Formation Of Supramolecular Complexes Research Articles

ОСОБЕННОСТИ ВЗАИМОДЕЙСТВИЯ ГЕМИНА И ZnII-КОМПЛЕКСА ТЕТРА(4 ПИРИДИЛ) ПОРФИРИНА С ГЕКСАМОЛИБДЕНОНИКЕЛАТ-ПОЛИАНИОНОМ В ВОДНЫХ СРЕДАХ

This work presents a method for producing new hybrid supramolecular organic-inorganic systems based on tetrapyrrole compounds (natural and artificially synthesized porphyrins) and hexamolibdenonicelate anion to create highly ordered supramolecular complexes based on porphyrins with the possibility of using them in medicine. In particular, the reaction of natural porphyrin (hemin) and the ZnII-complex of tetra(4-pyridyl)porphyrin with the heteropoly compound sodium hexamolibdenonicelate crystalline hydrate Na4[Ni(OH)6Mo6O18]·8H2O in an aqueous medium is considered. This heteropoly compound due to its physicochemical and biological properties can be considered as a part of photochromic materials and pharmacological agent. The optical absorption spectra of the obtained hybrid supramolecular organic-inorganic systems were investigated with the help of electronic absorption spectroscopy. Both the transformation of the bands which are the characteristics of porphyrins and the appearance of new bands indicating the formation of hybrid supramolecular organic-inorganic complexes are observed in the electron absorption spectra. The work traces the role of structural features of porphyrins in the process of their interaction with the heteropolyanions. Differences in the spectral behavior of the two metalloporphyrins when interacting them with the heteropoly compound have been shown and explained by variability in their structure. The data obtained will be useful when developing new hybrid materials as antibacterial components for medical use.

Smartphone-Based Sensing of Cortisol by Functionalized Rhodamine Probes.

During a stress condition, the human body synthesizes catecholamine neurotransmitters and specific hormones (called "stress hormones"), the most important of which is cortisol. The monitoring of cortisol levels should be extremely important to control the stress levels, and for this reason, it shows important medical applications. The common analytical methods (HPLC, GC-MS) cannot be used in real life, due to the bulky size of the instruments and the necessity of specialized personnel. Molecular probes solve these problems due to their fast and easy use. The synthesis of new fluorescent rhodamine probes, able to interact by non-covalent interactions with cortisol, the recognition properties in solution as well as in solid state by Strip Test, using a smartphone as detector, are here reported. DFT calculations and FT-IR measurements suggest the formation of supramolecular complexes through hydrogen bonds as main non-covalent interaction. The present study represents one of the first sensor, based on synthetical chemical receptors, able to detect cortisol in a linear range from 1 mM to 1 pM, based on non-covalent molecular recognition and paves the way to the realization of practical point-of-care device for the monitoring of cortisol in real live.

Creation of photofunctional materials through supramolecular complex formation and host–guest chemistry

Creation of photofunctional materials through supramolecular complex formation and host–guest chemistry

Enabling Superprotonic Phase Transitions in Solid Acids via Supramolecular Complex Formation: The Case of Crown Ethers and Alkali Hydrogen Sulfates

Enabling Superprotonic Phase Transitions in Solid Acids via Supramolecular Complex Formation: The Case of Crown Ethers and Alkali Hydrogen Sulfates

A Deeper Insight into the Supramolecular Activation of Oxidative Addition Reactions Involving Pincer-Rhodium(I) Complexes.

The factors governing the acceleration of the oxidative addition of methyl iodide to pincer rhodium(I)-complexes induced by coronene have been computationally explored in detail using quantum chemical methods. Both the parent reaction and the coronene-mediated process proceed via a stepwise SN2-type mechanism. It is found that the acceleration of the process derives from the formation of an initial supramolecular complex, mainly stabilized by electrostatic and π-π interactions, which significantly increases the electron richness of the complex. The impact of this effect on the reaction barrier has been quantitatively analyzed by applying the activation strain model in combination with the energy decomposition analysis method. In addition, the influence of other polycyclic aromatic hydrocarbons on the oxidative reaction has been also considered.

