To predict potential medical value or toxicity of nanoparticles (NPs), it is necessary to understand the chemical transformation during intracellular processes of NPs. However, it is a grand challenge to capture a high-resolution image of metallic NPs in a single cell and the chemical information on intracellular NPs. Here, by integrating synchrotron radiation-beam transmission X-ray microscopy (SR-TXM) and SR-X-ray absorption near edge structure (SR-XANES) spectroscopy, we successfully capture the 3D distribution of silver NPs (AgNPs) inside a single human monocyte (THP-1), associated with the chemical transformation of silver. The results reveal that the cytotoxicity of AgNPs is largely due to the chemical transformation of particulate silver from elemental silver (Ag(0))n, to Ag(+) ions and Ag-O-, then Ag-S- species. These results provide direct evidence in the long-lasting debate on whether the nanoscale or the ionic form dominates the cytotoxicity of silver nanoparticles. Further, the present approach provides an integrated strategy capable of exploring the chemical origins of cytotoxicity in metallic nanoparticles.

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Pentatricopeptide repeat (PPR) proteins comprise a large family of sequence-specific RNA binding proteins in land plants. Because of its large family size and frequent embryo lethality in the mutants, molecular functions and physiological roles of many PPR proteins are unknown. Through characterization of an empty pericarp9 (emp9) mutant in maize (Zea mays), we defined the functions of EMP9 in mitochondrial RNA editing, respiratory complex formation and seed development. Mu insertions in different regions of Emp9 facilitated dissection of the domain functions of the EMP9. Through genetic and functional analyses of multiple alleles, we showed that deletions of two N-terminal PPR motifs and partial E+ domain do not eliminate the editing function of EMP9. Emp9 encodes an E+ subclass PPR protein that is localized in mitochondria. Loss of EMP9 function abolishes the C-to-U editing of ccmB-43 and rps4-335 sites in mitochondria. The loss of editing at ccmB-43 and rps4-335 affects the maturation of cytochrome c and impairs the biogenesis of mitochondrial respiratory complexes, particularly complex III. This work extends our understanding of PPR-E+ protein in editing function and seed development, and provides insights into the molecular function of mitochondrial CcmB protein in higher plants.

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An artificial channel molecule 1 that mimics the shape and function of the ClC channel selective pore was described. To facilitate the transport of chloride along a unimolecular pathway, anion−π interactions were introduced as the noncovalent driving force. The hourglass-like shape of 1 was constructed with 1,3-alternate tetraoxacalix­[2]­arene­[2]­triazine as the narrowest (central) unit. Two diglycolamine-linked imide arms were tethered as the extending part, and phenylalanine moieties were fixed as the terminal anchoring groups. The ion transport activity was examined by a combination of vesicle and planar bilayer conductance techniques (BLM). The fluorescence analysis on the vesicle indicated that 1 is an efficient chloride transporter with high activity (EC50 = 1.50 μM; 1/lipid = 1:89). The ion channel characteristics were confirmed by BLM measurements, showing an average conductance of 20.8 ± 1.0 pS in symmetric KCl solutions (cis/trans = 1.0 M/1.0 M). Anion/cation selectivity with a permeability ratio P Cl –/P K + = 1.90 in an asymmetric KCl solution (cis/trans = 1.0 M/0.25 M) and anion/anion selectivity with P Cl –/P Br – = 22.83 in a KCl/KBr solution (cis/trans = 1.0 M KCl/1.0 M KBr) were demonstrated.

RNA editing plays an important role in organellar gene expression in plants, and pentatricopeptide repeat (PPR) proteins are involved in this function. Because of its large family size, many PPR proteins are not known for their function and roles in plant growth and development. Through genetic and molecular analyses of the empty pericarp18 (emp18) mutant in maize (Zea mays), we cloned the Emp18 gene, revealed its molecular function, and defined its role in the mitochondrial complex assembly and seed development. Emp18 encodes a mitochondrial-localized DYW-PPR protein. Null mutation of Emp18 arrests embryo and endosperm development at an early stage in maize, resulting in embryo lethality. Mutants are deficient in the cytidine (C)-to-uridine (U) editing at atp6-635 and cox2-449, which converts a Leu to Pro in ATP6 and a Met to Thr in Cox2. The atp6 gene encodes the subunit a of F F -ATPase. The Leu to Pro alteration disrupts an α-helix of subunit a, resulting in a dramatic reduction in assembly and activity of F F -ATPase holoenzyme and an accumulation of free F -subcomplex. These results demonstrate that EMP18 functions in the C-to-U editing of atp6 and cox2, and is essential to mitochondrial biogenesis and seed development in maize.

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Oceanic slab breakoff significantly affects the thermal regime of the lithosphere during continental collision. This often triggers extension‐related mafic magmatism and crustal melting. It is generally accepted that the Neo‐Tethyan lithosphere subducted beneath the southern Lhasa Subterrane, resulting in the formation of the Gangdese magmatic arc. However, the timing of slab breakoff is still disputed, due to a lack of evidence for extension‐related mafic magmatism. In this study, we provide comprehensive age, element and Sr–Nd–Hf isotopic data of mafic dikes, felsic intrusions, and enclaves from the Daju area, southern Lhasa Subterrane. The timing of mafic dikes and granitoids are contemporaneous at circa 57 Ma. The mafic dikes are characterized by high Th/U, and Zr/Y ratios, their geochemistry indicates an intraplate affinity rather than arc magmas. Furthermore, the mafic dikes show strongly variable igneous zircon ɛHf(t), and lower whole‐rock ɛNd(t) than granitoids. This evidence suggests that the mafic dikes represent asthenosphere‐derived melts contaminated by various degrees of ancient lithosphere. However, the granitoids were directly derived from the juvenile lower crust. Given the abrupt decrease in the convergence rate between India and Asia, and the surface uplift and sedimentation cessation in the southern Lhasa Subterrane in the early Cenozoic, the occurrence of synchronous mafic dikes and granitoids is best explained by a slab breakoff model. The occurrence of intraplate‐type magmas likely corresponds to the magmatic expression of the initial stage of Neo‐Tethyan slab breakoff. The slab breakoff concept also explains the onset of the magmatic “flare‐up” and crustal growth after 57 Ma.