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1. Effects of denitrification on the distributions of trace gas abundances in the polar regions: a comparison of WACCM with observations

   https://doi.org/10.5194/acp-23-6849-2023  

   Weimer, Michael; Kinnison, Douglas E.; Wilka, Catherine; Solomon, Susan (January 2023, Atmospheric Chemistry and Physics)

   Abstract. Polar stratospheric clouds (PSCs) play a key role in the polar chemistry of the stratosphere. Nitric acid trihydrate (NAT) particles have been shown to lead to denitrification of the lower stratosphere. While the existence of large NAT particles (NAT “rocks”) has been verified by many measurements, especially in the Northern Hemisphere (NH), most current chemistry–climate models use simplified parameterizations, often based on evaluations in the Southern Hemisphere where the polar vortex is stable enough that accounting for NAT rocks is not as important as in the NH. Here, we evaluate the probability density functions of various gaseous species in the polar vortex using one such model, the Whole Atmosphere Community Climate Model (WACCM), and compare these with measurements by the Michelson Interferometer for Passive Atmospheric Sounding onboard the Environmental Satellite (MIPAS/Envisat) and two ozonesonde stations for a range of years and in both hemispheres. Using the maximum difference between the distributions of MIPAS and WACCM as a measure of coherence, we find better agreement for HNO3 when reducing the NAT number density from the standard value of 10−2 used in this model to 5×10-4 cm−3 for almost all spring seasons during the MIPAS period in both hemispheres. The distributions of ClONO2 and O3 are not greatly affected by the NAT density. The average difference between WACCM and ozonesondes supports the need to reduce the NAT number density in the model. Therefore, this study suggests using a NAT number density of 5×10-4 cm−3 for future simulations with WACCM. 

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2. Synthesis and crystallographic characterization of diphenylamide rare-earth metal complexes Ln (NPh ₂ ) ₃ (THF) ₂ and [(Ph ₂ N) ₂ Ln (μ-NPh ₂ )] ₂

   https://doi.org/10.1107/S2056989020009998  

   Palumbo, Chad T.; Kotyk, Christopher M.; Ziller, Joseph W.; Evans, William J. (September 2020, Acta Crystallographica Section E Crystallographic Communications)

   null (Ed.)

   Studies of the coordination chemistry between the diphenylamide ligand, NPh 2 , and the smaller rare-earth Ln III ions, Ln = Y, Dy, and Er, led to the structural characterization by single-crystal X-ray diffraction crystallography of both solvated and unsolvated complexes, namely, tris(diphenylamido-κ N )bis(tetrahydrofuran-κ O )yttrium(III), Y(NPh 2 ) 3 (THF) 2 or [Y(C 12 H 10 N) 3 (C 4 H 8 O) 2 ], 1-Y , and the erbium(III) (Er), 1-Er , analogue, and bis[μ-1κ N :2(η 6 )-diphenylamido]bis[bis(diphenylamido-κ N )yttrium(III)], [(Ph 2 N) 2 Y(μ-NPh 2 )] 2 or [Y 2 (C 12 H 10 N) 6 ], 2-Y , and the dysprosium(III) (Dy), 2-Dy , analogue. The THF ligands of 1-Er are modeled with disorder across two positions with occupancies of 0.627 (12):0.323 (12) and 0.633 (7):0.367 (7). Also structurally characterized was the tetrametallic Er III bridging oxide hydrolysis product, bis(μ-diphenylamido-κ 2 N : N )bis[μ-1κ N :2(η 6 )-diphenylamido]tetrakis(diphenylamido-κ N )di-μ 3 -oxido-tetraerbium(III) benzene disolvate, {[(Ph 2 N)Er(μ-NPh 2 )] 4 (μ-O) 2 }·(C 6 H 6 ) 2 or [Er 4 (C 12 H 10 N) 8 O 2 ]·2C 6 H 6 , 3-Er . The 3-Er structure was refined as a three-component twin with occupancies 0.7375:0.2010:0.0615. 

