Reversible Complex Research Articles

Fluorescent robust photoactuator via photo-crosslinking induced single-layered janus polyimide

Advanced smart polymer materials with the ability of reversible deformation under external stimuli hold great potential in robotics, soft machines, and flexible electronics. However, the complexity and low efficiency for fabricating actuators along with their limited functionality hinder further progress. Here an efficient and mild catalyst-free thiol-yne click polymerization was developed to fabricate photosensitive polyimide (PI) films. Then the fluorescent robust photoactuators with single-layered janus structure were directly obtained via UV assisted photo-crosslinking of the films, exhibiting reversible response driven by a pronounced mismatch in expansion between the front and back sides of the films. Achieving selective, non-uniform spatial distribution within the PI films, rapid and reversible complex morphing of the actuators, along with the capabilities for encrypting, reading, and erasing fluorescent information—all through the use of a single UV light source—becomes straightforward. The robust mechanical property and driving ability of these actuators enable the conversion of light energy into obvious motion even under heavy loads and the leaping through the storage and release of energy, ensuring their potential for practical applications that require durability and reliability.

Network transformation-based analysis of biochemical systems.

A dynamical system obtains a wide variety of kinetic realizations, which is advantageous for the analysis of biochemical systems. A reaction network, derived from a dynamical system, may or may not possess some properties needed for a thorough analysis. We improve and extend the work of Johnston and Hong et al. on network translations to network transformations, where the network is modified while preserving the dynamical system. These transformations can shrink, extend, or retain the stoichiometric subspace. Here, we show that a positive dependent network can be translated to a weakly reversible network. Using the kinetic realizations of (1) calcium signaling in the olfactory system and (2) metabolic insulin signaling, we demonstrate the benefits of transformed systems with positive deficiency for analyzing biochemical systems. Furthermore, we present an algorithm for a network transformation of a weakly reversible non-complex factorizable kinetic (NFK) system to a weakly reversible complex factorizable kinetic (CFK) system, thereby enhancing the Subspace Coincidence Theorem for NFK systems of Nazareno et al. Finally, using the transformed kinetic realization of monolignol biosynthesis in Populus xylem, we study the structural and kinetic properties of transformed systems, including the invariance of concordance and variation of injectivity and mono-/multi-stationarity under network transformation.

Fabrication of Zinc(II) Mediated Poly(Acrylamide Co Acrylic Acid) Hydrogel with Thixotropic and Tribological Properties.

Hydrogels have emerged as promising candidates for biomedical applications, such as replacing natural articular cartilage, owing to their unique viscoelastic properties. However, sufficient mechanical properties, self-healing ability, and adhesive nature are some issues limiting its application window. Here, a facile one-pot synthesis of dual cross-linked zinc-coordinated copolymer hydrogels is presented. The network structure of the copolymer hydrogels is strategically developed via dynamic and reversible physical cross-linking by Zn2+ ions and simultaneous covalent cross-linking through a covalent cross-linker viz methylene bisacrylamide. Fourier-transform infrared (FTIR), X-ray diffraction (XRD) scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) analysis have thoroughly characterized the structure of the synthesized hydrogels. The introduction of Zn2+ offers dynamic and reversible complexation, leading to excellent mechanical properties and self-healing features. Moreover, the percentage of the equilibrium water content of zinc-coordinated copolymer hydrogel samples is comparable with that of natural articular cartilage. The Shear sliding study shows the dominant adhesive behavior of HGel-Zn(NO3)2 sample compared to the parent HGel sample. This facile dual cross-linked hydrogel, HGel-Zn(NO3)2, with a combination of good mechanical properties, efficient self-recovery, adequate water content, and favorable adhesive nature, seems very promising to mimic the articular cartilage.

