, and measurements and theoretical treatment of evanescent-wave optical rotation at a prism surface. Therefore, these signal-enhancing and signal-reversing methods open the way for ultrasensitive polarimetry measurements in gases, liquids and solids, and at surfaces.

The Cation-π Interaction

PubMed Central

DOUGHERTY, DENNIS A.

2014-01-01

CONSPECTUS The chemistry community now recognizes the cation-π interaction as a major force for molecular recognition, joining the hydrophobic effect, the hydrogen bond, and the ion pair in determining macromolecular structure and drug-receptor interactions. This Account provides the author’s perspective on the intellectual origins and fundamental nature of the cation-π interaction. Early studies on cyclophanes established that water-soluble, cationic molecules would forgo aqueous solvation to enter a hydrophobic cavity if that cavity was lined with π systems. Important gas phase studies established the fundamental nature of the cation-π interaction. The strength of the cation-π interaction – Li+ binds to benzene with 38 kcal/mol of binding energy; NH4+ with 19 kcal/mol– distinguishes it from the weaker polar-π interactions observed in the benzene dimer or water-benzene complexes. In addition to the substantial intrinsic strength of the cation-π interaction in gas phase studies, the cation-π interaction remains energetically significant in aqueous media and under biological conditions. Many studies have shown that cation-π interactions can enhance binding energies by 2 – 5 kcal/mol, making them competitive with hydrogen bonds and ion pairs in drug-receptor and protein-protein interactions. As with other noncovalent interactions involving aromatic systems, the cation-π interaction includes a substantial electrostatic component. The six (four) Cδ−–Hδ+ bond dipoles of a molecule like benzene (ethylene) combine to produce a region of negative electrostatic potential on the face of the π system. Simple electrostatics facilitate a natural attraction of cations to the surface. The trend for (gas phase) binding energies is Li+>Na+>K+>Rb+: as the ion gets larger the charge is dispersed over a larger sphere and binding interactions weaken, a classical electrostatic effect. On other hand, polarizability does not define these interactions. Cyclohexane

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.

Chiral Sensitivity in Electron-Molecule Interactions

NASA Astrophysics Data System (ADS)

Dreiling, Joan

2015-09-01

All molecular forms of life possess a chiral asymmetry, with amino acids and sugars found respectively in L- and D-enantiomers only. The primordial origin of this enantiomeric excess is unknown. One possible explanation is given by the Vester- Ulbricht hypothesis, which suggests that left-handed electrons present in beta-radiation, produced by parity-violating weak decays, interacted with biological precursors and preferentially destroyed one of the two enantiomers. Experimental tests of this idea have thus far yielded inconclusive results. We show direct evidence for chirally-dependent bond breaking through a dissociative electron attachment (DEA) reaction when spin-polarized electrons are incident on gas-phase chiral molecules. This provides unambiguous evidence for a well-defined, chirally-sensitive destructive molecular process and, as such, circumstantial evidence for the Vester-Ulbricht hypothesis. I will also present the results of our systematic study of the DEA asymmetry for different chiral halocamphor molecules. Three halocamphor molecules were investigated: 3-bromocamphor (C10H15BrO), 3-iodocamphor(C10H15IO), and 10-iodocamphor. The DEA asymmetries collected for bromocamphor and iodocamphor are qualitatively different, suggesting that the atomic number of the heaviest atom in the molecule plays a crucial role in the asymmetric interactions. The DEA asymmetry data for 3- and 10-iodocamphor have the same qualitative behavior, but the 10-iodocamphor asymmetry is about twice as large at the lowest energies investigated, so the location of the heavy atom in the camphor molecule also affects the asymmetries. This work was performed at the University of Nebraska-Lincoln. This project is funded by NSF Grant PHY-1206067.

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...

Combined use of chiral ionic liquid surfactants and neutral cyclodextrins: evaluation of ionic liquid head groups for enantioseparation of neutral compounds in capillary electrophoresis.

PubMed

Liu, Yijin; Shamsi, Shahab A

2014-09-19

Cyclodextrins (CDs) are most commonly used chiral selectors in capillary electrophoresis (CE). Although the use of neutral CDs and its derivatives have shown to resolve plethora of charged enantiomers, they cannot resolve neutral enantiomers. The use of ionic liquids (ILs) surfactants forming successful complex with CDs present itself an opportunity to resolve neutral enantiomers. In this work, the effect of IL head groups and their complexation ability with heptakis (2,3,6-tri-O-methyl)-β-cyclodextrin (TM-β-CD) was studied for the separation of neutral enantiomers by CE. First, cationic IL type surfactants with different chiral head groups were synthesized. Physicochemical properties such as critical micelle concentration were determined by surface tension, whereas aggregation and polarity were determined by fluorescence spectroscopy. The complexation ability of ILs with TM-β-CD was characterized in the gas phase by CE-mass spectrometry. The influence of the type of ILs head group and its concentration on chiral resolution, resolution per unit time and selectivity were investigated for four structurally diverse neutral compounds. The binding constants of the neutral analytes to the IL-CD complex were estimated by y-reciprocal method. The hydrophobicity of the side chain of the IL head group displayed significant effect on the binding constants and enantioseparations. Copyright © 2014 Elsevier B.V. All rights reserved.

Intrinsic chirality and prochirality at Air/R-(+)- and S-(-)-limonene interfaces: spectral signatures with interference chiral sum-frequency generation vibrational spectroscopy.

PubMed

Fu, Li; Zhang, Yun; Wei, Zhe-Hao; Wang, Hong-Fei

2014-09-01

We report in this work detailed measurements of the chiral and achiral sum-frequency vibrational spectra in the C-H stretching vibration region (2800-3050 cm(-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 RS racemic mixture (50/50 equal amount mixture), show that the corresponding molecular groups of the R and S enantiomers are with the same interfacial orientations. The interference chiral SFG spectra of the limonene enantiomers exhibit a spectral signature from the chiral response of the Cα-H stretching mode, and a spectral signature from the prochiral response of the CH(2) asymmetric stretching mode, respectively. The chiral spectral feature of the Cα-H stretching mode changes sign from R-(+)-limonene to S-(-)-limonene surfaces, and disappears for the RS racemic mixture surface. While the prochiral spectral feature of the CH(2) asymmetric stretching mode is the same for R-(+)-limonene and S-(-)-limonene surfaces, and also surprisingly remains the same for the RS racemic mixture surface. Therefore, the structures of the R-(+)-limonene and the S-(-)-limonene at the liquid interfaces are nevertheless not mirror images to each other, even though the corresponding groups have the same tilt angle from the interfacial normal, i.e., the R-(+)-limonene and the S-(-)-limonene at the surface are diastereomeric instead of enantiomeric. These results provide detailed information in understanding the structure and chirality of molecular interfaces and demonstrate the sensitivity and potential of SFG-VS as a unique spectroscopic tool for chirality characterization and chiral recognition at the molecular interface. © 2014 Wiley Periodicals, Inc.

