Ni(II)‐NTA Modified Poly(ethylene imine) Glycopolymers: Physicochemical Properties and First In Vitro Study of Polyplexes Formed with HIV‐Derived Peptides

Alternative delivery entities are desirable in immunotherapies in which polyplexes are widely formed by electrostatic interactions to induce cellular uptake processes for bioactive molecules. In our study, biocompatible Ni(II)‐nitrilo(triacetic acid)‐modified poly(ethylene imine)‐maltose ( Ni‐NTA‐DG ) is realized and evaluated as complexation agent against His‐tagged peptides using fluorescence polarization and dynamic light scattering. The polyplexes are stable until a pH of 6.5–6.0, and also up to 50 mM of imidazole. A first uptake approach shows that polyplexes lead to an increase in peptide uptake in monocyte‐derived immature dendritic cells. In summary, Ni‐NTA‐DG represents a promising (delivery) platform for forthcoming in vitro applications.

     

Insights on keto-hydroperoxide formation from O2 addition to the beta-tetrahydrofuran radical

Cyclic ethers provide an interesting case study of low-temperature oxidation chemistry, especially in relevance to biofuels. A recent experimental study (Hansen et al., 2019) revealed new questions regarding the low-temperature oxidation mechanism of tetrahydrofuran (THF) concerning the formation of keto-hydroperoxides. In particular, keto-hydroperoxides originating from the THF-β radical were not captured accurately by current literature models, motivating this work to calculate the energetics of the first and second O₂-addition pathways for THF radicals. Electronic structure calculations at the CCSD(T)/cc-pV∞Z//M06-2X/cc-pVTZ level of theory were used to generate potential energy surfaces for the α-C and β-C THF radicals and subsequent pathways to the formation of the keto-hydroperoxide isomers. These are the first theoretical calculations of the second O₂-addition radical pathways for the THF-β radical. Results from the theorical work provided further insight into the low-temperature oxidation of THF. This included identifying the pathways most likely to form the keto-hydroperoxide isomers observed in prior experimental work; and detecting that the shortcomings in prior models are likely due to uncertainties in R + THF abstraction reaction rates. These conclusions will motivate future work for accurate THF kinetic model development.     

Strain-Induced Nucleophilic Ring Opening of Donor–Acceptor Cyclopropenes for Synthesis of Monosubstituted Succinic Acid Derivatives

1,2,3-Trisubstituted donor–acceptor cyclopropenes (DACPs) generated in situ from enoldiazo compounds react with nucleophiles to form α-substituted succinic acid derivatives in high yields. Initial dirhodium(II) carboxylate catalysis rapidly converts enoldiazo-acetates or -acetamides to DACPs that undergo catalyst-free Favorskii ring opening with amines, and also with anilines, alcohols, and thiols, when facilitated by catalytic amounts of 4-dimethylaminopyridine (DMAP). This methodology provides easy access to mixed esters and amides of monosubstituted succinic acids, including derivatives of naturally occurring compounds. It also affords dihydrazide, dihydroxamic acid, and diamide derivatives, as well as α-substituted tetrahydropyridazine-3,6-diones in high yields. Attempts to generate optically enriched DACPs were not successful because their populations having the R and S configurations formed with a chiral dirhodium catalyst are quite similar, and the loss of enantiocontrol likely originates from the DACP ring forming step which is reversible with its intermediate metal carbene.     

Highly Sensitive Impedimetric Biosensor Based on Thermolysin Immobilized on a GCE Modified with AuNP-decorated Graphene for the Detection of Ochratoxin A

The fabrication of a thermolysin-based biosensor capable of detecting ochratoxin A (OTA) from food samples is described. The electrochemical deposition of calcium cross-linked cellulose film (CCLC) and gold nanoparticles (AuNPs) on graphene (GR) for modification of a glassy carbon electrode (GCE) is the first step. Then the thermolysin (TLN) enzyme in a polyvinyl alcohol (PVA)/polyethylenimine (PEI) matrix is immobilized. The impedimetric biosensor response is linear from 0.2 nM to 100 nM with a detection limit of 0.2 nM. The obtained stable and reproducible biosensor is then applied for the detection of OTA in spiked extracts from coffee beans.     

Ruthenium olefin metathesis catalysts with modified styrene ethers: influence of steric and electronic effects

A series of olefin metathesis catalysts with modified isopropoxybenzylidene ligands were synthesised, and the effects of ligands on the rate of metathesis investigated. Increased steric hinderance ortho to the isopropoxy group enhanced reaction rates. In the case of N-heterocyclic carbene complexes, decreasing electron density at both the chelating oxygen atom and the RuC bond accelerated reaction rates appreciably. Catalysts containing a tricyclohexylphosphane ligand, followed the same trend with regard to benzylidene electrophilicity, while higher electron density at oxygen enhanced reaction rates.     

Copper(II) complexes of 2-formyl-, 2-acetyl- and 2-benzoyl-pyridine N(4)-phenyl-, N(4)-o-methoxyphenyl-, N(4)-p-methoxy-phenyl- and N(4)-p-nitrophenylthiosemicarbazones

Summary Cu^II complexes of 2-formyl-, 2-acetyl- and 2-benzoylpyridine N(4)-phenyl-, N(4)-o-methoxyphenyl-, N(4)-p-methoxyphenyl- and N(4)-p-nitrophenyltniosemicarbazones, coordinated either as neutral or monoanionic ligands, have been prepared and characterized. I.r., electronic and e.p.r. spectra of the complexes, as well as ¹H-and ¹³C-n.m.r. spectra of the thiosemicarbazones, have been obtained. Both the thiosemicarbazones and their complexes show either modest or no growth inhibitory activity against Paecilomyces variotii. However, some of these thiosemicarbazones possess significant activity against a number of tumour cell strains.     

Human resource allocation applications of stochastic maintenance models with super‐reserve backups

This article deals with stochastic maintenance models that include a repair facility and three types of ‘unreliable’ machines: the main facility of working and reserve machines, and an auxiliary facility of ‘super‐reserve’ machines. Working machines breakdown exponentially and are immediately replaced by available reserve machines. Defective machines line up for repair and refurbished machines are returned to the main facility. This system falls into the category of closed queues with hot standbys and has more options than the basic model. If the main facility is restored to its original quantity and the repair facility leaves on routine maintenance, all reserve machines are temporarily blocked and renewals come from the super‐reserve group until the latter is exhausted. Explicit formulas obtained demonstrate a relatively effortless use of functionals of the main stochastic characteristics, and optimization of their objective function. Human resource applications are included as optimization examples. Copyright © 2005 John Wiley & Sons, Ltd.