Physical-information model of the immune system as a development of P.K. Anokhin’s theory of functional systems

The article deals with the standard immunological model, which is based on the principles of random combination of molecules and cells and their random encounter with their complementary sites, which is accompanied by the formation of reversible complexes and/or a cascade of subsequent reactions. In its purity, such a model gives rise to various kinds of paradoxes that do not correspond to the reality of immune processes. As a rule, the development of immunology is expressed in the construction of more and more detailed links of immunologic events, but the addition of each new event to the chain of links should lead not to acceleration, but to slowing down of the final process within the combinatorial-complementary system. In this connection, the question of a new possible model of the immune system is raised, which is based on P.K. Anokhin’s theory of functional systems. As its further development the physical-information model (PhIM) of the immune system is proposed, which assumes two plans, informational and physical, of the immune system organization and their coordination on the basis of the ideas of organic potential and processes of conjugation. The information plan is represented as an abstract space of degrees of freedom of the system, analogous to phase space in physics. The current and final state of the system can be represented as points of the state space, the activity of the system with the transition from the current to the final state, as a trajectory in this space. The acceptor of the action result in the theory of functional systems of P.K. Anokhin is connected in this case with the image of the final state as the result of the system action. The construction of the trajectory of the system’s activity can be represented as the direction of reduction of the organic potential of the system, by analogy with that in the case of physical systems and their physical potentials. The organic potential reaches a minimum in the final state and expresses the need of the biosystem as a result of action.

Mechanism-Based Allylic Carbasugar Chlorides That Form Covalent Intermediates with α- and β-Galactosidases.

Glycoside hydrolases have been implicated in a wide range of human conditions including lysosomal storage diseases. Consequently, many researchers have directed their efforts towards identifying new classes of glycoside hydrolase inhibitors, both synthetic and from natural sources. A large percentage of such inhibitors are reversible competitive inhibitors that bind in the active site often due to them possessing structural features, often a protonatable basic nitrogen atom, that mimic the enzymatic transition state. We report that mechanism-based small molecule galacto-like configured cyclohexenyl carbasugars form reversible covalent complexes with both α-galactosidase and β-galactosidase. In addition, we show that the β-galactosidase from Aspergillus oryzae reacts with three different carbasugar inhibitors, with three different second-order rate constants (kinact/Ki), to give the same enzyme-carbasugar covalent intermediate. The surprising observation that the α-galacto-configured inhibitor covalently labels the A. oryzae β-galactosidase highlights the catalytic versatility of glycoside hydrolases. We expect that cyclohexenyl covalent inhibitors will become an important class of compounds in the chemical biologist's tool box.

The Role of Inducible Nitric Oxide Synthase in Assessing the Functional Level of Coronary Artery Lesions in Chronic Coronary Syndrome.

Chronic coronary syndrome (CCS) is a long-term manifestation of coronary artery disease, marked by stable but recurring chest pain and myocardial ischemia due to the gradual buildup of atherosclerotic plaques in the coronary arteries. It is a metabolic disorder of coronary arteries characterized by oxidative stress, endothelial dysfunction, inflammation, and hyperlipidemia. The imbalance in oxidative-antioxidative status contributes to stable ischemic heart disease. Oxidative stress involves reactive oxygen and nitrogen species, leading to low-density lipoprotein (LDL) oxidation. Endothelial dysfunction, marked by reduced nitric oxide (NO) bioavailability, is an early onset of CCS, affecting vasodilation, cell proliferation, and inflammatory responses. Enzyme myeloperoxidase (MPO), traditionally considered protective, plays a dual role in initiating and progressing inflammatory diseases. MPO interacts with NO, modulating its catalytic activity. Elevated NO levels inhibit MPO through a reversible complex formation, preventing NO-induced inhibition by inducible nitric oxide synthase (iNOS). MPO also inactivates endothelial nitric oxide synthase (eNOS) and reacts with L-arginine, hindering NO synthesis. The interplay between MPO and NO significantly influences inflammation sites, impacting peroxidation rates and oxidation reactions. Peroxynitrite, a reactive species, contributes to nitration of tyrosine residues and lipid peroxidation. Mechanistic pathways suggest MPO enhances iNOS catalytic activity, influencing CCS development. iNOS, implicated in inflammation and atherosclerosis, is connected to NO regulation. This review analyzes the complex interplay of MPO, iNOS, and NO that affects plaque morphology, oxidative stress, and inflammation, contributing to atherosclerosis progression. Therefore, it is possible that the phenotypes of atherosclerotic plaques, focal and diffuse coronary artery disease, could be defined by the relationship between MPO and iNOS.

