More Like this

1. Stable native RIP 9 complexes associate with C‐to‐U RNA editing activity, PPR s, RIP s, OZ 1, ORRM 1 and ISE 2

   https://doi.org/10.1111/tpj.14384  

   Sandoval, Rafael ; Boyd, Robert D. ; Kiszter, Alena N. ; Mirzakhanyan, Yeva ; Santibańez, Paola ; Gershon, Paul D. ; Hayes, Michael L. ( June 2019 , The Plant Journal)

   The mitochondrial and chloroplastmRNAs of the majority of land plants are modified through cytidine to uridine (C‐to‐U)RNAediting. Previously, forward and reverse genetic screens demonstrated a requirement for pentatricopeptide repeat (PPR) proteins forRNAediting. Moreover, chloroplast editing factorsOZ1,RIP2,RIP9 andORRM1 were identified in co‐immunoprecipitation (co‐IP) experiments, albeit the minimal complex sufficient for editing activity was never deduced. The current study focuses on isolated, intact complexes that are capable of editing distinct sites. Peak editing activity for four sites was discovered in size‐exclusion chromatography (SEC) fractions ≥ 670 kDa, while fractions estimated to be approximately 413 kDa exhibited the greatest ability to convert a substrate containing the editing siterps14C80.RNAcontent peaked in the ≥ 670 kDa fraction. Treatment of active chloroplast extracts withRNase A abolished the relationship of editing activity with high‐MWfractions, suggesting a structuralRNAcomponent in native complexes. By immunoblotting,RIP9,OTP86,OZ1 andORRM1 were shown to be present in active gel filtration fractions, thoughOZ1 andORRM1 were mainly found in low‐MWinactive fractions. Active editing factor complexes were affinity‐purified using anti‐RIP9 antibodies, and orthologs to putativeArabidopsis thalianaRNAediting factorPPRproteins,RIP2,RIP9,RIP1,OZ1,ORRM1 andISE2 were identified via mass spectrometry. Western blots from co‐IP studies revealed the mutual association ofOTP86 andOZ1 with nativeRIP9 complexes. Thus,RIP9 complexes were discovered to be highly associated with C‐to‐URNAediting activity and other editing factors indicative of their critical role in vascular plant editosomes.

    

   more » « less
2. Modeling performance of rhamnolipid-coated engineered magnetite nanoparticles for U( vi ) sorption and separation

   https://doi.org/10.1039/d0en00416b  

   Sharma, Neha ; Ghosh, Anushree ; Fortner, John D. ; Giammar, Daniel E. ( July 2020 , Environmental Science: Nano)

   Based on tunable properties, engineered nanoparticles (NPs) hold significant promise for water treatment technologies. Motivated by concerns regarding toxicity and non-biodegradability of some nanoparticles, we explored engineered magnetite (Fe 3 O 4 ) nanoparticles with a biocompatible coating. These were prepared with a coating of rhamnolipid, a biosurfactant primarily obtained from Pseudomonas aeruginosa . By optimizing synthesis and phase transfer conditions, particles were observed to be monodispersed and stable in water under environmentally relevant pH and ionic strength values. These materials were evaluated for U( vi ) removal from water at varying dissolved inorganic carbon and pH conditions. The rhamnolipid-coated iron oxide nanoparticles (IONPs) showed high sorption capacities at pH 6 and pH 8 in both carbonate-free systems and systems in equilibrium with atmospheric CO 2 . Equilibrium sorption behavior was interpreted using surface complexation modeling (SCM). Two models (diffuse double layer and non-electrostatic) were evaluated for their ability to account for U( vi ) binding to the carboxyl groups of the rhamnolipid coating as a function of the pH, total U( vi ) loading, and dissolved inorganic carbon concentration. The diffuse double layer model provided the best simulation of the adsorption data and was sensitive to U( vi ) loadings as it accounted for the change in the surface charge associated with U( vi ) adsorption. 

   more » « less
3. 2.2.2-Cryptand complexes of neptunium( iii ) and plutonium( iii )

   https://doi.org/10.1039/D1CC05904A  

   Goodwin, Conrad A. ; Ciccone, Sierra R. ; Bekoe, Samuel ; Majumdar, Sourav ; Scott, Brian L. ; Ziller, Joseph W. ; Gaunt, Andrew J. ; Furche, Filipp ; Evans, William J. ( January 2022 , Chemical Communications)

   New coordination environments are reported for Np( iii ) and Pu( iii ) based on pilot studies of U( iii ) in 2.2.2-cryptand (crypt). The U( iii )-in-crypt complex, [U(crypt)I 2 ][I], obtained from the reaction between UI 3 and crypt, is treated with Me 3 SiOTf (OTf = O 3 SCF 3 ) in benzene to form the [U(crypt)(OTf) 2 ][OTf] complex. Similarly, the isomorphous Np( iii ) and Pu( iii ) complexes were obtained similarly starting from [AnI 3 (THF) 4 ]. All three complexes (1-An; An = U, Np, Pu) contain an encapsulated actinide in a THF-soluble complex. Absorption spectroscopy and DFT calculations are consistent with 5f 3 U( iii ), 5f 4 Np( iii ), and 5f 5 Pu( iii ) electron configurations. 

