Molecular Recognition Effect Research Articles

Molecularly imprinted polymer gel with superior recognition and adsorption capacity for amphenicol antibiotics in food matrices

A molecular-imprinted polymer (MIP) gel with high effective recognition of amphenicol antibiotics was synthesized for the first time based on layered double hydroxide (LDH) as the support and initiator, and functionalized β-cyclodextrin (β-CD) as the functional monomer. The synergistic effect of molecular imprinting recognition and β-CD host-guest affinity enabled MIP gel to exhibit excellent selectivity (imprinted factors: 3.9–9.4) and high adsorption capacity (28.9–75.4 mg g−1) for amphenicol antibiotics. Different adsorption isotherms and kinetics models were followed, suggesting heterogeneous single-layer recognition and chemical adsorption. After 5 cycles of adsorption and desorption, the adsorption capacity of MIP gel retained above 83.6 %, demonstrating favorable reproducibility and stability. Under optimal conditions, the method validation showed a satisfactory limit of detection (5–10 μg L−1), good correlation (r2 > 0.9967), and respectable recovery (82.6–105.3 %). The MIP gel was applied to extract amphenicol antibiotics from food matrices, achieving recoveries in the range of 78.3–104.5 %. Importantly, the recognition mechanism was studied in detail using density functional theory. Therefore, the established method demonstrates high sensitivity and can be applied as a new tactic for detecting amphenicol antibiotics in food matrices.

Green Method to Prepare Pure δ‐FAPbI3 Crystals for Fabrication of Highly Efficient Perovskite Solar Cells

The production of pure formamidinium lead iodide (FAPbI3) is crucial to ensure high‐efficiency perovskite solar cells and such pure FAPbI3 is obtainable from crystallization process because impurities from the reagents are removable by molecular recognition effect. In addition, it is important to develop a green crystallization process for the production of FAPbI3 single crystals. Via broad screening of chemicals, here, triethylphosphate and acetonitrile are selected as nontoxic solvent and antisolvent, respectively, for the liquid–liquid reaction of FAI and PbI2 and the antisolvent crystallization. The new green crystallization process produces pure δ‐FAPbI3 single crystals, which are applicable to fabricate α‐FAPbI3 perovskite solar cells. Due to the reduced trap states in the δ‐FAPbI3 single crystals, the corresponding α‐FAPbI3 perovskite solar cells have 22.61% efficiency (average = 20.65 ± 0.86% across 50 devices) and show good operational stability under continuous 1 sun illumination at 50 °C for 1000 h.

Molecular recognition effect enabled by novel crown ether as macrocyclic host towards highly reversible Zn anode

Aqueous Zn2+ ion batteries present notable advantages, including high abundance, low toxicity, and intrinsic nonflammability. However, they exhibit severe irreversibility due to uncontrolled dendrite growth and corrosion reactions, which limit their practical applications. Inspired by their distinct molecular recognition characteristics, supramolecular crown ethers featuring interior cavity sizes identical to the diameter of Zn2+ ions were screened as macrocyclic hosts to optimize the Zn2+ coordination environment, facilitating the suppression of the reactivity of H2O molecules and inducing the in-situ formation of organic–inorganic hybrid dual-protective interphase. The in-situ assembled interphase confers the system with an “ion-sieving” effect to repel H2O molecules and facilitate rapid Zn2+ transport, enabling the suppression of side reactions and uniform deposition of Zn2+ ions. Consequently, we were able to achieve dendrite-free Zn2+ plating/stripping at 98.4% Coulombic efficiency for approximately 300 cycles in Zn||Cu cell, steady charge–discharge for 1360 h in Zn||Zn symmetric cell, and improved cyclability of 70% retention for 200 cycles in Zn||LMO full cell, outlining a promising strategy to challenge lithium-ion batteries in low-cost, and large-scale applications.

Comprehensive analysis (aerobic/anaerobic, molecular recognitions, band-position and degradation-mechanism) of undoped and Co-doped anatase-brookite - An experimental/theoretical evaluation of the less-studied TiO2 mixed phase