Revealing the impact of different precursors and solvents for supramolecular complex formation and in-situ C-doping in g-C3N4 with enhanced photocatalytic H2O2 production

The reinforced light-harvesting capability suppresses photocarrier recombination and increases the specific surface area, representing the possibility of excellent photocatalytic performance for graphitic carbon nitride (CN) photocatalysts. Herein, the remarkable photocatalytic properties of porous carbon-doped g-C3N4 (CCN) were enhanced through the incorporation of a supramolecular complex, M-CA-U (melamine-cyanuric acid-urea), in DMSO as the carbon dopant source. Through the diverse characterization methods, the successful formation of the supramolecular g-C3N4 using varying polarity of solvent was verified, achieved through a simple hydrothermal/solvothermal process. The CCN-MCAU-DMSO photocatalyst achieved the maximum photocatalytic H2O2 production rate, 1.3-fold higher than other prepared samples. The outstanding performances of CCN-MCAU-DMSO were probably attributed to the extended specific surface area, robust visible light response, adjusted electronic band structure, accelerated charge separation, and limited charge recombination. The photocurrent response and photoluminescence spectroscopy analysis confirmed excellent charge carriers and separation. Overall, this work provided a new idea to design and construct high-efficiency porous supramolecular assembly of CCN photocatalysts for photocatalytic studies.

A NEW STRATEGY FOR THE SYNTHESIS OF HIGHLY ACTIVE CATALYSTS BASED ON <i>g-</i>C<sub>3</sub>N<sub>4</sub> FOR THE PHOTOCATALYTIC PRODUCTION OF HYDROGEN UNDER VISIBLE LIGHT

In this work, materials based on graphite-like carbon nitride were synthesized by thermal treatment of a mixture of melamine and urea and the effect of synthesis conditions on the photocatalytic activity of the samples was studied. As a cocatalyst, platinum (1 wt. %) was deposited on the surface of the synthesized g‑C3N4 samples. The photocatalysts were characterized by X-ray phase analysis, diffuse reflectance UV-vis spectro-scopy in the UV and visible range, and low-temperature nitrogen adsorption. Photocatalytic activity was determined in the reaction of hydrogen evolution from an aqueous solution of triethanolamine (10 vol. %) under visible light irradiation (λ = 425 nm). The optimal conditions for the synthesis of the photocatalyst 1% Pt/g-C3N4, obtained by calcination of a mixture of melamine and urea (1 : 3), were found, using which the rate of H2 evolution was 5.0 mmol g–1 h–1 with an apparent quantum efficiency of 2.5%. The developed synthetic approach makes it possible to obtain highly active catalysts due to the formation of an intermediate supramolecular melamine-cyanuric acid complex during the synthesis, which, upon further heating, turns into g-C3N4, which is characterized by a high specific surface area exceeding 100 m2 g–1.

Mammalian odorant-binding proteins are prone to form amorphous aggregates and amyloid fibrils

Odorant-binding proteins are involved in perceiving smell by capturing odorants within the protein's β-barrel. On the example of bovine odorant-binding protein (bOBP), the structural organization of such proteins and their ability to bind ligands under various conditions in vitro were examined. We found a tendency of bOBP to form oligomers and small amorphous aggregates without disturbing the integrity of protein monomers at physiological conditions. Changes in environmental parameters (increased temperature and pH) favored the formation of larger and dense supramolecular complexes that significantly reduce the binding of ligands by bOBP. The ability of bOBP to form fibrillar aggregates with the properties of amyloids, including high cytotoxicity, was revealed at sample stirring (even at physiological temperature and pH), at medium acidification or pre-solubilization with hexafluoroisopropanol. Fibrillogenesis of bOBP was initiated by the dissociation of the protein's supramolecular complexes into monomers and the destabilization of the protein's β-barrels without a significant destruction of its native β-strands.

