Reversible Inclusion Research Articles

Dynamic control of His-hemin coordination and catalysis by reversible host–guest inclusion in peptide assemblies

Dynamic self-assembly has significant implications in the regulation of the enzyme activities. In this study, we present a histidine-based enzyme-mimicking catalyst, formed by the self-assembly of carefully-engineered FH-based short peptides with hemin, showcasing switchable catalytic activity of hemin due to externally induced reversible inclusion of a cucurbit[7]uril-peptide hybrid. 1H NMR, ITC and theoretical simulation are employed to examine the binding affinity between the guest and host components, and UV–vis spectra are used to investigate changes in the hemin coordination environment. The histidine segment of the short peptide can be partially shielded by the cucurbituril and released following addition of the azo compound, leading to a decrease and subsequent restoration of the histidine-hemin coordination affinity and hemin activity. The photoisomeriziable nature of the azo compound enabled the activation of FHH/hemin activity to be switched on and off by exposure to different wavelengths of light. During the operation, the Phe residue remained within the cucurbituril, allowing reversible inclusion and exposure of the histidine residues. The hemin stayed connected to FHH/cucurbit[7]uril hybrid, preventing the severe aggregation of hemin and irreversible deactivation. This work may provide insights into engineering the dynamic behaviors of the cofactor-dependent catalytic assemblies.

Correction: Second time scale of the metastability of reversible inclusion processes

Correction: Second time scale of the metastability of reversible inclusion processes

Thioflavin-T-Incorporated Cerium-ATP Coordination Polymer Nanoparticles: A Promising System for Detection of Uranyl Ion (UO22+) in Aqueous Medium.

Lanthanide-based coordination polymer nanoparticles (Ln-CPNs) are studied for analytical and biomedical sensing, mainly utilizing the luminescent properties of lanthanides. However, the inclusion of fluorescent guest molecules within the nanoparticles can lead to a stimuli-responsive system with modulated photo-physical properties that can be useful for detecting analytes. In this work, we have synthesized cerium(III) coordination polymer nanoparticles using adenosine triphosphate (ATP) molecules as the ligands. The porous polymeric structure enables CPNs for reversible inclusion and release of thioflavin-T (ThT), which is a weakly emissive dye in the free state but becomes highly emissive when incorporated into the Ce-ATP CPNs. Modulation of the photo-physical properties of ThT-incorporated CPNs in response to the radiotoxic and environmentally alarming uranyl ion (UO22+) has been used for its detection in aqueous medium in the range of 0-20 μM by fluorimetry with an LOD of 80 ng mL-1 (0.34 μM) in deionized water without interference from the most commonly occurring metal ions. Furthermore, the sensing platform has been successfully utilized for UO22+ determination in seawater sample without any pre-treatment and adjustment of pH.

Cyclodextrin usage in textile Industry

Nowadays, there is a great interest in the textile industry for the production of functional textiles using environmentally friendly materials and processes. Cyclodextrins are cyclic oligosaccharides obtained by enzymatic degradation of starch truncated cone shape having a hydrophilic surface containing hydroxyl groups and a cavity with hydrophobic character which can form reversible inclusion complexes with various compounds. Several derivatives of β­cyclodextrin have been synthesized to enable it to attach to textile fibers permanently. Also, different methods have been developed for grafting of native and modified β­cyclodextrin on textile fibers. In this review the methods of application of β­cyclodextrin on different textile substrates for obtaining various functional properties including printability, dyeability, and in finishing application as antibacterial, ultraviolet protection wastewater pollutant removal, and fragrance release properties.

Second time scale of the metastability of reversible inclusion processes

We investigate the second time scale of the metastable behavior of the reversible inclusion process in an extension of the study by Bianchi et al. (Electron J Probab 22:1–34, 2017), which presented the first time scale of the same model and conjectured the scheme of multiple time scales. We show that $$N/d_{N}^{2}$$ is indeed the correct second time scale for the most general class of reversible inclusion processes, and thus prove the first conjecture of the foresaid study. Here, N denotes the number of particles, and $$d_{N}$$ denotes the small scale of randomness of the system. The main obstacles of this research arise in calculating the sharp asymptotics for the capacities, and in the fact that the methods employed in the former study are not directly applicable due to the complex geometry of particle configurations. To overcome these problems, we first thoroughly examine the landscape of the transition rates to obtain a proper test function of the equilibrium potential, which provides the upper bound for the capacities. Then, we modify the induced test flow and precisely estimate the equilibrium potential near the metastable valleys to obtain the correct lower bound for the capacities.

