Synthesis and cytotoxic evaluation of heterocyclic compounds by vinylic substitution of ketene dithioacetals.

N-heterocyclic compounds are important molecular scaffolds in the search for new drugs, since most drugs contain heterocyclic moieties in their molecular structure, and some of these classes of heterocycles are able to provide ligands for two or more biological targets. Ketene dithioacetals are important building blocks in organic synthesis and are widely used in the synthesis of N-heterocyclic compounds. In this work, we used double vinylic substitution reactions on ketene dithioacetals to synthesize a small library of heterocyclic derivatives and evaluated their cytotoxic activity in breast and ovarian cancer cells, identifying two benzoxazoles with good potency and selectivity. In silico predictions indicate that the two most active derivatives exhibit physicochemical properties within the range of drug-like compounds and showed potential to interact with HDAC8 and ERK1 cancer-related targets.

Development of the headspace gas chromatography-tandem mass spectrometry method for ethylene oxide and ethylene chlorohydrin residue in medical devices.

RATIONALE: Ethylene oxide (EO) sterilization is commonly employed for the sterilization of medical devices and has a very high market share. However, EO and its metabolite ethylene chlorohydrin (ECH) are toxic to humans. In compliance with the classification and residue limits of medical devices defined by ISO 10993-7, our study established two extraction methods for the testing of EO and ECH. METHODS: The first method involves simulated-use extraction using water as the extraction solvent. While the second, exhaustive extraction, directly extracts sample through headspace sampling analysis. Gas chromatography-tandem mass spectrometry in multiple reaction monitoring mode was utilized, requiring only 16 min. Then, the developed method was applied to assess 10 commercially available medical devices sterilized by EO. RESULTS: In simulated-use extraction, calibration curves were evaluated in the range of 1-100 and 5-500 µg for EO and ECH, respectively (r > 0.999). Inter-day recoveries ranged from 85.0% to 95.2% and from 94.8% to 102.4%. In exhaustive extraction, calibration curves spanned 0.5-50 and 2-200 µg for EO and ECH, respectively (r > 0.999). Inter-day recoveries ranged from 101.6% to 102.1% for EO and from 98.1% to 102.2% for ECH. After analysis of the 10 commercially available medical devices, two cotton swabs were found to have ECH of 35.1 and 28.4 µg per device, and four medical devices were found to have EO with concentration below the limit of quantification. Meanwhile, we found that the EO internal standard (propylene oxide) recommended by ISO 10993-7 had interference problems with other similar substances and was not suitable as an internal standard for EO. CONCLUSIONS: This study offers a sensitive and straightforward analytical approach to EO and ECH residues in a variety of medical devices. In addition, the results show that the EO or ECH content of these types of medical devices in our study falls below the regulatory limits, therefore instilling confidence among consumers regarding their safe use.

A new photoionization-induced substitution reaction chemical ionization time-of-flight mass spectrometry for highly sensitive detection of trace exhaled ethylene.

Highly sensitive and rapid detection of ethylene, the smallest alkene of great significance in human physiological metabolism remains a great challenge. In this study, we developed a new photoionization-induced substitution reaction chemical ionization time-of-flight mass spectrometry (PSCI-TOFMS) for trace exhaled ethylene detection. An intriguing ionization phenomenon involving a substitution reaction between the CH2Br2+ reactant ion and ethylene molecule was discovered and studied for the first time. The formation of readily identifiable [CH2Br·C2H4]+ product ion greatly enhanced the ionization efficiency of ethylene, which led to approximately 800-fold improvement of signal intensity over that in single photon ionization mode. The CH2Br2+ reactant ion intensity and ion-molecule reaction time were optimized, and a Nafion tube was employed to eliminate the influence of humidity on the ionization of ethylene. Consequently, a limit of detection (LOD) as low as 0.1 ppbv for ethylene was attained within 30 s at 100 % relative humidity. The application of PSCI-TOFMS on the rapid detection of trace amounts of exhaled ethylene from healthy smoker and non-smoker volunteers demonstrated the satisfactory performance and potential of this system for trace ethylene measurement in clinical diagnosis, atmospheric measurement, and process monitoring.

