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1. Supramolecular Catalysis of the oxa‐Pictet–Spengler Reaction with an Endohedrally Functionalized Self‐Assembled Cage Complex

   https://doi.org/10.1002/anie.202009553  

   Ngai, Courtney ; Sanchez‐Marsetti, Colomba M. ; Harman, W. Hill ; Hooley, Richard J. ( October 2020 , Angewandte Chemie International Edition)

   An endohedrally functionalized self‐assembled Fe₄L₆cage complex can catalyze oxa‐Pictet—Spengler cyclizations of tryptophols and various aldehyde derivatives, showing strong rate accelerations and size‐selectivity. Selective molecular recognition of substrates controls the reactivity, and the cage is capable of binding and activating multiple different species along the multistep reaction pathway. The combination of a functionalized active site, size‐selective reactivity, and multistep activation, all from a single host molecule, illustrates the biomimetic nature of the catalysis.
2. Supramolecular Catalysis of the oxa‐Pictet–Spengler Reaction with an Endohedrally Functionalized Self‐Assembled Cage Complex

   https://doi.org/10.1002/ange.202009553  

   Ngai, Courtney ; Sanchez‐Marsetti, Colomba M. ; Harman, W. Hill ; Hooley, Richard J. ( October 2020 , Angewandte Chemie)

   An endohedrally functionalized self‐assembled Fe₄L₆cage complex can catalyze oxa‐Pictet—Spengler cyclizations of tryptophols and various aldehyde derivatives, showing strong rate accelerations and size‐selectivity. Selective molecular recognition of substrates controls the reactivity, and the cage is capable of binding and activating multiple different species along the multistep reaction pathway. The combination of a functionalized active site, size‐selective reactivity, and multistep activation, all from a single host molecule, illustrates the biomimetic nature of the catalysis.
3. Host-Associated Rhizobial Fitness: Dependence on Nitrogen, Density, Community Complexity, and Legume Genotype

   https://doi.org/10.1128/aem.00526-22  

   Burghardt, Liana T. ; Epstein, Brendan ; Hoge, Michelle ; Trujillo, Diana I. ; Tiffin, Peter ( August 2022 , Applied and Environmental Microbiology)

   Glass, Jennifer B. (Ed.)

   ABSTRACT The environmental context of the nitrogen-fixing mutualism between leguminous plants and rhizobial bacteria varies over space and time. Variation in resource availability, population density, and composition likely affect the ecology and evolution of rhizobia and their symbiotic interactions with hosts. We examined how host genotype, nitrogen addition, rhizobial density, and community complexity affected selection on 68 rhizobial strains in the Sinorhizobium meliloti – Medicago truncatula mutualism. As expected, host genotype had a substantial effect on the size, number, and strain composition of root nodules (the symbiotic organ). The understudied environmental variable of rhizobial density had a stronger effect on nodule strain frequency than the addition of low nitrogen levels. Higher inoculum density resulted in a nodule community that was less diverse and more beneficial but only in the context of the more selective host genotype. Higher density resulted in more diverse and less beneficial nodule communities with the less selective host. Density effects on strain composition deserve additional scrutiny as they can create feedback between ecological and evolutionary processes. Finally, we found that relative strain rankings were stable across increasing community complexity (2, 3, 8, or 68 strains). This unexpected result suggests that higher-order interactions between strains are raremore »in the context of nodule formation and development. Our work highlights the importance of examining mechanisms of density-dependent strain fitness and developing theoretical predictions that incorporate density dependence. Furthermore, our results have translational relevance for overcoming establishment barriers in bioinoculants and motivating breeding programs that maintain beneficial plant-microbe interactions across diverse agroecological contexts. IMPORTANCE Legume crops establish beneficial associations with rhizobial bacteria that perform biological nitrogen fixation, providing nitrogen to plants without the economic and greenhouse gas emission costs of chemical nitrogen inputs. Here, we examine the influence of three environmental factors that vary in agricultural fields on strain relative fitness in nodules. In addition to manipulating nitrogen, we also use two biotic variables that have rarely been examined: the rhizobial community's density and complexity. Taken together, our results suggest that (i) breeding legume varieties that select beneficial strains despite environmental variation is possible, (ii) changes in rhizobial population densities that occur routinely in agricultural fields could drive evolutionary changes in rhizobial populations, and (iii) the lack of higher-order interactions between strains will allow the high-throughput assessments of rhizobia winners and losers during plant interactions.« less
4. Reductive transformations of dichloroacetamide safeners: effects of agrochemical co-formulants and iron oxide + manganese oxide binary-mineral systems