Condensation and Metastable Behavior of Non-reversible Inclusion Processes

In this article, we perform quantitative analyses of metastable behavior of an interacting particle system known as the inclusion process. For inclusion processes, it is widely believed that the system nucleates the condensation of particles because of the attractive nature of the interaction mechanism. The metastable behavior of the inclusion processes corresponds to the movement of the condensate on a suitable time scale, and the computation of the corresponding time scale and the characterization of the scaling limit of the condensate motion are the main problems in the study of metastability of inclusion processes. Previously, these problems were solved for reversible inclusion processes in [Bianchi, Dommers, and Giardin\`a, Electronic Journal of Probability, 22: 1-34, 2017], and the main contribution of the present study is to extend this analysis to a wide class of non-reversible inclusion processes. Non-reversibility is a major obstacle to analyzing such models, mainly because there is no closed-form expression of the invariant measure for the general case, and our main achievement is to overcome this difficulty. In particular, our results demonstrate that the time scale and limiting process of non-reversible inclusion processes are quantitatively and qualitatively different from those of reversible ones, respectively. We emphasize that, to the best of our knowledge, these results are the first rigorous quantitative results in the study of metastability when the invariant measure is not explicitly known. In addition, we consider the thermodynamic limit of metastable behavior of inclusion processes on large torus as in the paper [Armend\'ariz, Grosskinsky, and Loulakis, Probability Theory and Related Fields, 169: 105-175, 2017]. For this model, we observe three different time scales according to the level of asymmetry of the model.

Cyclodextrin-Based Nanosystems as Drug Carriers for Cancer Therapy.

Cyclodextrins have been of great interest as excellent candidates for fabricating versatile nano-drug delivery systems due to their commercial availability, easy functionalization, low immunogenicity, biocompatibility and safety. The possibility of reversible inclusion complex formation between cyclodextrins and various guest molecules in association with versatile exclusive properties of cyclodextrins offer a route towards the fabrication of highly sophisticated nanostructures with enormous potential for cancer treatment. The current review discusses important recent advances in the fabrication and development of cyclodextrin-based nanostructures for cancer therapy. Firstly, the formation of inclusion complexes between cyclodextrin derivatives and anticancer compounds, as well as their application, are summarized. Secondly, the cyclodextrins -based nanosystems including cyclodextrin-containing polymers, cyclodextrin-based supramolecular necklaces, which consist of polyrotaxanes and polypseudorotaxanes and cyclodextrin based hydrogels accompanied by their applications in cancer treatment are highlighted. In the end, the future perspective of this field is discussed. Numerous investigations in this area pave the way for the flourishing of the next generation of nano-therapeutics towards enhanced cancer therapy.

Thiolated hydroxypropyl-β-cyclodextrin as mucoadhesive excipient for oral delivery of budesonide in liquid paediatric formulation.

Budesonide (BUD) is a low water soluble (S0 = 5.028·10-5 M) corticosteroid used as preferred therapy for the treatment of Eosinophilic Esophagitis (EoE), a chronic allergic-immune condition with an increased incidence in the paediatric population. Currently there are no commercial medicines indicated for EoE, and, therefore, in the hospital pharmacy the BUD is extemporaneously formulated as viscous oral suspension at the initial dose of 1-2 mg per day for children, highlighting the need of a mucoadhesive drug delivery system (MDDS) that adheres to the site of action and prolongs the therapeutic activity of the administered drug. Considering the ability of hydroxypropyl-β-cyclodextrin (HP-β-CD, 100 mM) to increase the water solubility of BUD (SHP-β-CD = 4.3·10-3 M; K1:1 = 861.11 M-1), a mucoadhesive thiolated HP-β-CD (HP-β-CD-SH) was synthesized and characterized by mass spectroscopy, 1H- and 13C NMR techniques. Phase-solubility studies demonstrated the capability of HP-β-CD-SH (100 mM) to form a reversible water soluble inclusion complex with BUD (SHP-β-CD-SH = 10.9·10-3 M; K1:1 = 2013.52 M-1), which increases its permanence on the target site as proved by mucoadhesive studies on porcine oesophagus mucosa. HP-β-CD-SH might be a useful MDDS for the pharmacist to prepare BUD oral liquid formulations at the recommended doses, with pH values below 5, which guarantee the chemical stability of the new mucoadhesive excipient.