Nanoarchitectonics of supramolecular porphyrins based on a bis(porphyrin) cleft molecule

This account describes the construction of supramolecular constructs based on our bis(porphyrin) cleft molecule. The bis(porphyrin) cleft molecule was originally synthesized as a tweezer-shaped host molecule for planar guest molecules. A detailed study on the bis(porphyrin) cleft molecule revealed that the bis(porphyrin) cleft molecule forms two kinds of supramolecular structures. One structure is a self-complementary dimer obtained through intermolecular hydrogen bonding, and the other structure is a host-guest complex, in which the electron-rich cleft cavity accommodates electron-deficient guests through donor-acceptor interactions. Through the two supramolecular structures, two distinct supramolecular polymers can be formed through self-complementary dimerization or donor-acceptor host-guest complexation. The supramolecular chain structures were modified by judiciously using two distinct supramolecular structures. In the main text, several results, including the binding capability of our bis(porphyrin) cleft molecule, the formation of supramolecular porphyrin complexes, and the supramolecular polymerization behaviors of the bis(porphyrin) cleft molecule, are reported. In conclusion, the future direction of the bis(porphyrin) cleft molecule is provided.

Supramolecular complexes between Plinia cauliflora (DC.) Kausel extracts and β-cyclodextrin: Physicochemical characterization and antioxidant and anti-inflammatory properties

This work aims to investigate the supramolecular complexes formation between β-cyclodextrin (βCD) and compounds present in leaves (EEL) and branches (EEB) of Plinia cauliflora (DC.) Kausel Physicochemical characterization was carried out to investigate the formation of supramolecular complexes (EEL/βCD and EEB/βCD), such as, Fourier-transform infrared (FTIR) spectroscopy, thermal analysis (TGA/DTA), scanning electron microscopy (SEM), dynamic light scattering (DLS), Zeta potential (ZP), and electrical conductivity measurements. Antioxidant activity was evaluated by the 2,2-diphenyl-1-picrylhydrazyl, β-carotene/linoleic acid, and thiobarbituric acid reactive substance assays. Finally, anti-inflammatory activity was investigated by nitric oxide (NO) determination and evaluation of ear edema inhibition. FTIR spectroscopy and TGA/DTA confirmed the interactions in the solid-state, while ZP and DLS showed that the interaction between extracts and βCD caused differences in the hydrophobic nanoprecipitates. Moreover, the SEM micrograph of EEL/βCD and EEB/βCD indicates changing in particle morphology which confirms the interactions between extract compounds and βCD. EEL/βCD and EEB/βCD showed promising antioxidant activity for all assays performed. Furthermore, anti-inflammatory activity was confirmed by a significant reduction of NO (maximum of 90 and 85% for EEL/βCD and EEB/βCD, respectively) and inhibition of ear edema above 93% for both phytocomplexes. The development of a formulation based on the molecular encapsulation of extracts from P. cauliflora with βCD could be an effective, safe, and sustainable therapeutic alternative. Therefore, our samples showed the ability to reduce oxidative stress and inflammation, and serve as potential anti-inflammatory agents.

Oxygen-Rich Carbon Nitrides from an Eutectic Template Strategy Stabilize Ni, Fe Nanosites for Electrocatalytic Oxygen Evolution.

Functionalized porous carbons are central to various important applications such as energy storage and conversion. Here, a simple synthetic route to prepare oxygen-rich carbon nitrides (CNOs) decorated with stable Ni and Fe-nanosites is demonstrated. The CNOs are prepared via a salt templating method using ribose and adenine as precursors and CaCl2 ·2H2 O as a template. The formation of supramolecular eutectic complexes between CaCl2 ·2H2 O and ribose at relatively low temperatures facilitates the formation of a homogeneous starting mixture, promotes the condensation of ribose through the dehydrating effect of CaCl2 ·2H2 O to covalent frameworks, and finally generates homogeneous CNOs. As a specific of the recipe, the condensation of the precursors at higher temperatures and the removal of water promotes the recrystallization of CaCl2 (T < Tm = 772 °C), which then acts as a hard porogen. Due to salt catalysis, CNOs with oxygen and nitrogen contents as high as 12 and 20 wt%, respectively, can be obtained, while heteroatom content stayed about unchanged even at higher temperatures of synthesis, pointing to the extraordinarily high stability of the materials. After decorating Ni and Fe-nanosites onto the CNOs, the materials exhibit high activity and stability for electrochemical oxygen evolution reaction with an overpotential of 351mV.