Light-Nuclei Spectra from Chiral Dynamics

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

Piarulli, M.; Baroni, A.; Girlanda, L.

In recent years local chiral interactions have been derived and implemented in quantum Monte Carlo methods in order to test to what extent the chiral effective field theory framework impacts our knowledge of few- and many-body systems. Here in this Letter, we present Green’s function Monte Carlo calculations of light nuclei based on the family of local two-body interactions presented by our group in a previous paper in conjunction with chiral three-body interactions fitted to bound- and scattering-state observables in the three-nucleon sector. These interactions include Δ intermediate states in their two-pion-exchange components. We obtain predictions for the energy levelsmore » and level ordering of nuclei in the mass range A=4–12, accurate to ≤2% of the binding energy, in very satisfactory agreement with experimental data.« less

Light-Nuclei Spectra from Chiral Dynamics

DOE PAGES

Piarulli, M.; Baroni, A.; Girlanda, L.; ...

2018-02-01

In recent years local chiral interactions have been derived and implemented in quantum Monte Carlo methods in order to test to what extent the chiral effective field theory framework impacts our knowledge of few- and many-body systems. Here in this Letter, we present Green’s function Monte Carlo calculations of light nuclei based on the family of local two-body interactions presented by our group in a previous paper in conjunction with chiral three-body interactions fitted to bound- and scattering-state observables in the three-nucleon sector. These interactions include Δ intermediate states in their two-pion-exchange components. We obtain predictions for the energy levelsmore » and level ordering of nuclei in the mass range A=4–12, accurate to ≤2% of the binding energy, in very satisfactory agreement with experimental data.« less

Spin-orbit beams for optical chirality measurement

NASA Astrophysics Data System (ADS)

Samlan, C. T.; Suna, Rashmi Ranjan; Naik, Dinesh N.; Viswanathan, Nirmal K.

2018-01-01

Accurate measurement of chirality is essential for the advancement of natural and pharmaceutical sciences. We report here a method to measure chirality using non-separable states of light with geometric phase-gradient in the circular polarization basis, which we refer to as spin-orbit beams. A modified polarization Sagnac interferometer is used to generate spin-orbit beams wherein the spin and orbital angular momentum of the input Gaussian beam are coupled. The out-of-phase interference between counter-propagating Gaussian beams with orthogonal spin states and lateral-shear or/and linear-phase difference between them results in spin-orbit beams with linear and azimuthal phase gradient. The spin-orbit beams interact efficiently with the chiral medium, inducing a measurable change in the center-of-mass of the beam, using the polarization rotation angle and hence the chirality of the medium are accurately calculated. Tunable dynamic range of measurement and flexibility to introduce large values of orbital angular momentum for the spin-orbit beam, to improve the measurement sensitivity, highlight the techniques' versatility.

Chiral higher spin theories and self-duality

NASA Astrophysics Data System (ADS)

Ponomarev, Dmitry

2017-12-01

We study recently proposed chiral higher spin theories — cubic theories of interacting massless higher spin fields in four-dimensional flat space. We show that they are naturally associated with gauge algebras, which manifest themselves in several related ways. Firstly, the chiral higher spin equations of motion can be reformulated as the self-dual Yang-Mills equations with the associated gauge algebras instead of the usual colour gauge algebra. We also demonstrate that the chiral higher spin field equations, similarly to the self-dual Yang-Mills equations, feature an infinite algebra of hidden symmetries, which ensures their integrability. Secondly, we show that off-shell amplitudes in chiral higher spin theories satisfy the generalised BCJ relations with the usual colour structure constants replaced by the structure constants of higher spin gauge algebras. We also propose generalised double copy procedures featuring higher spin theory amplitudes. Finally, using the light-cone deformation procedure we prove that the structure of the Lagrangian that leads to all these properties is universal and follows from Lorentz invariance.

No-Drag Frame for Anomalous Chiral Fluid

DOE PAGES

Stephanov, Mikhail A.; Yee, Ho-Ung

2016-03-24

For an anomalous fluid carrying dissipationless chiral magnetic and/or vortical currents we show that there is a frame in which a stationary obstacle experiences no drag, but energy and charge currents do not vanish, resembling superfluidity. Unlike ordinary superfluid flow, the anomalous chiral currents can transport entropy in this frame. Moreover, we show that the second law of thermodynamics completely determines the amounts of these anomalous nondissipative currents in the “no-drag frame” as polynomials in temperature and chemical potential with known anomaly coefficients. These general results are illustrated and confirmed by a calculation in the chiral kinetic theory and inmore » the quark-gluon plasma at high temperature.« less

Chiral symmetry and the nucleon-nucleon interaction

DOE PAGES

Machleidt, Ruprecht

2016-04-20

We review how nuclear forces emerge from low-energy quantum chromodynamics (QCD) via chiral effective field theory (EFT). During the past two decades, this approach has evolved into a powerful tool to derive nuclear two- and many-body forces in a systematic and model-independent way. We then focus on the nucleon-nucleon (NN) interaction and show in detail how, governed by chiral symmetry, the long- and intermediate-range of the NN potential builds up order by order. We proceed up to sixth order in small momenta, where convergence is achieved. Lastly, the final result allows for a full assessment of the validity of themore » chiral EFT approach to the NN interaction.« less

Chiral Spin Order in Kondo-Heisenberg Systems

NASA Astrophysics Data System (ADS)

Tsvelik, A. M.; Yevtushenko, O. M.

2017-12-01

We demonstrate that low dimensional Kondo-Heisenberg systems, consisting of itinerant electrons and localized magnetic moments (Kondo impurities), can be used as a principally new platform to realize scalar chiral spin order. The underlying physics is governed by a competition of the Ruderman-Kittel-Kosuya-Yosida (RKKY) indirect exchange interaction between the local moments with the direct Heisenberg one. When the direct exchange is weak and RKKY dominates, the isotropic system is in the disordered phase. A moderately large direct exchange leads to an Ising-type phase transition to the phase with chiral spin order. Our finding paves the way towards pioneering experimental realizations of the chiral spin liquid in systems with spontaneously broken time-reversal symmetry.

A Ni(II) Bis(diphosphine)-Hydride Complex Containing Proton Relays - Structural Characterization and Electrocatalytic Studies

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

Das, Partha Pratim; Stolley, Ryan M.; Van Der Eide, Edwin F.