Free gallium (III) determination with AGNES (Absence of Gradients and Nernstian Equilibrium Stripping)

Gallium is being extensively used in technological applications. Increasing emissions to the environment classify it as an emerging contaminant. Speciation information, such as the free gallium concentration, [Ga3+], is fundamental for understanding/predicting its bioavailability and potential toxicity to biota. In this work, [Ga3+] in aqueous solutions at pH2 and 3 has been measured with AGNES (Absence of Gradients and Nernstian Equilibrium Stripping). The deposition times to reach equilibrium, for a fixed accumulation factor or gain, were longer than those required with other metals such as Zn, Pb, Cd and In. This is attributed to the electrodic irreversibility of the couple Ga0/Ga3+ on the mercury electrode together with low concentrations of relatively poorly labile and/or poorly reversible (for the electrodic transfer) hydroxy complexes. When the AGNES-SCP variant was applied in the Hanging Mercury Drop Electrode with radius 141 μm, and the transition time was ≤10 s, the correction of the deposited mass with a depletion factor was essential. The speciation capacity of AGNES for Ga was evaluated with the phthalate ligand at pH 3 and the experimental results obtained were very similar to the theoretical results predicted with the stability constants in the NIST and Brown-Ekberg databases.

Reversible protein complexes: Advancing subcutaneous delivery with controlled and sustained release of high concentration biologics

High concentration formulations are crucial in developing biological drugs, especially for subcutaneous (SC) administration where the administered dose is adversely impacted by the limited injection volume. In this study, we evaluated the fate and behavior of high concentration formulations of biologics, using the previously described reversible protein complex (RPC) approach and a novel in vitro tool called Subcutaneous Injection Site Simulator (Scissor). The Scissor simulates the changes that a biological drug could encounter as it transitions from a drug product formulation to the homeostatic state of the hypodermis following SC injection. The RPC formulation was injected in a cartridge filled with synthetic extracellular matrix, which was immersed in a release chamber filled with a bicarbonate-based physiological buffer that mimicked the SC injection site and the infinite sink conditions of the body. The system enabled continuous monitoring of the RPC formulation within the cartridge and could be used to characterize physicochemical changes of the drug. The dissociation of RPC and the release of the therapeutic protein from the cartridge to the infinite sink compartment simulated the drug migration from the injection site and uptake to the systemic circulation. Here, we present the evaluation of high concentration RPC formulations using five therapeutic proteins of different formats. Our findings suggest that the Scissor can provide a suitable tool to predict the stability of biological drugs in the subcutaneous environment. Also, the in vitro drug release data obtained from the Scissor highlighted a sustained and controlled release of RPC formulations and a surface erosion-based release mechanism was elucidated thanks to in vitro release models.

Porphyrin complex-based reversible fluorescent film sensor for differentiating and detecting sarin mimics vapor

This study presents a TAPP-based fluorescent sensor for diethylchlorophosphate (DCP), a surrogate for sarin, addressing the critical challenge of detecting nerve agents. The sensor can form a reversible weak bond interaction with the PO group in sarin by using the reversible weak bond complexation mechanism in the porphyrin cavity, which is the key to realize the reversible function of the sensor. In this study, we constructed a fluorescence probe that combines the advantages of physical process and chemical reaction process sensing, which not only ensures selectivity, but also realizes continuous and reversible real-time detection of DCP. The sensor demonstrates excellent photochemical stability and sensitivity, with an actual detection limit of 10 ppt and a theoretical detection limit of 1 ppt. In addition, it can differentiate challenging interferents like HCl through response kinetics, offering a practical, cost-effective, and environmentally sustainable solution for nerve agent detection in high-risk environments.

Reversible complexation mediated polymerization (RCMP) starting with a complex of iodine with organic salt and thermal initiators

Reversible complexation mediated polymerization (RCMP) starting with a complex of iodine with organic salt and thermal initiators

Kinetic Model for the Heterogeneous Biocatalytic Reactions Using Tethered Cofactors.

