Terminal Amine Research Articles

ZnO Nanowires/Self-Assembled Monolayer Mediated Selective Detection of Hydrogen.

We are proposing a novel self-assembled monolayer (SAM) functionalized ZnO nanowires (NWs)-based conductometric sensor for the selective detection of hydrogen (H2). The modulation of the surface electron density of ZnO NWs due to the presence of negatively charged terminal amine groups (-NH2) of monolayers leads to an enhanced electron donation from H2 to ZnO NWs. This, in turn, increases the relative change in the conductance (response) of functionalized ZnO NWs as compared to bare ones. In contrast, the sensing mechanism of bare ZnO NWs is determined by the chemisorbed oxygen ions. The functionalized ZnO NWs exhibit an eight times higher response compared to bare ZnO NWs at an optimal working temperature of 200 °C. Finally, in comparison to studies in the literature involving strategies to enhance the sensing performance of metal oxides toward H2, like decoration with metal nanoparticles, heterostructures, and functionalization with a metal-organic framework, etc., SAM functionalization showed superior sensing results.

Degradomics defines proteolysis information flow from human knee osteoarthritis cartilage to matched synovial fluid and the contributions of secreted proteases ADAMTS5, MMP13 and CMA1 to articular cartilage breakdown

ObjectivesProteolytic cartilage extracellular matrix breakdown is a major mechanism of articular cartilage loss in osteoarthritis (OA) pathogenesis. We sought to determine the overlap of proteolytic peptides in matched knee OA cartilage and synovial fluid on a proteome-wide scale to increase the prospective biomarker repertoire and to attribute proteolytic cleavages to specific secreted proteases. DesignMatched human knee OA cartilage and synovial fluid (n=5) were analyzed by N-terminomics using Terminal Amine Isotopic Labeling of Substrates (TAILS), comprising labeling and enrichment of protein N-termini, high-resolution mass spectrometry and positional peptide mapping. Donor non-OA articular cartilage was digested with CMA1, MMP13 or ADAMTS5, and TAILS was used to identify cleavage sites, which were matched against cartilage and synovial fluid degradomes. ResultsOf over 20,000 cleaved peptides in the combined OA cartilage and synovial fluid degradomes, 677 peptides, originating from 153 proteins, were present in all cartilage and synovial fluid samples. CMA1, MMP13 and ADAMTS5 digestion of cartilage identified numerous cleavage sites for each protease and distinct cleavage site preferences. Peptides resulting from the activities of these proteases were detected in OA cartilage and synovial fluid. ConclusionsProteolytic fragments from both cartilage and circulating proteins are detectable by synovial fluid degradomics. CMA1, MMP13 and ADAMTS5 activity profiles in cartilage are distinct from each other and the previously determined HtrA1 profile. This work expands the proteolytic biomarker space for OA investigation, suggests that multiple, diverse proteases contribute to cartilage destruction, and demonstrates that their specific contributions can each be defined by multiple biomarkers.

Organic-Inorganic Coupling Strategy: Clamp Effect to Capture Mg2+ for Aqueous Magnesium Ion Capacitor.

The rapid transport kinetics of divalent magnesium ions are crucial for achieving distinguished performance in aqueous magnesium-ion battery-based energy storage capacitors. However, the strong electrostatic interaction between Mg2+ with double charges and the host material significantly restricts Mg2+ diffusivity. In this study, a new composite material, EDA-Mn2O3, with double-energy storage mechanisms comprising an organic phase (ethylenediamine, EDA) and an inorganic phase (manganese sesquioxide) was successfully synthesized via an organic-inorganic coupling strategy. Inorganic-phase Mn2O3 serves as a scaffold structure, enabling the stable and reversible intercalation/deintercalation of magnesium ions. The organic phase EDA adsorbed onto the surface of Mn2O3 as an elastic matrix, works synergistically with Mn2O3, and utilizes bidentate chelating ligands to capture Mg2+. The robust coordination effect of terminal biprotonic amine in EDA enhances the structural diversity and specific capacity characteristics of the composite material, as further corroborated by density functional theory (DFT) calculations, ex-situ XRD, XPS, and Raman spectroscopy. As expected, an aqueous magnesium ion capacitor with EDA-Mn2O3 serving as the cathode can reach 110.17 Wh/kg. This study aimed to explore the practical application value of organic‒inorganic composite electrodes with double-energy storage mechanisms.

