Achiral Sm(III)-Based Metal-Organic Framework as a Luminescence Sensor for Enantiodiscrimination of Quinine and Quinidine

The effective discrimination and determination of the chiral antimalarial drugs quinine (QN) and quinidine (QD) are extremely important for human health. Herein, a 2D achiral Sm-based metal-organic framework (IMU-MOF1 = [Sm(tpba)(L)]n, where Htpba = 4-(2,2':6″,2'-terpyridin)-4'-ylbenzioc acid and H2L = 2,2'-biquinoline-4,4'-dicarboxylic acid) was successfully prepared by the solvothermal method. More importantly, IMU-MOF1 was designed as an ultrasensitive fluorescent probe for the identification of chiral enantiomer drugs. The limits of detection for QN and QD are 4.24 × 10-11 and 7.54 × 10-12 M, respectively. Furthermore, it was demonstrated that the stronger hydrogen-bonding interactions between IMU-MOF1 and quinine furnish a more efficient energy transfer to the ligands in the sensing process, resulting in a significant fluorescence enhancement of IMU-MOF1.

A Theoretical Design of Chiral Molecules through Conformational Lock towards Circularly Polarized Luminescence

Circularly polarized (CP) light has shown great potential in quantum computing, optical communications, and three-dimensional displays. It is still a challenge to produce high-efficiency and high-purity CP light. Herein, we proposed a strategy to design chiral organic small molecules for CP light generation. These kinds of chiral molecules are formed by achiral light-emitting groups and achiral alkyl chains through conformational lock, which indicates that chirality can also be introduced into achiral light-emitting groups through rational molecular design. The chirality of these molecules can be further tuned by changing the length of the alkyl chains connecting the diketopyrrolopyrrole unit. The chiroptical properties of these molecules are confirmed by calculated electronic circular dichroism and chiral emission spectra, and further confirmed in experiments. The strategy developed in this work will greatly enlarge the candidate library of chiral luminescent materials.

A biomolecule chiral interface base on BSA for electrochemical recognition of amine enantiomers

A composite chiral interface (BSA-MB-MWCNTs) was prepared from bovine serum albumin (BSA), methylene blue (MB), and multi-walled carbon nanotubes (MWCNTs) for chiral recognition of amine enantiomers (1S, 2S)-N,N'-dimethyl-1,2-cyclohexanediamine and (1R, 2R)-N,N'-dimethyl-1,2-cyclohexanediamine. The BSA-based composite was characterized by field emission scanning electron microscopy (FESEM) and ultraviolet-visible spectroscopy (UV-Vis). The electrochemical responses towards the two enantiomers were analyzed via cyclic voltammetry (CV), electrochemical AC impedance method (EIS), and differential-pulse voltammetry (DPV). The experimental results showed that the combination of MWCNTs and BSA could effectively improve the overall identification efficiency, and the peak current displayed by the S-enantiomer is larger, indicating that the prepared chiral surface has stronger interaction with the R-enantiomer. Under optimized condition, the current value of the oxidation peak of the chiral modified electrode showed a good linear relationship towards the amine concentration in the range of 5.0 × 10-3 to 5.0 × 10-5  mmol·L-1 . The proposed electrochemical chiral interface is easy to handle and provides a promising electrochemical sensing platform that can be used to identify chiral amine enantiomers.

Recent advances of the ionic chiral selectors for chiral resolution by chromatography, spectroscopy and electrochemistry

Ionic chiral selectors have been received much attention in the field of asymmetric catalysis, chiral recognition, and preparative separation. It has been shown that the addition of ionic chiral selectors can enhance the recognition efficiency dramatically due to the presence of multiple intermolecular interactions, including hydrogen bond, π-π interaction, van der Waals force, electrostatic ion-pairing interaction, and ionic-hydrogen bond. In the initial research stage of the ionic chiral selectors, most of work center on the application in chromatographic separation (capillary electrophoresis, high-performance liquid chromatography, and gas chromatography). Differently, more and more attention has been paid on the spectroscopy (nuclear magnetic resonance, fluorescence, ultraviolet and visible absorption spectrum, and circular dichroism spectrum) and electrochemistry in recent years. In this tutorial review as regards the ionic chiral selectors, we discuss in detail the structural features, properties, and their application in chromatography, spectroscopy, and electrochemistry.