Understanding the mechanism of interfacial enzyme kinetics is critical to the development of synthetic biological systems for the production of value-added chemicals. Here, the interfacial kinetics of the catalysis of β-nicotinamide adenine dinucleotide (NAD+)-dependent enzymes acting on NAD+ tethered to the surface of silica nanoparticles (SiNPs) has been investigated using two complementary and supporting kinetic approaches: enzyme excess and reactant (NAD+) excess. Kinetic models developed for these two approaches characterize several critical reaction steps including reversible enzyme adsorption, complexation, decomplexation, and catalysis of the surface-bound enzyme/NAD+ complex. The analysis reveals a concentrating effect resulting in a very high local concentration of enzyme and cofactor on the particle surface, in which the enzyme is saturated by surface-bound NAD, facilitating a rate enhancement of enzyme/NAD+ complexation and catalysis. This resulted in high enzyme efficiency within the tethered NAD+ system compared to that of the free enzyme/NAD+ system, which increases with decreasing enzyme concentration. The role of enzyme adsorption onto solid substrates with a tethered catalyst (such as NAD+) has potential for creating highly efficient flow biocatalytic systems.

Crystal structures of an HIV-1 reverse transcriptase second strand initiation complex with and without non-nucleoside inhibitors may explain slow nucleotide incorporation and high sensitivity to inhibition

Crystal structures of an HIV-1 reverse transcriptase second strand initiation complex with and without non-nucleoside inhibitors may explain slow nucleotide incorporation and high sensitivity to inhibition

Reversible solid bromine complexation into Ti3C2Tx MXene carriers: a highly active electrode for bromine-based flow batteries with ultralow self-discharge

The robust and reversible solid bromine complexation effect was incorporated into electrodes, endowing bromine-based flow batteries with ultralow self-discharge.

Methyl-β-cyclodextrin asymmetrically extracts phospholipid from bilayers, granting tunable control over differential stress in lipid vesicles.

Lipid asymmetry - that is, a nonuniform lipid distribution between the leaflets of a bilayer - is a ubiquitous feature of biomembranes and is implicated in several cellular phenomena. Differential tension - that is, unequal lateral monolayer tensions comparing the leaflets of a bilayer- is closely associated with lipid asymmetry underlying these varied roles. Because differential tension is not directly measurable in combination with the fact that common methods to adjust this quantity grant only semi-quantitative control over it, a detailed understanding of lipid asymmetry and differential tension are impeded. To overcome these challenges, we leveraged reversible complexation of phospholipid by methyl-β-cyclodextrin (mbCD) to tune the direction and magnitude of lipid asymmetry in synthetic vesicles. Lipid asymmetry generated in our study induced (i) vesicle shape changes and (ii) gel-liquid phase coexistence in 1-component vesicles. By applying mass-action considerations to interpret our findings, we discuss how this approach provides access to phospholipid thermodynamic potentials in bilayers containing lipid asymmetry (which are coupled to the differential tension of a bilayer). Because lipid asymmetry yielded by our approach is (i) tunable and (ii) maintained over minute to hour timescales, we anticipate that this approach will be a valuable addition to the experimental toolbox for systematic investigation into the biophysical role(s) of lipid asymmetry (and differential tension).

Energy performance of metallic tubular systems under reverse complex loading paths

Energy performance of metallic tubular systems under reverse complex loading paths

The IRE1β-mediated unfolded protein response is repressed by the chaperone AGR2 in mucin producing cells

Effector mechanisms of the unfolded protein response (UPR) in the endoplasmic reticulum (ER) are well-characterised, but how ER proteostasis is sensed is less well understood. Here, we exploited the beta isoform of the UPR transducer IRE1, that is specific to mucin-producing cells in order to gauge the relative regulatory roles of activating ligands and repressing chaperones of the specialised ER of goblet cells. Replacement of the stress-sensing luminal domain of endogenous IRE1α in CHO cells (normally expressing neither mucin nor IRE1β) with the luminal domain of IRE1β deregulated basal IRE1 activity. The mucin-specific chaperone AGR2 repressed IRE1 activity in cells expressing the domain-swapped IRE1β/α chimera, but had no effect on IRE1α. Introduction of the goblet cell-specific client MUC2 reversed AGR2-mediated repression of the IRE1β/α chimera. In vitro, AGR2 actively de-stabilised the IRE1β luminal domain dimer and formed a reversible complex with the inactive monomer. These features of the IRE1β-AGR2 couple suggest that active repression of IRE1β by a specialised mucin chaperone subordinates IRE1 activity to a proteostatic challenge unique to goblet cells, a challenge that is otherwise poorly recognised by the pervasive UPR transducers.