On-site sensing for aflatoxicosis poisoning via ultraviolet excitable aptasensor based on fluorinated ethylene propylene strip: a promising forensic tool.

The environmental contamination by extremophile Aspergillus species, i.e., Aflatoxin B1, is hardly controllable in Southeast Asia and Sub-Saharan Africa, which lack handling resources and controlled storage facilities. Acute aflatoxicosis poisoning from aflatoxin-prone dietary staples could cause acute hepatic necrosis, acute liver failure, and death. Here, as the cheaper, more straightforward, and facile on-site diagnostic kit is needed, we report an ultraviolet-excitable optical aptasensor based on a fluorinated ethylene propylene film strip. Molecular dynamics on the aptamer.AFB1 complex revealed that the AFB1 to the aptamer increases the overall structural stability, suggesting that the aptamer design is suitable for the intended application. Under various influencing factors, the proposed label-free strategy offers a fast 20-min on-site fabrication simplicity and 19-day shelf-life. The one-pot incubation provides an alternative to catalytic detection and exhibited 4 times reusability. The recovery of crude brown sugar, processed peanuts, and long-grain rice were 102.74 ± 0.41 (n = 3), 86.90 ± 3.38 (n = 3), and 98.50 ± 0.42 (n = 3), comparable to High-Performance Liquid Chromatography-Photodiode Array Detector results. This study is novel owing to the peculiar UV-active spectrum fingerprint and the convenient use of hydrophobic film strips that could promote breakthrough innovations and new frontiers for on-site/forensic detection of environmental pollutants.

Exploration and Development of Nitrone Chemistry.

Nitrones are widely used as 1,3-dipoles in organic synthesis, but control of their reactions is not always easy. This review outlines our efforts to make the reactions of nitrones more predictable and easier to use. These efforts can be categorized into (1) 1,3-nucleophilic addition reaction of ketene silyl acetals to nitrones, (2) geometry-controlled cycloaddition of C-alkoxycarbonyl nitrones, (3) stereo-controlled cycloaddition using double asymmetric induction, and (4) generation of nitrones by N-selective modification of oximes.

Effect of lignin on the structure-property behavior of metal-coordinated and chemically crosslinked ethylene-propylene-diene-monomer composites.

The efficient development and utilization of green biomass-based macromolecule engineering materials are essential for the sustainable development of human civilization. In this study, lignin-based ethylene-propylene-diene-monomer (EPDM) composites with excellent mechanical performance were fabricated using a simple method. The effects of water-insoluble enzymatically hydrolyzed lignin (EL) and alkali lignin (KL) on the mechanical performance of the composites were investigated separately. The results showed that the tensile strength of EPDM reinforced with KL and EL increased to 24.5 MPa and 22.1 MPa, respectively, surpassing that of the carbon black (CB)-reinforced EPDM. After 72 h of thermo-oxidative aging, the retention rates of the tensile strength and elongation at break in the lignin-reinforced EPDM were much better than those formed with pure CB, indicating that lignin significantly improved the thermo-oxidative aging resistance of the composites. In summary, the Zn2+ coordination bonds formed between the interface of EPDM and lignin in lignin/CB/EPDM ternary composites effectively improved the mechanical performance and aging resistance of the composites. This study has significant implications for enhancing the utilization of lignin and green functional polymer materials.

Advanced ethylene-absorbing and cushioning depending on the 3D porous-structured fruit packaging: Toward polyurethane foam manipulation using zein and soybean oil polyol substrates.

Fruits are essential sources of nutrients in our daily diet; however, their spoilage is often intensified by mechanical damage and the ethylene phytohormone, resulting in significant economic losses and exacerbating hunger issues. To address these challenges, this study presented a straightforward in situ synthesis protocol for producing Z/SOPPU foam, a 3D porous-structured fruit packaging. This innovative packaging material offered advanced ethylene-adsorbing and cushioning capabilities achieved through stirring, heating, and standing treatments. The results demonstrated that the Z/SOPPU foam, with its porous structure, served as an excellent packaging material for fruits, maintaining the intact appearance of tomatoes even after being thrown 72 times from a height of 1.5 m. Additionally, it exhibited desirable hydrophobicity (contact angle of 114.31 ± 0.82°), degradability (2.73 ± 0.88 % per 4 weeks), and efficient ethylene adsorption (adsorption rate of 13.2 ± 1.7 mg/m3/h). These remarkable characteristics could be attributed to the unique 3D micron-porous configuration, consisting of soybean oil polyol polyurethane foam for mechanical strain cushioning and zein for enhanced ethylene adsorption efficiency. Overall, this research offers an effective and original approach to the rational design and fabrication of advanced bio-based fruit packaging.

