WorldWideScience

Sample records for chiral molecules

  1. On Chiral Space Groups and Chiral Molecules

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    This note explains the relationship (as well as the absence of a relationship) between chiral space groups and chiral molecules (which have absolute configurations). For a chiral molecule, which must crystallize in a chiral space group, the outcome of the absolute configuration determination must be linked to some other properties of the chiral crystal such as its optical activity for the observation to the relevant.

  2. On Chiral Space Groups and Chiral Molecules

    Institute of Scientific and Technical Information of China (English)

    NgSeikWng; HUSheng-Zhi

    2003-01-01

    This note explains the relationship (as well as the absence of a relationship) between chiral space groups and chiral molecules (which have absolute configurations).For a chiral molecule,which must crystallize in a chiral space group,the outcome of the absolute configuration determination must be linked to some other properties of the chiral crystal such as its optical activity for the observation to the relevant.

  3. Chiral Molecules Revisited by Broadband Microwave Spectroscopy

    Science.gov (United States)

    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

  4. Chiral Sensitivity in Electron-Molecule Interactions

    Science.gov (United States)

    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.

  5. Circular Intensity Differential Scattering of chiral molecules

    Energy Technology Data Exchange (ETDEWEB)

    Bustamante, C.J.

    1980-12-01

    In this thesis a theory of the Circular Intensity Differential Scattering (CIDS) of chiral molecules as modelled by a helix oriented with respect to the direction of incidence of light is presented. It is shown that a necessary condition for the existence of CIDS is the presence of an asymmetric polarizability in the scatterer. The polarizability of the scatterer is assumed generally complex, so that both refractive and absorptive phenomena are taken into account.

  6. Enantiomer-Specific State Transfer of Chiral Molecules

    CERN Document Server

    Eibenberger, Sandra; Patterson, David

    2016-01-01

    State-selective enantiomeric excess is realized using microwave-driven coherent population transfer. The method selectively promotes either R- or S- molecules to a higher rotational state by phase-controlled microwave pulses that drive electric-dipole allowed rotational transitions. We demonstrate the method using a racemic mixture of 1,2-propanediol. This method of chiral enrichment can be applied to nearly any chiral molecule that can be vaporized and cooled to the point where rotationally resolved spectroscopy is possible, including molecules that rapidly racemize. The rapid chiral switching demonstrated here allows for new applications in high-precision spectroscopic searches for parity violation in chiral molecules.

  7. Supramolecular helices: chirality transfer from conjugated molecules to structures.

    Science.gov (United States)

    Yang, Yang; Zhang, Yajie; Wei, Zhixiang

    2013-11-13

    Different scales of chirality endow a material with many excellent properties and potential applications. In this review, using π-conjugated molecules as functional building blocks, recent progress on supramolecular helices inspired by biological helicity is summarized. First, induced chirality on conjugated polymers and small molecules is introduced. Molecular chirality can be amplified to nanostructures, superstructures, and even macroscopic structures by a self-assembly process. Then, the principles for tuning the helicity of supramolecular chirality, as well as formation of helical heterojunctions, are summarized. Finally, the potential applications of chiral structures in chiral sensing and organic electronic devices are critically reviewed. Due to recent progress in chiral structures, an interdisciplinary area called "chiral electronics" is expected to gain wide popularity in the near future.

  8. First molecules, biological chirality, origin(s) of life.

    Science.gov (United States)

    Caglioti, Luciano; Micskei, Károly; Pályi, Gyula

    2011-01-01

    Origin(s) of biological chirality appear(s) to be intimately connected to origin(s) of life. Prebiotic evolution toward these important turning points can be traced back to single chiral molecules. These can be small (monomeric) units as amino acids or monosaccharides or oligomers as oligo-RNA type molecules. Earlier speculations about these two kinds of entries to biological chirality are critically reviewed.

  9. Detecting chirality in molecules by linearly polarized laser fields

    CERN Document Server

    Yachmenev, Andrey

    2016-01-01

    A new scheme for enantiomer differentiation of chiral molecules using a pair of linearly polarized intense ultrashort laser pulses with skewed mutual polarization is presented. The technique relies on the fact that the off-diagonal anisotropic contributions to the electric polarizability tensor for two enantiomers have different signs. Exploiting this property, we are able to excite a coherent unidirectional rotation of two enantiomers with a {\\pi} phase difference in the molecular electric dipole moment. The approach is robust and suitable for relatively high temperatures of molecular samples, making it applicable for selective chiral analysis of mixtures, and to chiral molecules with low barriers between enantiomers. As an illustration, we present nanosecond laser-driven dynamics of a tetratomic non-rigid chiral molecule with short-lived chirality. The ultrafast time scale of the proposed technique is well suited to study parity violation in molecular systems in short-lived chiral states.

  10. Atom-Specific Identification of Adsorbed Chiral Molecules by Photoemission

    Science.gov (United States)

    Kim, J. W.; Carbone, M.; Dil, J. H.; Tallarida, M.; Flammini, R.; Casaletto, M. P.; Horn, K.; Piancastelli, M. N.

    2005-09-01

    The study of chiral adsorbed molecules is important for an analysis of enantioselectivity in heterogeneous catalysis. Here we show that such molecules can be identified through circular dichroism in core-level photoemission arising from the chiral carbon atoms in stereoisomers of 2,3-butanediol molecules adsorbed on Si(100), using circularly polarized x rays. The asymmetry in the carbon 1s intensity excited by right and left circularly polarized light is readily observed, and changes sign with the helicity of the radiation or handedness of the enantiomers; it is absent in the achiral form of the molecule. This observation demonstrates the possibility of determining molecular chirality in the adsorbed phase.

  11. Chiral Sensitivity in the Dissociative Electron Attachment of Halocamphor Molecules

    Science.gov (United States)

    Dreiling, Joan

    2016-05-01

    We have demonstrated chirally-dependent molecular destruction when incident longitudinally-spin-polarized (chiral) electrons break bonds in chiral molecules. This chiral sensitivity was observed through an asymmetry in the dissociative electron attachment (DEA) reaction rate with chiral 3-bromocamphor (C10 H15 BrO). Such an observation provides an unambiguous demonstration of the idea underlying the Vester-Ulbricht hypothesis, which attempts to explain the origins of the homochirality that is observed in many biological systems. While the lack of inversion symmetry in these reactions allows the effects we observe to occur, their dynamic causes are poorly understood. We have further studied the asymmetries in the DEA rates for two additional halocamphor molecules, 3-iodocamphor (C10 H15 IO) and 10-iodocamphor, in a systematic effort to illuminate the mechanisms responsible for the chiral sensitivity. The DEA signal depends on the sign of the incident electron helicity for a given target handedness in all molecules, and it varies with both the atomic number and the location of the heaviest atom in the molecule. Surprisingly, the DEA asymmetries for 10-iodocamphor, in which the heaviest atom is farther from a chiral center than for the other molecules, produced the largest asymmetries. This work was performed at the University of Nebraska-Lincoln. This project was funded by NSF Grant PHY-1206067.

  12. Spintronics and chirality: spin selectivity in electron transport through chiral molecules.

    Science.gov (United States)

    Naaman, Ron; Waldeck, David H

    2015-04-01

    Recent experiments have demonstrated that the electron transmission yield through chiral molecules depends on the electron spin orientation. This phenomenon has been termed the chiral-induced spin selectivity (CISS) effect, and it provides a challenge to theory and promise for organic molecule-based spintronic devices. This article reviews recent developments in our understanding of CISS. Different theoretical models have been used to describe the effect; however, they all presume an unusually large spin-orbit coupling in chiral molecules for the effect to display the magnitudes seen in experiments. A simplified model for an electron's transport through a chiral potential suggests that these large couplings can be manifested. Techniques for measuring spin-selective electron transport through molecules are overviewed, and some examples of recent experiments are described. Finally, we present results obtained by studying several systems, and we describe the possible application of the CISS effect for memory devices.

  13. Development of safer molecules through chirality

    Directory of Open Access Journals (Sweden)

    Patil P

    2006-10-01

    Full Text Available Many of the drugs currently used in medical practice are mixtures of enantiomers (racemates. Many a times, the two enantiomers differ in their pharmacokinetic and pharmacodynamic properties. Replacing existing racemates with single isomers has resulted in improved safety and/or efficacy profile of various racemates. In this review, pharmacokinetic and pharmacodynamic implications of chirality are discussed in brief, followed by an overview of some important chiral switches that have yielded safer alternatives. These include levosalbutamol, S-ketamine, levobupivacaine, S-zopiclone, levocetirizine, S-amlodipine, S-atenolol, S-metoprolol, S-omeprazole, S-pantoprazole and R-ondansetron. Few potential chiral switches under evaluation and some chiral switches that have not been successful are also discussed.

  14. Development of safer molecules through chirality

    OpenAIRE

    Patil P; Kothekar M

    2006-01-01

    Many of the drugs currently used in medical practice are mixtures of enantiomers (racemates). Many a times, the two enantiomers differ in their pharmacokinetic and pharmacodynamic properties. Replacing existing racemates with single isomers has resulted in improved safety and/or efficacy profile of various racemates. In this review, pharmacokinetic and pharmacodynamic implications of chirality are discussed in brief, followed by an overview of some important chiral switches that have yielded ...

  15. Chiral switching by spontaneous conformational change in adsorbed organic molecules.

    Science.gov (United States)

    Weigelt, Sigrid; Busse, Carsten; Petersen, Lars; Rauls, Eva; Hammer, Bjørk; Gothelf, Kurt V; Besenbacher, Flemming; Linderoth, Trolle R

    2006-02-01

    Self-assembly of adsorbed organic molecules is a promising route towards functional surface nano-architectures, and our understanding of associated dynamic processes has been significantly advanced by several scanning tunnelling microscopy (STM) investigations. Intramolecular degrees of freedom are widely accepted to influence ordering of complex adsorbates, but although molecular conformation has been identified and even manipulated by STM, the detailed dynamics of spontaneous conformational change in adsorbed molecules has hitherto not been addressed. Molecular surface structures often show important stereochemical effects as, aside from truly chiral molecules, a large class of so-called prochiral molecules become chiral once confined on a surface with an associated loss of symmetry. Here, we investigate a model system in which adsorbed molecules surprisingly switch between enantiomeric forms as they undergo thermally induced conformational changes. The associated kinetic parameters are quantified from time-resolved STM data whereas mechanistic insight is obtained from theoretical modelling. The chiral switching is demonstrated to enable an efficient channel towards formation of extended homochiral surface domains. Our results imply that appropriate prochiral molecules may be induced (for example, by seeding) to assume only one enantiomeric form in surface assemblies, which is of relevance for chiral amplification and asymmetric heterogenous catalysis.

  16. Discovery of the First Interstellar Chiral Molecule: Propylene Oxide

    Science.gov (United States)

    Carroll, Brandon; McGuire, Brett A.; Loomis, Ryan; Finneran, Ian A.; Jewell, Philip; Remijan, Anthony; Blake, Geoffrey

    2016-06-01

    Life on Earth relies on chiral molecules, that is, species not superimposable on their mirror images. This manifests itself as a reliance on a single molecular handedness, or homochirality that is characteristic of life and perhaps most readily apparent in the large enhancement in biological activity of particular amino acid and sugar enantiomers. Yet, the ancestral origin of biological homochirality remains a mystery. The non-racemic ratios in some organics isolated from primitive meteorites hint at a primordial chiral seed but even these samples have experienced substantial processing during planetary assembly, obscuring their complete histories. To determine the underlying origin of any enantiomeric excess, it is critical to understand the molecular gas from which these molecules originated. Here, we present the first extra-solar, astronomical detection of a chiral molecule, propylene oxide (CH_3CHCH_2O), in absorption toward the Galactic Center. With the detection of propylene oxide, we at last have a target for broad-ranging searches for the possible cosmic origin of the homochirality of life.

  17. Stereochemical configuration and selective excitation of the chiral molecule halothane

    CERN Document Server

    Pitzer, Martin; Burzynski, Phillip; Weller, Miriam; Metz, Daniel; Neff, Jonathan; Waitz, Markus; Trinter, Florian; Schmidt, Lothar Ph H; Williams, Joshua B; Jahnke, Till; Schmidt-Böcking, Horst; Berger, Robert; Dörner, Reinhard; Schöffler, Markus

    2016-01-01

    X-ray single-photon ionization and fragmentation of the chiral molecule halothane (CHBrClCF${}_{3}$) from a racemic mixture have been investigated using the COLTRIMS (Cold Target Recoil Ion Momentum Spectroscopy) technique. Two important facets related to the core ionization of this species are examined: Firstly, the distinction of enantiomers (mirror isomers) and the determination of absolute configuration on a single-molecule level by four-body Coulomb explosion; secondly, the interplay of site-selective excitation and fragmentation patterns. These results are easily transferrable to other molecular species and show the wealth of features

  18. Optical Rectification in Isotropic Thin Film Composed of Chiral Molecules with a Tripod-Like Structure

    Institute of Scientific and Technical Information of China (English)

    WANG Xiao-Ou; GONG Li-Jing; LI Chun-Fei

    2008-01-01

    @@ Optical rectification (OR) effect in the isotropic thin film consisting of chiral molecules with a tripod-like structure is investigated.The expressions of static-electric polarization in the isotropic chiral thin films and the relations between the OR and microscopic parameters of chiral medium are obtaineel by theoretical derivation,Furthermore,the relations of static electric polarization with the wavelength of incident light and parameters of chiral molecules are simulated numerically.

  19. Engineering of radiation of optically active molecules with chiral nano-meta-particles

    CERN Document Server

    Klimov, Vasily V; Ducloy, Martial

    2011-01-01

    The radiation of optically active (chiral) molecule placed near chiral nanoparticle is investigated. The optimal conditions for engineering of radiation of optically active (chiral) molecules with the help of chiral nanoparticles are derived. It is shown that for this purpose, the substance of the chiral particle must have both \\epsilon_and \\mu_negative (double negative material (DNG)) or negative \\mu_and positive \\epsilon_(\\mu_negative material (MNG)). Our results pave the way to an effective engineering of radiation of "left" and "right" molecules and to creating pure optical devices for separation of drugs enantiomers.

  20. Engineering of radiation of optically active molecules with chiral nano-meta-particles

    Science.gov (United States)

    Klimov, V. V.; Guzatov, D. V.; Ducloy, M.

    2012-02-01

    The radiation of an optically active (chiral) molecule placed near a chiral nanosphere is investigated. The optimal conditions for engineering of radiation of optically active (chiral) molecules with the help of chiral nanoparticles are derived. It is shown that for this purpose, the substance of the chiral particle must have both ɛ and μ negative (double negative material (DNG)) or negative μ and positive ɛ (μ negative material (MNG)). Our results pave the way to an effective engineering of radiation of "left" and "right" molecules and to creating pure optical devices for separation of drugs enantiomers.

  1. Parity violation tests in chiral molecules by laser spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Chardonnet, Ch.; Daussy, Ch.; Marrel, T.; Amy-Klein, A.; Nguyen, C.T.; Borde, Ch.J. [Paris-13 Univ., 93 - Villetaneuse (France). Lab. de Physique des Lasers

    1999-07-01

    A laser nonlinear spectroscopy experiment has been designed and implemented to test the conjecture that enantiomers of chiral molecules may have different spectra because of the parity violation associated with neutral currents in the weak interaction between electrons and nuclei. We review the theoretical reasons that lead to this prediction and we outline the method currently used to calculate energy and frequency differences between mirror image molecules. Preliminary experimental tests have been conducted on hyperfine components of vibration-rotation transitions of CHFClBr in the 9.3 {mu}m spectral range. The frequencies of saturation resonances of separated enantiomers have been compared and found identical within 13 Hz ({delta}{nu}/{nu} <4.10{sup -13}). (authors)

  2. Can circular dichroism in core-level photoemission provide a spectral fingerprint of adsorbed chiral molecules?

    Energy Technology Data Exchange (ETDEWEB)

    Allegretti, F [Physics Department, University of Warwick, Coventry CV4 7AL (United Kingdom); Polcik, M [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D 14195 Berlin (Germany); Sayago, D I [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D 14195 Berlin (Germany); Demirors, F [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D 14195 Berlin (Germany); O' Brien, S [Physics Department, University of Warwick, Coventry CV4 7AL (United Kingdom); Nisbet, G [Centre for Applied Catalysis, Department of Chemical and Biological Sciences, University of Huddersfield, Queensgate, Huddersfield HD1 3DH (United Kingdom); Lamont, C L A [Centre for Applied Catalysis, Department of Chemical and Biological Sciences, University of Huddersfield, Queensgate, Huddersfield HD1 3DH (United Kingdom); Woodruff, D P [Physics Department, University of Warwick, Coventry CV4 7AL (United Kingdom)

    2005-04-01

    The results of experimental measurements and theoretical simulations of circular dichroism in the angular distribution (CDAD) of photoemission from atomic core levels of each of the enantiomers of a chiral molecule, alanine, adsorbed on Cu(1 1 0) are presented. Measurements in, and out of, substrate mirror planes allow one to distinguish the CDAD due to the chirality of the sample from that due to a chiral experimental geometry. For these studies of oriented chiral molecules, the CDAD is seen not only in photoemission from the molecular chiral centre, but also from other atoms which have chiral geometries as a result of the adsorption. The magnitude of the CDAD due to the sample chirality differs for different adsorption phases of alanine, and for different emission angles and energies, but is generally small compared with CDAD out of the substrate mirror planes which is largely unrelated to the molecular chirality. While similar measurements of other molecules may reveal larger CDAD due to molecular chirality, the fact that the results for one chiral molecule show weak effects means that such CDAD is unlikely to provide a simple and routine general spectral fingerprint of adsorbed molecular chirality.

  3. Hyperpolarizabilities of Chiral Molecules Based on Three-Coupled-Oscillator Model

    Institute of Scientific and Technical Information of China (English)

    WANG Xiao-Ou; LI Jun-Qing; LI Chun-Fei

    2004-01-01

    @@ A chiral molecular model of three coupled oscillators is established. A set of coupling equations and hyperpolarizabilities for the chiral molecules with the tripod structure are presented. The expression of second-order nonlinear susceptibility is derived for an isotropic molecular system. The calculated hyperpolarizabilities of NPAN and NPP chiral molecules are consistent with the experimental results and the applicability of this model is validated.

  4. Stereoselective Modulation of P-Glycoprotein by Chiral Small Molecules.

    Science.gov (United States)

    Carocci, Alessia; Catalano, Alessia; Turi, Francesco; Lovece, Angelo; Cavalluzzi, Maria M; Bruno, Claudio; Colabufo, Nicola A; Contino, Marialessandra; Perrone, Maria G; Franchini, Carlo; Lentini, Giovanni

    2016-01-01

    Inhibition of drug efflux pumps such as P-glycoprotein (P-gp) is an approach toward combating multidrug resistance, which is a significant hurdle in current cancer treatments. To address this, N-substituted aryloxymethyl pyrrolidines were designed and synthesized in their homochiral forms in order to investigate the stereochemical requirements for the binding site of P-gp. Our study provides evidence that the chiral property of molecules could be a strategy for improving the capacity for interacting with P-gp, as the most active compounds of the series stereoselectively modulated this efflux pump. The naphthalene-1-yl analogue (R)-2-[(2,3-dichlorophenoxy)methyl]-1-(naphthalen-1-ylmethyl)pyrrolidine) [(R)-7 a] emerged foremost for its potency and stereoselectivity toward P-gp, with the S enantiomer being nearly inactive. The modulation of P-gp by (R)-7 a involved consumption of ATP, thus demonstrating that the compound behaves as a P-gp substrate.

  5. Structural characterization of chiral molecules using vibrational circular dichroism spectroscopy

    DEFF Research Database (Denmark)

    Lassen, Peter Rygaard

    2006-01-01

    compounds of pharmaceutical interest. Others are transition metal complexes relevant for the search for parity-violation effects in vibrational spectroscopy (rhenium complexes), for asymmetric catalysis (Schiff-base complexes), or as model systems for metal centres in biology (Schiff-bases and heme....... Currently, only part of the enhancement can be reproduced theoretically, as demonstrated for the Schiff-bases. Their conformers and absolute configurations were also identified. As for proteins, the interpretation of their spectra is different, because the immense number of overlapping vibrational modes...... chiral molecules. This project is about application of one such technique, circular dichroism (CD) spectroscopy, which measures the difference in absorption of left- and right circularly polarized light - hence the name circular dichroism. This study has focused on the infrared (IR) range because...

  6. Discovery of the Interstellar Chiral Molecule Propylene Oxide (CH$_3$CHCH$_2$O)

    CERN Document Server

    McGuire, Brett A; Loomis, Ryan A; Finneran, Ian A; Jewell, Philip R; Remijan, Anthony J; Blake, Geoffrey A

    2016-01-01

    Life on Earth relies on chiral molecules, that is, species not superimposable on their mirror images. This manifests itself in the selection of a single molecular handedness, or homochirality, across the biosphere. We present the astronomical detection of a chiral molecule, propylene oxide (CH$_3$CHCH$_2$O), in absorption toward the Galactic Center. Propylene oxide is detected in the gas phase in a cold, extended molecular shell around the embedded, massive protostellar clusters in the Sagittarius B2 star-forming region. This material is representative of the earliest stage of solar system evolution in which a chiral molecule has been found.

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

    Science.gov (United States)

    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.

  8. Transfer of chirality from adsorbed chiral molecules to the substrates highlighted by circular dichroism in angle-resolved valence photoelectron spectroscopy

    DEFF Research Database (Denmark)

    Contini, G.; Turchini, S.; Sanna, Simone

    2012-01-01

    Studies of self-assembled chiral molecules on achiral metallic surfaces have mostly focused on the determination of the geometry of adsorbates and their electronic structure. The aim of this paper is to provide direct information on the chirality character of the system and on the chirality trans...

  9. High resolution spectroscopy of methyltrioxorhenium: towards the observation of parity violation in chiral molecules

    CERN Document Server

    Stoeffler, Clara; Shelkovnikov, Alexander; Daussy, Christophe; Amy-Klein, Anne; Chardonnet, Christian; Guy, Laure; Crassous, Jeanne; Huet, Thérèse; Soulard, Pascale; Asselin, Pierre

    2010-01-01

    Originating from the weak interaction, parity violation in chiral molecules has been considered as a possible origin of the biohomochirality. It was predicted in 1974 but has never been observed so far. Parity violation should lead to a very tiny frequency difference in the rovibrational spectra of the enantiomers of a chiral molecule. We have proposed to observe this predicted frequency difference using the two photon Ramsey fringes technique on a supersonic beam. Promising candidates for this experiment are chiral oxorhenium complexes, which present a large effect, can be synthesized in large quantity and enantiopure form, and can be seeded in a molecular beam. As a first step towards our objective, a detailed spectroscopic study of methyltrioxorhenium (MTO) has been undertaken. It is an ideal test molecule as the achiral parent molecule of chiral candidates for the parity violation experiment. For the 187Re MTO isotopologue, a combined analysis of Fourier transform microwave and infrared spectra as well as...

  10. Condensations of single DNA molecules induced by heptaplatin and its chiral isomer

    Science.gov (United States)

    Zhang, Hong-Yan; Liu, Yu-Ru; Li, Wei; Li, Hui; Dou, Shuo-Xing; Xie, Ping; Wang, Wei-Chi; Wang, Peng-Ye

    2014-08-01

    Heptaplatin is a third-generation platinum antitumor drug. It has a chiral isomer. We studied the interactions between the two isomers and DNA by using magnetic tweezers and atomic force microscopy (AFM) to investigate the effect of chiralities of the isomers on the interactions. We found that the extension curves and average condensation rates of DNA molecules incubated with heptaplatin were nearly the same as those incubated with its chiral isomer. In addition, the structures of DNA molecules incubated with heptaplatin were also similar to those incubated with its chiral isomer. These results indicate the difference in chirality of the two isomers does not induce different interactions of the isomers with DNA. Our study may facilitate the understanding of interactions of platinum complexes with DNA and the design of new antitumor platinum complexes.

  11. Discovery of the interstellar chiral molecule propylene oxide (CH3CHCH2O)

    Science.gov (United States)

    McGuire, Brett A.; Carroll, P. Brandon; Loomis, Ryan A.; Finneran, Ian A.; Jewell, Philip R.; Remijan, Anthony J.; Blake, Geoffrey A.

    2016-06-01

    Life on Earth relies on chiral molecules—that is, species not superimposable on their mirror images. This manifests itself in the selection of a single molecular handedness, or homochirality, across the biosphere. We present the astronomical detection of a chiral molecule, propylene oxide (CH3CHCH2O), in absorption toward the Galactic center. Propylene oxide is detected in the gas phase in a cold, extended molecular shell around the embedded, massive protostellar clusters in the Sagittarius B2 star-forming region. This material is representative of the earliest stage of solar system evolution in which a chiral molecule has been found.

  12. Theory of Microwave 3-WAVE Mixing of Chiral Molecules

    Science.gov (United States)

    Lehmann, Kevin

    2016-06-01

    The traditional spectroscopic methods to measure enantiomeric excess, based upon optical rotation or circular dichroism arise from an interference of electric and magnetic dipole contributions of an optical transitions. The later is relativisitic and gets smaller with decreasing frequency and thus these effects have not been previously observed in pure rotational spectroscopy. First introduced by the group at Harvard^1, it is possible to use a 3-wave mixing method (with one of the fields potentially a Stark Field) to distinguish enantiomers if the three wave are nonplaner. In the conceptually simplest form of this experiment, a molecule is polarized with X polarization on a a → b transition, and then the resulting ρab molecular coherence is transferred to a ρac coherence by application of a π pulse on the b → c transition. For a chiral molecule with nonzero dipole projections on the three inertial axes, this ρac coherence can radiate Z polarized emission at the frequency of the a → c transition. In this talk, I will present the full theory of such experiments, including accounting for dirrection cosine matrix elements and M degeneracy. The resulting expressions can be used to calculate the expected size of the signal as a function of the specific transitions used in the a → b → c → a cycle.^2 It will be demonstrated that the maximum size of the ρac coherence is nearly that generated by a ``π/2'' pulse on the a → c transition. However, it is not possible to phase match the emission generated by this polarization due to the requirement that the three fields be orthogonal. Given that in rotational spectroscopy the physical size of the sample produced in a pulsed supersonic jet is comparable to the wavelengths of the microwave fields, the lack of phase matching produces a substantial but not catastrophic loss in the amplitude of the emitted free induction decay field. I will present a proposal to realize an analogy of quasiphase matching to

  13. Relaxation Dynamics in Photoexcited Chiral Molecules Studied by Time-Resolved Photoelectron Circular Dichroism: Toward Chiral Femtochemistry

    CERN Document Server

    Comby, Antoine; Boggio-Pasqua, Martial; Descamps, Dominique; Légaré, Francois; Nahon, Laurent; Petit, Stéphane; Pons, Bernard; Fabre, Baptiste; Mairesse, Yann; Blanchet, Valérie

    2016-01-01

    Unravelling the main initial dynamics responsible for chiral recognition is a key stepin the understanding of many biological processes. However this challenging task requires a sensitive enantiospecic probe to investigate molecular dynamics on their natural femtosecond timescale. Here we show that, in the gas phase, the ultrafast relaxationdynamics of photoexcited chiral molecules can be tracked by recording Time-ResolvedPhotoElectron Circular Dichroism (TR-PECD) resulting from the photoionisation bya circularly polarized probe pulse. A large forward/backward asymmetry along theprobe propagation axis is observed in the photoelectron angular distribution. Its evolution with pump-probe delay reveals ultrafast dynamics that are inaccessible in theangle-integrated photoelectron spectrum nor via the usual electron emission anisotropyparameter ($\\beta$). PECD, which originates from the electron scattering in the chiral molecular potential, appears as a new sensitive observable for ultrafast molecular dynamicsin ch...

  14. Determination of absolute configuration of chiral molecules using vibrational optical activity: a review.

    Science.gov (United States)

    He, Yanan; Wang, Bo; Dukor, Rina K; Nafie, Laurence A

    2011-07-01

    Determination of the absolute handedness, known as absolute configuration (AC), of chiral molecules is an important step in any field related to chirality, especially in the pharmaceutical industry. Vibrational optical activity (VOA) has become a powerful tool for the determination of the AC of chiral molecules in the solution state after nearly forty years of evolution. VOA offers a novel alternative, or supplement, to X-ray crystallography, permitting AC determinations on neat liquid, oil, and solution samples without the need to grow single crystals of the pure chiral sample molecules as required for X-ray analysis. By comparing the sign and intensity of the measured VOA spectrum with the corresponding ab initio density functional theory (DFT) calculated VOA spectrum of a chosen configuration, one can unambiguously assign the AC of a chiral molecule. Comparing measured VOA spectra with calculated VOA spectra of all the conformers can also provide solution-state conformational populations. VOA consists of infrared vibrational circular dichroism (VCD) and vibrational Raman optical activity (ROA). Currently, VCD is used routinely by researchers in a variety of backgrounds, including molecular chirality, asymmetric synthesis, chiral catalysis, drug screening, pharmacology, and natural products. Although the application of ROA in AC determination lags behind that of VCD, with the recent implementation of ROA subroutines in commercial quantum chemistry software, ROA will in the future complement VCD for AC determination. In this review, the basic principles of the application of VCD to the determination of absolute configuration in chiral molecules are described. The steps required for VCD spectral measurement and calculation are outlined, followed by brief descriptions of recently published papers reporting the determination of AC in small organic, pharmaceutical, and natural product molecules.

  15. Chiral conductors from BEDT-TTF and related chiral donor molecules

    Energy Technology Data Exchange (ETDEWEB)

    Martin, L., E-mail: lee.martin@ntu.ac.u [School of Science and Technology, Nottingham Trent University, Clifton Lane, Clifton, Nottingham NG11 8BS (United Kingdom); Wallis, J.D. [School of Science and Technology, Nottingham Trent University, Clifton Lane, Clifton, Nottingham NG11 8BS (United Kingdom); Day, P. [Chemistry Department, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom); Nakatsuji, S.-I.; Yamada, J.-I.; Akutsu, H. [Graduate School of Material Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297 (Japan)

    2010-06-01

    BEDT-TTF salts have been widely studied because of their ability to combine various physical properties in the same lattice. The series of salts containing tris(oxalato)metallate anions has been widely studied and has given rise to paramagnetism, ferromagnetism, superconductivity, semiconductivity, conductivity and proton conductivity. However, one property that has not been exploited fully in this family of materials is chirality.

  16. Communication: Probing the absolute configuration of chiral molecules at aqueous interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Lotze, Stephan, E-mail: lotze@amolf.nl; Versluis, Jan [FOM Institute for Atomic and Molecular Physics, Science Park 104, 1098 XG Amsterdam (Netherlands); Olijve, Luuk L. C.; Schijndel, Luuk van; Milroy, Lech G.; Voets, Ilja K. [Laboratory of Macromolecular and Organic Chemistry, Department of Chemical Engineering and Chemistry, and Institute for Complex Molecular Systems, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Bakker, Huib J., E-mail: bakker@amolf.nl [FOM Institute AMOLF, Science Park 104, 1098 XG Amsterdam (Netherlands)

    2015-11-28

    We demonstrate that the enantiomers of chiral macromolecules at an aqueous interface can be distinguished with monolayer sensitivity using heterodyne-detected vibrational sum-frequency generation (VSFG). We perform VSFG spectroscopy with a polarization combination that selectively probes chiral molecular structures. By using frequencies far detuned from electronic resonances, we probe the chiral macromolecular structures with high surface specificity. The phase of the sum-frequency light generated by the chiral molecules is determined using heterodyne detection. With this approach, we can distinguish right-handed and left-handed helical peptides at a water-air interface. We thus show that heterodyne-detected VSFG is sensitive to the absolute configuration of complex, interfacial macromolecules and has the potential to determine the absolute configuration of enantiomers at interfaces.

  17. Quiralidade em moléculas e cristais Chirality at molecules and crystals

    Directory of Open Access Journals (Sweden)

    Ayres Guimarães Dias

    2009-01-01

    Full Text Available The present contribution describes some concepts of stereochemistry and chirality in molecules and crystals. This paper also reports on the development of a simple and fast experiment to prepare and recognize conglomerate and true racemate of tartaric acid produced by mechanic mixture of commercial enantiomers and recristalization. Optical activity and melting point of mixtures are also used in the analysis.

  18. Mirror Symmetry Breaking by Chirality Synchronisation in Liquids and Liquid Crystals of Achiral Molecules.

    Science.gov (United States)

    Tschierske, Carsten; Ungar, Goran

    2016-01-04

    Spontaneous mirror symmetry breaking is an efficient way to obtain homogeneously chiral agents, pharmaceutical ingredients and materials. It is also in the focus of the discussion around the emergence of uniform chirality in biological systems. Tremendous progress has been made by symmetry breaking during crystallisation from supercooled melts or supersaturates solutions and by self-assembly on solid surfaces and in other highly ordered structures. However, recent observations of spontaneous mirror symmetry breaking in liquids and liquid crystals indicate that it is not limited to the well-ordered solid state. Herein, progress in the understanding of a new dynamic mode of symmetry breaking, based on chirality synchronisation of transiently chiral molecules in isotropic liquids and in bicontinuous cubic, columnar, smectic and nematic liquid crystalline phases is discussed. This process leads to spontaneous deracemisation in the liquid state under thermodynamic control, giving rise to long-term stable symmetry-broken fluids, even at high temperatures. These fluids form conglomerates that are capable of extraordinary strong chirality amplification, eventually leading to homochirality and providing a new view on the discussion of emergence of uniform chirality in prebiotic systems.

  19. Life's First Handshake - Discovery of the Interstellar Chiral Molecule Propylene Oxide

    Science.gov (United States)

    McGuire, Brett A.; Carroll, P. Brandon; Loomis, Ryan A.; Finneran, Ian A.; Jewell, Philip R.; Remijan, Anthony J.; Blake, Geoffrey A.

    2016-06-01

    Life on Earth relies on chiral molecules, that is, species not superimposable on their mirror images. This manifests itself in the selection of a single molecular handedness, or homochirality, across the biosphere, and is perhaps most readily apparent in the large enhancement in biological activity of particular amino acid and sugar enantiomers. Yet, the ancestral origin of biological homochirality remains a mystery. The non-racemic ratios in some organics isolated from primitive meteorites hint at a primordial chiral seed, but even these samples have experienced substantial processing during planetary assembly, obscuring their complete histories. To determine the underlying origin of any enantiomeric excess, it is critical to understand the molecular gas from which these molecules originated. Here, we present the first extra-solar, astronomical detection of a chiral molecule, propylene oxide (CH3CHCH2O), in absorption toward the Galactic Center. We discuss the implications of the detection on observational searches to determine a primordial chiral excess, as well as the state of laboratory efforts in these areas.

  20. A Simple Method to Determine the "R" or "S" Configuration of Molecules with an Axis of Chirality

    Science.gov (United States)

    Wang, Cunde; Wu, Weiming

    2011-01-01

    A simple method for the "R" or "S" designation of molecules with an axis of chirality is described. The method involves projection of the substituents along the chiral axis, utilizes the Cahn-Ingold-Prelog sequence rules in assigning priority to the substituents, is easy to use, and has broad applicability. (Contains 5 figures.)

  1. Magnetization switching in ferromagnets by adsorbed chiral molecules without current or external magnetic field.

    Science.gov (United States)

    Ben Dor, Oren; Yochelis, Shira; Radko, Anna; Vankayala, Kiran; Capua, Eyal; Capua, Amir; Yang, See-Hun; Baczewski, Lech Tomasz; Parkin, Stuart Stephen Papworth; Naaman, Ron; Paltiel, Yossi

    2017-02-23

    Ferromagnets are commonly magnetized by either external magnetic fields or spin polarized currents. The manipulation of magnetization by spin-current occurs through the spin-transfer-torque effect, which is applied, for example, in modern magnetoresistive random access memory. However, the current density required for the spin-transfer torque is of the order of 1 × 10(6) A·cm(-2), or about 1 × 10(25) electrons s(-1) cm(-2). This relatively high current density significantly affects the devices' structure and performance. Here we demonstrate magnetization switching of ferromagnetic thin layers that is induced solely by adsorption of chiral molecules. In this case, about 10(13) electrons per cm(2) are sufficient to induce magnetization reversal. The direction of the magnetization depends on the handedness of the adsorbed chiral molecules. Local magnetization switching is achieved by adsorbing a chiral self-assembled molecular monolayer on a gold-coated ferromagnetic layer with perpendicular magnetic anisotropy. These results present a simple low-power magnetization mechanism when operating at ambient conditions.

  2. Magnetization switching in ferromagnets by adsorbed chiral molecules without current or external magnetic field

    Science.gov (United States)

    Ben Dor, Oren; Yochelis, Shira; Radko, Anna; Vankayala, Kiran; Capua, Eyal; Capua, Amir; Yang, See-Hun; Baczewski, Lech Tomasz; Parkin, Stuart Stephen Papworth; Naaman, Ron; Paltiel, Yossi

    2017-01-01

    Ferromagnets are commonly magnetized by either external magnetic fields or spin polarized currents. The manipulation of magnetization by spin-current occurs through the spin-transfer-torque effect, which is applied, for example, in modern magnetoresistive random access memory. However, the current density required for the spin-transfer torque is of the order of 1 × 106 A·cm−2, or about 1 × 1025 electrons s−1 cm−2. This relatively high current density significantly affects the devices' structure and performance. Here we demonstrate magnetization switching of ferromagnetic thin layers that is induced solely by adsorption of chiral molecules. In this case, about 1013 electrons per cm2 are sufficient to induce magnetization reversal. The direction of the magnetization depends on the handedness of the adsorbed chiral molecules. Local magnetization switching is achieved by adsorbing a chiral self-assembled molecular monolayer on a gold-coated ferromagnetic layer with perpendicular magnetic anisotropy. These results present a simple low-power magnetization mechanism when operating at ambient conditions. PMID:28230054

  3. A versatile chiral selector for determination of enantiomeric composition of fluorescent and nonfluorescent chiral molecules using steady-state fluorescence spectroscopy.

    Science.gov (United States)

    Williams, Alicia A; Fakayode, Sayo O; Lowry, Mark; Warner, Isiah M

    2009-02-01

    A fluorescent chiral molecular micelle (FCMM), poly (sodium N-undecanoyl-L-phenylalaninate) (poly-L-SUF), was developed as a chiral selector for enantiomeric recognition and determination of enantiomeric composition of four fluorescent and four nonfluorescent chiral molecules by use of steady-state fluorescence spectroscopy. The influence of FCMM concentration, buffer pH and complexation medium on FCMM-analyte host-guest complexation, and the emission spectral properties of the resulting complexes were investigated. The chiral interactions of the analytes,1,1'-binaphthyl-2,2'-diamine, 1-(9-anthryl)-2,2,2-trifluoroethanol, propranolol, naproxen, chloromethyl menthyl ether (CME), citramalic acid, tartaric acid, and limonene (LIM), in the presence of poly-L-SUF were based on diastereomeric complex formation. The figures of merit obtained from the partial-least-squares regression modeling of the calibration samples suggested good prediction ability for the validation of six of the eight chiral analytes. Better host-guest complexation of the more hydrophobic molecules, CME and LIM, were obtained in methanol/water mixtures, resulting in better predictability of the regression models. Prediction ability of the models was evaluated by use of the root-mean-square percent relative error (RMS%RE) and was found to range from 1.77 to 15.80% (buffer), 1.26 to 7.95% (25:75 methanol/water), and 1.21 to 4.28% (75:25 methanol/water).

  4. Chirality in prebiotic molecules and the phenomenon of photo- and radioracemization

    Energy Technology Data Exchange (ETDEWEB)

    Cataldo, F [Soc. Lupi Chemical Research Institute, Via Casilina 1626/A, 00133 Rome (Italy); Brucato, J R [INAF, Osservatorio Astronomico Capodimonte, Naples (Italy); Keheyan, Y [Istituto per lo studio dei Materiali Nanostrutturati, CNR, Rome (Italy)

    2005-01-01

    The abiotic origin of some biologically active molecules and macromolecules have been reviewed. Particular emphasis has been dedicated to the formation of aminoacids and about the possible mechanisms for their asymmetric synthesis and accumulation. The phenomenon of racemization has been explained in detail and then applied in the context of the photo- and radioracemization. Apparent and true photo- and radioracemization have been distinguished. These phenomena play against the preservation of chirality of asymmetric molecules in meteorites and in space. This fact may explain why low enantiomeric excess have been found in meteorites and limited only to certain aminoacids quite uncommon in terrestrial environments. It can be hypothesized that chiral molecules are formed in space for instance under the CPL photolysis and then they are slowly and unselectively degraded and radioracemized by cosmic rays and other high energy radiations. However, the experiment on the radioracemization of certain terpenes has shown that the radioracemization rate is not so dramatically high to cause the complete racemization of the mixture even at very high radiation doses. The radioracemization reaction appears not selective at all, therefore the enantiomeric excess observed only in {alpha}-methyl amino acids in meteorites must be attributed to water-thermally driven methamorphism which is instead able to cause selective racemization on {alpha}-H amino acids but not on {alpha}-methyl amino acids.

  5. Control and femtosecond time-resolved imaging of torsion in a chiral molecule

    CERN Document Server

    Hansen, Jonas L; Madsen, Christian Bruun; Lindhardt, Anders Thyboe; Johansson, Mikael P; Skrydstrup, Troels; Madsen, Lars Bojer; Stapelfeldt, Henrik

    2012-01-01

    We study how the combination of long and short laser pulses, can be used to induce torsion in an axially chiral biphenyl derivative (3,5-difluoro-3',5'-dibromo-4'-cyanobiphenyl). A long, with respect to the molecular rotational periods, elliptically polarized laser pulse produces 3D alignment of the molecules, and a linearly polarized short pulse initiates torsion about the stereogenic axis. The torsional motion is monitored in real-time by measuring the dihedral angle using femtosecond time-resolved Coulomb explosion imaging. Within the first 4 picoseconds, torsion occurs with a period of 1.25 picoseconds and an amplitude of 3 degrees in excellent agreement with theoretical calculations. At larger times the quantum states of the molecules describing the torsional motion dephase and an almost isotropic distribution of the dihedral angle is measured. We demonstrate an original application of covariance analysis of two-dimensional ion images to reveal strong correlations between specific ejected ionic fragments...

  6. Profile of students' comprehension of 3D molecule representation and its interconversion on chirality

    Science.gov (United States)

    Setyarini, M.; Liliasari, Kadarohman, Asep; Martoprawiro, Muhamad A.

    2016-02-01

    This study aims at describing (1) students' level comprehension; (2) factors causing difficulties to 3D comprehend molecule representation and its interconversion on chirality. Data was collected using multiple-choice test consisting of eight questions. The participants were required to give answers along with their reasoning. The test was developed based on the indicators of concept comprehension. The study was conducted to 161 college students enrolled in stereochemistry topic in the odd semester (2014/2015) from two LPTK (teacher training institutes) in Bandar Lampung and Gorontalo, and one public university in Bandung. The result indicates that college students' level of comprehension towards 3D molecule representations and its inter-conversion was 5% on high level, 22 % on the moderate level, and 73 % on the low level. The dominant factors identified as the cause of difficulties to comprehend 3D molecule representation and its interconversion were (i) the lack of spatial awareness, (ii) violation of absolute configuration determination rules, (iii) imprecise placement of observers, (iv) the lack of rotation operation, and (v) the lack of understanding of correlation between the representations. This study recommends that learning show more rigorous spatial awareness training tasks accompanied using dynamic visualization media of molecules associated. Also students learned using static molecular models can help them overcome their difficulties encountered.

  7. Ftmw Study of the Chirality Recognition Between Two Different Chiral Molecules: the Glycidol-Propylene Oxide Complex

    Science.gov (United States)

    Thomas, Javix; Sunahori, Fumie X.; Borho, Nicole; Xu, Yunjie

    2010-06-01

    The chirality recognition effect between the prototype chiral molecular systems, i.e. glycidol and propylene oxide has been studied using rotational spectroscopy and high level ab initio calculations. Extensive ab initio calculations have been performed to locate all possible low energy conformers of the diastereomeric pair and twenty eight minima have been found. The four most sable hetero and four homo chiral dimers, formed from the two lowest energy monomer conformations G+g- and G-g+ of the glycidol, were predicted to be close in their stability. Jet-cooled rotational spectra of some of them have been detected using a pulsed molecular beam Fourier transform microwave spectrometer and been assigned for the first time. All the low energy binary conformers observed show one primary intermolecular O-H- - -O hydrogen bond and two secondary intermolecular C-H- - -O hydrogen bonds. The induced fit phenomenon detectedwill be discussed.

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

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Ramanpreet; Vikas, E-mail: qlabspu@pu.ac.in, E-mail: qlabspu@yahoo.com [Quantum Chemistry Group, Department of Chemistry and Centre of Advanced Studies in Chemistry, Panjab University, Chandigarh 160014 (India)

    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.

  9. Using chiral molecules as an approach to address low-druggability recognition sites.

    Science.gov (United States)

    Lucas, Xavier; Günther, Stefan

    2014-11-05

    The content of chiral carbon atoms or structural complexity, which is known to correlate well with relevant physicochemical properties of small molecules, represents a promising descriptor that could fill the gap in existing drug discovery between ligand library filtering rules and the corresponding properties of the target's recognition site. Herein, we present an in silico study on the yet unclear underlying correlations between molecular complexity and other more sophisticated physicochemical and biological properties. By analyzing thousands of protein-ligand complexes from DrugBank, we show that increasing molecular complexity of drugs is an approach to addressing particularly low-druggability and polar recognition sites. We also show that biologically relevant protein classes characteristically bind molecules with a certain degree of structural complexity. Three distinct behaviors toward drug recognition are described. The reported results set the basis for a better understanding of protein-drug recognition, and open the possibility of including target information in the filtering of large ligand libraries for screening.

  10. Chiral Nanoscience and Nanotechnology

    OpenAIRE

    Dibyendu S. Bag; T.C. Shami; K.U. Bhasker Rao

    2008-01-01

    The paper reviews nanoscale science and technology of chiral molecules/macromolecules-under twosubtopics-chiral nanotechnology and nano-chiral technology. Chiral nanotechnology discusses thenanotechnology, where molecular chirality plays a role in the properties of materials, including molecularswitches, molecular motors, and other molecular devices; chiral supramolecules and self-assembled nanotubesand their functions are also highlighted. Nano-chiral technology  describes the nanoscale appr...

  11. Demonstrating Chirality: Using a Mirror with Physical Models To Show Non-superimposability of Chiral Molecules with Their Mirror Images.

    Science.gov (United States)

    Collins, Michael J.

    2001-01-01

    Presents a remarkable demonstration on chiralty in molecules and the existence of enantiomers, also known as non-superimposable mirror images. Uses a mirror, a physical model of a molecule, and a bit of trickery involving the non-superimposable mirror image. (Author/NB)

  12. Formation of chiral nanotubes by the novel anthraquinone containing-achiral molecule.

    Science.gov (United States)

    Unsal, Hande; Aydogan, Nihal

    2013-03-15

    Self-assembled lipid nanotubes arouse lots of interest due to their exceptional properties such as very simple production procedures, large variety of applications and high biocompatibility. In this study, the new eccentric but simple molecule, AQua (AQ-NH-(CH(2))(10)COOH; where AQ is anthraquinone), which integrates redox-active and pH sensitive character with nanotube forming capability has been designed. AQua forms self-assembled nanotubes by the chiral symmetry-breaking mechanism, in a high yield in the presence of ethanolamine. The nanotubes obtained in AQua-ethanolamine mixture are stable with time and resistant against drying and dilution at constant pH. However, pH change with dilution (without pH control) causes the unfolding of the nanotubes indicating the pH sensitive character. Existence of redox active anthraquinone group along with the carboxylic acid moiety gives the probability of reversibly controllable character to our nanotubes. The effect of the base type which is used to adjust the pH of the dispersion has also been investigated, and helix-tube-ribbon mixture is obtained when NaOH is used instead of ethanolamine. Although there are limited number of studies particularly in the field of reversibly controllable and/or redox active lipid nanotubes, controlled self-assembly and disassembly of these appreciable aggregates are very important for their usage in special applications. Thus, this study is hoped to be one of the remarkable studies for the development of reversibly controllable, redox active self assembled nanotubes.

  13. Chiral photochemistry

    CERN Document Server

    Inoue, Yoshihisa

    2004-01-01

    Direct Asymmetric Photochemistry with Circularly Polarized Light, H. RauCoherent Laser Control of the Handedness of Chiral Molecules, P. Brumer and M. ShapiroMagnetochiral Anisotropy in Asymmetric Photochemistry, G.L.J.A.RikkenEnantiodifferentiating Photosensitized Reactions, Y. InoueDiastereodifferentiating Photoreactions, N. Hoffmann and J.-P. PeteChirality in Photochromism, Y. Yokoyama and M. SaitoChiral Photochemistry with Transition Metal Complexes, S. Sakaki and T. HamadaTemplate-Induced Enantioselective Photochemical Reactions in S

  14. Surface second harmonic generation of chiral molecules using three-coupled-oscillator model

    Institute of Scientific and Technical Information of China (English)

    Wang Xiao-Ou; Li Chun-Fei; Li Jun-Qing

    2006-01-01

    Based on the three-coupled-oscillator molecular model we proposed, the relation between the second-order susceptibilities of a chiral film and the molecular hyperpolarizabilities is given. The effect of microscopic parameters on the second-order susceptibilities is simulated numerically and the difference between the efficiencies of s-polarized second-harmonic fields induced by the left- and the right-handed circularly-polarized fundamental beams is discussed. The theoretical basis for studying second-order nonlinear optical properties of the chiral molecular media with a tripod-like structure is provided in this paper.

  15. Molecular chirality at surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Ernst, Karl-Heinz [Empa, Swiss Federal Laboratories for Materials Science and Technology, Ueberlandstrasse 129, 8600 Duebendorf (Switzerland); Organic Chemistry Institute, University Zurich, 8057 Zuerich (Switzerland)

    2012-11-15

    With the adsorption of larger molecules being increasingly tackled by surface scientists, the aspect of chirality often plays a role. This paper gives a topical review of molecular chirality at surfaces and gives a phenomenological overview of different aspects of adsorption and self-assembly of chiral and prochiral molecules and the principles of mirror-symmetry breaking at a surface. After a brief introduction into the history of molecular chirality and the important role it played for understanding the spatial structure of molecules, definitions of chirality are presented. Topics treated here are principle ways to create single chiral adsorbates, chiral ensembles, and monolayers by achiral molecules, adsorption of intrinsically chiral molecules at achiral and chiral surfaces, long-range symmetry breaking in two-dimensional (2D) crystals due to additional chiral bias, chiral restructuring of solid surfaces under the influence of chiral molecules, switching the handedness of adsorbates, and chirality at the liquid/air interface. An outlook onto further potential research directions and recommendations for further reading, including nonsurface-related sources of chiral topics completes this paper. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Control and femtosecond time-resolved imaging of torsion in a chiral molecule

    DEFF Research Database (Denmark)

    Hansen, Jonas Lerche; Nielsen, Jens Hedegaard; Madsen, Christian Bruun;

    2012-01-01

    We study how the combination of long and short laser pulses can be used to induce torsion in an axially chiral biphenyl derivative (3,5-difluoro-3′,5′-dibromo-4′-cyanobiphenyl). A long, with respect to the molecular rotational periods, elliptically polarized laser pulse produces 3D alignment of t...

  17. Photoelectron circular dichroism of chiral molecules studied with a continuum-state-corrected strong-field approximation

    Science.gov (United States)

    Dreissigacker, Ingo; Lein, Manfred

    2014-05-01

    Motivated by recent experiments on circular dichroism in the photoelectron momentum distributions from strong-field ionization of chiral molecules [C. Lux et al., Angew. Chem. Int. Ed. 51, 5001 (2012), 10.1002/anie.201109035; C. S. Lehmann et al., J. Chem. Phys. 139, 234307 (2013), 10.1063/1.4844295], we investigate the origin of this effect theoretically. We show that it is not possible to describe photoelectron circular dichroism with the commonly used strong-field approximation due to its plane-wave nature. We therefore apply the Born approximation to the scattering state and use this as a continuum-state correction in the strong-field approximation. We obtain electron distributions for the molecules camphor and fenchone. In order to gain physical insight into the process, we study the contributions of individual molecular orientations.

