Phase Selection of Calcium Carbonate through the Chirality of Adsorbed Amino Acids (original) (raw)
Related papers
Chiral acidic amino acids induce chiral hierarchical structure in calcium carbonate
Nature Communications
Chirality is ubiquitous in biology, including in biomineralization, where it is found in many hardened structures of invertebrate marine and terrestrial organisms (for example, spiralling gastropod shells). Here we show that chiral, hierarchically organized architectures for calcium carbonate (vaterite) can be controlled simply by adding chiral acidic amino acids (Asp and Glu). Chiral, vaterite toroidal suprastructure having a 'right-handed' (counterclockwise) spiralling morphology is induced by L-enantiomers of Asp and Glu, whereas 'left-handed' (clockwise) morphology is induced by D-enantiomers, and sequentially switching between amino-acid enantiomers causes a switch in chirality. Nanoparticle tilting after binding of chiral amino acids is proposed as a chiral growth mechanism, where a 'mother' subunit nanoparticle spawns a slightly tilted, consequential 'daughter' nanoparticle, which by amplification over various length scales creates oriented mineral platelets and chiral vaterite suprastructures. These findings suggest a molecular mechanism for how biomineralization-related enantiomers might exert hierarchical control to form extended chiral suprastructures.
Interfacial Chiral Selection by Bulk Species
Chemistry - A European Journal, 2014
In this paper we report on a chiral selection process in a self-assembled soft monolayer of an achiral amphiphile as a consequence of its interaction with chiral species dissolved in the aqueous subphase. The extent of the chiral selection is statistically measured in terms of the enantiomorphic excess of self assembled submillimeter domains endowed with well defined orientational chirality that is unambiguously resolved using optical microscopy. Our results show that the emergence of chirality is mediated by electrostatic interactions and significantly enhanced by hydrophobic effects. This chiral chemical effect can be suppressed and even reversed by opposing a macroscopic physical influence such as vortical stirring. This result evidences the crucial role of hydrodynamic effects in supramolecular aggregation.
Chiral interaction, magnitude of the effects and application to natural selection of L-enantiomer
Chemical Physics Letters, 1985
The reccn~ly inlroduced hpothcsis of chiml inwrncrion is trrawd quantitatively hy using ;1 newly defined concrpr 01 chiral eKn5sncy. Numerical estimmrs of the intsrnckn induced magnrric moment p, and the romkmnl frequency 0,. yield p, =l.O pLa and oC = 1.0 X 10" Tad/s. The cxiswnce of D molecular magnetic moment can lsad ro a nn~ur~l sclsckm of one chirality for cermin amino-acids due to coupling. wilh Ihr maanelic field of rhr earth 31 rhr wager surface. The energy differtnce helwcen _-[he Land D-enanliomers is eaimaled IO bc LE, =-lo-* kr.
Evidence for new enantiospecific interaction force in chiral biomolecules
Chem, 2021
Enantiospeci c biorecognition interactions are key to many biological events. Commonly, bio-a nity values, measured in these processes, are higher than those calculated by available methods. We report here the rst direct measurement of the interaction force between right and left handed helical polyalanine peptides using atomic force microscope (AFM) and calculations based on a simple theoretical model. A force difference of 60pN between same and opposite enantiomer interactions is measured. Additional measurements show spin dependency and fast decay of the interaction term, consistent with spin exchange interactions. This short range enantiospeci c interaction term is especially relevant in crowded biological systems. The results shed light on the importance of spin and exchange interactions in biological processes, providing explanation to the discrepancies between past calculations and experiments. Main Text Nature is based on chiral molecules, namely molecules that appear in two forms, enantiomers, that are mirror images of each other. Interestingly, chiral biomolecules, like proteins and sugars appear in Nature mainly as one enantiomer. The origin of "homo chirality" in Nature, was-and is-discussed very intensively in the literature 1. However, the focus of this work is related to a more fundamental question, i.e., why did Nature preserve chirality so persistently over the many millions years of evolution? In other words, does chirality per se, independent on the speci c handedness, provide properties that serve an important role in Life? The ability of biological molecules to interact selectively with each other is at the heart of all biological processes and the basis of many pharmaceutical concepts. Two important properties-related to chirality-characterize interactions in nature, i.e., very strong enantioselectivity