Organometallic-Organic Hybrid Assemblies Featuring the Diantimony Complex [Cp2Mo2(CO)4(μ,η2-Sb2)], Ag(I) Ions and Ndonor Molecules as Building Blocks.

The reactions of the of the organometallic ligand complex [Cp2Mo2(CO)4(μ,η2-Sb2)] (C) with Ag[TEF] ([TEF]‾ = [Al{OC(CF3)3}4]‾) in the presence of a number of di- or polytopic N-donor molecules (1,6,7,12-tetraazaperylene (L1), 2,2'-bipyrimidine (L2), 4,4'-bipyridine (L3), trans-1,2-di(4-pyridyl)ethylene (L4)) and 1,3-di(4-pyridyl)propane (L5), were studied. These reactions lead, depending on the reaction stoichiometry and choice of linker, to the selective formation of dimeric or tetrameric supramolecular coordination complexes as well as 1D and 2D coordination polymers (CPs). The presented compounds are unique examples of supramolecular complexes incorporating both organometallic Sb-donor and organic N-donor molecules as ligands to stabilize metal ions. Moreover, one of the formed compounds, the CP [Ag4(η2:1-C)4(L4)4]n[TEF]4n, represents an exceptional 1D polymer incorporating both N- and Sb-donor ligands as connectors for metal ions.

Monitoring Protein Complexation with Polyphosphazene Polyelectrolyte Using Automated Dynamic Light Scattering Titration and Asymmetric Flow Field Flow Fractionation and Protein Recognition Immunoassay.

Polyphosphazenes represent a class of intrinsically flexible polyelectrolytes with potent immunoadjuvant activity, which is enabled through non-covalent self-assembly with antigenic proteins by charge complexation. The formation of supramolecular complexes between polyphosphazene adjuvant, poly[di(carboxylatophenoxy)phosphazene] (PCPP), and a model vaccine antigen, hen egg lysozyme, was studied under physiological conditions using automated dynamic light scattering titration, asymmetric flow field flow fractionation (AF4), enzyme-linked immunosorbent assay (ELISA), and fluorescent quenching methods. Three regimes of self-assembly were observed covering complexation of PCPP with lysozyme in the nano-scale range, multi-chain complexes, and larger aggregates with complexes characterized by a maximum loading of over six hundred protein molecules per PCPP chain and dissociation constant in the micromolar range (Kd = 7 × 10-6 mol/L). The antigenicity of PCPP bound lysozyme, when compared to equivalent lysozyme solutions, was largely retained for all complexes, but observed a dramatic reduction for heavily aggregated systems. Routes to control the complexation regimes with elevated NaCl or KCl salt concentrations indicate ion-specific effects, such that more smaller-size complexes are present at higher NaCl, counterintuitive with respect to PCPP solubility arguments. While the order of mixing shows a prominent effect at lower stoichiometries of mixing, higher NaCl salt reduces the effect all together.

Self-Assembled Charge-Transfer Chiral π-Materials: Stimuli-Responsive Circularly Polarized Luminescence and Chiroptical Photothermic Effects