Сitric acid influence on electroreduction processes in low concentrated Cu(NO3)2 solutions

Physico-chemical regularities citric acid influence on processes of copper and nitrate-ions reduction in low concentrated nitrate solutions were established. An influence of pH value on inhibitor action of low concentrations of the additive according to cathode reduction reaction of nitrate-ions, on kinetics of copper electrodeposition, on structure of the precipitates obtained was shown. Polarization measurements show us changes of copper electrodeposition at introduction of citric acid in Cu(NO3)2 solution. By the methods of traced elements and extraction into aqueous phase the reversible inclusion complexes into electrolytic copper, was established that proves participation of complexes in cathode process.

Metastability in the reversible inclusion process

We study the condensation regime of the finite reversible inclusion process, i.e., the inclusion process on a finite graph $S$ with an underlying random walk that admits a reversible measure. We assume that the random walk kernel is irreducible and its reversible measure takes maximum value on a subset of vertices $S_\star\subset S$. We consider initial conditions corresponding to a single condensate that is localized on one of those vertices and study the metastable (or tunneling) dynamics. We find that, if the random walk restricted to $S_\star$ is irreducible, then there exists a single time-scale for the condensate motion. In this case we compute this typical time-scale and characterize the law of the (properly rescaled) limiting process. If the restriction of the random walk to $S_\star$ has several connected components, a metastability scenario with multiple time-scales emerges. We prove such a scenario, involving two additional time-scales, in a one-dimensional setting with two metastable states and nearest-neighbor jumps.

Direct inclusion of triphenylphosphine derivatives into the zeolite Y supercage

Thermal treatment of a mixture of triphenylphosphine (1) and zeolite Y at 423 K resulted in inclusion of the former into the zeolite supercage (SC), with up to 1.5 molecules per SC. Similar behavior was observed for cyclohexyldiphenylphosphine and diphosphines. The included molecules were strongly bound by zeolite Y, with desorption observed at higher temperature compared with those of unloaded phosphines. In contrast, inclusion of diphenylmethylphosphine and tri-p-tolylphosphine hardly occurred. The reversible inclusion and desorption of 1 were induced by thermal treatment at 423 and 873 K, respectively. The amount of included 1 increased with the decreasing Al content of zeolite Y, suggesting van der Waals forces as the driving force of inclusion. Calculations using molecular dynamics and density functional theory revealed that each of the three phenyl groups of 1 was inserted into the 12-membered rings of zeolite Y, thus forming inclusion compounds. PdCl2 introduced into the 1-included zeolite Y exhibited high turnover frequency (2.5 × 104 h−1) in the allylic alkylation, suggesting that the PdCl2(PPh3)2 complex included in the SC could be the catalytically active species.

Methodology to study polymers interaction by surface plasmon resonance imaging

The surface plasmon resonance (SPR) technique has been primarily used in the field of biology, in particular for the study of antibody-antigen interactions. Recently, polymers were introduced to form inclusion complexes.We describe here, a methodology based on surface plasmon resonance imaging to study water-resistant and reversible inclusion complexes using systems which are compatible with a cosmetic use. The purpose of this study is to follow in real time the interaction between two polymers.To carry out this study:•A biochip based on a covalent binding of one “host polymer” on a gold-activated surface was developed.•The binding of the host polymer to a guest polymer was monitored.•The presence of interactions between the β-cyclodextrins groups of the host polymer and the adamantyl functional groups of the guest polymer and the possibility of dissociating the complex were established.This technique allowed carrying out parallel assays for optimizing the amount of complexes formed, the host polymer being spotted at five concentrations. It was then possible to study the influence of the concentration in host system for two concentrations of the guest polymer. The concentration in the host polymer yielding the highest immobilization of the guest system was further determined.

A self-assembled conformational switch: a host-guest stabilized triple stem molecular beacon via a photoactivated and thermal regeneration mode.

We present a novel strategy for construction of a conformational switch of a molecular beacon based on the combination of nucleic acid (DNA) self-assembly and reversible host-guest inclusion interaction. With the functionalized probe, the nucleic acid hybridization process can be easily controlled with a photoactivated and thermal regeneration mode.

Azobenzene-Functionalised Core Cross-Linked Star Polymers and their Host–Guest Interactions

Water-soluble poly(2-hydroxyethyl acrylate) (PHEA)-based core cross-linked star polymers were efficiently synthesised with high macroinitiator-to-star-conversion (>95 %) in a one-pot system via single electron transfer-living radical polymerisation. The star polymers display excellent water solubility and the pendant hydroxyl groups provide a platform for facile post-functionalisation with various molecules. In demonstrating this, a photo-isomerisable molecule, 4-(phenylazo)benzoic acid was conjugated onto the preformed stars through partial esterification of the available hydroxyl groups (5–20 %). The azobenzene functionalised stars were subsequently employed to form reversible inclusion complexes with α-cyclodextrin.