The molecular recognition (MRec) effect is required in the initial phase of organic reactions. The second stage involves molecular-orientations and molecular-orbitals energy-levels (MOrbE). The components of a reaction must be compatible in terms MRec and MOrbE. Therefore, the comprehension of photocatalytic systems applied in wastewater treatment will be improved if the MRec effect is also considered as an important factor. The purpose of this study is to provide a comprehensive understanding of the less studied anatase-brookite mixed-phase (doped and undoped). Anatase/brookite photocatalytic systems were evaluated utilizing experimental/theoretical approaches in H2O (aerobic/anaerobic) environments with Vis-light and the organic pollutant (OrPo) methyl orange (MO). The compatibility of MRec and MOrbE of anatase-brookite mixed-phase (with the different reactive system components) confirmed this is the optimal combination for photocatalytic application. Using the sol-gel method, AM-TiO2NP (amorphous), TiO2NP (crystalline), and TiO2NP-Co0.1 at% (crystalline Co-doped) anatase-brookite mixed-phase photocatalysts were obtained. The morphology and surface were characterized using XRD, BET, SEM, HR-TEM, FT-IR and XPS. Employing UV–vis DRS and PL, photo-response and electron-hole recombination were studied. LVS and Mott-Schottky plot were employed to determine photo-electrochemical activity. The results of TiO2NP photocatalytic degradation in both aerobic and anaerobic environments are remarkable. The results of molecular dynamics (MD) simulation and Fukui Function (FF) based on density functional theory (DFT) validate the remarkable photocatalytic MO degradation.

NMR spectroscopy to study cyclodextrin-based host-guest assemblies with polynuclear clusters.

Natural cyclodextrin (CD) macrocycles are known to form diverse inclusion complexes with a wide variety of organic molecules, but recent work has revealed that inorganic clusters also form multicomponent supramolecular complexes and edifices. Such molecular assemblies exhibit a high degree of organization in solution governed by various chemical processes including molecular recognition, host-guest attraction, hydrophobic repulsion, or chaotropic effect. Nuclear magnetic resonance (NMR) spectroscopy is one of the most efficient and practical analytical techniques to characterize the nature, the strength and the mechanism of these interactions in solution. This review provides a brief overview on recent examples of the contribution of NMR to the characterization of hybrid systems in solution based on CD with polynuclear clusters, including polyoxometalates (POMs), metallic clusters and hydroborate clusters. The focus will be first on using 1H (and 13C) NMR of the host, i.e., CD, to identify the nature of the interactions and measure their strength. Then, 2D NMR methods will be illustrated by DOSY as a means of highlighting the clustering phenomena, and by NOESY/ROESY to evidence the spatial proximity and contact within the supramolecular assemblies. Finally, other NMR nuclei will be selected to probe the inorganic part as a guest molecule. Attention will be paid to classical host-guest complexes Cluster@CD, but also to hierarchical multi-scale, multi-component assemblies such as Cluster@CD@Cluster.

Artificial sodium-selective ionic device based on crown-ether crystals with subnanometer pores

Biological sodium channels ferry sodium ions across the lipid membrane while rejecting potassium ions and other metal ions. Realizing such ion selectivity in an artificial solid-state ionic device will enable new separation technologies but remains highly challenging. In this work, we report an artificial sodium-selective ionic device, built on synthesized porous crown-ether crystals which consist of densely packed 0.26-nm-wide pores. The Na+ selectivity of the artificial sodium-selective ionic device reached 15 against K + , which is comparable to the biological counterpart, 523 against Ca2 + , which is nearly two orders of magnitude higher than the biological one, and 1128 against Mg2 + . The selectivity may arise from the size effect and molecular recognition effect. This work may contribute to the understanding of the structure-performance relationship of ion selective nanopores.

Frontispiece: Majority‐Rules Effect and Allostery in Molecular Recognition of Calix[4]arene‐Based Triple‐Stranded Metallohelicates

Triple-stranded metallohelicates possessing the internal guest binding cavities surrounded by the calix[4]arene units are depicted in the graphic. The chirality of a guest is transferred to the helicity of the helicates. The majority-rules effects in the chiral guest binding are found in the helicates possessing the conformationally-coupled guest binding sites. For more information see the Full Paper by T. Haino et al. on page 8558 ff.

Majority‐Rules Effect and Allostery in Molecular Recognition of Calix[4]arene‐Based Triple‐Stranded Metallohelicates

The triple-stranded metallohelicates 1 a,/1 b-3 a/3 b possessing internal guest binding cavities surrounded by calix[4]arene units were synthesized through coordination-driven self-assembly. UV/Vis titration experiments verified that the metallohelicates encapsulated N-methyl pyridinium cations bearing amino acid groups to form host-guest complexes. The guest chirality was transferred to the helicity of the helicates through the steric contact between the stereogenic center of the amino acid group and the metal cores. The (M) helicity was induced when guests the (R)-4--(R)-6 were accommodated within the cavities. The multiple guest complexation within the self-assembled helicates 2 a and 3 a displayed large positive cooperative effects, indicating that the first guest complexation preorganizes the rest of the cavities to facilitate a subsequent guest binding. This cooperativity results in the majority-rules effect in the chiral guest binding for 2 a and 3 a.