Tuning Biosensor Cross-Reactivity Using Aptamer Mixtures

It is challenging to tune the response of biosensors to a set of ligands, for example, cross-reactivity to a given target family while maintaining high specificity against interferents, due to the lack of suitable bioreceptors. We present a novel approach for controlling the cross-reactivity of biosensors by employing defined mixtures of aptamers that have differing binding properties. As a demonstration, we develop assays for the specific detection of a family of illicit designer drugs, the synthetic cathinones, with customized responses to each target ligand and interferent. We first use a colorimetric dye-displacement assay to show that the binding spectra of dual-aptamer mixtures can be tuned by altering the molar ratio of these bioreceptors. Optimized assays achieve broad detection of synthetic cathinones with minimal response toward interferents and generally demonstrate better sensing performance than assays utilizing either aptamer alone. The generality of this strategy is demonstrated with a dual-aptamer electrochemical sensor. Our approach enables customization of biosensor responsiveness to an extent that has yet to be achieved through any previously reported aptamer engineering techniques such as sequence mutation or truncation. Since multiple aptamers for the designated target family can routinely be identified via high-throughput sequencing, we believe our strategy offers a generally applicable method for generating near-ideal aptamer biosensors for various analytical applications, including medical diagnostics, environmental monitoring, and drug detection.

DNA intercalative trinuclear Cu(ii) complex with new trans axial nitrato ligation as an efficient catalyst for atmospheric CO2 fixation to epoxides

A trinuclear octahedral Cu^II complex was synthesized and structurally characterized by single crystal X-ray diffraction studies and behaved as a catalyst for CO₂ fixation to epoxide and as a DNA binder.

Design and synthesis of a sulphur containing Schiff base drug: DNA binding studies and theoretical calculations

The Schiff base compound MTA ((E)-5-methyl-N'-((5-methylthiophen-2-yl)methylene)-1H-pyrazole-3-carbohydrazide) derived from 2-thiophenecarboxaldehyde and 5-methylpyrazole-3-carbohydrazide has been designed to develop new sulphur containing DNA targeted molecule. The MTA has been characterized by elemental analyses, ¹H-NMR, single crystal X-ray diffraction studies as well as by geometry optimization of using DFT/B3LYP. The interaction of MTA with Calf thymus DNA (CT-DNA) was studied by spectroscopic and calorimetric techniques. The synthesized compound was found to bind with CT-DNA through groove binding mode, and the binding constant was estimated to be (4.15 ± 0.08) × 10⁴ M^-1. The negative ΔG⁰ and positive ΔS⁰ values obtained from the calorimetric technique confirmed the spontaneity of the binding of MTA with DNA.Communicated by Ramaswamy H. Sarma.

Groove binding between ferulic acid and calf thymus DNA: spectroscopic methodology combined with chemometrics and molecular docking studies

Ferulic acid (FA), a dietary phenolic acid compound, is proved to possess numerous biological activities. Hence, this study was devoted to explore the interaction between FA and calf thymus DNA (ctDNA) by UV - vis absorption, fluorescence, circular dichroism (CD) spectroscopy combined with multivariate curve resolution-alternating least-squares (MCR - ALS) and molecular docking studies. The concentration curves and the pure spectra of compositions (FA, ctDNA and FA - ctDNA complex) were obtained by MCR - ALS approach to verify and monitor the interaction of FA with ctDNA. The groove binding mode between FA and ctDNA was confirmed by the results of melting analysis, viscosity measurements, single-stranded DNA experiments, and competitive studies. The binding constant of FA - ctDNA complex was 4.87 × 10⁴ L mol^-1 at 298 K. The values of enthalpy (ΔH°) and entropy (ΔS°) changes in the interaction were -16.24 kJ mol^-1 and 35.02 J mol^-1 K^-1, respectively, indicating that the main binding forces were hydrogen bonds and hydrophobic interactions. The result of CD spectra suggested that a decrease in right-handed helicity of ctDNA was induced by FA and the DNA conformational transition from the B-form to the A-form. The results of docking indicated that FA binding with ctDNA in the minor groove. These findings may be conducive to understand the interaction mechanism of FA with ctDNA and the pharmacological effects of FA. Communicated by Ramaswamy H. Sarma[Formula: see text].