Improving Tamoxifen Performance in Inducing Apoptosis and Hepatoprotection by Loading on a Dual Nanomagnetic Targeting System.

Although tamoxifen (TMX) belongs to selective estrogen receptor modulators (SERMs) and selectively binds to estrogen receptors, it affects other estrogen-producing tissues due to passive diffusion and non-differentiation of normal and cancerous cells and leads to side effects. The problems expressed about tamoxifen (TMX) encouraged us to design a new drug delivery system based on magnetic nanoparticles (MNPs) to simultaneously target two receptors on cancer cells through folic acid (FA) and hyaluronic acid (HA) groups. The mediator of binding of two targeting agents to MNPs is a polymer linker, including dopamine, polyethylene glycol, and terminal amine (DPN). Zeta potential, dynamic light scattering (DLS), and Field emission scanning electron microscopy (FESEM) methods confirmed that MNPs-DPN-HA-FA has a suitable size of ~105 nm and a surface charge of -41 mV, and therefore, it can be a suitable option for carrying TMX and increasing its solubility. The cytotoxic test showed that the highest concentration of MNPs-DPN-HA-FA-TMX decreased cell viability to about 11% after 72 h of exposure compared to the control. While the protective effect of modified MNPs on normal cells was evident, unlike tamoxifen, the survival rate of liver cells, even after 180 min of treatment, was not significantly different from the control group. The protective effect of MNPs was also confirmed by examining the amount of malondialdehyde, and no significant difference was observed in the amount of lipid peroxidation caused by modified MNPs compared to the control. Flow cytometry proved that TMX loaded onto modified MNPs can induce apoptosis by targeting the overexpressed receptors on cancer cells. Real-time PCR showed that the modified MNPs activated the intrinsic and extrinsic mitochondrial pathways of apoptosis, so the Bak1/Bclx ratio for MNPs-DPN-HAFA- TMX and free TMX was 70.82 and 0.38, respectively. Also, the expression of the caspase-3 gene increased 430 times compared to the control. On the other hand, only TNF gene expression, which is responsible for metastasis in some tumors, was decreased by both free TMX and MNPs-DPN-HA-FA-TMX. Finally, molecular docking proved that MNPs-DPN-HA-FA-TMX could provide a very stable interaction with both CD44 and folate receptors, induce apoptosis in cancer cells, and reduce hepatotoxicity. All the results showed that MNPs-DPN-HA-FA-TMX can show good affinity to cancer cells using targeting agents and induce apoptosis in metastatic breast ductal carcinoma T-47D cell lines. Also, the protective effects of MNPs on hepatocytes are quite evident, and they can reduce the side effects of TMX.

Substrate O-glycosylation actively regulates extracellular proteolysis.

Extracellular proteolysis critically regulates cellular and tissue responses and is often dysregulated in human diseases. The crosstalk between proteolytic processing and other major post-translational modifications (PTMs) is emerging as an important regulatory mechanism to modulate protease activity and maintain cellular and tissue homeostasis. Here, we focus on matrix metalloproteinase (MMP)-mediated cleavages and N-acetylgalactosamine (GalNAc)-type of O-glycosylation, two major PTMs of proteins in the extracellular space. We investigated the influence of truncated O-glycan trees, also referred to as Tn antigen, following the inactivation of C1GALT1-specific chaperone 1 (COSMC) on the general and MMP9-specific proteolytic processing in MDA-MB-231 breast cancer cells. Quantitative assessment of the proteome and N-terminome using terminal amine isotopic labelling of substrates (TAILS) technology revealed enhanced proteolysis by MMP9 within the extracellular proteomes of MDA-MB-231 cells expressing Tn antigen. In addition, we detected substantial modifications in the proteome and discovered novel ectodomain shedding events regulated by the truncation of O-glycans. These results highlight the critical role of mature O-glycosylation in fine-tuning proteolytic processing and proteome homeostasis by modulating protein susceptibility to proteolytic degradation. These data suggest a complex interplay between proteolysis and O-GalNAc glycosylation, possibly affecting cancer phenotypes.

