Monthly Archives: March 2024

Tunable electrospun scaffolds of polyacrylonitrile loaded with carbon nanotubes: from synthesis to biological applications

Posted on by
Tunable electrospun scaffolds of polyacrylonitrile loaded with carbon nanotubes: from synthesis to biological applications

We present here a multi-technique analysis, at both supra-fibre and intra-fibre scale, of 3D scaffolds structures made of thermally treated PAN electrospun fibres. Our results show that we can propose biocompatible scaffolds presenting the same topology but with different elastic properties. Therefore, these 3D electrospun PAN fibres scaffolds are a precious tool for the in vitro study of many cell types.


Abstract

Growing cells in a biomimetic environment is critical for tissue engineering as well as for studying the cell biology underlying disease mechanisms. To this aim a range of 3D matrices have been developed, from hydrogels to decellularized matrices. They need to mimic the extracellular matrix to ensure the optimal growth and function of cells. Electrospinning has gained in popularity due to its capacity to individually tune chemistry and mechanical properties and as such influence cell attachment, differentiation or maturation. Polyacrylonitrile (PAN) derived electrospun fibres scaffolds have shown exciting potential due to reports of mechanical tunability and biocompatibility. Building on previous work we fabricate here a range of PAN fibre scaffolds with different concentrations of carbon nanotubes. We characterize them in-depth in respect to their structure, surface chemistry and mechanical properties, using scanning electron microscopy, image processing, ultramicrotomic transmission electron microscopy, x-ray nanotomography, infrared spectroscopy, atomic force microscopy and nanoindentation. Together the data demonstrate this approach to enable finetuning the mechanical properties, while keeping the structure and chemistry unaltered and hence offering ideal properties for comparative studies of the cellular mechanobiology. Finally, we confirm the biocompatibility of the scaffolds using primary rat cardiomyocytes, vascular smooth muscle (A7r5) and myoblast (C2C12) cell lines.

Photoisomerization and Light‐Controlled Antibacterial Activity of Fluoroquinolone‐Azoisoxazole Hybrids

Posted on by
Photoisomerization and Light-Controlled Antibacterial Activity of Fluoroquinolone-Azoisoxazole Hybrids

Photoswitchable antibiotic hybrids: Potentials for creating phtoswitchable antibiotic hybrids using norfloxacin/ciproflocacin and azoisoxazole (photoswitch) pharmacophores have been explored. Against Gram-positive pathogens, all hybrids in their trans states exhibited antibacterial activity comparable to the parent drugs. Notably, the potency of the irradiated state (cis isomer) of a hybrid was found to be 2-fold lower than the nonirradiated state (trans isomer).


Abstract

Photopharmacology holds a huge untapped potential to locally treat diseases involving photoswitchable drugs via the elimination of drugs’ off-target effects. The growth of this field has created a pressing demand to develop such light-active drugs. We explored the potential for creating photoswitchable antibiotic hybrids by attaching pharmacophores norfloxacin/ciprofloxacin and azoisoxazole (photoswitch). All compounds exhibited a moderate to a high degree of bidirectional photoisomerization, long thermal cis half-lives, and impressive photoresistance. Gram-negative pathogens were found to be insensitive to these hybrids, while against Gram-positive pathogens, all hybrids in their trans states exhibited antibacterial activity that is comparable to that of the parent drugs. Notably, the toxicity of the irradiated hybrid 6 was found to be 2-fold lower than the nonirradiated trans isomer, indicating that the pre-inactivated cis-enriched drug can be employed for the site-specific treatment of bacterial infection using light, which could potentially eliminate the unwanted exposure of toxic antibiotics to both beneficial and untargeted harmful microbes in our body. Molecular docking revealed different binding affinity of the cis and trans isomers with the topoisomerase IV enzyme, due to their different shapes.

Ether Bond Cleavage of a Phenylcoumaran β‐5 Lignin Model Compound and Polymeric Lignin Catalysed by a LigE‐type Etherase from Agrobacterium sp.

Posted on by
Ether Bond Cleavage of a Phenylcoumaran β-5 Lignin Model Compound and Polymeric Lignin Catalysed by a LigE-type Etherase from Agrobacterium sp.

A LigE-type beta-etherase enzyme from lignin-degrading Agrobacterium sp. Is found to convert a phenylcoumaran β-5 lignin dimer into a cis-stilbene, alkene and ketone products, via reaction of glutathione at the α position, the first example of an etherase enzyme attacking the α position of a β-5 unit.


Abstract

A LigE-type beta-etherase enzyme from lignin-degrading Agrobacterium sp. has been identified, which assists degradation of polymeric lignins. Testing against lignin dimer model compounds revealed that it does not catalyse the previously reported reaction of Sphingobium SYK-6 LigE, but instead shows activity for a β-5 phenylcoumaran lignin dimer. The reaction products did not contain glutathione, indicating a catalytic role for reduced glutathione in this enzyme. Three reaction products were identified: the major product was a cis-stilbene arising from C−C fragmentation involving loss of formaldehyde; two minor products were an alkene arising from elimination of glutathione, and an oxidised ketone, proposed to arise from reaction of an intermediate with molecular oxygen. Testing of the recombinant enzyme against a soda lignin revealed the formation of new signals by two-dimensional NMR analysis, whose chemical shifts are consistent with the formation of a stilbene unit in polymeric lignin.

