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

   https://doi.org/10.1039/d3cp01899g  

   Chaturvedi, Shobhit S.; Jaber Sathik Rifayee, Simahudeen Bathir; Ramanan, Rajeev; Rankin, Joel A.; Hu, Jian; Hausinger, Robert P.; Christov, Christo Z. (May 2023, Physical Chemistry Chemical Physics)

   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. 

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2. Gold( i ) ethylene complexes supported by electron-rich scorpionates

   https://doi.org/10.1039/d0cc07717h  

   Wu, Jiang; Noonikara-Poyil, Anurag; Muñoz-Castro, Alvaro; Dias, H. V. (February 2021, Chemical Communications)

   null (Ed.)

   Ethylene complexes of gold( i ) have been stabilized by electron-rich, κ 2 -bound tris(pyrazolyl)borate ligands. Large up-field shifts of olefinic carbon NMR resonances and relatively long CC distances of gold bound ethylene are indicative of significant Au( i ) → ethylene π-backbonding relative to the analog supported by a weakly donating ligand, consistent with the computational data. 

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3. Bonding and ¹³C‐NMR properties of coinage metal tris(ethylene) and tris(norbornene) complexes: Evaluation of the role of relativistic effects from DFT calculations

   https://doi.org/10.1002/jcc.26987  

   Muñoz‐Castro, Alvaro; Dias, H. V. (October 2022, Journal of Computational Chemistry)
4. In Situ Electron Microscopy of Poly(ethylene glycol) Crystals Grown in Thin Ionic Liquids Films

   https://doi.org/10.1002/pol.20190120  

   Srivastava, Satyam; Ribbe, Alexander E.; Russell, Thomas P.; Hoagland, David A. (January 2020, Journal of Polymer Science)

   ABSTRACT Crystals of poly(ethylene glycol) grown in thin films of the room temperature ionic liquid (IL) 1‐ethyl‐3‐methylimidazolium ethyl sulfate were examined by electron microscopy as a first step toward exploiting nonvolatile liquids for nanoscale imaging of solvated/dissolved polymeric materials. The crystals were generated by cooling supported (over surfaces of varied polarity) and freestanding solution films to room temperature. This “open,” that is, without liquid cell, microscopy was performed on unstained, as‐grown crystals in the presence of the IL. A variety of nearly two‐dimensional crystal morphologies were observed, including rods, fibers, spherulites, compact faceted single crystals, and interconnected networks, with characteristic sizes ranging from tens of nanometers to tens of microns. Electron diffraction patterns for the rods and fibers revealed single crystal‐like long‐range order. The nature of the IL support little affected the morphology, but film thickness and cooling rate proved important. To assess the role of solvent polarity, crystals were also grown from 1‐ethyl‐3‐methylimidazolium ethyl sulfate mixed with the second IL, the less polar ethyl‐tributyl‐phosphonium diethyl phosphate; here, although the morphologies were similar to those made with pure IL, fibrillar morphologies were more prevalent. © 2020 Wiley Periodicals, Inc. J. Polym. Sci.2020,58, 478–486 

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5. A role for ethylene signaling and biosynthesis in regulating and accelerating CO₂ ‐ and abscisic acid‐mediated stomatal movements in Arabidopsis

   https://doi.org/10.1111/nph.18918  

   Azoulay‐Shemer, Tamar; Schulze, Sebastian; Nissan‐Roda, Dikla; Bosmans, Krystal; Shapira, Or; Weckwerth, Philipp; Zamora, Olena; Yarmolinsky, Dmitry; Trainin, Taly; Kollist, Hannes; et al (April 2023, New Phytologist)

   Summary Little is known about long‐distance mesophyll‐driven signals that regulate stomatal conductance. Soluble and/or vapor‐phase molecules have been proposed. In this study, the involvement of the gaseous signal ethylene in the modulation of stomatal conductance inArabidopsis thalianaby CO₂/abscisic acid (ABA) was examined.We present a diffusion model which indicates that gaseous signaling molecule/s with a shorter/direct diffusion pathway to guard cells are more probable for rapid mesophyll‐dependent stomatal conductance changes. We, therefore, analyzed different Arabidopsis ethylene‐signaling and biosynthesis mutants for their ethylene production and kinetics of stomatal responses to ABA/[CO₂]‐shifts.According to our research, higher [CO₂] causes Arabidopsis rosettes to produce more ethylene. An ACC‐synthase octuple mutant with reduced ethylene biosynthesis exhibits dysfunctional CO₂‐induced stomatal movements. Ethylene‐insensitive receptor (gain‐of‐function),etr1‐1andetr2‐1, and signaling,ein2‐5andein2‐1, mutants showed intact stomatal responses to [CO₂]‐shifts, whereas loss‐of‐function ethylene receptor mutants, includingetr2‐3;ein4‐4;ers2‐3,etr1‐6;etr2‐3andetr1‐6, showed markedly accelerated stomatal responses to [CO₂]‐shifts. Further investigation revealed a significantly impaired stomatal closure to ABA in the ACC‐synthase octuple mutant and accelerated stomatal responses in theetr1‐6;etr2‐3, andetr1‐6, but not in theetr2‐3;ein4‐4;ers2‐3mutants.These findings suggest essential functions of ethylene biosynthesis and signaling components in tuning/accelerating stomatal conductance responses to CO₂and ABA. 

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