Relationship between skin greasiness and cuticular wax in harvested "Hongro" apples.

We investigated the ripening and skin greasiness of "Hongro" apples during storage at 20 °C. Postharvest treatment using 100 µLL-1 ethylene accelerated ripening and increased greasiness, whereas treatment using 1 µLL-1 1-methylcyclopropene delayed ripening and reduced greasiness. Scanning electron microscopy showed changes in cuticular wax structure linked to greasiness. Metabolic analysis identified specific metabolites related to greasiness, which varied upon postharvest treatment. Greasiness was positively associated with ethylene production and butyl-9,12-octadecadienoate content. Random forest modeling predicted greasiness levels with high accuracy, with root mean square error values of 0.322 and 0.362 for training and validation datasets, respectively. These findings illuminate the complex interplay between postharvest treatment, apple ripening, wax composition, and skin greasiness. The application of predictive models exemplifies the potential for technology-driven approaches in agriculture and aids in the development of postharvest strategies to control greasiness and maintain fruit quality.

Dual site reactivity of indole-3-Schiff bases with S/Se/Cl substituted ketenes for stereoselective C-4 substituted indole-ß-lactams, biological evaluations, magic chloro effect and molecular docking studies.

A convenient methodology for C-4 indole-ß-lactam hybrids with chloro, sulphur and seleno substitutions through dual site reactivity of indole-3-Schiff bases towards ketenes has been developed. The reaction proceeded in a stereospecific manner with the exclusive formation of trans-ß-lactams assigned with respect to C3-H and C4-H. The synthesized novel ß-lactams have been characterized with the help of elemental analysis (CHNS) and spectroscopic techniques viz.1H NMR, 13C NMR, DEPT 135, HSQC and IR. The trans configuration was further estabilished based on X-ray crystallographic data. Examination of antibacterial properties unveiled that only derivatives 5a and 5b, featuring chloro substitution, exhibited potent activities, underscoring the emergence of the recently coined term "magic chloro effect". Molecular docking analysis provided additional support for the observed in vitro antibacterial activities of compounds 5a-b.

Insights into the hydrolysis/alcoholysis/ammonolysis mechanisms of ethylene naphthalate dimer using density functional theory (DFT) method.

Hydrolysis, alcoholysis and ammonolysis are viable routes for the efficient degradation and recycling of polyethylene naphthalate (PEN) plastic waste. Various possible hydrolysis/alcoholysis/ammonolysis reaction pathways for the degradation mechanism of the ethylene naphthalate dimer were investigated using the density functional theory (DFT) B3P86/6-31++G(d,p). To determine the thermodynamic and kinetic parameters, geometric structure optimization and frequency calculation were performed on a range of intermediates, transition states, and products associated with the reaction. The calculation results show that the highest energy barrier of the main element reaction step in hydrolysis is about 169.0 kJ/mol, the lowest is about 151.0 kJ/mol for ammonolysis, and the second is about 155.0 kJ/mol for alcoholysis. The main hydrolysis products of the ethylene naphthalate dimer are 2,6-naphthalenedicarboxylic acid and ethylene glycol; the main products of alcoholysis are dimethyl naphthalene-2,6-dicarboxylate and ethylene glycol, and the main products of ammonolysis are naphthalene-2,6-dicarboxamide and ethylene glycol. Furthermore, in the process of ethylene naphthalate dimer hydrolysis/alcoholysis/ammonolysis, the decomposition reaction in the NH3 atmosphere is better than that in methanol, and the reaction in CH3OH is better than that in the H2O molecular environment, and the increase in reaction temperature can increase its spontaneity. Our study presents the molecular mechanism of PEN hydrolysis/alcoholysis/ammonolysis and provides a reference for studying the degradation of other plastic wastes.

