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The localized surface plasmon resonance (LSPR) phenomenon of the noble metal nanoparticles is responsible for their strongly coloured colloidal solutions. The colorimetric or colour-based detection generally relies on the aggregation of the metal nanoparticles in the presence of the analyte. In this review, the sensing of numerous classes of biological molecules such as amino acids, proteins, DNA bases, neurotransmitters and vitamins have been discussed using gold nanoparticles (GNPs) - based probes. The performance characteristics of the probes such as linearity range and limit of detection (LOD) have been presented in a tabular form. The colorimetric recognition of the chiral enantiomers of amino acids has been discussed with the help of pertinent examples. The GNPs-based colorimetric quantification and differentiation of several proteins has also been presented in the review. The mechanisms of the sensing of biological molecules in the presence of the GNPs have been discussed in detail. Hydrogen-bonding interaction and coulombic-bridging between the analyte and the GNPs were found to induce the agglomeration of the particles in most of the systems.

Driven by the clinical demand on improving the oral bioavailability and reducing the side effects of insoluble drug, aminoated mesoporous silica xerogel (named L/d-BPEIN-MSX) with chiral surface topology was constructed through a facile, economical, and biomimetic strategy within 2 min, and served as the carrier of indomethacin (IMC). In the synthetic process, L/d-tartaric acid (L/d-TA) self-assembled with branched polyethyleneimine (BPEI) to endow chirality and synergistic promoted silica deposition, while 3-aminopropyl triethoxysilane (APTES) polycondensated with the silica source to form aminoated mesostructure. By premixed strategy, IMC can be in situ loaded into L/d-BPEIN-MSX with high efficiency, which then became active in circular dichroism (CD) spectra owing to induced chirality. Noteworthy, IMC-L/d-BPEIN-MSX significantly improved the release rate of IMC with multiple controlled release manners. That is, d-BPEIN-MSX had favorable drug release behavior which could respond to the chiral stimuli, whereas l-BPEIN-MSX exhibited advantageous chiral surface topology that was beneficial for bio-processes related to oral adsorption. Undoubtedly, they increased the bioavailability of IMC to 8–9 times, displayed good anti-inflammatory effect, and reduced the gastrointestinal irritation of IMC. In addition, L/d-BPEIN-MSX had low toxicity and irritation, and was proven to be biodegradable and biocompatible, which could meet the requirement for biomedical applications.

A highly sensitive and selective electrochemical chiral sensor was developed based on the competitive supramolecular interaction of carbon nanofibers (CNFs) embedded sulfobutyl ether-β-cyclodextrin (SBE-β-CD) with optically active cationic drugs at glassy carbon electrode (GCE). The difference in intermolecular hydrogen bonding/stability constant/enantioselectivity coefficient and Gibbs free energy of anionic host SBE-β-CD with enantiomers of amlodipine (R-/S-AML), clenbuterol (R-/S-CBL) and metoprolol (R-/S-MET) as a guest paved the way for efficient discrimination. The proposed sensing platform (CNFs-SBE-β-CD/GCE) could recognize the aforementioned enantiomers based on the discernible difference of peak potential (S/R-AML (ΔEp = 135 mV), R/S-MET (ΔEp = 99 mV) and R/S-CBL (ΔEp = 111 mV). The binding mechanisms and thermodynamic study of the enantiospecific behavior have been investigated using the host-guest chemistry approach inside the nanocavity and results suggest that S-AML, R-MET, and R-CBL show stronger stability constants than their antipodes. Formation of the diastereomeric complex was taken as a measure of enantioselectivity and experimental results indicated that anionic SBE-β-CD is a better chiral ligand than neutral cyclodextrins. The fabricated sensor could be a useful low-cost electrochemical tool for molecular recognition of a variety of cationic species not only of drugs but also from other sources.

Background: Chirality is an essential property of nature. Chiral recognition is of great significance to life sciences, pharmaceutical industry, food analysis, and so on. Chiral carbon dots (CCDs), as green nanomaterials, have great prospects in chiral sensing. However, CCDs with enantioselectivity for tryptophan (Trp) enantiomers are scarce. Moreover, most chiral sensing platforms depend on the difference of fluorescence intensity at the same emission wavelength to identify enantiomers, it is still a challenge to distinguish enantiomers by the positions of fluorescent emission peaks., Results: Novel CCDs with specific chiral recognition ability for Trp enantiomers are synthesized using l-lysine and l-cysteine as precursors. The CCDs have two fluorescent emission peaks at 390 nm and 450 nm. Interestingly, the fluorescence intensity of CCDs at 390 nm enhances obviously on the addition of L-Trp, while it enhances slightly at 450 nm in the presence of D-Trp. This chiral sensing system not only can identify Trp enantiomers according to fluorescence intensity, but also achieves the distinguishment depending on emission wavelength. The enantioselectivity (I L /I D ) reaches 4.5 when the concentration of Trp enantiomer is 1 mM. This chiral sensing platform not only can be used for quantitative analysis of D-Trp and L-Trp, but also can be used for determining the enantiomeric excess of racemates. The chiral recognition mechanism is investigated by molecular simulation. It is found that L-Trp has higher binding energy with CCDs., Significance: This work presents a novel kind of CCDs with special chiral recognition performance for Trp enantiomers, and opens the door to identify chiral isomers according to wavelength difference, which has profound significance for the development of chiral sensing platforms, and may provide inspirations for the design of novel CCDs with excellent chiral recognition performance., Competing Interests: Declaration of competing interest We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The purpose of this study was to investigate the potential chiral recognition functions induced by two kinds of novel chiral microenvironment-responsive mesoporous silica nanoparticles (CMR-L-MSN and CMR-D-MSN) for the oral delivery of the poorly water-soluble achiral drug indomethacin (IMC). The as-synthesized CMR-L-MSN and CMR-D-MSN with molecular chirality and high specific surface area (SBET: 1141 and 1075 m2/g, respectively) were successfully prepared through grafting chiral molecular functional groups. The characterization results showed that CMR-L-MSN and CMR-D-MSN were spherical nanoparticles with opposite chiral features and clearly visible pore channels. Meanwhile, they exhibited good biosafety and degradability. In vitro drug release study indicated that both CMR-L-MSN and CMR-D-MSN significantly improved IMC dissolution compared with naked-MSN (N-MSN) (p

