Dye-sensitized intrazeolite photooxygenation of 4-substituted cyclohexenes. Remote substituent effects in regioselectivity and diastereoselectivity

The product distribution in the dye-sensitized photooxygenation of α-terpinyl acetate and terpinen-4-ol is quite similar in solution, however, by zeolite Y confinement, is substantially influenced by the position of the remote polar substituents relative to the reacting double bond. The intrazeolite results were rationalized in terms of Na⁺-substrate and Na⁺-singlet oxygen interactions.     

Development of a non-labeled immunosensor for the herbicide trifluralin via optical waveguide lightmode spectroscopic detection

A highly sensitive immunosensor using optical waveguide lightmode spectroscopy (OWLS) was developed for the detection of the herbicide trifluralin. OWLS as an in situ and label free method of detection, based on the measurement of the diffraction of a linearly polarized laser beam (He-Ne laser, 632.8 nm) on a diffraction grating in a thin waveguide layer (SiO₂-TiO₂), offered means to produce immunosensors utilizing immobilized antibodies raised against trifluralin allowing a non-competitive biosensor, or immobilized trifluralin conjugate allowing a competitive biosensor for this analyte. Immobilization of molecules sensitizing the sensor was undertaken on amino silanized waveguide surfaces in a two-step procedure using glutaraldehyde. Within the immobilized antibody (Ab) based immunosensor the signal measured was proportional to the trifluralin content in the samples, but the method allowed detection of trifluralin only above 100 ng ml⁻¹ due to the small molecular size of the antigen (Ag). In the immobilized antigen based immunosensor, a trifluralin-bovine serum albumin (BSA) conjugate was covalently linked to the waveguide surface. During measurements the standard solutions and samples were mixed in 1:1 ratio with antiserum, containing constant amounts of antibodies. The amount of free antibodies bound to the surface was inversely proportional to the trifluralin content of the solutions measured. The immobilized antigen based method allowed detection of trifluralin in the concentration range of 2×10⁻⁷ to 3×10⁻⁵ ng ml⁻¹. Results of trifluralin determinations were compared to those obtained in parallel enzyme-linked immunosorbent assay (ELISA) tests and in gas chromatorgraphic-mass spectrometric (GC-MS) analyses, and indicated an increase of six orders of magnitude in the limit of detection (LOD).     

Insulin complexes with PEGylated basic oligopeptides

Biodegradable oligolysine and oligoarginine-type homopeptides functionalized with PEG of two different molecular weights interact with insulin, at physiological pH, affording complexes studied by dynamic light scattering, ζ-potential, circular dichroism, FTIR spectroscopy, and isothermal titration calorimetry (ITC). High levels of insulin complexation efficiencies (>99.5%) were determined for all derivatives. FTIR spectra suggest that the positively charged homo-oligopeptide derivatives interact with B chain C-terminus of insulin leading to the formation of nanoparticles than can be traced even at low oligopeptide/insulin molar ratios. The ITC profiles are complex, displaying significant endothermic and exothermic contributions. Oligoarginine-type derivatives exhibit the strongest interactions, while PEGylation of either oligopeptide with the high molecular weight chains significantly affects the ITC profiles and leads to larger enthalpy changes. This may be attributed to PEG-induced aggregation of insulin due to the depletion attraction effect leading to the formation of stable nanocomplexes. Stabilization of complexed insulin against enzymatic degradation by trypsin and α-chymotrypsin is observed especially for the high molecular weight PEGylated arginine-based derivative. Insulin release rates in simulated intestinal fluid are controlled by the length of PEG chains and the presence of arginine end-groups. Released insulin retains its secondary structure as established by circular dichroism spectroscopy.     

Structural Features of Interacting Complementary Liposomes Promoting Formation of Multicompartment Structures

The structural features of complementary liposomes and factors favoring formation of multicompartment systems are investigated. Specifically, liposomal formulations consisting of PEGylated unilamellar liposomes with guanidinium moieties located at the distal end of polyethylene glycol (PEG) chains interact with complementary multilamellar liposomes bearing phosphate moieties. Furthermore, the number of PEG chains attached to the unilamellar interface of the liposomes is enhanced by incorporating PEGylated cholesterol in their bilayer. While molecular recognition of the liposomes is the driving force for initiating multicompartmentalization, it is the enhanced PEGylation at the liposomal interface that synergistically promotes fusion resulting in large and well‐formed multicompartment systems. A mechanism is proposed according to which initial adhesion of the liposomes, followed by reorganization of their membrane lipids, leads to giant bilayer aggregates incorporating large liposomes.     

