Data_Sheet_1_N-Terminal Extension and C-Terminal Domains Are Required for ABCB6/HMT-1 Protein Interactions, Function in Cadmium Detoxification, and Localization to the Endosomal-Recycling System in Caenorhabditis elegans.PDF

<p>The chronic exposure of humans to toxic metals such as cadmium from food and air causes dysfunction of vital organs, neurodegenerative conditions, and cancer. In this regard, members of the ABCB sub-family of the ATP-binding cassette (ABC) transporter superfamily, ABCB6/HMT-1, are acutely required for the detoxification of heavy metals and are present in genomes of many organisms including the nematode worm, Caenorhabditis elegans and humans. We showed previously that C. elegans ABCB6/HMT-1 detoxifies cadmium, copper, and arsenic, and is expressed in liver-like cells, the coelomocytes, head neurons and intestinal cells, which are the cell types that are affected by heavy metal poisoning in humans. The subcellular localization of ABCB6/HMT-1 proteins is unclear. ABCB6/HMT-1 proteins have a distinguishing topology: in addition to one transmembrane domain and one nucleotide-binding domain, they possess a hydrophobic N-terminal extension (NTE) domain encompassing five to six transmembrane spans. The role of the NTE domain in the function of ABCB6/HMT-1 in the native organism remains to be investigated. We used a versatile, multicellular model system, C. elegans, to establish the subcellular localization of ABCB6/HMT-1 and refine its structure-function studies in the native organism. We show that ABCB6/HMT-1 localizes mainly to the apical recycling endosomes and, in part, to early and late endosomes of intestinal cells. We also show that ABCB6/HMT-1 lacking the NTE domain is mistargeted to the plasma membrane and is unable to confer cadmium resistance. Although the NTE domain is essential for ABCB6/HMT-1 interaction with itself, the absence of NTE does not fully prevent this interaction. As a result, ABCB6/HMT-1 lacking the NTE domain, and expressed in wild-type worms or co-expressed with the full-length polypeptide, inactivates and mistargets the full-length ABCB6/HMT-1. We also show that the 43 amino acid residue stretch at the COOH-terminus is required for the ABCB6/HMT-1 interaction with itself and cadmium detoxification function. These results suggest that both NTE and COOH-terminus must be present to allow the protein to interact with itself and confer cadmium resistance. Considering that ABCB6/HMT-1 proteins are highly conserved, this study advances our understanding of how these proteins function in cadmium resistance in different species. Furthermore, these studies uncover the role of the endosomal-recycling system in cadmium detoxification.</p

HMT-1 interacts with itself.

<p><b>A.</b> Schematic representation of the topology of the full-length HMT-1 polypeptide. Based on the predicted topology (TMHMM software, version 2.0), the NH2-terminus is located outside (<i>Lumen</i>), whereas the COOH-terminus is inside (<i>Cytosol</i>). Also shown are the HMT-1 core region (<i>ABC core</i>) consisting of a single transmembrane domain (<i>TMD1</i>) with six transmembrane spans and a single nucleotide binding domain (<i>NBD1</i>). In addition to a core region, HMT-1 possesses the N-terminal extension (<i>NTE</i>), comprised of a membrane spanning domain (<i>TMD0</i>) and a linker domain (<i>L0</i>). <b>B.</b> Full-length HMT-1 was fused at the C-terminus with CubPLV (<i>HMT-Cub</i>) or with NubG at the C- or N-termini (<i>NubG-HMT</i> and <i>HMT-NubG</i>, respectively). The orientation of CubPLV and NubG is based on the predicted topology of HMT-1. <b>C.</b> Protein-protein interactions of HMT-1 as detected by mbSUS. Growth conditions are indicated below each panel; concentrations of yeast cells are indicated on the left. Numbers across the top represent experiments and controls as follows. Interaction tests where HMT-1-CubPLV was used as bait: 2, HMT-Cub + NubG-HMT; 3, HMT-Cub + HMT-NubG; 7, HMT-Cub + KAT1-NubG. Controls for self-activation: 1, HMT-Cub + NubG; 4, Cub + HMT-NubG. Interaction assays using AtKAT1-CubPLV as bait: KAT1-Cub + HMT-NubG (negative control); 6, KAT1-Cub + KAT1-NubG (positive control, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0012938#pone.0012938-Obrdlik1" target="_blank">[27]</a>); 7, HMT-Cub + KAT1-NubG (negative control). Shown are representative results of at least three biological replicates. (SC =  synthetic complete medium; Met  =  methionine; Ade =  adenine; His = histidine). <b>D.</b> HMT-1-Nub confers Cd tolerance. Serial dilutions of yeast expressing pNub or HMT-NubG were as indicated. Concentrations of CdCl₂ in µM are indicated below each experiment. Note the striking growth difference at 75 µM.</p

List of <i>C. elegans</i> strains.