In this study, using chiral L-lysine as the molecular skeleton, three kinds of L-lysine-derived gelators (G BLB , G BLF and G FLF ) were synthesized and then bonded to the surface of silica matrix (5 μm) by amide condensation to prepare a series of multifunctional chromatography stationary phases (G BLB -SiO 2 , G BLF -SiO 2 , and G FLF -SiO 2) were prepared. The L-lysine-derived gelators not only possess chiral recognition ability, but also can spontaneously form oriented and ordered network structures in liquid medium through the interaction of non-covalent bonding forces such as hydrogen bonding, π-π stacking, and van der Waals forces. The comprehensive effect of multiple weak interaction sites enhances the molecular recognition ability and further improves the separation diversity of different types of compounds on stationary phases. The separation and evaluation of chiral compounds showed that benzoin, 1-phenyl-ethanol, 1-phenyl-propanol and 6-hydroxyflavanone could be separated in normal phase mode (NPLC). The separation of different types of non-chiral compounds, such as sulfonamides, nucleosides, nucleobases, polycyclic aromatic hydrocarbons (PAHs), anilines, and aromatic acids, were achieved in hydrophilic interaction/reversed-phase/ion-exchange mode (HILIC/RPLC/IEC), and the separation of polarized compounds could be performed under the condition of ultrapure water as the mobile phase, which has the typical retention characteristics of per aqueous liquid chromatography (PALC). The effects of organic solvent content, temperature, pH value, and buffer salt concentration on the retention and separation performance of the column were investigated. Comparison of the three prepared columns showed that the separation performance (such as aromatic selectivity) could be improved by increasing the types of functional groups on the surface of the stationary phase and the number of aromatic groups. In a word, the prepared stationary phase have multiple retention properties, can simultaneously separate chiral compounds and various types of achiral compounds. This work provides an idea for developing multifunctional liquid chromatography stationary phase materials, and further expands the application of gelators in separation science., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background: Chirality is a ubiquitous phenomenon in nature, but enantiomers exhibit different pharmacological activities and toxicological effects. Therefore, Chiral recognition plays a pivotal role in various fields such as life sciences, chemical synthesis, drug development, and materials science. The synthesis of novel chiral composites with well-defined loading capabilities and ordered structures holds significant potential for electrochemical chiral recognition applications. However, the design of selective and stable electrochemical chiral recognition materials remains a challenging task., Result: In this work, we construct a simple and rapid electrochemical sensing platform for tryptophan (Trp) enantiomer recognition using cyclodextrin-modified microporous organic network as chiral recognition agent. CD-MON with chiral microenvironment was prepared by Sonogashira-Hagihara coupling reaction of the chiral molecule heptyl-6-iodo-6-deoxyβ-cyclodextrin and 1, 4-Diethynylbenzene. The adhesion of BSA makes CD-MON firmly fixed on the electrode surface, and as a chiral protein, it can improve the chiral recognition ability through synergistic effect. Chiral amino acids are in full contact with the chiral microenvironment during pore conduction of MON, and L-Trp is more stably bound to CD-MON/BSA due to steric hindrance, host-guest recognition and hydrogen bonding. Therefore, the electrochemical sensor can effectively identify tryptophan enantiomers (I L-Trp /I D-Trp  = 2.02), and it exhibits a detection limit of 2.6 μM for L-Trp. UV-Vis spectroscopy confirmed the adsorption capacity of CD-MON towards tryptophan enantiomers in agreement with electrochemistry results., Significance: The prepared chiral sensor has excellent stability, reproducibility (RSD = 3.7%) and selectivity, realizes the quantitative detection of single isomer in tryptophan racemic and quantitative analysis in real samples with 94.0%-101.0% recovery. This work represents the first application of MON in chiral electrochemistry which expands the application scope of chiral sensors and holds great significance in separation science and electrochemical sensing., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Chiral separation of short peptides is of great interest, due to different pharmacological, pharmacokinetic, and/or toxicological activities often possessed by different stereoisomers of chiral drugs. Crown ether chiral stationary phases have been successfully used for separating enantiomers of various racemic compounds containing primary amino groups. Even though chiral recognition mechanism for crown-ethers CSPs is generally understood, on a molecular level, the exact chiral recognition mechanisms for the resolution are still unclear. Furthermore, short peptide analytes often contain multiple amino moieties capable of binding to the crown ether selector. A research of relationship between peptide chemical structure and chiral chromatographic interactions was performed, by comparing the retention profiles of µ-opioid receptor agonist tetrapeptide Tyr-Arg-Phe-Lys-NH2 and its structural analogues on two commercially available S- and R-(3,3’-diphenyl-1,1′-binaphthyl)-20-crown-6) stationary phases [CROWNPAK CR-I (+) and (-)], in order to clarify, which of the potential interaction sites are responsible for retention and chiral recognition in Tyr-Arg-Phe-Lys-NH2 tetrapeptide.

Current state-of-the-art chiral stationary phases (CSPs) enable chiral resolution of almost any racemic mixture of choice. The exceptions represent ionizable and ionized substances that fail at any attempts to resolve on commercially available CSPs. These compounds, however, can be efficiently separated on chiral ion exchangers. Commercially available Cinchona alkaloids-based chiral weak ion-exchangers are typically used for chiral resolution of organic acids, while zwitterion ion-exchangers are efficient in the resolution of acids, bases, and zwitterions. The latter possess in their structure a cation exchange unit, which alone can serve as a cornerstone of chiral strong cation exchangers facilitating chiral separation of various basic racemic mixtures. Although chiral strong cation exchangers (cSCX) are efficient CSPs, their structural variations have not been thoroughly studied so far. It was assumed that the mechanism of chiral recognition of basic compounds by cSCX is based predominantly on π-π-interactions, hydrogen bonding and steric interactions (CSP I). To verify this assumption, we aimed in our study on the design and synthesis of cSCX first lacking lateral polar substituents on the aromatic unit in the selector's structure (CSP II), and second, to replace the aromatic unit by a cyclohexane ring (CSP III and IV), thereby to omit completely the π-π-interactions. We hypothesized that this structural change should lead to a partial or complete loss of enantiorecognition power of the selectors. Surprisingly, the non-aromatic cSCXs have shown chiral recognition capability comparable to that of previously described chiral cation exchange-type CSPs: from 16 analytes screened, 11 analytes were baseline resolved and 5 partially resolved on CSP I, while non-aromatic CSP III resolved 10 analytes baseline and 6 partially. We discuss the structural motifs of the known cSCX and the novel non-aromatic selectors in a relationship with their chromatographic performance using a set of basic analytes. Moreover, we present a theory of an effective chiral recognition mechanism by two novel non-aromatic cSCXs based on the chromatographic results and quantum mechanical calculations., Competing Interests: Declaration of competing interest The authors declare the following finanial interests/personal relationships which may be considered as potential competing interests: Michal Kohout reports financial support was provided by Czech Science Foundation. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