   https://doi.org/10.1039/D0EM00331J  

   Ricko, Allison N. ; Psoras, Andrew W. ; Sivey, John D. ( October 2020 , Environmental Science: Processes & Impacts)

   The toxic effects of herbicides are often incompletely selective and can harm crops. Safeners are “inert” ingredients commonly added to herbicide formulations to protect crops from herbicide-induced injury. Dichloroacetamide safeners have been previously shown to undergo reductive dechlorination in anaerobic abiotic systems containing an iron (hydr)oxide mineral (goethite or hematite) amended with Fe( ii ). Manganese oxides ( e.g. , birnessite) are important redox-active species that frequently co-occur with iron (hydr)oxides, yet studies examining the effects of more than one mineral on transformations of environmental contaminants are rare. Herein, we investigate the reactivity of dichloroacetamide safeners benoxacor, furilazole, and dichlormid in binary-mineral, anaerobic systems containing Fe( ii )-amended hematite and birnessite. As the molar ratio of Fe( ii )-to-Mn( iv ) oxide increased, the transformation rate of benoxacor and furilazole increased. The safener dichlormid did not transform appreciably over the sampling period (6 hours). The concentration of pH buffer ([MOPS] = 10–50 mM), ionic strength ([NaCl] = 10–200 mM), and order of solute addition ( e.g. , safener followed by Fe( ii ) or vice versa ) do not appreciably affect transformation rates of the examined dichloroacetamide safeners in Fe( ii ) + hematite slurries. The presence of agrochemical co-formulants,more »including the herbicide S -metolachlor and three surfactants, in solutions containing Cr(H 2 O) 6 2+ (as a model homogeneous reductant) also did not substantially influence rates of safener transformation. This study is among the first to examine laboratory systems of intermediate complexity ( e.g. , systems containing mixtures of agrochemical co-formulants or mineral phases) when assessing the environmental fate of emerging contaminants such as dichloroacetamide safeners.« less
5. An ionic Fe-based metal–organic-framework with 4′-pyridyl-2,2′:6′,2′′-terpyridine for catalytic hydroboration of alkynes

   https://doi.org/10.1039/D2RA08040K  

   Zhang, Guoqi ; Zheng, Shengping ; Neary, Michelle C. ( January 2023 , RSC Advances)

   An ionic metal–organic-framework (MOF) containing nanoscale channels was readily assembled from ditopic 4′-pyridyl-2,2′:6′,2′′-terpyridine (pytpy) and a simple iron( ii ) salt. X-ray structural analysis revealed a two-dimensional grid-like framework assembled by classic octahedral (pytpy) 2 Fe II cations as linkers (with pytpy as a new ditopic pyridyl ligand) and octa-coordinate FeCl 2 centers as nodes. The layer-by-layer assembly of the 2-D framework resulted in the formation of 3-D porous materials consisting of nano-scale channels. The charges of the cationic framework were balanced with anionic Cl 3 FeOFeCl 3 in its void channels. The new Fe-based MOF material was employed as a precatalyst for syn -selective hydroboration of alkynes under mild, solvent-free conditions in the presence of an activator, leading to the synthesis of a range of trans -alkenylboronates in good yields. The larger scale applicability and recyclability of the new MOF catalyst was further explored. This represents a rare example of an ionic MOF material that can be utilized in hydroboration catalysis.