In Vitro Corrosion and Antibacterial Performance of Micro-Arc Oxidation Coating on AZ31 Magnesium Alloy: Effects of Tannic Acid

A micro-arc oxidation (MAO) coating was deposited with phytic acid (PA) and tannic acid (TA) on the AZ31 Mg alloy. The surface morphologies and chemical compositions were investigated using field-emission scanning electron microscopy, X-ray photoelectron spectrometry, Fourier transform infrared and X-ray diffractometry. Plate counting method was employed to confirm the antibacterial effect of the TA. The corrosion resistance of the coating was measured using electrochemical and hydrogen evolution tests. The results indicated that the thicker TA-MAO coating had smaller pores, no micro-cracks compared to the MAO coating, which possessed a good corrosion resistance and antibacterial activity in Hank's solution. The molecular recognition effect of TA was discussed. TA also could be used as a stabilizing agent of the hydroxyapatite (HA) precipitate during the immersion. Additionally, the corrosion mechanism for the TA-MAO coating was proposed.

Sorting of C4 Olefins with Interpenetrated Hybrid Ultramicroporous Materials by Combining Molecular Recognition and Size-Sieving.

C4 olefin separations present one of the great challenges in hydrocarbon purifications owing to their similar structures, thus a single separation mechanism often met with limited success. Herein we report a series of anion-pillared interpenetrated copper coordination for which the cavity and functional site disposition can be varied in 0.2 Å scale increments by altering the anion pillars and organic linkers (GeFSIX-2-Cu-i (ZU-32), NbFSIX-2-Cu-i (ZU-52), GeFSIX-14-Cu-i (ZU-33)), which enable selective recognition of different C4 olefins. In these materials the rotation of the organic linkers is controlled to create a contracted flexible pore window that enables the size-exclusion of specific C4 olefins, while still adsorbing significant amounts of 1,3-butadiene (C4 H6 ) or 1-butene (n-C4 H8 ). Combining the molecular recognition and size-sieving effect, these materials unexpectedly realized the sieving of C4 H6 /n-C4 H8 , C4 H6 /iso-C4 H8 , and n-C4 H8 /iso-C4 H8 with high capacity.

Role of Solvation in Drug Design as Revealed by the Statistical Mechanics Integral Equation Theory of Liquids.

Recent developments and applications in theoretical methods focusing on drug design and particularly on the solvent effect in molecular recognition based on the three-dimensional reference interaction site model (3D-RISM) theory are reviewed. Molecular recognition, a fundamental molecular process in living systems, is known to be the functional mechanism of most drugs. Solvents play an essential role in molecular recognition processes as well as in ligand-protein interactions. The 3D-RISM theory is derived from the fundamental statistical mechanics theory, which reproduces all solvation thermodynamics naturally and has some advantages over conventional solvation methods, such as molecular simulation and the continuum model. Here, we review the basics of the 3D-RISM theory and methods of molecular recognition in its applications toward drug design.

Exploration of a ternary deep eutectic solvent of methyltriphenylphosphonium bromide/chalcone/formic acid for the selective recognition of rutin and quercetin in Herba Artemisiae Scopariae.

Methyltriphenylphosphonium bromide/chalcone/formic acid, a green ternary deep eutectic solvent, was applied as a functional monomer and dummy template simultaneously in the synthesis of a new molecularly imprinted polymer. Ternary deep eutectic solvent based molecularly imprinted polymers are used as a solid-phase extraction sorbent in the separation and purification of rutin and quercetin from Herba Artemisiae Scopariae combined with high-performance liquid chromatography. Fourier transform infrared spectroscopy and field-emission scanning electron microscopy were applied to characterize the deep eutectic solvent based molecularly imprinted polymers synthesized using different molar ratios of chalcone. The static and competitive adsorption tests were performed to examine the recognition ability of the molecularly imprinted polymers to rutin and quercetin. The ternary deep eutectic solvent consisting of formic acid/chalcone/methyltriphenylphosphonium bromide (1:0.05:0.5) had the best molecular recognition effect. After optimization of the washing solvents (methanol/water, 1:9) and eluting solvents (acetonitrile/acetic acid, 9:1), a reliable analytical method was developed for strong recognition towards rutin and quercetin in Herba Artemisiae Scopariae with satisfactory extraction recoveries (rutin: 92.48%, quercetin: 94.23%). Overall, the chalcone ternary deep eutectic solvent-based molecularly imprinted polymer coupled with solid-phase extraction is an effective method for the selective purification of multiple bioactive compounds in complex samples.