An AIE active anthracene-based Schiff base probe for “turn-on” detection of Cu2+ ions: Demonstrations with nanostructural investigations, DFT, cellular imaging, and real water analysis

An aggregation induced emission (AIE) active anthracene-based Schiff base probe “(2-((anthracen-9-ylmethylene) amino) phenol); AP” was synthesized via one-pot reaction and utilized in “turn-on” detection of Cu2+ ions. Ultraviolet–visible and photoluminescence (UV–vis/PL) interrogations confirm the AIE between 0 and 99 % water fraction (fw) and high selectivity of AP to Cu2+. PL studies establish the linear regression of Cu2+ between 0 and 24 µM with a detection limit (LOD) of 53.2 nM. The Job plot and high-resolution mass (HR-mass) data affirm 2:1 stoichiometry and the association constant (Ka) value appraised as 1.88 × 10−4 M−2. Time-resolved photoluminescence (TRPL) studies reveal decay kinetics of AIE, Cu2+ sensors and complex's reversibility. Moreover, 1H NMR titration and density functional theory (DFT) investigations identify the binding mode, π-π stacking in AIE, AP − Cu2+ − AP* excimer formation, band gap variations and involvement of photoinduced electron transfer (PET) and chelation enhanced fluorescence (CHEF) mechanism. Crystallinity and nanostructural variations of AIE and Cu2+ sensors are investigated by using powder-X-ray diffraction (PXRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and dynamic light scattering (DLS). AIE and Cu2+ sensory method are validated by MDA-MB-231 cellular imaging studies. Finally, real water-based titrations show nanomolar LODs and recoveries > 97 % with RSDs < 3.5 %.

One-Pot Reversible Complexation-Mediated Polymerization (RCMP) from Benzylic Alcohols for Facile Access to Polymer-Grafted Lignin.

One-pot synthesis of methacrylic and acrylic polymers from benzylic alcohols (R-OH) used as initiating moieties was developed. R-OH was converted to alkyl iodide (R-I), and the generated R-I was used as an initiator without purification or isolation in the subsequent reversible complexation mediated polymerization (RCMP), leading to one-pot RCMP from R-OH. As a useful application, this technique was exploited for one-pot polymer-grafting from lignin that is the second most abundant renewable carbon-source on earth and bears benzylic alcohols. The direct initiation from lignin eliminates tedious initiator attachment and purification, offering a facile access to polymer-grafted lignin. The obtained polymer-grafted lignin was utilized to form an efficient UV-absorbing film with high transparency in visible region. One-pot RCMP may serve as a practical method to obtain value-added functional lignin-polymer composites.

One‐Pot Reversible Complexation‐Mediated Polymerization (RCMP) from Benzylic Alcohols for Facile Access to Polymer‐Grafted Lignin

AbstractOne‐pot synthesis of methacrylic and acrylic polymers from benzylic alcohols (R−OH) used as initiating moieties was developed. R−OH was converted to alkyl iodide (R−I), and the generated R−I was used as an initiator without purification or isolation in the subsequent reversible complexation mediated polymerization (RCMP), leading to one‐pot RCMP from R−OH. As a useful application, this technique was exploited for one‐pot polymer‐grafting from lignin that is the second most abundant renewable carbon‐source on earth and bears benzylic alcohols. The direct initiation from lignin eliminates tedious initiator attachment and purification, offering a facile access to polymer‐grafted lignin. The obtained polymer‐grafted lignin was utilized to form an efficient UV‐absorbing film with high transparency in visible region. One‐pot RCMP may serve as a practical method to obtain value‐added functional lignin‐polymer composites.

Facile synthesis of asymmetric tetrablock copolymer by dual thermal and photochemical initiator

Vesicles obtained by the self-assembly of asymmetric tetrablock copolymers are a class of materials with fascinating properties. However, simple strategies to synthesize asymmetric tetrablock copolymers are limited. Herein, we have designed and synthesized an initiator which generates radicals by either heating or photoirradiation. Taking the advantages of organocatalyzed reversible complexation mediated radical polymerization which has lower energy requirements, milder reaction conditions, and reduced generation of hazardous byproducts, a three steps synthetic route following “photo-photo-thermal” initiation condition for the preparation of asymmetric CABC tetrablock copolymers with controllable molecular weight, precise block composition and low polydispersity was developed.