<p>List of <i>C. elegans</i> strains.</p

Enhanced Water Retention Maintains Energy Dissipation in Dehydrated Metal-Coordinate Polymer Networks: Another Role for Fe-Catechol Cross-Links?

The change from wet and soft to dry and hard is a viscoelastic to solid material transition widely displayed in nature, in particular in materials rich in metal-coordinate cross-linking. How metal-coordinate cross-link dynamics contribute to macromolecular material mechanics upon solidification by dehydration remains an open question. Using mussel-inspired Fe-catechol cross-linked polymer hydrogels, we address this question. In addition to a nearly 2-fold increase in stiffness, we find that the presence of Fe-catechol coordination bonds in a dehydrated polymer gel also provides the bulk network with a significantly increased energy dissipation with over three times higher loss factor. We present evidence to suggest that small amounts (∼4 wt %) of locally bound water maintain the dynamic nature of Fe-catechol coordinate cross-links in a dehydrated polymer network. The dehydration-induced polymer material mechanics presented here may provide deeper insights on the biological utilization of metal-coordinate cross-link dynamics as well as inspire new ideas on sustainable materials engineering

The primer sequences used to clone the full-length and truncated CeHMT-1.

<p>The primer sequences used to clone the full-length and truncated CeHMT-1.</p

The acute respiratory exposure by intratracheal instillation of Sprague–Dawley rats with diesel particulate matter induces retinal thickening

<p><i>Context</i>: Adverse health effects of ambient particulate matter (PM) have been demonstrated in humans, mostly in terms of respiratory and cardiovascular events. However, whether ambient particle could affect the eyes had not been fully revealed.</p> <p><i>Objective</i>: This study investigated the effect of acute respiratory exposure to PM on eyes.</p> <p><i>Methods</i>: Diesel exhaust product (DEP) of 200 mg/l was given endotracheally in Sprague–Dawley rats for 1 h (<i>n</i> = 12) and compared to normal control (<i>n</i> = 4). We enucleated eyes and histologically evaluated. Immunohistochemical stains for CD34 (Dako, Glostrup, Denmark, 1:50) and Ki-67 (DakoCytomation, Glostrup, Denmark, 1:150) were performed to evaluate new vessel formation and proliferation activity.</p> <p><i>Results</i>: After endotracheal DEP exposure, the thickness of retina was significantly increased to 258 ± 96 μm in DEP group, while that of control was 113 ± 9 μm (<i>p</i> = 0.025). Among the retinal structure, inner plexiform, inner and outer nuclear and rod/cone cell layers were significantly thickened (<i>p</i> = 0.00, 0.017, 0.004, 0.001, respectively). The outer plexiform layer of DEP group showed a tendency of thickening, but statistically insignificant. The afferent fiber and ganglion cell layer showed no thickness difference between two groups, but prominent capillaries with congestion were noted in DEP group. Neither neovascularization nor increased proliferation was demonstrated on CD34 and Ki-67 immunohistochemical staining in DEP group.</p> <p><i>Conclusion</i>: This study shows that the acute respiratory exposure of ambient PM increased retinal thickness, especially inner plexiform, inner and outer nuclear and rod/cone cell layers. We thought that increase of retinal thickness in DEP group resulted in hypoxia-induced edema.</p

Highly Stable and Tunable n‑Type Graphene Field-Effect Transistors with Poly(vinyl alcohol) Films

The intrinsic p-type behavior of graphene field-effect transistors (FETs) under ambient conditions poses a fundamental challenge for the assembly of complex electronic devices, such as integrated circuits. In this work, we present a protocol for tunable n-type doping of graphene FETs via poly­(vinyl alcohol) (PVA) coating. Using graphene grown by alcohol catalytic chemical vapor deposition, functionalization of the surface by this hydroxyl anion-rich polymer results in an evolution of the FETs from p-type to ambipolar or n-type even under ambient air conditions. The doping level of graphene is strongly related to the PVA film coating parameters, such as solution concentration, hardening temperature, and hardening time. This PVA coating proves to be a simple and stable approach to tuning the Dirac point and doping level of graphene, which is highly desirable and of great significance for the future of graphene-based electronic devices