Analytical Chemistry, 1992
A total of 121 racemlc compounds were separated In the normal-phase mode on a (S)-(l-naphthylethyl)carbamoylated @cyclodextrin (S-NEC-&CD) bonded phase and 74 on the R equlvaient (R-NEC) chlrai stationary phase (CSP). All compounds are of the type that have four substituents on a stereogenic center, rather than an "axis of chirality". I t is shown that the binary solvent pair used as the mobile phase has a slgnlfhnt influence on chiral recognitlon. However, the proportions of the components of a specHic palr have little effect. From the results, the lndhrldual contrlbutions to chlral recognition by these CSPs were estimated for 81 different substituents of the stereogenk center. Varying the arrangement of these 8 1 substituents could produce over 1.6 million compounds. Hydrogen was chosen as the reference substituent and was asslgned a 0 caVmoi free energy. The chlrai recognition increased when sp2-hybridlzed carbons were connected to the stereogenic center. Conversely, sp3-hybrldired carbons decreased the enantioseiectivlty. Amldo groups increased the chiral recognitlon, especially when assoclated with ?r-acld (3,5-dlnitrobenzoyl) or ?r-basic (naphthyl) groups. This approach does not allow one to know which enantiomer elutes first. However, the "substituent energy" list for chiral compounds can be used to obtaln an estimated value for the enantloselectivity of a compound by adding the energy contributions of the four substituents connected to the stereogenk center. I n thk way one can predlct a priori whether or not a compound wlll separate on a CSP and estlmate Its separation factor (a). Theoretically, thls approach can be used for most CSPs, provlded a sufficient data base is generated on them.
Chiral self assembled monolayers as resolving auxiliaries in the crystallization of valine
Journal of Pharmaceutical Sciences, 2010
Chiral drugs are a subgroup of drug substances that contain one or more chiral centers. For reasons of safety and efficacy, the pure enantiomer is usually preferred over the racemate in many marketed dosage forms. Thus, resolution of racemic mixtures is an active area of research. In this work, chiral self assembled monolayers (SAMs) on gold were employed as resolving auxiliaries in the crystallization of the amino acid valine. Results showed the ability to obtain one enantiomer in excess on the crystals grown on the chiral SAMs when starting with racemic solutions. The enantiomer obtained in excess was the one having opposite chirality to the monolayer being used. In addition, it was possible to obtain crystals of the pure enantiomer when starting with a solution having an enantiomeric excess value of 50%. Control experiments carried out without chiral SAMs showed that at equilibrium, mixtures of the pure enantiomer and racemic compound were obtained under these conditions. The enantiomer obtained on the chiral SAMs was the one that was initially present in excess regardless of the chirality of the monolayer being used. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:3931–3940, 2010
Stereochemical studies on chiral systems in two dimensions
Journal of Physical Organic Chemistry, 2000
Structural studies on two-dimensional films of chiral amphiphiles at the air-solution interface, as investigated in situ primarily by grazing incidence x-ray diffraction (GIXD) using synchrotron radiation, yielded the crystalline packing arrangement at almost the molecular level. Results regarding three different topics are described. (1) It has proven possible to establish whether racemic mixtures of amphiphiles spread on water self-organize into 2-D crystals in which the two enantiomers either form heterochiral domains or spontaneously separate into enantiomorphous islands composed of homochiral molecules. Diastereoisomeric acid-base interactions between two different chiral amphiphiles were also used to achieve spontaneous chiral separation in two dimensions. (2) Ordered binding of solute molecules to the chiral amphiphiles could be applied in order to study their enantioselective interactions with chiral solutes present in the aqueous subphase. (3) Crystalline multilayer films of supramolecular architecture composed of water-soluble and water-insoluble chiral components may be formed at the air-solution interface and their packing arrangement determined by GIXD.