Fluorinated PAMAM-Arginine Carrier Prodrugs for pH-Sensitive Sustained Ibuprofen Delivery

ObjectiveThe development of an efficient, multifunctional drug delivery system overcoming different obstacles generally associated with drug formulations, including the poor accumulation of the active principle in the target site and its sustained release for prolonged time.MethodsOur study proposes the development of a fluorinated poly(amidoamine) (PAMAM) carrier prodrug combining drug release boosted in alkaline environments with a possible implementation in 19F MRI applications. In particular, we functionalized the terminal primary amines of PAMAM G2 and G4 through an ad hoc designed fluorinated ibuprofen-arginine Michael acceptor to obtain multifunctional ibuprofen-PAMAM-Arg conjugates.ResultsThese carriers demonstrated pH-dependent and sustained ibuprofen release for more than 5 days. This advantage was observed in both weak alkaline and physiological buffer solutions, allowing to overcome the limits associated to the burst release from similar fluorinated Arg-PAMAM dendrimers with ibuprofen physically encapsulated.ConclusionThese findings, coupled to the high biocompatibility of the system, suggest a potential synergistic biomedical application of our conjugates, serving as vehicles for drug delivery and as 19F magnetic resonance imaging contrast agents.

Tailoring Highly Branched Poly(β-amino ester)s for Efficient and Organ-Selective mRNA Delivery.

Development of mRNA therapeutics necessitates targeted delivery technology, while the clinically advanced lipid nanoparticles face difficulty for extrahepatic delivery. Herein, we design highly branched poly(β-amino ester)s (HPAEs) for efficacious organ-selective mRNA delivery through tailoring their chemical compositions and topological structures. Using an "A2+B3+C2" Michael addition platform, a combinatorial library of 219 HPAEs with varied backbone structures, terminal groups, and branching degrees are synthesized. The branched topological structures of HPAEs provide enhanced serum resistance and significantly higher mRNA expression in vivo. The terminal amine structures of HPAEs determine the organ-selectivity of mRNA delivery following systemic administration: morpholine facilitates liver targeting, ethylenediamine favors spleen delivery, while methylpentane enables mRNA delivery to the liver, spleen, and lungs simultaneously. This study represents a comprehensive exploration of the structure-activity relationship governing both the efficiency and organ-selectivity of mRNA delivery by HPAEs, suggesting promising candidates for treating various organ-related diseases.

Leveraging High-Resolution Ion Mobility-Mass Spectrometry for Cyclic Peptide Soft Spot Identification.

Cyclic peptides are an important class of molecules that gained significant attention in the field of drug discovery due to their unique pharmacological characteristics and enhanced proteolytic stability. Yet, gastrointestinal degradation remains a major hurdle in the discovery of orally bioavailable cyclic peptides. Soft spot identification (SSID) of the regions in the cyclic peptide sequence susceptible to amide hydrolysis by proteases is used in the discovery stage to guide medicinal chemistry design. SSID can be an arduous task, traditionally performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS), often resulting in complex and time-consuming manual analysis, particularly when isomeric linear peptide metabolites chromatographically coelute. Here, we present an alternative orthogonal approach that entails a high-resolution ion mobility (HRIM) system based on Structures for Lossless Ion Manipulation (SLIM) technology interfaced with quadrupole time-of-flight (QTOF) mass spectrometry to address some of the challenges associated with SSID. Two strategies were used to resolve linear isomeric peptide metabolites: labeled and label-free, both utilizing the HRIM platform. The label-free strategy leverages negative polarity to ionize the isomers which achieves better separation of the gas phase ions in the ion mobility (IM) dimension as compared to positive polarity, which is a more conventional approach when studying proteins and peptides. The second approach uses an isotope-labeled dimethyl tag on the terminal amine group, acting as a "shift reagent" to influence the mobility of isomers in the positive mode. This method resulted in baseline separation for the isomers of interest and produced unique product ions in the fragmentation spectra for unambiguous soft spot identification. Both label-free and labeled strategies demonstrated the ability to solve the challenges associated with SSID for cyclic peptides.