  18. Extrinsic electromagnetic chirality in metamaterials

    OpenAIRE

    Plum, E.; Fedotov, V. A.; Zheludev, N. I.

    2009-01-01

    Three- and two-dimensional chirality arising from the mutual orientation of non-chiral planar metamaterial structures and the incident electromagnetic wave (extrinsic chirality) lead to pronounced optical activity, circular dichroism and asymmetric transmission indistinguishable from those seen in media consisting of three- and two-dimensionally chiral molecules (intrinsic chirality).

  19. Geometrical approach to central molecular chirality: a chirality selection rule

    OpenAIRE

    Capozziello, S.; Lattanzi, A

    2004-01-01

    Chirality is of primary importance in many areas of chemistry and has been extensively investigated since its discovery. We introduce here the description of central chirality for tetrahedral molecules using a geometrical approach based on complex numbers. According to this representation, for a molecule having n chiral centres, it is possible to define an index of chirality. Consequently a chirality selection rule has been derived which allows the characterization of a molecule as achiral, e...

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

    Science.gov (United States)

    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.

  1. Chiral Supramolecular Self-Assembly of 2,2’:6’,2”-TERPYRIDINE-4’-CARBOXYLIC Acid Molecules Chemically Adsorbed on Cu(111)

    Science.gov (United States)

    Jiang, Danfeng; Lu, Yan; Ling, Jie; Leng, Xinli; Liu, Xiaoqing; Wang, Li

    2016-06-01

    In this paper, large-area chiral supramolecular self-assembly of 2,2’:6’,2”-terpyridine-4’-carboxylic acid (C16H11N3O2; Y) molecules on Cu(111) is studied using scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. The basic building blocks of such a self-assembled monolayer are triangular vortex-shaped supramolecular structures containing three twisted Y molecules. Chirality is maintained and transferred from one vortex to the adjacent vortex in successive molecular domains within the same atomic terrace. The twisted Y molecule, bridging two nearest-neighbor Cu atoms, is stabilized by symmetric Cu-O bonds on the surface. The near perpendicularity of these bonds to the surface is the main reason for the formation of “standing-up” Y molecules.

  2. Chiral Nanoscience and Nanotechnology

    Directory of Open Access Journals (Sweden)

    Dibyendu S. Bag

    2008-09-01

    Full Text Available The paper reviews nanoscale science and technology of chiral molecules/macromolecules-under twosubtopics-chiral nanotechnology and nano-chiral technology. Chiral nanotechnology discusses thenanotechnology, where molecular chirality plays a role in the properties of materials, including molecularswitches, molecular motors, and other molecular devices; chiral supramolecules and self-assembled nanotubesand their functions are also highlighted. Nano-chiral technology  describes the nanoscale approaches to chiraltechnology such as asymmetric synthesis and catalysis, chiral separation and detection, and enantiomericanalysis. Chiral sensors have also been included. The state-of-the-art chiral research at DMSRDE,Kanpur isalso presented.Defence Science Journal, 2008, 58(5, pp.626-635, DOI:http://dx.doi.org/10.14429/dsj.58.1685

  3. Chiral Rotational Spectroscopy

    CERN Document Server

    Cameron, Robert P; Barnett, Stephen M

    2015-01-01

    We introduce chiral rotational spectroscopy: a new technique that enables the determination of the individual optical activity polarisability components $G_{XX}'$, $G_{YY}'$, $G_{ZZ}'$, $A_{X,YZ}$, $A_{Y,ZX}$ and $A_{Z,XY}$ of chiral molecules, in a manner that reveals the enantiomeric constitution of a sample whilst yielding an incisive signal even for a racemate. Chiral rotational spectroscopy could find particular use in the analysis of molecules that are chiral by virtue of their isotopic constitution and molecules with multiple chiral centres. The principles that underpin chiral rotational spectroscopy can also be exploited in the search for molecular chirality in space, which, if found, may add weight to hypotheses that biological homochirality and indeed life itself are of cosmic origin.

  4. Chiral rotational spectroscopy

    Science.gov (United States)

    Cameron, Robert P.; Götte, Jörg B.; Barnett, Stephen M.

    2016-09-01

    We introduce chiral rotational spectroscopy, a technique that enables the determination of the orientated optical activity pseudotensor components BX X, BY Y, and BZ Z of chiral molecules, in a manner that reveals the enantiomeric constitution of a sample and provides an incisive signal even for a racemate. Chiral rotational spectroscopy could find particular use in the analysis of molecules that are chiral solely by virtue of their isotopic constitution and molecules with multiple chiral centers. A basic design for a chiral rotational spectrometer together with a model of its functionality is given. Our proposed technique offers the more familiar polarizability components αX X, αY Y, and αZ Z as by-products, which could see it find use even for achiral molecules.

  5. Separation of rare gases and chiral molecules by selective binding in porous organic cages

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Linjiang; Reiss, Paul S.; Chong, Samantha Y.; Holden, Daniel; Jelfs, Kim E.; Hasell, Tom; Little, Marc A.; Kewley, Adam; Briggs, Michael E.; Stephenson, Andrew; Thomas, K. M.; Armstrong, Jayne A.; Bell, Jon; Busto, Jose; Noel, Raymond; Liu, Jian; Strachan, Denis M.; Thallapally, Praveen K.; Cooper, Andrew I.

    2014-10-31

    Abstract: The rare gases krypton, xenon, and radon pose both an economic opportunity and a potential environmental hazard. Xenon is used in commercial lighting, medical imaging, and anesthesia, and can sell for $5,000 per kilogram. Radon, by contrast, Is naturally radioactive and the second largest cause of lung cancer, and radioactive xenon, 133Xe, was a major pollutant released In the Fukushima Daiichi Nuclear Power Plant disaster. We describe an organic cage molecule that can capture xenon and radon with unprecedented selectivity, suggesting new technologies for environmental monitoring, removal of pollutants, or the recovery of rare, valuable elements from air.

  6. Ab initio study of the enantio-selective magnetic-field-induced second harmonic generation in chiral molecules.

    Science.gov (United States)

    Rizzo, Antonio; Rikken, G L J A; Mathevet, R

    2016-01-21

    We present a systematic ab initio study of enantio-selective magnetic-field-induced second harmonic generation (MFISHG) on a set of chiral systems ((l)-alanine, (l)-arginine and (l)-cysteine; 3,4-dehydro-(l)-proline; (S)-α-phellandrene; (R,S)- and (S,S)-cystine disulphide; N-(4-nitrophenyl)-(S)-prolinol, N-(4-(2-nitrovinyl)-phenyl)-(S)-prolinol, N-(4-tricyanovinyl-phenyl)-(S)-prolinol, (R)-BINOL, (S)-BINAM and 6-(M)-helicene). The needed electronic frequency dependent cubic response calculations are performed within a density functional theory (DFT) approach. A study of the dependence of the property on the choice of electron correlation, on one-electron basis set extension and on the choice of magnetic gauge origin is carried out on a prototype system (twisted oxygen peroxide). The magnetic gauge dependence analysis is extended also to the molecules of the set. An attempt to analyze the structure-property relationships is also made, based on the results obtained for biphenyl (in a frozen twisted conformation), for prolinol and for some of their derivatives. The strength of the effect is discussed, in order to establish its measurability with a proposed experimental setup.

  7. Molecular model for chirality phenomena.

    Science.gov (United States)

    Latinwo, Folarin; Stillinger, Frank H; Debenedetti, Pablo G

    2016-10-21

    Chirality is a hallmark feature for molecular recognition in biology and chemical physics. We present a three-dimensional continuum model for studying chirality phenomena in condensed phases using molecular simulations. Our model system is based upon a simple four-site molecule and incorporates non-trivial kinetic behavior, including the ability to switch chirality or racemize, as well as thermodynamics arising from an energetic preference for specific chiral interactions. In particular, we introduce a chiral renormalization parameter that can locally favor either homochiral or heterochiral configurations. Using this model, we explore a range of chirality-specific phenomena, including the kinetics of chiral inversion, the mechanism of spontaneous chiral symmetry breaking in the liquid, chirally driven liquid-liquid phase separation, and chiral crystal structures.

  8. Conformational preferences of chiral molecules: free-jet rotational spectrum of 1-(4-fluorophenyl)-1-ethanol

    Energy Technology Data Exchange (ETDEWEB)

    Velino, Biagio [Dipartimento di Chimica Fisica e Inorganica dell' Universita, Viale Risorgimento 4, I-40136 Bologna (Italy); Satta, Mauro [Dipartimento di Chimica, Universita di Roma ' La Sapienza' and CNR (IMIP and ISC), Ple Aldo Moro 5, Roma (Italy); Caminati, Walther [Dipartimento di Chimica ' G Ciamician' dell' Universita, Via Selmi 2, I-40126 Bologna (Italy)], E-mail: walther.caminati@unibo.it

    2008-11-15

    The rotational spectra of normal and O-d species of the most stable conformer of chiral 1-(4-fluorophenyl)-1-ethanol have been measured by free-jet absorption millimeter-wave spectroscopy. The observed species is stabilized by an O-H-{pi} interaction and it is at least 1 kcal mol{sup -1} more stable than the remaining conformers.

  9. Superconductivity in a chiral nanotube

    Science.gov (United States)

    Qin, F.; Shi, W.; Ideue, T.; Yoshida, M.; Zak, A.; Tenne, R.; Kikitsu, T.; Inoue, D.; Hashizume, D.; Iwasa, Y.

    2017-02-01

    Chirality of materials are known to affect optical, magnetic and electric properties, causing a variety of nontrivial phenomena such as circular dichiroism for chiral molecules, magnetic Skyrmions in chiral magnets and nonreciprocal carrier transport in chiral conductors. On the other hand, effect of chirality on superconducting transport has not been known. Here we report the nonreciprocity of superconductivity--unambiguous evidence of superconductivity reflecting chiral structure in which the forward and backward supercurrent flows are not equivalent because of inversion symmetry breaking. Such superconductivity is realized via ionic gating in individual chiral nanotubes of tungsten disulfide. The nonreciprocal signal is significantly enhanced in the superconducting state, being associated with unprecedented quantum Little-Parks oscillations originating from the interference of supercurrent along the circumference of the nanotube. The present results indicate that the nonreciprocity is a viable approach toward the superconductors with chiral or noncentrosymmetric structures.

  10. X-ray absorption spectroscopy of the chiral molecules fenchone, α-pinene, limonene and carvone in the C1s excitation region

    Energy Technology Data Exchange (ETDEWEB)

    Ozga, Christian, E-mail: ozga@physik.uni-kassel.de [Institute for Physics and CINSaT, University of Kassel, Heinrich-Plett Str. 40, 34132 Kassel (Germany); Jänkälä, Kari [Centre for Molecular Materials Research, University of Oulu, PO Box 3000, 90014 Oulu (Finland); Schmidt, Philipp; Hans, Andreas; Reiß, Philipp; Ehresmann, Arno; Knie, André [Institute for Physics and CINSaT, University of Kassel, Heinrich-Plett Str. 40, 34132 Kassel (Germany)

    2016-02-15

    Highlights: • Determination of the X-ray absorption spectra for two terpenoids and two terpenes. • Allocation of predominant or even site-selective excitation of stereocenters. • Fragment fluorescence spectra of the prototype molecules are identical. • Presented data can be used for future fluorescence circular dichroism experiments. - Abstract: Relative ionization cross sections and fluorescence intensities as functions of the exciting-photon energy were recorded for the chiral molecules carvone, α-pinene, limonene and fenchone after excitation by monochromatized synchrotron radiation with energies of the exciting-photons between 284 eV and 289 eV. At selected exciting-photon energies dispersed fragment fluorescence spectra in the wavelength range between 365 nm and 505 nm were obtained. Time dependent density functional theory (TD-DFT) computations were performed to analyze the experimentally observed resonance-structures. Comparison of the computed and recorded spectra demonstrates the possibility of a predominant or even specific excitation of one particular stereocenter site in a molecule with more than one stereocenter.

  11. Evolução biomolecular homoquiral: a origem e a amplificação da quiralidade nas moléculas da vida Homochiral biomolecular evolution: the origin and the amplification of chirality in life molecules

    Directory of Open Access Journals (Sweden)

    José Augusto R. Rodrigues

    2010-01-01

    Full Text Available The fact that biologically relevant molecules exist only as one of the two enantiomers is a fascinating example of complete symmetry breaking of chirality and has long intrigued our curiosity. The origin of this selective chirality has remained a fundamental enigma with regard to the origin of life since the time of Pasteur, 160 years ago. The symmetry breaking processes, which include autocatalytic crystallization, asymmetric autocatalysis, spontaneous crystallization, adsorption and polymerization of amino acids on mineral surfaces, provide new insights into the origin of biomolecular homochirality.

  12. Selective binding of chiral molecules of cinchona alkaloid by beta- and gamma-cyclodextrins and organoselenium-bridged bis(beta-cyclodextrin)s.

    Science.gov (United States)

    Liu, Yu; Li, Li; Zhang, Heng-Yi; Fan, Zhi; Guan, Xu-Dong

    2003-02-01

    The inclusion complexation behavior of chiral members of cinchona alkaloid with beta- and gamma-cyclodextrins (1 and 2) and 6,6(')-trimethylenediseleno-bridged bis(beta-cyclodextrin) (3) was assessed by means of fluorescence and 2D-NMR spectroscopy. The spectrofluorometric titrations have been performed in aqueous buffer solution (pH 7.20) at 25.0 degrees C to determine the stability constants of the inclusion complexation of 1-3 with guest molecules (i.e., cinchonine, cinchonidine, quinine, and quinidine) in order to quantitatively investigate the molecular selective binding ability. The stability constants of the resulting complexes of 2 with guest molecules are larger than that of 1. As a result of cooperative binding, the stability constants of inclusion complexation of dimeric beta-cyclodextrin 3 with cinchonidine and cinchonine are higher than that of parent 1 by factor of 4.5 and 2.4, respectively. These results are discussed from the viewpoint of the size-fit and geometric complementary relationship between the host and guest.

  13. Theoretical description of circular dichroism in photoelectron angular distributions of randomly oriented chiral molecules after multi-photon photoionization

    CERN Document Server

    Goetz, R E; Nikoobakht, B; Berger, R; Koch, C P

    2016-01-01

    Photoelectron circular dichroism refers to the forward/backward asymmetry in the photoelectron angular distribution with respect to the propagation axis of circularly polarized light. It has recently been demonstrated in femtosecond multi-photon photoionization experiments with randomly oriented camphor and fenchone molecules [C. Lux et al., Angew. Chem. Int. Ed. 51, 5001 (2012);C. S. Lehmann et al., J. Chem. Phys. 139, 234307 (2013)]. A theoretical framework describing this process as (2+1) resonantly enhanced multi-photon ionization is constructed, which consists of two-photon photoselection from randomly oriented molecules and successive one-photon ionisation of the photoselected molecules. It combines perturbation theory for the light-matter interaction with ab initio calculations for the two-photon absorption and a single-center expansion of the photoelectron wavefunction in terms of hydrogenic continuum functions. It is verified that the model correctly reproduces the basic symmetry behavior expected un...

  14. Theoretical description of circular dichroism in photoelectron angular distributions of randomly oriented chiral molecules after multi-photon photoionization

    Science.gov (United States)

    Goetz, R. E.; Isaev, T. A.; Nikoobakht, B.; Berger, R.; Koch, C. P.

    2017-01-01

    Photoelectron circular dichroism refers to the forward/backward asymmetry in the photoelectron angular distribution with respect to the propagation axis of circularly polarized light. It has recently been demonstrated in femtosecond multi-photon photoionization experiments with randomly oriented camphor and fenchone molecules [C. Lux et al., Angew. Chem., Int. Ed. 51, 4755 (2012) and C. S. Lehmann et al., J. Chem. Phys. 139, 234307 (2013)]. A theoretical framework describing this process as (2+1) resonantly enhanced multi-photon ionization is constructed, which consists of two-photon photoselection from randomly oriented molecules and successive one-photon ionization of the photoselected molecules. It combines perturbation theory for the light-matter interaction with ab initio calculations for the two-photon absorption and a single-center expansion of the photoelectron wavefunction in terms of hydrogenic continuum functions. It is verified that the model correctly reproduces the basic symmetry behavior expected under exchange of handedness and light helicity. When applied to fenchone and camphor, semi-quantitative agreement with the experimental data is found, for which a sufficient d wave character of the electronically excited intermediate state is crucial.

  15. Transfer of noncovalent chiral information along an optically inactive helical peptide chain: allosteric control of asymmetry of the C-terminal site by external molecule that binds to the N-terminal site.

    Science.gov (United States)

    Ousaka, Naoki; Inai, Yoshihito

    2009-02-20

    This study aims at demonstrating end-to-end transfer of noncovalent chiral information along a peptide chain. The domino-type induction of helical sense is proven by using achiral peptides 1-m of bis-chromophoric sequence with different chain lengths: H-(Aib-Delta(Z)Phe)(m)-(Aib-Delta(Z)Bip)(2)-Aib-OCH(3) [m = 2, 4, and 6; Aib = alpha-aminoisobutyric acid; Delta(Z)Phe = (Z)-alpha,beta-didehydrophenylalanine; Delta(Z)Bip = (Z)-beta-(4,4'-biphenyl)-alpha,beta-didehydroalanine]. They all showed the tendency to adopt a 3(10)-helix. Whereas peptide 1-m originally shows no circular dichroism (CD) signals, marked CD signals were induced at around 270-320 nm based on both the beta-aryl didehydroresidues by chiral Boc-proline (Boc = tert-butoxycarbonyl). The observed CD spectra were interpreted on the basis of the exciton chirality method and theoretical CD simulation of several helical conformations that were energy-minimized. The experimental and theoretical CD analysis reveals that Boc-l-proline induces the preference for a right-handed helicity in the whole chain of 1-m. Such noncovalent chiral induction was not observed in the corresponding N-terminally protected 1-m. Obviously, helicity induction in 1-m originates from the binding of Boc-proline to the N-terminal site. In the 17-mer (1-6), the information of helix sense reaches the 16th residue from the N-terminus. We have monitored precise transfer of noncovalent chiral stimulus along a helical peptide chain. The present study also proposes a primitive allosteric model of a single protein-mimicking backbone. Here chiral molecule binding the N-terminal site of 1-6 controls the chiroptical signals and helical sense of the C-terminal site about 30 A away.

  16. On the Biological Advantage of Chirality

    OpenAIRE

    1999-01-01

    The presence of chirality in the main molecules of life may well be not just a structural artifact, but of pure biological advantage. The possibility of the existence of a phenomenon of a special mode of interaction, labeled as "chiral interaction" (CI), for which structural chirality is a necessary condition, is the main reason for such an advantage. In order to demonstrate such a possibility, macroscopic chiral devices are introduced and presented as analogies for such an interaction. For t...

  17. A web site for calculating the degree of chirality.

    Science.gov (United States)

    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.

  18. Single chirality through crystal grinding

    NARCIS (Netherlands)

    Noorduin, W.L.

    2010-01-01

    The properties of chiral molecules in living organisms can be different for left- and right-handed molecules. Therefore, ways to produce molecules of single handedness are of paramount importance, especially for economical, high yielding processes to synthesize pharmaceutical compounds that must be

  19. Free-standing chiral plasmonics

    Science.gov (United States)

    Leong, Eunice Sok Ping; Deng, Jie; Wu, Siji; Khoo, Eng Huat; Liu, Yan Jun

    2014-11-01

    Chiral plasmonic nanostructures offer the ability to achieve strong optical circular dichroism (CD) activity over a broad spectral range, which has been challenging for chiral molecules. Chiral plasmonic nanostructures have been extensively studied based on top-down and bottom-up fabrication techniques. Particularly, in the top-down electron-beam lithography, 3D plasmonic nanostructure fabrication involves layer-by-layer patterning and complex alignment, which is time-consuming and causes many defects in the structures. Here, we present a free-standing 3D chiral plamonic nanostructures using the electron-beam lithography technique with much simplified fabrication processes. The 3D chiral plasmonic nanostructures consist of a free-standing ultrathin silicon nitride membrane with well-aligned L-shape metal nanostructures on one side and disk-shape ones on the other side. The free-standing membrane provides an ultra-smooth metal/dielectric interface and uniformly defines the gap between the upper and lower layers in an array of chiral nanostructures. Such free-standing chiral plasmonic nanostructures exhibit strong CD at optical frequencies, which can be engineered by simply changing the disk size on one side of the membrane. Experimental results are in good agreement with the finite-difference time-domain simulations. Such free-standing chiral plasmonics holds great potential for chirality analysis of biomolecules, drugs, and chemicals.

  20. Chiral nanophotonics chiral optical properties of plasmonic systems

    CERN Document Server

    Schäferling, Martin

    2017-01-01

    This book describes the physics behind the optical properties of plasmonic nanostructures focusing on chiral aspects. It explains in detail how the geometry determines chiral near-fields and how to tailor their shape and strength. Electromagnetic fields with strong optical chirality interact strongly with chiral molecules and, therefore, can be used for enhancing the sensitivity of chiroptical spectroscopy techniques. Besides a short review of the latest results in the field of plasmonically enhanced enantiomer discrimination, this book introduces the concept of chiral plasmonic near-field sources for enhanced chiroptical spectroscopy. The discussion of the fundamental properties of these light sources provides the theoretical basis for further optimizations and is of interest for researchers at the intersection of nano-optics, plasmonics and stereochemistry. .

  1. METHODS DEVELOPMENT FOR THE ANALYSIS OF CHIRAL PESTICIDES

    Science.gov (United States)

    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...

  2. A Combined Synchrotron-Based High Resolution FTIR and Diode Laser Jet Infrared Spectroscopy Study of the Chiral Molecule CDBrClF

    Science.gov (United States)

    Albert, S.; Albert, K. Keppler; Quack, M.; Lerch, Ph.; Boudon, V.

    2013-06-01

    The experimental detection of molecular parity violation Δ_{PV}E is of great interest because of its importance in the understanding of fundamental aspects of molecular dynamics and symmetries. One possible method for this is measuring rovibrational or rotational frequency shifts in the infrared or microwave spectra of enantiomers. For that reason we have measured and analysed the rotationally resolved infrared spectrum of CDBrClF as a prototype spectrum for a chiral molecule using three different techniques. The spectrum has been recorded at room temperature with the Zurich Bruker IFS spectrometer ZP 2001 and with the Bruker interferometer 2009 connected to the Swiss synchrotron using a resolution of 0.0007 cm^{-1}. In addition, the IR spectrum of CDBrClF has been measured at low temperature with our diode laser jet setup in the ν_5 region. The spectra of the two major isotopomers CD^{81}Br^{35}ClF and CD^{79}Br^{35}ClF have been analysed within the ν_5 (CCl-stretch), ν_4 (CF-stretch) and ν_3 (CDF-bend) regions. A detailed rovibrational analysis of these bands is presented. The role for possible experiments in the experimental detection of molecular parity violation shall be discussed. M. Quack, Fundamental symmetries and symmetry violations in Handbook of High Resolution Spectroscopy, Vol. 1(Eds. M. Quack and F. Merkt), Wiley, Chichester, New York 2011, 659-722, M. Quack, J. Stohner and M. Willeke, Annu. Rev. Phys. Chem. 2008, 59, 741, A. Bakasov, T.K. Ha, and M. Quack, J. Chem. Phys. 1998, 109, 7263, R. Berger and M. Quack, J. Chem. Phys, 2000, 112, 3148. M. Quack and J. Stohner, Phys. Rev. Lett. 2000, 84, 3807, M. Quack and J. Stohner. J. Chem. Phys., 2003, 119, 11228. S. Albert, K. Keppler Albert and M. Quack, High Resolution Fourier Transform Infrared Spectroscopy in Handbook of High Resolution Spectroscopy, Vol. 2 (Eds. M. Quack and F. Merkt), Wiley, Chichester, New York 2011, 965-1019, S. Albert and M. Quack, ChemPhysChem, 2007, 8, 1271-1281. S. Albert

  3. Chiral superconductors.

    Science.gov (United States)

    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.

  4. Mechanism of chirality conversion by periodic change of temperature: Role of chiral clusters

    Science.gov (United States)

    Katsuno, Hiroyasu; Uwaha, Makio

    2016-01-01

    By grinding crystals in a solution, the chirality of crystal structure (and the molecular chirality for the case of chiral molecules as well) can be converted, and the cause of the phenomenon is attributed to crystal growth with chiral clusters. We show that the recently found chirality conversion with a periodic change of temperature can also be explained by crystal growth with chiral clusters. With the use of a generalized Becker-Döring model, which includes enantio-selective incorporation of small chiral clusters to large solid clusters, the change of cluster distribution and the mass flow between clusters are studied. The chiral clusters act as a reservoir to pump out the minority species to the majority, and the exponential amplification of the enantiomeric excess found in the experiment is reproduced in the numerical calculation.

  5. Asymmetric synthesis using chiral-encoded metal

    Science.gov (United States)

    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.

  6. Enantioselective recognition at mesoporous chiral metal surfaces

    Science.gov (United States)

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

    2014-02-01

    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.

  7. Isotopic chirality

    Energy Technology Data Exchange (ETDEWEB)

    Floss, H.G. [Univ. of Washington, Seattle, WA (United States)

    1994-12-01

    This paper deals with compounds that are chiral-at least in part, due to isotope substitution-and their use in tracing the steric course of enzyme reaction in vitro and in vivo. There are other applications of isotopically chiral compounds (for example, in analyzing the steric course of nonenzymatic reactions and in probing the conformation of biomolecules) that are important but they will not be discussed in this context.

  8. Chiral quantum dot based materials

    Science.gov (United States)

    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.

  9. Large Enhancement of Circular Dichroism Using an Embossed Chiral Metamaterial

    CERN Document Server

    Mousavi, S Hamed Shams; El-Sayed, Mostafa A; Eftekhar, Ali A; Adibi, Ali

    2016-01-01

    In the close vicinity of a chiral nanostructure, the circular dichroism of a biomolecule could be greatly enhanced, due to the interaction with the local superchiral fields. Modest enhancement of optical activity using a planar metamaterial, with some chiral properties, and achiral nanoparticles has been previously reported. A more substantial chirality enhancement can be achieved in the local filed of a chiral nanostructure with a three-dimensional arrangement. Using an embossed chiral nanostructure designed for chiroptical sensing, we measure the circular dichroism spectra of two biomolecules, Chlorophylls A and B, at the molecular level, using a simple polarization resolved reflection measurement. This experiment is the first realization of the on-resonance surface-enhanced circular dichroism, achieved by matching the chiral resonances of a strongly chiral metamaterial with that of a chiral molecule, resulting in an unprecedentedly large differential CD spectrum from a monolayer of a chiral material.

  10. Spatial control of chirality in supramolecular aggregates.

    Science.gov (United States)

    Castriciano, Maria A; Gentili, Denis; Romeo, Andrea; Cavallini, Massimiliano; Scolaro, Luigi Monsù

    2017-03-09

    Chirality is one of the most intriguing properties of matter related to a molecule's lack of mirror symmetry. The transmission of chirality from the molecular level up to the macroscopic scale has major implications in life sciences but it is also relevant for many chemical applications ranging from catalysis to spintronic. These technological applications require an accurate control of morphology, homogeneity and chiral handedness of thin films and nanostructures. We demonstrate a simple approach to specifically transfer chirality to the model supramolecular system of J aggregates of the protonated form of tetrakis(4-sulfonatophenyl)-porphyrin by utilizing a soft lithography technique. This approach successfully allows the fabrication of an ordered distribution of sub-micrometric structures in precise and controllable positions with programmed chirality, providing a fundamental breakthrough toward the exploitation of chiral supramolecular aggregates in technological applications, such as sensors, non-linear optics and spintronic.

  11. Chiral cardiovascular drugs: an overview.

    Science.gov (United States)

    Ranade, Vasant V; Somberg, John C

    2005-01-01

    Stereochemistry in drug molecules is rapidly becoming an important aspect in drug research, design, and development. Recently, individual stereoisomers of drug molecules with asymmetric centers such as fexofenadine, cetirizine, verapamil, fluoxetine, levalbutarol, and amphetamine, for example, have been separated and developed as individual drugs. These stereoisomers have different therapeutic activity, and each isomer has contributed differently with respect to its formulation's pharmacologic activity, side effects, and toxicity. The present overview discusses chirality among a select group of cardiovascular drugs, their stereochemical synthesis/preparation, isolation techniques using chiral chromatography, methods for confirmation of their enantiomeric purity, pharmacodynamics, and pharmacokinetics. Chirality has been visualized as an important factor in cardiovascular research. It is also becoming evident in other areas of therapeutics.

  12. The Chiral Dipolar Hard Sphere Model.

    OpenAIRE

    Mazars, Martial

    2009-01-01

    Abstract A simple molecular model of chiral molecules is presented in this paper : the chiral dipolar hard sphere model. The discriminatory interaction between enantiomers is represented by electrostatic (or magnetic) dipoles-dipoles interactions : short ranged steric repulsion are represented by hard sphere potential and, in each molecule, two point dipoles are located inside the sphere. The model is described in detail and some of its elementary properties are given ; in particul...

  13. Cosmic chirality both true and false.

    Science.gov (United States)

    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.

  14. A liquid crystalline chirality balance for vapours

    Science.gov (United States)

    Ohzono, Takuya; Yamamoto, Takahiro; Fukuda, Jun-Ichi

    2014-04-01

    Chiral discrimination of vapours plays an important role in olfactory perception of biological systems and its realization by artificial sensors has been an intriguing challenge. Here, we report a simple method that tangibly visualizes the chirality of a diverse variety of molecules dissolved from vapours with high sensitivity, by making use of a structural change in a periodic microstructure of a nematic liquid crystal confined in open microchannels. This microstructure is accompanied by a topological line defect of a zigzag form with equal lengths of ‘zig’ and ‘zag.’ We find that a tiny amount of vapour of chiral molecules injected onto the liquid crystal induces the imbalance of ‘zig’ and ‘zag’ depending on its enantiomeric excess within a few seconds. Our liquid-crystal-based ‘chirality balance’ offers a simple, quick and versatile chirality-sensing/-screening method for gas-phase analysis (for example, for odours, environmental chemicals or drugs).

  15. Chirality on Surfaces: Modeling and Behaviour.

    Energy Technology Data Exchange (ETDEWEB)

    Paci, Irina; Szleifer, Igal; Ratner, Mark A.

    2007-09-01

    The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. Chirality has been a fascinating topic in chemistry, ever since its first observation by Biot in 1815. Its molecular basis was first understood by Pasteur in 1848. Enantiomers, identical in every way but mirror-images of each other, have similar physical properties, behave identically in chemical reactions with achiral molecules, but have very different interactions with chiral molecules. In recent decades, chirality has become an important direction in pharmaceutical research, as many drugs have stereoselective activity. This review focuses on a new aspect of chiral resolution on solid surfaces, and relationships between molecular structure, thermodynamic effects, and the result of chiral surface self-organization.

  16. Intelligent Chiral Sensing Based on Supramolecular and Interfacial Concepts

    Directory of Open Access Journals (Sweden)

    Hironori Izawa

    2010-07-01

    Full Text Available 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.

  17. Development of Chiral LC-MS Methods for small Molecules and Their Applications in the Analysis of Enantiomeric Composition and Pharmacokinetic Studies

    Energy Technology Data Exchange (ETDEWEB)

    Meera Jay Desai

    2004-12-19

    The purpose of this research was to develop sensitive LC-MS methods for enantiomeric separation and detection, and then apply these methods for determination of enantiomeric composition and for the study of pharmacokinetic and pharmacodynamic properties of a chiral nutraceutical. Our first study, evaluated the use of reverse phase and polar organic mode for chiral LC-API/MS method development. Reverse phase methods containing high water were found to decrease ionization efficiency in electrospray, while polar organic methods offered good compatibility and low limits of detection with ESI. The use of lower flow rates dramatically increased the sensitivity by an order of magnitude. Additionally, for rapid chiral screening, the coupled Chirobiotic column afforded great applicability for LC-MS method development. Our second study, continued with chiral LC-MS method development in this case for the normal phase mode. Ethoxynonafluorobutane, a fluorocarbon with low flammability and no flashpoint, was used as a substitute solvent for hexane/heptane mobile phases for LC-APCI/MS. Comparable chromatographic resolutions and selectivities were found using ENFB substituted mobile phase systems, although, peak efficiencies were significantly diminished. Limits of detection were either comparable or better for ENFB-MS over heptane-PDA detection. The miscibility of ENFB with a variety of commonly used organic modifiers provided for flexibility in method development. For APCI, lower flow rates did not increase sensitivity as significantly as was previously found for ESI-MS detection. The chiral analysis of native amino acids was evaluated using both APCI and ESI sources. For free amino acids and small peptides, APCI was found to have better sensitivities over ESI at high flow rates. For larger peptides, however, sensitivity was greatly improved with the use of electrospray. Additionally, sensitivity was enhanced with the use of non-volatile additives, This optimized method was then

  18. Development of Chiral LC-MS Methods for small Molecules and Their Applications in the Analysis of Enantiomeric Composition and Pharmacokinetic Studies

    Energy Technology Data Exchange (ETDEWEB)

    Desai, Meera Jay [Iowa State Univ., Ames, IA (United States)

    2004-01-01

    The purpose of this research was to develop sensitive LC-MS methods for enantiomeric separation and detection, and then apply these methods for determination of enantiomeric composition and for the study of pharmacokinetic and pharmacodynamic properties of a chiral nutraceutical. Our first study, evaluated the use of reverse phase and polar organic mode for chiral LC-API/MS method development. Reverse phase methods containing high water were found to decrease ionization efficiency in electrospray, while polar organic methods offered good compatibility and low limits of detection with ESI. The use of lower flow rates dramatically increased the sensitivity by an order of magnitude. Additionally, for rapid chiral screening, the coupled Chirobiotic column afforded great applicability for LC-MS method development. Our second study, continued with chiral LC-MS method development in this case for the normal phase mode. Ethoxynonafluorobutane, a fluorocarbon with low flammability and no flashpoint, was used as a substitute solvent for hexane/heptane mobile phases for LC-APCI/MS. Comparable chromatographic resolutions and selectivities were found using ENFB substituted mobile phase systems, although, peak efficiencies were significantly diminished. Limits of detection were either comparable or better for ENFB-MS over heptane-PDA detection. The miscibility of ENFB with a variety of commonly used organic modifiers provided for flexibility in method development. For APCI, lower flow rates did not increase sensitivity as significantly as was previously found for ESI-MS detection. The chiral analysis of native amino acids was evaluated using both APCI and ESI sources. For free amino acids and small peptides, APCI was found to have better sensitivities over ESI at high flow rates. For larger peptides, however, sensitivity was greatly improved with the use of electrospray. Additionally, sensitivity was enhanced with the use of non-volatile additives, This optimized method was then

  19. Synthesis of chiral dopants based on carbohydrates.

    Science.gov (United States)

    Tsuruta, Toru; Koyama, Tetsuo; Yasutake, Mikio; Hatano, Ken; Matsuoka, Koji

    2014-07-01

    Chiral dopants based on carbohydrates for nematic liquid crystals were synthesized from D-glucose, and their helical twisting power (HTP) values were evaluated. The chiral dopants induced helices in the host nematic liquid crystals. An acetyl derivative having an ether-type glycosidic linkage between carbohydrate and a mesogenic moiety showed the highest HTP value of 10.4 μm(-1), while an acetyl derivative having an anomeric ester-type linkage did not show any HTP. It was surprising that this molecule had no HTP despite the presence of chirality in the molecule. A relationship between HTP and specific rotation was not observed in this study.

  20. Optical properties and circular dichroism of chiral metal nanoparticles

    Science.gov (United States)

    Fan, Zhiyuan; Govorov, Alexander; OU Team

    2013-03-01

    In nature, biological systems are built up by homochiral building blocks, such as a sugar and protein. Circular dichroism (CD) is an effective tool of resolving molecular conformations. It utilizes circularly polarized light to detect differential absorption of chiral materials. In medicine, it will help us to develop new drugs and therapies, if we understand the connection between the physical or chemical properties of drug molecules and their conformations. With the rapid development of nanotechnologies, chiral nanomaterials attract lots of attention nowadays. CD signals of chiral molecules can be enhanced or shifted to the visible band in the presence of plasmonic nanocrystals. Here we present a plasmonic CD mechanism from a single chiral metal nanocrystal. The mechanism is essentially different from the dipolar plasmon-plasmon interaction in a chiral NP assembly, which mimics the CD mechanism of chiral molecules. Chiral metal nanocrystals are expected to have promising applications in biosensing. Recently a few experimental papers reported successful realizations of chiral nanocrystals in a macroscopic ensemble in solution. Particularly the paper described silver nanoparticles grown on chiral template molecules and demonstrating characteristic CD signals at a plasmonic wavelength. The plasmonic CD signals in Ref. can come from a dipolar plasmon-molecule interaction or from a chiral shape of nanocrystals. This work was supported by the NSF (project: CBET- 0933782) and by the Volkswagen Foundation.

  1. Chirality and anaesthetic drugs: A review and an update

    OpenAIRE

    Sukanya Mitra; Puneet Chopra

    2011-01-01

    Many molecules can exist as right-handed and left-handed forms that are non-superimposable mirror images of each other. They are known as enantiomers or substances of opposite shape. Such compounds are also said to be chiral (Greek chiros meaning ‘hand’). Such chiral molecules are of great relevance to anaesthetic theory and practice. This review summarizes the basic concepts, pharmacokinetic and pharmacodynamic aspects of chirality, and some specific examples of their application in anaesthe...

  2. Design and synthesis of novel chiral molecular tweezers based on deoxycholic acid

    Institute of Scientific and Technical Information of China (English)

    Zhi Gang Zhao; Xing Li Liu; Yi Zhong

    2008-01-01

    A novel type of chiral molecular tweezers has been designed and synthesized by using deoxycholic acid as backbone and ethanoyl and the chiral unsymmetrical urea unit as arms. Their structures were characterized by 1H NMR, IR, MS spectra and elemental analysis. These molecular tweezers showed good binding ability for neutral molecules and chiral molecules.

  3. Chirality detection of enantiomers using twisted optical metamaterials

    Science.gov (United States)

    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.

  4. Chiral Biomarkers in Meteorites

    Science.gov (United States)

    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

  5. A molecular propeller effect for chiral separation and analysis

    Science.gov (United States)

    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.

  6. Stegosaurus chirality

    OpenAIRE

    Cameron, R.P.; Cameron, J. A.; Barnett, S. M.

    2016-01-01

    We explain that Stegosaurus exhibited exterior chirality and observe that the largest plate in particular of USNM 4394, USNM 4714, DMNS 2818 and NHMUK R36730 appears to have tilted to the right rather than to the left in each case. Several instances in which Stegosaurus specimens have been confused with their distinct, hypothetical mirror-image forms are highlighted. We believe our findings to be consistent with the hypothesis that Stegosaurus's plates acted primarily as display structures. A...

  7. Nematic twist cell: Strong chirality induced at the surfaces

    Science.gov (United States)

    Lin, Tzu-Chieh; Nemitz, Ian R.; Pendery, Joel S.; Schubert, Christopher P. J.; Lemieux, Robert P.; Rosenblatt, Charles

    2013-04-01

    A nematic twist cell having a thickness gradient was filled with a mixture containing a configurationally achiral liquid crystal (LC) and chiral dopant. A chiral-based linear electrooptic effect was observed on application of an ac electric field. This "electroclinic effect" varied monotonically with d, changing sign at d =d0 where the chiral dopant exactly compensated the imposed twist. The results indicate that a significant chiral electrooptic effect always exists near the surfaces of a twist cell containing molecules that can be conformationally deracemized. Additionally, this approach can be used to measure the helical twisting power (HTP) of a chiral dopant in a liquid crystal.

  8. Embarras de richesses – It is not good to be too anomalous: Accurate structure of selenourea, a chiral crystal of planar molecules

    Science.gov (United States)

    Luo, Zhipu

    2017-01-01

    Selenourea, SeC(NH2)2, recently found an application as a derivatization reagent providing a significant anomalous diffraction signal used for phasing macromolecular crystal structures. The crystal structure of selenourea itself was solved about 50 years ago, from data recorded on films and evaluated by eye and refined to R = 0.15 with errors of bond lengths and angles about 0.1 Å and 6°. In the current work this structure is re-evaluated on the basis of synchrotron data and refined to R1 = 0.021 with bond and angle errors about 0.007 Å and 0.5°. The nine planar molecules of selenourea pack either in the P31 or in the P32 unit cell. All unique molecules are connected by a complex network of Se•••H-N hydrogen bonds and Se•••Se contacts. The packing of selenourea molecules is highly pseudosymmetric, approximating either of the P31(2)12, R3, and R32 space groups. Because the overwhelming majority of diffracted X-ray intensity originates form the anomalously scattering selenium atoms, the measurable anomalous Bijvoet differences are diminished and it was not possible to solve this crystal structure based on the anomalous signal alone. PMID:28207770

  9. A liquid crystalline chirality balance for vapours

    OpenAIRE

    Ohzono, Takuya; Yamamoto, Takahiro; Fukuda, Jun-Ichi

    2014-01-01

    Chiral discrimination of vapours plays an important role in olfactory perception of biological systems and its realization by artificial sensors has been an intriguing challenge. Here, we report a simple method that tangibly visualizes the chirality of a diverse variety of molecules dissolved from vapours with high sensitivity, by making use of a structural change in a periodic microstructure of a nematic liquid crystal confined in open microchannels. This microstructure is accompanied by a t...

  10. [Cu3(Hmesox)3]3-: a precursor for the rational design of chiral molecule-based magnets (H4mesox = 2-dihydroxymalonic acid).

    Science.gov (United States)

    Sanchiz, Joaquín; Pasán, Jorge; Fabelo, Oscar; Lloret, Francesc; Julve, Miguel; Ruiz-Pérez, Catalina

    2010-09-06

    Two new compounds K(3)[Cu(3)(Hmesox)(3)(H(2)O)] x 4 H(2)O (1) and {(PPh(4))(2)[CoCu(3)(Hmesox)(3)Cl]} (2) [H(4)mesox = mesoxalic acid (2-dihydroxymalonic acid) and PPh(4)(+) = tetraphenylphosphonium cation] have been prepared and magneto-structurally characterized. Compound 1 contains the [Cu(3)(Hmesox)(3)](3-) entity which can be considered as a new precursor for molecular magnetism. In 1 the triangular arrangement of three copper(II) ions bridged by alkoxo groups are further connected to a symmetry-related tricopper(II) unit through a double oxo(carboxylate) bridge. The resulting hexacopper(II) entities are joined further through anti-syn carboxylate groups into an anionic three-dimensional network of formula [Cu(3)(Hmesox)(3)(H(2)O)](n)(3n-) whose charge is neutralized by univalent potassium cations. The strong decrease of the chi(M)T product [per three copper(II) ions] in the high temperature range with the occurrence of a plateau for a spin doublet at T < 65 K is as expected for the coexistence of two antiferromagnetic interactions within the quasi isosceles tricopper(II) core of 1 [J = -194(1) cm(-1) and j = -3(4) cm(-1), the Hamiltonian being defined as H = -J(S(1) x S(2) + S(2) x S(3)) - j(S(1) x S(2))]. Compound 2 exhibits a chiral three-dimensional structure which is made up of an anionic [Co(II)Cu(II)(3)(mu(3)-Cl)(Hmesox)(3)](n)(2n-) framework with a (10,3)-a topology whose cavities are filled by PPh(4)(+) cations. The [Cu(II)(3)(mu(3)-Cl)(Hmesox)(3)](3-) tricopper(II) unit in 2 acts as a tris-bidentate ligand through the Hmesox groups toward three cobalt(II) ions, these latter ones being tris-chelated. Alternating current (ac) and direct current (dc) magnetic susceptibility measurements of 2 show a ferrimagnetic behavior with a magnetic ordering at T(c) = 18.5 K and a coercive field H(c) = 5000 G. As shown by the magneto-structural study of 2, the use as a ligand of 1 versus metal ions other than cobalt(II) or preformed complexes whose coordination

  11. catena-Poly[[[(oxamide dioxime-κ2N,N')copper(II)]-μ-L-tartrato-κ4O1,O2:O3,O4] tetrahydrate]: a chiral nanochannel framework hosting solvent water molecules.

    Science.gov (United States)

    Bélombé, Michel M; Nenwa, Justin; Kouamo, Jean S T Wankap; Ponou, Siméon; Fischer, Andreas

    2012-05-01

    The crystal structure of the title compound, {[Cu(C(4)H(4)O(6))(C(2)H(6)N(4)O(2))]·4H(2)O}(n), contains the central Cu(II) cation in a distorted octahedral coordination, symmetrically chelated by the two imine N atoms of a neutral oxamide dioxime (H(2)oxado) ligand [Cu-N = 1.9829 (16) Å] and unsymmetrically bis-chelated by two halves of the L-(+)-tartrate(2-) (tart) ligands, each half being linked to the Cu(II) cation via the deprotonated carboxylate group and protonated hydroxy group [Cu-O = 1.9356 (14) and 2.4674 (13) Å, respectively]. The extended asymmetric unit is defined by twofold axes, one passing through the Cu(II) cation and the centre of the oxamide dioxime (H(2)oxado) ligand and the another two (symmetry related) bisecting the central C-C bonds of the tartrate ions. The structure is chiral, consisting of enantiomeric linear-chain polymers oriented along [001], with virtual monomeric {Cu(tart(0.5))(2)(H(2)oxado)} repeat units and with the chains interleaved face-to-face into `twin pillars'. Nanochannels exist, running parallel to the c axis and bisecting a and b, which host `double strings' of solvent water molecules. Extensive hydrogen bonding (O-H···O and N-H···O) between the chains and solvent water molecules, together with extended π-σ interactions, consolidate the bulk crystal structure.

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

    Science.gov (United States)

    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.

  13. Nanoconfinement-Induced Structures in Chiral Liquid Crystals

    OpenAIRE

    2013-01-01

    We employ Monte Carlo simulations in a specialized isothermal-isobaric and in the grand canonical ensemble to study structure formation in chiral liquid crystals as a function of molecular chirality. Our model potential consists of a simple Lennard-Jones potential, where the attractive contribution has been modified to represent the orientation dependence of the interaction between a pair of chiral liquid-crystal molecules. The liquid crystal is confined between a pair of planar and atomicall...

  14. Chiral mirrors

    Energy Technology Data Exchange (ETDEWEB)

    Plum, Eric, E-mail: erp@orc.soton.ac.uk [Optoelectronics Research Centre and Centre for Photonic Metamaterials, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Zheludev, Nikolay I., E-mail: niz@orc.soton.ac.uk [Optoelectronics Research Centre and Centre for Photonic Metamaterials, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); The Photonics Institute and Centre for Disruptive Photonic Technologies, Nanyang Technological University, Singapore 637378 (Singapore)

    2015-06-01

    Mirrors are used in telescopes, microscopes, photo cameras, lasers, satellite dishes, and everywhere else, where redirection of electromagnetic radiation is required making them arguably the most important optical component. While conventional isotropic mirrors will reflect linear polarizations without change, the handedness of circularly polarized waves is reversed upon reflection. Here, we demonstrate a type of mirror reflecting one circular polarization without changing its handedness, while absorbing the other. The polarization-preserving mirror consists of a planar metasurface with a subwavelength pattern that cannot be superimposed with its mirror image without being lifted out of its plane, and a conventional mirror spaced by a fraction of the wavelength from the metasurface. Such mirrors enable circularly polarized lasers and Fabry-Pérot cavities with enhanced tunability, gyroscopic applications, polarization-sensitive detectors of electromagnetic waves, and can be used to enhance spectroscopies of chiral media.

  15. Chiral THz metamaterial with tunable optical activity

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Jiangfeng [Los Alamos National Laboratory; Taylor, Antoinette [Los Alamos National Laboratory; O' Hara, John [Los Alamos National Laboratory; Chowdhury, Roy [Los Alamos National Laboratory; Zhao, Rongkuo [IOWA STATE UNIV; Soukoullis, Costas M [IOWA STATE UNIV

    2010-01-01

    Optical activity in chiral metamaterials is demonstrated in simulation and shows actively tunable giant polarization rotation at THz frequencies. Electric current distributions show that pure chirality is achieved by our bi-Iayer chiral metamaterial design. The chirality can be optically controlled by illumination with near-infrared light. Optical activity, occurring in chiral materials such as DNA, sugar and many other bio-molecules, is a phenomenon of great importance to many areas of science including molecular biology, analytical chemistry, optoelectronics and display applications. This phenomenon is well understood at an effective medium level as a magnetic/electric moment excited by the electric/magnetic field of the incident electromagnetic (EM) wave. Usually, natural chiral materials exhibit very weak optical activity e.g. a gyrotropic quartz crystal. The optical activity of chiral metamaterials, however, can be five orders of magnitude stronger. Chiral metamaterials are made of sub-wavelength resonators lacking symmetry planes. The asymmetry allows magnetic moments to be excited by the electric field of the incident EM wave and vice versa. Recently, chiral metamaterials have been demonstrated and lead to prospects in giant optical activity, circular dichroism, negative refraction and reversing the Casmir force. These fascinating optical properties require strong chirality, which may be designed through the microscopic structure of chiral metamaterials. However, these metamaterials have a fixed response function, defined by the geometric structuring, which limits their ability to manipulate EM waves. Active metamaterials realize dynamic control of response functions and have produced many influential applications such as ultra-fast switching devices, frequency and phase modulation and memory devices. Introducing active designs to chiral metamaterials will give additional freedom in controlling the optical activity, and therefore enable dynamic manipulation

  16. From helical to planar chirality by on-surface chemistry.

    Science.gov (United States)

    Stetsovych, Oleksandr; Švec, Martin; Vacek, Jaroslav; Chocholoušová, Jana Vacek; Jančařík, Andrej; Rybáček, Jiří; Kosmider, Krzysztof; Stará, Irena G; Jelínek, Pavel; Starý, Ivo

    2017-03-01

    The chirality of molecular structures is paramount in many phenomena, including enantioselective reactions, molecular self-assembly, biological processes and light or electron-spin polarization. Flat prochiral molecules, which are achiral in the gas phase or solution, can exhibit adsorption-induced chirality when deposited on surfaces. The whole array of such molecular adsorbates is naturally racemic as spontaneous global mirror-symmetry breaking is disfavoured. Here we demonstrate a chemical method of obtaining flat prochiral molecules adsorbed on the solid achiral surface in such a way that a specific adsorbate handedness globally dominates. An optically pure helical precursor is flattened in a cascade of on-surface reactions, which enables chirality transfer. The individual reaction products are identified by high-resolution scanning-probe microscopy. The ultimate formation of globally non-racemic assemblies of flat molecules through stereocontrolled on-surface synthesis allows for chirality to be expressed in as yet unexplored types of organic-inorganic chiral interfaces.

  17. From helical to planar chirality by on-surface chemistry

    Science.gov (United States)

    Stetsovych, Oleksandr; Švec, Martin; Vacek, Jaroslav; Chocholoušová, Jana Vacek; Jančařík, Andrej; Rybáček, Jiří; Kosmider, Krzysztof; Stará, Irena G.; Jelínek, Pavel; Starý, Ivo

    2016-11-01

    The chirality of molecular structures is paramount in many phenomena, including enantioselective reactions, molecular self-assembly, biological processes and light or electron-spin polarization. Flat prochiral molecules, which are achiral in the gas phase or solution, can exhibit adsorption-induced chirality when deposited on surfaces. The whole array of such molecular adsorbates is naturally racemic as spontaneous global mirror-symmetry breaking is disfavoured. Here we demonstrate a chemical method of obtaining flat prochiral molecules adsorbed on the solid achiral surface in such a way that a specific adsorbate handedness globally dominates. An optically pure helical precursor is flattened in a cascade of on-surface reactions, which enables chirality transfer. The individual reaction products are identified by high-resolution scanning-probe microscopy. The ultimate formation of globally non-racemic assemblies of flat molecules through stereocontrolled on-surface synthesis allows for chirality to be expressed in as yet unexplored types of organic-inorganic chiral interfaces.

