Enantioselective Recognition Of Amino Acids Research Articles

Engineering copper plasmonic chirality via ligand-induced dissolution for enantioselective recognition of amino acids.

The formation of chiral nanosystems and their subsequent enantioselective interaction with chiral amino acids are vital steps in many biological processes. Due to their potential to mimic biological systems, the synthesis of chiral nanomaterials has garnered significant attention over the years. Despite the emergence of diverse nanomaterials showcasing strong chiral responses, the in-depth understanding of the mechanism of plasmonic chirality in copper nanoparticles and their subsequent application in various fields are least explored. Herein, we demonstrate a facile approach for the synthesis of chiral copper nanoparticles using cysteine as a chiral precursor and capping ligand. Ligand-mediated chiral induction, established through experimental findings and a theoretical model, is ascribed as the major contributor to the origin of plasmonic chirality. The enantioselective recognition of chiral copper nanoparticles towards histidine, an amino acid with vast biological functions, was meticulously investigated by leveraging the strong copper-histidine binding ability. Ligand-induced dissolution, a unique phenomenon in nanoparticle reactions, was identified as the underlying mechanism for the nanoparticle-to-complex conversion. Understanding the mechanism of chiral induction in copper nanoparticles coupled with their enantioselective recognition of biomolecules not only holds promise in biomedical research but also sheds light on their potential as catalysts for asymmetric synthesis.

Chiral zinc oxide functionalized quartz crystal microbalance sensor for enantioselective recognition of amino acids

Chiral transition metal oxides with tunable structures and multiple physicochemical features have been increasingly applied for chiral sensing and detection. In this work, chiral zinc oxide (ZnO) was first applied as selector to construct quartz crystal microbalance (QCM) sensor for enantioselective recognition of amino acids. The chiral ZnO was prepared by a methionine-induced self-assembly strategy and its high topological chirality was confirmed by several techniques such as circular dichroism spectrum. The chiral discrimination factors were calculated by frequency shifts in response to aspartic acid, phenylalanine, lysine and arginine on L-ZnO surface, achieving 1.89 ± 0.04, 1.76 ± 0.11, 1.66 ± 0.07 and 1.54 ± 0.09, respectively. Notably, L-enantiomers preferred stronger absorptions on L-ZnO surface as compared to D-forms. It was further found that this sensor was appropriate for quantitative analysis and enantiomer excess analysis and adsorption kinetics study. Furthermore, molecular docking revealed the recognition mechanism, where chiral distinction was caused by the different steric interactions between enantiomers and chiral ZnO. This method enjoyed merits of high enantioselectivity, simple preparation and low cost, offering newly chiral sensing method for other molecules.

Chiral copper(i)–organic frameworks for dye degradation and the enantioselective recognition of amino acids

Four novel chiral CMOFs with a 2D layered hexagonal network have been prepared and used for dye adsorption and degradation. Furthermore, one exhibits different adsorption rates and efficiencies for chiral amino acids.

A near-IR Fluorescent Probe for Enantioselective Recognition of Amino Acids in Aqueous Solution.

A novel BINOL-based near-IR fluorescent probe was designed and synthesized by incorporating a rhodamine-like dye. In the presence of Zn(II), this compound was found to exhibit highly enantioselective fluorescence enhancement at λemi > 730 nm and λexc = 690 nm when treated with 14 common amino acids in aqueous solution. An enantioselective fluorescence enhancement ratio up to 163 was observed. The mechanism of the fluorescence response of this probe was investigated by various spectroscopic methods.

Amphiphilic Polymer-Based Fluorescent Probe for Enantioselective Recognition of Amino Acids in Immiscible Water and Organic Phases.

Atom transfer radical polymerization (ATRP) of N-isopropylacrylamide was conducted in the presence of a 3,3'-diformyl-1,1'-BINOL-based diinitiator (BINOL=1,1'-bi-2-naphthol) to give polymer (S)-7, which was soluble in both water and common organic solvents. Polymer (S)-7 in combination with Zn2+ in aqueous solution (BICINE buffer at pH 8.80) showed highly enantioselective fluorescence enhancement in the presence of a number of amino acids. It was found that chloroform can be used to extract the aqueous polymer-Zn2+ -amino acid solution and the resulting chloroform extract maintained the highly enantioselective fluorescence response. Thus, the enantiomeric composition of a chiral amino acid can be determined in the two immiscible solvents of water and chloroform. The aqueous polymer-Zn2+ -amino acid solution showed a lower critical solution temperature (LCST) at 34 °C, above which the polymer-Zn2+ -amino acid adduct precipitated out. Measuring the fluorescence of the precipitate redissolved in the aqueous buffer solution showed the retention of the high enantioselectivity. Both the chloroform extraction and the thermo-induced precipitation have allowed the fluorescence response of the sensor toward amino acids to be measured away from the original substrate solution. These two strategies should minimize the interference by other reaction components on the fluorescence measurement when the sensor is applied to analyze the asymmetric reaction screening experiments.