An eco friendly approach for the development of a dipeptide based anti-TB drug nanocomposites: A greener approach in drug delivery system for pulmonary delivery

The conventional anti tubercular (anti-TB) treatment strategies constitute challenges in terms of patient compliance and treatment outcomes. Nano-therapeutics is an emerging field with increasing demand for the therapeutic management of tuberculosis (TB) and the challenges over acquired drug toxicity and poor availability. Nevertheless, studies based on nanopeptide drug carrier for the delivery of anti-TB drugs are scanty. The present work emphasizes on the development of a nanocarrier system through hydrothermal process for encapsulating anti-TB drugs (rifampicin, isoniazid, pyrazinamide, ethambutol) using carnosine dipeptide for the potential therapeutic application. The carnosine-anti-TB drug nanocomposites were synthesized by treating native carnosine and anti-TB drugs at an equal ratio (1:1) incubated at 65°C for 30 min (pH 5.3). The hybrid clusters were freeze dried and used further for characterization (physiochemical, biological, morphology and in silico methods). The structural and functional annotations of carnosine and anti-TB drug nanocomposites were confirmed from its terminal amine absorption stretching’s and its amino group fingerprinting regions. The homogenous nature of carnosine-anti-TB drug complexes in solutions was demonstrated with the particle size (>1 μm), that is suitable for macrophage uptake. SEM analysis demonstrated the interactions and functional group orientation between carnosine and anti-TB drugs during the self-assembly process. The drug release profile indicated that the carnosine-drug conjugation promoted the sustained release compared to free drugs. The quantum mechanical calculations define the structural modelling of drugs with carnosine to obtain a stable energy-minimized conformation. To conclude, the developed carnosine- anti-TB drug nanoclusters with enhanced stability and uniformity in size makes them suitable for macrophage uptake and targeted delivery approaches during TB treatment.

Identification of the proteolytic signature in CVB3-infected cells.

RNA viruses encode proteases that are responsible for processing viral proteins into their mature form. Viral proteases also target and cleave host cellular proteins; however, the full catalog of these target proteins is incomplete. We use a technique called terminal amine isotopic labeling of substrates (TAILS), an N-terminomics to identify host proteins that are cleaved under virus infection. We identify hundreds of cellular proteins that are cleaved under infection, some of which are targeted directly by viral protease. Revealing these target proteins provides insights into the host cellular pathways and antiviral signaling factors that are modulated to promote virus infection and potentially leading to virus-induced pathogenesis.

Enhanced water permeability and antifouling properties of cross-linked graphene oxide composite membranes with tunable d-spacings

Low flux and membrane fouling are major challenges in membrane distillation (MD) for treating concentrated wastewater. This study compared the performance of GO composite membranes with different interlayer distances, by covalently bonding the terminal amine groups of ethylenediamine (EDA) and 1,12-diaminododecane (DADD) with the carboxyl groups present on the GO sheets. The results indicated that the GO-DADD/PTFE membrane, with longer carbon chain cross-linking, achieved the highest flux and antifouling properties. At 70 °C, the pure water flux reached 68.5 kg/m2·h, and the fluxes for treating NaCl, HA containing NaCl, and BSA containing NaCl were 29.8 %, 37.1 %, and 38.5 % higher than the uncrosslinked GO/PTFE, and 95.7 %, 121.2 %, and 146.9 % higher than the PTFE membrane, respectively. Through mathematical models for mass and heat transfer, the study identified the key to this enhancement as the increased d-spacing within the GO layer due to cross-linking, which weakened the Kelvin effect and enhanced the vapor partial pressure on the hot side. The unique surface structure and electrostatic interactions induced by long-chain cross-linking further boosted the antifouling effect. These modifications not only overcome the typical trade-off between retention rates and flux but also offer a scalable and efficient solution for advanced membrane distillation applications.

Unravelling the Antifibrinolytic Mechanism of Action of the 1,2,3-Triazole Derivatives.

A new family of antifibrinolytic drugs has been recently discovered, combining a triazole moiety, an oxadiazolone, and a terminal amine. Two of the molecules of this family have shown activity that is greater than or similar to that of tranexamic acid (TXA), the current antifibrinolytic gold standard, which has been associated with several side effects and whose use is limited in patients with renal impairment. The aim of this work was to thoroughly examine the mechanism of action of the two ideal candidates of the 1,2,3-triazole family and compare them with TXA, to identify an antifibrinolytic alternative active at lower dosages. Specifically, the antifibrinolytic activity of the two compounds (1 and 5) and TXA was assessed in fibrinolytic isolated systems and in whole blood. Results revealed that despite having an activity pathway comparable to that of TXA, both compounds showed greater activity in blood. These differences could be attributed to a more stable ligand-target binding to the pocket of plasminogen for compounds 1 and 5, as suggested by molecular dynamic simulations. This work presents further evidence of the antifibrinolytic activity of the two best candidates of the 1,2,3-triazole family and paves the way for incorporating these molecules as new antifibrinolytic therapies.