  18. Chiral conducting polymers.

    Science.gov (United States)

    Kane-Maguire, Leon A P; Wallace, Gordon G

    2010-07-01

    This critical review describes the preparation and properties of a relatively new class of chiral macromolecules, namely chiral conducting polymers. It focuses in particular on examples based on polypyrrole, polythiophene and polyaniline. They possess remarkable properties, combining not only chirality with electrical conductivity but also the ability to undergo facile redox and pH switching. These unique properties have opened up a range of exciting new potential applications, including as chiral sensors, as novel stationary phases for chiral separations, and as chiral electrodes for electrochemical asymmetric synthesis (153 references).

  19. A Molecular Model for Chiral Symmetry Breaking

    Science.gov (United States)

    Latinwo, Folarin; Stillinger, Frank; Debenedetti, Pablo

    In this work, we present a new class of molecular models for chiral phenomena in condensed matter systems. A key feature of these models is the ability of the four-site (tetramer) ``molecules'' to inter-convert between two distinct chiral forms (enantiomers). Given this feature, we use analytical theory and computer simulations to investigate the emergent chiral properties (including symmetry breaking) over a range of conditions. In particular, we consider the single-molecule level and condensed-phase behavior of our model system. Interestingly, we find that our liquid-phase predictions are in excellent agreement with recent experimental reports on chiral self-sorting in isotropic liquids. From this perspective, our model demonstrates accurate predictive capabilities, as well as a platform for understanding the microscopic origins of a variety of chiral phenomena. In a broader context, we anticipate that this class of models will be relevant to chirality-dominated areas such as the pharmaceutical industry and pre-biotic geochemistry.

  20. Single beam optical conveyor belt for chiral particles

    CERN Document Server

    Fernandes, David E

    2016-01-01

    We propose a novel paradigm to selectively manipulate and transport small engineered chiral particles and discriminate different enantiomers using unstructured chiral light. It is theoretically shown that the response of a chiral metamaterial particle may be tailored to enable an optical conveyor belt operation with no optical traps, such that for a fixed incident light helicity and independent of the nanoparticle location, it is either steadily pushed towards the direction of the photon flow or steadily pulled against the photon flow. Our findings create new opportunities for unconventional optical manipulations of tailored nanoparticles and may have applications in sorting racemic mixtures of artificial chiral molecules and in particle delivery.

  1. Chiral Recognition for the Two Enantiomers of Phenylalanine and Four Amino Acid Derivatives with (S)-Phenylethylamine Derived Nickel(II) Macrocyclic Complex

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Jeong Jae; Ryoo, Jae Jeong [Kyungpook National Univ., Daegu (Korea, Republic of)

    2013-11-15

    The potency of new chiral selector candidate was assessed by this simple chiral discrimination test. This experiment showed that the macrocyclic molecule can be a powerful candidate as a chiral selector to obtain optically pure amino acid or amino acid derivatives, particularly phenylalanine and N-benzoyl-phenylalanine enantiomers from racemic mixtures. This study attempted to use the chiral metal organic framework (MOF), 1, as a good chiral selector candidate for the chiral discrimination of racemic phenylalanine, N-benzoyl-alanine, N-benzoyl-phenylalanine, N-benzoyl-methionine, N-CBZ-alanine. The chiral recognition ability of the chiral macromolecule, was examined by varying the molar ratio of the macromolecule and racemates.

  2. Chirality and drugs in clinical practice and its ethical aspect.

    Science.gov (United States)

    Banerjee, Molly; Biswas, Indranil; Halder, Swaraj

    2009-01-01

    Recently specific enantiomer of different chiral molecules are being launched in the market as drugs. Here the rationality of scopes and uses of these drugs in therapeutic medicine is discussed including the ethical aspect.

  3. Chirality Amplification in Tactoids of Lyotropic Chromonic Liquid Crystals

    Science.gov (United States)

    Peng, Chenhui; Lavrentovich, Oleg

    2014-03-01

    We demonstrate an effective chirality amplification based on the long-range forces, extending over the scales of tens of micrometers, much larger than the single molecule (nanometer) scale. The mechanism is rooted in the long-range elastic nature of orientational order in lyotropic chromonic liquid crystals (LCLCs) that represent water solutions of achiral disc-like molecules. Minute quantities of chiral molecules such as amino acid L-alanine and limonene added to the droplets of LCLC lead to chiral amplification characterized by an increase of optical activity by a factor of 103 - 104. This effect allows one to discriminate and detect the absolute configuration of chiral molecules in an aqueous system, thus opening new possibilities in biosensing and other biological applications.

  4. Supernovae and the Chirality of the Amino Acids

    CERN Document Server

    Boyd, R N; Onaka, T

    2010-01-01

    A mechanism for creating amino acid enantiomerism that always selects the same global chirality is identified, and subsequent chemical replication and galactic mixing that would populate the galaxy with the predominant species is described. This involves: (1) the spin of the 14N in the amino acids, or in precursor molecules from which amino acids might be formed, coupling to the chirality of the molecules; 2) the neutrinos emitted from the supernova, together with magnetic field from the nascent neutron star or black hole formed from the supernova selectively destroying one orientation of the 14N, and thus selecting the chirality associated with the other 14N orientation; (3) chemical evolution, by which the molecules replicate and evolve to more complex forms of a single chirality on a relatively short timescale; and (4) galactic mixing on a longer timescale mixing the selected molecules throughout the galaxy.

  5. Supramolecular Chirality: Solvent Chirality Transfer in Molecular Chemistry and Polymer Chemistry

    Directory of Open Access Journals (Sweden)

    Michiya Fujiki

    2014-08-01

    Full Text Available Controlled mirror symmetry breaking arising from chemical and physical origin is currently one of the hottest issues in the field of supramolecular chirality. The dynamic twisting abilities of solvent molecules are often ignored and unknown, although the targeted molecules and polymers in a fluid solution are surrounded by solvent molecules. We should pay more attention to the facts that mostly all of the chemical and physical properties of these molecules and polymers in the ground and photoexcited states are significantly influenced by the surrounding solvent molecules with much conformational freedom through non-covalent supramolecular interactions between these substances and solvent molecules. This review highlights a series of studies that include: (i historical background, covering chiral NaClO3 crystallization in the presence of d-sugars in the late 19th century; (ii early solvent chirality effects for optically inactive chromophores/fluorophores in the 1960s–1980s; and (iii the recent development of mirror symmetry breaking from the corresponding achiral or optically inactive molecules and polymers with the help of molecular chirality as the solvent use quantity.

  6. Supramolecular tilt chirality in crystals of steroids and alkaloids.

    Science.gov (United States)

    Hisaki, Ichiro; Tohnai, Norimitsu; Miyata, Mikiji

    2008-03-01

    The concept of supramolecular chirality has assumed increasing importance in association with the development of supramolecular chemistry over the last two decades. In chiral crystals, 2 1 helical molecular assemblies are frequently observed as key motifs. Helical handedness of the 2 1 assemblies, however, has not been determined from the mathematical or crystallographical viewpoints. In this context, we have proposed two new concepts, three-axial chirality and tilt chirality. On the basis of the concepts, we describe supramolecular chirality and determine the handedness of 2 1 assemblies that are composed of relatively complicated molecules with multiple stereogenic centers such as brucine, bile acids, and cinchona alkaloids as well as those of simple molecules.

  7. Chiral organic glass and its infrared spectrum property

    Institute of Scientific and Technical Information of China (English)

    陶卫东; 夏海平; 董建峰; 白贵儒; 聂秋华; 陆祖康

    2003-01-01

    Chiral molecules griseofulvin were disseminated homogeneously in poly methyl metahcrylate (PMMA) host, which agglomerate from methyl metahcrylate and N, N-dimethyl formamide dimethyl acetal, using benzoyl peroxide as a catalyst. So the chiral organic glass has been manufactured successfully. Its optical rotatory were investigated from a solution state to a solid state. The results of measurement show that the chiral parameter of the chiral organic glass is 2.65×10-7 and its specific rotation has increased compared with its solution condition. Its infrared spectra property has been measured by Fourier transformation infrared spectrometer. The results show that the chiral molecules fill in the pore of the network structure in the organic glass, which hardly link with the host.

  8. Baryons and Chiral Symmetry

    CERN Document Server

    Liu, Keh-Fei

    2016-01-01

    The relevance of chiral symmetry in baryons is highlighted in three examples in the nucleon spectroscopy and structure. The first one is the importance of chiral dynamics in understanding the Roper resonance. The second one is the role of chiral symmetry in the lattice calculation of $\\pi N \\sigma$ term and strangeness. The third one is the role of chiral $U(1)$ anomaly in the anomalous Ward identity in evaluating the quark spin and the quark orbital angular momentum. Finally, the chiral effective theory for baryons is discussed.

  9. Spontaneous transmission of chirality through multiple length scales.

    Science.gov (United States)

    Iski, Erin V; Tierney, Heather L; Jewell, April D; Sykes, E Charles H

    2011-06-20

    The hierarchical transfer of chirality in nature, from the nano-, to meso-, to macroscopic length scales, is very complex, and as of yet, not well understood. The advent of scanning probes has allowed chirality to be monitored at the single molecule or monolayer level and has opened up the possibility to track enantiospecific interactions and chiral self-assembly with molecular-scale detail. This paper describes the self-assembly of a simple, model molecule (naphtho[2,3-a]pyrene) that is achiral in the gas phase, but becomes chiral when adsorbed on a surface. This polyaromatic hydrocarbon forms a stable and reversibly ordered system on Cu(111) in which the transmission of chirality from single surface-bound molecules to complex 2D chiral architectures can be monitored as a function of molecular packing density and surface temperature. In addition to the point chirality of the surface-bound molecule, the unit cell of the molecular domains was also found to be chiral due to the incommensurate alignment of the molecular rows with respect to the underlying metal lattice. These molecular domains always aggregated in groups of three, all of the same chirality, but with different rotational orientations, forming homochiral "tri-lobe" ensembles. At a larger length scale, these tri-lobe ensembles associated with nearest-neighbor tri-lobe units of opposite chirality at lower packing densities before forming an extended array of homochiral tri-lobe ensembles at higher converges. This system displayed chirality at a variety of size scales from the molecular (≈1 nm) and domain (≈5 nm) to the tri-lobe ensemble (≈10 nm) and extended array (>25 nm) levels. The chirality of the tri-lobe ensembles dictated how the overall surface packing occurred and both homo- and heterochiral arrays could be reproducibly and reversibly formed and interchanged as a function of surface coverage. Finally, these chirally templated surfaces displayed remarkable enantiospecificity for

  10. On chiral and non chiral 1D supermultiplets

    Energy Technology Data Exchange (ETDEWEB)

    Toppan, Francesco, E-mail: toppan@cbpf.b [Centro Brasileiro de Pesquisas Fisicas (TEO/CBPF), Rio de Janeiro, RJ (Brazil). Coordenacao de Fisica Teorica

    2011-07-01

    In this talk I discuss and clarify some issues concerning chiral and non chiral properties of the one-dimensional supermultiplets of the N-extended supersymmetry. Quaternionic chirality can be defined for N = 4, 5, 6, 7, 8. Octonionic chirality for N = 8 and beyond. Inequivalent chiralities only arise when considering several copies of N = 4 or N = 8 supermultiplets. (author)

  11. Chiral symmetry and chiral-symmetry breaking

    Energy Technology Data Exchange (ETDEWEB)

    Peskin, M.E.

    1982-12-01

    These lectures concern the dynamics of fermions in strong interaction with gauge fields. Systems of fermions coupled by gauge forces have a very rich structure of global symmetries, which are called chiral symmetries. These lectures will focus on the realization of chiral symmetries and the causes and consequences of thier spontaneous breaking. A brief introduction to the basic formalism and concepts of chiral symmetry breaking is given, then some explicit calculations of chiral symmetry breaking in gauge theories are given, treating first parity-invariant and then chiral models. These calculations are meant to be illustrative rather than accurate; they make use of unjustified mathematical approximations which serve to make the physics more clear. Some formal constraints on chiral symmetry breaking are discussed which illuminate and extend the results of our more explicit analysis. Finally, a brief review of the phenomenological theory of chiral symmetry breaking is presented, and some applications of this theory to problems in weak-interaction physics are discussed. (WHK)

  12. Stern-Gerlach effect goes chiral

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ Prof. SUN Changpu from the CAS Institute of Theoretical Physics and coworkers from University of Basel in Switzerland have worked out a way - at least in theory - to split a beam of molecules according to their chirality. The technique involves passing the molecules through three different laser beams and is similar to the famous Stern-Gerlach effect, whereby a beam of atoms passing through a magnetic field is split in two according to the atoms' spin states (Phys. Rev. Lett. 99 130403).

  13. High Resolution GHZ and Thz (ftir) Spectroscopy and Theory of Parity Violation and Tunneling for 1,2-DITHIINE (C4H4S2) as a Candidate for Measuring the Parity Violating Energy Difference Between Enantiomers of Chiral Molecules

    Science.gov (United States)

    Albert, Sieghard; Bolotova, Irina; Chen, Ziqiu; Fábri, Csaba; Horny, Lubos; Quack, Martin; Seyfang, Georg; Zindel, Daniel

    2016-06-01

    We report high resolution spectroscopic results for 1,2-dithiine-(1,2-dithia-3,5-cyclohexadiene,C4H4S2) in the Gigahertz and Terahertz spectroscopic ranges and exploratory theoretical calculations of parity violation and tunneling processes in view of a possible experimental determination of the parity violating energy difference ΔpvE in this chiral molecule. Theory predicts that the parity violating energy difference in the ground state (ΔpvE≃11x10-11(hc) wn)is in principle measurable as it is much larger than the calculated tunneling splitting for the symmetrical potential Δ±E≃10-24(hc) wn. With a planar transition state for stereomutation at about 2500 wn tunneling splittings become appreciable above 2300 wn. This makes levels of well defined parity accessible to parity selection by available powerful infrared lasers and thus useful for one of the existing experimental approaches towards molecular parity violation. The new GHz spectra lead to greatly improved ground state rotational parameters for 1,2-dithiine. These are used as starting point for the first successful analyses of high resolution interferometric Fourier Transform Infrared (FTIR, THz) spectra for the fundamentals ν17 (1308.873 wn or 39.23903 THz), ν22 (623.094 wn or 18.67989 THz) and ν3 (1544.900 wn or 46.314937 THz) for which highly accurate spectroscopic parameters are reported. The results are discussed in relation to current efforts to measure ΔpvE.a-. M. Quack , Fundamental Symmetries and Symmetry Violations from High-resolution Spectroscopy, Handbook of High Resolution Spectroscopy, M. Quack and F. Merkt eds.,John Wiley & Sons Ltd, Chichester, New York, 2001, vol. 1, ch. 18, pp. 659-722 S. Albert, I. Bolotova, Z. Chen, C. Fábri, L. Horny, M. Quack, G. Seyfang and D. Zindel,Proceedings of the 20th Symposium on Atomic, Cluster and Surface Physics (SASP 2016), Innsbruck University Press, 2016, pp. 127-130, ISBN:978-3-903122-04-8. and to be published P. Dietiker, E. Miloglyadov, M

  14. Chirality and anaesthetic drugs: A review and an update.

    Science.gov (United States)

    Mitra, Sukanya; Chopra, Puneet

    2011-11-01

    Many molecules can exist as right-handed and left-handed forms that are non-superimposable mirror images of each other. They are known as enantiomers or substances of opposite shape. Such compounds are also said to be chiral (Greek chiros meaning 'hand'). Such chiral molecules are of great relevance to anaesthetic theory and practice. This review summarizes the basic concepts, pharmacokinetic and pharmacodynamic aspects of chirality, and some specific examples of their application in anaesthesia, along with recent advances to elucidate the anaesthetic mechanisms. Chirality is relevant to anaesthesia, simply because more than half of the synthetic agents used in anaesthesia practice are chiral drugs. Almost all these synthetic chiral drugs are administered as racemic mixture, rather than as single pure enantiomers. These mixtures are not drug formulations containing two or more therapeutic substances, but combination of isomeric substances, with the therapeutic activity residing mainly in one of the enantiomer. The other enantiomer can have undesirable properties, have different therapeutic activities or be pharmacologically inert. Specific examples of application of chirality in anaesthetic drugs include inhalational general anaesthetics (e.g. isoflurane), intravenous anaesthetics (e.g. etomidate, thiopentone), neuromuscular blocking agents (e.g. cisatracurium), local anaesthetics (e.g. ropivacaine and levobupivacaine) and other agents (e.g. levosimendan, dexmedetomidine, L-cysteine). In the recent advances, chirality study has not only helped new drug development as mentioned above, but has also contributed in a more profound way to the understanding of the mechanism of anaesthesia and anaesthetic drugs.

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

    Science.gov (United States)

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

    2013-12-14

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

  16. Chirality study inside biological tissue by second harmonic generation circular dichroism

    Science.gov (United States)

    Hsu, Kuo-Jen; Lee, Hsuan; Zhuo, Guan-Yu; Chao, Pen-Hsiu; Chu, Shi-Wei

    2013-02-01

    Many biological systems are composed of chiral molecules and their functions depend strongly on their chirality. For example, most amino acids are of left-handed chirality while most polysaccharides are of right-handed chirality. Both of them are vital for human life, so it is important to perform chiral detection inside bio-tissues. Here we demonstrated second harmonic generation circular dichroism (SHG-CD) as a novel chiral imaging contrast in thick biotissue. Compared with conventional chiral detection, SHG-CD provides at least three orders higher contrast. In addition, due to the nonlinear nature of SHG, this technique provides optical sectioning capability, so the axial contrast is much better. The advantages of nonlinear optical microscopy are optical sectioning and deep penetration capabilities. The SHG-CD achieved 100% signal contrast with sub-micrometer spatial resolution. This method is expected to offer a novel contrast mechanism of imaging chirality inside complex bio-tissues.

  17. Chirality effects on 2D phase transitions

    DEFF Research Database (Denmark)

    Scalas, E.; Brezesinski, G.; Möhwald, H.

    1996-01-01

    -nearest neighbours (NNN) and an NNN-distorted lattice is observed. At 5 degrees C, the transition pressure is 15 mN m(-1), whereas at 20 degrees C it is 18 mN m(-1). Chirality destroys this transition: the pure enantiomer always exhibits an oblique lattice with tilted molecules, and the azimuths of tilt...... and distortion continuously vary from a direction close to NN to a direction close to NNN. The nature of the phase transition and the influence of chirality on it are discussed within the framework of Landau's theory of phase transitions....

  18. Discrete nanocubes as plasmonic reporters of molecular chirality.

    Science.gov (United States)

    Lu, Fang; Tian, Ye; Liu, Mingzhao; Su, Dong; Zhang, Hui; Govorov, Alexander O; Gang, Oleg

    2013-07-10

    One of the most intriguing structural properties, chirality, is often exhibited by organic and bio-organic molecular constructs. Chiral spectral signatures, typically appearing in the UV range for organic materials and known as circular dichroism (CD), are widely used to probe a molecular stereometry. Such probing has an increasingly broad importance for biomedical and pharmacological fields due to synthesis/separation/detection of homochiral species, biological role of chiral organization, and structural response to environmental conditions and enantiomeric drugs. Recent theoretical and experimental works demonstrated that the CD signal from chiral organic molecules could appear in the plasmonic (typically, visible) band when they coupled with plasmonic particles. However, the magnitude of this CD signal, induced by discrete nonchiral plasmonic particles, and its native molecular analog were found to be comparable. Here we show that shaped nonchiral nanoparticles, namely, gold/silver core/shell nanocubes, can act as plasmonic reporters of chirality for attached molecules by providing a giant, 2 orders of magnitude CD enhancement in a near-visible region. Through the experimental and theoretical comparison with nanoparticles of other shapes and materials, we demonstrate a uniqueness of silver nanocube geometry for the CD enhancement. The discovered phenomenon opens novel opportunities in ultrasensitive probing of chiral molecules and for novel optical nanomaterials based on the chiral elements.

  19. Molecular-Level Design of Heterogeneous Chiral Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    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 forming naturally chiral surfaces using imprinting chiral agents. Individually, the members of our team are leaders in these various aspects of chiral catalysis, but the present program provides the vehicle to generate and exploit the synergies necessary to address the problem in a comprehensive manner. Our initial work has advanced the methodology needed for these studies, including an enantioselective titration procedure to identify surface chiral sites, infrared spectroscopy in situ at the interface between gases or liquids and solids to mimic realistic catalytic conditions, and DFT and Monte Carlo algorithms to simulate and understand chirality on surfaces. The next step, to be funded by the monies requested in this proposal, is to apply those methods to specific problems in chiral catalysis, including the identification of the requirements for the formation of supramolecular surface structures with enantioselective behavior, the search for better molecules to probe the chiral nature of the modified surfaces, the exploration of the transition from supramolecular to one-to-one chiral modification, the correlation of the adsorption characteristics of one-to-one chiral modifiers with their physical properties, in particular with their configuration

  20. Chiral Superfluidity for QCD

    CERN Document Server

    Kalaydzhyan, Tigran

    2014-01-01

    We argue that the strongly coupled quark-gluon plasma formed at LHC and RHIC can be considered as a chiral superfluid. The "normal" component of the fluid is the thermalized matter in common sense, while the "superfluid" part consists of long wavelength (chiral) fermionic states moving independently. We use the bosonization procedure with a finite cut-off and obtain a dynamical axion-like field out of the chiral fermionic modes. Then we use relativistic hydrodynamics for macroscopic description of the effective theory obtained after the bosonization. Finally, solving the hydrodynamic equations in gradient expansion, we find that in the presence of external electromagnetic fields or rotation the motion of the "superfluid" component gives rise to the chiral magnetic, chiral vortical, chiral electric and dipole wave effects. Latter two effects are specific for a two-component fluid, which provides us with crucial experimental tests of the model.

  1. Emerging chirality in nanoscience.

    Science.gov (United States)

    Wang, Yong; Xu, Jun; Wang, Yawen; Chen, Hongyu

    2013-04-07

    Chirality in nanoscience may offer new opportunities for applications beyond the traditional fields of chirality, such as the asymmetric catalysts in the molecular world and the chiral propellers in the macroscopic world. In the last two decades, there has been an amazing array of chiral nanostructures reported in the literature. This review aims to explore and categorize the common mechanisms underlying these systems. We start by analyzing the origin of chirality in simple systems such as the helical spring and hair vortex. Then, the chiral nanostructures in the literature were categorized according to their material composition and underlying mechanism. Special attention is paid to highlight systems with original discoveries, exceptional structural characteristics, or unique mechanisms.

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

    Science.gov (United States)

    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'.

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

    Science.gov (United States)

    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

  4. Quantitatively analyzing intrinsic plasmonic chirality by tracking the interplay of electric and magnetic dipole modes

    CERN Document Server

    Hu, Li; Fang, Yurui

    2016-01-01

    Plasmonic chirality exhibits great potential for novel nanooptical devices due to the generation of a strong chiroptical response. Previous reports on plasmonic chirality explanations are mainly based on phase retardation and coupling. We propose a quantitative model similar to the chiral molecules for explaining the mechanism of the intrinsic plasmonic chirality quantitatively based on the interplay and mixing of electric and magnetic dipole modes, which forms a mixed electric and magnetic polarizability. The analysis method is also suitable for small chiral object down to quasi-static limit without phase delay and expected to be a universal rule.

  5. Peptide Deravatives as New Chiral Ligands for Enantioselective Phenylacetylene Addition to Aldehydes

    Institute of Scientific and Technical Information of China (English)

    ZHOU,Yi-Feng; GAO,Yan-Feng; KANG,Yong-Feng; HAN,Zhi-Jian; YAN,Wen-Jin; NI,Ming; WANG,Rui

    2004-01-01

    @@ The asymmetric addition of alkynylzinc to aldehydes is an important method of synthesizing chiral propargyl alcohols, which are important precursors to many chiral organic compounds. Recently, many significant chiral ligands in this area have been disclosed.[1] Use of a short peptide as a catalyst would allow expansion beyond the (still uncharted) repertoire of single amino acids, while conserving the advantages of a small molecule catalyst. To the best of our knowledge,no results of peptide derivatives as chiral ligands in this reaction has been disclosed to date.[2] Herein, we report the initial results of peptide derivatives, which have been used directly as a chiral ligand in this reaction (Scheme 1).

  6. Chiral atomically thin films

    Science.gov (United States)

    Kim, Cheol-Joo; Sánchez-Castillo, A.; Ziegler, Zack; Ogawa, Yui; Noguez, Cecilia; Park, Jiwoong

    2016-06-01

    Chiral materials possess left- and right-handed counterparts linked by mirror symmetry. These materials are useful for advanced applications in polarization optics, stereochemistry and spintronics. In particular, the realization of spatially uniform chiral films with atomic-scale control of their handedness could provide a powerful means for developing nanodevices with novel chiral properties. However, previous approaches based on natural or grown films, or arrays of fabricated building blocks, could not offer a direct means to program intrinsic chiral properties of the film on the atomic scale. Here, we report a chiral stacking approach, where two-dimensional materials are positioned layer-by-layer with precise control of the interlayer rotation (θ) and polarity, resulting in tunable chiral properties of the final stack. Using this method, we produce left- and right-handed bilayer graphene, that is, a two-atom-thick chiral film. The film displays one of the highest intrinsic ellipticity values (6.5 deg μm-1) ever reported, and a remarkably strong circular dichroism (CD) with the peak energy and sign tuned by θ and polarity. We show that these chiral properties originate from the large in-plane magnetic moment associated with the interlayer optical transition. Furthermore, we show that we can program the chiral properties of atomically thin films layer-by-layer by producing three-layer graphene films with structurally controlled CD spectra.

  7. Chiral Shock Waves

    CERN Document Server

    Sen, Srimoyee

    2016-01-01

    We study shock waves in relativistic chiral matter. We argue that the conventional Rankine- Hugoinot relations are modified due to the presence of chiral transport phenomena. We show that the entropy discontinuity in a weak shock wave is linearly proportional to the pressure discontinuity when the effect of chiral transport becomes sufficiently large. We also show that rarefaction shock waves, which do not exist in usual nonchiral fluids, can appear in chiral matter. These features are exemplified by shock propagation in dense neutrino matter in the hydrodynamic regime.

  8. Anomalous chiral superfluidity

    Energy Technology Data Exchange (ETDEWEB)

    Lublinsky, Michael, E-mail: lublinsky@phys.uconn.ed [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794 (United States); Physics Department, Ben-Gurion University, Beer Sheva 84105 (Israel); Zahed, Ismail [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794 (United States)

    2010-02-08

    We discuss both the anomalous Cartan currents and the energy-momentum tensor in a left chiral theory with flavor anomalies as an effective theory for flavored chiral phonons in a chiral superfluid with the gauged Wess-Zumino-Witten term. In the mean-field (leading tadpole) approximation the anomalous Cartan currents and the energy-momentum tensor take the form of constitutive currents in the chiral superfluid state. The pertinence of higher order corrections and the Adler-Bardeen theorem is briefly noted.

  9. Doped Chiral Polymer Metamaterials Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Doped Chiral Polymer Metamaterials (DCPM) with tunable resonance frequencies have been developed by adding plasmonic inclusions into chiral polymers with variable...

  10. Heavy Exotic Molecules

    CERN Document Server

    Liu, Yizhuang

    2016-01-01

    We briefly review the formation of pion-mediated heavy-light exotic molecules with both charm and bottom, under the general strictures of chiral and heavy quark symmetries. The charm isosinglet exotic molecules with $J^{PC}=1^{++}$ binds, which we identify as the reported neutral $X(3872)$. The bottom isotriplet exotic with $J^{PC}=1^{+-}$ binds, and is identified as a mixed state of the reported charged exotics $Z^+_b(10610)$ and $Z^+_b(10650)$. The bound bottom isosinglet molecule with $J^{PC}=1^{++}$ is a possible neutral $X_b(10532)$ to be observed.

  11. Molecular-level Design of Heterogeneous Chiral Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Gellman, Andrew John [Carnegie Mellon University; Sholl, David S. [Georgia Institute of Technology; Tysoe, Wilfred T. [University of Wisconsin - Milwaukee; Zaera, Francisco [University of California at Riverside

    2013-04-28

    Understanding and controlling selectivity is one of the key challenges in heterogeneous catalysis. Among problems in catalytic selectivity enantioselectivity is perhaps the most the most challenging. The primary goal of the project on “Molecular-level Design of Heterogeneous Chiral Catalysts” is to understand the origins of enantioselectivity on chiral heterogeneous surfaces and catalysts. The efforts of the project team include preparation of chiral surfaces, characterization of chiral surfaces, experimental detection of enantioselectivity on such surfaces and computational modeling of the interactions of chiral probe molecules with chiral surfaces. Over the course of the project period the team of PI’s has made some of the most detailed and insightful studies of enantioselective chemistry on chiral surfaces. This includes the measurement of fundamental interactions and reaction mechanisms of chiral molecules on chiral surfaces and leads all the way to rationale design and synthesis of chiral surfaces and materials for enantioselective surface chemistry. The PI’s have designed and prepared new materials for enantioselective adsorption and catalysis. Naturally Chiral Surfaces • Completion of a systematic study of the enantiospecific desorption kinetics of R-3-methylcyclohexanone (R-3-MCHO) on 9 achiral and 7 enantiomeric pairs of chiral Cu surfaces with orientations that span the stereographic triangle. • Discovery of super-enantioselective tartaric acid (TA) and aspartic acid (Asp) decomposition as a result of a surface explosion mechanism on Cu(643)R&S. Systematic study of super-enantiospecific TA and Asp decomposition on five enantiomeric pairs of chiral Cu surfaces. • Initial observation of the enantiospecific desorption of R- and S-propylene oxide (PO) from Cu(100) imprinted with {3,1,17} facets by L-lysine adsorption. Templated Chiral Surfaces • Initial observation of the enantiospecific desorption of R- and S-PO from Pt(111) and Pd(111

  12. Binary mixtures of chiral gases

    CERN Document Server

    Presilla, Carlo

    2015-01-01

    A possible solution of the well known paradox of chiral molecules is based on the idea of spontaneous symmetry breaking. At low pressure the molecules are delocalized between the two minima of a given molecular potential while at higher pressure they become localized in one minimum due to the intermolecular dipole-dipole interactions. Evidence for such a phase transition is provided by measurements of the inversion spectrum of ammonia and deuterated ammonia at different pressures. In particular, at pressure greater than a critical value no inversion line is observed. These data are well accounted for by a model previously developed and recently extended to mixtures. In the present paper, we discuss the variation of the critical pressure in binary mixtures as a function of the fractions of the constituents.

  13. Applications of chiral symmetry

    CERN Document Server

    Pisarski, R D

    1995-01-01

    I discuss several topics in the applications of chiral symmetry at nonzero temperature, including: where the rho goes, disoriented chiral condensates, and the phase diagram for QCD with 2+1 flavors. (Based upon talks presented at the "Workshop on Finite Temperature QCD", Wuhan, P.R.C., April, 1994.)

  14. Can the chirality of the ISM be measured

    Science.gov (United States)

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

    1990-04-01

    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.

  15. Can the chirality of the ISM be measured

    Science.gov (United States)

    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.

  16. The significance of chirality in drug design and development.

    Science.gov (United States)

    Brooks, W H; Guida, W C; Daniel, K G

    2011-01-01

    Proteins are often enantioselective towards their binding partners. When designing small molecules to interact with these targets, one should consider stereoselectivity. As considerations for exploring structure space evolve, chirality is increasingly important. Binding affinity for a chiral drug can differ for diastereomers and between enantiomers. For the virtual screening and computational design stage of drug development, this problem can be compounded by incomplete stereochemical information in structure libraries leading to a "coin toss" as to whether or not the "ideal" chiral structure is present. Creating every stereoisomer for each chiral compound in a structure library leads to an exponential increase in the number of structures resulting in potentially unmanageable file sizes and screening times. Therefore, only key chiral structures, enantiomeric pairs based on relative stereochemistry need be included, and lead to a compromise between exploration of chemical space and maintaining manageable libraries. In clinical environments, enantiomers of chiral drugs can have reduced, no, or even deleterious effects. This underscores the need to avoid mixtures of compounds and focus on chiral synthesis. Governmental regulations emphasizing the need to monitor chirality in drug development have increased. The United States Food and Drug Administration issued guidelines and policies in 1992 concerning the development of chiral compounds. These guidelines require that absolute stereochemistry be known for compounds with chiral centers and that this information should be established early in drug development in order that the analysis can be considered valid. From exploration of structure space to governmental regulations it is clear that the question of chirality in drug design is of vital importance.

  17. A VCD robust mode analysis of induced chirality: the case of pulegone in chloroform.

    Science.gov (United States)

    Nicu, Valentin Paul; Debie, Elke; Herrebout, Wouter; Van der Veken, Benjamin; Bultinck, Patrick; Baerends, Evert Jan

    2009-01-01

    Vibrational modes in an achiral molecule may acquire rotational strength by complexation to a chiral molecule, as happens for achiral solvent molecules complexed to a chiral solute. We investigate this transfer of chirality in vibrational circular dichroism for the pulegone molecule in CDCl(3) solvent from the point of view of the robustness concept introduced recently. It turns out that the transfer of chirality yields nonrobust modes, which means that, although they are observed in vibrational circular dichroism (VCD) experiments, the sign of these modes cannot be predicted reliably with standard (Density Functional Theory) VCD calculations. This limits the usefulness of the induced chirality phenomenon for obtaining information on the intermolecular interactions that give rise to it.

  18. Design and synthesis of quasi-diastereomeric molecules with unchanging central, regenerating axial and switchable helical chirality via cleavage and formation of Ni(II–O and Ni(II–N coordination bonds

    Directory of Open Access Journals (Sweden)

    Vadim A. Soloshonok

    2012-11-01

    Full Text Available We describe herein the design and synthesis of asymmetric, pentadentate ligands, which are able to coordinate to Ni(II cations leading to quasi-diastereomeric complexes displaying two new elements of chirality: stereogenic axis and helix along with configurational stabilization of the stereogenic center on the nitrogen. Due to the stereocongested structural characteristics of the corresponding Ni(II complexes, the formation of quasi-diastereomeric products is highly stereoselective providing formation of only two, (Ra*,Mh*,Rc* and (Ra*,Ph*,Rc*, out of the four possible stereochemical combinations. The reversible quasi-diastereomeric transformation between the products (Ra*,Mh*,Rc* and (Ra*,Ph*,Rc* occurs by intramolecular trans-coordination of Ni–NH and Ni–O bonds providing a basis for a chiral switch model.

  19. Enantiospecific adsorption of cysteine on a chiral Au34 cluster

    Science.gov (United States)

    Pelayo, José de Jesús; Valencia, Israel; Díaz, Gabriela; López-Lozano, Xóchitl; Garzón, Ignacio L.

    2015-12-01

    The interaction of biological molecules like chiral amino acids with chiral metal clusters is becoming an interesting and active field of research because of its potential impact in, for example, chiral molecular recognition phenomena. In particular, the enantiospecific adsorption (EA) of cysteine (Cys) on a chiral Au55 cluster was theoretically predicted a few years ago. In this work, we present theoretical results, based on density functional theory, of the EA of non-zwitterionic cysteine interacting with the C3-Au34 chiral cluster, which has been experimentally detected in gas phase, using trapped ion electron diffraction. Our results show that, indeed, the adsorption energy of the amino acid depends on which enantiomers participate in the formation Cys-Au34 chiral complex. EA was obtained in the adsorption modes where both the thiol, and the thiol-amino functional groups of Cys are adsorbed on low-coordinated sites of the metal cluster surface. Similarly to what was obtained for the Cys-Au55 chiral complex, in the present work, it is found that the EA is originated from the different strength and location of the bond between the COOH functional group and surface Au atoms of the Au34 chiral cluster. Calculations of the vibrational spectrum for the different Cys-Au34 diastereomeric complexes predict the existence of a vibro-enantiospecific effect, indicating that the vibrational frequencies of the adsorbed amino acid depend on its handedness.

  20. Applications of chiral symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Pisarski, R.D.

    1995-03-01

    The author discusses several topics in the applications of chiral symmetry at nonzero temperature. First, where does the rho go? The answer: up. The restoration of chiral symmetry at a temperature T{sub {chi}} implies that the {rho} and a{sub 1} vector mesons are degenerate in mass. In a gauged linear sigma model the {rho} mass increases with temperature, m{sub {rho}}(T{sub {chi}}) > m{sub {rho}}(0). The author conjectures that at T{sub {chi}} the thermal {rho} - a{sub 1}, peak is relatively high, at about {approximately}1 GeV, with a width approximately that at zero temperature (up to standard kinematic factors). The {omega} meson also increases in mass, nearly degenerate with the {rho}, but its width grows dramatically with temperature, increasing to at least {approximately}100 MeV by T{sub {chi}}. The author also stresses how utterly remarkable the principle of vector meson dominance is, when viewed from the modern perspective of the renormalization group. Secondly, he discusses the possible appearance of disoriented chiral condensates from {open_quotes}quenched{close_quotes} heavy ion collisions. It appears difficult to obtain large domains of disoriented chiral condensates in the standard two flavor model. This leads to the last topic, which is the phase diagram for QCD with three flavors, and its proximity to the chiral critical point. QCD may be very near this chiral critical point, and one might thereby generated large domains of disoriented chiral condensates.

  1. Chiral discrimination in biomimetic systems: Phenylalanine

    Indian Academy of Sciences (India)

    K Thirumoorthy; K Soni; T Arun; N Nandi

    2007-09-01

    Chiral discrimination and recognition is important in peptide biosynthesis, amino acid synthesis and drug designing. Detailed structural information is available about the peptide synthesis in ribosome. However, no detailed study is available about the discrimination in peptide synthesis. We study the conformational energy variation of neutral methoxy phenyl alanine molecule as a function of its different dihedral angle to locate the minimum energy conformation using quantum chemical theory. We compared the intermolecular energy surfaces of phenyl alanine molecule in its neutral and zwitterionic state using quantum chemical theory as a function of distance and mutual orientation. The energy surfaces are studied with rigid geometry by varying the distance and orientation. The potential energy surfaces of - and - pairs are found to be dissimilar and reflect the underlying chirality of the homochiral pair and racemic nature of the heterochiral pair. The intermolecular energy surface of homochiral pair is more favourable than the corresponding energy surface of heterochiral pair.

  2. Spectral signatures of chirality

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Mortensen, Asger

    2009-01-01

    We present a new way of measuring chirality, via the spectral shift of photonic band gaps in one-dimensional structures. We derive an explicit mapping of the problem of oblique incidence of circularly polarized light on a chiral one-dimensional photonic crystal with negligible index contrast...... to the formally equivalent problem of linearly polarized light incident on-axis on a non-chiral structure with index contrast. We derive analytical expressions for the first-order shifts of the band gaps for negligible index contrast. These are modified to give good approximations to the band gap shifts also...

  3. Chiral supergravity and anomalies

    CERN Document Server

    Mielke, E W; Macias, Alfredo; Mielke, Eckehard W.

    1999-01-01

    Similarily as in the Ashtekar approach, the translational Chern-Simons term is, as a generating function, instrumental for a chiral reformulation of simple (N=1) supergravity. After applying the algebraic Cartan relation between spin and torsion, the resulting canonical transformation induces not only decomposition of the gravitational fields into selfdual and antiselfdual modes, but also a splitting of the Rarita-Schwinger fields into their chiral parts in a natural way. In some detail, we also analyze the consequences for axial and chiral anomalies.

  4. Catalysis of Dynamical Chiral Symmetry Breaking by Chiral Chemical Potential

    CERN Document Server

    Braguta, V V

    2016-01-01

    In this paper we study the properties of media with chiral imbalance parameterized by chiral chemical potential. It is shown that depending on the strength of interaction between constituents in the media the chiral chemical potential either creates or enhances dynamical chiral symmetry breaking. Thus the chiral chemical potential plays a role of the catalyst of dynamical chiral symmetry breaking. Physically this effect results from the appearance of the Fermi surface and additional fermion states on this surface which take part in dynamical chiral symmetry breaking. An interesting conclusion which can be drawn is that at sufficiently small temperature chiral plasma is unstable with respect to condensation of Cooper pairs and dynamical chiral symmetry breaking even for vanishingly small interactions between constituents.

  5. Reconfigurable self-assembly through chiral control of interfacial tension.

    Science.gov (United States)

    Gibaud, Thomas; Barry, Edward; Zakhary, Mark J; Henglin, Mir; Ward, Andrew; Yang, Yasheng; Berciu, Cristina; Oldenbourg, Rudolf; Hagan, Michael F; Nicastro, Daniela; Meyer, Robert B; Dogic, Zvonimir

    2012-01-04

    From determining the optical properties of simple molecular crystals to establishing the preferred handedness in highly complex vertebrates, molecular chirality profoundly influences the structural, mechanical and optical properties of both synthetic and biological matter on macroscopic length scales. In soft materials such as amphiphilic lipids and liquid crystals, the competition between local chiral interactions and global constraints imposed by the geometry of the self-assembled structures leads to frustration and the assembly of unique materials. An example of particular interest is smectic liquid crystals, where the two-dimensional layered geometry cannot support twist and chirality is consequently expelled to the edges in a manner analogous to the expulsion of a magnetic field from superconductors. Here we demonstrate a consequence of this geometric frustration that leads to a new design principle for the assembly of chiral molecules. Using a model system of colloidal membranes, we show that molecular chirality can control the interfacial tension, an important property of multi-component mixtures. This suggests an analogy between chiral twist, which is expelled to the edges of two-dimensional membranes, and amphiphilic surfactants, which are expelled to oil-water interfaces. As with surfactants, chiral control of interfacial tension drives the formation of many polymorphic assemblages such as twisted ribbons with linear and circular topologies, starfish membranes, and double and triple helices. Tuning molecular chirality in situ allows dynamical control of line tension, which powers polymorphic transitions between various chiral structures. These findings outline a general strategy for the assembly of reconfigurable chiral materials that can easily be moved, stretched, attached to one another and transformed between multiple conformational states, thus allowing precise assembly and nanosculpting of highly dynamical and designable materials with complex

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

    Science.gov (United States)

    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.

  7. Chiral discrimination in optical trapping and manipulation

    Science.gov (United States)

    Bradshaw, David S.; Andrews, David L.

    2014-10-01

    When circularly polarized light interacts with chiral molecules or nanoscale particles powerful symmetry principles determine the possibility of achieving chiral discrimination, and the detailed form of electrodynamic mechanisms dictate the types of interaction that can be involved. The optical trapping of molecules and nanoscale particles can be described in terms of a forward-Rayleigh scattering mechanism, with trapping forces being dependent on the positioning within the commonly non-uniform intensity beam profile. In such a scheme, nanoparticles are commonly attracted to local potential energy minima, ordinarily towards the centre of the beam. For achiral particles the pertinent material response property usually entails an electronic polarizability involving transition electric dipole moments. However, in the case of chiral molecules, additional effects arise through the engagement of magnetic counterpart transition dipoles. It emerges that, when circularly polarized light is used for the trapping, a discriminatory response can be identified between left- and right-handed polarizations. Developing a quantum framework to accurately describe this phenomenon, with a tensor formulation to correctly represent the relevant molecular properties, the theory leads to exact analytical expressions for the associated energy landscape contributions. Specific results are identified for liquids and solutions, both for isotropic media and also where partial alignment arises due to a static electric field. The paper concludes with a pragmatic analysis of the scope for achieving enantiomer separation by such methods.

  8. Chiral Brownian heat pump

    OpenAIRE

    Van Den Broek, Martijn; Van Den Broeck, Christian

    2007-01-01

    We present the exact analysis of a chiral Brownian motor and heat pump. Optimization of the construction predicts, for a nanoscale device, frequencies of the order of kHz and cooling rates of the order of femtojoule per second.

  9. Chiral brownian heat pump.

    Science.gov (United States)

    van den Broek, M; Van den Broeck, C

    2008-04-04

    We present the exact analysis of a chiral Brownian motor and heat pump. Optimization of the construction predicts, for a nanoscale device, frequencies of the order of kHz and cooling rates of the order of femtojoule per second.

  10. Color chiral solitons

    CERN Document Server

    Novozhilov, V Yu; Novozhilov, Victor; Novozhilov, Yuri

    2002-01-01

    We discuss specific features of color chiral solitons (asymptotics, possibility of confainment, quantization) at example of isolated SU(2) color skyrmions, i.e. skyrmions in a background field which is the vacuum field forming the gluon condensate.

  11. Measuring the optical chirality of molecular aggregates at liquid-liquid interfaces.

    Science.gov (United States)

    Watarai, Hitoshi; Adachi, Kenta

    2009-10-01

    Some new experimental methods for measuring the optical chirality of molecular aggregates formed at liquid-liquid interfaces have been reviewed. Chirality measurements of interfacial aggregates are highly important not only in analytical spectroscopy but also in biochemistry and surface nanochemistry. Among these methods, a centrifugal liquid membrane method was shown to be a highly versatile method for measuring the optical chirality of the liquid-liquid interface when used in combination with a commercially available circular dichroism (CD) spectropolarimeter, provided that the interfacial aggregate exhibited a large molar absorptivity. Therefore, porphyrin and phthalocyanine were used as chromophoric probes of the chirality of itself or guest molecules at the interface. A microscopic CD method was also demonstrated for the measurement of a small region of a film or a sheet sample. In addition, second-harmonic generation and Raman scattering methods were reviewed as promising methods for detecting interfacial optical molecules and measuring bond distortions of chiral molecules, respectively.

  12. Electrodynamics of chiral matter

    Science.gov (United States)

    Qiu, Zebin; Cao, Gaoqing; Huang, Xu-Guang

    2017-02-01

    Many-body systems with chiral fermions can exhibit novel transport phenomena that violate parity and time-reversal symmetries, such as the chiral magnetic effect, the anomalous Hall effect, and the anomalous generation of charge. Based on the Maxwell-Chern-Simons electrodynamics, we examine some electromagnetic and optical properties of such systems including the electrostatics, the magnetostatics, the propagation of electromagnetic waves, the novel optical effects, etc.

  13. Chiral Odd GPDs

    Directory of Open Access Journals (Sweden)

    Goldstein Gary R.

    2015-01-01

    Full Text Available Nucleon spin structure, transversity and the tensor charge are of central importance to understanding the role of QCD in hadronic physics. A new approach to measuring orbital angular momenta of quarks in the proton via twist 3 GPDs is shown. The “flexible parametrization” of chiral even GPDs is reviewed and its transformation into the chiral odd sector is discussed. The resulting parametrization is applied to recent data on π0 and η electroproduction.

  14. Chlorophylls, Symmetry, Chirality, and Photosynthesis

    Directory of Open Access Journals (Sweden)

    Mathias O. Senge

    2014-09-01

    Full Text Available Chlorophylls are a fundamental class of tetrapyrroles and function as the central reaction center, accessory and photoprotective pigments in photosynthesis. Their unique individual photochemical properties are a consequence of the tetrapyrrole macrocycle, the structural chemistry and coordination behavior of the phytochlorin system, and specific substituent pattern. They achieve their full potential in solar energy conversion by working in concert in highly complex, supramolecular structures such as the reaction centers and light-harvesting complexes of photobiology. The biochemical function of these structures depends on the controlled interplay of structural and functional principles of the apoprotein and pigment cofactors. Chlorophylls and bacteriochlorophylls are optically active molecules with several chiral centers, which are necessary for their natural biological function and the assembly of their supramolecular complexes. However, in many cases the exact role of chromophore stereochemistry in the biological context is unknown. This review gives an overview of chlorophyll research in terms of basic function, biosynthesis and their functional and structural role in photosynthesis. It highlights aspects of chirality and symmetry of chlorophylls to elicit further interest in their role in nature.

  15. Induced solvent chirality: A VCD study of camphor in CDCl 3

    Science.gov (United States)

    Debie, Elke; Jaspers, Lize; Bultinck, Patrick; Herrebout, Wouter; Veken, Benjamin Van Der

    2008-01-01

    It is shown how the presence of a chiral compound in solution induces chirality in the surrounding solvent molecules. Using Vibrational Circular Dichroism on camphor dissolved in deuterated chloroform, it is found that the C-D stretch in the latter indeed becomes VCD active. The experimental results agree with ab initio computed spectra for 1:1 associations between the solvent and solute.

  16. Sum-Frequency Generation from Chiral Media and Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Na [Univ. of California, Berkeley, CA (United States)

    2006-02-13

    Sum frequency generation (SFG), a second-order nonlinear optical process, is electric-dipole forbidden in systems with inversion symmetry. As a result, it has been used to study chiral media and interfaces, systems intrinsically lacking inversion symmetry. This thesis describes recent progresses in the applications of and new insights into SFG from chiral media and interfaces. SFG from solutions of chiral amino acids is investigated, and a theoretical model explaining the origin and the strength of the chiral signal in electronic-resonance SFG spectroscopy is discussed. An interference scheme that allows us to distinguish enantiomers by measuring both the magnitude and the phase of the chiral SFG response is described, as well as a chiral SFG microscope producing chirality-sensitive images with sub-micron resolution. Exploiting atomic and molecular parity nonconservation, the SFG process is also used to solve the Ozma problems. Sum frequency vibrational spectroscopy is used to obtain the adsorption behavior of leucine molecules at air-water interfaces. With poly(tetrafluoroethylene) as a model system, we extend the application of this surface-sensitive vibrational spectroscopy to fluorine-containing polymers.

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

    Science.gov (United States)

    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.

  18. Nanoconfinement-induced structures in chiral liquid crystals.

    Science.gov (United States)

    Melle, Michael; Theile, Madlona; Hall, Carol K; Schoen, Martin

    2013-08-28

    We employ Monte Carlo simulations in a specialized isothermal-isobaric and in the grand canonical ensemble to study structure formation in chiral liquid crystals as a function of molecular chirality. Our model potential consists of a simple Lennard-Jones potential, where the attractive contribution has been modified to represent the orientation dependence of the interaction between a pair of chiral liquid-crystal molecules. The liquid crystal is confined between a pair of planar and atomically smooth substrates onto which molecules are anchored in a hybrid fashion. Hybrid anchoring allows for the formation of helical structures in the direction perpendicular to the substrate plane without exposing the helix to spurious strains. At low chirality, we observe a cholesteric phase, which is transformed into a blue phase at higher chirality. More specifically, by studying the unit cell and the spatial arrangement of disclination lines, this blue phase can be established as blue phase II. If the distance between the confining substrates and molecular chirality are chosen properly, we see a third structure, which may be thought of as a hybrid, exhibiting mixed features of a cholesteric and a blue phase.

  19. Nanoconfinement-Induced Structures in Chiral Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Carol K. Hall

    2013-08-01

    Full Text Available We employ Monte Carlo simulations in a specialized isothermal-isobaric and in the grand canonical ensemble to study structure formation in chiral liquid crystals as a function of molecular chirality. Our model potential consists of a simple Lennard-Jones potential, where the attractive contribution has been modified to represent the orientation dependence of the interaction between a pair of chiral liquid-crystal molecules. The liquid crystal is confined between a pair of planar and atomically smooth substrates onto which molecules are anchored in a hybrid fashion. Hybrid anchoring allows for the formation of helical structures in the direction perpendicular to the substrate plane without exposing the helix to spurious strains. At low chirality, we observe a cholesteric phase, which is transformed into a blue phase at higher chirality. More specifically, by studying the unit cell and the spatial arrangement of disclination lines, this blue phase can be established as blue phase II. If the distance between the confining substrates and molecular chirality are chosen properly, we see a third structure, which may be thought of as a hybrid, exhibiting mixed features of a cholesteric and a blue phase.

  20. Chiral separation and twin-beam photonics

    Science.gov (United States)

    Bradshaw, David S.; Andrews, David L.

    2016-03-01

    It is well-known that, in a homogeneous fluid medium, most optical means that afford discrimination between molecules of opposite handedness are intrinsically weak effects. The reason is simple: the wide variety of origins for differential response commonly feature real or virtual electronic transitions that break a parity condition. Despite being electric dipole allowed, they manifest the chirality of the material in which they occur by breaking a selection rule that would otherwise preclude the simultaneous involvement of magnetic dipole or electric quadrupole forms of coupling. Although the latter are typically weaker than electric dipole effects by several orders of magnitude, it is the involvement of these weak forms of interaction that are responsible for chiral sensitivity. There have been a number of attempts to cleverly exploit novel optical configurations to enhance the relative magnitude - and hence potentially the efficiency - of chiral discrimination. The prospect of success in any such venture is enticing, because of the huge impact that such an advance might be expected to have in the health, food and medical sectors. Some of these proposals have utilized mirror reflection, and others surface plasmon coupling, or optical binding methods. Several recent works in the literature have drawn attention to a further possibility: the deployment of optical beam interference as a means to achieve chiral separations of sizeable extent. In this paper the underlying theory is fully developed to identify the true scope and limitations of such an approach.