Recent Advances on Diarylethene-Based Photoswitching Materials: Applications in Bioimaging, Controlled Singlet Oxygen Generation for Photodynamic Therapy and Catalysis.

Photoswitching materials have emerged as a promising class of compounds that possess manifold interesting properties rendering their widespread use from photoswitches, regulators to optoelectronic devices, security technologies and biochemical assays. Diarylethenes (DAE) constitute one such category of photoswitchable compounds, where the key features of stability, photoisomerization wavelengths, quantum yield and variability in the photoisomers significantly depend on their derivatization. The last decade has witnessed a surge in the engagement of DAEs in different areas of chemical and biological sciences, like biomarkers, controlled generation of singlet oxygen, photo-dynamic therapy, chemosensing, catalysis, etc. In all the cases, the photoswitchability of DAE is the principal regulating factor along with its emission properties according to the appended groups. Previous reviews on applications of DAE-based systems did not predominantly cover all the aspects of biological and industrial implementations. They have covered only one field of application either in the biological science or in the synthetic aspect or photochromic aspects only. This review is a coalition of all those aspects in last six years. Here the variation of properties of the DAE systems with respect to structural diversifications have been discussed in detail along with their potential applications in bioimaging of cells, regulating singlet oxygen generation for photodynamic therapy and catalysis of organic reactions, and their future prospects. A tabular presentation of the photophysical properties of DAE derivatives adds to the basic understanding of this subject at a glance. We hope that this cumulative collection of contemporary research on DAE, as presented in this review, will enhance the knowledge of the readers about synthetic design anticipating their properties well in advance, and will certainly motivate researchers to generate new DAE architectures with superior chemical and biological properties in future.

One-pot co-crystallized hexanal-loaded ZIF-8/quaternized chitosan film for temperature-responsive ethylene inhibition and climacteric fruit preservation.

Controlling ethylene production and microbial infection are key factors to prolong the shelf life of climacteric fruit. Herein, a nanocomposite film, hexanal-loaded ZIF-8/CS (HZCF) with "nano-barrier" structure, was developed by a one-pot co-crystallized of ZIF-8 in situ growth on quaternized chitosan (CS) and encapsulation of hexanal into ZIF-8 via microporous adsorption. The resultant film realized the temperature responsive release of hexanal via the steric hindrance and hierarchical pore structure as "nano-barrier", which can inhibit ethylene production in climacteric fruit on demand. Based on this, the maximum ethylene inhibition rate of HZCF was up to 52.6 %. Meanwhile, the film exhibits excellent antibacterial, mechanical, UV resistance and water retention properties, by virtue of the functional synergy between ZIF-8 and CS. Contributed to the multifunctional features, HZCF prolonged the shelf life of banana and mango for at least 16 days, which is 8 days longer than that of control fruit. More strikingly, HZCF is washable and biodegradable, which is expected to replace non-degradable plastic film. Thus, this study provides a convenient novel approach to simplify the encapsulation of active molecule on metal-organic frameworks (MOFs), develops a packaging material for high-efficient freshness preservation, and helps to alleviate the survival crisis caused by food waste.

An AIEgen and Iodine Double-Ornamented Platinum(II) Complex for Bimodal Imaging-Guided Chemo-Photodynamic Combination Therapy.

Real-time biodistribution monitoring and enhancing the therapeutic efficacy of platinum(II)-based anticancer drugs are urgently required to elevate their clinical performance. Herein, a tetraphenylethene derivative (TP) with aggregation-induced emission (AIE) properties and an iodine atom are selected as ligands to endow platinum (II) complex TP-Pt-I with real-time in vivo self-tracking ability by fluorescence (FL) and computerized tomography (CT) imaging, and improved anticancer efficacy by the combination of chemotherapy and photodynamic therapy. Especially, benefiting from the formation of a donor-acceptor-donor structure between the AIE photosensitizer TP and Pt-I moiety, the heavy atom effects of Pt and I, and the presence of I, TP-Pt-I displayed red-shifted absorption and emission wavelengths, enhanced ROS generation efficiency, and improved CT imaging capacity compared with the pristine TP and the control agent TP-Pt-Cl. As a result, the enhanced intratumoral accumulation of TP-Pt-I loaded nanoparticles is readily revealed by dual-modal FL and CT imaging with high contrast. Meanwhile, the TP-Pt-I nanoparticles show significantly improved tumor growth-inhibiting effects on an MCF-7 xenograft murine model by combining the chemotherapeutic effects of platinum(II) and the photodynamic effects of TP. This self-tracking therapeutic complex thus provides a new strategy for improving the therapeutic outcomes of platinum(II)-based anticancer drugs.