Cyclodextrins in Analytical Chemistry: Host–Guest Type Molecular Recognition

Cyclodextrins are utilized in many diverse fields of analytical chemistry, due to their propensity to form reversible inclusion complexes and recognize analytes selectively. This Feature shows how these nanocavities can serve analysts in sample preparation, sensitivity and selectivity improvement, enantio-separation, creating single-molecule sensors, and automatizing DNA sequencing.

Cooperative effect of “flexible” interaction and “flexible” framework in reversible intake and removal of aromatic guest molecules

The metal-organic frameworks of amide based "flexible" ligands has been explored. The reaction of bis-(3-pyridyl)ethanediamide with Cu(PF6)2 resulted in a 1D looped chain, where the PF6(-) anions interact with the amide groups of the chains. This resulted in unavailability of space for guest inclusion in the loops. The exchange of PF6(-) ion with ClO4(-) ion resulted in the intake of aromatic guest molecules, which were monitored by IR and UV-Vis spectroscopy. The capability of the flexible ethyl spacer of bis-(3-pyridyl)ethanediamide to adjust the conformation according to the requirements of the other components of the networks is observed in the present study. This resulted in reversible inclusion and removal of guest molecules triggered by the exchange of anions.

Natural and Biomimetic Materials for the Detection of Insulin

Microgravimetric sensors have been developed for detection of insulin by using quartz crystal microbalances as transducers, in combination with sensitive layers. Natural antibodies as coatings were compared with biomimetic materials to fabricate mass-sensitive sensors. For this purpose polyurethane was surface imprinted by insulin, which acts as a synthetic receptor for reversible analyte inclusion. The sensor responses for insulin give a pronounced concentration dependence, with a detection limit down to 1 μg/mL and below. Selectivity studies reveal that these structured polymers lead to differentiation between insulin and glargine. Moreover, antibody replicae were generated by a double imprinting process. Thus, biological recognition capabilities of immunoglobulins are transferred to synthetic polymers. In the first step, natural-immunoglobulin-imprinted nanoparticles were synthesized. Subsequently, these templated particles were utilized for creating positive images of natural antibodies on polymer layers. These synthetic coatings, which are more robust than natural analogues, can be produced in large amount. These biomimetic sensors are useful in the biotechnology of insulin monitoring.

Reversible and Selective Sensing of Aniline Vapor by Perylene-Bridged Bis(cyclodextrins) Assembly

Detecting volatile amines is a significant topic in quality control of food and medical diagnosis. Selectively sensing a given gaseous amine from other analogues, however, still remains a formidable challenge in solid-state fluorescence sensing because of the lack of specialized binding sites. Herein, we demonstrate a new supramolecular strategy for selectively sensing aniline based on the aggregation of perylene-cyclodextrin conjugate 1. Compared with our previous results based on perylene-bridged bis(permethyl-β-cyclodextrins), the present system achieves a pronounced improvement of both selectivity and reversibility. The sensory material was constructed from the π-stacking aggregate of 1 embedded in poly(vinylidene fluoride) membrane, which ensures benign solid-state fluorescence with potential amplification mechanism as well as convenient preparation and practical operation. Grafting cyclodextrin receptors endows the sensory material with desired selectivity as a result of diverse binding abilities. Especially, the thermodynamically reversible host-guest inclusion leads to the excellent sensing reversibility. The present research opens the way to build new n-type fluorescence sensory materials for detecting volatile amines instantly with compelling selectivity, sensitivity, and reversibility.

Fabrication of reactivated biointerface for dual-controlled reversible immobilization of cytochrome C.

A light or pH dual-responsive reactivated biointerface is fabricated using of photocontrolled reversible inclusion and exclusion reactions between photoresponsive azobenzene-containing self-assembled monolayer and pH-responsive poly(acrylic acid) polymer grafted with cyclodextrins. The dual-controlled reactivated biointerface can be employed for reversible immobilization of redox protein-Cytochrome c, triggered by dual external stimuli-light and pH.

Fully reversible guest exchange in tetraphosphonate cavitand complexes probed by fluorescence spectroscopy

We report here the monitoring of reversible guest inclusion in phosphonate cavitands through a large increase in luminescence intensity caused by the modulation of the exoergonicity of an electron-transfer reaction.