Co₃V₂O₈ Sponge Network Morphology Derived from Metal–Organic Framework as an Excellent Lithium Storage Anode Material

Metal–organic framework (MOF)-based synthesis of battery electrodes has presntly become a topic of significant research interest. Considering the complications to prepare Co₃V₂O₈ due to the criticality of its stoichiometric composition, we report on a simple MOF-based solvothermal synthesis of Co₃V₂O₈ for use as potential anodes for lithium battery applications. Characterizations by X-ray diffraction, X-ray photoelectron spectroscopy, high resolution electron microscopy, and porous studies revealed that the phase pure Co₃V₂O₈ nanoparticles are interconnected to form a sponge-like morphology with porous properties. Electrochemical measurements exposed the excellent lithium storage (∼1000 mAh g^–1 at 200 mA g^–1) and retention properties (501 mAh g^–1 at 1000 mA g^–1 after 700 cycles) of the prepared Co₃V₂O₈ electrode. A notable rate performance of 430 mAh g^–1 at 3200 mA g^–1 was also observed, and ex situ investigations confirmed the morphological and structural stability of this material. These results validate that the unique nanostructured morphology arising from the use of the ordered array of MOF networks is favorable for improving the cyclability and rate capability in battery electrodes. The synthetic strategy presented herein may provide solutions to develop phase pure mixed metal oxides for high-performance electrodes for useful energy storage applications

Electrochemically Induced Structural Transformation in a γ‑MnO₂ Cathode of a High Capacity Zinc-Ion Battery System

In the present study, an in-depth investigation on the structural transformation in a mesoporous γ-MnO₂ cathode during electrochemical reaction in a zinc-ion battery (ZIB) has been undertaken. A combination of in situ Synchrotron XANES and XRD studies reveal that the tunnel-type parent γ-MnO₂ undergoes a structural transformation to spinel-type Mn­(III) phase (ZnMn₂O₄) and two new intermediary Mn­(II) phases, namely, tunnel-type γ-Zn_<i>x</i>MnO₂ and layered-type L-Zn_<i>y</i>MnO₂, and that these phases with multioxidation states coexist after complete electrochemical Zn-insertion. On successive Zn-deinsertion/extraction, a majority of these phases with multioxidation states is observed to revert back to the parent γ-MnO₂ phase. The mesoporous γ-MnO₂ cathode, prepared by a simple ambient temperature strategy followed by low-temperature annealing at 200 °C, delivers an initial discharge capacity of 285 mAh g^–1 at 0.05 mA cm^–2 with a defined plateau at around 1.25 V vs Zn/Zn²⁺. Ex situ HR-TEM studies of the discharged electrode aided to identify the lattice fringe widths corresponding to the Mn­(III) and Mn­(II) phases, and the stoichiometric composition estimated by ICP analysis appears to be concordant with the in situ findings. Ex situ XRD studies also confirmed that the same electrochemical reaction occurred on repeated discharge/charge cycling. Moreover, the present synthetic strategy offers solutions for developing cost-effective and environmentally safe nanostructured porous electrodes for cheap and eco-friendly batteries

Na₂V₆O₁₆·3H₂O Barnesite Nanorod: An Open Door to Display a Stable and High Energy for Aqueous Rechargeable Zn-Ion Batteries as Cathodes

Owing to their safety and low cost, aqueous rechargeable Zn-ion batteries (ARZIBs) are currently more feasible for grid-scale applications, as compared to their alkali counterparts such as lithium- and sodium-ion batteries (LIBs and SIBs), for both aqueous and nonaqueous systems. However, the materials used in ARZIBs have a poor rate capability and inadequate cycle lifespan, serving as a major handicap for long-term storage applications. Here, we report vanadium-based Na₂V₆O₁₆·3H₂O nanorods employed as a positive electrode for ARZIBs, which display superior electrochemical Zn storage properties. A reversible Zn²⁺-ion (de)­intercalation reaction describing the storage mechanism is revealed using the in situ synchrotron X-ray diffraction technique. This cathode material delivers a very high rate capability and high capacity retention of more than 80% over 1000 cycles, at a current rate of 40C (1C = 361 mA g^–1). The battery offers a specific energy of 90 W h kg^–1 at a specific power of 15.8 KW kg^–1, enlightening the material advantages for an eco-friendly atmosphere