  1. Room temperature chiral discrimination in paramagnetic NMR spectroscopy

    CERN Document Server

    Soncini, Alessandro

    2016-01-01

    A recently proposed theory of chiral discrimination in NMR spectroscopy based on the detection of a molecular electric polarization $\\mathbf{P}$ rotating in a plane perpendicular to the NMR magnetic field [A. D. Buckingham, J. Chem. Phys. $\\mathbf{140}$, 011103 (2014)], is here generalized to paramagnetic systems. Our theory predicts new contributions to $\\mathbf{P}$, varying as the square of the inverse temperature. Ab initio calculations for ten Dy$^{3+}$ complexes, at 293K, show that in strongly anisotropic paramagnetic molecules $\\mathbf{P}$ can be more than 1000 times larger than in diamagnetic molecules, making paramagnetic NMR chiral discrimination amenable to room temperature detection.

  2. Resolution of the Chiral Drugs

    Institute of Scientific and Technical Information of China (English)

    DENG; JinGen

    2001-01-01

    Chiral drugs are generally not permitted to be used in racemic form so that unintended side effects and unnecessary environmental hazards are avoided. Moreover, homochiral molecules are required immediately to progress key toxicological and clinical studies in the drug discovery. One series of technologies which can rapidly supply homochiral compounds is the separation of racemates, and of those the technique of crystallization of diastereomers is extremely effective-principally because it is simple to operate and it affords both enantiomers. In classical resolution via diastereoisomeric salt formation, the resolved compounds are limited to a given racemic acid or base and the choice of a suitable resolving agent for a racemic target compound is achieved by time-consuming trial-and-error procedure.  ……

  3. Resolution of the Chiral Drugs

    Institute of Scientific and Technical Information of China (English)

    DENG JinGen; ZHU Jin

    2001-01-01

    @@ Chiral drugs are generally not permitted to be used in racemic form so that unintended side effects and unnecessary environmental hazards are avoided. Moreover, homochiral molecules are required immediately to progress key toxicological and clinical studies in the drug discovery. One series of technologies which can rapidly supply homochiral compounds is the separation of racemates, and of those the technique of crystallization of diastereomers is extremely effective-principally because it is simple to operate and it affords both enantiomers. In classical resolution via diastereoisomeric salt formation, the resolved compounds are limited to a given racemic acid or base and the choice of a suitable resolving agent for a racemic target compound is achieved by time-consuming trial-and-error procedure.

  4. Experimental demonstration of spontaneous chirality in a nonlinear microresonator

    CERN Document Server

    Cao, Qi-Tao; Dong, Chun-Hua; Jing, Hui; Liu, Rui-Shan; Chen, Xi; Ge, Li; Gong, Qihuang; Xiao, Yun-Feng

    2016-01-01

    Chirality is an important concept that describes the asymmetry property of a system, which usually emerges spontaneously due to mirror symmetry breaking. Such spontaneous chirality manifests predominantly as parity breaking in modern physics, which has been studied extensively, for instance, in Higgs physics, double-well Bose-Einstein condensates, topological insulators and superconductors. In the optical domain, spontaneous chiral symmetry breaking has been elusive experimentally, especially for micro- and nano-photonics which demands multiple identical subsystems, such as photonic nanocavities, meta-molecules and other dual-core settings. Here, for the first time, we observe spontaneous emergence of a chiral field in a single ultrahigh-Q whispering- gallery microresonator. This counter-intuitive effect arises due to the inherent Kerr nonlinearity-modulated coupling between clockwise (CW) and counterclockwise (CCW) propagating waves. At an ultra-weak input threshold of a few hundred microwatts, the initial c...

  5. Chiral Random Matrix Theory and Chiral Perturbation Theory

    CERN Document Server

    Damgaard, P H

    2011-01-01

    Spontaneous breaking of chiral symmetry in QCD has traditionally been inferred indirectly through low-energy theorems and comparison with experiments. Thanks to the understanding of an unexpected connection between chiral Random Matrix Theory and chiral Perturbation Theory, the spontaneous breaking of chiral symmetry in QCD can now be shown unequivocally from first principles and lattice simulations. In these lectures I give an introduction to the subject, starting with an elementary discussion of spontaneous breaking of global symmetries.

  6. Chiral Random Matrix Theory and Chiral Perturbation Theory

    Energy Technology Data Exchange (ETDEWEB)

    Damgaard, Poul H, E-mail: phdamg@nbi.dk [Niels Bohr International Academy and Discovery Center, The Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen (Denmark)

    2011-04-01

    Spontaneous breaking of chiral symmetry in QCD has traditionally been inferred indirectly through low-energy theorems and comparison with experiments. Thanks to the understanding of an unexpected connection between chiral Random Matrix Theory and chiral Perturbation Theory, the spontaneous breaking of chiral symmetry in QCD can now be shown unequivocally from first principles and lattice simulations. In these lectures I give an introduction to the subject, starting with an elementary discussion of spontaneous breaking of global symmetries.

  7. Chiral Graphene Quantum Dots.

    Science.gov (United States)

    Suzuki, Nozomu; Wang, Yichun; Elvati, Paolo; Qu, Zhi-Bei; Kim, Kyoungwon; Jiang, Shuang; Baumeister, Elizabeth; Lee, Jaewook; Yeom, Bongjun; Bahng, Joong Hwan; Lee, Jaebeom; Violi, Angela; Kotov, Nicholas A

    2016-02-23

    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 for 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. Emergence of nanoscale chirality in GQDs decorated with biomolecules is expected to be a general stereochemical phenomenon for flexible sheets of nanomaterials.

  8. The Development of Chiral Catalysis in Asymmetric Synthesis%手性催化在不对称合成中的发展

    Institute of Scientific and Technical Information of China (English)

    杨晓刚; 黄蓓

    2012-01-01

    介绍了手性化合物的重要性及其发展情况,从手性分子的制备、手性有机小分子催化的应用等方面总结了手性分子的研究进展,指出了手性分子的发展方向。%The importance and devopment of chiral compounds are introduced, from the preparation of chiral molecule, the application of chiral organic small molecular catalyst, the research progress of chiral molealle are summarized, the development direction of chiral molecule are pointed out.

  9. Chirality and anaesthetic drugs: A review and an update

    Directory of Open Access Journals (Sweden)

    Sukanya Mitra

    2011-01-01

    Full Text Available Many molecules can exist as right-handed and left-handed forms that are non-superimposable mirror images of each other. They are known as enantiomers or substances of opposite shape. Such compounds are also said to be chiral (Greek chiros meaning ′hand′. Such chiral molecules are of great relevance to anaesthetic theory and practice. This review summarizes the basic concepts, pharmacokinetic and pharmacodynamic aspects of chirality, and some specific examples of their application in anaesthesia, along with recent advances to elucidate the anaesthetic mechanisms. Chirality is relevant to anaesthesia, simply because more than half of the synthetic agents used in anaesthesia practice are chiral drugs. Almost all these synthetic chiral drugs are administered as racemic mixture, rather than as single pure enantiomers. These mixtures are not drug formulations containing two or more therapeutic substances, but combination of isomeric substances, with the therapeutic activity residing mainly in one of the enantiomer. The other enantiomer can have undesirable properties, have different therapeutic activities or be pharmacologically inert. Specific examples of application of chirality in anaesthetic drugs include inhalational general anaesthetics (e.g. isoflurane, intravenous anaesthetics (e.g. etomidate, thiopentone, neuromuscular blocking agents (e.g. cisatracurium, local anaesthetics (e.g. ropivacaine and levobupivacaine and other agents (e.g. levosimendan, dexmedetomidine, L-cysteine. In the recent advances, chirality study has not only helped new drug development as mentioned above, but has also contributed in a more profound way to the understanding of the mechanism of anaesthesia and anaesthetic drugs.

  10. Chiral anomalies and differential geometry

    Energy Technology Data Exchange (ETDEWEB)

    Zumino, B.

    1983-10-01

    Some properties of chiral anomalies are described from a geometric point of view. Topics include chiral anomalies and differential forms, transformation properties of the anomalies, identification and use of the anomalies, and normalization of the anomalies. 22 references. (WHK)

  11. Quarkyonic Chiral Spirals

    CERN Document Server

    Kojo, Toru; McLerran, Larry; Pisarski, Robert D

    2009-01-01

    We consider the formation of chiral density waves in Quarkyonic matter, which is a phase where cold, dense quarks experience confining forces. We model confinement following Gribov and Zwanziger, taking the gluon propagator, in Coulomb gauge and momentum space, as 1/(p^2)^2. We assume that the number of colors, N, is large, and that the quark chemical potential, mu, is much larger than renormalization mass scale, Lambda_QCD. To leading order in 1/N and Lambda_QCD, a gauge theory with Nf flavors of massless quarks in 3+1 dimensions naturally reduces to a gauge theory in 1+1 dimensions, with an enlarged flavor symmetry of SU(2Nf). Through an anomalous chiral rotation, in two dimensions a Fermi sea of massless quarks maps directly onto the corresponding theory in vacuum. A chiral condensate forms locally, and varies with the spatial position, z, as . Following Schon and Thies, we term this two dimensional pion condensate a (Quarkyonic) chiral spiral. Massive quarks also exhibit chiral spirals, with the magnitude...

  12. Chiral Synthons in Pesticide Syntheses

    NARCIS (Netherlands)

    Feringa, Bernard

    1988-01-01

    The use of chiral synthons in the preparation of enantiomerically pure pesticides is described in this chapter. Several routes to chiral synthons based on asymmetric synthesis or on natural products are illustrated. Important sources of chiral building blocks are reviewed. Furthermore the implicatio

  13. Chiral fermions on the lattice

    CERN Document Server

    Jahn, O; Jahn, Oliver; Pawlowski, Jan M.

    2002-01-01

    We discuss topological obstructions to putting chiral fermions on an even dimensional lattice. The setting includes Ginsparg-Wilson fermions, but is more general. We prove a theorem which relates the total chirality to the difference of generalised winding numbers of chiral projection operators. For an odd number of Weyl fermions this implies that particles and anti-particles live in topologically different spaces.

  14. [Chirality and drugs].

    Science.gov (United States)

    Testa, B; Reist, M; Carrupt, P A

    2000-07-01

    The two enantiomers of a chiral drug may have vastly different pharmacodynamic and pharmacokinetic properties. As a result, the research and development of chiral drugs raises specific problems some of which are discussed here. Thus, various pharmacokinetic interactions may involve two enantiomers, as seen for example when one enantiomer inhibits the metabolism of the other and modifies its effects. A different situation occurs when a third compound stereoselectively inhibits the metabolism of one of the two enantiomers. Another problem examined here results from the lack of configurational stability of some chiral drugs, a little known phenomenon whose consequences can be of pharmacological or pharmaceutical significance depending on the rate of the reaction of racemization or epimerisation. In-depth investigations are needed before choosing between a eutomer or a racemate.

  15. Doped Chiral Polymer Metamaterials

    Science.gov (United States)

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

  16. Chiral Quantum Optics

    CERN Document Server

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

    2016-01-01

    At the most fundamental level, the interaction between light and matter is manifested by the emission and absorption of single photons by single quantum emitters. Controlling light--matter interaction is the basis for diverse applications ranging from light technology to quantum--information processing. Many of these applications are nowadays based on photonic nanostructures strongly benefitting from their scalability and integrability. The confinement of light in such nanostructures imposes an inherent link between the local polarization and propagation direction of light. This leads to {\\em chiral light--matter interaction}, i.e., the emission and absorption of photons depend on the propagation direction and local polarization of light as well as the polarization of the emitter transition. The burgeoning research field of {\\em chiral quantum optics} offers fundamentally new functionalities and applications both for single emitters and ensembles thereof. For instance, a chiral light--matter interface enables...

  17. Dynamic Figure Eight Chirality: Multifarious Inversions of a Helical Preference Induced by Complexation.

    Science.gov (United States)

    Katoono, Ryo; Tanaka, Yuki; Kusaka, Keiichi; Fujiwara, Kenshu; Suzuki, Takanori

    2015-08-07

    We demonstrate two types of inversion of a helical preference upon the 1:1 complexation of a dynamic figure eight molecule with a guest molecule through the controlled transmission of point chirality. We designed a series of macrocycles that prefer a nonplanar conformation with figure eight chirality. These macrocycles are composed of a chirality-transferring unit (terephthalamide) and a structure-modifying unit (two o-phenylene rings spaced with a varying number of triple bonds). The former unit provides a binding site for capturing a guest molecule through the formation of hydrogen bonds. The attachment of chiral auxiliaries to the former unit induces a helical preference for a particular sense through the intramolecular transmission of point chirality. For relatively small-sized macrocycles, the preferred sense was reversed upon complexation with an achiral guest. Contrary preferences before and after complexation were both seen for chiral auxiliaries associated with a figure eight host through two-way intramolecular transmission of the single chiral source. Alternatively, the helical preference induced in relatively large-sized macrocycles was reversed only when a figure eight host formed a 1:1 complex with a particular enantiomeric guest through the supramolecular transmission of point chirality in the guest. This stereospecific inversion of a helical preference is rare.

  18. Chiral quark model

    Indian Academy of Sciences (India)

    H Weigel

    2003-11-01

    In this talk I review studies of hadron properties in bosonized chiral quark models for the quark flavor dynamics. Mesons are constructed from Bethe–Salpeter equations and baryons emerge as chiral solitons. Such models require regularization and I show that the two-fold Pauli–Villars regularization scheme not only fully regularizes the effective action but also leads the scaling laws for structure functions. For the nucleon structure functions the present approach serves to determine the regularization prescription for structure functions whose leading moments are not given by matrix elements of local operators. Some numerical results are presented for the spin structure functions.

  19. Host–Guest Chirality Interplay: A Mutually Induced Formation of a Chiral ZMOF and Its Double-Helix Polymer Guests

    KAUST Repository

    Luo, Xiaolong

    2016-01-12

    A novel homochiral zeolite-like metal-organic framework (ZMOF), [(Cu4I4) (dabco)2]·[Cu2(bbimb)]·3DMF (JLU-Liu23, dabco =1,4-diazabicyclo[2.2.2]-octane, H2bbimb =1,3-bis(2-benzimidazol)benzene, DMF = N,N-dimethylformamide), has been successfully constructed to host unprecedented DNA-like [Cu2(bbimb)]n polymers with double-helicity. The host-guest chirality interplay permitted the induced formation of an unusual gyroid MOF with homochirality and helical channels in the framework for the first time, JLU-Liu23. Importantly, the enantiomeric pairs (23P, 23M) can be promoted and isolated in the presence of appropriate chiral inducing agents, affording enantioselective separation of chiral molecules as well as small gas molecules. © 2016 American Chemical Society.

  20. Chirality Synchronization of Hydrogen-Bonded Complexes of Achiral N-Heterocycles.

    Science.gov (United States)

    Buchs, Jens; Vogel, Laura; Janietz, Dietmar; Prehm, Marko; Tschierske, Carsten

    2017-01-02

    2,4-Diamino-6-phenyl-1,3,5-triazines carrying a single oligo(ethylene oxide) (EO) chain form an optically isotropic mesophase composed of a conglomerate of macroscopic chiral domains with opposite sense of chirality even though the constituent molecules are achiral. This mesophase was proposed to result from the helical packing of hydrogen-bonded triazine aggregates, providing long-range chirality synchronization. The results provide first evidence for macroscopic achiral symmetry breaking upon conglomerate formation in an amorphous isotropic phase formed by hydrogen-bonded associates of simple N-heterocycles that are related to prebiotic molecules.

  1. Absolute Asymmetric Synthesis : The Origin, Control, and Amplification of Chirality

    NARCIS (Netherlands)

    Feringa, Ben L.; van Delden, Richard A.

    1999-01-01

    One of the fundamental and intriguing aspects of life is the homochirality of the essential molecules. From the early days of stereochemistry, the origin of chirality in biological systems has been a challenge to the chemical sciences and numerous theories and experiments have been reported. Despite

  2. Interweaving Chiral Spirals

    CERN Document Server

    Kojo, Toru; Fukushima, Kenji; McLerran, Larry; Pisarski, Robert D

    2011-01-01

    We elaborate how to construct the interweaving chiral spirals in (2+1) dimensions, that is defined as a superposition of differently oriented chiral spirals. We divide the two-dimensional Fermi sea into distinct wedges characterized by the opening angle 2 Theta and the depth Q \\simeq pF, where pF is the Fermi momentum. Each wedge earns an energy gain by forming a single chiral spiral. The optimal values for Theta and Q are chosen by the balance between this energy gain and the energy costs from the deformed Fermi surface (dominant at large Theta) and patch-patch interactions (dominant at small Theta). We estimate these energy gains and costs by means of the expansions in terms of 1/Nc, Lambda_QCD/Q, and Theta using a non-local four-Fermi interaction model: At small 1/Nc the mass gap (chiral condensate) is large enough and the interaction among quarks and the condensate is local in momentum space thanks to the form factor in our non-local model. The fact that patch-patch interactions lie only near the patch bo...

  3. Simplicial chiral models

    CERN Document Server

    Rossi, P; Rossi, Paolo; Tan, Chung I

    1995-01-01

    Principal chiral models on a d-1 dimensional simplex are introduced and studied analytically in the large N limit. The d = 0 , 2, 4 and \\infty models are explicitly solved. Relationship with standard lattice models and with few-matrix systems in the double scaling limit are discussed.

  4. Chiral magnetic effect without chirality source in asymmetric Weyl semimetals

    CERN Document Server

    Kharzeev, Dmitri; Meyer, Rene

    2016-01-01

    We describe a new type of the Chiral Magnetic Effect (CME) that should occur in Weyl semimetals with an asymmetry in the dispersion relations of the left- and right-handed chiral Weyl fermions. In such materials, time-dependent pumping of electrons from a non-chiral external source generates a non-vanishing chiral chemical potential. This is due to the different capacities of the left- and right-handed (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 f...

  5. Enantiospecific adsorption of cysteine on a chiral Au34 cluster

    Science.gov (United States)

    de Jesús Pelayo, José; Valencia, Israel; Díaz, Gabriela; López-Lozano, Xóchitl; Garzón, Ignacio L.

    2015-12-01

    The interaction of biological molecules like chiral amino acids with chiral metal clusters is becoming an interesting and active field of research because of its potential impact in, for example, chiral molecular recognition phenomena. In particular, the enantiospecific adsorption (EA) of cysteine (Cys) on a chiral Au55 cluster was theoretically predicted a few years ago. In this work, we present theoretical results, based on density functional theory, of the EA of non-zwitterionic cysteine interacting with the C3-Au34 chiral cluster, which has been experimentally detected in gas phase, using trapped ion electron diffraction. Our results show that, indeed, the adsorption energy of the amino acid depends on which enantiomers participate in the formation Cys-Au34 chiral complex. EA was obtained in the adsorption modes where both the thiol, and the thiol-amino functional groups of Cys are adsorbed on low-coordinated sites of the metal cluster surface. Similarly to what was obtained for the Cys-Au55 chiral complex, in the present work, it is found that the EA is originated from the different strength and location of the bond between the COOH functional group and surface Au atoms of the Au34 chiral cluster. Calculations of the vibrational spectrum for the different Cys-Au34 diastereomeric complexes predict the existence of a vibro-enantiospecific effect, indicating that the vibrational frequencies of the adsorbed amino acid depend on its handedness. Contribution to the Topical Issue "Atomic Cluster Collisions (7th International Symposium)", edited by G. Delgado Barrio, A. Solov'Yov, P. Villarreal, R. Prosmiti.

  6. Detecting the chirality for coupled quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Cao Huijuan [Institute for Condensed Matter Physics, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510631 (China); Hu Lian [Institute for Condensed Matter Physics, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510631 (China)], E-mail: huliancaohj@yahoo.com

    2008-04-21

    We propose a scheme to detect the chirality for a system consisting of three coupled quantum dots. The chirality is found to be determined by the frequency of the transition between chiral states under the chiral symmetry broken perturbation. The results are important to construct quantum gates and to demonstrate chiral entangle states in the triangle spin dots.

  7. Second harmonic generation of chiral-modified silver nanoparticles

    Science.gov (United States)

    Tao, Yue

    Chiral molecules, which exist under enantiomers with non-mirror-symmetrical structures, have been the subject of intense research for their linear and nonlinear optical activities. Cysteine is such a chiral amino acid found as a building block of proteins throughout human bodies. Second harmonic generation (SHG) has been considered to investigate chiral molecules. SHG from metallic nanoparticles is promising for nanoplasmonics and photonic nanodevice applications. Therefore, it's desirable to combine and study nonlinear properties due to both chirality and metallic nanoparticles, and help developing an alternatively optical diagnostic of chiral molecules. Our experiments are carried out with the FemtoFiber Scientific FFS laser system. SHG of silver nanoparticles (Ag NPs) modified by either L-Cysteine (L-C) or D-Cysteine (D-C) is observed, where L-Cysteine and D-Cysteine are a pair of enantiomers. Ag NPs are deposited through Vacuum Thermal Evaporation, controlled under different deposition thicknesses. UV-Vis/IR spectra and AFM are used to characterize Ag NPs under different conditions. Transmitted SHG measurements dependent on incidence are recorded with standard lock-in techniques. Deposition thickness of vacuum thermal evaporation plays an important role in forming diverse Ag NPs, which strongly imparts the intensity of SHG. Second harmonic intensity as a function of the incident angle presents similar results for Ag NPs with or without L-Cysteine or D-Cysteine modification, in the output of p- and s-polarization. However, we monitor reversed rotation difference in second harmonic intensities at linearly +45° and -45° polarization for L-C/Ag NPs and D-C/Ag NPs, while there's no difference at linearly +45° and -45° polarization for Ag NPs alone. This optical rotation difference in SHG is termed as SHG-ORD. Also, for second harmonic light fixed at p-polarization, L-C/Ag NPs and D-C/Ag NPs exhibit a reversely net difference for SHG excited by right and left

  8. Final Technical Report for DOE Grant DE-FG02-03ER15473 “Molecular Level Design of Heterogeneous Chiral Catalysis”

    Energy Technology Data Exchange (ETDEWEB)

    David Sholl; Andrew Gellman

    2007-03-15

    The production of enantiomerically pure chiral compounds is of great importance in the pharmaceutical industry. Although processes involving chiral catalysis and separations involving solid surfaces are known, the molecular-scale details of these processes are not well understood. This lack of understanding strongly limits the development of new chiral processes. Our collaborative research effort examines several intertwined aspects of chirality and enantioselectivity at catalytically active metal surfaces. At Carnegie Mellon, our efforts focus on the development of chirally imprinted metal powders as materials for chiral columns and the experimental and theoretical study of small chiral molecules adsorbed on well-characterized metal surfaces, both achiral and chiral. These efforts are being performed in close collaboration with our team members at the University of California Riverside and the University of Wisconsin Milwaukee.

  9. Metal-organic complex-functionalized protein nanopore sensor for aromatic amino acids chiral recognition.

    Science.gov (United States)

    Guo, Yanli; Niu, Aihua; Jian, Feifei; Wang, Ying; Yao, Fujun; Wei, Yongfeng; Tian, Lei; Kang, Xiaofeng

    2017-03-27

    Chiral recognition at single-molecule level for small active molecules is important, as exhibited by many nanostructures and molecular assemblies in biological systems, but it presents a significant challenge. We report a simple and rapid sensing strategy to discriminate all enantiomers of natural aromatic amino acids (AAA) using a metal-organic complex-functionalized protein nanopore, in which a chiral recognition element and a chiral recognition valve were equipped. A trifunctional molecule, heptakis-(6-deoxy-6-amino)-β-cyclodextrin (am7βCD), was non-covalently lodged within the nanopore of an α-hemolysin (αHL) mutant, (M113R)7-αHL. Copper(ii) ion reversibly bonds to the amino group of am7βCD to form an am7βCD-Cu(II) complex, which allowed chiral recognition for each enantiomer in the mixture of AAA by distinct current signals. The Cu(II) plugging valve plays a crucial rule that holds chiral molecules in the nanocavity for a sufficient registering time. Importantly, six enantiomers of all nature AAA could be simultaneously recognized at one time. Enantiomeric excess (ee) could also be accurately detected by this approach. It should be possible to generalize this approach for sensing of other chiral molecules.

  10. Concise theory of chiral lipid membranes

    CERN Document Server

    Tu, Z C

    2007-01-01

    A theory of chiral lipid membranes is proposed on the basis of a concise free energy density which includes the contributions of the bending and the surface tension of membranes, as well as the chirality and orientational variation of tilting molecules. This theory is consistent with the previous experiments [J.M. Schnur \\textit{et al.}, Science \\textbf{264}, 945 (1994); M.S. Spector \\textit{et al.}, Langmuir \\textbf{14}, 3493 (1998); Y. Zhao, \\textit{et al.}, Proc. Natl. Acad. Sci. USA \\textbf{102}, 7438 (2005)] on self-assembled chiral lipid membranes of DC$_{8,9}$PC. A torus with the ratio between its two generated radii larger than $\\sqrt{2}$ is predicted from the Euler-Lagrange equations. It is found that tubules with helically modulated tilting state are not admitted by the Euler-Lagrange equations, and that they are less energetically favorable than helical ripples in tubules. The pitch angles of helical ripples are theoretically estimated to be about 0$^\\circ$ and 35$^\\circ$, which are close to the mo...

  11. Analysis of Chiral Carboxylic Acids in Meteorites

    Science.gov (United States)

    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

  12. Time-Harmonic Optical Chirality in Inhomogeneous Space

    CERN Document Server

    Gutsche, Philipp; Hammerschmidt, Martin; Burger, Sven; Schmidt, Frank

    2016-01-01

    Optical chirality has been recently suggested to complement the physically relevant conserved quantities of the well-known Maxwell's equations. This time-even pseudoscalar is expected to provide further insight in polarization phenomena of electrodynamics such as spectroscopy of chiral molecules. Previously, the corresponding continuity equation was stated for homogeneous lossless media only. We extend the underlying theory to arbitrary setups and analyse piecewise-constant material distributions in particular. Our implementation in a Finite Element Method framework is applied to illustrative examples in order to introduce this novel tool for the analysis of time-harmonic simulations of nano-optical devices.

  13. Liquid Crystal Phases of Molecular Bananas: Polarity and Chirality as Broken Symmetries

    Science.gov (United States)

    Clark, Noel

    2006-03-01

    The study of the interplay of chirality and polarity has been a particularly rich theme of soft matter science since Meyer's seminal discovery that tilted smectics of chiral molecules are macroscopically polar. This event, and the subsequent realization of polar domains and high-speed electro-optic switching in chiral smectics, engaged the liquid crystal community in a worldwide pursuit of novel smectics for applications, featured by the synthesis of more than 50,000 new liquid crystal compounds, and by a consequent broad diversification of the palette of liquid crystal phases and possibilities for supermolecular ordering. A current important activity in this scenario is the study of polar order in synthetically achiral molecules, for example, in molecular bananas, which, as their shape suggests, might be expected to organize in a polar way. Indeed they do, but beyond this, almost everything learned about them has been surprising, including their persistent tendency to exhibit chirality as a spontaneously broken symmetry. I will discuss some of these new phases and phenomena, including the discovery of fluid conglomerates (Pasteur's experiment in a fluid), triclinic fluid order, chiral twist grain boundary phases of achiral molecules, chirality flipping and field-induced deracemization, ferroelectric and antiferroelectric phases with supermolecular- scale polarization modulation, and chiral thermotropic sponge phases.

  14. Soldering Chiralities; 2, Non-Abelian Case

    CERN Document Server

    Wotzasek, C

    1996-01-01

    We study the non-abelian extension of the soldering process of two chiral WZW models of opposite chiralities, resulting in a (non-chiral) WZW model living in a 2D space-time with non trivial Riemanian curvature.

  15. Explanation for the Emergence of a Single Chiral Solid State during Attrition-Enhanced Ostwald Ripening : Survival of the Fittest

    NARCIS (Netherlands)

    Noorduin, Wim L.; Meekes, Hugo; Bode, Arno A.C.; Enckevort, Willem J.P. van; Kaptein, Bernard; Kellogg, Richard M.; Vlieg, Elias

    2008-01-01

    The overabundant occurrence of single-handed chiral molecules in living systems has inspired scientists for well more than a century. A route to the evolution of a single chiral solid phase, using abrasive grinding of the crystals in contact with a saturated solution, has been demonstrated for the a

  16. Spiral Galaxies as Chiral Objects?

    CERN Document Server

    Capozziello, S; Capozziello, Salvatore; Lattanzi, Alessandra

    2005-01-01

    Spiral galaxies show axial symmetry and an intrinsic 2D-chirality. Environmental effects can influence the chirality of originally isolated stellar systems and a progressive loss of chirality can be recognised in the Hubble sequence. We point out a preferential modality for genetic galaxies as in microscopic systems like aminoacids, sugars or neutrinos. This feature could be the remnant of a primordial symmetry breaking characterizing systems at all scales.

  17. Chiral Biomarkers and Microfossils in Carbonaceous Meteorites

    Science.gov (United States)

    Hoover, Richard B.

    2010-01-01

    Homochirality of the biomolecules (D-sugars of DNA and RNA and L-amino acids of proteins) is a fundamental property of all life on Earth. Abiotic mechanisms yield racemic mixtures (D/L=1) of chiral molecules and after the death of an organism, the enantiopure chiral biomolecules slowly racemize. Several independent investigators have now established that the amino acids present in CI1 and CM2 carbonaceous meteorites have a moderate to strong excess of the L-enantiomer. Stable isotope data have established that these amino acids are both indigenous and extraterrestrial. Carbonaceous meteorites also contain many other strong chemical biomarkers including purines and pyrimidines (nitrogen heterocycles of nucleic acids); pristine and phytane (components of the chlorophyll pigment) and morphological biomarkers (microfossils of filamentous cyanobacteria). Energy dispersive X-ray Spectroscopy (EDS) analysis reveals that nitrogen is below the detectability level in most of the meteorite filaments as well as in Cambrian Trilobites and filaments of 2.7 Gya Archaean cyanobacteria from Karelia. The deficiency of nitrogen in the filaments and the total absence of sugars, of twelve of the life-critical protein amino acids, and two of the nucleobases of DNA and RNA provide clear and convincing evidence that these filaments are not modern biological contaminants. This paper reviews the chiral, chemical biomarkers morphological biomarkers and microfossils in carbonaceous meteorites. This paper reviews chiral and morphological biomarkers and discusses the missing nitrogen, sugars, protein amino acids, and nucleobases as ?bio-discriminators? that exclude modern biological contaminants as a possible explanation for the permineralized cyanobacterial filaments found in the meteorites.

  18. Chiral nuclear thermodynamics

    CERN Document Server

    Fiorilla, Salvatore; Weise, Wolfram

    2011-01-01

    We calculate the equation of state of nuclear matter for arbitrary isospin-asymmetry up to three loop order in the free energy density in the framework of in-medium chiral perturbation theory. In our approach 1\\pi- and 2\\pi-exchange dynamics with the inclusion of the \\Delta-isobar excitation as an explicit degree of freedom, corresponding to the long- and intermediate-range correlations, are treated explicitly. Few contact terms fixed to reproduce selected known properties of nuclear matter encode the short-distance physics. Two-body as well as three-body forces are systematically included. We find a critical temperature of about 15 MeV for symmetric nuclear matter. We investigate the dependence of the liquid-gas first-order phase transition on isospin-asymmetry. In the same chiral framework we calculate the chiral condensate of isospin-symmetric nuclear matter at finite temperatures. The contribution of the \\Delta-isobar excitation is essential for stabilizing the condensate. As a result, we find no indicati...

  19. Generalized simplicial chiral models

    CERN Document Server

    Alimohammadi, M

    2000-01-01

    Using the auxiliary field representation of the simplicial chiral models on a (d-1)-dimensional simplex, we generalize the simplicial chiral models by replacing the term Tr$(AA^{\\d})$ in the Lagrangian of these models, by an arbitrary class function of $AA^{\\d}; V(AA^{\\d})$. This is the same method that has been used in defining the generalized two-dimensional Yang-Mills theories (gYM_2) from ordinary YM_2. We call these models, the " generalized simplicial chiral models ". With the help of the results of one-link integral over a U(N) matrix, we compute the large-N saddle-point equations for eigenvalue density function $\\ro (z)$ in the weak ($\\b >\\b_c$) and strong ($\\b <\\b_c$) regions. In d=2, where the model somehow relates to gYM_2 theory, we solve the saddle-point equations and find $\\ro (z)$ in two region, and calculate the explicit value of critical point $\\b_c$ for $V(B)=TrB^n (B=AA^{\\d})$. For $V(B)=Tr B^2,Tr B^3$ and Tr$B^4$, we study the critical behaviour of the model at d=2, and by calculating t...

  20. Chiral expression at the solid-liquid interface: a joint experimental and theoretical study of the self-assembly of chiral porphyrins on graphite.

    Science.gov (United States)

    Linares, Mathieu; Iavicoli, Patrizia; Psychogyiopoulou, Krystallia; Beljonne, David; De Feyter, Steven; Amabilino, David B; Lazzaroni, Roberto

    2008-09-01

    The chiral organization of an enantiopure functional molecule on an achiral surface has been studied with the aim of understanding the influence of stereogenic centers on the self-assembly in two dimensions. A chiral tetra meso-amidophenyl-substituted porphyrin containing long hydrophobic tails at the periphery of the conjugated pi-electron system was prepared for this purpose. Scanning tunneling microscopy (STM) images of the compound at the graphite-heptanol interface reveal a chiral arrangement of the molecules, with the porphyrin rows tilted by 13 degrees with respect to the normal to the graphite axes. In terms of molecular modeling, a combination of molecular dynamics simulations on systems constrained by periodic boundary conditions and on unconstrained large molecular aggregates has been applied to reach a quantitative interpretation on both the density of the layer and its orientation with respect to the graphite surface. The results show clearly that (i) the methyl groups of the stereogenic point toward the graphite surface and (ii) the porphyrin molecules self-assemble into an interdigitated structure where the alkyl chains align along one of the graphite axes and the porphyrin cores are slightly shifted with respect to one another. The direction of this shift, which defines the chirality of the monolayer, is set by the chirality of the stereogenic centers. Such an arrangement results in the formation of a dense chiral monolayer that is further stabilized by hydrogen bonding with protic solvents.

  1. Origins of the handedness of biological molecules.

    Science.gov (United States)

    Mason, S F

    1991-01-01

    Pasteur (1860) showed that many organic molecules form enantiomeric pairs with non-superposable mirror-image shapes, characterized by their oppositely signed optical rotation but otherwise apparently identical. Equal numbers of left-handed and right-handed molecules resulted from laboratory synthesis, whereas biosynthetic processes afforded only one of the two enantiomers, leading Pasteur to conclude that biosynthesis involves a chiral force. Fischer demonstrated (1890-1919) that functional biomolecules are composed specifically of the D-sugars and the L-amino acids and that the laboratory synthetic reactions of such molecules propagate with chiral stereoselectivity. Given a primordial enantiomer, biomolecular homochirality follows without the intervention of a chiral natural force, except prebiotically. Chiral forces known at the time were found to be even handed on a time and space average, exemplifying parity conservation (1927). The weak nuclear force, shown to violate parity (1956), was unified with electro-magnetism in the electroweak force (1970). Ab initio estimations including the chiral electroweak force indicate that the L-amino acids and the D-sugars are more stable than the corresponding enantiomers. The small energy difference between these enantiomeric pairs, with Darwinian reaction kinetics in a flow reactor, account for the choice of biomolecular handedness made when life began.

  2. Heavy Exotic Molecules with Charm and Bottom

    CERN Document Server

    Liu, Yizhuang

    2016-01-01

    We revisit the formation of pion-mediated heavy-light exotic molecules with both charm and bottom and their chiral partners under the general strictures of both heavy-quark and chiral symmetry. The chiral exotic partners with good parity formed using the $(0^+, 1^+)$ multiplet are about twice more bound than their primary exotic partners formed using the $(0^-,1^-)$ multiplet. The chiral couplings across the multiplets $(0^\\pm, 1^\\pm)$ cause the chiral exotic partners to unbind, and the primary exotic molecules to be about twice more bound, for $J\\leq 1$. Our multi-channel coupling results show that only the charm isosinglet exotic molecules with $J^{PC}=1^{++}$ binds, which we identify as the reported neutral $X(3872)$. Also, the bottom isotriplet exotic with $J^{PC}=1^{+-}$ binds, which we identify as a mixture of the reported charged exotics $Z^+_b(10610)$ and $Z^+_b(10650)$. The bound isosinglet with $J^{PC}=1^{++}$ is suggested as a possible neutral $X_b(10532)$ not yet reported.

  3. Heavy exotic molecules with charm and bottom

    Science.gov (United States)

    Liu, Yizhuang; Zahed, Ismail

    2016-11-01

    We revisit the formation of pion-mediated heavy-light exotic molecules with both charm and bottom and their chiral partners under the general strictures of both heavy-quark and chiral symmetry. The chiral exotic partners with good parity formed using the (0+ ,1+) multiplet are about twice more bound than their primary exotic partners formed using the (0- ,1-) multiplet. The chiral couplings across the multiplets (0± ,1±) cause the chiral exotic partners to unbind, and the primary exotic molecules to be about twice more bound, for J ≤ 1. Our multi-channel coupling results show that only the charm isosinglet exotic molecules with JPC =1++ bind, which we identify as the reported neutral X (3872). Also, the bottom isotriplet exotic with JPC =1+- binds, which we identify as a mixture of the reported charged exotics Zb+ (10610) and Zb+ (10650). The bound isosinglet with JPC =1++ is suggested as a possible neutral Xb (10532) not yet reported.

  4. Spontaneous Generation of Chirality in Simple Diaryl Ethers.

    Science.gov (United States)

    Lennartson, Anders; Hedström, Anna; Håkansson, Mikael

    2015-07-01

    We studied the spontaneous formation of chiral crystals of four diaryl ethers, 3-phenoxybenzaldehyde, 1; 1,3-dimethyl-2-phenoxybenzene, 2; di(4-aminophenyl) ether, 3; and di(p-tolyl) ether, 4. Compounds 1, 3, and 4 form conformationally chiral molecules in the solid state, while the chirality of 2 arises from the formation of supramolecular helices. Compound 1 is a liquid at ambient temperature, but 2-4 are crystalline, and solid-state CD-spectroscopy showed that they could be obtained as optically active bulk samples. It should be noted that the optical activity arise upon crystallization, and no optically active precursors were used. Indeed, even commercial samples of 3 and 4 were found to be optically active, giving evidence for the ease at which total spontaneous resolution may occur in certain systems.

  5. Supernovae, Neutrinos and the Chirality of Amino Acids

    Directory of Open Access Journals (Sweden)

    Toshitaka Kajino

    2011-05-01

    Full Text Available A mechanism for creating an enantioenrichment in the amino acids, the building blocks of the proteins, that involves global selection of one handedness by interactions between the amino acids and neutrinos from core-collapse supernovae is defined. The chiral selection involves the dependence of the interaction cross sections on the orientations of the spins of the neutrinos and the 14N nuclei in the amino acids, or in precursor molecules, which in turn couple to the molecular chirality. It also requires an asymmetric distribution of neutrinos emitted from the supernova. The subsequent chemical evolution and galactic mixing would ultimately populate the Galaxy with the selected species. The resulting amino acids could either be the source thereof on Earth, or could have triggered the chirality that was ultimately achieved for Earth’s proteinaceous amino acids.

  6. Stardust, Supernovae and the Chirality of the Amino Acids

    Energy Technology Data Exchange (ETDEWEB)

    Boyd, R N; Kajino, T; Onaka, T

    2011-03-09

    A mechanism for creating enantiomerism in the amino acids, the building blocks of the proteins, that involves global selection of one chirality by interactions between the amino acids and neutrinos from core-collapse supernovae is described. The selection involves the dependence of the interaction cross sections on the orientations of the spins of the neutrinos and the 14N nuclei in the amino acids, or in precursor molecules, which in turn couple to the molecular chirality. The subsequent chemical evolution and galactic mixing would ultimately populate the Galaxy with the selected species. The resulting amino acids could either be the source thereof on Earth, or could have triggered the chirality that was ultimately achieved for Earth's amino acids.

  7. Supernovae, Neutrinos, and the Chirality of the Amino Acids

    CERN Document Server

    Boyd, R N; Onaka, T

    2011-01-01

    A mechanism for creating an enantioenrichment in the amino acids, the building blocks of the proteins, that involves global selection of one handedness by interactions between the amino acids and neutrinos from core-collapse supernovae is described. The chiral selection involves the dependence of the interaction cross sections on the orientations of the spins of the neutrinos and the 14N nuclei in the amino acids, or in precursor molecules, which in turn couple to the molecular chirality. It also requires an asymmetric distribution of neutrinos emitted from the supernova. The subsequent chemical evolution and galactic mixing would ultimately populate the Galaxy with the selected species. The resulting amino acids could either be the source thereof on Earth, or could have triggered the chirality that was ultimately achieved for Earth's proteinaceous amino acids.

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

    CERN Document Server

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

    2016-01-01

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

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

    Science.gov (United States)

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

    2016-10-01

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

  10. Spontaneous chiral resolution in two-dimensional systems of patchy particles

    Energy Technology Data Exchange (ETDEWEB)

    Martínez-González, J. A.; Chapela, G. A. [Departamento de Física, Universidad Autónoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco 186, Col. Vicentina, 09340 México D.F. (Mexico); Quintana-H, J., E-mail: jaq@unam.mx [Instituto de Química, Universidad Nacional Autónoma de México - Apdo. Postal 70213, 04510 Coyoacán, México D.F. (Mexico)

    2014-05-21

    Short ranged potentials and their anisotropy produce spontaneous chiral resolution in a two dimensional model of patchy particles introduced in this paper. This model could represent an equimolar binary mixture (racemic mixture) of two kinds of chiral molecules (enantiomers) adsorbed to a bi-dimensional domain where only lateral short ranged interactions are present. Most racemic mixtures undergo chiral resolution due to their spatial anisotropy, the combined effect of long range forces and the thermodynamic conditions. The patchy particles are modeled as a hard disk and four different bonding sites located to produce chirality. Phase behavior and structural properties are analysed using Discontinuous Molecular Dynamics in the canonical ensemble. When the four patchy particles are separated by the angles (60°, 120°, 60°, 120°), spontaneous chiral resolution is produced, given by the formation of homochiral clusters, if started from the corresponding racemic mixture. Gel behavior is also obtained in all the systems for low temperatures and low densities.

  11. Enantiomer Identification in Chiral Mixtures with Broadband Microwave Spectroscopy

    Science.gov (United States)

    Shubert, V. Alvin; Schmitz, David; Medcraft, Chris; Patterson, David; Doyle, John M.; Schnell, Melanie

    2014-06-01

    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 components, determine which enantiomers are present, and to measure the enantiomeric excesses (ee) is still one of the challenging but very important tasks of analytical chemistry. These analyses are required at every step of modern drug development, from candidate searches to production and regulation. We present here a new method of identifying individual enantiomers in mixtures of chiral molecules in the gas phase. It is based on broadband rotational spectroscopy and employs a sum or difference frequency generation 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 (see figure), as it depends upon the combined quantity, μaμbμc, which is of opposite sign between members of an enantiomeric pair. Furthermore, because the signal amplitude is proportional to the ee, this technique allows for both determining which enantiomer is in excess and by how much. The high resolution of our technique allows us to perform molecule specific measurements of mixtures of chiral molecules with μaμbμc ≠ 0, even when the molecules are very similar (e.g. conformational isomers). We introduce the technique and present results on the analysis of mixtures of the terpenes, carvone, menthone, and carvomenthenol. D. Patterson, M. Schnell, J. M. Doyle, Nature. 497, 475-477, 2013 V. A. Shubert, D. Schmitz, D. Patterson, J. M. Doyle, M. Schnell, Ang. Chem. Int. Ed. 53, 1152-1155,2014

  12. Isothermal Titration Calorimetry of Chiral Polymeric Nanoparticles.

    Science.gov (United States)

    Werber, Liora; Preiss, Laura C; Landfester, Katharina; Muñoz-Espí, Rafael; Mastai, Yitzhak

    2015-09-01

    Chiral polymeric nanoparticles are of prime importance, mainly due to their enantioselective potential, for many applications such as catalysis and chiral separation in chromatography. In this article we report on the preparation of chiral polymeric nanoparticles by miniemulsion polymerization. In addition, we describe the use of isothermal titration calorimetry (ITC) to measure the chiral interactions and the energetics of the adsorption of enantiomers from aqueous solutions onto chiral polymeric nanoparticles. The characterization of chirality in nano-systems is a very challenging task; here, we demonstrate that ITC can be used to accurately determine the thermodynamic parameters associated with the chiral interactions of nanoparticles. The use of ITC to measure the energetics of chiral interactions and recognition at the surfaces of chiral nanoparticles can be applied to other nanoscale chiral systems and can provide further insight into the chiral discrimination processes of nanomaterials.

  13. Chiral Dynamics 2006

    Science.gov (United States)

    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

  14. Interlocked chiral/polar domain walls and large optical rotation in Ni3TeO6

    Directory of Open Access Journals (Sweden)

    Xueyun Wang

    2015-07-01

    Full Text Available Chirality, i.e., handedness, pervades much of modern science from elementary particles, DNA-based biology to molecular chemistry; however, most of the chirality-relevant materials have been based on complex molecules. Here, we report inorganic single-crystalline Ni3TeO6, forming in a corundum-related R3 structure with both chirality and polarity. These chiral Ni3TeO6 single crystals exhibit a large optical specific rotation (α—1355° dm−1 cm3 g−1. We demonstrate, for the first time, that in Ni3TeO6, chiral and polar domains form an intriguing domain pattern, resembling a radiation warning sign, which stems from interlocked chiral and polar domain walls through lowering of the wall energy.

  15. Interlocked chiral/polar domain walls and large optical rotation in Ni{sub 3}TeO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xueyun; Huang, Fei-Ting [Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854 (United States); Yang, Junjie [Laboratory for Pohang Emergent Materials and Max Plank POSTECH Center for Complex Phase Materials, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Oh, Yoon Seok [Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854 (United States); Department of Physics, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798 (Korea, Republic of); Cheong, Sang-Wook, E-mail: sangc@physics.rutgers.edu [Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854 (United States); Laboratory for Pohang Emergent Materials and Max Plank POSTECH Center for Complex Phase Materials, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of)

    2015-07-01

    Chirality, i.e., handedness, pervades much of modern science from elementary particles, DNA-based biology to molecular chemistry; however, most of the chirality-relevant materials have been based on complex molecules. Here, we report inorganic single-crystalline Ni{sub 3}TeO{sub 6}, forming in a corundum-related R3 structure with both chirality and polarity. These chiral Ni{sub 3}TeO{sub 6} single crystals exhibit a large optical specific rotation (α)—1355° dm{sup −1} cm{sup 3} g{sup −1}. We demonstrate, for the first time, that in Ni{sub 3}TeO{sub 6}, chiral and polar domains form an intriguing domain pattern, resembling a radiation warning sign, which stems from interlocked chiral and polar domain walls through lowering of the wall energy.

  16. Chirality-sensitive nuclear magnetic resonance effects induced by indirect spin-spin coupling

    Science.gov (United States)

    Garbacz, P.; Buckingham, A. D.

    2016-11-01

    It is predicted that, for two spin-1/2 nuclei coupled by indirect spin-spin coupling in a chiral molecule, chirality-sensitive induced electric polarization can be observed at the frequencies equal to the sum and difference between the spin resonance frequencies. Also, an electric field oscillating at the difference frequency can induce spin coherences which allow the direct discrimination between enantiomers by nuclear magnetic resonance. The dominant contribution to the magnitude of these expected chiral effects is proportional to the permanent electric dipole moment and to the antisymmetric part of the indirect spin-spin coupling tensor of the chiral molecule. Promising compounds for experimental tests of the predictions are derivatives of 1,3-difluorocyclopropene.

  17. Supramolecular chiral host-guest nanoarchitecture induced by the selective assembly of barbituric acid derivative enantiomers

    Science.gov (United States)

    Sun, Xiaonan; Silly, Fabien; Maurel, Francois; Dong, Changzhi

    2016-10-01

    Barbituric acid derivatives are prochiral molecules, i.e. they are chiral upon adsorption on surfaces. Scanning tunneling microscopy reveals that barbituric acid derivatives self-assemble into a chiral guest-host supramolecular architecture at the solid-liquid interface on graphite. The host nanoarchitecture has a sophisticated wavy shape pattern and paired guest molecules are nested insides the cavities of the host structure. Each unit cell of the host structure is composed of both enantiomers with a ratio of 1:1. Furthermore, the wavy patterns of the nanoarchitecture are formed from alternative appearance of left- and right-handed chiral building blocks, which makes the network heterochiral. The functional guest-host nanoarchitecture is the result of two-dimensional chiral amplification from single enantiomers to organizational heterochiral supramolecular self-assembly.

  18. Opportunities for chiral discrimination using high harmonic generation in tailored laser fields

    CERN Document Server

    Smirnova, Olga; Patchkovskii, Serguei

    2015-01-01

    Chiral discrimination with high harmonic generation (cHHG method) has been introduced in the recent work by R. Cireasa et al ( Nat. Phys. 11, 654 - 658, 2015). In its original implementation, the cHHG method works by detecting high harmonic emission from randomly oriented ensemble of chiral molecules driven by elliptically polarized field, as a function of ellipticity. Here we discuss future perspectives in the development of this novel method, the ways of increasing chiral dichroism using tailored laser pulses, new detection schemes involving high harmonic phase measurements, and concentration-independent approaches. Using the example of the epoxypropane molecule C$_3$H$_6$O (also known as 1,2-propylene oxide), we show theoretically that application of two-color counter-rotating elliptically polarized laser fields yields an order of magnitude enhancement of chiral dichroism compared to single color elliptical fields. We also describe how one can introduce a new functionality to cHHG: concentration-independen...

  19. Dileptons and Chiral Symmetry Restoration

    CERN Document Server

    Hohler, P M

    2015-01-01

    We report on recent work relating the medium effects observed in dilepton spectra in heavy-ion collisions to potential signals of chiral symmetry restoration. The key connection remains the approach to spectral function degeneracy between the vector-isovector channel with its chiral partner, the axialvector-isovector channel. Several approaches are discussed to elaborate this connection, namely QCD and Weinberg sum rules with input for chiral order parameters from lattice QCD, and chiral hadronic theory to directly evaluate the medium effects of the axialvector channel and the pertinent pion decay constant as function of temperature. A pattern emerges where the chiral mass splitting between rho and a_1 burns off and is accompanied by a strong broadening of the spectral distributions.

  20. Applications Of Chiral Perturbation Theory

    CERN Document Server

    Mohta, V

    2005-01-01

    Effective field theory techniques are used to describe the spectrum and interactions of hadrons. The mathematics of classical field theory and perturbative quantum field theory are reviewed. The physics of effective field theory and, in particular, of chiral perturbation theory and heavy baryon chiral perturbation theory are also reviewed. The geometry underlying heavy baryon chiral perturbation theory is described in detail. Results by Coleman et. al. in the physics literature are stated precisely and proven. A chiral perturbation theory is developed for a multiplet containing the recently- observed exotic baryons. A small coupling expansion is identified that allows the calculation of self-energy corrections to the exotic baryon masses. Opportunities in lattice calculations are discussed. Chiral perturbation theory is used to study the possibility of two multiplets of exotic baryons mixed by quark masses. A new symmetry constraint on reduced partial widths is identified. Predictions in the literature based ...

  1. Quark structure of chiral solitons

    CERN Document Server

    Diakonov, D

    2004-01-01

    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 and additional quark-antiquark pairs. We also find the 5-quark wave function of the exotic baryon Theta+.