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3. Asymmetric Redox‐Polymer Interfaces for Electrochemical Reactive Separations: Synergistic Capture and Conversion of Arsenic

   https://doi.org/10.1002/adma.201906877  

   Kim, Kwiyong; Cotty, Stephen; Elbert, Johannes; Chen, Raylin; Hou, Chia‐Hung; Su, Xiao (December 2019, Advanced Materials)

   Abstract Advanced redox‐polymer materials offer a powerful platform for integrating electroseparations and electrocatalysis, especially for water purification and environmental remediation applications. The selective capture and remediation of trivalent arsenic (As(III)) is a central challenge for water purification due to its high toxicity and difficulty to remove at ultra‐dilute concentrations. Current methods present low ion selectivity, and require multistep processes to transform arsenic to the less harmful As(V) state. The tandem selective capture and conversion of As(III) to As(V) is achieved using an asymmetric design of two redox‐active polymers, poly(vinyl)ferrocene (PVF) and poly‐TEMPO‐methacrylate (PTMA). During capture, PVF selectively removes As(III) with exceptional uptake (>100 mg As/g adsorbent), and during release, synergistic electrocatalytic oxidation of As(III) to As(V) with >90% efficiency can be achieved by PTMA, a radical‐based redox polymer. The system demonstrates >90% removal efficiencies with real wastewater and concentrations of arsenic as low as 10 ppb. By integrating electron‐transfer through the judicious design of asymmetric redox‐materials, an order‐of‐magnitude energy efficiency increase can be achieved compared to non‐faradaic, carbon‐based materials. The study demonstrates for the first time the effectiveness of asymmetric redox‐active polymers for integrated reactive separations and electrochemically mediated process intensification for environmental remediation. 

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4. Chapter Six - Heterologous expression, purification, and characterization of proteins in the lanthanome

   https://doi.org/10.1016/bs.mie.2021.02.004  

   Featherston, Emily R; Mattocks, Joseph A; Trisch, Jonathan L; Cotruvo Jr, Joseph A (April 2021, Methods in enzymology)

   Cotruvo Jr, Joseph A (Ed.)

   Recent work has revealed that certain lanthanides—in particular, the more earth-abundant, lighter lanthanides—play essential roles in pyrroloquinoline quinone (PQQ) dependent alcohol dehydrogenases from methylotrophic and non-methylotrophic bacteria. More recently, efforts of several laboratories have begun to identify the molecular players (the lanthanome) involved in selective uptake, recognition, and utilization of lanthanides within the cell. In this chapter, we present protocols for the heterologous expression in Escherichia coli, purification, and characterization of many of the currently known proteins that comprise the lanthanome of the model facultative methylotroph, Methylorubrum extorquens AM1. In addition to the methanol dehydrogenase XoxF, these proteins include the associated c-type cytochrome, XoxG, and solute binding protein, XoxJ. We also present new, streamlined protocols for purification of the highly selective lanthanide-binding protein, lanmodulin, and a solute binding protein for PQQ, PqqT. Finally, we discuss simple, spectroscopic methods for determining lanthanide- and PQQ-binding stoichiometry of proteins. We envision that these protocols will be useful to investigators identifying and characterizing novel members of the lanthanome in many organisms. 

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5. Enhanced rare-earth separation with a metal-sensitive lanmodulin dimer

   https://doi.org/10.1038/s41586-023-05945-5  

   Mattocks, Joseph A.; Jung, Jonathan J.; Lin, Chi-Yun; Dong, Ziye; Yennawar, Neela H.; Featherston, Emily R.; Kang-Yun, Christina S.; Hamilton, Timothy A.; Park, Dan M.; Boal, Amie K.; et al (June 2023, Nature)

   Abstract Technologically critical rare-earth elements are notoriously difficult to separate, owing to their subtle differences in ionic radius and coordination number^1–3. The natural lanthanide-binding protein lanmodulin (LanM)^4,5is a sustainable alternative to conventional solvent-extraction-based separation⁶. Here we characterize a new LanM, fromHansschlegelia quercus(Hans-LanM), with an oligomeric state sensitive to rare-earth ionic radius, the lanthanum(III)-induced dimer being >100-fold tighter than the dysprosium(III)-induced dimer. X-ray crystal structures illustrate how picometre-scale differences in radius between lanthanum(III) and dysprosium(III) are propagated toHans-LanM’s quaternary structure through a carboxylate shift that rearranges a second-sphere hydrogen-bonding network. Comparison to the prototypal LanM fromMethylorubrum extorquensreveals distinct metal coordination strategies, rationalizingHans-LanM’s greater selectivity within the rare-earth elements. Finally, structure-guided mutagenesis of a key residue at theHans-LanM dimer interface modulates dimerization in solution and enables single-stage, column-based separation of a neodymium(III)/dysprosium(III) mixture to >98% individual element purities. This work showcases the natural diversity of selective lanthanide recognition motifs, and it reveals rare-earth-sensitive dimerization as a biological principle by which to tune the performance of biomolecule-based separation processes. 

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