Fabrication of hybrid polyimide composites containing Ladder-like poly(phenyl-co-glycidoxypropyl)silsesquioxane)

Ladder-like structured poly(phenyl-co-glycidoxypropyl) silsesquioxanes with different ratios of phenyl to glycidyl group (LPS64 and LPS 82) were synthesized using simple hydrolysis reaction followed by condensation polymerization of phenyltrimethoxysilane (PTMS) and (3-glycidyloxypropyl)trimethoxysilane (GPTMS). Two series of hybrid polyimide composites (PI/LPS64 and PI/LPS82) with different contents of LPS (10, 20, and 30 wt%) were prepared by the chemical reaction of epoxy groups in LPS64 or LPS82 and the terminal amine groups in poly(amic acid). The dielectric constant (k) of hybrid PI composites (k = 1.3) was lower than that of pure polyimide (k = 2.9) and the degree of roughness was increased according to the increase of LPS contents. The dispersion of LPS in the PI matrix was improved due to the chemical bonding between LPS and PI. The thermal stability of PI/LPS82 was higher than that of PI/LPS64 due to the enhanced π-π stacking between PI matrix and LPS82 with more phenyl groups as compared to LPS64.

Differences in mechanisms between divalent and univalent copper complexes-catalyzed hydroacylation of terminal alkyne with aldehyde and amine

DFT calculations are carried out to investigate the hydroacylation mechanism based on copper-catalyzed A3-coupling tandem reaction of terminal alkynes, aldehydes and amines. The study reveals significant mechanistic differences between copper(I) and copper(II) catalysts. In the Cu(II)-catalyzed system, incorporation of a ligand is deemed necessary for facilitating reactivity, whereas no ancillary ligand is required in Cu(I) system. The ligand, through coordination with the Cu(II) center, stabilizes the key transition states and intermediates, resulting in a substantial reduction in the activation barrier. The ligand exhibits varying effect, with the order of activity being piperidine > pyridine > DMSO, correlating positively with the interaction energy between ligand and Cu complex. Additionally, the study sheds light on the pivotal roles played by the catalyst, ligand, base, and solvent DMSO in the reaction.

Amine-Terminated Phenanthroline Diimides as Aqueous Masking Agents for Am(III)/Eu(III) Separation: An Alternative Ligand Design Strategy for Water-Soluble Lanthanide/Actinide Chelating Ligands.

Selective actinide coordination (from lanthanides) is critical for both nuclear waste management and sustainable development of nuclear power. Hydrophilic ligands used as masking agents to withhold actinides in the aqueous phase are currently highly pursued, while synthetic accessibility, water solubility, acid resistance, and extraction capability are the remaining problems. Most reported hydrophilic ligands are only effective at low acidity. We recently proved that the phenanthroline diimide skeleton was an efficient building block for the construction of highly efficient acid-resistant hydrophilic lanthanide/actinide separation agents, while the limited water solubility hindered the loading capability of the ligand. Herein, amine was introduced as the terminal solubilizing group onto the phenanthroline diimide backbone, which after protonation in acid showed high water solubility. The positively charged terminal amines enhanced the ligand water solubility to a large extent, which, on the other side, was believed to be detrimental for the coordination and complexation of the metal cations. We showed that by delicately adjusting the alkyl chain spacing, this intuitive disadvantage could be relieved and superior extraction performances could be achieved. This work holds significance for both hydrophilic lanthanide/actinide separation ligand design and, concurrently, offers insights into the development of water-soluble lanthanide/actinide complexes for biomedical and bioimaging applications.