The syntheses of the new 1,5-diphenyl-3,7-di(isopropyl)-1,5-diaza-3,7-diphosphacyclooctane ligand, PiPr2NPh2, is reported. The two equivalents of the ligand react with [Ni(CH3CN)6](BF4)2 to form the bis-diphosphine Ni(II)-complex [Ni(PiPr2NPh2)2](BF4)2, which acts as a proton reduction electrocatalyst. In addition to [Ni(PiPr2NPh2)2]2+, we report the syntheses and structural characterization of the Ni(0)-complex Ni(PiPr2NPh2)2, and the Ni(II)-hydride complex [HNi(PiPr2NPh2)2]BF4. The [HNi(PiPr2NPh2)2]BF4 complex represents the first Ni(II)-hydride in the [Ni(PR2NR'2)2]2+ family of compounds to be isolated and structurally characterized. In addition to the experimental data, the mechanism of electrocatalysis facilitated by [Ni(PiPr2NPh2)2]2+ is analyzed using linear free energy relationships recently established for the [Ni(PR2NR'2)2]2+ family. We thank Dr.more » Aaron Appel, Dr. Simone Raugei and Dr. Eric Wiedner for helpful discussions. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Mass spectrometry was provided at W. R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy’s office of Biological and Environmental Research located at Pacific Northwest National Laboratory. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.« less

Chiral monolithic absorbent constructed by optically active helical-substituted polyacetylene and graphene oxide: preparation and chiral absorption capacity.

PubMed

Li, Weifei; Wang, Bo; Yang, Wantai; Deng, Jianping

2015-02-01

Chiral monolithic absorbent is successfully constructed for the first time by using optically active helical-substituted polyacetylene and graphene oxide (GO). The preparative strategy is facile and straightforward, in which chiral-substituted acetylene monomer (Ma), cross-linker (Mb), and alkynylated GO (Mc) undergo copolymerization to form the desired monolithic absorbent in quantitative yield. The resulting monoliths are characterized by circular dichroism, UV-vis absorption, scanning electron microscopy (SEM), FT-IR, Raman, energy-dispersive spectrometer (EDS), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), XPS, and thermogravimetric analysis (TGA) techniques. The polymer chains derived from Ma form chiral helical structures and thus provide optical activity to the monoliths, while GO sheets contribute to the formation of porous structures. The porous structure enables the monolithic absorbents to demonstrate a large swelling ratio in organic solvents, and more remarkably, the helical polymer chains provide optical activity and further enantio-differentiating absorption ability. The present study establishes an efficient and versatile methodology for preparing novel functional materials, in particular monolithic chiral materials based on substituted polyacetylene and GO. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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 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.

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

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.

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.

Near-unity thermally activated delayed fluorescence efficiency in three- and four-coordinate Au(i) complexes with diphosphine ligands.

PubMed

Osawa, Masahisa; Aino, Masa-Aki; Nagakura, Takaki; Hoshino, Mikio; Tanaka, Yuya; Akita, Munetaka

2018-05-14

The synthesis and photoluminescence properties of three-coordinate Au(i) complexes with rigid diphosphine ligands LMe {1,2-bis[bis(2-methylphenyl)phosphino]benzene}, LEt {1,2-bis[bis(2-ethylphenyl)phosphino]benzene}, and LiPr {1,2-bis[bis(2-isopropylphenyl)phosphino]benzene} are investigated. The LMe and LEt ligands afford two types of complexes: dinuclear complexes [μ-LMe(AuCl)2] (1d) and [μ-LEt(AuCl)2] (2d) with an Au(i)-Au(i) bond and mononuclear three-coordinate Au(i) complexes LMeAuCl (1) and LEtAuCl (2). On the other hand, the bulkiest ligand, LiPr, affords three-coordinate Au(i) complexes, LiPrAuCl (3) and LiPrAuI (4), but no dinuclear complexes. X-ray analysis suggests that both 3 and 4 possess a highly distorted trigonal planar geometry. Moreover, luminescence data reveal that at room temperature, 3 and 4 exhibit yellow-green thermally activated delayed fluorescence in the crystalline state with maximum emission wavelengths at 558 and 549 nm, respectively. The emission yields are close to unity. Quantum chemical calculations suggest that the emission of 4 originates from the (σ + X) → π* excited state that possesses strong intraligand charge-transfer character. The luminescent properties of four-coordinate Au(i) complex (5) possessing a tetrahedral geometry are discussed on the basis of the emission spectra and decay times measured in a temperature range of 309-77 K.

The chiral separation of triazole pesticides enantiomers by amylose-tris (3,5-dimethylphenylcarbamate) chiral stationary phase.

PubMed

Wang, Peng; Liu, Donghui; Jiang, Shuren; Xu, Yangguang; Zhou, Zhiqiang

2008-10-01

The amylose-tris(3,5-dimethylphenylcarbamate) chiral stationary phase was synthesized and used to separate the enantiomers of triazole pesticides by high-performance liquid chromatography. The mobile phase was n-hexane-isopropanol applying a flow rate of 1.0 mL/min. Six triazole pesticides were enantioselectively separated. Myclobutanil, paclobutrazol, tebuconazole, and uniconazole obtained complete separation with the resolution factors of 5.73, 2.99, 1.72, and 2.07, respectively, and imazalil and diniconazole obtained partial separation with the resolution factors of 0.79 and 0.77 under the optimized conditions. The effect of the content of isopropanol as well as column temperature on the separation was investigated. A circular dichroism detector was used to identify the enantiomers and determine the elution orders. The results showed the low temperature was good for the chiral separation except for diniconazole. The thermodynamic parameters calculated based on linear Van't Hoff plots showed the chiral separations were controlled by enthalpy.

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.

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

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

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.

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.

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.

Structural Composites With Tuned EM Chirality

DTIC Science & Technology

2014-12-23

photonic   crystals .   Tammuz  Dubnov  (7/14  –  9/14)  –  Laboratory  Assistant  -­‐  assisted in the testing...AFRL-OSR-VA-TR-2015-0018 STRUCTURAL COMPOSITES WITH TUNED EM CHIRALITY Siavouche Nemat Nasser UNIVERSITY OF CALIFORNIA SAN DIEGO Final Report 12/23...REPORT Grant/Contract  Title:        STRUCTURAL  COMPOSITES  WITH  TUNED  EM   CHIRALITY     Grant  No.:

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.

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.

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.