We report a post-synthesis modification for the preparation of a novel chiral fluorescent covalent organic framework (COF) for selective recognization of imazamox enantiomers. In this study, chiral COF was firstly synthesized via a Schiff-base reaction between 2,5-dihydroxyterephthalaldehyde (Dha) and 1,3,5-tris(4-aminophenyl)benzene (Tab) followed by a nucleophilic substitution using (1S)-(+)-10-camphorsulfonyl chloride as chiral modifier. The resulting regular spherical chiral COF Dha Tab not only presented the high optical efficiency, strong covalent bond structure, good crystallinity, large specific surface area but also showed the specific enantioselectivity and quick identification for imazamox enantiomers among five pesticide enantiomers (S/R-imazamox, acephate, acetochlor, propisochlor and metalaxyl). The detection limits for S- and R-imazamox were 4.20 μmol/L and 3.03 μmol/L, respectively. Meanwhile, the enantiomeric excess value (5.30 %) manifested that the chiral COF Dha Tab had the strong adsorption ability to imazamox enantiomers and more higher affinity for R-imazamox. This chiral fluorescent COF opened up a new way for the recognition of enantiomers., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

An optically-active poly(diphenylacetylene) (PDPA) bearing carboxy pendant groups with left-handed helicity memory (M-h-poly-1), synthesized using the noncovalent helicity-induction-and-memory strategy, was converted into a PDPA bearing optically-active pendant groups through an amide bonding (M-h KT -poly-2S), while maintaining the left-handed helicity memory, by reaction with (S)-1-phenylethylamine ((S)-2) using a condensing reagent at room temperature. Its chiral recognition ability was investigated as a chiral stationary phase (CSP) for high-performance liquid chromatography (HPLC). M-h KT -poly-2S exhibited significantly different chiral recognition ability towards racemates compared to the previously reported corresponding helical PDPA bearing the same optically-active pendant groups (M-h TS -poly-2S) (prepared by the reaction of an optically-inactive PDPA bearing carboxy pendants with (S)-2, followed by thermal annealing, to induce a left-handed helical structure in the polymer main chain). Although the main chains of both M-h KT -poly-2S and M-h TS -poly-2S formed almost completely left-handed helical structures, their higher-order structures varied slightly, as confirmed by various spectroscopic methods (UV-Vis, circular dichroism (CD), IR, and vibrational CD). M-h KT-TS -poly-2S, the PDPA formed on the thermal annealing of M-h KT -poly-2S, exhibited the same higher-order structure and chiral discrimination ability as M-h TS -poly-2S. Therefore, slight differences in the higher-order structures of the kinetically-trapped metastable state (M-h KT -poly-2S) and the thermodynamically-stable state (M-h TS -poly-2S), due to differences in synthetic procedures, significantly impact their chiral recognition abilities as CSPs, even with identical primary structures and helix-sense of the polymer main chain., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Katsuhiro Maeda has patent issued to Kanazawa University., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The influence of amino acid residue on μ-opioid receptor agonist tetrapeptide Tyr-Arg-Phe-Lys-NH 2 analogue chromatographic behaviour on crown ether based chiral stationary phases has been investigated. S- and R-(3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6 chiral selectors in commercially available CROWNPAK CR-I (+) and (-) columns are both each other enantiomers, thus, under the same LC conditions, retention of Tyr-Arg-Phe-Lys-NH 2 dxxx enantiomers (fixed in d-tyrosine position) on S-chiral selector do not significantly differ from the retention times of their lxxx antipodes, obtained on R-chiral selector (and vice versa), allowing us to study the apparent separation of a specific tetrapeptide enantiomeric pair, without obtaining the actual racemate. Ten tetrapeptides (llll-isomers) have been synthesized with the aim to cover a wider range of different amino acid classes. Histidine, glutamic acid, cysteine, leucine and tryptophan were introduced at the N-terminus or Phe position of Tyr-Arg-Phe-Lys-NH 2 tetrapeptide structure. The effects of the amino acid residue with emphasis on retention, enantioseparation, as well as the influence of position of the amino acid residue in tetrapeptide sequence, are discussed., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

This work firstly developed a near-infrared fluorescence capillary imprinted sensor with high selectivity and sensitivity for the chiral recognition of l-histidine. The near-infrared fluorescence imprinted polymer prepared by sol-gel method using CdTe quantum dots as the near-infrared fluorescence source was self-sucked into activated capillary to form the fluorescence imprinted capillary. The fluorescence imprinted capillary sensor had higher fluorescence response efficiency. With the superior stability, reproducibility and reusability, the fluorescence capillary imprinted sensor displayed higher selectivity toward l-histidine. Under the optimal conditions, the fluorescence intensity (λex = 370 nm, λem = 695 nm) of the fluorescence capillary imprinted sensor was enhanced in proportion to l-histidine concentration ranged from 0.1 pM to 1.8 pM with a limit of detection of 0.08 pM. Spiking experiment showed that the fluorescence capillary imprinted sensor was successfully used for determination of l-histidine in human urine and serum with the recoveries of 99.6-102.7%. The near-infrared fluorescence capillary imprinted sensor possessed significantly potential for high sensitive detection of l-histidine, which realized trace-level analysis for micro-volume sample and provided promising utility for green chemical., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Amino acids play a very important role in the fields of pharmacy and biochemistry, and the identification of amino acid enantiomers has become a research hotspot. In this study, chiral nanomaterials ZnFe 2 O 4 -L-Cys (Cys = cysteine) were prepared by the mechanical stirring method and characterizad by different kinds of techniques. The effect of pH and Cu 2+ on the recognition of tryptophan by chiral nanomaterials ZnFe 2 O 4 -L-Cys was further explored by ultraviolet-visible spectroscopy. The experimental results show that when the pH of the recognition environment is neutral, ZnFe 2 O 4 -L-Cys can be used as chiral selectors for tryptophan enantiomers in the presence of Cu 2+ and the absorbance of L-Trp is always stronger than D-Trp within a certain concentration range, which provides a novel and convenient way for the chiral recognition of tryptophan enantiomers., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Lactide is a natural and renewable lactone cyclic ester-containing intrinsic chiral center, providing an affordable natural compound that is potential for the development of chiral polymers. In this work, we reported two novel chiral stationary phases (CSPs) based on lactide derivatives, methylene lactide (MLA), for high-performance liquid chromatography (HPLC). By using free radical polymerization, chemically bonded CSPs of poly(methylene lactide) (PMLA) and side-chain modified PMLA by aminolysis (N-PMLA) can be prepared. Also, poly(l-lactic acid) (PLLA) was prepared as a control. The chiral resolution performance of the chromatographic columns was examined in both reversed-phase and normal-phase modes. PMLA and N-PMLA CSPs exhibited fairly good chiral recognition ability, whereas the separation ability of PLLA is much weaker. This work provides a new platform for the development of high-performance CSPs from affordable natural products., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021. Published by Elsevier B.V.)

