A particular challenge for nanotoxicology is the evaluation of the biological fate and toxicity of nanomaterials that dissolve in aqueous fluids. Zinc oxide nanomaterials are of particular concern ...because dissolution leads to release of the toxic divalent zinc ion. Although zinc ions have been implicated in ZnO cytotoxicity, direct identification of the chemical form of zinc taken up by cells exposed to ZnO nanoparticles, and its intracellular fate, has not yet been achieved. We combined high resolution X-ray spectromicroscopy and high elemental sensitivity X-ray microprobe analyses to determine the fate of ZnO and less soluble iron-doped ZnO nanoparticles following exposure to cultures of human bronchial epithelial cells, BEAS-2B. We complemented two-dimensional X-ray imaging methods with atomic force microscopy of cell surfaces to distinguish between nanoparticles that were transported inside the cells from those that adhered to the cell exterior. The data suggest cellular uptake of ZnO nanoparticles is a mechanism of zinc accumulation in cells. Following uptake, ZnO nanoparticles dissolved completely generating intracellular Zn2+ complexed by molecular ligands. These results corroborate a model for ZnO nanoparticle toxicity that is based on nanoparticle uptake followed by intracellular dissolution.
Abstract
Quantum sensors have attracted broad interest in the quest towards sub-micronscale NMR spectroscopy. Such sensors predominantly operate at low magnetic fields. Instead, however, for high ...resolution spectroscopy, the high-field regime is naturally advantageous because it allows high absolute chemical shift discrimination. Here we demonstrate a high-field spin magnetometer constructed from an ensemble of hyperpolarized
13
C nuclear spins in diamond. They are initialized by Nitrogen Vacancy (NV) centers and protected along a transverse Bloch sphere axis for minute-long periods. When exposed to a time-varying (AC) magnetic field, they undergo secondary precessions that carry an imprint of its frequency and amplitude. For quantum sensing at 7T, we demonstrate detection bandwidth up to 7 kHz, a spectral resolution < 100mHz, and single-shot sensitivity of 410pT
$$/\sqrt{{{\rm{Hz}}}$$
/
Hz
. This work anticipates opportunities for microscale NMR chemical sensors constructed from hyperpolarized nanodiamonds and suggests applications of dynamic nuclear polarization (DNP) in quantum sensing.
1. The question of when to monitor and when to act is fundamental to applied ecology and notoriously difficult to answer. Value of information (VOI) theory holds great promise to help answer this ...question for many management problems. However, VOI theory in applied ecology has only been demonstrated in singledecision problems and has lacked explicit links between monitoring and management costs. 2. Here, we present an extension of VOI theory for solving multi-unit decisions of whether to monitor before managing, while explicitly accounting for monitoring costs. Our formulation helps to choose the optimal monitoring/management strategy among groups of management units (e.g. species, habitat patches) and can be used to examine the benefits of partial and repeat monitoring. 3. To demonstrate our approach, we use case-simulated studies of single-species protection that must choose among potential habitat areas, and classification and management of multiple species threatened with extinction. We provide spreadsheets and code to illustrate the calculations and facilitate application. Our case studies demonstrate the utility of predicting the number of units with a given outcome for problems with probabilities of discrete states and the efficiency of having a flexible approach to manage according to monitoring outcomes. 4. Synthesis and applications. The decision to act or gather more information can have serious consequences for management. No decision, including the decision to monitor, is risk-free. Our multi-unit expansion of Value of Information theory can reduce the risk in monitoring/acting decisions for many applied ecology problems. While our approach cannot account for the potential value of discovering previously unknown threats or ecological processes via monitoring programmes, it can provide quantitative guidance on whether to monitor before acting, and which monitoring/management actions are most likely to meet management objectives.
Nanoparticle aggregation affects the sorption, retention, and speciation of metals differently based on the mechanism of aggregation (pH, ionic strength, drying, freezing).
Adsorption at the ...mineral–water interface is an important process governing metal ion concentration and mobility in aqueous systems. Ferric iron oxyhydroxide nanoparticles possess a large capacity for the adsorption of heavy metals but quantification of metal uptake and sequestration is challenging due to the tendency of natural nanoparticles to aggregate in natural waters. We studied the effects of aggregation via pH, ionic strength, drying, and freezing on the uptake and release of copper from ferrihydrite nanoparticles employing small-angle X-ray scattering (SAXS) studies of aggregate morphology, macroscopic Cu(II) sorption and desorption batch experiments, and extended X-ray absorption fine structure (EXAFS) spectroscopic studies of copper sorption geometries. Results show that the mechanism of aggregation has a large effect upon aggregate morphology and consequently on the net sorption/retention of ions from solution. While aggregation reduces the total amount of copper that can be adsorbed, it also may introduce physical constraints to desorption and/or increased proportions of higher strength binding sites that lead to greater retention, and hence more effective sequestration, of metal ion contaminants.