   more » « less
4. An exploratory study of “large‐ n ” detrital zircon geochronology of the Book Cliffs, UT via rapid (3 s/analysis) U–Pb dating

   https://doi.org/10.1111/bre.12840  

   Sundell, Kurt E. ; Gehrels, George E. ; D. Blum, Michael ; Saylor, Joel E. ; Pecha, Mark E. ; Hundley, Bridget P. ( January 2024 , Basin Research)

   Detrital zircon (DZ) U–Pb geochronology has improved the way geologists approach questions of sediment provenance and stratigraphic age. However, there is debate about what constitutes an appropriate sample size (i.e., the number of dates in a DZ sample,n), which depends on project objectives, sample complexity, and, critically, analytical budget. Additionally, there is ongoing concern about bias introduced by zircon grain size. We tested a recently developed rapid (3 s/analysis) data acquisition method by multicollector laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) that incorporates an automated selection routine and calculates two‐dimensional grain geometry from polished sample surfaces. Eleven samples were analysed from below and above the Late Cretaceous (Campanian) basal Castlegate unconformity of the Book Cliffs, Utah, in a down‐depositional‐dip transect including Price, Horse, Tusher, and Thompson canyons. 12,448 new concordant dates were generated during two measurement sessions. Results are consistent with recent studies suggesting there is no major provenance change and little time (1–2 Myr) represented across the unconformity. Grain size and sample size both exert a strong control on sample dissimilarity. Age distributions constructed from subsamples of large grains are systematically less similar to whole samples; age distributions composed of small grains are overall more similar to whole samples. As such, North American sediment sources that produce large grains such as the Grenville and Yavapi‐Mazatzal belts can bias age distributions if only large grains are analysed. A sample size ofn = 100 is inadequate for characterizing age distributions as complex as those of the Book Cliffs, whereas a sample size ofn = 300 provides good characterization. Sample size ofn ≈ 1000 or more is unnecessary unless project objectives include scanning for subordinate age groups, such as when identifying the youngest grains for calculating a maximum depositional age (MDA). Dates used in MDA calculations acquired with rapid acquisition are best re‐analysed with longer LA‐ICP‐MS acquisition methods or isotope dilution thermal ionization mass spectrometry for increased accuracy and precision. We include new MATLAB code and open‐source software programs,DZpickandDZmda, for automated spot picking and calculating MDAs.

    

   more » « less
5. (U‐Th)/He and 4 He/ 3 He Thermochronology of Secondary Oxides in Faults and Fractures: A Regional Perspective From Southeastern Arizona

   https://doi.org/10.1029/2021GC009905  

   Scoggin, Shane H. ; Reiners, Peter W. ; Shuster, David L. ; Davis, George H. ; Ward, Lauren A. ; Worthington, James R. ; Nickerson, Phillip A. ; Evenson, Nathan S. ( November 2021 , Geochemistry, Geophysics, Geosystems)

   Fe‐ and Mn‐oxides are common secondary minerals in faults, fractures, and veins and potentially record information about the timing of fluid movement through their host rocks. These phases are difficult to date by most radioisotopic techniques, but relatively high concentrations of U and Th make the (U‐Th)/He system a promising approach. We present new petrographic, geochronologic and thermochronologic analyses of secondary oxides and associated minerals from fault zones and fractures in southeastern Arizona. We use these phases in attempt to constrain the timing of fluid flow and their relationship to magmatic, tectonic, or other regional processes. In the shallowly exhumed Galiuro Mountains, Fe‐oxide (U‐Th)/He dates correspond to host‐rock crystallization and magmatic intrusions from ca. 1.6 to 1.1 Ga. Step‐heating⁴He/³He experiments and polydomain diffusion modeling of³He release spectra on these samples are consistent with a crystallite size control on He diffusivity, and little fractional loss of radiogenic He since formation in coarse‐grained hematite, but large losses from fine‐grained Mn‐oxide. In contrast to Proterozoic dates, Fe‐ and Mn‐oxides from the Catalina‐Rincon and Pinaleño metamorphic core complexes are exclusively Cenozoic, with dates clustering at ca. 24, 15, and 9 Ma, which represent distinct cooling or fluid‐flow episodes during punctuated periods of normal faulting. Finally, a subset of Fe‐oxides yield dates of ca. 5 Ma to 6 ka and display either pseudomorphic cubic forms consistent with oxidative retrogression of original pyrite or magnetite, or fine‐grained botryoidal morphologies that we interpret to represent approximate ages of recrystallization or pseudomorphic replacement at shallow depths.

    

   more » « less