  2. Optically active quantum-dot molecules.

    Science.gov (United States)

    Shlykov, Alexander I; Baimuratov, Anvar S; Baranov, Alexander V; Fedorov, Anatoly V; Rukhlenko, Ivan D

    2017-02-20

    Chiral molecules made of coupled achiral semiconductor nanocrystals, also known as quantum dots, show great promise for photonic applications owing to their prospective uses as configurable building blocks for optically active structures, materials, and devices. Here we present a simple model of optically active quantum-dot molecules, in which each of the quantum dots is assigned a dipole moment associated with the fundamental interband transition between the size-quantized states of its confined charge carriers. This model is used to analytically calculate the rotatory strengths of optical transitions occurring upon the excitation of chiral dimers, trimers, and tetramers of general configurations. The rotatory strengths of such quantum-dot molecules are found to exceed the typical rotatory strengths of chiral molecules by five to six orders of magnitude. We also study how the optical activity of quantum-dot molecules shows up in their circular dichroism spectra when the energy gap between the molecular states is much smaller than the states' lifetime, and maximize the strengths of the circular dichroism peaks by optimizing orientations of the quantum dots in the molecules. Our analytical results provide clear design guidelines for quantum-dot molecules and can prove useful in engineering optically active quantum-dot supercrystals and photonic devices.

  3. Observing Disoriented Chiral Condensates

    CERN Document Server

    Bjorken, James D; Taylor, C C

    1993-01-01

    We speculate that, in very high energy hadronic collisions, large fireballs may be produced with interiors which have anomalous chiral order parameters. Such a process would result in radiation of pions with distinctive momentum and isospin distributions, and may provide an explanation of Centauro and related phenomena in cosmic-ray events. The phenomenology of such events is reviewed, with emphasis on the possibility of observing such phenomena at Fermilab experiment T-864 (MiniMax), or at a Full Acceptance Detector (FAD) at the SSC.

  4. Chiral Nuclear Dynamics II

    CERN Document Server

    Rho, Mannque

    2008-01-01

    This is the sequel to the first volume to treat in one effective field theory framework the physics of strongly interacting matter under extreme conditions. This is vital for understanding the high temperature phenomena taking place in relativistic heavy ion collisions and in the early Universe, as well as the high-density matter predicted to be present in compact stars. The underlying thesis is that what governs hadronic properties in a heat bath and/or a dense medium is hidden local symmetry which emerges from chiral dynamics of light quark systems and from the duality between QCD in 4D and

  5. Intrinsic Chirality of CdSe/ZnS Quantum Dots and Quantum Rods.

    Science.gov (United States)

    Mukhina, Maria V; Maslov, Vladimir G; Baranov, Alexander V; Fedorov, Anatoly V; Orlova, Anna O; Purcell-Milton, Finn; Govan, Joseph; Gun'ko, Yurii K

    2015-05-13

    A new class of chiral nanoparticles is of great interest not only for nanotechnology, but also for many other fields of scientific endeavor. Normally the chirality in semiconductor nanocrystals is induced by the initial presence of chiral ligands/stabilizer molecules. Here we report intrinsic chirality of ZnS coated CdSe quantum dots (QDs) and quantum rods (QRs) stabilized by achiral ligands. As-prepared ensembles of these nanocrystals have been found to be a racemic mixture of d- and l-nanocrystals which also includes a portion of nonchiral nanocrystals and so in total the solution does not show a circular dichroism (CD) signal. We have developed a new enantioselective phase transfer technique to separate chiral nanocrystals using an appropriate chiral ligand and obtain optically active ensembles of CdSe/ZnS QDs and QRs. After enantioselective phase transfer, the nanocrystals isolated in organic phase, still capped with achiral ligands, now display circular dichroism (CD). We propose that the intrinsic chirality of CdSe/ZnS nanocrystals is caused by the presence of naturally occurring chiral defects.

  6. Spontaneous Chiral Symmetry Breaking as Condensation of Dynamical Chirality

    CERN Document Server

    Alexandru, Andrei

    2012-01-01

    The occurrence of spontaneous chiral symmetry breaking (SChSB) is equivalent to sufficient abundance of Dirac near-zeromodes. However, dynamical mechanism leading to breakdown of chiral symmetry should be naturally reflected in chiral properties of the modes. Here we offer such connection, presenting evidence that SChSB in QCD proceeds via the appearance of modes exhibiting dynamical tendency for local chiral polarization. These modes form a band of finite width Lambda_ch (chiral polarization scale) around the surface of otherwise anti--polarized Dirac sea, and condense. Lambda_ch characterizes the dynamics of the breaking phenomenon and can be converted to a quark mass scale, thus offering conceptual means to determine which quarks of nature are governed by broken chiral dynamics. It is proposed that, within the context of SU(3) gauge theories with fundamental Dirac quarks, mode condensation is equivalent to chiral polarization, making Lambda_ch an "order parameter" of SChSB. Several uses of these features, ...

  7. Repulsive Casimir Force in Chiral Metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, R.; Zhou, J.; Koschny, Th.; Economou, E.N.; Soukoulis, C.M.

    2009-09-04

    We demonstrate theoretically that one can obtain repulsive Casimir forces and stable nanolevitations by using chiral metamaterials. By extending the Lifshitz theory to treat chiral metamaterials, we find that a repulsive force and a minimum of the interaction energy possibly exist for strong chirality, under realistic frequency dependencies and correct limiting values (for zero and infinite frequencies) of the permittivity, permeability, and chiral coefficients.

  8. Repulsive Casimir Force in Chiral Metamaterials

    OpenAIRE

    Zhao, R.; J. Zhou; Koschny, Th.; Economou, E. N.; C M Soukoulis

    2009-01-01

    We demonstrate theoretically that one can obtain repulsive Casimir forces and stable nanolevitations by using chiral metamaterials. By extending the Lifshitz theory to treat chiral metamaterials, we find that a repulsive force and a minimum of the interaction energy exist for strong chirality, under realistic frequency dependencies and correct limiting values (for zero and infinite frequencies) of the permittivity, permeability, and chiral coefficients.

  9. Repulsive Casimir Force in Chiral Metamaterials

    Science.gov (United States)

    Zhao, R.; Zhou, J.; Koschny, Th.; Economou, E. N.; Soukoulis, C. M.

    2009-09-01

    We demonstrate theoretically that one can obtain repulsive Casimir forces and stable nanolevitations by using chiral metamaterials. By extending the Lifshitz theory to treat chiral metamaterials, we find that a repulsive force and a minimum of the interaction energy possibly exist for strong chirality, under realistic frequency dependencies and correct limiting values (for zero and infinite frequencies) of the permittivity, permeability, and chiral coefficients.

  10. Origin of organic molecules and biomolecular homochirality.

    Science.gov (United States)

    Podlech, J

    2001-01-01

    Theories about the origin of biomolecular homochirality, which seems to be a prerequisite for the creation of life, are discussed. First, possible terrestrial and extraterrestrial sources of organic molecules are outlined. Then, mechanisms for the formation of enantiomerically enriched compounds and for the amplification of their chirality are described.

  11. Chiral selectivity of amino acid adsorption on chiral surfaces—The case of alanine on Pt

    Energy Technology Data Exchange (ETDEWEB)

    Franke, J.-H.; Kosov, D. S. [Department of Physics, Campus Plaine - CP 231, Université Libre de Bruxelles, 1050 Brussels (Belgium)

    2015-02-07

    We study the binding pattern of the amino acid alanine on the naturally chiral Pt surfaces Pt(531), Pt(321), and Pt(643). These surfaces are all vicinal to the (111) direction but have different local environments of their kink sites and are thus a model for realistic roughened Pt surfaces. Alanine has only a single methyl group attached to its chiral center, which makes the number of possible binding conformations computationally tractable. Additionally, only the amine and carboxyl group are expected to interact strongly with the Pt substrate. On Pt(531), we study the molecule in its pristine as well as its deprotonated form and find that the deprotonated one is more stable by 0.47 eV. Therefore, we study the molecule in its deprotonated form on Pt(321) and Pt(643). As expected, the oxygen and nitrogen atoms of the deprotonated molecule provide a local binding “tripod” and the most stable adsorption configurations optimize the interaction of this “tripod” with undercoordinated surface atoms. However, the interaction of the methyl group plays an important role: it induces significant chiral selectivity of about 60 meV on all surfaces. Hereby, the L-enantiomer adsorbs preferentially to the Pt(321){sup S} and Pt(643){sup S} surfaces, while the D-enantiomer is more stable on Pt(531){sup S}. The binding energies increase with increasing surface density of kink sites, i.e., they are largest for Pt(531){sup S} and smallest for Pt(643){sup S}.

  12. Nanoscale chirality in metal and semiconductor nanoparticles.

    Science.gov (United States)

    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.

  13. Nonequilibrium chiral perturbation theory and disoriented chiral condensates

    CERN Document Server

    Nicola, A G

    1999-01-01

    We analyse the extension of Chiral Perturbation Theory to describe a meson gas out of thermal equilibrium. For that purpose, we let the pion decay constant be a time-dependent function and work within the Schwinger-Keldysh contour technique. A useful connection with curved space-time QFT allows to consistently renormalise the model, introducing two new low-energy constants in the chiral limit. We discuss the applicability of our approach within a Relativistic Heavy-Ion Collision environment. In particular, we investigate the formation of Disoriented Chiral Condensate domains in this model, via the parametric resonance mechanism.

  14. Chiral quantum optics.

    Science.gov (United States)

    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.

  15. Chiral imbalance in QCD

    Directory of Open Access Journals (Sweden)

    Andrianov Alexander

    2017-01-01

    Full Text Available The chiral imbalance (ChI is given by a difference between the numbers of RH and LH quarks which may occur in the fireball after heavy ion collision. To characterize it adiabatically a quark chiral (axial chemical potential must be introduced taking into account emergence of a ChI in such a phase. In this report the phenomenology of formation of Local spatial Parity Breaking (LPB in the hot and dense baryon matter is discussed and its simulation within a number of QCD-inspired models is outlined. The appearance of new states in the spectra of scalar, pseudoscalar and vector particles in such a matter is elucidated. In particular, from the effective vector meson theory in the presence of Chern-Simons interaction it is demonstrated that the spectrum of massive vector mesons splits into three polarization components with different effective masses. The asymmetry in production of longitudinally and transversely polarized states of ρ and ω mesons for various values of the dilepton invariant mass can serve as a characteristic indication of the LPB in PHENIX, STAR and ALICE experiments.

  16. Chirally extended quantum chromodynamics

    CERN Document Server

    Brower, R C; Tan, C I; Richard C Brower; Yue Shen; Chung-I Tan

    1994-01-01

    We propose an extended Quantum Chromodynamics (XQCD) Lagrangian in which the fermions are coupled to elementary scalar %\\sigma and \\pi fields through a Yukawa coupling which preserves chiral invariance. Our principle motivation is to find a new lattice formulation for QCD which avoids the source of critical slowing down usually encountered as the bare quark mass is tuned to the chiral limit. The phase diagram and the weak coupling limit for XQCD are studied. They suggest a conjecture that the continuum limit of XQCD is the same as the continuum limit of conventional lattice formulation of QCD. As examples of such universality, we present the large N solutions of two prototype models for XQCD, in which the mass of the spurious pion and sigma resonance go to infinity with the cut-off. Even if the universality conjecture turns out to be false, we believe that XQCD will still be useful as a low energy effective action for QCD phenomenology on the lattice. Numerical simulations are recommended to further investiga...

  17. Stereogenicity revisited. Proposal of holantimers for comprehending the relationship between stereogenicity and chirality.

    Science.gov (United States)

    Fujita, Shinsaku

    2004-04-30

    The close relationship between stereogenicity and chirality has frequently caused serious confusion in the stereochemistry of organic molecules and inorganic complexes. To clarify the entangled relationship between them, we have proposed the concept of "holantimer". In addition, we have newly defined the concept of "stereoisogram" in order to correlate a set of stereoiomers based on holantimeric and enantiomeric relationships. These concepts have been applied to tetrahedral organic molecules as well as to square-planar inorganic complexes. The stereogenicity characterized by a stereoisogram has been called "RS-stereogenicity", which has been clarified to be a property that should be correlated to chirality. The stereoisograms of tetrahedral molecules have been examined and classified into five types, i.e., type I (chiral/RS-stereogenic), type II (chiral/RS-astereogenic), type III (chiral/RS-stereogenic), type IV (achiral/RS-astereogenic), and type V (achiral/RS-stereogenic), where RS descriptors are concluded to be specified in cases of types I, III, and V. On the other hand, the stereoisograms of square-planar complexes have been classified to two types, i.e., type II and type IV. As a result, the confusion on the RS-nomenclature has been concluded to appear within the RS-stereogenic relationships. Such a new viewpoint of stereogenicity and chirality as described in the present paper provides us with a methodology for restructuring stereochemistry.

  18. Coupling chiral bosons to gravity

    CERN Document Server

    Braga, N R F; Braga, N R F; Wotzasek, C

    1995-01-01

    chiral boson actions of Floreanini and Jackiw (FJ), and of McClain,Wu and Yu (MWY) have been recently shown to be different representations of the same chiral boson theory. MWY displays manifest covariance and also a (gauge) symmetry that is hidden in the FJ side, which, on the other hand, displays the physical spectrum in a simple manner. We make use of the covariance of the MWY representation for the chiral boson to couple it to background gravity showing explicitly the equivalence with the previous results for the FJ representation

  19. Chiral gravity in higher dimensions

    CERN Document Server

    Ootsuka, T; Ura, K; Ootsuka, Takayoshi; Tanaka, Erico; Ura, Kousuke

    2003-01-01

    We construct a chiral theory of gravity in 7 and 8 dimensions, which are equivalent to Einstein-Cartan theory using less variables. In these dimensions, we can construct such higher dimensional chiral gravity because of the existence of gravitational instanton. The octonionic-valued variables in the theory represent the deviation from the gravitational instanton, and from their non-associativity, prevents the theory to be SO(n) gauge invariant. Still the chiral gravity holds G_2 (7-D), and Spin(7) (8-D) gauge symmetry.

  20. Chiral Fermions on the Lattice

    CERN Document Server

    Bietenholz, Wolfgang

    2010-01-01

    In the last century the non-perturbative regularization of chiral fermions was a long-standing problem. We review how this problem was finally overcome by the formulation of a modified but exact form of chiral symmetry on the lattice. This also provides a sound definition of the topological charge of lattice gauge configurations. We illustrate a variety of applications to QCD in the p-, the epsilon- and the delta-regime, where simulation results can now be related to Random Matrix Theory and Chiral Perturbation Theory. The latter contains Low Energy Constants as free parameters, and we comment on their evaluation from first principles of QCD.

  1. Field induced spin chirality and chirality switching in magnetic multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Tartakovskaya, Elena V., E-mail: elena_tartakovskaya@yahoo.com [Institute of Magnetism NAS of Ukraine, Vernadsky blvd 36b, 03142 Kiev (Ukraine); Institute of High Technologies, Taras Shevchenko National University of Kiev, 03022 Kiev (Ukraine)

    2015-05-01

    The physical origin of the field-induced spin chirality experimentally observed in rare earth multilayers is determined. It is shown that the effect is possible due to the interplay between solid-state exchange interactions (the Ruderman–Kittel–Kasuya–Yosida and the Dsyaloshinsky–Moriya interactions), the external magnetic field and a special confinement of magnetic constituents. The presented model describes a certain temperature dependence of the chirality factor in agreement with experimental data and opens a new way to design nanostructured objects with predicted handedness. - Highlights: • Field-induced spin chirality in magnetic multilayers is explained. • The roles of the RKKY, the DM and the Zeeman interactions are clarified. • Theoretical analysis of the chirality factor is in agreement with experimental data.

  2. Chiral Relaxation Time at the Chiral Crossover of Quantum Chromodynamics

    CERN Document Server

    Ruggieri, M; Chernodub, M

    2016-01-01

    We study microscopic processes responsible for chirality flips in the thermal bath of Quantum Chromodynamics at finite temperature and zero baryon chemical potential. We focus on the temperature range where the crossover from chirally broken phase to quark-gluon plasma takes place, namely $T \\simeq (150, 200)$ MeV. The processes we consider are quark-quark scatterings mediated by collective excitations with the quantum number of pions and $\\sigma$-meson, hence we refer to these processes simply as \\sugg{to} one-pion (one-$\\sigma$) exchange\\sugg{s}. We use a Nambu-Jona-Lasinio model to compute equilibrium properties of the thermal bath, as well as the relevant scattering kernel to be used in the collision integral to estimate the chiral relaxation time $\\tau$. We find $\\tau\\simeq 0.1 \\div 1$ fm/c around the chiral crossover.

  3. Consistent chiral kinetic theory in Weyl materials: chiral magnetic plasmons

    CERN Document Server

    Gorbar, E V; Shovkovy, I A; Sukhachov, P O

    2016-01-01

    We argue that the correct definition of the electric current in the chiral kinetic theory for Weyl materials should include the Chern--Simons contribution that makes the theory consistent with the local conservation of the electric charge in electromagnetic and strain-induced pseudoelectromagnetic fields. By making use of such a kinetic theory, we study the plasma frequencies of collective modes in Weyl materials in constant magnetic and pseudomagnetic fields taking into account the effects of dynamical electromagnetism. We show that the collective modes are chiral plasmons. While the plasma frequency of the longitudinal collective mode coincides with the Langmuir one, this mode is unusual because it is characterized not only by oscillations of the electric current density, but also oscillations of the chiral current density. The latter are triggered by a dynamical version of the chiral electric separation effect. We also find that the plasma frequencies of the transverse modes split up in a magnetic field. T...

  4. Syntheses and molecular self-assembly of chiral phosphorami dates

    Institute of Scientific and Technical Information of China (English)

    DU, Da-Ming; HUA, Wen-Ting; WANG, Jian-Wu

    2000-01-01

    Two chiral phosphoramidates, ( R )-( - )-1, 1′-binaphthyl-2, 2′-dihydroxy-N-[ α-( S)-methylbenzyl] phosphoramidate and (-)-l,1′-biphenyl-2,2′-dihydroxy-N-[ α-( S)-methylbenzyl]- phosphoramidate were synthesized. Their crystal structures were determined by X-ray single crystal diffraction analysis. The phoshorramidate molecules are self-associated by inter molecular N-H…… O = P hydrogen bonds and aromatic edge to face interactions.

  5. Quasistatic limit for plasmon-enhanced optical chirality

    Science.gov (United States)

    Finazzi, Marco; Biagioni, Paolo; Celebrano, Michele; Duò, Lamberto

    2015-05-01

    We discuss the possibility of enhancing the chiroptical response from molecules uniformly distributed around nanostructures that sustain localized plasmon resonances. We demonstrate that the average optical chirality in the near field of any plasmonic nanostructure cannot be significantly higher than that in a plane wave. This conclusion stems from the quasistatic nature of the nanoparticle-enhanced electromagnetic fields and from the fact that, at optical frequencies, the magnetic response of matter is much weaker than the electric one.

  6. Chirality in photonic systems

    Science.gov (United States)

    Solnyshkov, Dmitry; Malpuech, Guillaume

    2016-10-01

    The optical modes of photonic structures are the so-called TE and TM modes that bring intrinsic spin-orbit coupling and chirality to these systems. This, combined with the unique flexibility of design of the photonic potential, and the possibility to mix photon states with excitonic resonances, sensitive to magnetic field and interactions, allows us to achieve many phenomena, often analogous to other solid-state systems. In this contribution, we review in a qualitative and comprehensive way several of these realizations, namely the optical spin Hall effect, the creation of spin currents protected by a non-trivial geometry, the Berry curvature for photons, and the photonic/polaritonic topological insulator.

  7. Reducible chiral metamaterials

    CERN Document Server

    Ciattoni, Alessandro; Rizza, Carlo

    2016-01-01

    We introduce the concept of 3D reducible metamaterials whose constituent permittivity can be modelled by a factorized profile. The separated cartesian coordinates dependence, easily achieved in all-optical reconfigurable materials, allows to physically regard a reducible metamaterial as a superposition of three fictitious 1D generating media. We prove that, in the long-wavelength limit, the electromagnetic response of reducible metamaterials can be reconstructed from the properties of the 1D generating media whose interplay provides large freedom to control the electromagnetic chirality. Our approach introduces an unprecedented decomposition strategy in metamaterial science which allows the full ab-initio and flexible design of a complex 3D bianisotropic response by using 1D metamaterials as basic building blocks.

  8. Amino Acids and Chirality

    Science.gov (United States)

    Cook, Jamie E.

    2012-01-01

    Amino acids are among the most heavily studied organic compound class in carbonaceous chondrites. The abundance, distributions, enantiomeric compositions, and stable isotopic ratios of amino acids have been determined in carbonaceous chondrites fi'om a range of classes and petrographic types, with interesting correlations observed between these properties and the class and typc of the chondritcs. In particular, isomeric distributions appear to correlate with parent bodies (chondrite class). In addition, certain chiral amino acids are found in enantiomeric excess in some chondrites. The delivery of these enantiomeric excesses to the early Earth may have contributed to the origin of the homochirality that is central to life on Earth today. This talk will explore the amino acids in carbonaceous chondritcs and their relevance to the origin of life.

  9. Cyclodextrin Derivatives as Chiral Supramolecular Receptors for Enantioselective Sensing

    Directory of Open Access Journals (Sweden)

    Uwe Pieles

    2006-06-01

    Full Text Available In view of the chiral nature of many bio-molecules (and all bio-macromolecules,most of therapeutically active compounds which target these molecules need to be chiraland “good handed” to be effective. In addition to asymmetric synthetic and separationmethodologies, enantioselective chemical sensors, able to distinguish between twoenantiomers of the same molecule, are of relevance. In order to design these sensing tools,two major classes of enantioselective layers have been developed. The first is based onmolecularly imprinted polymers which are produced (polymerized in the presence of theirtarget, thus the polymeric material keep in “memory” the size and the shape of this moleculeand the system could be used for sensing (not reviewed here. The second approach makesuse of sensitive layers containing chiral macrocyclic receptors able of stereoselectivemolecular recognition; these receptors are mainly based on cyclodextrins. In thiscontribution, are reviewed achievements in the use of native or chemically modifiedcyclodextrins for chiral sensing purposes (at interfaces. Potentialities of other chiralmacrocycles based on calixarenes, calix-resorcinarenes or crown-ethers as supramolecularreceptors for enantioselective sensing are discussed.

  10. Domains of Disoriented Chiral Condensate

    CERN Document Server

    Amado, R D; Lu, Yang

    1996-01-01

    The probability distribution of neutral pion fraction from independent domains of disoriented chiral condensate is characterized. The signal for the condensate is clear for a small number of domains but is greatly reduced for more than three.

  11. Review of chiral perturbation theory

    Indian Academy of Sciences (India)

    B Ananthanarayan

    2003-11-01

    A review of chiral perturbation theory and recent developments on the comparison of its predictions with experiment is presented. Some interesting topics with scope for further elaboration are touched upon.

  12. Chiral Dynamics With Wilson Fermions

    CERN Document Server

    Splittorff, K

    2012-01-01

    Close to the continuum the lattice spacing affects the smallest eigenvalues of the Wilson Dirac operator in a very specific manner determined by the way in which the discretization breaks chiral symmetry. These effects can be computed analytically by means of Wilson chiral perturbation theory and Wilson random matrix theory. A number of insights on chiral Dynamics with Wilson fermions can be obtained from the computation of the microscopic spectrum of the Wilson Dirac operator. For example, the unusual volume scaling of the smallest eigenvalues observed in lattice simulations has a natural explanation. The dynamics of the eigenvalues of the Wilson Dirac operator also allow us to determine the additional low energy constants of Wilson chiral perturbation theory and to understand why the Sharpe-Singleton scenario is only realized in unquenched simulations.

  13. Chirally motivated K - nuclear potentials

    Science.gov (United States)

    Cieplý, A.; Friedman, E.; Gal, A.; Gazda, D.; Mareš, J.

    2011-08-01

    In-medium subthreshold Kbar N scattering amplitudes calculated within a chirally motivated meson-baryon coupled-channel model are used self consistently to confront K- atom data across the periodic table. Substantially deeper K- nuclear potentials are obtained compared to the shallow potentials derived in some approaches from threshold Kbar N amplitudes, with Re VK-chiral = - (85 ± 5) MeV at nuclear matter density. When Kbar NN contributions are incorporated phenomenologically, a very deep K- nuclear potential results, Re VK-chiral + phen . = - (180 ± 5) MeV, in agreement with density dependent potentials obtained in purely phenomenological fits to the data. Self consistent dynamical calculations of K--nuclear quasibound states generated by VK-chiral are reported and discussed.

  14. Chiral Quark Model of Mesons

    CERN Document Server

    Wang, X J; Wang, Xiao-Jun; Yan, Mu-Lin

    1999-01-01

    We study SU(3)$_L\\timesSU(3)_R$ chiral quark model of mesons up to next leading order of $1/N_c$ expansion. Composite vector and axial-vector mesons resonances are introduced via non-linear realization of chiral SU(3) and vector meson dominant. Effects of one-loop graphs of pseudoscalar, vector and axial-vector mesons is calculated systematically and the significant results are obtained. Correction of effective gluon interaction is studied too. The light quark masses are introduced via new mechanism which agree with phenomenology and the requirement of chiral symmetry. Up to powers four of derivatives, chiral effective lagrangian of mesons is derived and evaluated to next leading order of $1/N_c$. Low energy limit of the model is examined. Ten low energy coupling constants $L_i(i=1,2,...,10)$ in ChPT are obtained and agree with ChPT well.

  15. Homogenization of resonant chiral metamaterials

    DEFF Research Database (Denmark)

    Andryieuski, Andrei; Menzel, C.; Rockstuhl, Carsten

    2010-01-01

    Homogenization of metamaterials is a crucial issue as it allows to describe their optical response in terms of effective wave parameters as, e.g., propagation constants. In this paper we consider the possible homogenization of chiral metamaterials. We show that for meta-atoms of a certain size...... an analytical criterion for performing the homogenization and a tool to predict the homogenization limit. We show that strong coupling between meta-atoms of chiral metamaterials may prevent their homogenization at all....

  16. Chiral thermodynamics of nuclear matter

    Energy Technology Data Exchange (ETDEWEB)

    Fiorilla, Salvatore

    2012-10-23

    The equation of state of nuclear matter is calculated at finite temperature in the framework of in-medium chiral perturbation theory up to three-loop order. The dependence of its thermodynamic properties on the isospin-asymmetry is investigated. The chiral quark condensate is evaluated for symmetric nuclear matter. Its behaviour as a function of density and temperature sets important nuclear physics constraints for the QCD phase diagram.

  17. Baryon spectrum and chiral dynamics

    CERN Document Server

    Glozman, L Ya

    1995-01-01

    New results on baryon structure and spectrum developed in collaboration with Dan Riska [1-4] are reported. The main idea is that beyond the chiral symmetry spontaneous breaking scale light and strange baryons should be considered as systems of three constituent quarks with an effective confining interaction and a chiral interaction that is mediated by the octet of Goldstone bosons (pseudoscalar mesons) between the constituent quarks.

  18. Bottom-up synthesis of chiral covalent organic frameworks and their bound capillaries for chiral separation.

    Science.gov (United States)

    Qian, Hai-Long; Yang, Cheng-Xiong; Yan, Xiu-Ping

    2016-07-12

    Covalent organic frameworks (COFs) are a novel class of porous materials, and offer great potential for various applications. However, the applications of COFs in chiral separation and chiral catalysis are largely underexplored due to the very limited chiral COFs available and their challenging synthesis. Here we show a bottom-up strategy to construct chiral COFs and an in situ growth approach to fabricate chiral COF-bound capillary columns for chiral gas chromatography. We incorporate the chiral centres into one of the organic ligands for the synthesis of the chiral COFs. We subsequently in situ prepare the COF-bound capillary columns. The prepared chiral COFs and their bound capillary columns give high resolution for the separation of enantiomers with excellent repeatability and reproducibility. The proposed strategy provides a promising platform for the synthesis of chiral COFs and their chiral separation application.

  19. Bottom-up synthesis of chiral covalent organic frameworks and their bound capillaries for chiral separation

    Science.gov (United States)

    Qian, Hai-Long; Yang, Cheng-Xiong; Yan, Xiu-Ping

    2016-07-01

    Covalent organic frameworks (COFs) are a novel class of porous materials, and offer great potential for various applications. However, the applications of COFs in chiral separation and chiral catalysis are largely underexplored due to the very limited chiral COFs available and their challenging synthesis. Here we show a bottom-up strategy to construct chiral COFs and an in situ growth approach to fabricate chiral COF-bound capillary columns for chiral gas chromatography. We incorporate the chiral centres into one of the organic ligands for the synthesis of the chiral COFs. We subsequently in situ prepare the COF-bound capillary columns. The prepared chiral COFs and their bound capillary columns give high resolution for the separation of enantiomers with excellent repeatability and reproducibility. The proposed strategy provides a promising platform for the synthesis of chiral COFs and their chiral separation application.

  20. Chirality in Bare and Passivated Gold Nanoclusters

    CERN Document Server

    Garzon, I L; Rodrigues-Hernandez, J I; Sigal, I; Beltran, M R; Michaelian, K

    2002-01-01

    Chiral structures have been found as the lowest-energy isomers of bare (Au$_{28}$ and Au$_{55}) and thiol-passivated (Au$_{28}(SCH$_{3})$_{16}$ and Au$_{38}$(SCH$_{3}$)$_{24}) gold nanoclusters. The degree of chirality existing in the chiral clusters was calculated using the Hausdorff chirality measure. We found that the index of chirality is higher in the passivated clusters and decreases with the cluster size. These results are consistent with the observed chiroptical activity recently reported for glutahione-passivated gold nanoclusters, and provide theoretical support for the existence of chirality in these novel compounds.

  1. Using the Chiral Organophosphorus Derivatizing Agents for Determination of the Enantiomeric Composition of Chiral Carboxylic Acids by 31PNMR Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    Chao CHE; Zhong Ning ZHANG; Gui Lan HUANG; Xin Xing WANG; Zhao Hai QIN

    2004-01-01

    The use of chiral organophosphorus derivatizing agents prepared in situ from chiral tartrate or chiral diamine for the 31PNMR determination of the enantiomeric composition of chiral carboxylic acids is described. The method is accurate, reliable and convenient.

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

    Science.gov (United States)

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

    2011-10-01

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

  3. Recent Advances in Multinuclear NMR Spectroscopy for Chiral Recognition of Organic Compounds

    Directory of Open Access Journals (Sweden)

    Márcio S. Silva

    2017-02-01

    Full Text Available Nuclear magnetic resonance (NMR is a powerful tool for the elucidation of chemical structure and chiral recognition. In the last decade, the number of probes, media, and experiments to analyze chiral environments has rapidly increased. The evaluation of chiral molecules and systems has become a routine task in almost all NMR laboratories, allowing for the determination of molecular connectivities and the construction of spatial relationships. Among the features that improve the chiral recognition abilities by NMR is the application of different nuclei. The simplicity of the multinuclear NMR spectra relative to 1H, the minimal influence of the experimental conditions, and the larger shift dispersion make these nuclei especially suitable for NMR analysis. Herein, the recent advances in multinuclear (19F, 31P, 13C, and 77Se NMR spectroscopy for chiral recognition of organic compounds are presented. The review describes new chiral derivatizing agents and chiral solvating agents used for stereodiscrimination and the assignment of the absolute configuration of small organic compounds.

  4. Structural origins of chiral second-order optical nonlinearity in collagen: amide I band.

    Science.gov (United States)

    Reiser, Karen M; McCourt, Alexander B; Yankelevich, Diego R; Knoesen, André

    2012-11-21

    The molecular basis of nonlinear optical (NLO) chiral effects in the amide I region of type I collagen was investigated using sum-frequency generation vibrational spectroscopy; chiral and achiral tensor elements were separated using different input/output beam polarization conditions. Spectra were obtained from native rat tail tendon (RTT) collagen and from cholesteric liquid crystal-like (LC) type I collagen films. Although RTT and LC collagen both possess long-range order, LC collagen lacks the complex hierarchical organization of RTT collagen. Their spectra were compared to assess the role of such organization in NLO chirality. No significant differences were observed between RTT and LC with respect to chiral or achiral spectra. These findings suggest that amide I NLO chiral effects in type I collagen assemblies arise predominantly from the chiral organization of amide chromophores within individual collagen molecules, rather than from supramolecular structures. The study suggests that sum-frequency generation vibrational spectroscopy may be uniquely valuable in exploring fundamental aspects of chiral nonlinearity in complex macromolecular structures.

  5. Characteristics of chiral and racemic ketoprofen drugs using terahertz time-domain spectroscopy

    Science.gov (United States)

    Du, Yong; Liu, Jianjun; Hong, Zhi

    2013-08-01

    Absorption spectra of chiral S-(+)- and racemic RS-ketoprofen pharmaceutical molecules in crystalline form were recorded in the terahertz region between 6 and 66 cm-1 (0.2 ~ 2.0 THz) by using time-domain terahertz spectroscopic (THz-TDS) measurement. Different distinctive absorption features were observed which are strikingly sensitive to the change of subtle conformational structures within such isostructural crystal molecules. The results suggest that the THz-TDS technique can be definitely used for distinguishing between chiral and racemic compounds in pharmaceutical and biological fields.

  6. Observation of enhanced chiral asymmetries in the inner-shell photoionization of uniaxially oriented methyloxirane enantiomers

    CERN Document Server

    Tia, Maurice; Kastirke, Gregor; Gatzke, Janine; Kim, Hong-Keun; Trinter, Florian; Rist, Jonas; Hartung, Alexander; Trabert, Daniel; Siebert, Juliane; Henrichs, Kevin; Becht, Jasper; Zeller, Stefan; Gassert, Helena; Wiegandt, Florian; Wallauer, Robert; Kuhlins, Andreas; Schober, Carl; Bauer, Tobias; Wechselberger, Natascha; Burzynski, Phillip; Neff, Jonathan; Weller, Miriam; Metz, Daniel; Kircher, Max; Waitz, Markus; Williams, Joshua B; Schmidt, Lothar; Mueller, Anne D; Knie, Andre; Hans, Andreas; Ltaief, Ltaief Ben; Ehresmann, Arno; Berger, Robert; Fukuzawa, Hironobu; Ueda, Kiyoshi; Schmidt-Boecking, Horst; Doerner, Reinhard; Jahnke, Till; Demekhin, Philipp V; Schoeffler, Markus

    2016-01-01

    Most large molecules are chiral in their structure: they exist as two enantiomers, which are mirror images of each other. Whereas the rovibronic sublevels of two enantiomers are almost identical, it turns out that the photoelectric effect is sensitive to the absolute configuration of the ionized enantiomer - an effect termed Photoelectron Circular Dichroism (PECD). Our comprehensive study demonstrates that the origin of PECD can be found in the molecular frame electron emission pattern connecting PECD to other fundamental photophysical effects as the circular dichroism in angular distributions (CDAD). Accordingly, orienting a chiral molecule in space enhances the PECD by a factor of about 10.

  7. Asymmetric Synthesis of Fluoroamines from Chiral Aziridines

    Energy Technology Data Exchange (ETDEWEB)

    Park, Hyeonjeong; Yoon, Dooha; Ha, Hyunjoon [Hankuk Univ. of Foreign Studies, Yongin (Korea, Republic of); Son, Se In; Lee, Won Koo [Sogang Univ., Seoul (Korea, Republic of)

    2014-03-15

    We described an efficient preparation of fluoroamines by the ring-opening reactions of chiral aziridines with Et{sub 3}N·3HF. At most cases both regioisomers were obtained from the ring openings at C2 and C3 positions depending on the substituents at C2 of the starting substrates.The fluorinated organic molecules have attracted great attentions from synthetic and medicinal chemists with wide use of various agrochemicals and pharmaceuticals. Their uniqueness is originated from its electronic characteristics and the small size without altering the molecular conformations of non-fluorinated compounds. The fluorine is the second most widely used atom in the commercial drugs following the amine. Thereby, the elaboration of fluoro-amines bearing two most widely used atoms in drugs is one of the most challenging problems in drug synthesis and its development.

  8. Molecule nanoweaver

    Science.gov (United States)

    Gerald, II; Rex E.; Klingler, Robert J.; Rathke, Jerome W.; Diaz, Rocio; Vukovic, Lela

    2009-03-10

    A method, apparatus, and system for constructing uniform macroscopic films with tailored geometric assemblies of molecules on the nanometer scale. The method, apparatus, and system include providing starting molecules of selected character, applying one or more force fields to the molecules to cause them to order and condense with NMR spectra and images being used to monitor progress in creating the desired geometrical assembly and functionality of molecules that comprise the films.

  9. Engineering chiral porous metal-organic frameworks for enantioselective adsorption and separation

    Science.gov (United States)

    Peng, Yongwu; Gong, Tengfei; Zhang, Kang; Lin, Xiaochao; Liu, Yan; Jiang, Jianwen; Cui, Yong

    2014-07-01

    The separation of racemic molecules is of substantial significance not only for basic science but also for technical applications, such as fine chemicals and drug development. Here we report two isostructural chiral metal-organic frameworks decorated with chiral dihydroxy or -methoxy auxiliares from enantiopure tetracarboxylate-bridging ligands of 1,1‧-biphenol and a manganese carboxylate chain. The framework bearing dihydroxy groups functions as a solid-state host capable of adsorbing and separating mixtures of a range of chiral aromatic and aliphatic amines, with high enantioselectivity. The host material can be readily recycled and reused without any apparent loss of performance. The utility of the present adsorption separation is demonstrated in the large-scale resolution of racemic 1-phenylethylamine. Control experiments and molecular simulations suggest that the chiral recognition and separation are attributed to the different orientations and specific binding energies of the enantiomers in the microenvironment of the framework.

  10. Amplification of Chirality through Self-Replication of Micellar Aggregates in Water

    KAUST Repository

    Bukhriakov, Konstantin

    2015-03-17

    We describe a system in which the self-replication of micellar aggregates results in a spontaneous amplification of chirality in the reaction products. In this system, amphiphiles are synthesized from two "clickable" fragments: a water-soluble "head" and a hydrophobic "tail". Under biphasic conditions, the reaction is autocatalytic, as aggregates facilitate the transfer of hydrophobic molecules to the aqueous phase. When chiral, partially enantioenriched surfactant heads are used, a strong nonlinear induction of chirality in the reaction products is observed. Preseeding the reaction mixture with an amphiphile of one chirality results in the amplification of this product and therefore information transfer between generations of self-replicating aggregates. Because our amphiphiles are capable of catalysis, information transfer, and self-assembly into bounded structures, they present a plausible model for prenucleic acid "lipid world" entities. © 2015 American Chemical Society.

  11. Stirring competes with chemical induction in chiral selection of Langmuir monolayer domains

    Directory of Open Access Journals (Sweden)

    Petit-Garrido Nuria

    2013-08-01

    Full Text Available Chirality, the absence of mirror symmetry, can be equally invoked in relation to physical forces and chemical induction processes, yet a competition between these two types of influences is rarely reported. Here, we employ Langmuir monolayers of azobenzene surfactants as a prototypical self-assembled two-dimensional system in which chiral selection is controlled by the combined independent action of a chiral dopant and vortical stirring. The two effects can be arbitrarily coupled, either constructively or destructively, leading to a situation of perfect compensation. The induced enantiomorphic excess is measured in terms of the statistical imbalance of an ensemble of sub-millimeter monolayer domains, where achiral molecules self-assemble with a well-defined orientational chirality, which is unambiguously resolved using Brewster angle microscopy.

  12. Cellulose Nanocrystals as Chiral Inducers: Enantioselective Catalysis and Transmission Electron Microscopy 3D Characterization.

    Science.gov (United States)

    Kaushik, Madhu; Basu, Kaustuv; Benoit, Charles; Cirtiu, Ciprian M; Vali, Hojatollah; Moores, Audrey

    2015-05-20

    Cellulose nanocrystals (CNCs), derived from cellulose, provide us with an opportunity to devise more sustainable solutions to current technological challenges. Enantioselective catalysis, especially heterogeneous, is the preferred method for the synthesis of pure chiral molecules in the fine chemical industries. Cellulose has been long sought as a chiral inducer in enantioselective catalysis. We report herein an unprecedentedly high enantiomeric excess (ee) for Pd patches deposited onto CNCs used as catalysts for the hydrogenation of prochiral ketones in water at room temperature and 4 bar H2. Our system, where CNCs acted as support and sole chiral source, achieved an ee of 65% with 100% conversions. Cryo-electron microscopy, high-resolution transmission electron microscopy, and tomography were used for the first time to study the 3D structure of a metal functionalized CNC hybrid. It established the presence of sub-nanometer-thick Pd patches at the surface of CNCs and provided insight into the chiral induction mechanism.

  13. Consistent Chiral Kinetic Theory in Weyl Materials: Chiral Magnetic Plasmons

    Science.gov (United States)

    Gorbar, E. V.; Miransky, V. A.; Shovkovy, I. A.; Sukhachov, P. O.

    2017-03-01

    We argue that the correct definition of the electric current in the chiral kinetic theory for Weyl materials should include the Chern-Simons contribution that makes the theory consistent with the local conservation of the electric charge in electromagnetic and strain-induced pseudoelectromagnetic fields. By making use of such a kinetic theory, we study the plasma frequencies of collective modes in Weyl materials in constant magnetic and pseudomagnetic fields, taking into account the effects of dynamical electromagnetism. We show that the collective modes are chiral plasmons. While the plasma frequency of the longitudinal collective mode coincides with the Langmuir one, this mode is unusual because it is characterized not only by oscillations of the electric current density, but also by oscillations of the chiral current density. The latter are triggered by a dynamical version of the chiral electric separation effect. We also find that the plasma frequencies of the transverse modes split up in a magnetic field. This finding suggests an efficient means of extracting the chiral shift parameter from the measurement of the plasma frequencies in Weyl materials.

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

    Science.gov (United States)

    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.)

  15. An Inherent Chiral Calix[4]arene Bearing Chiral Groups without Forming Sub-ring

    Institute of Scientific and Technical Information of China (English)

    Xian Xian LIU; Yan Song ZHENG; Wan Ling MO

    2006-01-01

    The NMR spectra revealed that the calixarene frame of 1, 3-disubstituted calix[4]arenes bearing optically active groups is asymmetric, even without the formation of a sub-ring. This inherent chirality arises from the interaction of the two chiral groups, which hinder the substituents' free rotation. Thus, these chiral calix[4]arenes display good chiral recognition ability.

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

    Science.gov (United States)

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

    2012-01-01

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

  17. Chirality of Sulforhodamine Dye Molecules Incorporated in DNA Thin Films

    Science.gov (United States)

    2008-11-13

    of the aqueous solution, but is soluble in simple organic solvents. Thin film formation by spin coating is markedly easier with organic solvents...filter. Solutions of 2.5, 5, 10, 15, 20, and 25 wt % SRh to DNA/CTMA were prepared. Thin films produced by spin coating were typically 1.5 m thick...The spin - coating process started by com- pletely flooding the substrate, followed by spreading the so- lution for 8 s at 300 rpm, a spin of 1 min at

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

    Science.gov (United States)

    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.

  19. Chaos of chiral condensate

    CERN Document Server

    Hashimoto, Koji; Yoshida, Kentaroh

    2016-01-01

    Assigning a chaos index for vacua of generic quantum field theories is a challenging problem. We find chaotic behavior of chiral condensates of a quantum gauge theory at strong coupling limit, by using the AdS/CFT correspondence. We evaluate the time evolution of homogeneous quark condensates and in an N=2 supersymmetric QCD with the SU(N_c) gauge group at large N_c and at large 't Hooft coupling lambda. At an equivalent classical gravity picture, a Lyapunov exponent is readily defined. We show that the condensates exhibit chaotic behavior for energy density E > (6x10^2) (N_c/lambda^2) (m_q)^4 where m_q is the quark mass. The energy region of the chaotic vacua of the N=2 supersymmetric QCD increases for smaller N_c or larger lambda. The Lyapunov exponent is calculated as a function of the theory (N_c,lambda,E), showing that the N=2 supersymmetric QCD is more chaotic for smaller N_c.

  20. Chirality-induced spin polarization places symmetry constraints on biomolecular interactions

    Science.gov (United States)

    Kumar, Anup; Capua, Eyal; Kesharwani, Manoj K.; Martin, Jan M. L.; Sitbon, Einat; Waldeck, David H.; Naaman, Ron

    2017-01-01

    Noncovalent interactions between molecules are key for many biological processes. Necessarily, when molecules interact, the electronic charge in each of them is redistributed. Here, we show experimentally that, in chiral molecules, charge redistribution is accompanied by spin polarization. We describe how this spin polarization adds an enantioselective term to the forces, so that homochiral interaction energies differ from heterochiral ones. The spin polarization was measured by using a modified Hall effect device. An electric field that is applied along the molecules causes charge redistribution, and for chiral molecules, a Hall voltage is measured that indicates the spin polarization. Based on this observation, we conjecture that the spin polarization enforces symmetry constraints on the biorecognition process between two chiral molecules, and we describe how these constraints can lead to selectivity in the interaction between enantiomers based on their handedness. Model quantum chemistry calculations that rigorously enforce these constraints show that the interaction energy for methyl groups on homochiral molecules differs significantly from that found for heterochiral molecules at van der Waals contact and shorter (i.e., ∼0.5 kcal/mol at 0.26 nm). PMID:28228525

  1. Chiral Thirring–Wess model

    Energy Technology Data Exchange (ETDEWEB)

    Rahaman, Anisur, E-mail: anisur.rahman@saha.ac.in

    2015-10-15

    The vector type of interaction of the Thirring–Wess model was replaced by the chiral type and a new model was presented which was termed as chiral Thirring–Wess model in Rahaman (2015). The model was studied there with a Faddeevian class of regularization. Few ambiguity parameters were allowed there with the apprehension that unitarity might be threatened like the chiral generation of the Schwinger model. In the present work it has been shown that no counter term containing the regularization ambiguity is needed for this model to be physically sensible. So the chiral Thirring–Wess model is studied here without the presence of any ambiguity parameter and it has been found that the model not only remains exactly solvable but also does not lose the unitarity like the chiral generation of the Schwinger model. The phase space structure and the theoretical spectrum of this new model have been determined in the present scenario. The theoretical spectrum is found to contain a massive boson with ambiguity free mass and a massless boson.

  2. Chiral Logs in Quenched QCD

    CERN Document Server

    Dong, S J; Horváth, I; Lee, F X; Liu, K F; Mathur, N; Zhang, J B

    2003-01-01

    The quenched chiral logs are examined on a $16^3 \\times 28$ lattice with Iwasaki gauge action and overlap fermions. The pion decay constant $f_{\\pi}$ is used to set the lattice spacing, $a = 0.200(3)$ fm. With pion mass as low as $\\sim 180 {\\rm MeV}$, we see the quenched chiral logs clearly in $m_{\\pi}^2/m$ and $f_P$, the pseudoscalar decay constant. We analyze the data to determine how low the pion mass needs to be in order for the quenched one-loop chiral perturbation theory ($\\chi$PT) to apply. With the constrained curve fitting, we are able to extract the quenched chiral log parameter $\\delta$ together with the chiral cutoff $\\Lambda_{\\chi}$ and other parameters. Only for $m_{\\pi} \\leq 300 {\\rm MeV}$ do we obtain a consistent and stable fit with a constant $\\delta$ which we determine to be 0.23(2). By comparing to the $12^3 \\times 28$ lattice, we estimate the finite volume effect to be about 1.8% for the smallest pion mass. We also study the quenched non-analytic terms in the nucleon and the $\\rho$ masses...

  3. Orientation-dependent handedness and chiral design

    OpenAIRE

    Efrati, Efi; Irvine, William T. M.

    2013-01-01

    Chirality occupies a central role in fields ranging from biological self-assembly to the design of optical metamaterials. The definition of chirality, as given by Lord Kelvin, associates chirality with the lack of mirror symmetry: the inability to superpose an object on its mirror image. While this definition has guided the classification of chiral objects for over a century, the quantification of handed phenomena based on this definition has proven elusive, if not impossible, as manifest in ...

  4. Chiral Decomposition For Non-Abelian Bosons

    CERN Document Server

    Braga, N R F; Braga, Nelson R. F.; Wotzasek, Clovis

    1996-01-01

    We study the non-abelian extension for the splitting of a scalar field into chiral components. Using this procedure we find a non ambiguous way of coupling a non abelian chiral scalar field to gravity. We start with a (non-chiral) WZW model covariantly coupled to a background metric and, after the splitting, arrive at two chiral Wess-Zumino-Witten (WZW) models coupled to gravity.

  5. Chiral gap effect in curved space

    CERN Document Server

    Flachi, Antonino

    2014-01-01

    We discuss a new type of QCD phenomenon induced in curved space. In the QCD vacuum a mass gap of Dirac fermions is attributed to the spontaneous breaking of chiral symmetry. If the curvature is positive large, the chiral condensate melts but a chiral invariant mass gap can still remain, which we name the chiral gap effect in curved space. This leads to decoupling of quark deconfinement which implies a view of black holes surrounded by a first-order QCD phase transition.

  6. Chirality: a relational geometric-physical property.

    Science.gov (United States)

    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.

  7. Bifurcated, modular syntheses of chiral annulet triazacyclononanes.

    Science.gov (United States)

    Argouarch, Gilles; Stones, Graham; Gibson, Colin L; Kennedy, Alan R; Sherrington, David C

    2003-12-21

    Three chiral 2,6-disubstituted tri-N-methyl azamacrocycles have been prepared by modular methods. These macrocycles were accessed from three chiral 1,4,7-triazaheptanes intermediates that were prepared by two independent routes. The first of these routes involved the benzylamine opening of chiral tosyl aziridines followed by debenzylation but was problematic on solubility grounds. A second, more effective, route was developed which avoided debenzylation by using ammonia in the nucleophilic opening of chiral tosyl aziridines.

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

    Science.gov (United States)

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

    2013-09-01

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

  9. Field induced spin chirality and chirality switching in magnetic multilayers

    Science.gov (United States)

    Tartakovskaya, Elena V.

    2015-05-01

    The physical origin of the field-induced spin chirality experimentally observed in rare earth multilayers is determined. It is shown that the effect is possible due to the interplay between solid-state exchange interactions (the Ruderman-Kittel-Kasuya-Yosida and the Dsyaloshinsky-Moriya interactions), the external magnetic field and a special confinement of magnetic constituents. The presented model describes a certain temperature dependence of the chirality factor in agreement with experimental data and opens a new way to design nanostructured objects with predicted handedness.

  10. Chiral dynamics of baryons in the perturbative chiral quark model

    Energy Technology Data Exchange (ETDEWEB)

    Pumsa-ard, K.

    2006-07-01

    In this work we develop and apply variants of a perturbative chiral quark model (PCQM) to the study of baryonic properties dominantly in the low-energy region. In a first step we consider a noncovariant form of the PCQM, where confinement is modelled by a static, effective potential and chiral corrections are treated to second order, in line with similar chiral quark models. We apply the PCQM to the study of the electromagnetic form factors of the baryon octet. We focus in particular on the low-energy observables such as the magnetic moments, the charge and magnetic radii. In addition, the electromagnetic N-delta transition is also studied in the framework of the PCQM. In the chiral loop calculations we consider a quark propagator, which is restricted to the quark ground state, or in hadronic language to nucleon and delta intermediate states, for simplicity. We furthermore include the low-lying excited states to the quark propagator. In particular, the charge radius of the neutron and the transverse helicity amplitudes of the N-delta transition are considerably improved by this additional effect. In a next step we develop a manifestly Lorentz covariant version of the PCQM, where in addition higher order chiral corrections are included. The full chiral quark Lagrangian is motivated by and in analogy to the one of Chiral Perturbation Theory (ChPT). This Lagrangian contains a set of low energy constants (LECs), which are parameters encoding short distance effects and heavy degrees of freedom. We evaluate the chiral Lagrangian to order O(p{sup 4}) and to one loop to generate the dressing of the bare quark operators by pseudoscalar mesons. In addition we include the vector meson degrees of freedom in our study. Projection of the dressed quark operators on the baryonic level serves to calculate the relevant matrix elements. In a first application of this scheme, we resort to a parameterization of the valence quark form factors in the electromagnetic sector. Constraints

  11. Neutrino Oscillation Induced by Chiral Phase Transition

    Institute of Scientific and Technical Information of China (English)

    MU Cheng-Fu; SUN Gao-Feng; ZHUANG Peng-Fei

    2009-01-01

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

  12. Quenched Chiral Perturbation Theory to one loop

    NARCIS (Netherlands)

    Colangelo, G.; Pallante, E.