The phases and stability of ferric iron products formed early during neutralization of acid mine drainage waters remain largely unknown. In this work, we used in situ and time-resolved quick-scanning ...X-ray absorption spectroscopy and X-ray diffraction to study products formed between 4 min and 1 h after ferric iron sulfate solutions were partially neutralized by addition of NaHCO3 (HCO3 –/Fe3+ < 3). When HCO3 –/Fe3+ = 0.5 and 0.6 (initial pH ∼ 2.1 and 2.2, respectively), the only large species formed were sulfate-complexed ferrihydrite-like molecular clusters that were stable throughout the duration of the experiment. When HCO3 –/Fe3+ = 1 (initial pH ∼ 2.5), ferrihydrite-like molecular clusters formed initially, but most later converted to schwertmannite. In contrast, when HCO3 –/Fe3+ = 2 (initial pH ∼ 2.7), schwertmannite and larger ferrihydrite particles formed immediately upon neutralization. However, the ferrihydrite particles subsequently converted to schwertmannite. The schwertmannite particles formed under both conditions aggregated extensively with increasing time. This work provides new insight into the formation, stability and reactivity of some early products that may form during the neutralization of natural acid mine drainage.
Urbanization is an important component of global change. Urbanization affects species interactions, but the evolutionary implications are rarely studied. We investigate the evolutionary consequences ...of a common pattern: the loss of high trophic‐level species in urban areas. Using a gall‐forming fly, Eurosta solidaginis, and its natural enemies that select for opposite gall sizes, we test for patterns of enemy loss, selection, and local adaptation along five urbanization gradients. Eurosta declined in urban areas, as did predation by birds, which preferentially consume gallmakers that induce large galls. These declines were linked to changes in habitat availability, namely reduced forest cover in urban areas. Conversely, a parasitoid that attacks gallmakers that induce small galls was unaffected by urbanization. Changes in patterns of attack by birds and parasitoids resulted in stronger directional selection, but loss of stabilizing selection in urban areas, a pattern which we suggest may be general. Despite divergent selective regimes, gall size did not very systematically with urbanization, suggesting but not conclusively demonstrating that environmental differences, gene flow, or drift, may have prevented the adaptive divergence of phenotypes. We argue that the evolutionary effects of urbanization will have predictable consequences for patterns of species interactions and natural selection.
Extracellular electron transfer (EET) between microbes and iron minerals, and syntrophically between species, is a widespread process affecting biogeochemical cycles and microbial ecology. The ...distribution of this capacity among microbial taxa, and the thermodynamic controls on EET in complex microbial communities, are not fully known. Microbial electrochemical cells (MXCs), in which electrodes serve as the electron acceptor or donor, provide a powerful approach to enrich for organisms capable of EET and to study their metabolism. We used MXCs coupled with genome-resolved metagenomics to investigate the capacity for EET in microorganisms present in a well-studied aquifer near Rifle, CO. Electroactive biofilms were established and maintained for almost 4 years on anodes poised mostly at -0.2 to -0.25 V vs. SHE, a range that mimics the redox potential of iron-oxide minerals, using acetate as the sole carbon source. Here we report the metagenomic characterization of anode-biofilm and planktonic microbial communities from samples collected at timepoints across the study period. From two biofilm and 26 planktonic samples we reconstructed draft-quality and near-complete genomes for 84 bacteria and 2 archaea that represent the majority of organisms present. A novel Geobacter sp. with at least 72 putative multiheme c-type cytochromes (MHCs) was the dominant electrode-attached organism. However, a diverse range of other electrode-associated organisms also harbored putative MHCs with at least 10 heme-binding motifs, as well as porin-cytochrome complexes and e-pili, including Actinobacteria, Ignavibacteria, Chloroflexi, Acidobacteria, Firmicutes, Beta- and Gammaproteobacteria. Our results identify a small subset of the thousands of organisms previously detected in the Rifle aquifer that may have the potential to mediate mineral redox transformations.
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