Steric Perturbation of the Grob-like Final Step of Ethylene-Forming Enzyme Enables 3-Hydroxypropionate and Propylene Production.

Ethylene-forming enzyme (EFE) is an iron(II)-dependent dioxygenase that fragments 2-oxoglutarate (2OG) to ethylene (from C3 and C4) and 3 equivs of carbon dioxide (from C1, C2, and C5). This major ethylene-forming pathway requires l-arginine as the effector and competes with a minor pathway that merely decarboxylates 2OG to succinate as it oxidatively fragments l-arginine. We previously proposed that ethylene forms in a polar-concerted (Grob-like) fragmentation of a (2-carboxyethyl)carbonatoiron(II) intermediate, formed by the coupling of a C3-C5-derived propion-3-yl radical to a C1-derived carbonate coordinated to the Fe(III) cofactor. Replacement of one or both C4 hydrogens of 2OG by fluorine, methyl, or hydroxyl favored the elimination products 2-(F1-2/Me/OH)-3-hydroxypropionate and CO2 over the expected olefin or carbonyl products, implying strict stereoelectronic requirements in the final step, as is known for Grob fragmentations. Here, we substituted active-site residues expected to interact sterically with the proposed Grob intermediate, aiming to disrupt or enable the antiperiplanar disposition of the carboxylate electrofuge and carbonate nucleofuge required for concerted fragmentation. The bulk-increasing A198L substitution barely affects the first partition between the major and minor pathways but then, as intended, markedly diminishes ethylene production in favor of 3-hydroxypropionate. Conversely, the bulk-diminishing L206V substitution enables propylene formation from (4R)-methyl-2OG, presumably by allowing the otherwise sterically disfavored antiperiplanar conformation of the Grob intermediate bearing the extra methyl group. The results provide additional evidence for a polar-concerted ethylene-yielding step and thus for the proposed radical-polar crossover via substrate-radical coupling to the Fe(III)-coordinated carbonate.

Machine Learning Models for Predicting Zirconocene Properties and Barriers.

Zr metallocenes have significant potential to be highly tunable polyethylene catalysts through modification of the aromatic ligand framework. Here we report the development of multiple machine learning models using a large library (>700 systems) of DFT-calculated zirconocene properties and barriers for ethylene polymerization. We show that very accurate machine learning models are possible for HOMO-LUMO gaps of precatalysts but the performance significantly depends on the machine learning algorithm and type of featurization, such as fingerprints, Coulomb matrices, smooth overlap of atomic positions, or persistence images. Surprisingly, the description of the bonding hapticity, the number of direct connections between Zr and the ligand aromatic carbons, only has a moderate influence on the performance of most models. Despite robust models for HOMO-LUMO gaps, these types of machine learning models based on structure connectivity type features perform poorly in predicting ethylene migratory insertion barrier heights. Therefore, we developed several relatively robust and accurate machine learning models for barrier heights that are based on quantum-chemical descriptors (QCDs). The quantitative accuracy of these models depends on which potential energy surface structure QCDs were harvested from. This revealed a Hammett-type principle to naturally emerge showing that QCDs from the π-coordination complexes provide much better descriptions of the transition states than other potential-energy structures. Feature importance analysis of the QCDs provides several fundamental principles that influence zirconocene catalyst reactivity.

Recent Advances in Synthesis of Non-Alternating Polyketone Generated by Copolymerization of Carbon Monoxide and Ethylene.