    1998-01-01

    The divergences of the generating functional of quenched Chiral Perturbation theory (qCHPT) to one loop are computed in closed form. We show how the quenched chiral logarithms can be reabsorbed in the renormalization of the B0 parameter of the leading order Lagrangian. Finally, we do the chiral powe

  13. Shear Viscosity of Turbulent Chiral Plasma

    CERN Document Server

    Kumar, Avdhesh; Das, Amita; Kaw, P K

    2016-01-01

    It is well known that the difference between the chemical potentials of left-handed and right-handed particles in a parity violating (chiral) plasma can lead to an instability. We show that the chiral instability may drive turbulent transport. Further we estimate the anomalous viscosity of chiral plasma arising from the enhanced collisionality due to turbulence.

  14. Exact Chiral Symmetry on the Lattice

    CERN Document Server

    Neuberger, H

    2001-01-01

    Developments during the last eight years have refuted the folklore that chiral symmetries cannot be preserved on the lattice. The mechanism that permits chiral symmetry to coexist with the lattice is quite general and may work in Nature as well. The reconciliation between chiral symmetry and the lattice is likely to revolutionize the field of numerical QCD.

  15. Chirality and gravitational parity violation.

    Science.gov (United States)

    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.

  16. Synthetic Applications of Chiral Furanboronate

    Institute of Scientific and Technical Information of China (English)

    CHAN KinFai; WONG Henry N,C.

    2001-01-01

    @@ We recently uncovered that consecutive reactions of chiral furfural-boronate 1 with a lithium alkoxide and a nucleophile led to the formation of alcohols 2 with good diastereoselection in favor of S-configuration at the newly generated chiral carbon. In addition, it was also found that 2a and 2b were chromatographically separable on a silica gel column. This reaction is believed to involve a tetrahedral borate intermediate, as can be substantiated by 11BNMR spectroscopic studies. Chiral furanmethanolboronates 2a(or 2b) underwent a palladium-catalyzed Suzuki coupling to form enantiomerically pure furans 3, which can be further converted to the synthetically useful hydroxypyranones 4.1,2,3 In addition, Mukaiyama reaction of 1 also led to chromatographically separable diastereomeric aldol-products. The scope and limitation of these conversions will be discussed.

  17. Synthetic Applications of Chiral Furanboronate

    Institute of Scientific and Technical Information of China (English)

    CHAN; KinFai

    2001-01-01

    We recently uncovered that consecutive reactions of chiral furfural-boronate 1 with a lithium alkoxide and a nucleophile led to the formation of alcohols 2 with good diastereoselection in favor of S-configuration at the newly generated chiral carbon. In addition, it was also found that 2a and 2b were chromatographically separable on a silica gel column. This reaction is believed to involve a tetrahedral borate intermediate, as can be substantiated by 11BNMR spectroscopic studies. Chiral furanmethanolboronates 2a(or 2b) underwent a palladium-catalyzed Suzuki coupling to form enantiomerically pure furans 3, which can be further converted to the synthetically useful hydroxypyranones 4.1,2,3 In addition, Mukaiyama reaction of 1 also led to chromatographically separable diastereomeric aldol-products. The scope and limitation of these conversions will be discussed.  ……

  18. Chiral separation of agricultural fungicides.

    Science.gov (United States)

    Pérez-Fernández, Virginia; García, Maria Ángeles; Marina, Maria Luisa

    2011-09-23

    Fungicides are very important and diverse environmental and agricultural concern species. Their determination in commercial formulations or environmental matrices, requires highly efficient, selective and sensitive methods. A significant number of these chemicals are chiral with the activity residing usually in one of the enantiomers. The different toxicological and degradation behavior observed in many cases for fungicide enantiomers, results in the need to investigate them separately. For this purpose, separation techniques such as GC, HPLC, supercritical fluid chromatography (SFC) and CE have widely been employed although, at present, HPLC still dominates chromatographic chiral analysis of fungicides. This review covers the literature concerning the enantiomeric separation of fungicides usually employed in agriculture grouping the chiral separation methodologies developed for their analysis in environmental, biological, and food samples.

  19. Application of computational chemistry methods to the prediction of chirality and helical twisting power in liquid crystal systems

    Science.gov (United States)

    Noto, Anthony G.; Marshall, Kenneth L.

    2005-08-01

    Until recently, it has not been possible to determine, with any real certainty, a complete picture of "chirality" (absolute configuration, optical rotation direction, and helical twisting power) for new chiral compounds without first synthesizing, purifying, characterizing, and testing every new material. Recent advances in computational chemistry now allow the prediction of certain key chiral molecular properties prior to synthesis, which opens the possibility of predetermining the "chiroptical" properties of new liquid crystal dopants and mixtures for advanced optical and photonics applications. A key element to this activity was the development of both the chirality index (G0) by Osipov et al., and the scaled chirality index (G0S) by Solymosi et al., that can be used as a "figure of merit" for molecular chirality. Promising correlations between G0S and both circular dichroism (CD) and the helical twisting power (HTP) of a chiral dopant in a liquid crystal host have been shown by Neal et al., Osipov, and Kuball. Our work improves the predictive capabilities of G0S by taking into account the actual mass of each atom in the molecule in the calculations; in previous studies the mass of each atom was assumed to be equal. This "weighted" scaled chirality index (G0SW) was calculated and correlated to existing experimental HTP data for each member of a series of existing, well-known chiral compounds. The computed HTP using G0SW for these model systems correlated to the experimental data with remarkable accuracy. Weighted, scaled chiral indices were also calculated for the first time for a series of novel chiral transition metal dithiolene dyes for near-IR liquid crystal device applications.

  20. Surface Chirality of Gly-Pro Dipeptide Adsorbed on a Cu(110) Surface.

    Science.gov (United States)

    Cruguel, Hervé; Méthivier, Christophe; Pradier, Claire-Marie; Humblot, Vincent

    2015-07-01

    The adsorption of chiral Gly-Pro dipeptide on Cu(110) has been characterized by combining in situ polarization modulation infrared reflection absorption spectroscopy (PM-RAIRS) and X-ray photoelectron spectroscopy (XPS). The chemical state of the dipeptide, and its anchoring points and adsorption geometry, were determined at various coverage values. Gly-Pro molecules are present on Cu(110) in their anionic form (NH2 /COO(-)) and adsorb under a 3-point binding via both oxygen atoms of the carboxylate group and via the nitrogen atom of the amine group. Low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) have shown the presence of an extended 2D chiral array, sustained via intermolecular H-bonds interactions. Furthermore, due to the particular shape of the molecule, only one homochiral domain is formed, creating thus a truly chiral surface.

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

    Science.gov (United States)

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

    2007-05-05

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

  2. On superconductivity of matter at hight density and the effects of inducing nuclear chirality in molecular structures

    DEFF Research Database (Denmark)

    da Providëncia, J.; Jalkanen, Karl J.; Bohr, Henrik

    2013-01-01

    relativistic fluid of elementary particles is studied. We find that the magnetic field of spin polarized matter with densities of 2 to 30, where 0 is the equilibrium density of nuclear matter, is rather huge, of the order of 1017 Gauss. Finally we look at the chiral nature of nuclear forces and interactions...... as they possibly relate to chirality of nuclei (atoms) in molecules as a source of chirality in amino acids and hence in life. Previous works have not investigated the nuclear forces as a possible bias which initiated the bias towards L-amino acids as the building blocks on proteins, and later life....

  3. Novel Chiral Auxiliaries of BIAZOLs

    Institute of Scientific and Technical Information of China (English)

    CHEN; Arh-Hwang

    2001-01-01

    Asymmetric catalysis is one of the most challenging and formidable endeavor in organic synthesis. The development of chiral auxiliaries is a key in the asymmetric catalysis. Azulenoids, a parent structure of bicyclo[5.3.0]decapentaene with 10 πelectrons, are useful as dye materials, medical treatment of inflammation and hypertension, and the development of liquid crystals. In continuing to investigate synthetic application of azulenoids, we have studied to develop novel chiral auxiliaries of BIAZOLs. The BIAZOLs were synthesized from dicyclopentadiene and characterized using spectroscopies.  ……

  4. Novel Chiral Auxiliaries of BIAZOLs

    Institute of Scientific and Technical Information of China (English)

    CHEN Arh-Hwang; YUAN Shou-Bin; CHIU Shu-Ching

    2001-01-01

    @@ Asymmetric catalysis is one of the most challenging and formidable endeavor in organic synthesis. The development of chiral auxiliaries is a key in the asymmetric catalysis. Azulenoids, a parent structure of bicyclo[5.3.0]decapentaene with 10 πelectrons, are useful as dye materials, medical treatment of inflammation and hypertension, and the development of liquid crystals. In continuing to investigate synthetic application of azulenoids, we have studied to develop novel chiral auxiliaries of BIAZOLs. The BIAZOLs were synthesized from dicyclopentadiene and characterized using spectroscopies.

  5. Asymmetric Synthesis via Chiral Aziridines

    DEFF Research Database (Denmark)

    Tanner, David Ackland; Harden, Adrian; Wyatt, Paul

    1996-01-01

    A series of chiral bis(aziridines) has been synthesised and evaluated as chelating ligands for a variety of asymmetric transformations mediated by metals [Os (dihydroxylation), Pd (allylic alkylation) Cu (cyclopropanation and aziridination, Li (1,2-addition of organolithiums to imines)]. In the b......A series of chiral bis(aziridines) has been synthesised and evaluated as chelating ligands for a variety of asymmetric transformations mediated by metals [Os (dihydroxylation), Pd (allylic alkylation) Cu (cyclopropanation and aziridination, Li (1,2-addition of organolithiums to imines...

  6. Collisions in Chiral Kinetic Theory

    CERN Document Server

    Chen, Jing-Yuan; Stephanov, Mikhail A

    2015-01-01

    Using a covariant formalism, we construct a chiral kinetic theory Lorentz invariant to order $\\mathcal O(\\hbar)$ which includes collisions. We find a new contribution to the particle number current due to the side jumps required by the conservation of angular momentum during collisions. We also find a conserved symmetric stress-energy tensor as well as the $H$-function obeying Boltzmann's $H$-theorem. We demonstrate their use by finding a general equilibrium solution and the values of the anomalous transport coefficients characterizing chiral vortical effect.

  7. Strange chiral nucleon form factors

    CERN Document Server

    Hemmert, T R; Meißner, Ulf G; Hemmert, Thomas R.; Kubis, Bastian; Meissner, Ulf-G.

    1999-01-01

    We investigate the strange electric and magnetic form factors of the nucleon in the framework of heavy baryon chiral perturbation theory to third order in the chiral expansion. All counterterms can be fixed from data. In particular, the two unknown singlet couplings can be deduced from the parity-violating electron scattering experiments performed by the SAMPLE and the HAPPEX collaborations. Within the given uncertainties, our analysis leads to a small and positive electric strangeness radius, $ = (0.05 \\pm 0.16) fm^2$. We also deduce the consequences for the upcoming MAMI A4 experiment.

  8. Dynamic chirality, chirality transfer and aggregation behaviour of dithienylethene switches

    NARCIS (Netherlands)

    de Jong, Jaap J. D.; van Rijn, Patrick; Tiemersma-Wegeman, Theodora D.; Lucas, Linda N.; Browne, Wesley R.; Kellogg, Richard M.; Uchida, Kingo; Van Esch, Jan H.; Feringa, Ben L.

    2008-01-01

    The synthesis and characterisation of a series of chiral and achiral low molecular weight organogelators (LMWGs) based on bis-amide substituted dithienylethene photochromic switches is reported. The LMWGs gelate a range of solvents depending on the specific functionalisation of the hydrogen bonding

  9. K stability and stability of chiral ring

    CERN Document Server

    Collins, Tristan C; Yau, Shing-Tung

    2016-01-01

    We define a notion of stability for chiral ring of four dimensional N=1 theory by introducing test chiral rings and generalized a maximization. We conjecture that a chiral ring is the chiral ring of a superconformal field theory if and only if it is stable. We then study N=1 field theory derived from D3 branes probing a three-fold singularity X, and show that the K stability which implies the existence of Ricci-flat conic metric on X is equivalent to the stability of chiral ring of the corresponding field theory.

  10. Thermal chiral vortical and magnetic waves: new excitation modes in chiral fluids

    CERN Document Server

    Kalaydzhyan, Tigran

    2016-01-01

    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. We study first-order hydrodynamics of a chiral fluid on a vortex background and in a 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, the chiral vortical and chiral magnetic waves. We demonstrate that the velocity of the chiral vortical wave is zero, when the full hydrodynamic framework is applied, and hence the excitation reduces to a charge diffusion mode or is completely absent. We also correct the dispersion relation for the chiral magnetic wave.

  11. Chiral magnetic plasmons in anomalous relativistic matter

    CERN Document Server

    Gorbar, E V; Shovkovy, I A; Sukhachov, P O

    2016-01-01

    The chiral plasmon modes of relativistic matter in background magnetic and strain-induced pseudomagnetic fields are studied in detail using the consistent chiral kinetic theory. The results reveal a number of anomalous features of these chiral magnetic and pseudomagnetic plasmons that could be used to identify them in experiment. In a system with nonzero electric (chiral) chemical potential, the background magnetic (pseudomagnetic) fields not only modify the values of the plasmon frequencies in the long wavelength limit, but also affect the qualitative dependence on the wave-vector. Similar modifications can be also induced by the chiral shift parameter in Weyl materials. Interestingly, even in the absence of the chiral shift and external fields, the chiral chemical potential alone leads to a splitting of plasmon energies at linear order in the wave vector.

  12. A Chiral Macroscopic Force between Liquid of Butyl Alcohol and Copper Block

    Institute of Scientific and Technical Information of China (English)

    HU Yong-Hong; LIU Zhong-Zhu

    2008-01-01

    A non-zero macroscopic chirality-dependent force between a copper block and a vessel of homochiral molecules(butyl alcohol) is calculated quantitatively with the central field approximation. The magnitude of the force is estimated with the published limits of the scalar and pseudo-scalar coupling constants.

  13. Reversal of helicoidal twist handedness near point defects of confined chiral liquid crystals

    Science.gov (United States)

    Ackerman, Paul J.; Smalyukh, Ivan I.

    2016-05-01

    Handedness of the director twist in cholesteric liquid crystals is commonly assumed to be the same throughout the medium, determined solely by the chirality of constituent molecules or chiral additives, albeit distortions of the ground-state helicoidal configuration often arise due to the effects of confinement and external fields. We directly probe the twist directionality of liquid crystal director structures through experimental three-dimensional imaging and numerical minimization of the elastic free energy and show that spatially localized regions of handedness opposite to that of the chiral liquid crystal ground state can arise in the proximity of twisted-soliton-bound topological point defects. In chiral nematic liquid crystal confined to a film that has a thickness less than the cholesteric pitch and perpendicular surface boundary conditions, twisted solitonic structures embedded in a uniform unwound far-field background with chirality-matched handedness locally relieve confinement-imposed frustration and tend to be accompanied by point defects and smaller geometry-required, energetically costly regions of opposite twist handedness. We also describe a spatially localized structure, dubbed a "twistion," in which a twisted solitonic three-dimensional director configuration is accompanied by four point defects. We discuss how our findings may impinge on the stability of localized particlelike director field configurations in chiral and nonchiral liquid crystals.

  14. Application of modified amino acid as a chiral building block in asymmetric synthesis

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Phenylglycine 1 as a representative of natural resourceful (-amino acid was modified by reduction and protection of functional group to afford the amino alcohol as a chiral building block 3. A new chiral compound, the chiral building block/spiro-cyclopropane derivative containing four stereogenic centers, compound 7, has been obtained in 52% yield with de≥98% via the tandem double Michael addition/internal nucleophilic substitution under mild condition of 5-l-menthyloxy-3-bromo-2-(5H)-furanone 4 with the nucleophilic reagent, the amino alcohol 3. The new chiral compound 7 is identified on the basis of its analytical data and spectroscopic data, such as UV, IR, 1H NMR, 13C NMR, MS and elementary analysis. The absolute configuration of the interesting spiro-cyclopropanes 7 was established by X-ray crystallography. This result can provide new route and method for the introduction of chiral building block and the important synthetic strategy in synthesis of some complex molecules containing spiro-cyclopropane skeleton with multiple chiral centers and the study of their biological activity.

  15. Algebraic study of chiral anomalies

    Indian Academy of Sciences (India)

    Juan Mañes; Raymond Stora; Bruno Zumino

    2012-06-01

    The algebraic structure of chiral anomalies is made globally valid on non-trivial bundles by the introduction of a fixed background connection. Some of the techniques used in the study of the anomaly are improved or generalized, including a systematic way of generating towers of ‘descent equations’.

  16. Chiral Perturbation Theory and Unitarization

    CERN Document Server

    Ruiz-Arriola, E; Nieves, J; Peláez, J R

    2000-01-01

    We review our recent work on unitarization and chiral perturbation theory both in the $\\pi\\pi$ and the $\\pi N$ sectors. We pay particular attention to the Bethe-Salpeter and Inverse Amplitude unitarization methods and their recent applications to $\\pi\\pi$ and $\\pi N$ scattering.

  17. Multipolar Effects in the Optical Active Second Harmonic Generation from Sawtooth Chiral Metamaterials.

    Science.gov (United States)

    Su, Huimin; Guo, Yuxiang; Gao, Wensheng; Ma, Jie; Zhong, Yongchun; Tam, Wing Yim; Chan, C T; Wong, Kam Sing

    2016-02-25

    Based on the facts that chiral molecules response differently to left- and right-handed circular polarized light, chiroptical effects are widely employed for determining structure chirality, detecting enantiomeric excess, or controlling chemical reactions of molecules. Compared to those in natural materials, chiroptical behaviors can be significantly amplified in chiral plasmonic metamaterials due to the concentrated local fields in the structure. The on-going research towards giant chiroptical effects in metamaterial generally focus on optimizing the field-enhancement effects. However, the observed chiroptical effects in metamaterials rely on more complicated factors and various possibilities towards giant chiroptical effects remains unexplored. Here we study the optical-active second harmonic generation (SHG) behaviors in a pair of planar sawtooth gratings with mirror-imaged patterns. Significant multipolar effects were observed in the polarization-dependent SHG curves. We show that the chirality of the nanostructure not only give rise to nonzero chiral susceptibility tensor components within the electric-dipole approximation, but also lead to different levels of multipolar interactions for the two orthogonal circular polarizations that further enhance the nonlinear optical activity of the material. Our results thus indicate novel ways to optimize nonlinear plasmonic structures and achieve giant chiroptical response via multipolar interactions.

  18. Chiral non-Fermi liquids

    Science.gov (United States)

    Sur, Shouvik; Lee, Sung-Sik

    2014-07-01

    A non-Fermi liquid state without time-reversal and parity symmetries arises when a chiral Fermi surface is coupled with a soft collective mode in two space dimensions. The full Fermi surface is described by a direct sum of chiral patch theories, which are decoupled from each other in the low-energy limit. Each patch includes low-energy excitations near a set of points on the Fermi surface with a common tangent vector. General patch theories are classified by the local shape of the Fermi surface, the dispersion of the critical boson, and the symmetry group, which form the data for distinct universality classes. We prove that a large class of chiral non-Fermi liquid states exists as stable critical states of matter. For this, we use a renormalization group scheme where low-energy excitations of the Fermi surface are interpreted as a collection of (1+1)-dimensional chiral fermions with a continuous flavor labeling the momentum along the Fermi surface. Due to chirality, the Wilsonian effective action is strictly UV finite. This allows one to extract the exact scaling exponents although the theories flow to strongly interacting field theories at low energies. In general, the low-energy effective theory of the full Fermi surface includes patch theories of more than one universality classes. As a result, physical responses include multiple universal components at low temperatures. We also point out that, in quantum field theories with extended Fermi surface, a noncommutative structure naturally emerges between a coordinate and a momentum which are orthogonal to each other. We show that the invalidity of patch description for Fermi liquid states is tied with the presence of UV/IR mixing associated with the emergent noncommutativity. On the other hand, UV/IR mixing is suppressed in non-Fermi liquid states due to UV insensitivity, and the patch description is valid.

  19. Nuclear chiral dynamics and thermodynamics

    Science.gov (United States)

    Holt, Jeremy W.; Kaiser, Norbert; Weise, Wolfram

    2013-11-01

    This presentation reviews an approach to nuclear many-body systems based on the spontaneously broken chiral symmetry of low-energy QCD. In the low-energy limit, for energies and momenta small compared to a characteristic symmetry breaking scale of order 1 GeV, QCD is realized as an effective field theory of Goldstone bosons (pions) coupled to heavy fermionic sources (nucleons). Nuclear forces at long and intermediate distance scales result from a systematic hierarchy of one- and two-pion exchange processes in combination with Pauli blocking effects in the nuclear medium. Short distance dynamics, not resolved at the wavelengths corresponding to typical nuclear Fermi momenta, are introduced as contact interactions between nucleons. Apart from a set of low-energy constants associated with these contact terms, the parameters of this theory are entirely determined by pion properties and low-energy pion-nucleon scattering observables. This framework (in-medium chiral perturbation theory) can provide a realistic description of both isospin-symmetric nuclear matter and neutron matter, with emphasis on the isospin-dependence determined by the underlying chiral NN interaction. The importance of three-body forces is emphasized, and the role of explicit Δ(1232)-isobar degrees of freedom is investigated in detail. Nuclear chiral thermodynamics is developed and a calculation of the nuclear phase diagram is performed. This includes a successful description of the first-order phase transition from a nuclear Fermi liquid to an interacting Fermi gas and the coexistence of these phases below a critical temperature Tc. Density functional methods for finite nuclei based on this approach are also discussed. Effective interactions, their density dependence and connections to Landau Fermi liquid theory are outlined. Finally, the density and temperature dependences of the chiral (quark) condensate are investigated.

  20. Synthesis of racemic and chiral BEDT-TTF derivatives possessing hydroxy groups and their achiral and chiral charge transfer complexes

    Directory of Open Access Journals (Sweden)

    Sara J. Krivickas

    2015-09-01

    Full Text Available Chiral molecular crystals built up by chiral molecules without inversion centers have attracted much interest owing to their versatile functionalities related to optical, magnetic, and electrical properties. However, there is a difficulty in chiral crystal growth due to the lack of symmetry. Therefore, we made the molecular design to introduce intermolecular hydrogen bonds in chiral crystals. Racemic and enantiopure bis(ethylenedithiotetrathiafulvalene (BEDT-TTF derivatives possessing hydroxymethyl groups as the source of hydrogen bonds were designed. The novel racemic trans-vic-(hydroxymethyl(methyl-BEDT-TTF 1, and racemic and enantiopure trans-vic-bis(hydroxymethyl-BEDT-TTF 2 were synthesized. Moreover, the preparations, crystal structure analyses, and electrical resistivity measurements of the novel achiral charge transfer salt θ21-[(S,S-2]3[(R,R-2]3(ClO42 and the chiral salt α’-[(R,R-2]ClO4(H2O were carried out. In the former θ21-[(S,S-2]3[(R,R-2]3(ClO42, there are two sets of three crystallographically independent donor molecules [(S,S-2]2[(R,R-2] in a unit cell, where the two sets are related by an inversion center. The latter α’-[(R,R-2]ClO4(H2O is the chiral salt with included solvent H2O, which is not isostructural with the reported chiral salt α’-[(S,S-2]ClO4 without H2O, but has a similar donor arrangement. According to the molecular design by introduction of hydroxy groups and a ClO4− anion, many intermediate-strength intermolecular hydrogen bonds (2.6–3.0 Å were observed in these crystals between electron donor molecules, anions, and included H2O solvent, which improve the crystallinity and facilitate the extraction of physical properties. Both salts are semiconductors with relatively low resistivities at room temperature and activation energies of 1.2 ohm cm with Ea = 86 meV for θ21-[(S,S-2]3[(R,R-2]3(ClO42 and 0.6 ohm cm with Ea = 140 meV for α'-[(R,R-2]2ClO4(H2O, respectively. The variety of donor arrangements

  1. Oriented circular dichroism analysis of chiral surface-anchored metal-organic frameworks grown by liquid-phase epitaxy and upon loading with chiral guest compounds

    KAUST Repository

    Gu, Zhigang

    2014-06-17

    Oriented circular dichroism (OCD) is explored and successfully applied to investigate chiral surface-anchored metal-organic frameworks (SURMOFs) based on camphoric acid (D- and Lcam) with the composition [Cu2(Dcam) 2x(Lcam)2-2x(dabco)]n (dabco=1,4-diazabicyclo- [2.2.2]-octane). The three-dimensional chiral SURMOFs with high-quality orientation were grown on quartz glass plates by using a layer-by-layer liquid-phase epitaxy method. The growth orientation, as determined by X-ray diffraction (XRD), could be switched between the [001] and [110] direction by using either OH- or COOH-terminated substrates. These SURMOFs were characterized by using OCD, which confirmed the ratio as well as the orientation of the enantiomeric linker molecules. Theoretical computations demonstrate that the OCD band intensities of the enantiopure [Cu2(Dcam)2(dabco)] n grown in different orientations are a direct result of the anisotropic nature of the chiral SURMOFs. Finally, the enantiopure [Cu 2(Dcam)2(dabco)]n and [Cu2(Lcam) 2(dabco)]n SURMOFs were loaded with the two chiral forms of ethyl lactate [(+)-ethyl-D-lactate and (-)-ethyl-L-lactate)]. An enantioselective enrichment of >60 % was observed by OCD when the chiral host scaffold was loaded from the racemic mixture. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Enumerating molecules.

    Energy Technology Data Exchange (ETDEWEB)

    Visco, Donald Patrick, Jr. (, . Tennessee Technological University, Cookeville, TN); Faulon, Jean-Loup Michel; Roe, Diana C.

    2004-04-01

    This report is a comprehensive review of the field of molecular enumeration from early isomer counting theories to evolutionary algorithms that design molecules in silico. The core of the review is a detail account on how molecules are counted, enumerated, and sampled. The practical applications of molecular enumeration are also reviewed for chemical information, structure elucidation, molecular design, and combinatorial library design purposes. This review is to appear as a chapter in Reviews in Computational Chemistry volume 21 edited by Kenny B. Lipkowitz.

  3. Molecular chirality and chiral capsule-type dimer formation of cyclic triamides via hydrogen-bonding interactions.

    Science.gov (United States)

    Fujimoto, Noriko; Matsumura, Mio; Azumaya, Isao; Nishiyama, Shizuka; Masu, Hyuma; Kagechika, Hiroyuki; Tanatani, Aya

    2012-05-18

    Chiral properties of bowl-shaped cyclic triamides bearing functional groups with hydrogen-bonding ability were examined. Chiral induction of cyclic triamide 3a was observed by addition of chiral amine in solution, and chiral separation was achieved by simple crystallization to afford chiral capsule-type dimer structure of 4a.

  4. Chiral Redox-Active Isosceles Triangles.

    Science.gov (United States)

    Nalluri, Siva Krishna Mohan; Liu, Zhichang; Wu, Yilei; Hermann, Keith R; Samanta, Avik; Kim, Dong Jun; Krzyaniak, Matthew D; Wasielewski, Michael R; Stoddart, J Fraser

    2016-05-11

    Designing small-molecule organic redox-active materials, with potential applications in energy storage, has received considerable interest of late. Herein, we report on the synthesis, characterization, and application of two rigid chiral triangles, each of which consist of non-identical pyromellitic diimide (PMDI) and naphthalene diimide (NDI)-based redox-active units. (1)H and (13)C NMR spectroscopic investigations in solution confirm the lower symmetry (C2 point group) associated with these two isosceles triangles. Single-crystal X-ray diffraction analyses reveal their rigid triangular prism-like geometries. Unlike previously investigated equilateral triangle containing three identical NDI subunits, both isosceles triangles do not choose to form one-dimensional supramolecular nanotubes by dint of [C-H···O] interaction-driven columnar stacking. The rigid isosceles triangle, composed of one NDI and two PMDI subunits, forms-in the presence of N,N-dimethylformamide-two different types of intermolecular NDI-NDI and NDI-PMDI π-π stacked dimers with opposite helicities in the solid state. Cyclic voltammetry reveals that both isosceles triangles can accept reversibly up to six electrons. Continuous-wave electron paramagnetic resonance and electron-nuclear double-resonance spectroscopic investigations, supported by density functional theory calculations, on the single-electron reduced radical anions of the isosceles triangles confirm the selective sharing of unpaired electrons among adjacent redox-active NDI subunit(s) within both molecules. The isosceles triangles have been employed as electrode-active materials in organic rechargeable lithium-ion batteries. The evaluation of the structure-performance relationships of this series of diimide-based triangles reveals that the increase in the number of NDI subunits, replacing PMDI ones, within the molecules improves the electrochemical cell performance of the batteries.

  5. Chiral extraction of ketoprofen enantiomers with chiral selector tartaric esters

    Institute of Scientific and Technical Information of China (English)

    ZHOU Dan; LIU Jia-jia; TANG Ke-wen; HUANG Ke-long

    2007-01-01

    Distribution behavior of ketoprofen enantiomers was examined in methanol aqueous and organic solvent mixture containing tartaric esters. The influence of length of alkyl chain of tartaric esters, concentration of L-tartaric esters and methanol aqueous, kind of organic solvent on partition ratio and separation factors was investigated. The results show that L-tartaric and D-tartaric esters have different chiral recognition abilities. S-ketoprofen is easily extracted by L-tartaric esters, and R-ketoprofen is easily extracted by D-tartaric esters. L-tartaric esters form more stable diastereomeric complexes with S-enantiomer than that with R-enantiomer. This distribution behavior is consistent with chiral recognition mechanism. With the increase of the concentration of tartaric ester from 0 to 0.3 mol/L, partition coefficient K and separation factor α increase. Also, the kind of organic solvent and the concentration of the methanol aqueous have significant influence on K and α.

  6. Spectral study of a chiral limit without chiral condensate

    CERN Document Server

    Bietenholz, Wolfgang

    2009-01-01

    Random Matrix Theory (RMT) has elaborated successful predictions for Dirac spectra in field theoretical models. However, a generic assumption by RMT has been a non-vanishing chiral condensate $\\Sigma$ in the chiral limit. Here we consider the 2-flavour Schwinger model, where this assumption does not hold. We simulated this model with dynamical overlap hypercube fermions, and entered terra incognita by analysing this Dirac spectrum. The usual RMT prediction for the unfolded level spacing distribution in a unitary ensemble is precisely confirmed. The microscopic spectrum does not perform a Banks-Casher plateau. Instead the obvious expectation is a density of the lowest eigenvalue $\\lambda_{1}$ which increases $\\propto \\lambda_{1}^{1/3}$. That would correspond to a scale-invariant parameter $\\propto \\lambda V^{3/4}$, which is, however, incompatible with our data. Instead we observe to high precision a scale-invariant parameter $z \\propto \\lambda V^{5/8}$. This surprising result implies a microscopic spectral den...

  7. Chiral Lagrangian and chiral quark model from confinement in QCD

    CERN Document Server

    Simonov, Yu A

    2015-01-01

    The effective chiral Lagrangian in both nonlocal form $L_{ECCL}$ and standard local form $L_{ECL}$ are derived in QCD using the confining kernel, obtained in the vacuum correlator formalism. As a result all coefficients of $L_{ECL}$ can be computed via $q\\bar q$ Green's functions. In the $p^2$ order of $L_{ECL}$ one obtains GOR relations and quark decay constants $f_a$ are calculated $a=1,...8$, while in the $p^4$ order the coefficients $L_1, L_2, L_3,L_4, L_5, L_6$ are obtained in good agreement with the values given by data. The chiral quark model is shown to be a simple consequence of $L_{ECCL}$ with defined coefficients. It is demonstrated that $L_{ECCL}$ gives an extension of the limiting low-energy Lagrangian $L_{ECL}$ to arbitrary momenta.

  8. Microwave modulation characteristics of twisted liquid crystals with chiral dopant

    Directory of Open Access Journals (Sweden)

    Rui Yuan

    2017-01-01

    Full Text Available Adding a chiral dopant in twisted nematic (TN liquid crystal cell can stabilize the orientation of liquid crystal molecules, particularly in high TN (HTN or super TN (STN liquid crystal cells. The difference in pitches in liquid crystal is induced by the chiral dopant, and these different pitches affect the orientation of liquid crystal director under an external applied voltage and influence the characteristics of microwave modulation. To illustrate this point, the microwave phase shift per unit length (MPSL versus voltage is calculated on the basis of the elastic theory of liquid crystal and the finite-difference iterative method. Enhancing the pitch induced by the chiral dopant in liquid crystal increases the MPSLs, but the stability of the twisted structures is decreased. Thus, appropriate pitches of 100d, 4d, and 2d can be applied in TN, HTN, and STN cells with cell gap d to enhance the characteristics of microwave modulation and stabilize the structures in twisted cell. This method can improve the characteristics of liquid crystal microwave modulators such that the operating voltage and the size of such phase shifters can be decreased.

  9. Chiral Analysis of Isopulegol by Fourier Transform Molecular Rotational Spectroscopy

    Science.gov (United States)

    Evangelisti, Luca; Seifert, Nathan A.; Spada, Lorenzo; Pate, Brooks

    2016-06-01

    Chiral analysis on molecules with multiple chiral centers can be performed using pulsed-jet Fourier transform rotational spectroscopy. This analysis includes quantitative measurement of diastereomer products and, with the three wave mixing methods developed by Patterson, Schnell, and Doyle (Nature 497, 475-477 (2013)), quantitative determination of the enantiomeric excess of each diastereomer. The high resolution features enable to perform the analysis directly on complex samples without the need for chromatographic separation. Isopulegol has been chosen to show the capabilities of Fourier transform rotational spectroscopy for chiral analysis. Broadband rotational spectroscopy produces spectra with signal-to-noise ratio exceeding 1000:1. The ability to identify low-abundance (0.1-1%) diastereomers in the sample will be described. Methods to rapidly identify rotational spectra from isotopologues at natural abundance will be shown and the molecular structures obtained from this analysis will be compared to theory. The role that quantum chemistry calculations play in identifying structural minima and estimating their spectroscopic properties to aid spectral analysis will be described. Finally, the implementation of three wave mixing techniques to measure the enantiomeric excess of each diastereomer and determine the absolute configuration of the enantiomer in excess will be described.

  10. ND^(*) and NB^(*) interactions in a chiral quark model

    CERN Document Server

    Yang, Dan; Zhang, Dan

    2015-01-01

    ND and ND^* interactions become a hot topic after the observation of new charmed hadrons \\Sigma_c(2800) and \\Lambda_c(2940)^+. In this letter, we have preliminary investigated S-wave ND and ND^* interactions with possible quantum numbers in the chiral SU(3) quark model and the extended chiral SU(3) quark model by solving the resonating group method equation. The numerical results show that the interactions between N and D or N and D^* are both attractive, which are mainly from \\sigma exchanges between light quarks. Further bound-state studies indicate the attractions are strong enough to form ND or ND^* molecules, except for (ND)_{J=3/2} and (ND^*)_{J=3/2} in the chiral SU(3) quark model. In consequence ND system with J=1/2 and ND^* system with J=3/2 in the extended SU(3) quark model could correspond to the observed \\Sigma_c(2800) and \\Lambda_c(2940)^+, respectively. Naturally, the same method can be applied to research NB and NB^* interactions, and similar conclusions obtained, i.e. NB and NB^* attractive fo...

  11. Chiral Recognition and Enantioseparation Mechanisms in Capillary Electrokinetic Chromatography

    Science.gov (United States)

    Chankvetadze, Bezhan

    This chapter deals with the basic theory of enantiomeric separations in electrokinetic chromatography (EKC) in general and with the relationships between the recognition and the separation of enantiomers in EKC, in particular. It is important to note that the dependence between recognition and separation is not as straightforward in EKC as it is in chromatographic separation techniques. Therefore, a clear understanding of these dependences is very important for the explanation of experimentally observed results, as well as for a design of new powerful separation systems, technologies, and materials. Cyclodextrins (CDs) are mainly discussed as chiral selectors not only because the author has a long-term experience of working with these multifunctional macrocycles but also because CDs belong to the most widely used chiral selectors in EKC. In addition, these materials are quite well-characterized molecules of medium size. In addition, CDs are used for separation of enantiomers almost in all analytical separation techniques, as well as for determination of the enantiomeric excess in nonseparation techniques such as nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry. This chapter does not address applications of chiral EKC in chemistry, pharmaceutical and biomedical, environmental, and food analyses.

  12. Focusing, Power Tunneling and Rejection from Chiral and/or Chiral Nihility/Nihility Metamaterials Layers

    CERN Document Server

    Shah, Syed Touseef Hussain; Syed, Aqeel A; Naqvi, Qaisar Abbas

    2013-01-01

    Focusing of electromagnetic plane wave from a large size paraboloidal reflector, composed of layers of chiral and/or chiral nihility metamaterials, has been studied us- ing Maslov's method. First, the transmission and reflection of electromagnetic plane wave from two parallel layers of chiral and/or chiral nihility metamaterials are cal- culated using transfer matrix method. The effects of change of angle of incidence, chirality parameters and impedances of layers are noted and discussed. Special cases by taking very large and small values of permittivity of second layer, while assuming value of corresponding chirality equal to zero, are also treated. These special cases are equivalent to reflection from a perfect electric conductor backed chiral layer and nihility backed chiral layer, respectively. Results of reflection from parallel layers have been utilized to study focusing from a large size paraboloidal reflector. The present study, on focusing from a paraboloidal re{\\deg}ector, not only unifies several ...

  13. The effect of carbon nanotubes on chiral chemical reactions

    Science.gov (United States)

    Rance, Graham A.; Miners, Scott A.; Chamberlain, Thomas W.; Khlobystov, Andrei N.

    2013-02-01

    The intrinsic helicity of carbon nanotubes influences the formation of chiral molecules in chemical reactions. A racemic mixture of P and M enantiomers of nanotubes affects the enantiomeric excess of the products of the autocatalytic Soai reaction proportional to the amount of nanotubes added in the reaction mixture. An intermediate complex formed between the nanotube and the organometallic reagent is essential and explains the observed correlation between the enantiomeric distribution of products and the curvature of the carbon nanostructure. This Letter establishes a key mechanism for harnessing the helicity of nanoscale carbon surfaces for preparative organic reactions.

  14. Wave propagation in a chiral fluid an undergraduate study

    CERN Document Server

    Garel, T

    2003-01-01

    We study the propagation of electromagnetic waves in a chiral fluid, where the molecules are described by a simplified version of the Kuhn coupled oscillator model. The eigenmodes of Maxwell's equations are circularly polarized waves. The application of a static magnetic field further leads to a magnetochiral term in the index of refraction of the fluid, which is independent of the wave polarization. A similar result holds when absorption is taken into account. Interference experiments and photochemical reactions have recently demonstrated the existence of the magnetochiral term. The comparison with Faraday rotation in an achiral fluid emphasizes the different symmetry properties of the two effects.

  15. Shape Selection in the Self-Assembly of Chiral Lipid Aggregates

    Science.gov (United States)

    Selinger, Robin; Selinger, Jonathan; Malanoski, Anthony; Schnur, Joel M.

    2004-03-01

    Many lipids and other biological materials self-assemble into helical or twisted membranes and tubules. The membrane shape is determined by a complex interplay between elastic forces and the orientation and chirality of the constituent molecules. We study this interplay through Monte Carlo simulations, using a mesoscale model of the self-assembly process. Our simulations show shape transitions as the membrane's elastic properties are varied. Remarkably, both right- and left-handed helical aggregates can form from a membrane of a single chirality, depending on the orientation of molecular tilt. We discuss application of these findings to help understand recent experiments.

  16. Diastereomeric resolution directed towards chirality determination focussing on gas-phase energetics of coordinated sodium dissociation

    Science.gov (United States)

    Kanie, Osamu; Shioiri, Yuki; Ogata, Koji; Uchida, Waka; Daikoku, Shusaku; Suzuki, Katsuhiko; Nakamura, Shinichiro; Ito, Yukishige

    2016-01-01

    Defining chiral centres is addressed by introducing a pair of chiral auxiliary groups. Ions of diastereomeric pairs of molecules could be distinguished utilising energy-resolved mass spectrometry, and the applicability of the method to a series of compounds carrying amine, carboxylic acid, alcohol, and all the amino acids was verified. The method was further strengthened by distinguishing diastereomeric ions that did not undergo fragmentation. Mass spectrometric evaluation of the dissociation process of adducted sodium cations from the diastereomeric precursors agreed with the theoretical calculations, indicating the potential usefulness of the method for the determination of absolute configurations. PMID:27040078

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

    Science.gov (United States)

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

    2012-11-01

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

  18. ENANTIOMERIC RATIOS OF CHIRAL PCB ATROPISOMERS IN RADIODATED SEDIMENT CORES

    Science.gov (United States)

    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...

  19. Spatial control of chirality in supramolecular aggregates

    Science.gov (United States)

    Castriciano, Maria A.; Gentili, Denis; Romeo, Andrea; Cavallini, Massimiliano; Scolaro, Luigi Monsù

    2017-01-01

    Chirality is one of the most intriguing properties of matter related to a molecule’s lack of mirror symmetry. The transmission of chirality from the molecular level up to the macroscopic scale has major implications in life sciences but it is also relevant for many chemical applications ranging from catalysis to spintronic. These technological applications require an accurate control of morphology, homogeneity and chiral handedness of thin films and nanostructures. We demonstrate a simple approach to specifically transfer chirality to the model supramolecular system of J aggregates of the protonated form of tetrakis(4-sulfonatophenyl)-porphyrin by utilizing a soft lithography technique. This approach successfully allows the fabrication of an ordered distribution of sub-micrometric structures in precise and controllable positions with programmed chirality, providing a fundamental breakthrough toward the exploitation of chiral supramolecular aggregates in technological applications, such as sensors, non-linear optics and spintronic. PMID:28275239

  20. Molecular chirality: language, history, and significance.

    Science.gov (United States)

    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.

  1. Symmetries of Ginsparg-Wilson Chiral Fermions

    CERN Document Server

    Mandula, Jeffrey E

    2009-01-01

    The group structure of the variant chiral symmetry discovered by Luscher in the Ginsparg-Wilson description of lattice chiral fermions is analyzed. It is shown that the group contains an infinite number of linearly independent symmetry generators, and the Lie algebra is given explicitly. CP is an automorphism of this extended chiral group, and the CP transformation properties of the symmetry generators are found. The group has an infinite-parameter subgroup, and the factor group whose elements are its cosets is isomorphic to the continuum chiral symmetry group. Features of the currents associated with these symmetries are discussed, including the fact that some different, non-commuting symmetry generators lead to the same Noether current. These are universal features of lattice chiral fermions based on the Ginsparg-Wilson relation; they occur in the overlap, domain-wall, and perfect-action formulations. In a solvable example - free overlap fermions - these non-canonical elements of lattice chiral symmetry are...

  2. Radioracemization and radiation-induced chiral amplification of chiral terpenes measured by optical rotatory dispersion (ORD) spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Cataldo, Franco [Lupi Chemical Research Institute, Via Casilina 1626/A, 00133 Rome (Italy); INAF-Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania (Italy)], E-mail: franco.cataldo@fastwebnet.it; Ursini, Ornella; Angelini, Giancarlo [Institute of Chemical Methodologies, CNR Via Salaria Km. 29300 00016 Monterotondo Stazione, Rome (Italy)

    2008-08-15

    For the first time the radioracemization of {alpha}(+)pinene and {alpha}(-)pinene, of turpentine and of R(-)-{alpha}-phellandrene has been studied by optical rotatory dispersion (ORD) spectroscopy. For all these compounds, the radioracemization implies a shift of the ORD curves toward lower levels of specific optical rotation. The radioracemization degree (R{sub R}) has been defined and calculated for all the compounds studied. It has been found that for radiation dose of 1 MGy the radioracemization degree is about 4.5% for the compound with the highest optical purity and reaches 7-8% for the less optically pure compounds, demonstrating that impurities can affect greatly the radioracemization. In contrast with the general radioracemization effect exerted by high-energy radiation on chiral molecules, {beta}(-)pinene, {beta}(+)pinene when irradiated show an increment of their specific optical rotation. This fact has been measured for the first time by ORD spectroscopy and the amplification degree of chirality can reach 1000% in the near UV. This phenomenon is due to the formation of a chiral polymer, poly-{beta}-pinene, which forms a solution with the monomer enhancing its optical activity. The implications for the theories of the origin of life of such unexpected phenomenon are discussed briefly.

  3. Negative refractive index in chiral metamaterials.

    Science.gov (United States)

    Zhang, Shuang; Park, Yong-Shik; Li, Jensen; Lu, Xinchao; Zhang, Weili; Zhang, Xiang

    2009-01-16

    We experimentally demonstrate a chiral metamaterial exhibiting negative refractive index at terahertz frequencies. The presence of strong chirality in the terahertz metamaterial lifts the degeneracy for the two circularly polarized waves and allows for the achievement of negative refractive index without requiring simultaneously negative permittivity and negative permeability. The realization of terahertz chiral negative index metamaterials offers opportunities for investigation of their novel electromagnetic properties, such as negative refraction and negative reflection, as well as important terahertz device applications.

  4. Chiral Plasmonic Nanostructures on Achiral Nanopillars

    Science.gov (United States)

    2013-10-10

    0704-0188 3. DATES COVERED (From - To) - UU UU UU UU Approved for public release; distribution is unlimited. Chiral Plasmonic Nanostructures on Achiral...Nanopillars Chirality of plasmonic films can be strongly enhanced by threedimensional (3D) out-of-plane geometries. The complexity of lithographic...methods currently used to produce such structures and other methods utilizing chiral templates impose limitations on spectral windows of chiroptical

  5. Chirality and the angular momentum of light

    Science.gov (United States)

    Cameron, Robert P.; Götte, Jörg B.; Barnett, Stephen M.; Yao, Alison M.

    2017-02-01

    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'.

  6. Chiral phases of fundamental and adjoint quarks

    Energy Technology Data Exchange (ETDEWEB)

    Natale, A. A. [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC 09210-170, Santo André, SP (Brazil); Instituto de Física Teórica - UNESP Rua Dr. Bento T. Ferraz, 271, Bl.II - 01140-070, São Paulo, SP (Brazil)

    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.

  7. Infinite Chiral Symmetry in Four Dimensions

    CERN Document Server

    Beem, Christopher; Liendo, Pedro; Peelaers, Wolfger; Rastelli, Leonardo; van Rees, Balt C

    2015-01-01

    We describe a new correspondence between four-dimensional conformal field theories with extended supersymmetry and two-dimensional chiral algebras. The meromorphic correlators of the chiral algebra compute correlators in a protected sector of the four-dimensional theory. Infinite chiral symmetry has far-reaching consequences for the spectral data, correlation functions, and central charges of any four-dimensional theory with ${\\mathcal N}=2$ superconformal symmetry.

  8. A spectral route to determining chirality

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Mortensen, Asger

    2009-01-01

    We show how one-dimensional structured media can be used to measure chirality, via the spectral shift of the photonic band gap edges. Analytically, we show that a chiral contrast can, in some cases, be mapped unto an index contrast, thereby greatly simplifying the analysis of such structures. Using...... this mapping, we derive a first-order shift of the band gap edges with chirality. Potentially, this effect could be used for measuring enantiomeric excess....

  9. Louis Pasteur, language, and molecular chirality. I. Background and dissymmetry.

    Science.gov (United States)

    Gal, Joseph

    2011-01-01

    Louis Pasteur resolved sodium ammonium (±)-tartrate in 1848, thereby discovering molecular chirality. Although hindered by the primitive state of organic chemistry, he introduced new terminology and nomenclature for his new science of molecular and crystal chirality. He was well prepared for this task by his rigorous education and innate abilities, and his linguistic achievements eventually earned him membership in the supreme institution for the French language, the Académie française. Dissymmetry had been in use in French from the early 1820s for disruption or absence of symmetry or for dissimilarity or difference in appearance between two objects, and Pasteur initially used it in the latter connotation, without any reference to handedness or enantiomorphism. Soon, however, he adopted it in the meaning of chirality. Asymmetry had been in use in French since 1691 but Pasteur ignored it in favor of dissymmetry. The two terms are not synonymous but it is not clear whether Pasteur recognized this difference in choosing the former over the latter. However, much of the literature mistranslates his dissymmetry as asymmetry. Twenty years before Pasteur the British polymath John Herschel proposed that optical rotation in the noncrystalline state is due to the "unsymmetrical" [his term] nature of the molecules and later used dissymmetrical for handed. Chirality, coined by Lord Kelvin in 1894 and introduced into chemistry by Mislow in 1962, has nearly completely replaced dissymmetry in the meaning of handedness, but the use of dissymmetry continues today in other contexts for lack of symmetry, reduction of symmetry, or dissimilarity.

  10. Chiral Separation of Erythromycin as a New Chiral Selector on CE

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Erythromycin as a new chiral selector was first used for chrial separation of four derivatives of biphenyldimethylester enantiomers on CE. The influence of pH, the chiral selector concentration and organic modifiers were preliminarily studied. Experiments show that the erythromycin as chiral selector is useful to CE.

  11. Chiral Induction with Chiral Conformational Switches in the Limit of Low "Sergeants to Soldiers" Ratio

    DEFF Research Database (Denmark)

    Nuermaimaiti, Ajiguli; Bombis, Christian; Knudsen, Martin Markvard

    2014-01-01

    " mechanism for an oligo(phenylene ethynylene) based chiral conformational switch by coadsorbing it with an intrinsically chiral seed on Au(111). Through statistical analysis of scanning tunneling microscopy (STM) data we demonstrate successful chiral induction with a very low concentration of seeding...

  12. Staggered chiral random matrix theory

    CERN Document Server

    Osborn, James C

    2010-01-01

    We present a random matrix theory (RMT) for the staggered lattice QCD Dirac operator. The staggered RMT is equivalent to the zero-momentum limit of the staggered chiral Lagrangian and includes all taste breaking terms at their leading order. This is an extension of previous work which only included some of the taste breaking terms. We will also present some results for the taste breaking contributions to the partition function and the Dirac eigenvalues.

  13. Molecule-based magnets

    Indian Academy of Sciences (India)

    J V Yakhmi

    2009-06-01

    The conventional magnetic materials used in current technology, such as, Fe, Fe2O3, Cr2O3, SmCo5, Nd2Fe14B etc are all atom-based, and their preparation/processing require high temperature routes. Employing self-assembly methods, it is possible to engineer a bulk molecular material with long-range magnetic order, mainly because one can play with the weak intermolecular interactions. Since the first successful synthesis of molecular magnets in 1986, a large variety of them have been synthesized, which can be categorized on the basis of the chemical nature of the magnetic units involved: organic-, metal-based systems, heterobimetallic assemblies, or mixed organic–inorganic systems. The design of molecule-based magnets has also been extended to the design of poly-functional molecular magnets, such as those exhibiting second-order optical nonlinearity, liquid crystallinity, or chirality simultaneously with long-range magnetic order. Solubility, low density and biocompatibility are attractive features of molecular magnets. Being weakly coloured, unlike their opaque classical magnet ‘cousins’ listed above, possibilities of photomagnetic switching exist. Persistent efforts also continue to design the ever-elusive polymer magnets towards applications in industry. While providing a brief overview of the field of molecular magnetism, this article highlights some recent developments in it, with emphasis on a few studies from the author’s own lab.

  14. On the gauging of chiral bosons

    CERN Document Server

    Wotzasek, C

    1995-01-01

    We study the coupling of chiral bosons to external electromagnetic fields. It is observed that a naive gauging procedure leaves the gauge invariant chirality condition incompatible with the field equations. We propose the use of this feature as a consistency test to select the appropriate way to perform the gauge coupling. We verify that among all the possible gauging schemes, only the coupling of gauge fields with chiral currents passes the consistency test. As an application, we use this gauging scheme to show how the introduction of a gauge field becomes necessary in order to sold together a right and a left chiral boson.

  15. Effects from inhomogeneities in the chiral transition

    CERN Document Server

    Taketani, B G; Taketani, Bruno G.; Fraga, Eduardo S.

    2006-01-01

    We consider an approximation procedure to evaluate the finite-temperature one-loop fermionic density in the presence of a chiral background field which systematically incorporates effects from inhomogeneities in the chiral field through a derivative expansion. We apply the method to the case of a simple low-energy effective chiral model which is commonly used in the study of the chiral phase transition, the linear sigma-model coupled to quarks. The modifications in the effective potential and their consequences for the bubble nucleation process are discussed.