Strategies to Improve the Activity of Silver–loaded Calcium Titanate Crystal Photocatalyst for Photocatalytic Reduction of Carbon Dioxide with Water

Posted on by
Strategies to Improve the Activity of Silver–loaded Calcium Titanate Crystal Photocatalyst for Photocatalytic Reduction of Carbon Dioxide with Water

Several strategies to improve the Ag/CaTiO3 (Ag/CTO) photocatalysts for selective photocatalytic CO2 reduction with water to form CO are shortly reviewed, such as fabrication of well–structured fine crystal photocatalysts with moderate size, modification of Ag NPs cocatalyst with size control or additives, enhancement of surface CO2 adsorption, development of dual cocatalyst, and improvement of photoabsorption.


Abstract

The rapid increase of carbon dioxide (CO2) in the atmosphere has sparked a global enthusiasm for carbon recycling. Photocatalytic CO2 reduction with water into carbon–containing products has attracted much attention since it can convert solar energy to the chemical potential of the products and CO2 to valuable compounds at the same time. One of the main products in the photocatalytic reaction system is carbon monoxide (CO), a useful compound for the one-carbon chemistry and related ones. The current shortage of this system is the low production efficiency, demanding us to improve the activity of the photocatalyst. In this perspective article, by taking a calcium titanate (CaTiO3, CTO) photocatalyst with silver cocatalyst (Ag/CTO) and so on as examples that can promote the selective photocatalytic CO2 reduction with water, we shortly review some strategies to improve the photocatalytic activity such as fabrication of well–structured crystal photocatalysts, development of the surface property and cocatalyst, improvement of surface CO2 adsorption, and improvement of photoabsorption. These concepts will be widely applied and contribute to further development of photocatalytic systems.

Alkaline Earth Metal Aluminate Support for Selective Oxidative Coupling of Methane

Posted on by
Alkaline Earth Metal Aluminate Support for Selective Oxidative Coupling of Methane

Utilizing MgAl2O4 as a support for Mn-doped K2WO4 catalysts to maintain high surface area under the harsh reaction conditions of OCM, to get high CH4 conversion rata, compared with commonly used SiO2 support.


Abstract

The oxidative coupling of methane (OCM) provides a direct route to transform methane into higher value products. The alkali metal tungstate catalysts have demonstrated high selectivity towards C2 products, ethane (C2H6) and ethylene (C2H4). However, the severe sintering of the SiO2 support limits the reaction rate requiring active site densification to compete with unselective gas phase combustion reaction especially at high pressure operations. This work studies alkaline earth metal oxides as supports for K2WO4 catalysts to maintain comparatively high surface area under OCM conditions. Among Mg, Ca, and Sr aluminates, the K2WO4/MgAl2O4 catalyst exhibited the highest C2 yields. To achieve high C2 product selectivity, a relatively large loading of K2WO4 (20 wt %) was required likely to cover the unselective surface sites of MgAl2O4 support. The catalyst further showed high levels of stability when utilized at high pressures (0.9 MPa) for over 60 h, without any change in product selectivity. The Mn/K2WO4/MgAl2O4 showed multifold higher CH4 conversion rate, compared with the SiO2 counterpart. The findings showcase the potential of the MgAl2O4 support as a viable candidate for alkali metal tungstate catalysts for OCM, which introduces high density of active components in given volume in the reactor, which induces high contribution of the catalyst relative to the pure gas phase oxidation.

Ruthenium Complexes with a Tridentate Anionic Bisfluoroalkoxy‐Carbene Ligand – Valuable Latent Olefin Metathesis Catalysts for Polymerisation Reactions

Posted on by
Ruthenium Complexes with a Tridentate Anionic Bisfluoroalkoxy-Carbene Ligand – Valuable Latent Olefin Metathesis Catalysts for Polymerisation Reactions

Synthesis of latent Grubbs-type ruthenium complex bearing a tridentate anionic bisfluoroalkoxy-carbene and unexpected formation of new complex formed upon coordination of the substrate and occurrence of only first olefin metathesis step; triggering its activity in olefin metathesis reactions by addition of HCl.