Enantioselective Recognition of Amino Acids by Enantiomerically Pure Calix[4]arene Carboxylic Acid or Their Diastereomerically Pure N-(1-Phenyl)­ethyl Amides

The interaction of inherently chiral calix[4]arene carboxilic acids and their amides with amino acids in the organic phase has been studied using electron spectroscopy. It was found that the chiral calix[4]arenes are able of enantioselective recognition of L- and D-forms of amino acids. Stability constants of the calixarene – amino acid supramolecular complexes were determined and mechanism of the host-guest interaction was examined by molecular modeling method.

Enantioselective recognition by a highly ordered porphyrin-assembly on a chiral molecular gel

Enantioselective recognition of amino acids was achieved by using a highly ordered chiral assembly of achiral porphyrin on a chiral molecular gel. Exceptionally high enantioselectivity was observed for histidine derivatives by monitoring the CD patterns and fluorescence quenching, K(SV) (l): 26.3 × 10(3) M(-1); K(SV)(D)-enantiomer: 7.03 × 10(3) M(-1).

Enantioselective recognition of amino acids based on molecularly imprinted polyaniline electrode column

A novel molecularly imprinted polyaniline (PAn) electrode column is introduced as a new technique for the enantioselective recognition of amino acids. The principle of the molecularly imprinted electrode column is based on the reversible doping/de-doping property of PAn. PAn is an organic semiconductor and thus from an electrochemical point of view the column packed with PAn can be regarded as a packed-bed electrode of a three-electrode arrangement. The electric potential of this column can be easily controlled by a potentiostat. Various important factors influencing the performance of the molecularly imprinted PAn column have been investigated using fluorescence spectrometry in conjugation with the electrochemical quartz crystal microbalance (EQCM) technique. The advantage of this method proposed over previously reported is that the enantio-recognition can be performed in a high efficiency without requiring an expensive chiral column. Especially, the ejection and re-binding of amino acids can be accomplished by adjusting the potential applied on the column packed with molecularly imprinted PAn.

Enantioselective recognition of amino acids by chiral peptido-calix[4]arenes and thiacalix[4]arenes

In order to prepare new molecular hosts able to discriminate enantiomers of amino-acid derivatives, we have synthesized chiral thiacalix[4]arenes. Extensive studies using NMR and mass spectrometry techniques allow us to determine the major supramolecular interactions involved in the recognition process. Moreover, a titration study enables us to determine the binding constant between these new hosts and a series of amino-acid derivatives. Finally, we have also demonstrated that these calixarenes are able to discriminate enantiomers of amino-acid guests.

Electrosynthesized molecularly imprinted polypyrrole films for enantioselective recognition of l-aspartic acid

The electrosynthesis, overoxidation and characterization of l-aspartic acid ( l-Asp) imprinted polypyrrole (PPy) films have been performed by using electrochemical quartz crystal microbalance (EQCM). Following the determination of the optimal electrosynthesis parameters for the formation of a smooth and uniform PPy/ l-Asp films, the overoxidized polypyrrole (oPPy) matrix templated with either l- or d-aspartic acid ( l-, d-Asp) was evaluated as a potential enantioselective recognition element. Under potentiodynamic conditions and in strongly acidic media a significantly higher sensitivity of the l-Asp acid imprinted overoxidized polypyrrole film (oPPy/ l-Asp) for l-Asp than d-Asp was observed. The results suggest the feasibility of preparing molecularly imprinted films by electropolymerization for the enantioselective recognition of amino acids and the suitability of EQCM for both monitoring the selective recognition as well as to electrochemically modulate the binding process.