  16. Laser Writing of Multiscale Chiral Polymer Metamaterials

    Directory of Open Access Journals (Sweden)

    E. P. Furlani

    2012-01-01

    Full Text Available A new approach to metamaterials is presented that involves laser-based patterning of novel chiral polymer media, wherein chirality is realized at two distinct length scales, intrinsically at the molecular level and geometrically at a length scale on the order of the wavelength of the incident field. In this approach, femtosecond-pulsed laser-induced two-photon lithography (TPL is used to pattern a photoresist-chiral polymer mixture into planar chiral shapes. Enhanced bulk chirality can be realized by tuning the wavelength-dependent chiral response at both the molecular and geometric level to ensure an overlap of their respective spectra. The approach is demonstrated via the fabrication of a metamaterial consisting of a two-dimensional array of chiral polymer-based L-structures. The fabrication process is described and modeling is performed to demonstrate the distinction between molecular and planar geometric-based chirality and the effects of the enhanced multiscale chirality on the optical response of such media. This new approach to metamaterials holds promise for the development of tunable, polymer-based optical metamaterials with low loss.

  17. Supramolecular Chirality in Dynamic Coordination Chemistry

    Directory of Open Access Journals (Sweden)

    Hiroyuki Miyake

    2014-10-01

    Full Text Available Labile metal complexes have a useful coordination bond; which is weaker than a covalent C–C bond and is reversibly and dynamically formed and dissociated. Such labile metal complexes also can be used to construct chiral shapes and offer dynamic conversion of chiral molecular shapes in response to external stimuli. This review provides recent examples of chirality induction and describes the dynamic conversion systems produced by chiral metal complexes including labile metal centers, most of which respond to external stimuli by exhibiting sophisticated conversion phenomena.

  18. Chiral methyl-branched pheromones.

    Science.gov (United States)

    Ando, Tetsu; Yamakawa, Rei

    2015-07-01

    Insect pheromones are some of the most interesting natural products because they are utilized for interspecific communication between various insects, such as beetles, moths, ants, and cockroaches. A large number of compounds of many kinds have been identified as pheromone components, reflecting the diversity of insect species. While this review deals only with chiral methyl-branched pheromones, the chemical structures of more than one hundred non-terpene compounds have been determined by applying excellent analytical techniques. Furthermore, their stereoselective syntheses have been achieved by employing trustworthy chiral sources and ingenious enantioselective reactions. The information has been reviewed here not only to make them available for new research but also to understand the characteristic chemical structures of the chiral pheromones. Since biosynthetic studies are still limited, it might be meaningful to examine whether the structures, particularly the positions and configurations of the branched methyl groups, are correlated with the taxonomy of the pheromone producers and also with the function of the pheromones in communication systems.

  19. Chiral symmetry breaking and monopoles

    CERN Document Server

    Di Giacomo, Adriano; Pucci, Fabrizio

    2015-01-01

    To understand the relation between the chiral symmetry breaking and monopoles, the chiral condensate which is the order parameter of the chiral symmetry breaking is calculated in the $\\overline{\\mbox{MS}}$ scheme at 2 [GeV]. First, we add one pair of monopoles, varying the monopole charges $m_{c}$ from zero to four, to SU(3) quenched configurations by a monopole creation operator. The low-lying eigenvalues of the Overlap Dirac operator are computed from the gauge links of the normal configurations and the configurations with additional monopoles. Next, we compare the distributions of the nearest-neighbor spacing of the low-lying eigenvalues with the prediction of the random matrix theory. The low-lying eigenvalues not depending on the scale parameter $\\Sigma$ are compared to the prediction of the random matrix theory. The results show the consistency with the random matrix theory. Thus, the additional monopoles do not affect the low-lying eigenvalues. Moreover, we discover that the additional monopoles increa...

  20. Chiral Asymmetric Structures in Aspartic Acid and Valine Crystals Assessed by Atomic Force Microscopy.

    Science.gov (United States)

    Teschke, Omar; Soares, David Mendez

    2016-03-29

    Structures of crystallized deposits formed by the molecular self-assembly of aspartic acid and valine on silicon substrates were imaged by atomic force microscopy. Images of d- and l-aspartic acid crystal surfaces showing extended molecularly flat sheets or regions separated by single molecule thick steps are presented. Distinct orientation surfaces were imaged, which, combined with the single molecule step size, defines the geometry of the crystal. However, single molecule step growth also reveals the crystal chirality, i.e., growth orientations. The imaged ordered lattice of aspartic acid (asp) and valine (val) mostly revealed periodicities corresponding to bulk terminations, but a previously unreported molecular hexagonal lattice configuration was observed for both l-asp and l-val but not for d-asp or d-val. Atomic force microscopy can then be used to identify the different chiral forms of aspartic acid and valine crystals.

  1. PHOTOINDUCED HOLOGRAPHIC PHASE GRATINGS BURIED IN AZOBENZENE SIDE-CHAIN POLYMER FILMS WITH A CHIRAL GROUP

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    An optically active polymer (PM1) containing azobenzene moieties with a chiral group (s-2-methyl-butyl) was synthesized by homopolymerization of monomer, 4-[2-(methacryloyloxy)ethyloxy]-4'-(s-2-methyl-1-butyloxycarbonyl)azobenzene, using the free radical polymerization method. The polymer dissolved in tetrahydrofuran (THF) could be easily processed into high optical quality films. The optical anisotropy of the polymer films was investigated by polarizing optical microscopy (POM). The experimental results showed that irradiation with a circularly polarized beam could align the orientation of the molecules in the polymer films. Moreover, the holographic phase gratings of photo-induced polymer films were detected by atomic force microscopy (AFM) and POM. In comparison with polymer containing no chiral group, it was found from the preliminary measurement of the photo-induced holographic phase gratings that PM1 containing a chiral group could form holographic phase gratings buried in the films.

  2. The chiral phase transition in a random matrix model with molecular correlations

    CERN Document Server

    Wettig, T; Weidenmüller, H A; Wettig, Tilo

    1995-01-01

    The chiral phase transition of QCD is analyzed in a model combining random matrix elements of the Dirac operator with specially chosen non-random ones. The special form of the latter is motivated by the assumption that the fermionic quasi-zero modes associated with instanton and anti-instanton configurations determine the chiral properties of QCD. Our results show that the degree of correlation between these modes plays the decisive role. To reduce the value of the chiral condensate by more than a factor of 2 about 95 percent of the instantons and anti-instantons must form so-called molecules. This conclusion agrees with numerical results of the Stony Brook group.

  3. Recent Advances in the Application of Chiral Phosphine Ligands in Pd-Catalysed Asymmetric Allylic Alkylation

    Directory of Open Access Journals (Sweden)

    Erika Martin

    2011-01-01

    Full Text Available One of the most powerful approaches for the formation of simple and complex chiral molecules is the metal-catalysed asymmetric allylic alkylation. This reaction has been broadly studied with a great variety of substrates and nucleophiles under different reaction conditions and it has promoted the synthesis of new chiral ligands to be evaluated as asymmetric inductors. Although the mechanism as well as the active species equilibria are known, the performance of the catalytic system depends on the fine tuning of factors such as type of substrate, nucleophile nature, reaction medium, catalytic precursor and type of ligand used. Particularly interesting are chiral phosphines which have proved to be effective asymmetric inductors in several such reactions. The present review covers the application of phosphine-donor ligands in Pd-catalysed asymmetric allylic alkylation in the last decade.

  4. Dimers of cyclic carbonates: chirality recognition in battery solvents and energy storage.

    Science.gov (United States)

    Kollipost, Franz; Hesse, Susanne; Lee, Juhyon J; Suhm, Martin A

    2011-08-21

    Dimers of ethylene carbonate and propylene carbonate are created in supersonic jet expansions and characterized by FTIR spectroscopy. Fermi resonances are switched on and off by dimerization. There is a unique centrosymmetric dimer of ethylene carbonate in a pronounced case of complementary chirality synchronization, contributing to its energy storage capacity at melting. Two chiral propylene carbonate molecules combine in more intricate ways. If they have the same handedness, one of them is forced into an axial conformation and the binding partner stays in the more stable equatorial structure. If they have opposite handedness, centrosymmetric dimers of either axial or equatorial conformations are formed. This suggests the usefulness of chirality control in elucidating ionic transport mechanisms in battery solvents and asymmetric catalysis in such solvents.

  5. Synthesis and Chiral Recognition of a New Type of Chiral Calix[4]arene Derivatives

    Institute of Scientific and Technical Information of China (English)

    HE,Yong-Bing; LI,Jian-Feng; XIAO,Yuan-Jing; WEI,Lan-Hua; WU,Xiao-Jun; MENG,Ling-Zhi

    2003-01-01

    Two new chiral calix[4] arenes bearing chiral pendants, which were from by-product of the antibiotic industry, were synthesized and characterized by 1H NMR, MS-FAB and elemental analysis. Studies of 1H NMR of the two calix [4] arene derivatives indicate that they exist in cone conformation in solution. Results of chiral recognition of the two chiral ligands 2a and 2b towards the tartaric acid derivative 3 show that ligand 2a exhibited good chiral recognition abilities compared to ligand 2b.

  6. Chiral memory via chiral amplification and selective depolymerization of porphyrin aggregates.

    Science.gov (United States)

    Helmich, Floris; Lee, Cameron C; Schenning, Albertus P H J; Meijer, E W

    2010-12-01

    Chiral memory at the supramolecular level is obtained via a new approach using chiral Zn porphrins and achiral Cu porphyrins. In a "sergeant-and-soldiers" experiment, the Zn "sergeant" transfers its own chirality to Cu "soldiers" and, after chiral amplification, the "sergeant" is removed from the coaggregates by axial ligation with a Lewis base. After this extraction, the preferred helicity observed for the aggregates containing achiral Cu porphyrins reveals a chiral memory effect that is stable and can be erased and partially restored upon subsequent heating and cooling.

  7. Twisting Fluorescence through Extrinsic Chiral Antennas.

    Science.gov (United States)

    Yan, Chen; Wang, Xiaolong; Raziman, T V; Martin, Olivier J F

    2017-03-22

    Plasmonic antennas and planar structures have been undergoing intensive developments in order to control the scattering and absorption of light. One specific class, extrinsic chiral surfaces, that does not possess 2-fold rotational symmetry exhibits strong asymmetric transmission for different circular polarizations under obliquely incident illumination. In this work, we show that the design of those surfaces can be optimized with complex multipolar resonances in order to twist the fluorescence emission from nearby molecules. While this emission is usually dipolar and linearly polarized, the interaction with these resonances twists it into a multipolar radiation pattern with opposite helicity in different directions. The proposed structure maximizes this effect and provides control over the polarization of light. Splitting of left- and right-handed circularly polarized light is experimentally obtained in the backward direction. These results highlight the intricate interplay between the near-field absorption and the far-field scattering of a plasmonic nanostructure and are further used for modifying the emission of incoherent quantum sources. Our finding can potentially lead to the development of polarization- and angle-resolved ultracompact optical devices.

  8. Preface to the Surface Science Topical Issue on Chirality at Surfaces

    Science.gov (United States)

    2014-11-01

    This Topical Issue of Surface Science focuses on the rapidly growing interest in the structure and enantioselective properties of chiral surfaces and chiral organic layers on surfaces. Chirality has intrigued scientists since the time of Pasteur and his 1848 [1] demonstration of the relationship between the optical rotation of light and the atomic structure of the compounds through which it propagates. The origin of optical rotation in the structure of organic molecules and the tetrahedral nature of the carbon atom was first appreciated and articulated by van't Hoff in 1874 [2]. In biochemistry, the importance of molecular chirality arises from the fact that most naturally occurring chiral biomolecules exist in homochiral form. For example, the fundamental building blocks of proteins are the amino acids which all appear in the L-enantiomeric form in nature. The implications of biomolecular homochirality were not truly appreciated until the late 1950s [3] when the stereochemistry of the artificially produced drug thalidomide was implicated in the physical defects observed in thousands of children born to mothers who had used the drug during pregnancy. This then sparked an explosion in asymmetric synthesis and enantioselective chemical processing in general, as regulations required that chiral pharmaceuticals be manufactured in enantiomerically pure form. The development of heterogenous catalysts for industrial-scale production of enantiomerically pure molecules is still a huge challenge. Many of the studies in this Topical Issue are aimed at developing a molecular level understanding of the surface processes which direct enantioselective reactions at gas-solid and liquid-solid interfaces.

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

    Science.gov (United States)

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

    2016-09-21

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

  10. Stardust and the Molecules of Life (Why are the Amino Acids Left-Handed?)

    Energy Technology Data Exchange (ETDEWEB)

    Boyd, R N; Kajino, T; Onaka, T

    2010-04-02

    A mechanism for creating and selecting amino acid chirality is identified, and subsequent chemical replication and galactic mixing that would populate the galaxy with the predominant species will be described. This involves: (1) the spin of the {sup 14}N in the amino acids, or in precursor molecules from which amino acids might be formed, coupling to the chirality of the molecules; (2) the neutrinos emitted from the supernova, together with magnetic field from the nascent neutron star or black hole from the supernova selectively destroying one orientation of the {sup 14}N, thereby selecting the chirality associated with the other {sup 14}N orientation; (3) amplification by chemical evolution, by which the molecules replicate on a relatively short timescale; and (4) galactic mixing on a longer timescale mixing the selected molecules throughout the galaxy.

  11. [Characterization of drug, narcotic and psychotropic drug chirality by statistical methods].

    Science.gov (United States)

    Noszál, B; Schiller, Z

    1999-04-01

    The percentage of chiral entities among drug, narcotic drug and psychotropic compounds is steadily increasing. Receptors of the human body recognize the enantiomeric forms of constitutionally identical compounds as entirely different chemical agents. Based upon these facts, this paper reports the percentage of chiral compounds in the various pharmacological classes, and related data. Pertinent terms, such as eutomer, distomer, eudismic index, eudismic affinity quotient are defined. Differences in biological activity between eutomers and distomers are exemplified. The pharmacological classes and subclasses of highest chirality, and the "most chiral" active principles are shown. Some puzzling observations on pharmacological behaviour of stereoisomers are highlighted. The necessity of "racemate switch" in the pharmaceutical industry, and the significance of stereo-specific interactions between the drug, narcotic drug and psychotropic ligands, and complementary, "pocket" moieties of the human body are emphasized. Some features of enantiopharmacology, a fledgling science in the interface of stereochemistry and traditional pharmacology are introduced. The statistical treatment of asymmetric compounds in pharmacological classes and subclasses shows that presently, the percentage of chirality in drug categories is more characteristic of the origin of the compound than its target molecule.

  12. A computational investigation of attrition-enhanced chiral symmetry breaking in conglomerate crystals

    Science.gov (United States)

    Ricci, Francesco; Stillinger, Frank H.; Debenedetti, Pablo G.

    2013-11-01

    Attrition-enhanced chiral symmetry breaking in crystals, also known as Viedma ripening, is a remarkable phenomenon from a variety of perspectives. By providing a direct route to solid-phase homochirality in a controllable manner, it is of inherent interest to those who study chiral symmetry-breaking/amplification mechanisms. When applied to intrinsically chiral molecules, Viedma ripening may have implications for the origin of biological homochirality, as well as applications in chiral drug resolution. Despite an abundance of research, the mechanistic details underlying this phenomenon have not been unambiguously elucidated. We employ a Monte Carlo algorithm to study this driven system, in order to gain further insights into the mechanisms capable of reproducing key experimental signatures. We provide a comprehensive numerical investigation of how the model parameters (attrition rate, liquid-phase racemization kinetics, and the relative rates of growth and dissolution kinetics) impact the system's overall behavior. It is shown that size-dependent crystal solubility alone is insufficient to reproduce most of the experimental signatures of Viedma ripening, and that some form of a solid-phase chiral feedback mechanism must be invoked in order to reproduce experimentally observed behavior. In this work, such feedback mechanisms can take the form of agglomeration, or of artificial modification of the size dependent growth kinetics.

  13. A strategy for tuning achiral main-chain polymers into helical assemblies and chiral memory systems.

    Science.gov (United States)

    Yang, Dong; Zhao, Yin; Lv, Kai; Wang, Xiufeng; Zhang, Wei; Zhang, Li; Liu, Minghua

    2016-01-28

    A general strategy to tune the achiral main chain polymers into helical nanoassemblies was proposed based on the co-gelation approach. As an example, two achiral main chain polymers, PCz8 and PSi8, were selected, and their co-assembly with an amphiphilic l- or d-glutamide gelator was investigated. Although the polymers could not form gels individually, they could form co-gels with the gelator and the resultant gels exhibited macroscopic supramolecular chirality, which could be confirmed by CD spectra and SEM observations. Moreover, the supramolecular chirality can be memorized even after the gelator molecules were removed. Remarkably, either the gelator-containing or gelator-free chiral polymer assemblies showed circularly polarized luminescence (CPL), which is usually inherent to intrinsic chiral polymers. It was suggested that during the co-gelation, the chirality of the gelator was transferred to and memorized by the achiral polymers. The approach seems to be general and we provided the first example to tune the achiral polymers into helical assemblies through the co-gelation.

  14. Enantiomeric excesses of chiral amines in ammonia-rich carbonaceous meteorites

    Science.gov (United States)

    Pizzarello, Sandra; Yarnes, Christopher T.

    2016-06-01

    Chiral homogeneity is essential to the structure and function of terrestrial biopolymers but the origin of this "homochirality" is poorly understood and remains one of the many unknowns surrounding the origins of life. Several amino acids extracted from Carbonaceous Chondrite meteorites display L-enantiomeric excesses (ee) and their findings have encouraged suggestions that an input of non-racemic meteoritic compounds to early Earth might have led to terrestrial homochirality. Motivated by occasional indications of possible ee in other classes of soluble meteoritic compounds, we have undertaken a systematic study of the chiral distribution of amines in Renazzo-type (CR) meteorites, where they are the second most abundant organic molecular species and ammonia is by far the most abundant single molecule. We report here the first time finding of L-ee for two chiral amines in several pristine CR meteorites from Antarctica and outline a proposal by which the compounds possibly formed from the same ketone precursors as some of the chiral amino acids. This would occur during a warm hydrous stage of the asteroidal parent body, via a reductive amination process in the presence of a large abundance of ammonia, where the precursors' adsorption upon mineral phases possessing asymmetry offered the opportunity for chiral induction. Because the precursor ketones are achiral, the proposal underscores the likelihood of diverse asymmetric influences and processes in cosmochemistry.

  15. Chiral metamaterials reduce the attractive Casimir force

    Science.gov (United States)

    Zhao, R.; Koschny, Th.; Economou, E. N.; Soukoulis, C. M.

    2010-08-01

    In our previous work [R. Zhao, J. Zhou, Th. Koschny, E. N. Economou, and C. M. Soukoulis, Phys. Rev. Lett. 103, 103602 (2009)], we demonstrated theoretically that one can obtain repulsive Casimir forces and stable nanolevitations by using chiral metamaterials if the chirality is strong enough. In our recent work [R. Zhao, Th. Koschny, E.N. Economou, and C.M. Soukoulis, Phys. Rev. B 81, 235126 (2010)], we checked some chiral metamaterial designs and found that the artificial chiral metamaterials constructed by passive materials is very difficult to reach the critical chirality to realize repulsive Casimir force. Therefore, in this paper, we give a four-folded rotated Ω-particle chiral metamaterial as an example, use the effective medium approximation to retrieval the constitutive parameters, and take the same procedure as we did before to see how much the chiral metamaterial can reduce the attractive force. It shows that this un-optimized chiral metamaterial can reduce the Casimir attraction by 70%.

  16. LINEARLY POLARIZED PROBES OF SURFACE CHIRALITY

    NARCIS (Netherlands)

    VERBIEST, T; KAURANEN, M; MAKI, JJ; TEERENSTRA, MN; SCHOUTEN, AJ; NOLTE, RJM; PERSOONS, A

    1995-01-01

    We present a new nonlinear optical technique to study surface chirality. We demonstrate experimentally that the efficiency of second-harmonic generation from isotropic chiral surfaces is different for excitation with fundamental light that is +45 degrees and -45 degrees linearly polarized with respe

  17. An Extended Chiral SU(3) Quark Model

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zong-Ye; YU You-Wen; WANG Ping; DAI Lian-Rong

    2003-01-01

    The chiral SU(3) quark model is extended by including the vector meson exchanges to describe the short range interactions. The phase shifts of NN scattering are studied in this model. Compared with the results of the chiral SU(3) quark model in which only the pseudo-scalar and scalar chiralfields are considered, the phase shifts of 1 So wave are obviously improved.

  18. A NEW CHIRAL ALLOTROPE C80

    Institute of Scientific and Technical Information of China (English)

    詹克明

    1994-01-01

    The theoretical prophecy is given on a new chiral allotrope of Fullerene-C80.C80 molecuule should have 3C2 symmetric axes,which should be vertical each othyer.C80 should have two chiral allotropes,13C-NMR spectra of C80 should consist of 20 lines of equal intensity.

  19. Chiral magnetic effect in condensed matter systems

    Science.gov (United States)

    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].

  20. DEVELOPMENT AND REGISTRATION OF CHIRAL DRUGS

    NARCIS (Netherlands)

    WITTE, DT; ENSING, K; FRANKE, JP; DEZEEUW, RA

    1993-01-01

    In this review we describe the impact of chirality on drug development and registration in the United States, Japan and the European Community. Enantiomers may have differences in their pharmacological profiles, and, therefore, chiral drugs ask for special analytical and pharmacological attention du

  1. Quenched chiral perturbation theory to one loop

    NARCIS (Netherlands)

    Colangelo, Gilberto; Pallante, Elisabetta

    1998-01-01

    We calculate the divergences of the generating functional of quenched chiral perturbation theory at one loop, and renormalize the theory by an appropriate definition of the counterterms. We show that the quenched chiral logarithms can be accounted for by defining a renormalized B0 parameter which, a

  2. Lambda Hypernuclei in a Chiral Hadronic Model

    Institute of Scientific and Technical Information of China (English)

    LIANG Yin-Hua; GUO Hua

    2005-01-01

    @@ Nuclear matter calculations in a chiral hadronic model have been performed. It has been found that the scalar and the vector potentials and binding energies per nucleon in the chiral hadronic model are very close to those of the microscopic relativistic Brueckner-Hartree-Fock calculations. The good results for finite nuclei can be obtained in the mean field approximation only if scalar mass ms and coupling constant gs have been improved with the fixed values of cs2 ≡ g2s(M/ms)2 as those given by the original parameter sets of the chiral hadronic model. Then the chiral hadronic model is extended to lambda hypernuclei. Our results predicted by the chiral hadronic model are compared with those by the nonlinear Walecka model. It has been shown that the hadronic model can also be used to describe lambda hypernuclei successfully.

  3. Chiral Superfluidity for the Heavy Ion Collisions

    CERN Document Server

    Kalaydzhyan, T

    2013-01-01

    We argue that the strongly coupled quark-gluon plasma formed at LHC and RHIC can be considered as a chiral superfluid. The "normal" component of the fluid is the thermalized matter in common sense, while the "superfluid" part consists of long wavelength (chiral) fermionic states moving independently. We use the bosonization procedure with a finite cut-off and obtain a dynamical axion-like field out of the chiral fermionic modes. Then we use relativistic hydrodynamics for macroscopic description of the effective theory obtained after the bosonization. Finally, solving the hydrodynamic equations in gradient expansion, we find that in the presence of external electromagnetic fields the motion of the "superfluid" component gives rise to the chiral magnetic, chiral electric and dipole wave effects. Latter two effects are specific for a two-component fluid, which provides us with crucial experimental tests of the model. By considering probe quarks one can show that the fermionic spectrum at the intermediate tempera...

  4. New Chiral Bis-Dipolar 6,6'-Disubstituted-Binaphthol Derivatives for Second-Order Nonlinear Optics

    DEFF Research Database (Denmark)

    Deussen, Heinz-Josef; Boutton, Carlo; Thorup, Niels;

    1998-01-01

    (S)everal chiral molecules with C-2 symmetry derived from two geometries of the binaphthol (BN) system substituted with different accepters have been synthesized in order to study the possibility of producing noncentrosymmetric crystals formed from these chiral structures. All the molecules possess...... cancel out exactly despite the noncentrosymmetry. The crystal structure of racemic 9,14-dicyanodinaphtho[2,1-d:1',2'-f][1,3]-dioxepin (2b) was found to be centrosymmetric. The new compounds were investigated for second-harmonic generation (including BN derivatives reported earlier) by the Kurtz......-Perry powder test to evaluate the second-order nonlinear optical (NLO) properties of polycrystalline samples. Although chirality ensures noncentrosymmetric crystals, only modest (approximate to 2-methyl-4-nitroaniline) or no nonlinearities were observed in the powder test, For a representative selection...

  5. Principal chiral model on superspheres

    Energy Technology Data Exchange (ETDEWEB)

    Mitev, V.; Schomerus, V. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Quella, T. [Amsterdam Univ. (Netherlands). Inst. for Theoretical Physics

    2008-09-15

    We investigate the spectrum of the principal chiral model (PCM) on odd-dimensional superspheres as a function of the curvature radius R. For volume-filling branes on S{sup 3} {sup vertical} {sup stroke} {sup 2}, we compute the exact boundary spectrum as a function of R. The extension to higher dimensional superspheres is discussed, but not carried out in detail. Our results provide very convincing evidence in favor of the strong-weak coupling duality between supersphere PCMs and OSP(2S+2 vertical stroke 2S) Gross-Neveu models that was recently conjectured by Candu and Saleur. (orig.)

  6. Status of chiral meson physics

    Energy Technology Data Exchange (ETDEWEB)

    Bijnens, Johan [Department of Astronomy and Theoretical Physics, Lund University, Sölvegatan 14A, SE 22362 Lund (Sweden)

    2016-01-22

    This talk includes a short introduction to Chiral Perturbation Theory in the meson sector concentrating on a number of recent developments. I discuss the latest fit of the low-energy constants. Finite volume corrections are discussed for the case with twisted boundary conditions for form-factors and first results at two-loops for three flavours for masses. The last part discusses the extension to other symmetry breaking patterns relevant for technicolour and related theories as well as the calculation of leading logarithms to high loop orders.

  7. Chiral Anomaly in Contorted Spacetimes

    CERN Document Server

    Mielke, E W

    1999-01-01

    The Dirac equation in Riemann-Cartan spacetimes with torsion is reconsidered. As is well-known, only the axial covector torsion $A$, a one-form, couples to massive Dirac fields. Using diagrammatic techniques, we show that besides the familiar Riemannian term only the Pontrjagin type four-form $dA\\wedge dA$ does arise additionally in the chiral anomaly, but not the Nieh-Yan term $d ^* A$, as has been claimed recently. Implications for cosmic strings in Einstein-Cartan theory as well as for Ashtekar's canonical approach to quantum gravity are discussed.

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

    Science.gov (United States)

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

    2013-04-16

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

  9. New possibilities for the gauging of chiral bosons

    CERN Document Server

    Abreu, Everton M C; Wotzasek, C; Abreu, Everton M. C.; Dutra, Alvaro de Souza; Wotzasek, Clovis

    2003-01-01

    We study a new mechanism for the electromagnetic gauging of chiral bosons showing that new possibilities emerge for the interacting theory of chiral scalars. We introduce a chirally coupled gauge field necessary to mod out the degree of freedom that obstructs gauge invariance in a system of two opposite chiral bosons soldering them together.

  10. Synthesis and characterization of mixed ligand chiral nanoclusters

    KAUST Repository

    Guven, Zekiye P.

    2016-06-22

    Chiral mixed ligand silver nanoclusters were synthesized in the presence of a chiral and an achiral ligand. While the chiral ligand led mostly to the formation of nanoparticles, the presence of the achiral ligand drastically increased the yield of nanoclusters with enhanced chiral properties. © 2016 The Royal Society of Chemistry.

  11. Novel Applications of Buffer-gas Cooling to Cold Atoms, Diatomic Molecules, and Large Molecules

    Science.gov (United States)

    Drayna, Garrett Korda

    Cold gases of atoms and molecules provide a system for the exploration of a diverse set of physical phenomena. For example, cold gasses of magnetically and electrically polar atoms and molecules are ideal systems for quantum simulation and quantum computation experiments, and cold gasses of large polar molecules allow for novel spectroscopic techniques. Buffer-gas cooling is a robust and widely applicable method for cooling atoms and molecules to temperatures of approximately 1 Kelvin. In this thesis, I present novel applications of buffer-gas cooling to obtaining gases of trapped, ultracold atoms and diatomic molecules, as well as the study of the cooling of large organic molecules. In the first experiment of this thesis, a buffer-gas beam source of atoms is used to directly load a magneto-optical trap. Due to the versatility of the buffer-gas beam source, we obtain trapped, sub-milliKelvin gases of four different lanthanide species using the same experimental apparatus. In the second experiment of this thesis, a buffer-gas beam is used as the initial stage of an experiment to directly laser cool and magneto-optically trap the diatomic molecule CaF. In the third experiment of this thesis, buffer-gas cooling is used to study the cooling of the conformational state of large organic molecules. We directly observe conformational relaxation of gas-phase 1,2-propanediol due to cold collisions with helium gas. Lastly, I present preliminary results on a variety of novel applications of buffer-gas cooling, such as mixture analysis, separation of chiral mixtures, the measurement of parity-violation in chiral molecules, and the cooling and spectroscopy of highly unstable reaction intermediates.

  12. Chiral Ionic Liquids in Chromatographic Separation and Spectroscopic Discrimination

    Science.gov (United States)

    Li, Min; Bwambok, David K.; Fakayode, Sayo O.; Warner, Isiah M.

    Chiral ionic liquids (CILs) are a subclass of ionic liquids (ILs) in which the cation, anion, or both may be chiral. The chirality can be central, axial, or planar. CILs possess a number of unique advantageous properties which are inherited from ionic liquids including negligible vapor pressure, wide liquidus temperature range, high thermal stability, and high tunability. Due to their dual functionalities as chiral selectors and chiral solvents simultaneously, CILs recently have been widely used both in enantiomeric chromatographic separation and in chiral spectroscopic discrimination. In this chapter, the various applications of CILs in chiral chromatographic separations such as GC, HPLC, CE, and MEKC are reviewed. The applications of CILs in enantiomeric spectroscopic discrimination using techniques such as NMR, fluorescence, and NIR are described. In addition, chiral recognition and separation mechanism using the CILs as chiral selectors or chiral solvents is also discussed.

  13. Chiral transition with magnetic fields

    CERN Document Server

    Ayala, Alejandro; Mizher, Ana Julia; Rojas, Juan Cristobal; Villavicencio, Cristian

    2014-01-01

    We study the nature of the chiral transition for an effective theory with spontaneous breaking of symmetry, where charged bosons and fermions are subject to the effects of a constant external magnetic field. The problem is studied in terms of the relative intensity of the magnetic field with respect to the mass and the temperature. When the former is the smallest of the scales, we present a suitable method to obtain magnetic and thermal corrections up to ring order at high temperature. By these means, we solve the problem of the instability in the boson sector for these theories, where the squared masses, taken as functions of the order parameter, can vanish and even become negative. The solution is found by considering the screening properties of the plasma, encoded in the resummation of the ring diagrams at high temperature. We also study the case where the magnetic field is the intermediate of the three scales and explore the nature of the chiral transition as we vary the field strength, the coupling const...

  14. Nucleic acids, proteins, and chirality

    Science.gov (United States)

    Usher, D. A.; Profy, A. T.; Walstrum, S. A.; Needels, M. C.; Bulack, S. C.; Lo, K. M.

    1984-01-01

    The present investigation is concerned with experimental results related, in one case, to the chirality of nucleotides, and, in another case, to the possibility of a link between the chirality of nucleic acids, and that of peptides. It has been found that aminoacylation of the 'internal' hydroxyl group of a dinucleoside monophosphate can occur stereoselectively. However, this reaction has not yet been made a part of a working peptide synthesis scheme. The formation and cleavage of oligonucleotides is considered. In the event of the formation of a helical complex between the oligonucleotide and the polymer, 1-prime,5-prime-bonds in the oligomer are found to become more resistant towards cleavage. The conditions required for peptide bond formation are examined, taking into account the known structures of RNA and possible mechanisms for prebiotic peptide bond formation. The possibility is considered that the 2-prime,5-prime-internucleotide linkage could have played an important part in the early days of biological peptide synthesis.

  15. Chiral differential operators and topology

    CERN Document Server

    Cheung, Pokman

    2010-01-01

    The first part of this paper provides a new formulation of chiral differential operators (CDOs) in terms of global geometric quantities. The main result is a recipe to define essentially all sheaves of smooth CDOs on a cs-manifold; its ingredients consist of an affine connection and an even 3-form that trivializes the first Pontrjagin form. With the connection fixed, two suitable 3-forms define isomorphic sheaves of CDOs if and only if their difference is exact. Moreover, conformal structures are in one-to-one correspondence with even 1-forms that trivialize the first Chern form. The second part of this paper concerns the construction of what may be called "chiral Dolbeault complexes". The classical Dolbeault complex of a complex manifold M may be viewed as the functions on an associated cs-manifold with the action of an odd vector field Q that satisfies Q^2=0. Motivated by this, we study the condition under which a conformal sheaf of CDOs on that cs-manifold admits an odd derivation Q' that extends Q and sat...

  16. Nuclear chiral dynamics and thermodynamics

    CERN Document Server

    Holt, J W; Weise, W

    2013-01-01

    This presentation reviews an approach to nuclear many-body systems based on the spontaneously broken chiral symmetry of low-energy QCD. In the low-energy limit, for energies and momenta small compared to a characteristic symmetry breaking scale of order 1 GeV, QCD is realized as an effective field theory of Goldstone bosons (pions) coupled to heavy fermionic sources (nucleons). Nuclear forces at long and intermediate distance scales result from a systematic hierarchy of one- and two-pion exchange processes in combination with Pauli blocking effects in the nuclear medium. Short distance dynamics, not resolved at the wavelengths corresponding to typical nuclear Fermi momenta, are introduced as contact interactions between nucleons. Apart from a set of low-energy constants associated with these contact terms, the parameters of this theory are entirely determined by pion properties and low-energy pion-nucleon scattering observables. This framework (in-medium chiral perturbation theory) can provide a realistic des...

  17. On the possibility that supernovae influence homochiral organic molecule formation

    Energy Technology Data Exchange (ETDEWEB)

    Cline, D.B. [Univ. of California Los Angeles, Dept. of Physics and Astronomy 405 Hilgard Avenue, Los Angeles, California 90095-1547 (United States)

    1996-07-01

    The origin of the homochirality of the organic molecules in living material remains a mystery. We propose here that the supernova(s) that initiated the solar system also produced the mechanism for the chiral symmetry breaking in the organic material in the interstellar medium. The major process would involve either {bar {ital v}}{sub {ital e}} from a supernova explosion or the {ital Al}{sup 26} produced in the debris in conjunction with the weak neutral current process. Both give rise to chiral positrons and interactions with the organic material in the prebiotic medium. We describe some possible tests of this concept. We note that in this picture, all life forms in the Universe based on hydrocarbons should have the same chiral structure. {copyright} {ital 1996 American Institute of Physics.}

  18. Detection of zinc ions under aqueous conditions using chirality assisted solid-state fluorescence of a bipyridyl based fluorophore.

    Science.gov (United States)

    Sreejith, Sivaramapanicker; Divya, Kizhumuri P; Ajayaghosh, Ayyappanpillai

    2008-07-07

    A pyrrole end-capped bipyridyl ligand incorporating a chiral handle exhibited high solid-state emission when compared to the achiral analogue 1b and to the racemic molecule 1c which allowed the design of a reusable fluorescent probe for the selective detection of Zn2+ under aqueous conditions.

  19. Spontaneous Planar Chiral Symmetry Breaking in Cells

    Science.gov (United States)

    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.

  20. N-H stretching modes around 3300 wavenumber from peptide backbones observed by chiral sum frequency generation vibrational spectroscopy.

    Science.gov (United States)

    Fu, Li; Wang, Zhuguang; Yan, Elsa C Y

    2014-09-01

    We present a detailed analysis of the molecular origin of the chiral sum frequency generation (SFG) signals of proteins and peptides at interfaces in the N-H stretching vibrational region. The N-H stretching can be a probe for investigating structural and functional properties of proteins, but remains technically difficult to analyze due to the overlapping with the O-H stretching of water molecules. Chiral SFG spectroscopy offers unique tools to study the N-H stretching from proteins at interfaces without interference from the water background. However, the molecular origin of the N-H stretching signals of proteins is still unclear. This work provides a justification of the origin of chiral N-H signals by analyzing the vibrational frequencies, examining chiral SFG theory, studying proton (hydrogen/deuterium) exchange kinetics, and performing optical control experiments. The results demonstrate that the chiral N-H stretching signals at ~3300 cm(-1) originate from the amide group of the protein backbones. This chiral N-H stretching signal offers an in situ, real-time, and background-free probe for interrogating the protein structures and dynamics at interfaces at the molecular level.

  1. New Chiral Calixarene Derivatives: Syntheses and Their Chiral Recognition Toward Amino Acids by UV-Vis Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Three novel types of chiral calixarene derivatives 5, 8, and 10 were designed and synthesized by introducing chiral units to parent calixarenes. Their chiralities were confirmed by rotational analysis. Chiral recognition properties of these host compounds towards L- and D-threonine were studied by UV-Vis spectroscopy. The results indicated that calixarene derivatives 5 and 8 exhibited good chiral recognition capabilities toward L- or D-threonine. Although calixarene derivative 10 had no evident chiral recognition ability, the supramolecules of calixarene derivative 10 with L- or D-threonine showed a hypochromic effect or hyperchromic effect respectively. Therefore, calixarene derivative 10 might serve as a good chiral UV-indicator.

  2. The Life Story of Hydrogen Peroxide III: Chirality and Physical Effects at the Dawn of Life

    Science.gov (United States)

    Ball, Rowena; Brindley, John

    2016-03-01

    It is a remarkable observed fact that all life on Earth is homochiral, its biology using exclusively the D-enantiomer of ribose, the sugar moiety of the ribonucleic acids, and the L-enantiomers of the chiral amino acids. Motivated by concurrent work that elaborates further the role of hydrogen peroxide in providing an oscillatory drive for the RNA world (Ball & Brindley 2015a, J. R. Soc. Interface 12, 20150366, and Ball & Brindley 2015b, this journal, in press), we reappraise the structure and physical properties of this small molecule within this context. Hydrogen peroxide is the smallest, simplest molecule to exist as a pair of non-superimposable mirror images, or enantiomers, a fact which leads us to develop the hypothesis that its enantiospecific interactions with ribonucleic acids led to enantioselective outcomes. We propose a mechanism by which these chiral interactions may have led to amplification of D-ribonucleic acids and extinction of L-ribonucleic acids.

  3. New studies on molecular chirality in the gas phase: enantiomer differentiation and determination of enantiomeric excess.

    Science.gov (United States)

    Patterson, David; Schnell, Melanie

    2014-06-21

    Chirality plays a fundamental role in the activity of biological molecules and broad classes of chemical reactions. The chemistry of life is built almost exclusively on left-handed amino acids and right-handed sugars, a phenomenon known as "homochirality of life". Furthermore, most drugs developed in the last decade are of specified chirality. Thus, fast and reliable methods that can differentiate molecules of different handedness, determine the enantiomeric excess of even molecular mixtures, and allow for an unambiguous determination of molecular handedness are of great interest, in particular with respect to complex mixtures. In this perspective article, we discuss the recent developments, with an emphasis on modern spectroscopic methods using gas-phase samples, such as photoelectron circular dichroism, Coulomb explosion imaging, and microwave three-wave mixing.

  4. Low symmetry tetrahedral nematic liquid crystal phases: Ambidextrous chirality and ambidextrous helicity.

    Science.gov (United States)

    Pleiner, Harald; Brand, Helmut R

    2014-02-01

    We discuss the symmetry properties as well as the dynamic behavior of various non-polar nematic liquid crystal phases with tetrahedral order. We concentrate on systems that show biaxial nematic order coexisting with octupolar (tetrahedral) order. Non-polar examples are phases with D2 and S4 symmetries, which can be characterized as biaxial nematics lacking inversion symmetry. It is this combination that allows for new features in the statics and dynamics of these phases. The D2-symmetric phase is chiral, even for achiral molecules, and shows ambidextrous chirality in all three preferred directions. The achiral S4-symmetric phase allows for ambidextrous helicity, similar to the higher-symmetric D2d-symmetric phase. Such phases are candidates for nematic phases made from banana-shaped molecules.

  5. Biocatalysis: synthesis of chiral intermediates for drugs.

    Science.gov (United States)

    Patel, Ramesh N

    2006-11-01

    Chirality is a key factor in the safety and efficacy of many drug products and thus the production of single enantiomers of drug intermediates has become increasingly important in the pharmaceutical industry. Chiral intermediates and fine chemicals are in high demand for the bulk preparation of drug substances and agricultural products. There has been an increasing awareness of the enormous potential of the use of microorganisms and microorganism-derived enzymes for the transformation of synthetic chemicals with high chemo-, regio- and enantioselectivities. In this article, biocatalytic processes are described for the synthesis of chiral intermediates for drugs.

  6. Interplay between Deconfinement and Chiral Properties

    CERN Document Server

    Suganuma, Hideo; Redlich, Krzysztof; Sasaki, Chihiro

    2016-01-01

    We study interplay between confinement/deconfinement and chiral properties. We derive some analytical relations of the Dirac modes with the confinement quantities, such as the Polyakov loop, its susceptibility and the string tension. For the confinement quantities, the low-lying Dirac eigenmodes are found to give negligible contribution, while they are essential for chiral symmetry breaking. This indicates no direct, one-to-one correspondence between confinement/deconfinement and chiral properties in QCD. We also investigate the Polyakov loop in terms of the eigenmodes of the Wilson, the clover and the domain-wall fermion kernels, respectively.

  7. Enhanced Chiral Recognition by Cyclodextrin Dimers

    Directory of Open Access Journals (Sweden)

    Bart Jan Ravoo

    2011-07-01

    Full Text Available In this article we investigate the effect of multivalency in chiral recognition. To this end, we measured the host-guest interaction of a β-cyclodextrin dimer with divalent chiral guests. We report the synthesis of carbohydrate-based water soluble chiral guests functionalized with two borneol, menthol, or isopinocampheol units in either (+ or (– configuration. We determined the interaction of these divalent guests with a β-cyclodextrin dimer using isothermal titration calorimetry. It was found that—in spite of a highly unfavorable conformation—the cyclodextrin dimer binds to guest dimers with an increased enantioselectivity, which clearly reflects the effect of multivalency.

  8. Critical Temperature of Chiral Symmetry Restoration for Quark Matter with a Chiral Chemical Potential

    CERN Document Server

    Ruggieri, M

    2016-01-01

    In this article we study restoration of chiral symmetry at finite temperature for quark matter with a chiral chemical potential, $\\mu_5$, by means of a quark-meson model with vacuum fluctuations included. Vacuum fluctuations give a divergent contribution to the vacuum energy, so the latter has to be renormalized before computing physical quantities. The vacuum term is important for restoration of chiral symmetry at finite temperature and $\\mu_5\

  9. Hadron Molecules

    CERN Document Server

    Gutsche, Thomas; Faessler, Amand; Lee, Ian Woo; Lyubovitskij, Valery E

    2010-01-01

    We discuss a possible interpretation of the open charm mesons $D_{s0}^*(2317)$, $D_{s1}(2460)$ and the hidden charm mesons X(3872), Y(3940) and Y(4140) as hadron molecules. Using a phenomenological Lagrangian approach we review the strong and radiative decays of the $D_{s0}^* (2317)$ and $D_{s1}(2460)$ states. The X(3872) is assumed to consist dominantly of molecular hadronic components with an additional small admixture of a charmonium configuration. Determing the radiative ($\\gamma J/\\psi$ and $\\gamma \\psi(2s)$) and strong ($J/\\psi 2\\pi $ and $ J/\\psi 3\\pi$) decay modes we show that present experimental observation is consistent with the molecular structure assumption of the X(3872). Finally we give evidence for molecular interpretations of the Y(3940) and Y(4140) related to the observed strong decay modes $J/\\psi + \\omega$ or $J/\\psi + \\phi$, respectively.

  10. Proposal for Laser Cooling of Complex Polyatomic Molecules.

    Science.gov (United States)

    Kozyryev, Ivan; Baum, Louis; Matsuda, Kyle; Doyle, John M

    2016-11-18

    An experimentally feasible strategy for direct laser cooling of polyatomic molecules with six or more atoms is presented. Our approach relies on the attachment of a metal atom to a complex molecule, where it acts as an active photon cycling site. We describe a laser cooling scheme for alkaline earth monoalkoxide free radicals taking advantage of the phase space compression of a cryogenic buffer-gas beam. Possible applications are presented including laser cooling of chiral molecules and slowing of molecular beams using coherent photon processes.

  11. New Chiral Metal Cluster Systems for Catalytic Asymmetric Syntheses of Chiral Alcohols

    Institute of Scientific and Technical Information of China (English)

    LI Yan-yun; CHEN Jian-shan; YANG Chuan-bo; DONG Zhen-rong; LI Bao-zhu; ZHANG Hui; GAO Jing-xing; TAKAO Ikariya

    2004-01-01

    The efficient chiral Ru3(CO)12 systems were prepared in situ from Ru3(CO)12 and various chiral diiminoor diamino-diphosphine tetradentate ligands. The systems have been used for the asymmetric transfer hydrogenation of propiophenone in 2-propanol, leading to 1-phenyl-1-propanol in a 98% yield and 96% e.e. The IR study suggests that the carbonyl hydride anion [HRu3(CO)11]- most probably exists as a principal species under the reaction conditions. The high chiral efficiency may be due to the synergetic effect produced by the neighboring ruthenium atoms and a special chiral micro-environment involving the polydentate ligand and the Ru3 framework.

  12. Chirality affects aggregation kinetics of single-walled carbon nanotubes.

    Science.gov (United States)

    Khan, Iftheker A; Afrooz, A R M Nabiul; Flora, Joseph R V; Schierz, P Ariette; Ferguson, P Lee; Sabo-Attwood, Tara; Saleh, Navid B

    2013-02-19

    Aggregation kinetics of chiral-specific semiconducting single-walled carbon nanotubes (SWNTs) was systematically studied through time-resolved dynamic light scattering. Varied monovalent (NaCl) and divalent (CaCl(2)) electrolyte composition was used as background solution chemistry. Suwannee River humic acid (SRHA) was used to study the effects of natural organic matter on chirally separated SWNT aggregation. Increasing salt concentration and introduction of divalent cations caused aggregation of SWNT clusters by suppressing the electrostatic repulsive interaction from the oxidized surfaces. The (6,5) SWNTs, i.e., SG65, with relatively lower diameter tubes compared to (7,6), i.e., SG76, showed substantially higher stability (7- and 5-fold for NaCl and CaCl(2), respectively). The critical coagulation concentration (CCC) values were 96 and 13 mM NaCl in the case of NaCl and 2.8 and 0.6 mM CaCl(2) for SG65 and SG76, respectively. The increased tube diameter for (7,6) armchair SWNTs likely presented with higher van der Waals interaction and thus increased the aggregation propensity substantially. The presence of SRHA enhanced SWNT stability in divalent CaCl(2) environment through steric interaction from adsorbed humic molecules; however showed little or no effects for monovalent NaCl. The mechanism of aggregation-describing favorable interaction tendencies for (7,6) SWNTs-is probed through ab initio molecular modeling. The results suggest that SWNT stability can be chirality dependent in typical aquatic environment.

  13. Molecular Recognition of Biomolecules by Chiral CdSe Quantum Dots

    Science.gov (United States)

    Mukhina, Maria V.; Korsakov, Ivan V.; Maslov, Vladimir G.; Purcell-Milton, Finn; Govan, Joseph; Baranov, Alexander V.; Fedorov, Anatoly V.; Gun’Ko, Yurii K.

    2016-04-01

    Molecular recognition is one of the most important phenomena in Chemistry and Biology. Here we present a new way of enantiomeric molecular recognition using intrinsically chiral semiconductor nanocrystals as assays. Real-time confocal microscopy studies supported by circular dichroism spectroscopy data and theoretical modelling indicate an ability of left-handed molecules of cysteine and, to a smaller extent, histidine and arginine to discriminate between surfaces of left- and right-handed nanocrystals.

  14. The Synthesis of a New Type of Calix[4]arene with Chiral Pendant

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Two new chiral calixarenes were synthesized by condensing 1,3-bis-chlorocarbomethyl-calix[4]arehes with (1S, 2S)-2-amino-1-(4-nitrophenyl)-1, 3-propanediol, a by-product from antibiotic industry ,and were characterized by 1H-NMR , MS-FAB, and elemental analysis. The 1H-NMR spectra show that those molecules assume a cone conformation in solution.

  15. CD Spectroscopic Study on the Molecular Recognition of Chiral Salen-Metal Complexes

    Institute of Scientific and Technical Information of China (English)

    刘涛; 阮文娟; 南晶; 朱志昂

    2003-01-01

    The molecular recognition behavior of the chiral salen-metal complexes towards guest molecules, such as imidazole derivatives and amino-acid ester, was systematically investigated by means of circular dichroism (CD) spectra. The coordination numbers of the host-guest complexes as well as the recognition capability of the salen-metal complexes were explained by character and intensity analyses of the CD spectra.

  16. Thin film phase and local chirality of surface-bound MOP4 nanofibers

    DEFF Research Database (Denmark)

    Balzer, Frank; Röthel, Christian; Rubahn, Horst-Günter

    2016-01-01

    Vacuum deposition of the methoxy-functionalized p-quaterphenylene MOP4 on muscovite mica at elevated temperatures led to the formation of several ten micrometer long nanofibers. As shown by X-ray diffraction and polarized optical microscopy, the fibers are formed by lying molecules which grow epi...... by atomic force microscopy (AFM). The fibers represent chiral organization into single-handed aggregates of both handednesses, which is not affected by aging. On a global level, the sample remained achiral....

  17. Reconnaissance chirale dans des complexes moléculaires neutres et ioniques

    OpenAIRE

    Sen, Ananya

    2012-01-01

    The main objective of this thesis is a spectroscopic study of molecules or complexes bearing multiple chiral centres in the gas phase, to understand the effects of stereochemistry on their structural properties. Neutral cinchona alkaloids have been introduced intact in gas phase by laser-ablation. They have been studied by combining supersonic expansion with laser spectroscopy. The two pseudo-enantiomers Quinine and Quinidine show similar electronic and vibrational spectra, in line with simil...

  18. Surface control of alkyl chain conformations and 2D chiral amplification.

    Science.gov (United States)

    Hauptmann, Nadine; Scheil, Katharina; Gopakumar, Thiruvancheril G; Otte, Franziska L; Schütt, Christian; Herges, Rainer; Berndt, Richard

    2013-06-19

    Trioctyl-functionalized triazatriangulenium (trioctyl-TATA) deposited on Au(111) and Ag(111) surfaces by electrospray ionization was investigated using low-temperature scanning tunneling microscopy. The molecule surprisingly adsorbs with gauche rather than anti conformations of the octyl groups. We observed chiral amplification in the islands. Only one of the eight possible configurations of the octyl groups was found in homochiral hexagonal networks. Quantum-chemical calculations confirmed and explained the preference for the gauche conformations of adsorbed trioctyl-TATA.

  19. Chiral separation by (S)-naproxen imprinted monolithic column with mixed functional monomers

    Institute of Scientific and Technical Information of China (English)

    Zhen Ying Li; Zhao Sheng Liu; Qing Wei Zhang; Hong Quan Duan

    2007-01-01

    Molecularly imprinted polymers (MIPs), using (S)-naproxen as template and the combination of butyl methacrylate (BMA) and column was evaluated in HPLC mode. The result showed that the monolithic MIPs with the combination of two monomers produced better chiral resolution of rac-naproxen (Rs = 1.55) and column efficiencies of imprinted molecules (N = 2860 plates/m)than that with pure MAA.

  20. Chiral exceptional points in metasurfaces

    Science.gov (United States)

    Kang, Ming; Chen, Jing; Chong, Y. D.