Surface defects and chiral algebras

NASA Astrophysics Data System (ADS)

Córdova, Clay; Gaiotto, Davide; Shao, Shu-Heng

2017-05-01

We investigate superconformal surface defects in four-dimensional N=2 superconformal theories. Each such defect gives rise to a module of the associated chiral algebra and the surface defect Schur index is the character of this module. Various natural chiral algebra operations such as Drinfeld-Sokolov reduction and spectral flow can be interpreted as constructions involving four-dimensional surface defects. We compute the index of these defects in the free hypermultiplet theory and Argyres-Douglas theories, using both infrared techniques involving BPS states, as well as renormalization group flows onto Higgs branches. In each case we find perfect agreement with the predicted characters.

Phonon Dispersion in Chiral Single-Wall Carbon Nanotubes

NASA Astrophysics Data System (ADS)

Mu, Weihua; Vamivakas, Anthony Nickolas; Fang, Yan; Wang, Bolin

The method to obtain phonon dispersion of achiral single-wall carbon nanotubes (SWNTs) from 6×6 matrix proposed by Mahan and Jeon7 has been extended to chiral SWNTs. The number of calculated phonon modes of a chiral SWNT (10, 1) is much larger than that of a zigzag one (10, 0) because the number of atoms in the translational unit cell of chiral SWNT is larger than that of an achiral one even though they have relative similar radius. The possible application of our approach to other models with more phonon potential terms beyond Mahan and Jeon's model is discussed.

Two-dimensional chiral topological superconductivity in Shiba lattices

PubMed Central

Li, Jian; Neupert, Titus; Wang, Zhijun; MacDonald, A. H.; Yazdani, A.; Bernevig, B. Andrei

2016-01-01

The chiral p-wave superconductor is the archetypal example of a state of matter that supports non-Abelian anyons, a highly desired type of exotic quasiparticle. With this, it is foundational for the distant goal of building a topological quantum computer. While some candidate materials for bulk chiral superconductors exist, they are subject of an ongoing debate about their actual paring state. Here we propose an alternative route to chiral superconductivity, consisting of the surface of an ordinary superconductor decorated with a two-dimensional lattice of magnetic impurities. We furthermore identify a promising experimental platform to realize this proposal. PMID:27465127

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?

Chiral Spin Order in Kondo-Heisenberg systems

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

Tsvelik, A. M.; Yevtushenko, O. M.

We demonstrate that Kondo-Heisenberg systems, consisting of itinerant electrons and localized magnetic moments (Kondo impurities), can be used as a principally new platform to realize scalar chiral spin order. The underlying physics is governed by a competition of the Ruderman-Kittel- Kosuya-Yosida (RKKY) indirect exchange interaction between the local moments with the direct Heisenberg one. When the direct exchange is weak and RKKY dominates the isotropic system is in the disordered phase. A moderately large direct exchange leads to an Ising-type phase transition to the phase with chiral spin order. Our nding paves the way towards pioneering experimental realizations of themore » chiral spin liquid in low dimensional systems with spontaneously broken time reversal symmetry.« less

Chiral Spin Order in Kondo-Heisenberg systems

DOE PAGES

Tsvelik, A. M.; Yevtushenko, O. M.

2017-12-15

We demonstrate that Kondo-Heisenberg systems, consisting of itinerant electrons and localized magnetic moments (Kondo impurities), can be used as a principally new platform to realize scalar chiral spin order. The underlying physics is governed by a competition of the Ruderman-Kittel- Kosuya-Yosida (RKKY) indirect exchange interaction between the local moments with the direct Heisenberg one. When the direct exchange is weak and RKKY dominates the isotropic system is in the disordered phase. A moderately large direct exchange leads to an Ising-type phase transition to the phase with chiral spin order. Our nding paves the way towards pioneering experimental realizations of themore » chiral spin liquid in low dimensional systems with spontaneously broken time reversal symmetry.« less

Fluconazole affects the alkali-metal-cation homeostasis and susceptibility to cationic toxic compounds of Candida glabrata.

PubMed

Elicharova, Hana; Sychrova, Hana

2014-08-01

Candida glabrata is a salt-tolerant and fluconazole (FLC)-resistant yeast species. Here, we analyse the contribution of plasma-membrane alkali-metal-cation exporters, a cation/proton antiporter and a cation ATPase to cation homeostasis and the maintenance of membrane potential (ΔΨ). Using a series of single and double mutants lacking CNH1 and/or ENA1 genes we show that the inability to export potassium and toxic alkali-metal cations leads to a slight hyperpolarization of the plasma membrane of C. glabrata cells; this hyperpolarization drives more cations into the cells and affects cation homeostasis. Surprisingly, a much higher hyperpolarization of C. glabrata plasma membrane was produced by incubating cells with subinhibitory concentrations of FLC. FLC treatment resulted in a substantially increased sensitivity of cells to various cationic drugs and toxic cations that are driven into the cell by negative-inside plasma-membrane potential. The effect of the combination of FLC plus cationic drug treatment was enhanced by the malfunction of alkali-metal-cation transporters that contribute to the regulation of membrane potential and cation homeostasis. In summary, we show that the combination of subinhibitory concentrations of FLC and cationic drugs strongly affects the growth of C. glabrata cells. © 2014 The Authors.

Graphene chiral liquid crystals and macroscopic assembled fibres

PubMed Central

Xu, Zhen; Gao, Chao

2011-01-01

Chirality and liquid crystals are both widely expressed in nature and biology. Helical assembly of mesophasic molecules and colloids may produce intriguing chiral liquid crystals. To date, chiral liquid crystals of 2D colloids have not been explored. As a typical 2D colloid, graphene is now receiving unprecedented attention. However, making macroscopic graphene fibres is hindered by the poor dispersibility of graphene and by the lack of an assembly method. Here we report that soluble, chemically oxidized graphene or graphene oxide sheets can form chiral liquid crystals in a twist-grain-boundary phase-like model with simultaneous lamellar ordering and long-range helical frustrations. Aqueous graphene oxide liquid crystals were continuously spun into metres of macroscopic graphene oxide fibres; subsequent chemical reduction gave the first macroscopic neat graphene fibres with high conductivity and good mechanical performance. The flexible, strong graphene fibres were knitted into designed patterns and into directionally conductive textiles. PMID:22146390

Metabolism studies of chiral pesticides: A critical review.

