Homochirality in Life: Two Equal Runners, One Tripped

Green, Mark M.; Jain, Vipul

doi:10.1007/s11084-009-9180-7

Cited by 44 publications

(41 citation statements)

References 58 publications

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“…The simplicity of our system, an aqueous solution of lowmolecular weight nonchiral organic molecules, in which the collective chiral symmetry breaking is observed, makes the finding relevant not only to liquid crystals, but also within a broader context of homochirality in biology and materials sciences (61)(62)(63)(64). The mechanism is also particularly simple.…”

Section: Resultsmentioning

confidence: 92%

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

Tortora

Lavrentovich

2011

Proc. Natl. Acad. Sci. U.S.A.

167

171

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In many colloidal systems, an orientationally ordered nematic (N) phase emerges from the isotropic (I) melt in the form of spindle-like birefringent tactoids. In cases studied so far, the tactoids always reveal a mirror-symmetric nonchiral structure, sometimes even when the building units are chiral. We report on chiral symmetry breaking in the nematic tactoids formed in molecularly nonchiral polymer-crowded aqueous solutions of low-molecular weight disodium cromoglycate. The parity is broken by twisted packing of self-assembled molecular aggregates within the tactoids as manifested by the observed optical activity. Fluorescent confocal microscopy reveals that the chiral N tactoids are located at the boundaries of cells. We explain the chirality induction as a replacement of energetically costly splay packing of the aggregates within the curved bipolar tactoidal shape with twisted packing. The effect represents a simple pathway of macroscopic chirality induction in an organic system with no molecular chirality, as the only requirements are orientational order and curved shape of confinement.parity breaking | twisted tactoids | geometrical anchoring | nematic-isotropic coexistence I n 1949, Onsager demonstrated theoretically that a dispersion of long rigid rods develops an organized state, a so-called nematic (N) with rods being parallel to each, once their concentration exceeds some critical value (1). This remarkable collective behavior with an establishment of nonpolar axis of alignmentn ¼ −n, called the director, stems from the molecular symmetry alone, as the only requirement of the Onsager model is that the rods do not overlap. The theory was inspired by Bernal and Fankuchen's experiments (2) on aqueous suspensions of tobacco mosaic viruses (TMV) that phase separated into an isotropic (I) phase with a relatively low concentration of TMV rods and an N phase with a high concentration of TMV. The N domains emerged as spindle-like "tactoids" (3, 4) with the axes of rods following the meridians of the spindles. Besides TMV dispersions (2, 5), the N tactoids have been experimentally documented in water dispersions of many other materials, such as vanadium pentoxide (3, 4, 6, 7), bohemite rods (8), fd viruses (9, 10), f-actin (11), carbon nanotubes (12), as well as in lyotropic chromonic liquid crystals (LCLCs) (13,14).Reversible chromonic assembly and ensuing LCLC mesomorphism is displayed broadly by dyes, drugs (15-18), nucleotides (19,20), and DNA oligomers (21,22). Typically, the LCLC molecule is plank-like with aromatic cores and peripheral polar groups. In water, the polyaromatic cores stack face-to-face, forming elongated charged aggregates. The aggregates, self-assembled through weak noncovalent interactions, are polydisperse, with the length distribution that depends on concentration, temperature, ionic strength, and presence of crowding agents. At low concentrations, the aggregates are short and orient randomly. As the volume fraction increases, the aggregates elongate, multiply, and eventually some frac...

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Section: Resultsmentioning

confidence: 92%

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

Tortora

Lavrentovich

2011

Proc. Natl. Acad. Sci. U.S.A.