Chiral recognition is always a significant and challenging work in analytical chemistry. A fluorescent chiral recognition method based on chiral carbon quantum dots (CCQDs) towards isoleucine (Ile) enantiomers was developed in this work. CCQDs were synthesized by one-step hydrothermal method using l-cysteine as chiral source. The fluorescence intensity of CCQDs enhanced obviously in the presence of L-Ile, but had no observable change in the presence of D-Ile. The response speed of this chiral sensing system is fast, Ile enantiomers can be discriminated by CCQDs within 5 min, the enantioselectivity (I L /I D ) can reach up to 2.2. Good linearity for detecting L-Ile was obtained over the concentration range from 0 to 30 mM with a LOD of 0.29 mM. The fluorescence intensity also increased linearly with the enantiomeric percentages of L-Ile in the mixture of Ile enantiomers. Thus, the developed method not only can achieve quantitative detection of L-Ile but also can determine the enantiomeric percentage in racemates. The chiral recognition mechanism can be explained by the difference in binding energy and interaction types between D-Ile and L-Ile with CCQDs by molecular modeling. The current method was applied in detecting L-Ile in real samples of functional drinks, the detection results were in consistent with the results obtained from high performance liquid chromatography, and the recoveries of standard addition were also satisfactory, which verified the reliability of the developed method., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Penicillamine (Pen) is a common chiral drug that is obtained from penicillin. Between the two enantiomers of Pen, only D-Pen can be used to treat cystinuria and rheumatoid arthritis while L-Pen is toxic. Therefore, it requires great efforts for the research of the rigorous analysis and distinction of the two enantiomers. The non-covalent combination of chiral molecules and chiral selectors (CSs) has been proved as a unique strategy for chiral distinction by ion mobility spectrometry in coupling with -mss spectrometry (IM-MS). Here, we developed a simple method to distinguish D, L-Pen by using special CSs for IM-MS separation. The CSs utilized here include cyclodextrins (CD) and linear chain oligosaccharides plus metal ions. We found that non-covalent complexes [Pen+β-CD + Li] + could be easily formed by electrospray ionization of the mixture of the solution, and the chirality of Pen could be effectively recognized by measuring their mobilities due to the different collision cross collision sections of [D-Pen+β-CD + Li] + and [L-Pen+β-CD + Li] + . A detailed analysis of [Pen+β-CD + Li] + was then conducted by the optical rotation measurements and NMR experiments to reveal their structural differences. Furthermore, DFT calculation showed the differences of molecular conformation between the complexes. The results provide a new powerful method for fast analysis and recognition of chirality of Pen compounds by IM-MS., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021. Published by Elsevier B.V.)

As the highest form of molecular recognition, the chiral molecular recognition is the most difficult measurements. Herein, a disposable dual-signal enantioselective platform was fabricated based on stereoscopic porous chiral carbon nanotubes hydrogel modified screen printed electrode. This kind of chiral hydrogel was prepared by a simple heating method with l-cysteine and chiral single-walled carbon nanotubes of chirality (6,5), and its dispersion and morphology were characterized by several techniques including scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. The stereogenic chiral interface was successfully employed to discriminate mandelic acid enantiomers via both oxidation peak intensity and peak potential value of cyclic voltammetry. The chiral recognition mechanism was discussed specifically, which resulted from the formation of an efficient three-dimensional chiral nanospace. The inherent chirality of chiral carbon nanotubes hydrogel, together with their orderly spatial arrangement, can significantly improve the efficiency of chiral recognition compared with traditional electrochemical chiral sensors. As a novel chiral sensing interface, such chiral carbon nanotubes hydrogel was simple to prepare, fast to operate, with good sensitivity and excellent stability for the construction of efficient and practical electrochemical chiral sensors., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Chiral recognition between amino acids and monosaccharides in the gas phase was investigated as a model for chemical evolution in interstellar molecular clouds. Ultraviolet (UV) photodissociation spectra and product ion spectra of cold gas-phase hydrogen-bonded clusters of protonated tryptophan (Trp) and a pentose, including ribose and arabinose, were obtained using a tandem mass spectrometer equipped with an electrospray ionization source and a temperature-controlled ion trap. The relative intensity of the signal arising from the S 1 -S 0 transition of protonated Trp observed at approximately 285 nm in the UV photodissociation spectrum of homochiral H + (d-Trp)(d-ribose) was significantly higher than that of heterochiral H + (l-Trp)(d-ribose), corresponding to the ππ* state of the Trp indole ring. Optical properties of Trp in the clusters induced by 285-nm photoexcitation were applied to the identification and quantification of pentose enantiomers in solution. Pentose enantiomeric excess in solution was determined from relative abundances observed in a single product ion spectrum of 285-nm photoexcited hydrogen-bonded clusters of H + (l-Trp) and pentose. A mixture of two pentoses could also be quantified by this method. The geometric and electronic structures of Trp enable recognition of biological molecules through hydrogen bonding., (Copyright © 2021 Elsevier Inc. All rights reserved.)