PubMed

de Albuquerque, Nayara Cristina Perez; Carrão, Daniel Blascke; Habenschus, Maísa Daniela; de Oliveira, Anderson Rodrigo Moraes

2018-01-05

The consumption of pesticides worldwide has been growing in recent decades, and consequently the exposure of humans and other animals to them as well. However, even though it is known that chiral pesticides can behave stereoselectively, the knowledge about the risks to human health and the environment is scarce. Among the pesticides registered to date, approximately 30% have at least one center of asymmetry, and just 7% of them are currently marketed as a pure stereoisomer or as an enriched mixture of the active stereoisomer. There are several in vitro, in vivo, and in silico models available to evaluate the enantioselective metabolism of chiral pesticides aiming ecotoxicological and risk assessment. Therefore, this paper intends to provide a critical view of the metabolism of chiral pesticides in non-target species, including humans, and discuss their implications, as well as, conduct a review of the analytical techniques employed for in vitro and in vivo metabolism studies of chiral pesticides. Copyright © 2017 Elsevier B.V. All rights reserved.

Pressure-induced cation-cation bonding in V 2 O 3

DOE PAGES

Bai, Ligang; Li, Quan; Corr, Serena A.; ...

2015-10-09

A pressure-induced phase transition, associated with the formation of cation-cation bonding, occurs in V 2O 3 by combining synchroton x-ray diffraction in a diamond anvil cell and ab initio evolutionary calculations. The high-pressure phase has a monoclinic structure with a C2/c space group, and it is both energetically and dynamically stable at pressures above 47 GPa to at least 105 GPa. this phase transition can be viewed as a two-dimensional Peierls-like distortion, where the cation-cation dimer chains are connected along the c axis of the monoclinic cell. In conclusion, this finding provides insights into the interplay of electron correlation andmore » lattice distortion in V 2O 3, and it may also help to understand novel properties of other early transition-metal oxides.« 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.

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.

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.

Chiral quantum optics.

PubMed

Lodahl, Peter; Mahmoodian, Sahand; Stobbe, Søren; Rauschenbeutel, Arno; Schneeweiss, Philipp; Volz, Jürgen; Pichler, Hannes; Zoller, Peter

2017-01-25

Advanced photonic nanostructures are currently revolutionizing the optics and photonics that underpin applications ranging from light technology to quantum-information processing. The strong light confinement in these structures can lock the local polarization of the light to its propagation direction, leading to propagation-direction-dependent emission, scattering and absorption of photons by quantum emitters. The possibility of such a propagation-direction-dependent, or chiral, light-matter interaction is not accounted for in standard quantum optics and its recent discovery brought about the research field of chiral quantum optics. The latter offers fundamentally new functionalities and applications: it enables the assembly of non-reciprocal single-photon devices that can be operated in a quantum superposition of two or more of their operational states and the realization of deterministic spin-photon interfaces. Moreover, engineered directional photonic reservoirs could lead to the development of complex quantum networks that, for example, could simulate novel classes of quantum many-body systems.

Combined use of chiral ionic liquid and cyclodextrin for MEKC: Part I. Simultaneous enantioseparation of anionic profens.

PubMed

Wang, Bin; He, Jun; Bianchi, Victoria; Shamsi, Shahab A

2009-08-01

The enantiomers of five profen drugs were simultaneously separated by MEKC with the combined use of 2,3,6-tri-O-methyl-beta-cyclodextrin and chiral cationic ionic liquid, N-undecenoxy-carbonyl-L-leucinol bromide, which formed micelles in aqueous buffers. Enantioseparations of these profen drugs were optimized by varying the chain length and concentration of the IL surfactant using a standard recipe containing 35 mM 2,3,6-tri-O-methyl-beta-cyclodextrin, 5 mM sodium acetate at pH 5.0. The batch-to-batch reproducibility of N-undecenoxy-carbonyl-L-leucinol bromide was tested and found to have no significant impact in terms of enantiomeric resolution, efficiency, and migration time. Finally, this method was successfully applied for the quantitative determination of ibuprofen in pharmaceutical tablets.

Combined use of chiral ionic liquid and cyclodextrin for MEKC: Part I. Simultaneous enantioseparation of anionic profens

PubMed Central

Wang, Bin; He, Jun; Bianchi, Victoria; Shamsi, Shahab A.

2009-01-01

The enantiomers of five profen (PROF) drugs were simultaneously separated by MEKC with the combined use of 2, 3, 6-tri-O-methyl-β-cyclodextrin (TM-β-CD) and chiral cationic ionic liquid (IL), N-undecenoxy-carbonyl-L-leucinol bromide (L-UCLB), which formed micelles in aqueous buffers. Enantioseparations of these PROF drugs were optimized by varying the chain length and concentration of the IL surfactant using a standard recipe containing 35 mM TM-β-CD, 5 mM sodium acetate at pH 5.0. The batch-to-batch reproducibility of L-UCLB was tested and found to have no significant impact in terms of enantiomeric resolution, efficiency and migration time. Finally, this method was successfully applied for the quantitative determination of ibuprofen in pharmaceutical tablets. PMID:19650046

Mechanisms for the inversion of chirality: Global reaction route mapping of stereochemical pathways in a probable chiral extraterrestrial molecule, 2-aminopropionitrile

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

Kaur, Ramanpreet; Vikas, E-mail: qlabspu@pu.ac.in, E-mail: qlabspu@yahoo.com

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 themore » 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.« less

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.

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.

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 liquid phase of simple quantum magnets

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

Wang, Zhentao; Feiguin, Adrian E.; Zhu, Wei

2017-11-07

We study a T=0 quantum phase transition between a quantum paramagnetic state and a magnetically ordered state for a spin S=1 XXZ Heisenberg antiferromagnet on a two-dimensional triangular lattice. The transition is induced by an easy-plane single-ion anisotropy D. At the mean-field level, the system undergoes a direct transition at a critical D=D c between a paramagnetic state at D>D c and an ordered state with broken U(1) symmetry at Dc. We show that beyond mean field the phase diagram is very different and includes an intermediate, partially ordered chiral liquid phase. Specifically, we find that inside the paramagnetic phasemore » the Ising (J z) component of the Heisenberg exchange binds magnons into a two-particle bound state with zero total momentum and spin. This bound state condenses at D>D c, before single-particle excitations become unstable, and gives rise to a chiral liquid phase, which spontaneously breaks spatial inversion symmetry, but leaves the spin-rotational U(1) and time-reversal symmetries intact. This chiral liquid phase is characterized by a finite vector chirality without long-range dipolar magnetic order. In our analytical treatment, the chiral phase appears for arbitrarily small J z because the magnon-magnon attraction becomes singular near the single-magnon condensation transition. This phase exists in a finite range of D and transforms into the magnetically ordered state at some Dc. In conclusion, we corroborate our analytic treatment with numerical density matrix renormalization group calculations.« less

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.

Attosecond-resolved photoionization of chiral molecules.