Ternary choline chloride/caffeic acid/ethylene glycol deep eutectic solvent as both a monomer and template in a molecularly imprinted polymer.

A molecularly imprinted polymer based on a ternary deep eutectic solvent comprised of choline chloride/caffeic acid/ethylene glycol was prepared. The caffeic acid in the ternary deep eutectic solvent was used as both a monomer and template. The molecularly imprinted polymer based on the ternary deep eutectic solvent was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, field-emission scanning electron microscopy, Brunauer-Emmett-Teller surface area analysis, atomic force microscopy, and elemental analysis. A series of molecularly imprinted polymers based on choline chloride/caffeic acid/ethylene glycol with different molar ratios was prepared and applied to the molecular recognition of polyphenols. A comparison of the recognition ability of molecularly imprinted polymers to polyphenols revealed that the choline chloride/caffeic acid/ethylene glycol (1:0.4:1, molar ratio) molecularly imprinted polymer had the best molecular recognition effect with 132μg/g of protocatechuic acid, 104μg/g of catechins, 80μg/g of epicatechin, and 123μg/g of caffeic acid in 6h, as well as good molecular recognition ability for polyphenols from a Radix Asteris sample. These results show that the ternary deep eutectic solvent based molecularly imprinted polymer is a potential medium that can be applied to drug purification, drug delivery, and drug analysis.

Laser Spectroscopic Study of Cold Gas-Phase Host-Guest Complexes of Crown Ethers.

The structure, molecular recognition, and inclusion effect on the photophysics of guest species are investigated for neutral and ionic cold host-guest complexes of crown ethers (CEs) in the gas phase. Here, the cold neutral host-guest complexes are produced by a supersonic expansion technique and the cold ionic complexes are generated by the combination of electrospray ionization (ESI) and a cryogenically cooled ion trap. The host species are 3n-crown-n (3nCn; n = 4, 5, 6, 8) and (di)benzo-3n-crown-n ((D)B3nCn; n = 4, 5, 6, 8). For neutral guests, we have chosen water and aromatic molecules, such as phenol and benzenediols, and as ionic species we have chosen alkali-metal ions (M(+) ). The electronic spectra and isomer-specific vibrational spectra for the complexes are observed with various laser spectroscopic methods: laser-induced fluorescence (LIF); ultraviolet-ultraviolet hole-burning (UV-UV HB); and IR-UV double resonance (IR-UV DR) spectroscopy. The obtained spectra are analyzed with the aid of quantum chemical calculations. We will discuss how the host and guest species change their flexible structures for forming best-fit stable complexes (induced fitting) and what kinds of interactions are operating for the stabilization of the complexes. For the alkali metal ion•CE complexes, we investigate the solvation effect by attaching water molecules. In addition to the ground-state stabilization problem, we will show that the complexation leads to a drastic effect on the excited-state electronic structure and dynamics of the guest species, which we call a "cage-like effect".

Hierarchical biointerfaces assembled by leukocyte-inspired particles for specifically recognizing cancer cells.

By mimicking certain biochemical and physical attributes of biological cells, bio-inspired particles have attracted great attention for potential biomedical applications based on cell-like biological functions. Inspired by leukocytes, hierarchical biointerfaces are designed and prepared based on specific molecules-modified leukocyte-inspired particles. These biointerfaces can efficiently recognize cancer cells from whole blood samples through the synergistic effect of molecular recognition and topographical interaction. Compared to flat, mono-micro or nano-biointerfaces, these micro/nano hierarchical biointerfaces are better able to promote specific recognition interactions, resulting in an enhanced cell-capture efficiency. It is anticipated that this study may provide promising guidance to develop new bio-inspired hierarchical biointerfaces for biomedical applications.