Chiral Melamine Derivatives: Design, Synthesis, and Application to Mass Spectrometry-Based Chiral Analysis

A novel class of chiral melamine derivatives has been designed and synthesized. The ability of these compounds to perform chiral recognition toward 19 natural chiral alpha-amino acids has been investigated by electrospray ionization tandem mass spectrometry for the first time. The enantioselectivities of these new chiral selectors are encouraging. To elucidate some mechanism and regularity in the chiral recognition process using chiral melamine derivatives as chiral selectors, the effect of different noncovalent interactions caused by various chiral or achiral moieties in melamine derivatives on the chiral recognition in the gas phase has been studied at the same time. The result shows that electrostatic, hydrogen bond, pi-pi stacking, and steric interaction between selector and analyte play important roles in the association and enantioselective recognition of amino acids with the chiral melamine derivatives as chiral selectors. Enantiodiscrimination for analytes with different structures and properties could be improved by modifying substituents in melamine derivatives on purpose.

Amino acid recognition of pyridine bis(oxazoline)–copper(II) complex in aqueous solvent

Enantioselective recognition of amino acids has been studied with C 2-symmetric chiral pyridine bis(oxazoline)–copper(II) complexes at physiological pH condition. UV–visible titration revealed strong binding of submillimolar dissociation constant between pyridine bis(oxazoline)–copper(II) complex and amino acids in aqueous solution. Moderate selectivity of up to 2:1 between d- and l-amino acids was achieved. The enantiomers were baseline resolved by capillary electrophoresis, using the bis( l-lysine)–copper(II) complex as a chiral selector.

Enantioselective recognition of amino acids by β-cyclodextrin 6-O-monophosphates 1

Mono-(6-O-diphenoxyphosphoryl)-β-cyclodextrin 1 and mono-(6-O-ethoxyhydroxyphosphoryl)-β-cyclodextrin 2 have been synthesized by a convenient method in 40 and 35% yields, respectively. The stability constant (Ks) and Gibbs free energy change (-ΔG°) for the 1:1 inclusion complexation of the two β-cyclodextrin 6-O-monophosphates with some selected L/D-amino acids have been examined by means of differential UV spectrometry in buffered aqueous solution (pH = 7.20) at 25 °C. The results obtained indicate that the modified β-cyclodextrin compound 1 is favourable for complexation with D-amino acids except for alanine, giving fairly good enantioselectivity of up to 3.6 for D/L-serine, with a molecular selectivity of up to 12.9 for D-leucine/D-alanine. The molecular recognition ability and enantioselectivity for amino acids of the modified β-cyclodextrins 1 and 2 are discussed from the viewpoints of the size/shape-fit relationship and the multipoint recognition mechanism. The binding constant (Ks) and Gibbs free energy change (-ΔG°) for the modified β-cyclodextrins (host) inclusion complexation with L/D-amino acids (guest) may more explicitly be understood in terms of the induced-fit interaction and the complementary geometrical relationship between the host and the guest.

Enantioselective Recognition of Amino Acids by Axially-Chiral pi-Electron-Deficient Receptors.

Enantioselective Recognition of Amino Acids by Axially-Chiral pi-Electron-Deficient Receptors.

ChemInform Abstract: Chiral Diaminodiamide Copper(II) Complexes for the Enantioselective Recognition of Amino Acids: Synthesis of the Ligands and Formation Constants.

AbstractThe bis(aminoacyl)alkanediamines (III) are prepared from the compounds (I) and (II).

Chiral Diaminodiamide Copper(II) Complexes for the Enantioselective Recognition of Amino Acids: Synthesis of the Ligands and Formation Constants

Abstract(S,S)‐N,N′ ‐Bis(aminoacyl)ethane‐ and (S,S)‐N,N′ ‐bis(aminoacyl)propanediamines (AA‐NN‐2 and AA‐NN‐3, respectively, AA = alanine, phenylalanine, valine) were synthesized as the dihydrochlorides, and their complexes with Cu(II) studied potentiometrically. Since these ligands in the presence of Cu(II) are able to perform chiral resolution of D,L‐dansylamino acids in HPLC (reversed phase), in a certain pH range (6.5–8.5), it is important to know the equilibria existing between ligands and copper in aqueous solution. For AA‐NN‐2, four species, CuLH3+, CuL2+, Cu2L2H, and CuLH−2, were detected, whereas for AA‐NN‐3, only CuLH3+, CuL2+, and CuLH−2 were found. The aim is to find out which complexes may be involved in the recognition process.