In this work, three kinds of gold nanorods (AuNRs) with different aspect ratios were synthesized through conventional seed-mediated growth method, and the chirality of these AuNRs were characterized by circular dichroism (CD) spectroscopy. The results showed that the AuNRs with bigger aspect ratio had larger chirality. The AuNRs with different aspect ratios were applied to distinguish the enantiomers of 19 kinds of α-amino acids. It was found that AuNRs with bigger aspect ratio exhibited the stronger chiral recognition ability. As a proof-of-principle, the AuNRs with the aspect ratio of 4.8 were used to quantitatively recognize enantiomers of valine. Furthermore, the microcalorimetry was applied to study the interaction of AuNRs with amino acid enantiomers. This work provides one method to improve the chiral recognition ability of AuNRs by optimizing the aspect ratio of AuNRs, and helps people better understand the intrinsic chirality of nanostructures., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Inclusion complexes of R-ketoprofen and S-ketoprofen enantiomers with β-cyclodextrin (β-CD) in aqueous solution were studied using various spectroscopic techniques such as Raman, FTIR, UV and fluorescence. The different relative intensities and characteristic band shifts of the two enantiomers from Raman spectra suggests different interaction when complexed with β-CD. Raman experiments revealed a noticeable diminishing of the CC vibration and ring deformation, which indicate the embedding of ketoprofen inside the β-CD cavity. It's revealed that distinct differences between R- and S-ketoprofen in the presence of β-CD at neutral pH. The stoichiometry ratio and binding constant of the inclusion complexes were calculated using Benesi-Hildebrand plot. Both enantiomers showed stoichiometry ratio of 1:1 inclusion complex with β-CD. The binding constant of R-ketoprofen (4088 M -1 ) is higher than S-ketoprofen (2547 M -1 ). These values indicated that β-CD formed inclusion complexes more preferentially with R-ketoprofen than S-ketoprofen. Results demonstrated that β-CD can be used as a promising chiral selector for ketoprofen enantiomers., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The recognition and separation of polar chiral compounds are important technological challenges in separation science. Taking full advantage of the intrinsically chiral environment and multiple interactions featured by macrocycles, we designed the first example of porous methylated cyclodextrins-containing polymers (MP-CDPs) with three-dimensional (3D) chiral channels. The enantioselective recognition of (R)/(S)-1-phenylethylamine mixtures was realized with enantiomer excess (e.e.) >73% in only 3 min by using MP-CDPs as the adsorbent. The obtained MP-CDPs also serve as highly efficient liquid chromatographic stationary phases for separation of polar chiral compounds. The stationary phase can separate racemic alcohols and acids successfully. These chiral compounds can be separated within 8 min under normal-phase mode, and the resolution (R S ) range from 1.76 to 3.00. Molecular simulations suggest that chiral recognition is a cooperative interaction based on multiple effects such as host-guest interaction, H-bond and size selection. These findings will provide novel chiral stationary phases for recognition and separation of polar chiral compounds in the fields of separation science and pharmaceutical industry., Competing Interests: Declaration of Competing Interest None., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Designed more than thirty years ago in order to improve and maximize the discrimination capability of native polysaccharides, cellulose- and amylose-based selectors have shown excellent and unequalled performances for the enantioseparation of chiral compounds. The successful story of these chiral selectors relies on a multi-site high-ordered chiral platform which is held up by intramolecular hydrogen bonds (HBs), and makes the polymer able to host and discriminate enantiomers. In this environment, both achiral and stereoselective intermolecular noncovalent interactions play a pivotal role, and HBs, halogen bonds (XBs), dipole-dipole, π-π stacking, steric repulsive, and van der Waals interactions underlie adsorption process and formation of transient diastereomeric assemblies between the polymer and the enantiomer pair. In the last decades, advances in computational chemistry and spectroscopic techniques have improved knowledge of noncovalent interactions, contributing to decode their functions in chemical systems. Significantly, over time the growing interplay between experimental and theoretical approaches has contributed to unravel intermolecular forces underlying selector-selectand association and to understand recognition patterns. On this basis, this review summarizes seminal and representative studies dealing with noncovalent interactions that function in HPLC enantioseparations promoted by cellulose benzoates and phenylcarbamates of amylose and cellulose. The importance of integrating theoretical and experimental approaches to profile mechanisms and interaction patterns is highlighted by discussing focused case studies. In particular, the advantageous utilization of electrostatic potential (V) analysis and molecular dynamics (MD) simulations in this field is evidenced. A systematic compilation of all published literature has not been attempted., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier B.V.)

Poly(diphenylacetylene) having optically active anilide pendants (poly-1) were synthesized by the condensation reaction of an optically active carboxylic acid with a key precursor polymer containing amino (-NH 2 ) groups, which was prepared by the polymerization of a phthalimide-protected diphenylacetylene monomer using WCl 6 -Ph 4 Sn as a catalyst, followed by phthalimide deprotection in the resulting polymer using hydrazine monohydrate. Poly-1 formed a preferred-handed helical conformation (h-poly-1) upon thermal annealing in DMF because of chirality of the pendant group. Poly-1 and h-poly-1 showed different chiral recognition abilities from the analogous poly(diphenylacetylene)s, having the corresponding optically active amide pendants, as chiral stationary phases (CSPs) for high-performance liquid chromatography. The resolution results with the h-poly-1-based CSP were much better than those with the poly-1-based CSP owing to the preferred-handed macromolecular helicity. Among the tested racemates, the h-poly-1-based CSP exhibited superior chiral recognition ability, especially toward binaphthyl compounds and chiral metal complexes., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