PubMed

Beaulieu, S; Comby, A; Clergerie, A; Caillat, J; Descamps, D; Dudovich, N; Fabre, B; Géneaux, R; Légaré, F; Petit, S; Pons, B; Porat, G; Ruchon, T; Taïeb, R; Blanchet, V; Mairesse, Y

2017-12-08

Chiral light-matter interactions have been investigated for two centuries, leading to the discovery of many chiroptical processes used for discrimination of enantiomers. Whereas most chiroptical effects result from a response of bound electrons, photoionization can produce much stronger chiral signals that manifest as asymmetries in the angular distribution of the photoelectrons along the light-propagation axis. We implemented self-referenced attosecond photoelectron interferometry to measure the temporal profile of the forward and backward electron wave packets emitted upon photoionization of camphor by circularly polarized laser pulses. We measured a delay between electrons ejected forward and backward, which depends on the ejection angle and reaches 24 attoseconds. The asymmetric temporal shape of electron wave packets emitted through an autoionizing state further reveals the chiral character of strongly correlated electronic dynamics. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Spontaneous chiral symmetry breaking in metamaterials

NASA Astrophysics Data System (ADS)

Liu, Mingkai; Powell, David A.; Shadrivov, Ilya V.; Lapine, Mikhail; Kivshar, Yuri S.

2014-07-01

Spontaneous chiral symmetry breaking underpins a variety of areas such as subatomic physics and biochemistry, and leads to an impressive range of fundamental phenomena. Here we show that this prominent effect is now available in artificial electromagnetic systems, enabled by the advent of magnetoelastic metamaterials where a mechanical degree of freedom leads to a rich variety of strong nonlinear effects such as bistability and self-oscillations. We report spontaneous symmetry breaking in torsional chiral magnetoelastic structures where two or more meta-molecules with opposite handedness are electromagnetically coupled, modifying the system stability. Importantly, we show that chiral symmetry breaking can be found in the stationary response of the system, and the effect is successfully demonstrated in a microwave pump-probe experiment. Such symmetry breaking can lead to a giant nonlinear polarization change, energy localization and mode splitting, which provides a new possibility for creating an artificial phase transition in metamaterials, analogous to that in ferrimagnetic domains.

Spontaneous chiral symmetry breaking in metamaterials.

PubMed

Liu, Mingkai; Powell, David A; Shadrivov, Ilya V; Lapine, Mikhail; Kivshar, Yuri S

2014-07-18

Spontaneous chiral symmetry breaking underpins a variety of areas such as subatomic physics and biochemistry, and leads to an impressive range of fundamental phenomena. Here we show that this prominent effect is now available in artificial electromagnetic systems, enabled by the advent of magnetoelastic metamaterials where a mechanical degree of freedom leads to a rich variety of strong nonlinear effects such as bistability and self-oscillations. We report spontaneous symmetry breaking in torsional chiral magnetoelastic structures where two or more meta-molecules with opposite handedness are electromagnetically coupled, modifying the system stability. Importantly, we show that chiral symmetry breaking can be found in the stationary response of the system, and the effect is successfully demonstrated in a microwave pump-probe experiment. Such symmetry breaking can lead to a giant nonlinear polarization change, energy localization and mode splitting, which provides a new possibility for creating an artificial phase transition in metamaterials, analogous to that in ferrimagnetic domains.

Chiral behavior of K →π l ν decay form factors in lattice QCD with exact chiral symmetry

NASA Astrophysics Data System (ADS)

Aoki, S.; Cossu, G.; Feng, X.; Fukaya, H.; Hashimoto, S.; Kaneko, T.; Noaki, J.; Onogi, T.; Jlqcd Collaboration

2017-08-01

We calculate the form factors of the K →π l ν semileptonic decays in three-flavor lattice QCD and study their chiral behavior as a function of the momentum transfer and the Nambu-Goldstone boson masses. Chiral symmetry is exactly preserved by using the overlap quark action, which enables us to directly compare the lattice data with chiral perturbation theory (ChPT). We generate gauge ensembles at a lattice spacing of 0.11 fm with four pion masses covering 290-540 MeV and a strange quark mass ms close to its physical value. By using the all-to-all quark propagator, we calculate the vector and scalar form factors with high precision. Their dependence on ms and the momentum transfer is studied by using the reweighting technique and the twisted boundary conditions for the quark fields. We compare the results for the semileptonic form factors with ChPT at next-to-next-to-leading order in detail. While many low-energy constants appear at this order, we make use of our data of the light meson electromagnetic form factors in order to control the chiral extrapolation. We determine the normalization of the form factors as f+(0 )=0.9636 (36 )(-35+57) and observe reasonable agreement of their shape with experiment.

Analysis of Chiral Carboxylic Acids in Meteorites

NASA Technical Reports Server (NTRS)

Burton, A. S.; Elsila, J. E.; Hein, J. E.; Aponte, J. C.; Parker, E. T.; Glavin, D. P.; Dworkin, J. P.

2015-01-01

Homochirality of amino acids in proteins and sugars in DNA and RNA is a critical feature of life on Earth. In the absence of a chiral driving force, however, reactions leading to the synthesis of amino acids and sugars result in racemic mixtures. It is currently unknown whether homochirality was necessary for the origins of life or if it was a product of early life. The observation of enantiomeric excesses of certain amino acids of extraterrestrial origins in meteorites provides evidence to support the hypothesis that there was a mechanism for the preferential synthesis or destruction of a particular amino acid enantiomer [e.g., 1-3]. The cause of the observed chiral excesses is un-clear, although at least in the case of the amino acid isovaline, the degree of aqueous alteration that occurred on the meteorite parent body is correlated to the isovaline L-enantiomeric excess [3, 4]. This suggests that chiral symmetry is broken and/or amplified within the meteorite parent bodies. Besides amino acids, there have been only a few reports of other meteoritic compounds found in enantiomeric excess: sugars and sugar acids [5, 6] and the hydroxy acid lactic acid [7]. Determining whether or not additional types of molecules in meteorites are also present in enantiomeric excesses of extraterrestrial information will provide insights into mechanisms for breaking chiral symmetry. Though the previous measurements (e.g., enantiomeric composition of lactic acid [7], and chiral carboxylic acids [8]) were made by gas chromatography-mass spectrometry, the potential for increased sensitivity of liquid chromatography-mass spectrometry (LC-MS) analyses is important because for many meteorite samples, only small sample masses are available for study. Furthermore, at least in the case of amino acids, many of the largest amino acid enantiomeric excesses were observed in samples that contained lower abundances (tens of ppb) of a given amino acid enantiomer. In the present work, we describe

Methods of analysis and separation of chiral flavonoids.