167

171

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“…[29] Finally,t he long-range chirality synchronization in SmQ,a s well as in Iso [*] liquid and the triple network cubic phase,a ll occurring in achiral compounds,may also provide new insight into how homochirality could have propagated at the beginning of life on Earth. [30]…”

Section: Angewandte Chemiementioning

confidence: 99%

“…CPL emitters,s ensors,a nd manipulators are also essential in optical communication, [27] quantum-based optical computing, [28] and as efficient LC display backlights. [30] [30] …”

mentioning

confidence: 99%

The Solution of the Puzzle of Smectic‐Q: The Phase Structure and the Origin of Spontaneous Chirality

Zeng

Ungar

et al. 2018

Angew Chem Int Ed

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The so-called smectic-Q (SmQ) liquid crystal phase was discovered in 1983 in rod-like molecules, but its structure remain unclear in spite of numerous attempts to solve it. Herein, we report what we believe to be the solution: A unique bicontinuous phase that is non-cubic and is made up of orthogonal twisted columns with planar 4-way junctions. While SmQ had only been observed in chiral compounds, we show that this chiral phase forms also in achiral materials through spontaneous symmetry breaking. The results strongly support the idea of a helical substructure of bicontinuous phases and long-range homochirality being sustained by helicity-matching at network junctions. The model also explains the triangular shape of double-gyroid domains growing within a SmQ environment. SmQ-forming materials hold potential for applications such as circularly polarized light emitters that require no alignment or asymmetric synthesis.

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“…mirror symmetry | parity symmetry | topological defects | chiral defects T he emergence of chirality from achiral systems poses fundamental questions about which we have limited mechanistic understanding (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11). When the chiral symmetry of an achiral system is broken, a handedness is established, and materials with different handedness commonly exhibit distinct and useful properties (10)(11)(12)(13)(14) relevant for applications ranging from chemical sensors (15,16) to photonics (17)(18)(19).…”

mentioning

confidence: 99%

Chiral structures from achiral liquid crystals in cylindrical capillaries

Jeong

Kang

Davidson

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

109

103

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We study chiral symmetry-broken configurations of nematic liquid crystals (LCs) confined to cylindrical capillaries with homeotropic anchoring on the cylinder walls (i.e., perpendicular surface alignment). Interestingly, achiral nematic LCs with comparatively small twist elastic moduli relieve bend and splay deformations by introducing twist deformations. In the resulting twisted and escaped radial (TER) configuration, LC directors are parallel to the cylindrical axis near the center, but to attain radial orientation near the capillary wall, they escape along the radius through bend and twist distortions. Chiral symmetry-breaking experiments in polymercoated capillaries are carried out using Sunset Yellow FCF, a lyotropic chromonic LC with a small twist elastic constant. Its director configurations are investigated by polarized optical microscopy and explained theoretically with numerical calculations. A rich phenomenology of defects also arises from the degenerate bend/twist deformations of the TER configuration, including a nonsingular domain wall separating domains of opposite twist handedness but the same escape direction and singular point defects (hedgehogs) separating domains of opposite escape direction. We show the energetic preference for singular defects separating domains of opposite twist handedness compared with those of the same handedness, and we report remarkable chiral configurations with a double helix of disclination lines along the cylindrical axis. These findings show archetypally how simple boundary conditions and elastic anisotropy of confined materials lead to multiple symmetry breaking and how these broken symmetries combine to create a variety of defects.mirror symmetry | parity symmetry | topological defects | chiral defects T he emergence of chirality from achiral systems poses fundamental questions about which we have limited mechanistic understanding (1-11). When the chiral symmetry of an achiral system is broken, a handedness is established, and materials with different handedness commonly exhibit distinct and useful properties (10-14) relevant for applications ranging from chemical sensors (15, 16) to photonics (17-19). To date, considerable effort has been expended to control handedness in materials (for example, by chiral separation of racemic mixtures or chiral amplification of small enantiomeric imbalances) (1,8,(20)(21)(22). Recently and in a different vein, identification and elucidation of pathways by which achiral building blocks spontaneously organize to create chiral structures have become an area of active study. Examples of these pathways include packing with multiple competing length scales (8-10, 23, 24), reconfiguration through mechanical instabilities of periodic structures (20,25,26), and helix formation of flexible cylinders through inter-and intracylinder interactions (27,28). In addition, the system of a broken chiral symmetry often consists of domains of opposite handedness with defects separating the domains.Liquid crystals (LCs) are soft materials composed ...

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Homochirality in Life: Two Equal Runners, One Tripped

Cited by 44 publications

References 58 publications

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

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

The Solution of the Puzzle of Smectic‐Q: The Phase Structure and the Origin of Spontaneous Chirality

Chiral structures from achiral liquid crystals in cylindrical capillaries

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