Exploring various carbon nanomaterials-based electrodes modified with polymelamine for the reagentless electrochemical immunosensing of Claudin18.2

Claudin18.2 (CLDN18.2) is a tight junction protein often overexpressed in various solid tumors, including gastrointestinal and esophageal cancers, serving as a promising target and potential biomarker for tumor diagnosis, treatment assessment, and prognosis. Despite its significance, no biosensor has been reported to date for the detection of CLDN18.2. Here, we present the inaugural immunosensor for CLDN18.2. In this study, an amine-rich conducting polymer of polymelamine (PM) was electrografted onto different carbon nanomaterial-based screen-printed electrodes (SPEs), including carbon (C), graphene (Gr), graphene oxide (GO), carbon nanotube (CNT), and carbon nanofiber (CNF) via cyclic voltammetry. A comparative study was performed to explore the best material for the preparation of the PM-modified electrodes to be used as in-situ redox substrate for the immunosensor fabrication. The surface chemistry and structural features of pristine and PM-deposited electrodes were analyzed using Raman and scanning electron microscopy (SEM) techniques. Our results showed that the PM deposited on Gr and CNT/SPEs exhibited the most significant and stable redox behavior in PBS buffer. The terminal amine moieties on the PM-modified electrode surfaces were utilized for immobilizing anti-CLDN18.2 monoclonal antibodies via N-ethyl-N′-(3-(dimethylamino)propyl)carbodiimide/N-hydroxysuccinimide chemistry to construct the electrochemical immunosensor platform. Differential pulse voltammetry-based immunosensing of CLDN18.2 protein on BSA/anti-CLDN18.2/PM-Gr/SPE and BSA/anti-CLDN18.2/PM-CNT/SPE exhibited excellent selectivity against other proteins such as CD1, PDCD1, and ErBb2. The limits of detection of these two immunosensor platforms were calculated to be 7.9 pg/mL and 0.104 ng/mL for the CNT and Gr immunosensors, respectively. This study demonstrated that the PM-modified Gr and CNT electrodes offer promising platforms not only for the reagentless signaling but also for covalent immobilization of biomolecules. Moreover, these platforms offer excellent sensitivity and selectivity for the detection of CLDN18.2 due to its enhanced stable redox activity. The immunosensor demonstrated promising results for the sensitive detection of CLDN18.2 in biological samples, addressing the critical need for early gastric cancer diagnosis.

Zwitterionic targeting nanodrugs prepared from poly(propyleneimine) dendrimers for enhanced anti-tumor therapy

Development of targeting and high drug loading drug delivery system has been gaining great interest. Zwitterionic modification of the terminal amine groups on G2 poly(propyleneimine) (G2 PPI) dendrimers was achieved via the thiol-ene click reaction, followed by the introduction of the anti-cancer drug paclitaxel and targeting peptides c(RGDfC), then the micelles were formed through self-assembly behavior, subsequently doxorubicin was encapsulated internally, finally the targeting drug-loaded micelles PPIMPRC-DOX were synthesized. The PPIMPRC-DOX micelles were irregular spherical with good monodispersity. The average particle size from TEM image was 63.05 nm and the hydrodynamic size was 93.1 nm, both of which were relatively uniform. The critical micelle concentration was 48.52 μg/mL, the total drug loading efficiency was 32.45 %. In vitro release experiments revealed that within the mildly acidic environment of tumors, PPIMPRC-DOX micelles exhibited enhanced release efficiency and increased accumulation of DOX. The anti-nonspecific protein adsorption experiment proved that the interaction between the PPIMPRC-DOX micelles and fibrinogen was very weak, and they had good anti-nonspecific protein adsorption ability. The cytotoxicity assessments using the MTT assay on HeLa cells and A549 cells revealed obvious cytotoxic effects of PPIMPRC-DOX micelles on both cells. Hence, the utilization of zwitterionic G2 PPI dendrimers in constructing PPIMPRC-DOX micelles holds promise as a prospective nanodrug delivery system.