The copolymers of carbon monoxide (CO) and ethylene, namely aliphatic polyketones (PKs), have attracted considerable attention due to their unique property and degradation. Based on the arrangement of the ethylene and carbonyl groups in the polymer chain, PKs can be divided into perfect alternating and non-perfect alternating copolymers. Perfect alternating PKs have been previously reviewed, we herein focus on recent advances in the synthesis of PKs without a perfect alternating structure including non-perfect alternating PKs and PE with in-chain ketones. The chain structure of PKs, catalytic copolymerization mechanism, and non-alternating polymerization catalysts including phosphine-sulfonate Pd, diphosphazane monoxide (PNPO) Pd/Ni, and phosphinophenolate Ni catalysts are comprehensively summarized. This review aims to enlighten the design of ethylene/CO non-alternating polymerization catalysts for the development of new polyketone materials.

An exact and vigorous kinetic Monte Carlo simulation to determine the properties of bimodal HDPE synthesized with a dual-site metallocene catalyst.

A vigorous and progressed Monte Carlo strategy was developed to precisely simulate the ethylene and 1-butene copolymerization within the presence of hydrogen by dual-site metallocene catalyst. The results showed up that the ethylene and 1-butene consumption rates at the second catalyst site were approximately 5 times higher than at the first site, and hydrogen transfer rates at the first catalyst site were over 3 times more rapid than at the second site. It was found that the most elevated molar percentage of 1-butene inside the copolymers synthesized from the second site was around 12% and within the copolymers gotten from the first site was around 2%. At a steady hydrogen concentration, with 8 times increase in the 1-butene concentration within the initial feed, the overall weight average molecular weight (M‾w) and an overall number average molecular weight (M‾n) extended by approximately 50% and 40%, respectively. Besides, at a consistent 1-butene concentration, with 8 times increase in the concentration of hydrogen, M‾w and M‾n diminished by approximately 18% and 22%, separately. Due to the synthesis of two groups of chains with distinct molecular weights, the overall dispersity (D) was slightly higher than the dispersity resulting from each catalyst site (1.5-2.1). With increasing 1-butene concentrations, the overall bimodal molecular weight distribution (MWD) widened, and the peak sizes grew smaller and moved towards higher molecular weights. As hydrogen concentration increased, peaks became taller and move toward shorter chain lengths. It was observed that the first site created chain lengths between 102 and 103 while the second site generated chain lengths between 102 and 106. As the concentration of 1-butene was increased in the initial feed, the number of short chain branching per 1000 carbon atoms (SCB/1000C) increased from 10 to 50. Compared to the first site, there were 5 times as many SCBs at the chains produced from the second site. By diminishing the ratio of ethylene to 1-butene, the melt index (MI) tended towards smaller numbers (0.2≤MI≤2). With an increase in the ratio of ethylene to 1-butene and ethylene to hydrogen, the weight fraction of crystals raised from 67.4 to 69.5% and diminished from 71 to 69.5%, respectively. At last, increasing the temperature led to a diminish in molecular weight, a narrowing of the bimodal MWD, an increment within the thickness and weight fraction of crystals, and an increment within the density of HDPE.

Unraveling the comonomer distribution in ethylene - vinyl ester terpolymers through liquid chromatography with infrared detection.

Polyolefins are the most commercially relevant polymers by volume. A readily available feedstock and their tailor-made microstructure allow to adapt polyolefins to many fields of application. Important molecular design features of olefin copolymers are the molar mass distribution (MMD) with the corresponding average values, comonomer type, chemical composition distribution (CCD) with the corresponding average and the tacticity distribution (TD). Advanced separation techniques i.e., high-temperature gel permeation chromatography (HT-GPC) as well as its hyphenation with high-temperature high performance liquid chromatography (HT-HPLC) in the form of high-temperature two-dimensional liquid chromatography (HT 2D-LC) have been successfully applied in this work. This allowed to deeply analyze the molecular heterogeneities of complex polyolefin terpolymers consisting of ethylene, vinyl acetate and branched vinyl ester monomers. By using filter-based infrared detection, the capabilities of HT-GPC are further extended so that the distribution of methyl- and carbonyl groups could be obtained along the molar mass axis. Using porous graphitic carbon (PGC) as a stationary phase for HT-HPLC separation provided information about the CCD of these complex polyolefins from experimental data as part of the hyphenated approach of HT 2D-LC. The latter revealed the full MMD x CCD distribution function, which is the key for a comprehensive analysis of the bivariate molecular structure of the polyolefin terpolymers.