Analysis of Binding Properties Between β-Cyclodextrin Bipyridine-ruthenium Derivative and Vitamins by Their Fluorescence Spectra

This paper presents a research of the binding interaction of a new synthetized β-cyclodextrin bipyridine-ruthenium derivative[β-CD-Ru(bpy)3] with a series of vitamins using fluorescent spectrometry.The performance of fluorescence emission of β-CD-Ru(bpy)3 was excellent due to the existence of the center of bipyridine-ruthenium.Based on the effect of molecular recognition between β-cyclodextrin and guest molecule,the fluorescence quenching occured because of the energy transfer between the β-CD-Ru(bpy)3 and the vitamin when a kind of vitamin was added.According to the quantitative value of fluorescence quenching,the binding constants of the new derivative with respect to various vitamins were determined by Benesi-Hildebrand Equation.The results show that the binding capacities of the vitamins with β-CD-Ru(bpy)3 were in a descending sequence of VB12VK3VCVA.

Protein destabilisation by ruthenium(ii) tris-bipyridine based protein-surface mimetics

Highly functionalised ruthenium(II) tris-bipyridine receptor 1 which acts as a selective sensor for equine cytochrome c (cyt c) is shown to destabilise the native protein conformation by around 25 °C. Receptors 2 and 3 do not exert this effect confirming the behaviour is a specific effect of molecular recognition between 1 and cyt c, whilst the absence of a destabilising effect on 60% acetylated cyt c demonstrates the behaviour of 1 to be protein specific. Molecular recognition also modifies the conformational properties of the target protein at room temperature as evidenced by ion-mobility spectrometry (IMS) and accelerated trypsin proteolysis.

An innovative approach to molecularly imprinted capillaries for polar templates by grafting polymerization

Molecularly imprinted polymers have been successfully used as selective stationary phases in capillary electrophoresis. Notwithstanding, this technique suffers from several drawbacks as the loss of molecular recognition properties in aqueous media and the lack of feasibility for imprinted systems directed towards highly polar templates soluble in aqueous environments only. Thus, the preparation of imprinted polymers for highly polar, water-soluble analytes, represents a challenge. In this work, we present an innovative approach to overcome these drawbacks. It is based on a surface molecular imprinting technique that uses preformed macromonomers as both functional recognition elements and cross-linking agents. A poly-2-hydroxyethyl-co-methacrylic acid linear polymer was grafted from the surface of silica capillaries. The grafted polymer was exhaustively esterified with methacrylic anhydride to obtain polyethylendimethacrylate-co-methacrylic acid linear chains. Then, as a proof of concept, an adequate amount of a very polar template like penicillin V was added in a hydro-organic mixture, and a thin layer of imprinted polymer was obtained by cross-linking the polymer linear chains. The binding behaviour of the imprinted and non-imprinted capillaries was evaluated in different separation conditions in order to assess the presence of template selectivity and molecular recognition effects. The experimental results clearly show that this innovative kind of imprinted material can be easily obtained in very polar polymerization environments and that it is characterized by enhanced molecular recognition properties in aqueous buffers and good selectivity towards the template and strictly related molecules.

Molecular Recognition Effects in Atomistic Models of Imprinted Polymers

In this article we present a model for molecularly imprinted polymers, which considers both complexation processes in the pre-polymerization mixture and adsorption in the imprinted structures within a single consistent framework. As a case study we investigate MAA/EGDMA polymers imprinted with pyrazine and pyrimidine. A polymer imprinted with pyrazine shows substantial selectivity towards pyrazine over pyrimidine, thus exhibiting molecular recognition, whereas the pyrimidine imprinted structure shows no preferential adsorption of the template. Binding sites responsible for the molecular recognition of pyrazine involve one MAA molecule and one EGDMA molecule, forming associations with the two functional groups of the pyrazine molecule. Presence of these specific sites in the pyrazine imprinted system and lack of the analogous sites in the pyrimidine imprinted system is directly linked to the complexation processes in the pre-polymerization solution. These processes are quite different for pyrazine and pyrimidine as a result of both enthalpic and entropic effects.

Nanoscale segregation, molecular recognition and fluorophobic effect – from molecular design towards complex mesophase morphologies

Mesomorphic structure formation of hydrogen-bonded complexes of amino substituted 1,3,5-triazines with complementary (semiperfluoro)alkoxybenzoic acids is presented. The substitution pattern of both components was modified systematically in order to elucidate the influence of molecular parameters on the mesophase morphologies of the binary mixed systems. The phase sequence of the triazines, and of their associates with the acids, spans the range from smectic layer structures to discontinuous cubic phases composed of closed inverted micelles. Columnar phases with various two-dimensional lattice symmetries and bicontinuous cubic phases were found as intermediates. The mesophase morphologies are discussed in terms of the microsegregation of rigid polar, lipophilic and fluorinated molecular blocks in different sub-spaces along with tailoring the shape of (curved) aggregates by the space requirement of incompatible molecular fragments.