PubMed

Yáñez, Jaime A; Andrews, Preston K; Davies, Neal M

2007-04-01

Although the analysis of the enantiomers and epimers of chiral flavanones has been carried out for over 20 years, there often remains a deficit within the pharmaceutical, agricultural, and medical sciences to address this issue. Hence, despite increased interest in the potential therapeutic uses, plant physiology roles, and health-benefits of chiral flavanones, the importance of stereoselectivity in agricultural, nutrition, pharmacokinetic, pharmacodynamic, pharmacological activity and disposition has often been ignored. This review presents both the general principles that allow separation of chiral flavanones, and discusses both the advantages and disadvantages of the available chromatographic assay methods and procedures used to separately quantify flavanone enantiomers and epimers in biological matrices.

Birefringence in a chiral medium, via temporal cloaking

NASA Astrophysics Data System (ADS)

Khan, Humayun; Haneef, Muhammad

2017-05-01

This paper reports theoretical investigation of birefringence in a chiral medium for the creation of temporal cloaking. The chiral medium splits the input probe beam into left/right circular polarized beams. These left/right circular polarized beams are then controlled and modified within the chiral medium. The left circular polarized beam delays by 24 ns whereas the right circular polarized beam advances by  -23 ns at a control field of rabbi frequency 6γ . This opens a 47 ns time gap for temporal cloaking to hide information without noise corruption and energy loss. The results have potential applications in communication devices for secure propagation of light pulse.

Chiral Biomarkers in Meteorites

NASA Technical Reports Server (NTRS)

Hoover, Richard B.

2010-01-01

The chirality of organic molecules with the asymmetric location of group radicals was discovered in 1848 by Louis Pasteur during his investigations of the rotation of the plane of polarization of light by crystals of sodium ammonium paratartrate. It is well established that the amino acids in proteins are exclusively Levorotary (L-aminos) and the sugars in DNA and RNA are Dextrorotary (D-sugars). This phenomenon of homochirality of biological polymers is a fundamental property of all life known on Earth. Furthermore, abiotic production mechanisms typically yield recemic mixtures (i.e. equal amounts of the two enantiomers). When amino acids were first detected in carbonaceous meteorites, it was concluded that they were racemates. This conclusion was taken as evidence that they were extraterrestrial and produced by abiologically. Subsequent studies by numerous researchers have revealed that many of the amino acids in carbonaceous meteorites exhibit a significant L-excess. The observed chirality is much greater than that produced by any currently known abiotic processes (e.g. Linearly polarized light from neutron stars; Circularly polarized ultraviolet light from faint stars; optically active quartz powders; inclusion polymerization in clay minerals; Vester-Ulbricht hypothesis of parity violations, etc.). This paper compares the measured chirality detected in the amino acids of carbonaceous meteorites with the effect of these diverse abiotic processes. IT is concluded that the levels observed are inconsistent with post-arrival biological contamination or with any of the currently known abiotic production mechanisms. However, they are consistent with ancient biological processes on the meteorite parent body. This paper will consider these chiral biomarkers in view of the detection of possible microfossils found in the Orgueil and Murchison carbonaceous meteorites. Energy dispersive x-ray spectroscopy (EDS) data obtained on these morphological biomarkers will be

Surface defects and chiral algebras

DOE PAGES

Córdova, Clay; Gaiotto, Davide; Shao, Shu-Heng

2017-05-26

Here, we investigate superconformal surface defects in four-dimensional N = 2 superconformal theories. Each such defect gives rise to a module of the associated chiral algebra and the surface defect Schur index is the character of this module. Various natural chiral algebra operations such as Drinfield-Sokolov reduction and spectral flow can be interpreted as constructions involving four-dimensional surface defects. We compute the index of these defects in the free hypermultiplet theory and Argyres-Douglas theories, using both infrared techniques involving BPS states, as well as renormalization group flows onto Higgs branches. We find perfect agreement with the predicted characters, in eachmore » case.« less

Surface defects and chiral algebras

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

Córdova, Clay; Gaiotto, Davide; Shao, Shu-Heng

Here, we investigate superconformal surface defects in four-dimensional N = 2 superconformal theories. Each such defect gives rise to a module of the associated chiral algebra and the surface defect Schur index is the character of this module. Various natural chiral algebra operations such as Drinfield-Sokolov reduction and spectral flow can be interpreted as constructions involving four-dimensional surface defects. We compute the index of these defects in the free hypermultiplet theory and Argyres-Douglas theories, using both infrared techniques involving BPS states, as well as renormalization group flows onto Higgs branches. We find perfect agreement with the predicted characters, in eachmore » case.« less

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

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.

Utilization of Alternate Chirality Enantiomers in Microbial Communities

NASA Technical Reports Server (NTRS)

Pikuta, Elena V.; Hoover, Richard B.

2010-01-01

Our previous study of chirality led to interesting findings for some anaerobic extremophiles: the ability to metabolize substrates with alternate chirality enantiomers of amino acids and sugars. We have subsequently found that not just separate microbial species or strains but entire microbial communities have this ability. The functional division within a microbial community on proteo- and sugarlytic links was also reflected in a microbial diet with L-sugars and D-amino acids. Several questions are addressed in this paper. Why and when was this feature developed in a microbial world? Was it a secondary de novo adaptation in a bacterial world? Or is this a piece of genetic information that has been left in modern genomes as an atavism? Is it limited exclusively to prokaryotes, or does this ability also occur in eukaryotes? In this article, we have used a broader approach to study this phenomenon using anaerobic extremophilic strains from our laboratory collection. A series of experiments were performed on physiologically different groups of extremophilic anaerobes (pure and enrichment cultures). The following characteristics were studied: 1) the ability to grow on alternate chirality enantiomers -- L-sugars and D- amino acids; 2) Growth-inhibitory effect of alternate chirality enantiomers; 3) Stickland reaction with alternate chirality amino acids. The results of this research are presented in this paper.