Despite significant achievements in the field of chiroptical organic materials, the full utilization of both the excited state and ground state chiroptical properties in a single supramolecular system is still rarely disclosed. Here, we report that the rational combination of the charge-transfer (CT) interaction with the spacer effect and controlled protonation of π-histidine leads to chiroptical organic π-materials with both circularly polarized luminescence (CPL) and the supramolecular chirality-directed chiroptical photothermic effect. Three pyrene-conjugated histidine derivatives with varied acyl linkers (PyHis, PyC1His, and PyC3His) were designed to coassemble with electron-deficient 1,2,4,5-tetracyanobenzene (TCNB), leading to the formation of supramolecular CT complexes with intense orange to red CPL depending on the linker length. The linker length also affected the protonation-induced CPL responsiveness of the corresponding CT assemblies. Upon protonation of the histidine moiety, PyC3His/TCNB CT assemblies exhibited an inverted CPL signal, while PyHis/TCNB pairs gave quenched CPL due to the disassembly. The protonation-controlled PyC3His/TCNB CT assemblies at varied pH values showed different chiroptical photothermic effects (CPEs) for the same incident chiral light despite the molecular chirality of PyC3His remaining unchanged, supporting an interesting supramolecular chirality-directed photothermic effect.

A DNA damage–induced phosphorylation circuit enhances Mec1ATR Ddc2ATRIP recruitment to Replication Protein A

The cell cycle checkpoint kinase Mec1ATR and its integral partner Ddc2ATRIP are vital for the DNA damage and replication stress response. Mec1-Ddc2 "senses"single-stranded DNA (ssDNA) by being recruited to the ssDNA binding Replication Protein A (RPA) via Ddc2. In this study, we show that a DNA damage-induced phosphorylation circuit modulates checkpoint recruitment and function. We demonstrate that Ddc2-RPA interactions modulate the association between RPA and ssDNA and that Rfa1-phosphorylation aids in the further recruitment of Mec1-Ddc2. We also uncover an underappreciated role for Ddc2 phosphorylation that enhances its recruitment to RPA-ssDNA that is important for the DNA damage checkpoint in yeast. The crystal structure of a phosphorylated Ddc2 peptide in complex with its RPA interaction domain provides molecular details of how checkpoint recruitment is enhanced, which involves Zn2+. Using electron microscopy and structural modeling approaches, we propose that Mec1-Ddc2 complexes can form higher order assemblies with RPA when Ddc2 is phosphorylated. Together, our results provide insight into Mec1 recruitment and suggest that formation of supramolecular complexes of RPA and Mec1-Ddc2, modulated by phosphorylation, would allow for rapid clustering of damage foci to promote checkpoint signaling.

Phase separation of Hippo signalling complexes.

The Hippo pathway was originally discovered to control tissue growth in Drosophila and includes the Hippo kinase (Hpo; MST1/2 in mammals), scaffold protein Salvador (Sav; SAV1 in mammals) and the Warts kinase (Wts; LATS1/2 in mammals). The Hpo kinase is activated by binding to Crumbs-Expanded (Crb-Ex) and/or Merlin-Kibra (Mer-Kib) proteins at the apical domain of epithelial cells. Here we show that activation of Hpo also involves the formation of supramolecular complexes with properties of a biomolecular condensate, including concentration dependence andsensitivity to starvation, macromolecular crowding, or 1,6-hexanediol treatment. Overexpressing Ex or Kib induces formation of micron-scale Hpo condensates in the cytoplasm, rather than at the apical membrane. Several Hippo pathway components contain unstructured low-complexity domains and purified Hpo-Sav complexes undergo phase separation invitro. Formation of Hpo condensates is conserved in human cells. We propose that apical Hpo kinase activation occurs in phase separated "signalosomes" induced by clustering of upstream pathway components.

Comparative study of GBP recruitment on two cytosol-dwelling pathogens, Francisella novicida and Shigella flexneri highlights differences in GBP repertoire and in GBP1 motif requirements.