Developing a Hazomalania voyronii Essential Oil Nanoemulsion for the Eco-Friendly Management of Tribolium confusum,Tribolium castaneum and Tenebrio molitor Larvae and Adults on Stored Wheat

Most insecticides commonly used in storage facilities are synthetic, an issue that generates concerns about food safety and public health. Therefore, the development of eco-friendly pest management tools is urgently needed. In the present study, a 6% (w/w) Hazomalania voyronii essential oil-based nanoemulsion (HvNE) was developed and evaluated for managing Tribolium confusum, T. castaneum, and Tenebrio molitor, as an eco-friendly wheat protectant. Larval and adult mortality was evaluated after 4, 8, and 16 h, and 1, 2, 3, 4, 5, 6, and 7 days, testing two HvNE concentrations (500 ppm and 1000 ppm). T. confusum and T. castaneum adults and T. molitor larvae were tolerant to both concentrations of the HvNE, reaching 13.0%, 18.7%, and 10.3% mortality, respectively, at 1000 ppm after 7 days of exposure. However, testing HvNE at 1000 ppm, the mortality of T. confusum and T. castaneum larvae and T. molitor adults 7 days post-exposure reached 92.1%, 97.4%, and 100.0%, respectively. Overall, the HvNE can be considered as an effective adulticide or larvicide, depending on the target species. Our results highlight the potential of H. voyronii essential oil for developing green nanoinsecticides to be used in real-world conditions against key stored-product pests.     

Statistical copolymers of N‐vinylpyrrolidone and 2‐(dimethylamino)ethyl methacrylate via RAFT: Monomer reactivity ratios,thermal properties,and kinetics of thermal decomposition

Statistical copolymers of N‐vinylpyrrolidone (NVP) with 2‐(dimethylamino)ethyl methacrylate (DMAEMA) were prepared by Reversible Addition‐Fragmentation chain Transfer Polymerization (RAFT), employing three different RAFT agents: [(O‐ethylxanthyl)methyl]benzene, [1‐(O‐ethylxanthyl)ethyl]benzene, and O‐ethyl S‐(phthalimidylmethyl) xanthate. The reactivity ratios were estimated using the Fineman‐Ross, inverted Fineman‐Ross, Kelen‐Tüdos, and extended Kelen‐Tüdos graphical methods, along with the computer program COPOINT. Structural parameters of the copolymers were obtained by calculating the dyad sequence fractions and the mean sequence length. All the methods indicate that the DMAEMA reactivity ratio is much greater than the one of NVP, thus, the statistical copolymers are in fact pseudo‐diblocks. The glass‐transition temperature (T_g) values of the copolymers were measured by Differential Scanning Calorimetry. Furthermore, a systematic and detailed investigation has been done, on the thermal degradation of the copolymers compared with the respective homopolymers, by Thermogravimetric Analysis, within the framework of the Ozawa‐Flynn‐Wall and Kissinger methodologies. Apparently, the thermal stability of the copolymers is influenced by both monomers and by the structure of the thiocarbonylthio end groups due to the RAFT agents. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3776–3787     

Crystal Structure of<Emphasis Type="SmallCaps"> D</Emphasis>(−)-amino-(4-hydroxyphenyl)acetate,the Zwitter Ionic Form of Biologically Active<Emphasis Type="SmallCaps"> D</Emphasis>(−)-4-hydroxyphenylglycine

Abstract  Crystals of D(−)-amino-(4-hydroxyphenyl)acetate were analyzed by single crystal X-ray diffraction. The compound crystallizes in the chiral space group, P2₁ (No. 4) with one molecule in the asymmetric unit and a = 5.0994(10) ?, b = 9.3169(19) ?, c = 8.6960(17) ?, β = 91.50(3)°. The intermolecular interactions in the crystal have been visualised by plotting the Hirshfeld surface of the molecule. Graphical Abstract  The extensive hydrogen bonding network in D(−)-amino-(4-hydroxyphenyl)acetate has been described and visualised by plotting its Hirshfeld surface.      

1H and 13C NMR investigation of 20‐hydroxyecdysone dioxolane derivatives,a novel group of MDR modulator agents

The synthesis, structure elucidation and the complete ¹H and ¹³C signal assignment of a series of dioxolane derivatives of 20‐hydroxyecdysone, synthesized as novel modulators of multidrug resistance, are presented. The structures and NMR signal assignment were established by comprehensive one‐dimensional and two‐dimensional NMR spectroscopy supported by mass spectrometry. Copyright © 2013 John Wiley & Sons, Ltd.     

A Study on the Direct Esterification of Monoalkylphosphates and Dialkylphosphates; The Conversion of the Latter Species to Trialkylphosphates by Alkylating Esterification

The microwave (MW)-assisted direct esterification of certain P-acids is a green method. Quantum chemical calculations revealed that the activation enthalpy (ΔH^#) for the exothermic monoalkylphosphate → dialkylphosphate transformation was on the average 156.6 kJ mol⁻¹, while ΔH^# for the dialkylphosphate → trialkylphosphate conversion was somewhat higher, 171.2 kJ mol⁻¹, and the energetics of the elemental steps of this esterification was less favorable. The direct monoesterification may be performed on MW irradiation in the presence of a suitable ionic liquid additive. However, the second step, with the less favorable energetics as a whole, could not be promoted by MWs. Hence, dialkylphosphates had to be converted to triesters by another method that was alkylation. In this way, it was also possible to synthesize triesters with different alkyl groups. Eventually a green, P-chloride free MW-promoted two-step method was elaborated for the synthesis of phosphate triesters.