We report a novel chiral interface based on polysaccharides that was integrated via an amidation reaction between the COOH of sodium alginate and the NH 2 of chitosan to form a chiral selector (SA-CS) with three dimensional N-doped graphene-CNT (NGC) as the substrate material. This interface was used for chiral discrimination of tryptophan (Trp) enantiomers via electrochemical measurements. The FT-IR, SEM, TEM and XPS characterization showed that the chiral selector and substrate materials were prepared successfully. Compared with individual SA-CS and NGC, the integrated polysaccharides/3D NGC showed higher enantioselectivity for L-Trp than D-Trp due to the smaller steric hindrance for D-Trp during the formation of three-point interactions between the two diastereoisomeric enantiomer-selector complexes, which allowed L-Trp to more easily detach from the electrode modification layer and approach the electrode surface, facilitating its approach and confirming that SA-CS had a higher constant for L-Trp when applied to real samples., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Chiral recognition of enantiomers is fundamentally important. In this work, an effective and simple chiral sensing strategy for discrimination of leucine (Leu) enantiomers was constructed. In this chiral sensing, cube-shaped gold nanoparticles (AuNCs) as colorimetric probes are used to recognize Leu enantiomers. L-Leu can induce rapidly the aggregation of AuNCs, leading to change of AuNCs solution from red to colorless, while D-Leu cannot induce the color change. This distinct color changes allow naked-eye to distinguish chiral isomers of Leu. The chiral sensing was applied to measure the enantiometric excess of L-Leu in the whole range (from -100% to 100%). This chiral analysis can be performed by naked eye or simple ultraviolet-visible spectrometer. In addition, the mechanism of chiral recognition has been studied with circular dichroism (CD) spectra, UV-vis absorption spectra and zeta potential. In this method, the chiral recognition is due to the intrinsic chirality of AuNCs, and the AuNCs don't need any chiral labeling or modification. This chiral sensing method is simple, cheap, rapid and easy to operate. Furthermore, this work provides one experimental evidence for intrinsic chirality of nanoparticles, and helps people understand the chirality of nanostructures., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Graphene oxide (GO) modified with ferrocene (Fc) was successfully assembled via the π-π interaction (GO-Fc) and had the features of large surface area and high loading. Then, a novel composite was synthesized via β-cyclodextrin (β-CD) functionalized GO-Fc by combining the advantages of GO-Fc and β-CD. An efficient chiral electrochemical sensing interface was constructed by using the rGO-Fc-CD composite as the electrode modification for the recognition of phenylalanine (Phe) enantiomers. The successful synthesis of the composites was confirmed by FTIR, XRD, TGA, SEM, and XPS results. The host-guest inclusion interaction was detected by ultraviolet spectroscopy and DPV. The recognition results demonstrated that the rGO-Fc-CD/GCE showed a higher chiral recognition capability for L-Phe than for D-Phe. The enantioselectivity coefficient (I D /I L ) of the proposed sensor was 2.47. The LOD values of 27 nM and 52 nM (S/N = 3) for L-Phenylalanine and D-Phenylalanine were obtained for this electrochemical sensor. The as-synthesized material was successfully exploited for the recognition of Phe enantiomers, indicating that the developed sensor has wide application prospects., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Construction of convenient and effective method for enantiomer identification is of vital significance for biochemistry and medical science. Herein, we design an effective sensor for chiral recognition of tryptophan (Trp) enantiomers, and self-assembly of Cu 2+ -modified β-cyclodextrin on poly-L-arginine/multi-walled carbon nanotubes (Cu-β-CD/PLA/MWCNTs) is studied. Meanwhile, Cu 2+ acts as a cap to prevent the release of the high energy water and compel Trp enantiomer into the smaller opening of β-cyclodextrin. Recognition of L-Trp is accomplished by the formation of hydrogen bonds between the amino of L-Trp and the high energy water confined in cavity of Cu-β-CD. Compared with D-Trp, the sensor exhibits favorable chiral recognition toward L-Trp with a separation coefficient of 3.37. And the chiral sensor presents admirable enantiomers determination with excellent sensitivity, providing a good linear correlation in the range of 1 × 10 -6 M~5.5 × 10 -5 M, and the detection limit can reach 3.3 × 10 -7 M (S/N = 3). Besides, the proposed sensor has been able to predict the percentage of D-Trp in the racemic mixture, suggesting its potential applications in the enantiomer recognition field., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The chiral analysis of enantiomers is important because bioactivity can depend strongly on stereochemistry as ligand-protein binding motifs are typically chiral. Ion mobility mass spectrometry-based methods are emerging for the rapid and sensitive chiral analysis of molecules. However, such methods are typically limited by the use of metal-bound trimers, which can be challenging to form owing to ion suppression and the need for extensive pre-screening experiments to identify suitable metal ions. Moreover, the chiral separation of very small molecules, such as cysteine and proline, using ion mobility has remained challenging. Here, using electrospray ionisation high-resolution differential ion mobility mass spectrometry (ESI-DMS-MS), we demonstrate that the enantiomers of benchmark amino acids as small as proline can be rapidly distinguished without the use of metal ions for the first time. ESI-DMS-MS of proton-bound diastereomeric dimer complexes, containing enantiomers of amino acids and a 'chiral selector' (N-tert-butoxycarbonyl-O-benzyl-l-serine; BBS) corresponding to [L/D-X(BBS)+H] + (X = cysteine and proline) resulted in the separation of L and D-enantiomers. By use of DMS-MS and standard solutions of chiral mixtures, these data indicate that the enantiomeric excess of proline can be accurately quantified by differential ion mobility mass spectrometry. Overall, these results provide further evidence that DMS-MS can be used for the rapid and accurate 'metal-ion free' chiral analysis of many other biologically important molecules., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Electrochemical enantiorecognition has attracted much interest due to its advantages of low cost and simple equipment. In this work, a new chiral ionic liquid is prepared and applied as an electrolyte for the one-step synthesis of functional graphene sheets (GO-(S,S)-CIL). More importantly, an electrode is modified by the material for the construction of an electrochemical sensor (GO-(S,S)-CIL-GCE). Enantiomers including L/D-tryptophan, (R)-/(S)-mandelic acid, (R)-/(S)-malic acid, and L/D-tyrosine are successfully distinguished by GO-(S,S)-CIL-GCE in the response of peak currents to different forms. In addition, the peak potential of the L form is located negatively compared to the D form for tryptophan, and the value of the peak-to-peak potential separation approaches 72 mV. The recognition mechanism is assessed by the density functional theory calculation in detail. In brief, the present method offers great promise for the preparation of functional graphene sheets and their further application in chiral recognition., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Nine cellulose derivatives bearing two different carbamate substituents at 2,3- and 6-positions of a glucose unit were synthesized by a sequential process based on the regioselective protection at 6-position. Their chiral recognition abilities were then evaluated as the chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) after coating them onto the macroporous silica gel. The introduction of two different phenylcarbamates at 2,3- and 6-positions of glucose unit was comparatively more attractive than that of one phenylcarbamate and one cyclohexylcarbamate to enhance the chiral recognition ability of these cellulose derivatives. Different combination of carbamate substituents of cellulose derivatives seems to offer superior resolution of different racemic compounds. The chiral recognition ability of these derivatives is apparently dependent on the nature, position and number of the substituents on the aromatic moieties. Many derivatives exhibit good enantioselectivity for the racemates in this study, and those based on cellulose 2,3-(3,5-dimethylphenylcarbamate) showed relatively better chiral recognition than others. Some racemates could be even more efficiently resolved on the cellulose derivatives with different carbamate groups at 2,3- and 6-positions than on the cellulose tris(3,5-dimethylphenylcarbamate), which is commercially available as one of the most popular chiral columns, Chiralcel OD. The structures of the obtained cellulose derivatives were also investigated by circular dichroism spectroscopy., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A highly ordered chiral mesoporous silica-coated capillary column has been used for high-resolution gas chromatographic separations. The column has excellent selectivity, not only for the separation of isomers, polycyclic aromatic hydrocarbons, linear alkanes, long chain alkanes, Grob's test mixture and aromatic hydrocarbons, but also for the resolution of different classes of chiral compounds. Additionally, the column exhibits high column efficiency, excellent temperature resistance, and analysis times are short. This is the first report of a highly ordered chiral inorganic mesoporous silica used in separation science., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In this study, a novel aptamer - based fluorescence bio-sensor (aptamer-AuNps) was developed for chiral recognition of arginine (Arg) enantiomers based on aptamer and gold nanoparticles (AuNps). Carboxyfluorescein (FAM) labeled aptamers (Apt) were absorbed on AuNps and their fluorescence intensity could be significantly quenched by AuNps based on fluorescence resonance energy transfer (FRET). Once d-Arg or l-Arg were added into the above solution, the aptamer specifically bind to Arg enantiomers and released from AuNps, so the fluorescence intensity of d-Arg system and l-Arg system were all enhanced. The affinity of Apt to l-Arg is tighter to d-Arg, so the enhanced fluorescence signals of l-Arg system was stronger than d-Arg system. What's more, the enhanced fluorescence were directly proportional to the concentration of d-Arg and l-Arg ranging from 0-300 nM and 0-400 nM with related coefficients of 0.9939 and 0.9952, respectively. Furthermore, the method was successfully applied to detection l-Arg in human urine samples with satisfactory results. Eventually, a simple "OR" logic gate with d-Arg &l-Arg as inputs and AuNps aggregation state as outputs was fabricated, which can help us understand the chiral recognition process deeply., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Paper-based sensors open new avenue to produce simple, rapid, inexpensive and single-use analytical devices for a wide application fields involving medical diagnosis, food analysis and environmental monitoring. In this study, a new optical sensing platform for enantioselective recognition of chiral analytes was introduced by using in-situ synthesized silver nanoparticles-embedded transparent nanopaper. To this aim, nanopaper was obtained by environment-friendly approach using bacterial cellulose made of nanofibers and silver nanoparticles were embedded within nanopaper by an in-situ generation method. The chiral recognition capability of AgNPs was operated in both solution phase and nanopaper for the tested enantiomers. AgNPs showed a discriminative sensing response toward D-cysteine with a LOD value of 4.88 µM. The principle of optical sensing is the selective interaction of the inherently chiral AgNPs with enantiomers causing to aggregation of AgNPs to display a significant colour change from yellow to purple-brown in both aqueous phase and nanopaper. As for practical use, the obtained plasmonic nanopaper was punched into circular pieces and put on wax-printed PET film to produce disposable two-dimensional cuvette which could be inserted in an ordinary spectrophotometer. The enantiomeric percentage of D-cysteine was successfully determined by the fabricated nanopaper-based cuvettes., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A new, fast and inexpensive colorimetric sensor was developed for chiral recognition of tryptophan enantiomers using chitosan-capped silver nanoparticles. The function of the sensor was based on scanometry and spectrophotometry of the colored product of a reaction solution containing a mixture of chitosan-capped silver nanoparticles, phosphate buffer and tryptophan enantiomers. The image of the colored solution was taken using the scanometer and the corresponding color values were obtained using Photoshop software which subsequently were used for optimization of the experimental parameters as the analytical signal. Two types of color values system were investigated: RGB (red, green and blue values) and CMYK (cyan, magenta, yellow and black values). The color values indicated that L-tryptophan had better interaction than D-tryptophan with chitosan-capped silver nanoparticles. A linear relationship between the analytical signal and the concentration of L-tryptophan was obtained in the concentration range of 1.3 × 10 -5 -4.6 × 10 -4 molL -1 . Detection limits, were obtained to be 2.1 × 10 -6 , 2.4 × 10 -6 and 3.8 × 10 -6 molL -1 for L-tryptophan based on R (red), G (green) and B (blue) values, respectively., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A simple, fast and green method for chiral recognition of S- and R-naproxen has been introduced. The method was based on quenching of the fluorescence intensity of bovine serum albumin-stabilized gold nanoclusters in the presence of naproxen enantiomers. The quenching intensity in the presence of S-naproxen was higher than R-naproxen when phosphate buffer solution at pH7.0 was used. The chiral recognition occurred due to steric effect between bovine serum albumin conformation and naproxen enantiomers. Two linear determination range were established as 7.4×10 -7 -9.1×10 -6 and 9.1×10 -6 -3.1×10 -5 molL -1 for both enantiomers and detection limits of 7.4×10 -8 molL -1 and 9.5×10 -8 molL -1 were obtained for S- and R-naproxen, respectively. The developed method showed good repeatability and reproducibility for the analysis of a synthetic sample. To make the procedure applicable to biological samples, the removal of heavy metals from the sample is suggested before any analytical attempt., (Copyright © 2017 Elsevier B.V. All rights reserved.)