Can an external electric field switch between ethylene formation and L-arginine hydroxylation in the ethylene forming enzyme?

The non-heme Fe(II) and 2-oxoglutarate (2OG) dependent ethylene-forming enzyme (EFE) catalyzes both ethylene generation and L-Arg hydroxylation. Despite experimental and computational progress in understanding the mechanism of EFE, no EFE variant has been optimized for ethylene production while simultaneously reducing the L-Arg hydroxylation activity. In this study, we show that the two L-Arg binding conformations, associated with different reactivity preferences in EFE, lead to differences in the intrinsic electric field (IntEF) of EFE. Importantly, we suggest that applying an external electric field (ExtEF) along the Fe-O bond in the EFE·Fe(III)·OO-˙·2OG·L-Arg complex can switch the EFE reactivity between L-Arg hydroxylation and ethylene generation. Furthermore, we explored how applying an ExtEF alters the geometry, electronic structure of the key reaction intermediates, and the individual energy contributions of second coordination sphere (SCS) residues through combined quantum mechanics/molecular mechanics (QM/MM) calculations. Experimentally generated variant forms of EFE with alanine substituted for SCS residues responsible for stabilizing the key intermediates in the two reactions of EFE led to changes in enzyme activity, thus demonstrating the key role of these residues. Overall, the results of applying an ExtEF indicate that making the IntEF of EFE less negative and stabilizing the off-line binding of 2OG is predicted to increase ethylene generation while reducing L-Arg hydroxylation.

Multiplication, morphogenesis and foliar abscision of Schinopsis brasiliensis Engl. in vitro / Multiplicación, morfogénesis y abscisión foliar de Schinopsis brasiliensis Engl. in vitro

The objective was to evaluate plant growth regulators and ethylene inhibitors on the development and leaf abscission of Schinopsis brasiliensis Engl. Zeatin (ZEA) was evaluated in concentrations combined with concentrations of indolacetic acid (IAA), naphthalene acetic acid (NAA) and indolbutyric acid (IBA). ZEA and 6-benzylamino purine (BAP) were evaluated in concentrations plus a control. Ethylene inhibitors, silver nitrate and cobalt chloride were evaluated in four concentrations. The addition of 0.2 µL-1 of NAA to 0.4 µL-1 of ZEA promotes a greater number of baraúna sprouts. At concentrations of 5 and 10 µM, cobalt chloride is more efficient than silver nitrate for reducing leaf abscission in baraúna. IAA is the most suitable auxin to be associated with ZEA for higher shoot length and number of buds. Silver nitrate from a concentration of 20 µM completely avoids leaf abscission whilecobalt chloride has a maximum reduction in abscission at a concentration of 40 µM.

El objetivo fue evaluar reguladores de crecimiento e inhibidores de etileno sobre el desarrollo y abscisión foliar en Schinopsis brasiliensis Engl. La zeatina (ZEA) se evaluó en concentraciones combinadas con concentraciones de ácido indolacético (IAA), ácido naftaleno acético (NAA) y ácido indolbutírico (IBA). Se evaluaron ZEA y 6-bencilamino purina (BAP) en concentraciones más un control. Se evaluaron inhibidores de etileno, nitrato de plata y cloruro de cobalto, en cuatro concentraciones. La adición de 0.2 µL-1 de NAA a 0.4 µL-1 de ZEA promueve un mayor número de brotes de baraúna. A concentraciones de 5 y 10 µM, el cloruro de cobalto es más eficaz que el nitrato de plata para reducir la abscisión de las hojas en baraúna. IAA es la auxina más adecuada para asociar con ZEA para una mayor longitud de brotes y número de brotes. El nitrato de plata a partir de una concentración de 20 µM evita completamente la abscisión de las hojas, mientras que el cloruro de cobalto tiene una reducción máxima en la abscisión a una concentración de 40 µM.