Abstract

A Grubbs-type ruthenium complex bearing a tridentate anionic bisfluoroalkoxy-carbene was synthesised and fully characterised. Under standard conditions, it proved to be inactive in olefin metathesis reactions, but the addition of HCl triggers its activity and allows the synthesis of a series of cyclic olefins and ethers as well as a stereoregular polynorbornene with an unexpectedly high content of trans-configured double bonds, as found in commercially available polynorbornene (Norsorex®). Detailed structural studies and DFT calculations showed that the complex enters the catalytic cycle, but instead of performing a full turnover, it is caught as a stable intermediate that does not undergo further reactions. The addition of HCl causes dissociation of the fluoroalkoxy units, resulting in a compound that behaves similarly to standard Grubbs-type complexes. To further understand this phenomenon, the corresponding Hoveyda-Grubbs complex was also obtained and studied in detail; due to the absence of the phosphine ligand, its behaviour was different from that of its Grubbs-type counterpart.

Investigations on Water‐Soluble Copper Complexes with the Sterically Demanding Triazacyclononane Derivative (tBu)2(nPrSO3)Htacn

Posted on by
Investigations on Water-Soluble Copper Complexes with the Sterically Demanding Triazacyclononane Derivative (tBu)2(nPrSO3)Htacn

Copper(I) and copper (II) complexes with (tBu)2(nPrSO3)Htacn were synthesized and characterized. Focused on the reaction of Cu(II) complexes with H2O2 kinetic investigations in protic solvents were performed.


Abstract

Related to environmentally friendly productions in the industry, the synthesis of catalysts with designed ligands for solubility in protic solvents and reactivity under mild conditions becomes important. Thus, copper complexes were synthesized with a ligand system that was designed for better solubility in protic solvents. The reactivity of copper complexes with hydrogen peroxide under ambient conditions was investigated in water and in methanol. The formation of a μ-η2 : η2-peroxide copper complex with a stability of a few minutes was observed in contrast to most related complexes reported in the literature. A kinetic analysis was performed, leading to activation parameters of ΔH ≠: 66±4 kJ ⋅ mol−1 and ΔS ≠: −5±12 J ⋅ K−1 ⋅ mol−1 (in water), a strong indication of an interchange mechanism.

Modulating the Acceptor Preference of His‐C‐Geranyltransferase LimF

Posted on by
Modulating the Acceptor Preference of His-C-Geranyltransferase LimF


Abstract

Lipidation stands as a pivotal strategy for enhancing the metabolic stability of target peptides. Prenyltransferases in cyanobactin biosynthesis have garnered significant attention as potential peptide lipidation biocatalysts because of their exceptional regio- and chemoselectivity. However, these enzymes often exhibit a biased preference for certain acceptor substrates, requiring specific amino acids adjacent to the modifying residue. In this study, we demonstrate the structure-guided engineering of LimF, a His-C-geranyltransferase, to broaden its peptide substrate tolerance. By altering key residues in the peptide-binding pocket, we created a LimF variant capable of modifying sequence motifs previously inaccessible to the wildtype enzyme. The variant successfully modified some previously unfavored sequence motifs in artificial peptide substrates and bioactive peptide agents, validating the engineered substrate scope. With the discovery of novel peptide prenyltransferases, this approach would lead to a more comprehensive toolbox of peptide prenylation biocatalysts.

Cover Feature: High Inhibition for a CoII Tetrazole Bi‐pyrazole Dinuclear Complex against Fusarium Oxysporum f. sp. Albedinis (Eur. J. Inorg. Chem. 11/2024)

Posted on by
Cover Feature: High Inhibition for a CoII Tetrazole Bi-pyrazole Dinuclear Complex against Fusarium Oxysporum f. sp. Albedinis (Eur. J. Inorg. Chem. 11/2024)

The Cover Feature illustrates how a newly obtained dinuclear cobalt complex bearing a novel bipyrazole and tetrazole-based ligand 1′-((1H-tetrazol-5-yl)methyl)-3,5,5′-trimethyl-1′H-1,3′-bipyrazole fights off the fungus Fusarium oxysporum f. sp. Albedinis, represented in blue, which is the main cause of the Bayoud disease responsible for great damage to the palm trees in North Africa. In a fictional boxing match, the dinuclear cobalt metal complex is knocking out the fungi with ease, symbolising the treatment of sick plants, thus yielding healthy palm trees ready to be harvested for dates. The artwork for the cover was done by Olivera Cvetković. More information can be found in the Research Article by Y. Garcia and co-workers.


Front Cover: Rare Earth 2‐Methyl‐3‐furoate Complexes: Effect of Steric Hindrance on Corrosion Inhibitor Properties (Eur. J. Inorg. Chem. 11/2024)

Posted on by
Front Cover: Rare Earth 2-Methyl-3-furoate Complexes: Effect of Steric Hindrance on Corrosion Inhibitor Properties (Eur. J. Inorg. Chem. 11/2024)

The Front Cover shows our rare earth corrosion inhibitor work. Corrosion is a significant burden to infrastructure, including bridges, and we have shown that incorporation of steric bulk about heteroatoms on the ligands bound to rare earth atoms (right figure) affects the ability to inhibit corrosion, compared to when we have open access to these heteroatoms (left figure). The artwork for the cover was done by Vidushi Vithana. More information can be found in the Research Article by P. C. Junk and co-workers.