In this study, travelling wave ion mobility mass spectrometry has been used to investigate chiral differentiation of common chiral amino acids, through separation of binuclear copper bound tetrameric ions formed with chiral selector tryptophan, proline, tyrosine, phenylalanine or histidine. Significant chiral recognition was observed for amino acids with aromatic rings or long and active side chains, with peak-to-peak resolutions up to 1.826. Tryptophan and histidine offered better enantioselectivity, compared to other chiral selectors. The results suggested that the mechanism for chiral recognition in ion mobility mass spectrometry might be significantly different from that in tandem mass spectrometry. Linear calibration curves were also established to allow determination of enantiomeric excess of the analytes by the approach. This study showed that higher assembly of chiral analyte and chiral selector might enable better chiral discrimination and ion mobility mass spectrometry could be a powerful technique for provide qualitative, quantitative and structural information of chiral analysis., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Chiral analysis is of great importance to fundamental and applied research in chemical, biological and pharmaceutical sciences. Due to the superiority of mass spectrometry (MS) over other analytical methods in terms of speed, specificity and sensitivity, chiral analysis by MS has attracted much interest in recent years. Chiral analysis by MS typically involves introduction of a chiral selector to form diastereomers with analyte enantiomers, and comparison of the behaviors of diastereomers in MS. Chiral differentiation can be achieved by comparing the relative abundances of diastereomers, the thermodynamic or kinetic constants of ion-molecule reactions of diastereomers in the gas phase, the dissociation of diastereomers in MS/MS, or the mobility of diastereomers in ion mobility mass spectrometry. In this review, chiral recognition and determination of enantiomeric excess by these chiral MS methods were summarized, and the prospects of chiral analysis by MS were discussed., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Despite of the importance of enantiomers, the fluorescence sensing of enantiomers and the interpretation of the "preferential interaction" still remain insufficiently explored. In this study, we report the recognition of tyrosine (Tyr) enantiomers by chiral N-acetyl-L-cysteine (L-NAC) capped CdSe/CdS quantum dots (QDs) under alkaline experimental condition. L-Tyr could greatly quench the fluorescence of CdSe/CdS QDs, while D-Tyr displayed no effect on the fluorescence. The one-step synthesized chiral L-NAC-CdSe/CdS QDs demonstrated high selectivity for Tyr enantiomers. In particular, the mechanism of chiral recognition has been studied by UV/vis absorption spectra and circular dichroism (CD) spectra. The changes of intensity and sign of CD spectra corroborated the attachment of L-Tyr to the surface of QDs, which may be valuable aids in obtaining a better understanding of the possible mechanism of enantioselective recognition., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A new stable and stereo-selective electrochemiluminescence (ECL) interface has been designed for specific recognition of penicillamine (Pen) enantiomers by using hemoglobin (Hb) and gold nanoparticles functionalized graphite-like carbon nitride nanosheets composite (Au-g-C 3 N 4 NHs) modified glassy carbon electrodes (Hb/Au-g-C 3 N 4 /GCE). The advantages of Hb as chiral selector and Au-g-C 3 N 4 NHs as luminophore were perfectly displayed in this novel interface. The obviously different ECL intensity was exhibited after l-Pen and d-Pen adsorbed on Hb/Au-g-C 3 N 4 /GCE, and a larger response was observed on d-Pen/Hb/Au-g-C 3 N 4 /GCE. Under the optimum conditions, the developed ECL chiral sensor showed excellent analytical property for detection of Pen enantiomers in a linear range of 1.0×10 -4 M to 5.0×10 -3 M, and the detection limits of l-Pen and d-Pen were 3.1×10 -5 M and 3.3×10 -5 M (S/N=3) respectively. This work with high selectivity, stability and reproducibility may open a new door based on ECL to discriminate Pen enantiomers., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Two small molecules showed intriguing properties of analytical multipurpose probes, whereby one chromophore gives different signal for many different DNA/RNA by application of several highly sensitive spectroscopic methods. Dyes revealed pronounced fluorescence ratiomeric differentiation between ds-AU-RNA, AT-DNA and GC-DNA in approximate order 10:8:1. Particularly interesting, dyes showed specific fluorimetric response for poly rA even at 10-fold excess of any other ss-RNA, and moreover such emission selectivity is preserved in multicomponent ss-RNA mixtures. The dyes also showed specific chiral recognition of poly rU in respect to the other ss-RNA by induced CD (ICD) pattern in visible range (400-500 nm), which was attributed to the dye-side-chain contribution to binding (confirmed by absence of any ICD band for reference compound lacking side-chain). Most intriguingly, minor difference in the side-chain attached to dye chromophore resulted in opposite sign of dye-ICD pattern, whereby differences in NMR NOESY contacts and proton chemical shifts between two dye/oligo rU complexes combined with MD simulations and CD calculations attributed observed bisignate ICD to the dimeric dye aggregate within oligo rU., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Although the halogen bond (XB) has been so far mainly studied in silico and in the solid state, its potential impact in solution is yet to be fully understood. In this study, we describe the first systematic investigation on the halogen bond in solvated environment by high-performance liquid chromatography (HPLC). Thirty three atropisomeric polyhalogenated-4,4'-bipyridines (HBipys), containing Cl, Br and I as substituents, were selected and used as potential XB donors (XBDs) on two cellulose-based chiral stationary phases (CSPs) containing potential XB acceptors (XBAs). The impact of the halogens on the enantiodiscrimination mechanism was investigated and iodine showed a pivotal role on the enantioseparation in non-polar medium. Electrostatic potentials (EPs) were computed to understand the electrostatic component of CSP-analyte interaction. Moreover, van't Hoff studies for ten HBipys were performed and the thermodynamic parameters governing the halogen-dependent enantioseparations are discussed. Finally, a molecular dynamic (MD) simulation is proposed to model halogen bond in polysaccharide-analyte complexes by inclusion of a charged extra point to represent the positive 'σ-hole' on the halogen atom. On the basis of both experimental results and theoretical data, we have profiled the halogen bond as a chemo-, regio-, site- and stereoselective interaction which can work in HPLC environment besides other known interactions based on the complementarity between selector and selectand., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Eighteen novel amylose derivatives bearing different phenylcarbamate substituents at 2,6- and 3-positions of a glucose ring were synthesized through the regioselective protection at 2- and 6-positions using a bulky trialkylsilyl chloride. Their chiral recognition abilities were then evaluated as the chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) after coating them on the surface of macroporous silica gel. The chiral recognition abilities of these CSPs intricately depended on the nature, position and number of the substituents on the phenyl moieties. The introduction of substituents at meta-position of aromatic moieties at 2- and 6-positions of glucose unit was more attractive than other positions to improve the chiral recognition ability of these amylose derivatives. Each CSP seems to possess its own characteristic resolving power, and those based on amylose 3-(3,5-dichlorophenylcarbamate) showed comparatively better chiral recognition than others. For some racemates, the amylose derivatives with different phenylcarbamate substituents at 2,6- and 3-positions exhibited higher enantioselectivity than the amylose tris(3,5-dimethylphenylcarbamate), which is commercially available as Chiralpak AD, one of the most powerful CSPs. The structures of the obtained amylose derivatives were also investigated by circular dichroism spectroscopy., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A surface imprinted material of the single enantiomer of mandelic acid with high performance was successfully prepared with a new surface imprinting technique of synchronously graft-polymerizing and molecule imprinting, and its enantiomeric recognition and resolution properties were investigated. Micro-sized silica gel particles were first modified with coupling agent γ-mercaptopropyl trimethoxysilane (MPMS), obtaining the modified particles MPMS-SiO2 on which mercapto groups were introduced. A surface initiating system of -SH/BPO was constituted with the mercapto group (-SH) on MPMS-SiO2 particles and dibenzoyl peroxide (BPO) in N,N-dimethyl formamide (DMF) solution. In DMF solution, (R)-mandelic acid molecule was used as the template and the functional monomer hydroxyethyl methylacrylate (HEMA) were combined together by right of multi-site hydrogen bonds. The free radicals produced on MPMS-SiO2 particles initiate HEMA molecules around (R)-mandelic acid molecules and the crosslinking agent N,N'-Methylenebisacrylamide (MBA) to produce graft/crosslinking-polymerization. At the same time, the template (R)-mandelic acid molecules were enveloped within the thin grafted polymer layer on the surfaces of SiO2 particles, obtaining (R)-mandelic acid surface imprinted material MIP-PHEMA/SiO2. The experimental results show that MIP-PHEMA/SiO2 particles have excellent enantiomeric recognition and resolution ability. The binding capacity of MIP-PHEMA/SiO2 particles for (R)-mandelic acid reaches up to 278 mg/g. As the resolution experiment of a racemic mixture was carried out with MIP-PHEMA/SiO2 particles as solid adsorbent, relative another enantiomer, (S)-mandelic acid, the selectivity coefficient of the imprinted particles for (R)-mandelic acid is 5.02. As a consequence, the two enantiomers were well separated, and the optical purities (ee values) of the supernatant and eluant get up to 44% (corresponding to (S)-mandelic acid excess) and 85% (corresponding to (R)-mandelic acid excess), respectively., (Copyright © 2016. Published by Elsevier B.V.)