    2016-09-01

    An exceptional point (EP) is a degeneracy occurring in a non-energy-conserving system, in which two eigenvectors of a non-Hermitian Hamiltonian coalesce. We explore how EPs can be realized in a metamaterial surface, or metasurface, consisting of a pair of lossy coupled linear antennas in each unit cell. EPs appear in the eigenvectors of the transmission matrix by tuning the frequency and the coupling and loss rates of the metasurface. Each EP is associated with the appearance of a circularly polarized transmission eigenstate; hence, within the parameter space of the system, the EPs lie along pairs of curves with distinct chirality. Our results are obtained using finite-difference time-domain simulations, as well as a fitted coupled-mode theory. The coupled-mode theory agrees well with the numerical results and is capable of accurately predicting the EP f curves.

  1. Spontaneous transfer of chirality in an atropisomerically enriched two-axis system.

    Science.gov (United States)

    Barrett, Kimberly T; Metrano, Anthony J; Rablen, Paul R; Miller, Scott J

    2014-05-01

    One of the most well-recognized stereogenic elements in a chiral molecule is an sp(3)-hybridized carbon atom that is connected to four different substituents. Axes of chirality can also exist about bonds with hindered barriers of rotation; molecules containing such axes are known as atropisomers. Understanding the dynamics of these systems can be useful, for example, in the design of single-atropisomer drugs or molecular switches and motors. For molecules that exhibit a single axis of chirality, rotation about that axis leads to racemization as the system reaches equilibrium. Here we report a two-axis system for which an enantioselective reaction produces four stereoisomers (two enantiomeric pairs): following a catalytic asymmetric transformation, we observe a kinetically controlled product distribution that is perturbed from the system's equilibrium position. As the system undergoes isomerization, one of the diastereomeric pairs drifts spontaneously to a higher enantiomeric ratio. In a compensatory manner, the enantiomeric ratio of the other diastereomeric pair decreases. These observations are made for a class of unsymmetrical amides that exhibits two asymmetric axes--one axis is defined through a benzamide substructure, and the other axis is associated with differentially N,N-disubstituted amides. The stereodynamics of these substrates provides an opportunity to observe a curious interplay of kinetics and thermodynamics intrinsic to a system of stereoisomers that is constrained to a situation of partial equilibrium.

  2. Chiral Magnetic Effect in Heavy Ion Collisions

    CERN Document Server

    Liao, Jinfeng

    2016-01-01

    The Chiral Magnetic Effect (CME) is a remarkable phenomenon that stems from highly nontrivial interplay of QCD chiral symmetry, axial anomaly, and gluonic topology. 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 $|\\vec{\\bf B}|\\sim m_\\pi^2$ are present during the early stage of such collisions. Significant efforts have been made to look for CME signals in heavy ion collision experiments. In this contribution we give a brief overview on the status of such efforts.

  3. Chirality in thiolate-protected gold clusters.

    Science.gov (United States)

    Knoppe, Stefan; Bürgi, Thomas

    2014-04-15

    Over recent years, research on thiolate-protected gold clusters Au(m)(SR)n has gained significant interest. Milestones were the successful determination of a series of crystal structures (Au102(SR)44, Au25(SR)18, Au38(SR)24, Au36(SR)24, and Au28(SR)20). For Au102(SR)44, Au38(SR)24, and Au28(SR)20, intrinsic chirality was found. Strong Cotton effects (circular dichroism, CD) of gold clusters protected by chiral ligands have been reported a long time ago, indicating the transfer of chiral information from the ligand into the cluster core. Our lab has done extensive studies on chiral thiolate-protected gold clusters, including those protected with chiral ligands. We demonstrated that vibrational circular dichroism can serve as a useful tool for the determination of conformation of the ligand on the surface of the cluster. The first reports on crystal structures of Au102(SR)44 and Au38(SR)24 revealed the intrinsic chirality of these clusters. Their chirality mainly arises from the arrangement of the ligands on the surface of the cluster cores. As achiral ligands are used to stabilize the clusters, racemic mixtures are obtained. However, the separation of the enantiomers by HPLC was demonstrated which enabled the measurement of their CD spectra. Thermally induced inversion allows determination of the activation parameters for their racemization. The inversion demonstrates that the gold-thiolate interface is anything but fixed; in contrast, it is rather flexible. This result is of fundamental interest and needs to be considered in future applications. A second line of our research is the selective introduction of chiral, bidentate ligands into the ligand layer of intrinsically chiral gold clusters. The ligand exchange reaction is highly diastereoselective. The bidentate ligand connects two of the protecting units on the cluster surface and thus effectively stabilizes the cluster against thermally induced inversion. A minor (but significant) influence of chiral ligands to

  4. Random matrix model approach to chiral symmetry

    CERN Document Server

    Verbaarschot, J J M

    1996-01-01

    We review the application of random matrix theory (RMT) to chiral symmetry in QCD. Starting from the general philosophy of RMT we introduce a chiral random matrix model with the global symmetries of QCD. Exact results are obtained for universal properties of the Dirac spectrum: i) finite volume corrections to valence quark mass dependence of the chiral condensate, and ii) microscopic fluctuations of Dirac spectra. Comparisons with lattice QCD simulations are made. Most notably, the variance of the number of levels in an interval containing $n$ levels on average is suppressed by a factor $(\\log n)/\\pi^2 n$. An extension of the random matrix model model to nonzero temperatures and chemical potential provides us with a schematic model of the chiral phase transition. In particular, this elucidates the nature of the quenched approximation at nonzero chemical potential.

  5. Chiral dynamics with (non)strange quarks

    Science.gov (United States)

    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.

  6. Chiral susceptibility and the scalar Ward identity.

    Energy Technology Data Exchange (ETDEWEB)

    Chang, L.; Liu, Y.-X.; Roberts, C. D.; Shi, Y.-M.; Sun, W.-M.; Zong, H.-S.; Physics; Inst. of Applied Physics and Computational Mathematics; Peking Univ.; National Lab. of Heavy Ion Accelerator; Univ. of New South Wales; Nanjing Univ.; Joint Center for Particle, Nuclear Physics and Cosmology

    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 the 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.

  7. New Advances in Chiral Catalyst Immobilization

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ Asymmetric catalysis of organic reactions is one of the most efficient ways to obtain optically pure chiral compounds, which are crucially important to the development of modern pharmaceutical and fine chemical industries, as well as material science.

  8. Notes on conservation laws in chiral hydrodynamics

    CERN Document Server

    Zakharov, V I

    2016-01-01

    We consider chiral fluids within the standard framework of a chiral-invariant underlying field theory, anomalous in presence of electromagnetic fields. Apart from the Noether axial current of the underlying theory, in the limit of ideal fluid there exist extra conserved currents, corresponding to classical helical motions. The extra conservation laws are known to break down once viscosity is non-vanishing. Which looks puzzling, as if introduction of viscosity were inconsistent with chiral invariance. As a resolution of the puzzle, we argue that locally one can introduce an inertial frame where an extra conservation law still holds. In other words, the extra currents are covariantly conserved. The emergent gravitational field is determined by dynamics of the viscous fluid. We turn then to instabilities of chiral plasma against decays into helical magnetic or vortical configurations. We emphasise similarity between the two cases in the far infrared region, responsible for the decays. This similarity is not appa...

  9. Application of cyclodextrins in chiral capillary electrophoresis.

    Science.gov (United States)

    Rezanka, Pavel; Navrátilová, Klára; Rezanka, Michal; Král, Vladimír; Sýkora, David

    2014-10-01

    CE represents a very powerful separation tool in the area of chiral separations. CD-mediated chiral CE is a continuously flourishing technique within the frame of the electromigration methods. In this review, a brief overview of the synthetic procedures leading to modified CDs is provided first. Next, selected aspects related to the utilization of CDs in chiral CE are discussed specifically in the view of recently published data. Advantages of CDs and basic principles of chiral CE are remained. The topic of the determination of binding constants is touched. Particular attention is paid to the effort aiming at better understanding of the molecular level of the enantiorecognition between CDs and the analyte in the solution. Powerful approaches extensively utilized in this field are NMR, molecular modeling, and computer simulations. Then, a summary of applications of CDs in the CE enantioseparations is given, covering years 2008-2013. Finally, the general trend of modified CDs use in separation science is statistically evaluated.

  10. Chiral transition of fundamental and adjoint quarks

    Energy Technology Data Exchange (ETDEWEB)

    Capdevilla, R.M. [Instituto de Física Teórica, UNESP – Universidade Estadual Paulista, Rua Dr. Bento T. Ferraz, 271, Bloco II, 01140-070 São Paulo, SP (Brazil); Doff, A., E-mail: agomes@utfpr.edu.br [Universidade Tecnológica Federal do Paraná – UTFPR – DAFIS, Av. Monteiro Lobato Km 04, 84016-210 Ponta Grossa, PR (Brazil); Natale, A.A., E-mail: natale@ift.unesp.br [Instituto de Física Teórica, UNESP – Universidade Estadual Paulista, Rua Dr. Bento T. Ferraz, 271, Bloco II, 01140-070 São Paulo, SP (Brazil); Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, 09210-170 Santo André, SP (Brazil)

    2014-01-20

    The chiral symmetry breaking transition of quarks in the fundamental and adjoint representation is studied in a model where the gap equation contains two contributions, one containing a confining propagator and another corresponding to the exchange of one-dressed dynamically massive gluons. When quarks are in the fundamental representation the confinement effect dominates the chiral symmetry breaking while the gluon exchange is suppressed due to the dynamical gluon mass effect in the propagator and in the coupling constant. In this case the chiral and deconfinement transition temperatures are approximately the same. For quarks in the adjoint representation, due to the larger Casimir eigenvalue, the gluon exchange is operative and the chiral transition happens at a larger temperature than the deconfinement one.

  11. NN Interaction in Chiral Constituent Quark Models

    CERN Document Server

    Valcarce, A; González, P

    2003-01-01

    We review the actual state in the description of the NN interaction by means of chiral constituent quark models. We present a series of relevant features that are nicely explained within the quark model framework.

  12. Selective adsorption and chiral amplification of amino acids in vermiculite clay-implications for the origin of biochirality.

    Science.gov (United States)

    Fraser, Donald G; Fitz, Daniel; Jakschitz, T; Rode, Bernd M

    2011-01-21

    Smectite clays are hydrated layer silicates that, like micas, occur naturally in abundance. Importantly, they have readily modifiable interlayer spaces that provide excellent sites for nanochemistry. Vermiculite is one such smectite clay and in the presence of small chain-length alkyl-NH(3)Cl ions forms sensitive, 1-D ordered model clay systems with expandable nano-pore inter-layer regions. These inter-layers readily adsorb organic molecules. n-Propyl NH(3)Cl vermiculite clay gels were used to determine the adsorption of alanine, lysine and histidine by chiral HPLC. The results show that during reaction with fresh vermiculite interlayers, significant chiral enrichment of either L- and D-enantiomers occurs depending on the amino acid. Chiral enrichment of the supernatant solutions is up to about 1% per pass. In contrast, addition to clay interlayers already reacted with amino acid solutions resulted in little or no change in D/L ratio during the time of the experiment. Adsorption of small amounts of amphiphilic organic molecules in clay inter-layers is known to produce Layer-by-Layer or Langmuir-Blodgett films. Moreover atomistic simulations show that self-organization of organic species in clay interlayers is important. These non-centrosymmetric, chirally active nanofilms may cause clays to act subsequently as chiral amplifiers, concentrating organic material from dilute solution and having different adsorption energetics for D- and L-enantiomers. The additional role of clays in RNA oligomerization already postulated by Ferris and others, together with the need for the organization of amphiphilic molecules and lipids noted by Szostak and others, suggests that such chiral separation by clays in lagoonal environments at normal biological temperatures might also have played a significant role in the origin of biochirality.

  13. Bringing chiral optical forces to dominance with optical nanofibers

    CERN Document Server

    Alizadeh, M H

    2016-01-01

    Transverse spin angular momentum (SAM) of light and associated transverse chiral optical forces have received tremendous attention recently as the latter may lead to an optical separation of chiral biomolecules. Previous schemes to generate chiral forces are plagued by the fact that the chiral optical forces are orders of magnitude smaller than conventional gradient and scattering forces. The relative magnitude of chiral and non-chiral forces represents a fundamental challenge for the implementation of chiral separation schemes. In this work we demonstrate that, by spatially separating the maxima of transverse spin density from the gradient of field intensity, in the vicinity of optical nanofibers and nanowires, chiral optical forces can emerge that are stronger than gradient and scattering forces. This finding has important implications for the design of improved optical separation schemes for chiral biomolecules.

  14. On the covariantization of the chiral constraints

    CERN Document Server

    Neves, C; Wotzasek, C; Neves, C; de Abreu, E M C; Wotzasek, C

    1995-01-01

    We show that a complete covariantization of the chiral constraint in the Floreanini-Jackiw necessitates an infinite number of auxiliary Wess-Zumino fields otherwise the covariantization is only partial and unable to remove the nonlocality in the chiral boson operator. We comment on recent works that claim to obtain covariantization through the use of Batalin-Fradkin-Tyutin method, that uses just one Wess-Zumino field.

  15. Lattice quantum chromodynamics with approximately chiral fermions

    Energy Technology Data Exchange (ETDEWEB)

    Hierl, Dieter

    2008-05-15

    In this work we present Lattice QCD results obtained by approximately chiral fermions. We use the CI fermions in the quenched approximation to investigate the excited baryon spectrum and to search for the {theta}{sup +} pentaquark on the lattice. Furthermore we developed an algorithm for dynamical simulations using the FP action. Using FP fermions we calculate some LECs of chiral perturbation theory applying the epsilon expansion. (orig.)

  16. Open Problems in Understanding the Nuclear Chirality

    CERN Document Server

    Meng, Jie

    2010-01-01

    Open problems in the interpretation of the observed pair of near degenerate $\\Delta I = 1$ bands with the same parity as the chiral doublet bands are discussed. The ambiguities for the existing fingerprints of the chirality in atomic nuclei and problems in existing theory are discussed, including the description of quantum tunneling in the mean field approximation as well as the deformation, core polarization and configuration of particle rotor model (PRM). Future developments of the theoretical approach are prospected.

  17. Insights on some chiral smectic phases

    Indian Academy of Sciences (India)

    B Pansu

    2003-08-01

    Combining layered positional order as smectic order and chirality can generate complex architectures since twist parallel to the layers is not allowed. This paper will review some new experimental results on different phases resulting from the competition between smectic positional order and twist orientational order. It concerns the TGBA and the NL*, that is the liquid line phase as well as the SmQ phase. Chiral effects in the isotropic phase will also be discussed.

  18. Chiral symmetry and lattice gauge theory

    CERN Document Server

    Creutz, M

    1994-01-01

    I review the problem of formulating chiral symmetry in lattice gauge theory. I discuss recent approaches involving an infinite tower of additional heavy states to absorb Fermion doublers. For hadronic physics this provides a natural scheme for taking quark masses to zero without requiring a precise tuning of parameters. A mirror Fermion variation provides a possible way of extending the picture to chirally coupled light Fermions. Talk presented at "Quark Confinement and the Hadron Spectrum," Como, Italy, 20-24 June 1994.

  19. Chiral symmetry and the constituent quark model

    CERN Document Server

    Glozman, L Ya

    1995-01-01

    New results on baryon structure and spectrum developed in collaboration with Dan Riska [1-4] are reported. The main idea is that beyond the chiral symmetry spontaneous breaking scale light and strange baryons should be considered as systems of three constituent quarks with an effective confining interaction and a chiral interaction that is mediated by the octet of Goldstone bosons (pseudoscalar mesons) between the constituent quarks.

  20. Baryons in chiral constituent quark model

    CERN Document Server

    Glozman, L Ya

    1996-01-01

    Beyond the spontaneous chiral symmetry breaking scale light and strange baryons should be considered as systems of three constituent quarks with an effective confining interaction and a flavor-spin chiral interaction that is mediated by the octet of Goldstone bosons (pseudoscalar mesons) between the constituent quarks. One cannot exclude, however, the possibility that this flavor-spin interaction has an appreciable vector- and higher meson exchange component.

  1. Radiopolymerization of {beta}(-)pinene: A case of chiral amplification

    Energy Technology Data Exchange (ETDEWEB)

    Cataldo, Franco [Soc. Lupi Chemical Research, Via Casilina 1626/A, 00133 Rome (Italy)]. E-mail: cdcata@flashnet.it; Keheyan, Yeghis [CNR, Istituto per lo studio dei Materiali Nanostrutturati, Department of Chemistry, University ' La Sapienza' , P.le Aldo Moro 1, Rome (Italy)

    2006-05-15

    {beta}(-)Pinene was treated with {gamma} radiation at three dose levels: 150, 300 and 600 kGy. The expected effect of radiation at these high doses was the partial racemization of the substrate as already observed in the case of other terpene monomers. Unexpectedly {beta}(-)pinene underwent a radiopolymerization reaction into a solid resin and into a dimer. The structure of the products was studied by FT-IR spectroscopy also in comparison to a reference {beta}(-)pinene resin prepared by cationic polymerization. A highly ordered structure was found in the case of the radiopolymer in comparison to the resin from cationic polymerization. Polarimetric measurements have shown astonishing enhancement in the optical activity of the radiopolymer and radiodimer in comparison to the starting optical activity of the {beta}(-)pinene monomer. The results have been discussed in terms of amplification of chirality caused by {gamma} radiation and the implications of this fact on the mechanism of chiral amplification on prebiotic molecules.

  2. Isocyanurates with planar chirality: design, optical resolution, and isomerization.

    Science.gov (United States)

    Goto, Hidetoshi; Sudoh, Masanao; Kawamoto, Keiko; Sugimoto, Hiroshi; Inoue, Shohei

    2012-10-01

    Designs and syntheses of isocyanurates (1-3) are described on the basis of a novel concept that two enantiotopic faces of C(s) -symmetric, prochiral planar molecules are differentiated with a location of groups at the top or bottom of the planar skeleton using a rigid linker. Such isocyanurates are atropisomeric. The planar-chiral structures of 1 and 2(anti) (anti-conformer of 2) were confirmed by single-crystal X-ray analyses, and the space groups were P1 (for 1) and P2(1)/c (for 2(anti)), resulting that the crystals were racemates. Optical resolutions of 1-3 were successfully accomplished by using chiral high-performance liquid chromatography technique in combination with circular dichroism, absorption, and nuclear magnetic resonance spectroscopies and mass spectrometry. Furthermore, the rotational barriers (ΔG(‡)s) related to isomerizations of 1-3 were estimated to be 27.2 (for 1 at 50 °C), 27.6 (for 2(anti) at 50 °C), and 40.6 (for 3(syn) at 150 °C) kcal/mol. The ΔG(‡)s of 2 and 3 were higher than that of 1 and, in particular, that of 3 was highest among them. This result indicates that an introduction of bulky substituents and an intramolecular bridging are effective for inhibitions of the isomerizations.

  3. Chirality and chiroptical properties of amyloid fibrils.

    Science.gov (United States)

    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.

  4. CHIRAL CONJUGATED OLIGOMER BASED ON 1,1'-BINOL WITH 3,3'-ACETYLENE-PHENYLENE-ACETYLENE SPACER

    Institute of Scientific and Technical Information of China (English)

    Tian-jun Liu; Ke-shen Zhang; Yong-jun Chen; Dong Wang; Chao-jun Li

    2001-01-01

    The 1,1'-binaphthol based oligomers 3 and 7 with 3,3'-acetylene-phenylene-acetylene spacer were prepared from BINOL 1. The high optical rotation value and CD spectra demonstrated the main chain chirality of the oligomer molecule. The UV-VIS and fluorescent spectra evidence the characteristics of conjugated structure. In comparison with oligomer 2 bearing 3,3'-acetylene spacer, the oligomers 3 and 7 have longer efficient conjugation segment, and their fluorescent quantum yields (φ) increased (0.60-0.65 versus 0.14). Extending the effective conjugation segment would improve the photophysical properties of chiral conjugated polymers.``

  5. Developing a Practical Chiral Toolbox for Asymmetric Catalytic Reactions

    Institute of Scientific and Technical Information of China (English)

    ZHANG XuMu

    2001-01-01

    @@ Chiral Quest's Toolbox Approach: During the last several decades, chemists have made major progress in discovering man-made catalysts to perform challenging asymmetric transformations. However, there is no universal chiral ligand or catalyst for solving problems in enantioselective transformations. The focus of Chiral Quest's research is to develop a useful chiral toolbox for strategically important asymmetric catalytic reactions by inventing a diverse set of novel chiral ligands and combining them with transition metals as effective enantioselective catalysts. The toolbox approach addresses significant problems in organic stereochemistry and has resulted in practical methods for the synthesis of chiral pharmaceuticals and agrochemicals

  6. Developing a Practical Chiral Toolbox for Asymmetric Catalytic Reactions

    Institute of Scientific and Technical Information of China (English)

    ZHANG; XuMu

    2001-01-01

    Chiral Quest's Toolbox Approach: During the last several decades, chemists have made major progress in discovering man-made catalysts to perform challenging asymmetric transformations. However, there is no universal chiral ligand or catalyst for solving problems in enantioselective transformations. The focus of Chiral Quest's research is to develop a useful chiral toolbox for strategically important asymmetric catalytic reactions by inventing a diverse set of novel chiral ligands and combining them with transition metals as effective enantioselective catalysts. The toolbox approach addresses significant problems in organic stereochemistry and has resulted in practical methods for the synthesis of chiral pharmaceuticals and agrochemicals  ……

  7. 识别手性六螺烯分子的计算机模拟%Computer Simulation on Recognition of Chiral Hexahelicenes

    Institute of Scientific and Technical Information of China (English)

    孙凯; 李霆; 梁太宁; 杨小震

    2001-01-01

    Molecular interactions are the key to understanding the structure and properties of materials. Also, it is critical of chiral recognition. Since the molecular interactions at play in chiral discrimination is difficult to investigate under traditional experiment conditions. We have undertaken a computer experiment of van der Waals interaction between chiral molecules and a polymer, which works for chiral separation. Building molecular models, choosing proper force field and Monte Carlo method, we have calculated the difference of interaction energy between isotactic poly-(triphenylmethyl methacrylate) and (+)-hexahelicene or (-)-hexahelicene. It is finally found about 1.379 4 kJ/mol between the polymer and the two chiral hexahelicenes. Reasonably, this difference is regardd as the main reason which induced chiral separation. Furthermore, we compared the results from computer smulation with that from experiment. It can be seen that some details during chiral separation process, such as trailing effect, can also be predicted, and be consistent with the experiment results. Finally, the effective structureal characteristics of the recognition site are pointed out.

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Guo Zhen; Liu Xianbin; Ng, Siu-Choon; Chen Yuan; Yang Yanhui [School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore 637459 (Singapore); Du Yu, E-mail: du_yu@jlu.edu.cn, E-mail: yhyang@ntu.edu.sg [College of Electronic Science and Engineering, Jilin University, Changchun 130012 (China)

    2010-04-23

    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.

  10. The asymmetric alkylation of dimethylhydrazones; intermolecular chirality transfer using sparteine as chiral ligand.

    Science.gov (United States)

    McSweeney, Christina M; Foley, Vera M; McGlacken, Gerard P

    2014-12-01

    The asymmetric alkylation of ketones represents a fundamental transformation in organic chemistry. Chiral auxiliaries have been used almost exclusively for this transformation. Herein we describe a strategy for the generation of enantiomerically enriched α-alkylated ketones up to an er of 83 : 17, using a chiral ligand protocol.

  11. Chirality, photochemistry and the detection of amino acids in interstellar ice analogues and comets.

    Science.gov (United States)

    Evans, Amanda C; Meinert, Cornelia; Giri, Chaitanya; Goesmann, Fred; Meierhenrich, Uwe J

    2012-08-21

    The primordial appearance of chiral amino acids was an essential component of the asymmetric evolution of life on Earth. In this tutorial review we will explore the original life-generating, symmetry-breaking event and summarise recent thoughts on the origin of enantiomeric excess in the universe. We will then highlight the transfer of asymmetry from chiral photons to racemic amino acids and elucidate current experimental data on the photochemical synthesis of amino and diamino acid structures in simulated interstellar and circumstellar ice environments. The chirality inherent within actual interstellar (cometary) ice environments will be considered in this discussion: in 2014 the Rosetta Lander Philae onboard the Rosetta space probe is planned to detach from the orbiter and soft-land on the surface of the nucleus of comet 67P/Churyumov-Gerasimenko. It is equipped for the in situ enantioselective analysis of chiral prebiotic organic species in cometary ices. The scientific design of this mission will therefore be presented in the context of analysing the formation of amino acid structures within interstellar ice analogues as a means towards furthering understanding of the origin of asymmetric biological molecules.

  12. Intermolecular chiral assemblies in R(-) and S(+) 2-butanol detected by microcalorimetry measurements.

    Science.gov (United States)

    Cogan, Uri; Shpigelman, Avi; Portnaya, Irina; Rutenberg, Abraham; Scolnik, Yosef; Shinitzky, Meir

    2012-07-01

    Supramolecular chiral assemblies of R(-) and S(+) 2-butanol, in their neat form or when dissolved in their nonchiral isomer isobutanol, were evaluated by isothermal titration calorimetry (ITC) ensuing mixing. Dilution of 0.5 M solution of R(-) 2-butanol in isobutanol into the latter liberated heat of several calories per mole, which was approximately double than that obtained in parallel dilutions of S(+) 2-butanol in isobutanol. The ITC dilution profiles indicated an estimate of about 100 isobutanol solvent molecules surrounding each of the 2-butanol enantiomers, presumably arranged in chiral configurations, with different adopted order between the isomers. Mixings of neat R and S 2-butanol were followed by endothermic ITC profiles, indicating that, in racemic 2-butanol, both the supramolecular order and the intermolecular binding energies are lower than in each of the neat chiral isomers. The diversion from symmetrical ITC patterns in these mixings indicated again a subtle difference in molecular organization between the neat enantiomers. It should be noted that the presence of impurities, α-pinene and teterhydrofuran, at a level totaling 0.5%, did not influence the ITC heat flow profiles. The findings of this study demonstrate for the first time that chiral solutes in organic solvents are expected to acquire asymmetric solvent envelopes that may be different between the enantiomers, thus broadening this phenomenon beyond the previously demonstrated cases in aqueous solutions.

  13. A relativistic neutron fireball from a supernova explosion as a possible source of chiral influence.

    Science.gov (United States)

    Gusev, G A; Saito, T; Tsarev, V A; Uryson, A V

    2007-06-01

    We elaborate on a previously proposed idea that polarized electrons produced from neutrons, released in a supernova (SN) explosion, can cause chiral dissymmetry of molecules in interstellar gas-dust clouds. A specific physical mechanism of a relativistic neutron fireball with Lorentz factor of the order of 100 is assumed for propelling a great number of free neutrons outside the dense SN shell. A relativistic chiral electron-proton plasma, produced from neutron decays, is slowed down owing to collective effects in the interstellar plasma. As collective effects do not involve the particle spin, the electrons can carry their helicities to the cloud. The estimates show high chiral efficiency of such electrons. In addition to this mechanism, production of circularly polarized ultraviolet photons through polarized-electron bremsstrahlung at an early stage of the fireball evolution is considered. It is shown that these photons can escape from the fireball plasma. However, for an average density of neutrals in the interstellar medium of the order of 0.2 cm(-3) and at distances of the order of 10 pc from the SN, these photons will be absorbed with a factor of about 10(-7) due to the photoeffect. In this case, their chiral efficiency will be about five orders of magnitude less than that for polarized electrons.

  14. Chiral morphology of calcite through selective binding of amino acids

    Science.gov (United States)

    Orme, Christine

    2002-03-01

    Many living organisms contain biominerals and composites with finely tuned properties, reflecting a remarkable level of control over the nucleation, growth and shape of the constituent crystals. Peptides and proteins play an important role in achieving this control. Using in situ AFM we find that site-specific binding of amino acid residues to surface steps changes the step-edge free energies, giving rise to direction-specific binding energies unique to individual amino acid enantiomers and leading to chiral modifications that propagate from atomic length scales to macroscopic length scales. Molecular modeling studies support an energetic basis for the differences in binding. Our results emphasize that the mechanism under-lying crystal modification through organic molecules is best understood by considering both stereochemical recognition as well as the effects of binding on the interfacial energies of the growing crystal.

  15. Chiral separation of racemic drugs using molecular imprinting

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Molecularly imprinted polymers (MIPs) of (S)-ketoprofen and (S)-naproxen are prepared using non-covalent imprinting in the presence of template molecules. The prepared MIPs are used as the chiral stationary phase to separate ramemic naproxen and ketoprofen. The results show that racemic naproxen and ketoprofen are efficiently resolved on MIPs. The effect of concentration of acetic acid in the mobile phase is studied, and the data are analyzed using the affinity chromatography model, and the close agreement is achieved between the simulated and experimental curves. The results suggest that the affinity chromatography mechanism controls the retention in this system. Moreover, the affinity chromatography equilibrium constants on (S)-naproxen and (S)-ketoprofen are estimated.

  16. Hidden topological constellations and polyvalent charges in chiral nematic droplets

    Science.gov (United States)

    Posnjak, Gregor; Čopar, Simon; Muševič, Igor

    2017-02-01

    Topology has an increasingly important role in the physics of condensed matter, quantum systems, material science, photonics and biology, with spectacular realizations of topological concepts in liquid crystals. Here we report on long-lived hidden topological states in thermally quenched, chiral nematic droplets, formed from string-like, triangular and polyhedral constellations of monovalent and polyvalent singular point defects. These topological defects are regularly packed into a spherical liquid volume and stabilized by the elastic energy barrier due to the helical structure and confinement of the liquid crystal in the micro-sphere. We observe, for the first time, topological three-dimensional point defects of the quantized hedgehog charge q=-2, -3. These higher-charge defects act as ideal polyvalent artificial atoms, binding the defects into polyhedral constellations representing topological molecules.

  17. Hidden topological constellations and polyvalent charges in chiral nematic droplets

    Science.gov (United States)

    Posnjak, Gregor; Čopar, Simon; Muševič, Igor

    2017-01-01

    Topology has an increasingly important role in the physics of condensed matter, quantum systems, material science, photonics and biology, with spectacular realizations of topological concepts in liquid crystals. Here we report on long-lived hidden topological states in thermally quenched, chiral nematic droplets, formed from string-like, triangular and polyhedral constellations of monovalent and polyvalent singular point defects. These topological defects are regularly packed into a spherical liquid volume and stabilized by the elastic energy barrier due to the helical structure and confinement of the liquid crystal in the micro-sphere. We observe, for the first time, topological three-dimensional point defects of the quantized hedgehog charge q=−2, −3. These higher-charge defects act as ideal polyvalent artificial atoms, binding the defects into polyhedral constellations representing topological molecules. PMID:28220770

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

    Science.gov (United States)

    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.

  19. Chiral dynamics and peripheral transverse densities

    Energy Technology Data Exchange (ETDEWEB)

    Granados, Carlos G. [Uppsala University (Sweden); Weiss, Christian [JLAB, Newport News, VA (United States)

    2014-01-01

    In the partonic (or light-front) description of relativistic systems the electromagnetic form factors are expressed in terms of frame-independent charge and magnetization densities in transverse space. This formulation allows one to identify the chiral components of nucleon structure as the peripheral densities at transverse distances b = O(M{sub {pi}}{sup -1}) and compute them in a parametrically controlled manner. A dispersion relation connects the large-distance behavior of the transverse charge and magnetization densities to the spectral functions of the Dirac and Pauli form factors near the two--pion threshold at timelike t = 4 M{ sub {pi}}{sup 2}, which can be computed in relativistic chiral effective field theory. Using the leading-order approximation we (a) derive the asymptotic behavior (Yukawa tail) of the isovector transverse densities in the "chiral" region b = O(M{sub {pi}}{sup -1}) and the "molecular" region b = O(M{sub N}{sup 2}/M{sub {pi}}{sup 3}); (b) perform the heavy-baryon expansion of the transverse densities; (c) explain the relative magnitude of the peripheral charge and magnetization densities in a simple mechanical picture; (d) include Delta isobar intermediate states and study the peripheral transverse densities in the large-N{ sub c} limit of QCD; (e) quantify the region of transverse distances where the chiral components of the densities are numerically dominant; (f) calculate the chiral divergences of the b{sup 2}-weighted moments of the isovector transverse densities (charge and anomalous magnetic radii) in the limit M{sub {pi}} -> 0 and determine their spatial support. Our approach provides a concise formulation of the spatial structure of the nucleon's chiral component and offers new insights into basic properties of the chiral expansion. It relates the information extracted from low-t elastic form factors to the generalized parton distributions probed in peripheral high-energy scattering processes.

  20. Molecular chirality in meteorites and interstellar ices, and the chirality experiment on board the ESA cometary Rosetta mission.

    Science.gov (United States)

    Myrgorodska, Iuliia; Meinert, Cornelia; Martins, Zita; Le Sergeant d'Hendecourt, Louis; Meierhenrich, Uwe J

    2015-01-26

    Life, as it is known to us, uses exclusively L-amino acid and D-sugar enantiomers for the molecular architecture of proteins and nucleic acids. This Minireview explores current models of the original symmetry-breaking influence that led to the exogenic delivery to Earth of prebiotic molecules with a slight enantiomeric excess. We provide a short overview of enantiomeric enhancements detected in bodies of extraterrestrial origin, such as meteorites, and interstellar ices simulated in the laboratory. Data are interpreted from different points of view, namely, photochirogenesis, parity violation in the weak nuclear interaction, and enantioenrichment through phase transitions. Photochemically induced enantiomeric imbalances are discussed more specifically in the topical context of the "chirality module" on board the cometary Rosetta spacecraft of the ESA. This device will perform the first enantioselective in situ analyses of samples taken from a cometary nucleus.

  1. On the interplay between chirality and exciton coupling: a DFT calculation of the circular dichroism in π-stacked ethylene.

    Science.gov (United States)

    Norman, Patrick; Linares, Mathieu

    2014-09-01

    The chirality of stacked weakly interacting π-systems was interpreted in terms of Frenkel exciton states and the formation of excitonic circular dichroism (CD) bands was monitored for ethylene stacks of varying sizes. Convergence of CD bands with respect to the system size was observed for stacks involving around 10 molecules. By means of rotation around the C-C double bond in ethylene, chirality was induced in the monomeric system and which was shown to dominate the spectral responses, even for polymer aggregates. In helical assemblies of chiral entities, there will always be a mix of excitonic and monomeric contributions to the CD signal and it is demonstrated that the complex polarization propagator approach in combination with Density Functional Theory is a suitable method to address this situation.

  2. A chiral rhenium complex with predicted high parity violation effects: synthesis, stereochemical characterization by VCD spectroscopy and quantum chemical calculations

    CERN Document Server

    Saleh, Nidal; Roisnel, Thierry; Guy, Laure; Bast, Radovan; Saue, Trond; Darquié, Benoît; Crassous, Jeanne

    2015-01-01

    With their rich electronic, vibrational, rotational and hyperfine structure, molecular systems have the potential to play a decisive role in precision tests of fundamental physics. For example, electroweak nuclear interactions should cause small energy differences between the two enantiomers of chiral molecules, a signature of parity symmetry breaking. Enantioenriched oxorhenium(VII) complexes S-(-)- and R-(+)-3 bearing a chiral 2-methyl-1-thio-propanol ligand have been prepared as potential candidates for probing molecular parity violation effects via high resolution laser spectroscopy of the Re=O stretching. Although the rhenium atom is not a stereogenic centre in itself, experimental vibrational circular dichroism (VCD) spectra revealed a surrounding chiral environment, evidenced by the Re=O bond stretching mode signal. The calculated VCD spectrum of the R enantiomer confirmed the position of the sulfur atom cis to the methyl, as observed in the solid-state X-ray crystallographic structure, and showed the ...

  3. Theoretical Investigation on the Second-order Nonlinear Optical Properties of Chiral Amino Acid Zinc(Ⅱ) Porphyrins

    Institute of Scientific and Technical Information of China (English)

    LIU Hai-Yang; TIAN Jun-Chun; YING Xiao; XU Zhi-Guang; LIAO Shi-Jun; CHANG Chi-Kwong

    2005-01-01

    Static second-order nonlinear optical effects of amino acid zinc(II) porphyrins 1, 2, 3 and 4 were calculated by the TDHF/PM3 method based on the molecular structures optimized at the semiempirical PM3 quantum chemistry level, showing due to the cancellation of symmetric center, these amino acid zinc(II) porphyrins exhibit second order nonlinear optical response. The analysis of β components indicated that these amino acid zinc(II) porphyrins are of multipolarizabilities, and they may be ascribed as the "mixture" of octupolar and dipoar molecules with ||βJ=3||/||βJ=1|| ≈ 5. It is found that there are no significant differences between the static β values of non-chiral and chiral amino acid zinc(II) porphyrins. However, the βxyz component, which is quite important to quadratic macroscopic х (2) susceptibility of chiral material, is increased significantly with the increase of side chain group of amino acids.

  4. Use of cage molecules for cleansing and chemical analysis; Utilisations de molecules cages pour la depollution et l'analyse chimique

    Energy Technology Data Exchange (ETDEWEB)

    Janus, L.

    2003-06-15

    Cage molecules are capable to include a large variety of compounds, and to release them without any modification. This 'host'-'guest' or 'receptor'-'substrate' association concept is commonly encountered in the biological domains, and thus cage molecules can imitate a natural process. In this work 4 types of cage molecules have been used: beta-cyclo-dextrin and two of its derivatives, and tetra-pyrazole macrocycles. Polymer supports carrying these different molecules have been elaborated by different ways (grafting, polymerization, coating of a pre-existing mineral support) and have been used for two types of applications: cleansing and chiral recognition. The targeted pollutants are the toxic aromatic compounds and the heavy metals. The chiral recognition is performed by capillary electrophoresis and high-performance liquid chromatography techniques. (J.S.)

  5. Diffusion of active chiral particles

    Science.gov (United States)

    Sevilla, Francisco J.

    2016-12-01

    The diffusion of chiral active Brownian particles in three-dimensional space is studied analytically, by consideration of the corresponding Fokker-Planck equation for the probability density of finding a particle at position x and moving along the direction v ̂ at time t , and numerically, by the use of Langevin dynamics simulations. The analysis is focused on the marginal probability density of finding a particle at a given location and at a given time (independently of its direction of motion), which is found from an infinite hierarchy of differential-recurrence relations for the coefficients that appear in the multipole expansion of the probability distribution, which contains the whole kinematic information. This approach allows the explicit calculation of the time dependence of the mean-squared displacement and the time dependence of the kurtosis of the marginal probability distribution, quantities from which the effective diffusion coefficient and the "shape" of the positions distribution are examined. Oscillations between two characteristic values were found in the time evolution of the kurtosis, namely, between the value that corresponds to a Gaussian and the one that corresponds to a distribution of spherical shell shape. In the case of an ensemble of particles, each one rotating around a uniformly distributed random axis, evidence is found of the so-called effect "anomalous, yet Brownian, diffusion," for which particles follow a non-Gaussian distribution for the positions yet the mean-squared displacement is a linear function of time.

  6. Magnetohydrodynamics of Chiral Relativistic Fluids

    CERN Document Server

    Boyarsky, Alexey; Ruchayskiy, Oleg

    2015-01-01

    We study the dynamics of a plasma of charged relativistic fermions at very high temperature $T\\gg m$, where $m$ is the fermion mass, coupled to the electromagnetic field. In particular, we derive a magneto-hydrodynamical description of the evolution of such a plasma. We show that, as compared to conventional MHD for a plasma of non-relativistic particles, the hydrodynamical description of the relativistic plasma involves new degrees of freedom described by a pseudo-scalar field originating in a local asymmetry in the densities of left-handed and right-handed fermions. This field can be interpreted as an effective axion field. Taking into account the chiral anomaly we present dynamical equations for the evolution of this field, as well as of other fields appearing in the MHD description of the plasma. Due to its non-linear coupling to helical magnetic fields, the axion field significantly affects the dynamics of a magnetized plasma and can give rise to a novel type of inverse cascade.

  7. Chiral heteropoly blues and controllable switching of achiral polyoxometalate clusters.

    Science.gov (United States)

    Wang, Yizhan; Li, Haolong; Wu, Che; Yang, Yang; Shi, Lei; Wu, Lixin

    2013-04-22

    Managing the blues: Chiral heteropoly blues of achiral polyoxometalate clusters were created through an intermolecular interaction with a chiral organic compound. Controllable chiroptical switching of the cluster complexes was possible through reversible photochromism of the polyoxometalates (see picture).

  8. Spontaneous chiral symmetry breaking in the Tayler instability

    CERN Document Server

    Del Sordo, Fabio; Brandenburg, Axel; Mitra, Dhrubaditya

    2011-01-01

    The chiral symmetry breaking properties of the Tayler instability are discussed. Effective amplitude equations are determined in one case. This model has three free parameters that are determined numerically. Comparison with chiral symmetry breaking in biochemistry is made.

  9. Enantioselective catalytic syntheses of alpha-branched chiral amines

    DEFF Research Database (Denmark)

    Brase, S.; Baumann, T.; Dahmen, S.

    2007-01-01

    Chiral amines play a pivotal role in fine chemical and natural product syntheses and the design of novel materials.......Chiral amines play a pivotal role in fine chemical and natural product syntheses and the design of novel materials....

  10. Radiation and scattering from thin wires in chiral media

    Science.gov (United States)

    Jaggard, Dwight L.; Liu, John C.; Grot, Annette; Pelet, Philippe

    1992-11-01

    The effect of chirality on thin win antennas and scatterers in unbounded chiral material is examined through the application of fundamental principles and the examination of several canonical examples. In particular, the interplay between normalized chirality and wire length is investigated to classify radiation and scattering patterns. Chirality induces rapid decay in the currents on such wires, resulting in mountain-peak-shaped current distributions characteristic of wire antennas and bow-tie-shaped current distributions characteristic of wire scatterers of sufficient length. These current distributions, in turn, cause radiation and scattering patterns which exhibit a chirality-dependent forbidden zone for both antennas and scatterers. In this zone, the fields are greatly reduced. These distinctive results lead naturally to the classification of wire scattering and radiation into subchiral, chiral, and superchiral regimes. All results are understood from the underlying physical principles of electromagnetic chirality, and are related to values of a dimensionless parameter involving normalized chirality and normalized wire length.

  11. The Practical Asymmetric Syntheses of Key Chiral Intermediates of Chiral Drug from Four-Carbon Chiral Pool

    Institute of Scientific and Technical Information of China (English)

    MI AiQiao; LIN WenQin; HE Zhe; JIN Yi; JIANG YaoZhong

    2001-01-01

    @@ (S)-or (R)-2-Amino-4-phenylbutyric acid and (S)-or (R)-2-hydroxy-4-phenylbutyric acid and their ethyl esters are key chiral intermediates for the preparation of angiotensin converting enzyme inhibitors (ACEI) and other chiral drugs. Their practically asymmetric synthetic methods in large scale from four-carbon chiral pool, commercially available L-aspartic acid and L-malic acid, will be presented (as scheme). (S)-2-Amino-4-phenylbutyric acid and its ethyl ester hydrochloride were prepared from the easily available L-aspartic acid via activation by forming anhydride hydrochloride, Friedel-Crafts reaction with benzene, hydrogenolysis and esterification with ethanol in the presence of thionyl chloride in overall yield of 80% and 73.6% respectively with 99% ee. We first used amino acid anhydride hydrochloride as the acylating agent in Friedel-Crafts reaction without racemization. [1

  12. The Practical Asymmetric Syntheses of Key Chiral Intermediates of Chiral Drug from Four-Carbon Chiral Pool

    Institute of Scientific and Technical Information of China (English)

    MI; AiQiao

    2001-01-01

    (S)-or (R)-2-Amino-4-phenylbutyric acid and (S)-or (R)-2-hydroxy-4-phenylbutyric acid and their ethyl esters are key chiral intermediates for the preparation of angiotensin converting enzyme inhibitors (ACEI) and other chiral drugs. Their practically asymmetric synthetic methods in large scale from four-carbon chiral pool, commercially available L-aspartic acid and L-malic acid, will be presented (as scheme).  (S)-2-Amino-4-phenylbutyric acid and its ethyl ester hydrochloride were prepared from the easily available L-aspartic acid via activation by forming anhydride hydrochloride, Friedel-Crafts reaction with benzene, hydrogenolysis and esterification with ethanol in the presence of thionyl chloride in overall yield of 80% and 73.6% respectively with 99% ee. We first used amino acid anhydride hydrochloride as the acylating agent in Friedel-Crafts reaction without racemization. [1]……

  13. Rotating pigment cells exhibit an intrinsic chirality.

    Science.gov (United States)

    Yamanaka, Hiroaki; Kondo, Shigeru

    2015-01-01

    In multicellular organisms, cell properties, such as shape, size and function are important in morphogenesis and physiological functions. Recently, 'cellular chirality' has attracted attention as a cellular property because it can cause asymmetry in the bodies of animals. In recent in vitro studies, the left-right bias of cellular migration and of autonomous arrangement of cells under some specific culture conditions were discovered. However, it is difficult to identify the molecular mechanism underlying their intrinsic chirality because the left-right bias observed to date is subtle or is manifested in the stable orientation of cells. Here, we report that zebrafish (Danio rerio) melanophores exhibit clear cellular chirality by unidirectional counterclockwise rotational movement under isolated conditions without any special settings. The chirality is intrinsic to melanophores because the direction of the cellular rotation was not affected by the type of extracellular matrix. We further found that the cellular rotation was generated as a counter action of the clockwise movement of actin cytoskeleton. It suggested that the mechanism that directs actin cytoskeleton in the clockwise direction is pivotal for determining cellular chirality.

  14. [Preparations and biological properties of chiral compounds].

    Science.gov (United States)

    Sinko, Goran

    2005-12-01

    Enantiomers of chiral compounds may express various biological activities and also different toxicities. Examples of different pharmacological effects of some chiral drugs such as fluoxetine, penicillamine, ibuprofen and albuterol are provided in this paper. Due to possible differences in activity, the chiral drugs are required to be pure enantiomeric compounds in order to be more effective and safer to use. In the laboratory, enantiomers are mainly synthesized as racemates (an equimolar mixture of enantiomers) while in biological pathways only one enantiomeric form is produced, such as amino acids, sugars and lipids. This paper presents the principles of chirality, general information about enantiomers and their biological aspects. It gives an outline of stereoselective methods for chromatographic resolution of enantiomers with stereoselective protein stationary phases, i.e. capillary electrochromatography (CEC) and high performance liquid chromatography (HPLC). The use of enzyme biotransformations (hydrolysis, oxidation and reduction) in chiral syntheses of carboxyl-, phosphoryl- or beta-hydroxy esters, alcohols, epoxides and cis-carboxyl sulphoxide is described. This article also includes an example of lipase stereoselectivity improvement by amino acid mutations within the enzyme active site.

  15. On the chiral imbalance and Weibel instabilities

    Science.gov (United States)

    Kumar, Avdhesh; Bhatt, Jitesh R.; Kaw, P. K.

    2016-06-01

    We study the chiral-imbalance and the Weibel instabilities in presence of the quantum anomaly using the Berry-curvature modified kinetic equation. We argue that in many realistic situations, e.g. relativistic heavy-ion collisions, both the instabilities can occur simultaneously. The Weibel instability depends on the momentum anisotropy parameter ξ and the angle (θn) between the propagation vector and the anisotropy direction. It has maximum growth rate at θn = 0 while θn = π / 2 corresponds to a damping. On the other hand the pure chiral-imbalance instability occurs in an isotropic plasma and depends on difference between the chiral chemical potentials of right and left-handed particles. It is shown that when θn = 0, only for a very small values of the anisotropic parameter ξ ∼ξc, growth rates of the both instabilities are comparable. For the cases ξc Weibel modes dominate over the chiral-imbalance instability if μ5 / T ≤ 1. However, when μ5 / T ≥ 1, it is possible to have dominance of the chiral-imbalance modes at certain values of θn for an arbitrary ξ.

  16. Helical Ordering in Chiral Block Copolymers

    Science.gov (United States)

    Zhao, Wei; Hong, Sung Woo; Chen, Dian; Grason, Gregory; Russell, Thomas

    2012-02-01

    Introducing molecular chirality into the segments of block copolymers can influence the nature of the resultant morphology. Such an effect was found for poly(styrene-b-L-lactide) (PS-b-PLLA) diblock copolymers where hexagonally packed PLLA helical microdomains (H* phase) form in a PS matrix. However, molecular ordering of PLLA within the helical microdomains and the transfer of chirality from the segmental level to the mesoscale is still not well understood. We developed a field theoretic model to describe the interactions between segments of chiral blocks, which have the tendency to form a ``cholesteric'' texture. Based on the model, we calculated the bulk morphologies of chiral AB diblock copolymers using self-consistent field theory (SCFT). Experiments show that the H* phase only forms when microphase separation between PS and PLLA block happens first and crystallization of PLLA block is suppressed or happens within confined microdomain. Hence, crystalline ordering is not necessary for H* phase formation. The SCFT offers the chance to explore the range of thermodynamic stability of helical structures in the phase diagram of chiral block copolymer melts, by tuning parameters not only like the block segregation strength and composition, but also new parameters such as the ratio between preferred helical pitch to the radius of gyration and the Frank elastic constant for inter-segment distortions.

  17. Chiral effects in the confining QCD vacuum

    CERN Document Server

    Simonov, Yu A

    1994-01-01

    Configurations are introduced into the standard instanton vacuum model. This drastically improves theoretical properties of the vacuum: instanton size density $d(\\rho)$ stabilizes at $\\rho\\sim 0.2 fm$, all chiral effects are formulated in a gauge-invariant way and quarks are confined. An interesting interplay of chiral and confining dynamics is observed; for the realistic values of parameters the Georgi-Manohar picture emerges with chiral radius $R_{ch}\\sim \\rho\\sim 0.2 fm$ much less than confining radius $R_c\\sim$ hadron radius $\\sim 1 fm$. In the limit $R_{ch}\\ll R_c$ the chiral mass $M_{ch}(p)$ is unaffected by confinement and can be taken in the local limit $M_{ch}(p=0)$. Different types of effective chiral Lagrangians (ECL) are obtained, containing all or a part of gluon, quark and Nambu--Goldstone--meson fields. The ECL are manifestly gauge--invariant and in the limit of no gluon fields coincide with those found previously. The problem of the double role of the pion -- as a Goldstone meson or as a $q\\ba...

  18. Novel Lifshitz point for chiral transition in the magnetic field

    Directory of Open Access Journals (Sweden)

    Toshitaka Tatsumi

    2015-04-01

    Full Text Available Based on the generalized Ginzburg–Landau theory, chiral phase transition is discussed in the presence of magnetic field. Considering the chiral density wave we show that chiral anomaly gives rise to an inhomogeneous chiral phase for nonzero quark-number chemical potential. Novel Lifshitz point appears on the vanishing chemical potential line, which may be directly explored by the lattice QCD simulation.

  19. New Terms for Compact Form of Electroweak Chiral Lagrangian

    Institute of Scientific and Technical Information of China (English)

    YE Wei; ZHANG Hong-Hao; YANG Hong-Wei; YAN Wen-Bin; CHEN Na; J.K. Parry; LI Xue-Song

    2008-01-01

    The compact form of the electroweak chiral Lagrangian is a reformulation of its original form and is expressed in terms of chiral rotated electroweak gauge fields, which is crucial for relating the information of underlying theories to the coefficients of the low-energy effective Lagrangian. However the compact form obtained in previous works is not complete. In this letter we add several new chiral invariant terms to it and discuss the contributions of these terms to the original electroweak chiral Lagrangian.

  20. Inhomogeneous Polyakov loop induced by inhomogeneous chiral condensates

    Directory of Open Access Journals (Sweden)

    Tomoya Hayata

    2015-05-01

    Full Text Available We study the spatial inhomogeneity of the Polyakov loop induced by inhomogeneous chiral condensates. We formulate an effective model of gluons on the background fields of chiral condensates, and perform its lattice simulation. On the background of inhomogeneous chiral condensates, the Polyakov loop exhibits an in-phase spatial oscillation with the chiral condensates. We also analyze the heavy quark potential and show that the inhomogeneous Polyakov loop indicates the inhomogeneous confinement of heavy quarks.