Solution structure, crystal structure, Hirshfeld surface analysis of copper(II) diamide species as an optical chemical sensor

Optical chemical sensors are promising tools for the detection of metal ions in various samples. Copper(II) has received significant attention among metal ions due to its toxic nature and widespread applications in various industrial processes. In recent years, several optical chemical sensors have been developed to detect copper(II) with high sensitivity and selectivity. This paper describes the spectrophotometric determination of trace amounts of copper(II) using N1-(2-aminoethyl)-N2-((pyridin-2-yl)methyl)oxalamide (H2(555)NH2) as an optical chemical sensor. The protonation and formation constants of the Cu(II)/(H2(555)NH2) system were determined at 25 °C and the ionic strength of 0.15 mol dm−3 using glass electrode potentiometry. The structures of the different species, present in solution at different pH values, were determined using UV–vis, 1H NMR, and EPR spectroscopic techniques. At pH 5, the [Cu(H2(555)NH2)]2+ species was formed with the Cu(II) coordinated to the pyridole nitrogen and the terminal amine. Above pH 8, [Cu(H2(555)NH2)H-2] is the most predominant species in solution. Here the Cu(II) coordinates to all four nitrogen atoms. In the solid state, a dinuclear complex, [Cu(H(55)NH3)Cl]2[Cu(H2O)2(NO3)2Cl2]H2O, was formed. Single crystal X-ray structure showed the Cu(II) to be coordinated to the pyridine and the amide N-atoms in addition to an O-atom from one of the two carbonyl groups. The coordination environment was completed by two bridged chloride ions to give a slightly distorted trigonal bipyramidal coordination geometry around the copper centre. The amine was not coordinated. The proposed sensor was successfully applied to determine copper(II) in real samples, with recoveries ranging from 10−5 to 10−3 mol/dm−3. Using H2(555)NH2 as an optical chemical sensor emerged as a powerful tool for detecting copper(II) ions in different aqueous samples.

Multifunctional composite materials of rGO with RAFT initiated polymers with terminal amine or protonated amine functionalities for chemical eliminations HCHO and acidic pollutants at ambient conditions

In this paper, the contribution of self-assembled composite material of bifunctional polymer prepared by RAFT polymerization and rGO to the removal of low concentration HCHO and acids from air were systematically studied. Experimental results demonstrate that the condensation reaction between HCHO and the protonated amino group at the terminal of the rGO-py-pAMHS-NH3+-ph chain effectively can eliminate HCHO chemically, resulting in the release of H2O as the sole by-product following oxime bonds formation. rGO alone is incapable of chemically removing gaseous HCHO, but when combined with the py-pAMHS-NH3+-ph, efficient HCHO conversion can be achieved, well elucidating the remarkable HCHO removal capability via rGO-py-pAMHS-NH3+-ph. The HCHO chemical removal performance of composite is evaluated by a self-made device at the 1000 mL/min N2 velocity under 25 °C and 50 % RH and it is found that 206.41 mg of HCHO can be removed in approximately 4 h by using 1.0 g of rGO-py-pAMHS-NH3+-ph. In addition, cycling experiments demonstrate the rGO-py-pAMHS-NH3+-ph possesses good durability. We also find that the rGO-py-pAMHS-NH2-ph has the ability to remove acids when the terminal protonated amino groups have been converted into amine functionalities. This green and zero-carbon emission methodology for chemical removal of HCHO degradation and acid pollutants could provide valuable reference for developing other efficient strategies to remove other pollutants such as VOCs etc.

Spontaneous Curvature Induction in an Artificial Bilayer Membrane.

Maintaining lipid asymmetry across membrane leaflets is critical for functions like vesicular traffic and organelle homeostasis. However, a lack of molecular-level understanding of the mechanisms underlying membrane fission and fusion processes in synthetic systems precludes their development as artificial analogs. Here, we report asymmetry induction of a bilayer membrane formed by an extended π-conjugated molecule with oxyalkylene side chains bearing terminal tertiary amine moieties (BA1) in water. Autogenous protonation of the tertiary amines in the periphery of the bilayer by water induces anisotropic curvature, resulting in membrane fission to form vesicles and can be monitored using time-dependent spectroscopy and microscopy. Interestingly, upon loss of the induced asymmetry by extensive protonation using an organic acid restored bilayer membrane. The mechanism leading to the compositional asymmetry in the leaflet and curvature induction in the membrane is validated by density functional theory (DFT) calculations. Studies extended to control molecules having changes in hydrophilic (BA2) and hydrophobic (BA3) segments provide insight into the delicate nature of molecular scale interactions in the dynamic transformation of supramolecular structures. The synergic effect of hydrophobic interaction and the hydrated state of BA1 aggregates provide dynamicity and unusual stability. Our study unveils mechanistic insight into the dynamic transformation of bilayer membranes into vesicles.