A series of chitosan bis(methylphenylcarbamate)-(isobutyrylamide) derivatives were synthesized by carbamylating chitosan isobutyrylamide with different methylphenyl isocyanates. Then the prepared chitosan derivatives were coated onto 3-aminopropyl silica particles, resulting in a series of new chiral stationary phases (CSPs) for high-performance liquid chromatography. It was observed that the chiral recognition abilities of these coated-type CSPs depended very much on the substituents on the phenyl moieties of the chitosan derivatives, the eluent composition, as well as the structure of racemates. As a typical example, the eluent tolerance of the prepared CSP with the best enantioseparation ability was investigated in detail, and the results revealed that the CSP exhibited extraordinary solvent tolerance and could still work without significant loss in enantioseparation capability after being flushed with chloroform (100%), ethyl acetate (100%) and even THF/n-hexane (70/30, v/v), while the traditional coated-type CSPs based on the cellulose and amylose derivatives, such as cellulose tris(3,5-dimethylphenylcarbamate) (CDMPC) and amylose tris(3,5-dimethylphenylcarbamate) (ADMPC), might be dissolved or highly swollen in these eluents. Therefore, the application of the resultant CSPs could address the problem of the dissolution and high swelling of traditional coated-type CSPs in some unusual eluents, broadening the possibility of eluent choice. In addition, a comparison of the prepared CSPs with the well known CDMPC- and ADMPC- based CSPs concerning the chiral recognition ability was also made. Separation performances achieved on the as-prepared CSPs in different eluents were found to be even superior to CDMPC- and ADMPC-based CSPs for the tested chiral compounds. In summary, we could safely draw the conclusion that the CSPs derived from chitosan isobutyrylamide derivatives were capable of excellent chiral recognition ability, and meanwhile possessed satisfactory eluent tolerance in a wider range of solvents., (Copyright © 2016 Elsevier B.V. All rights reserved.)