Chirality-sensitive microwave spectroscopy - application to terpene molecules

NASA Astrophysics Data System (ADS)

Schnell, Melanie

Most molecules of biochemical relevance are chiral. Even though the physical properties of two enantiomers are nearly identical, they might exhibit completely different biochemical effects, such as different odor in the case of carvone. In nature and as products of chemical syntheses, chiral molecules often exist in mixtures with other chiral molecules. The analysis of these complex mixtures to identify the molecular components, to determine which enantiomers are present, and to measure the enantiomeric excesses (ee) is still one of the challenging and very important tasks of analytical chemistry. We recently experimentally demonstrated a new method of differentiating enantiomeric pairs of chiral molecules in the gas phase. It is based on broadband rotational spectroscopy and is a three-wave mixing process that involves a closed cycle of three rotational transitions. The phase of the acquired signal bares the signature of the enantiomer, as it depends upon the product of the transition dipole moments. Furthermore, because the signal amplitude is proportional to the ee, this technique allows not only for determining which enantiomer is in excess, but also by how much. A unique advantage of our technique is that it can also be applied to mixtures of chiral molecules, even when the molecules are very similar. In my lecture, I will introduce the technique and give an update on the recent developments.

Chiral algebras in Landau-Ginzburg models

NASA Astrophysics Data System (ADS)

Dedushenko, Mykola

2018-03-01

Chiral algebras in the cohomology of the {\\overline{Q}}+ supercharge of two-dimensional N=(0,2) theories on flat spacetime are discussed. Using the supercurrent multiplet, we show that the answer is renormalization group invariant for theories with an R-symmetry. For N=(0,2) Landau-Ginzburg models, the chiral algebra is determined by the operator equations of motion, which preserve their classical form, and quantum renormalization of composite operators. We study these theories and then specialize to the N=(2,2) models and consider some examples.

New mathematic model for predicting chiral separation using molecular docking: mechanism of chiral recognition of triadimenol analogues.

PubMed

Zhang, Guoqing; Sun, Qingyan; Hou, Ying; Hong, Zhanying; Zhang, Jun; Zhao, Liang; Zhang, Hai; Chai, Yifeng

2009-07-01

The purpose of this paper was to study the enantioseparation mechanism of triadimenol compounds by carboxymethylated (CM)-beta-CD mediated CE. All the enantiomers were separated under the same experimental conditions to study the chiral recognition mechanism using a 30 mM sodium dihydrogen phosphate buffer at pH 2.2 adjusted by phosphoric acid. The inclusion courses between CM-beta-CD and enantiomers were investigated by the means of molecular docking technique. It was found that there were at least three points (one hydrophobic bond and two hydrogen bonds) involved in the interaction of each enantiomer with the chiral selectors. A new mathematic model has been built up based on the results of molecular mechanics calculations, which could analyze the relationship between the resolution of enantioseparation and the interaction energy in the docking area. Comparing the results of the separation by CE, the established mathematic model demonstrated good capability to predict chiral separation of triadimenol enantiomers using CM-beta-CD mediated CE.

Resonance Raman Spectroscopy of Chirality Enriched Semiconducting Carbon Nanotubes

NASA Astrophysics Data System (ADS)

Hight Walker, A. R.; Piao, Y.; Simpson, J. R.; Lindsay, M.; Streit, J. K.; Ao, G.; Zheng, M.; Fagan, J. A.

Relative intensities of resonant Raman RBM and G modes of 11 chirality-enriched SWCNT species were established under second-order excitation. Results demonstrate an under-recognized complexity in evaluation of Raman spectra for assignment of (n,m) population distributions. Strong chiral angle and mod dependencies affect the intensity ratio of RBM/G modes and can result in misleading interpretations. We report 5 new (n,m) values for chirality-dependent G+ and G- Raman peak positions and intensity ratios, extending the available data to cover smaller diameters down to (5,4). The Raman spectral library sufficiently decouples G peaks from multiple species and enables fundamental characterization in mixed chirality samples. Our results on dispersive properties of the D modes will also be discussed. Probing defects is crucial to evaluate SWCNT quality and to understand the photophysics behind defect-induced optoelectronic features. Using high-quality, chirality-enriched semiconducting SWCNTs and tunable lasers, our results show a non-dispersive D band throughout the resonant window within the same (n,m). Our results were validated by multiple (n,m) samples and intentional covalent surface functionalization generating D peaks with increased intensity, which remain non-dispersive.

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.

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.

Monte Carlo simulations of nematic and chiral nematic shells

NASA Astrophysics Data System (ADS)

Wand, Charlie R.; Bates, Martin A.

2015-01-01

We present a systematic Monte Carlo simulation study of thin nematic and cholesteric shells with planar anchoring using an off-lattice model. The results obtained using the simple model correspond with previously published results for lattice-based systems, with the number, type, and position of defects observed dependent on the shell thickness with four half-strength defects in a tetrahedral arrangement found in very thin shells and a pair of defects in a bipolar (boojum) configuration observed in thicker shells. A third intermediate defect configuration is occasionally observed for intermediate thickness shells, which is stabilized in noncentrosymmetric shells of nonuniform thickness. Chiral nematic (cholesteric) shells are investigated by including a chiral term in the potential. Decreasing the pitch of the chiral nematic leads to a twisted bipolar (chiral boojum) configuration with the director twist increasing from the inner to the outer surface.

Implications of the causality principle for ultra chiral metamaterials

PubMed Central

Gorkunov, Maxim V.; Dmitrienko, Vladimir E.; Ezhov, Alexander A.; Artemov, Vladimir V.; Rogov, Oleg Y.

2015-01-01

Chiral metamaterials – artificial subwavelength structures with broken mirror symmetry – demonstrate outstanding degree of optical chirality that exhibits sophisticated spectral behavior and can eventually reach extreme values. Based on the fundamental causality principle we show how one can unambiguously relate the metamaterial circular dichroism and optical activity by the generalized Kramers-Kronig relations. Contrary to the conventional relations, the generalized ones provide a unique opportunity of extracting information on material-dependent zeroes of transmission coefficient in the upper half plane of complex frequency. We illustrate the merit of the formulated relations by applying them to the observed ultra chiral optical transmission spectra of subwavelength arrays of chiral holes in silver films. Apart from the possibility of precise verification of experimental data, the relations enable resolving complex eigenfrequencies of metamaterial intrinsic modes and resonances. PMID:25787007

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

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

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.

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.

Three-Step Synthesis of Chiral Spirocyclic Oxaphospholenes.

PubMed

Berton, Jan K E T; Salemi, Hadi; Pirat, Jean-Luc; Virieux, David; Stevens, Christian V

2017-12-01

Chiral spirocylic oxaphospholenes were prepared in a three-step sequence from chiral pool terpenoid ketones. After addition of a metal acetylide, the resulting propargyl alcohols were converted stereoselectively into their allenylphosphonate counterparts. In the last step, they were conveniently cyclized into spirooxaphospholenes with one equivalent of iodine without purification. When starting from sterically hindered terpenes, allenylphosphonates were also easily obtained but showed to be unreactive or rearranged under these cyclization conditions.

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.

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.

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.

Chiral separation and twin-beam photonics