Studies of the binding properties of the food preservative thiabendazole to DNA by computer simulations and NMR relaxation

Thiabendazole (TBZ) is a commonly used food preservative and has a wide range of anthelmintic properties. In this study, computer simulations and experiments were conducted to investigate the interaction mechanism of TBZ and herring sperm DNA (hsDNA) at the molecular level. Molecular docking showed that TBZ interacted with DNA in groove mode and bound in A-T and C-G base pair regions. Molecular dynamics (MD) was used to evaluate the stability of the TBZ–DNA complex and found that the three phases in MD and the hydrogen bonds helped maintain the combination. NMR relaxation indicated that TBZ had a certain affinity to hsDNA with a binding constant of 462.43 L mol⁻¹, and the thiazole ring was the main group bound with DNA. Results obtained from fluorescence experiments showed that the binding of TBZ and hsDNA was predominantly driven by enthalpy through a static quenching mechanism. Circular dichroism and viscosity measurements proved the groove binding mode. The FTIR results clarified the conformational changes of DNA, that the DNA helix became shorter and compact, and the DNA structure transformed from B-form to A-form.

The groove binding of thiabendazole and hsDNA was studied by computer simulation and experimental methods.

Rhodamine based turn-on chemosensor for Fe3+ in aqueous medium and interactions of its Fe3+ complex with DNA

A novel di-coordinating rhodamine-based chemosensor, HL with NO donor atoms, selectively and rapidly recognizes Fe³⁺ in the presence of all biologically relevant as well as toxic metal ions and numerous anions and also with other reactive oxygen and nitrogen species.

The construction of electrochemical chiral interfaces using hydroxypropyl chitosan

A simple chiral electrochemical sensor based on hydroxypropyl chitosan (HPCS) covalently bound to multi-walled carbon nanotubes (MWCNTs) was developed for the recognition of mandelic acid (MA) enantiomers.

Novel N-Doped Carbon Dots/β-Cyclodextrin Nanocomposites for Enantioselective Recognition of Tryptophan Enantiomers

Based on N-doped carbon dots/β-cyclodextrin nanocomposites modified glassy carbon electrodes (N-CDs/β-CD/GCE), an effective electrochemical sensor for enantioselective recognition of tryptophan (Trp) enantiomers was developed by differential pulse voltammograms (DPVs). Fluorescent N-CDs were synthesized through a hydrothermal method and characterized by spectroscopic approaches. The N-CDs/β-CD nanocomposites were efficiently electrodeposited on the surface of GCE through C-N bond formation between N-CDs and electrode. The obtained N-CDs/β-CD/GCE was characterized by multispectroscopic and electrochemical methods. Such N-CDs/β-CD/GCE generated a significantly lower Ip and more negative Ep in the presence of l-Trp in DPVs, which was used for the enantioselective recognition of Trp enantiomers. The N-CDs/β-CD nanocomposites showed different binding constants for tryptophan enantiomers, and they further selectively bonded with l-Trp to form inclusion complexes. This N-CDs/β-CD/GCE combined advantages of N-CDs with strong C-N binding ability and β-CD with specific recognition of Trp enantiomers to fabricate a novel sensing platform for enantioselective recognition of Trp enantiomers. This strategy provided the possibility of using a nanostructured sensor to discriminate the chiral molecules in bio-electroanalytical applications.

Research progress in electroanalytical techniques for determination of antimalarial drugs in pharmaceutical and biological samples

The review focusses on the role of electroanalytical methods for determination of antimalarial drugs in biological matrices and pharmaceutical formulations with a critical analysis of published voltammetric and potentiometric methods.

Characterization of the interaction between resmethrin and calf thymus DNA in vitro

Resmethrin preferentially binds to the G–C rich region of the ctDNA groove, and the UV-vis spectral matrix is decomposed by MCR-ALS.

The application of l-tryptophan functionalized graphene-supported platinum nanoparticles for chiral recognition of DOPA enantiomers

A carbon-based nanocomposite surface was prepared to develop a simple strategy for electrochemical chiral analysis.