Guanylate-Binding Proteins are interferon-inducible GTPases that play a key role in cell autonomous responses against intracellular pathogens. Despite sharing high sequence similarity, subtle differences among GBPs translate into functional divergences that are still largely not understood. A key GBP feature is the formation of supramolecular GBP complexes on the bacterial surface. Such complexes are observed when GBP1 binds lipopolysaccharide (LPS) from Shigella and Salmonella and further recruits GBP2-4. Here, we compared GBP recruitment on two cytosol-dwelling pathogens, Francisella novicida and S. flexneri. Francisella novicida was coated by GBP1 and GBP2 and to a lower extent by GBP4 in human macrophages. Contrary to S. flexneri, F. novicida was not targeted by GBP3, a feature independent of T6SS effectors. Multiple GBP1 features were required to promote targeting to F. novicida while GBP1 targeting to S. flexneri was much more permissive to GBP1 mutagenesis suggesting that GBP1 has multiple domains that cooperate to recognize F. novicida atypical LPS. Altogether our results indicate that the repertoire of GBPs recruited onto specific bacteria is dictated by GBP-specific features and by specific bacterial factors that remain to be identified.

Domain motions, dimerization, and membrane interactions of the murine guanylate binding protein 2

Guanylate-binding proteins (GBPs) are a group of GTPases that are induced by interferon-gamma and are crucial components of cell-autonomous immunity against intracellular pathogens. Here, we examine murine GBP2 (mGBP2), which we have previously shown to be an essential effector protein for the control of Toxoplasma gondii replication, with its recruitment through the membrane of the parasitophorous vacuole and its involvement in the destruction of this membrane likely playing a role. The overall aim of our work is to provide a molecular-level understanding of the mutual influences of mGBP2 and the parasitophorous vacuole membrane. To this end, we performed lipid-binding assays which revealed that mGBP2 has a particular affinity for cardiolipin. This observation was confirmed by fluorescence microscopy using giant unilamellar vesicles of different lipid compositions. To obtain an understanding of the protein dynamics and how this is affected by GTP binding, mGBP2 dimerization, and membrane binding, assuming that each of these steps are relevant for the function of the protein, we carried out standard as well as replica exchange molecular dynamics simulations with an accumulated simulation time of more than 30 μs. The main findings from these simulations are that mGBP2 features a large-scale hinge motion in its M/E domain, which is present in each of the studied protein states. When bound to a cardiolipin-containing membrane, this hinge motion is particularly pronounced, leading to an up and down motion of the M/E domain on the membrane, which did not occur on a membrane without cardiolipin. Our prognosis is that this up and down motion has the potential to destroy the membrane following the formation of supramolecular mGBP2 complexes on the membrane surface.

Benzenesulfonyl thiazoloimines as unique multitargeting antibacterial agents towards Enterococcus faecalis

New efficient antimicrobial agents are urgently needed to combat invasive multidrug-resistant pathogens infections. Structurally unique benzenesulfonyl thiazoloimines (BSTIs) were exploited as novel potential antibacterial victors to confront terrific drug resistance. Some developed BSTIs exerted effectively antimicrobial efficacy against the tested strains. Notably, 2-pyridyl BSTI 14d exhibited good antibacterial activity against E. faecalis with MIC value of 1 μg/mL, which was superior to sulfathiazole and norfloxacin. The most active compound 14d not only showed rapid bactericidal properties and impeded E. faecalis biofilm formation to effectually relieve the development of drug resistance, but also performed low toxicity toward human red blood cells, human normal squamous epithelial cells and human non-neoplastic colon epithelial cells. Mechanistic investigation demonstrated that molecule 14d could exert efficient membrane destruction leading to the leakage of intracellular materials and metabolism inhibition, cause oxidative damage of E. faecalis through accumulation of excess reactive oxygen species and reduction of glutathione activity, and intercalate into DNA to hinder replication of DNA. Molecular docking indicated that the formation of 14d-dihydrofolate synthetase supramolecular complex could hinder the function of this enzyme. ADME analysis displayed that compound 14d possessed promising pharmacokinetic properties. These findings suggested that the newly developed benzenesulfonyl thiazoloimines with multitargeting antibacterial potential provided a new possibility for evading resistance.

Triplet dynamic nuclear polarization of pyruvate via supramolecular chemistry

Formation of supramolecular complexes with cyclodextrins improves the dispersibility of pentacene derivatives in polar matrices, resulting in the first triplet dynamic nuclear polarization of an important bioprobe, pyruvate.