A Whole-Cell Biosensor for the Detection of Gold

Geochemical exploration for gold (Au) is becoming increasingly important to the mining industry. Current processes for Au analyses require sampling materials to be taken from often remote localities. Samples are then transported to a laboratory equipped with suitable analytical facilities, such as Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) or Instrumental Neutron Activation Analysis (INAA). Determining the concentration of Au in samples may take several weeks, leading to long delays in exploration campaigns. Hence, a method for the on-site analysis of Au, such as a biosensor, will greatly benefit the exploration industry. The golTSB genes from Salmonella enterica serovar typhimurium are selectively induced by Au(I/III)-complexes. In the present study, the golTSB operon with a reporter gene, lacZ, was introduced into Escherichia coli. The induction of golTSB::lacZ with Au(I/III)-complexes was tested using a colorimetric β-galactosidase and an electrochemical assay. Measurements of the β-galactosidase activity for concentrations of both Au(I)- and Au(III)-complexes ranging from 0.1 to 5 µM (equivalent to 20 to 1000 ng g⁻¹ or parts-per-billion (ppb)) were accurately quantified. When testing the ability of the biosensor to detect Au(I/III)-complexes_(aq) in the presence of other metal ions (Ag(I), Cu(II), Fe(III), Ni(II), Co(II), Zn, As(III), Pb(II), Sb(III) or Bi(III)), cross-reactivity was observed, i.e. the amount of Au measured was either under- or over-estimated. To assess if the biosensor would work with natural samples, soils with different physiochemical properties were spiked with Au-complexes. Subsequently, a selective extraction using 1 M thiosulfate was applied to extract the Au. The results showed that Au could be measured in these extracts with the same accuracy as ICP-MS (P<0.05). This demonstrates that by combining selective extraction with the biosensor system the concentration of Au can be accurately measured, down to a quantification limit of 20 ppb (0.1 µM) and a detection limit of 2 ppb (0.01 µM).     

Relationship between Oscillatory Neuronal Activity during Reward Processing and Trait Impulsivity and Sensation Seeking

Background

The processing of reward and punishment stimuli in humans appears to involve brain oscillatory activity of several frequencies, probably each with a distinct function. The exact nature of associations of these electrophysiological measures with impulsive or risk-seeking personality traits is not completely clear. Thus, the aim of the present study was to investigate event-related oscillatory activity during reward processing across a wide spectrum of frequencies, and its associations with impulsivity and sensation seeking in healthy subjects.

Methods

During recording of a 32-channel EEG 22 healthy volunteers were characterized with the Barratt Impulsiveness and the Sensation Seeking Scale and performed a computerized two-choice gambling task comprising different feedback options with positive vs. negative valence (gain or loss) and high or low magnitude (5 vs. 25 points).

Results

We observed greater increases of amplitudes of the feedback-related negativity and of activity in the theta, alpha and low-beta frequency range following loss feedback and, in contrast, greater increase of activity in the high-beta frequency range following gain feedback. Significant magnitude effects were observed for theta and delta oscillations, indicating greater amplitudes upon feedback concerning large stakes. The theta amplitude changes during loss were negatively correlated with motor impulsivity scores, whereas alpha and low-beta increase upon loss and high-beta increase upon gain were positively correlated with various dimensions of sensation seeking.

Conclusions

The findings suggest that the processing of feedback information involves several distinct processes, which are subserved by oscillations of different frequencies and are associated with different personality traits.     

Donor–Acceptor Shape Matching Drives Performance in Photovoltaics

While the demonstrated power conversion efficiency of organic photovoltaics (OPVs) now exceeds 10%, new design rules are required to tailor interfaces at the molecular level for optimal exciton dissociation and charge transport in higher efficiency devices. We show that molecular shape‐complementarity between donors and acceptors can drive performance in OPV devices. Using core hole clock (CHC) X‐ray spectroscopy and density functional theory (DFT), we compare the electronic coupling, assembly, and charge transfer rates at the interface between C₆₀ acceptors and flat‐ or contorted‐hexabenzocorone (HBC) donors. The HBC donors have similar optoelectronic properties but differ in molecular contortion and shape matching to the fullerene acceptors. We show that shape‐complementarity drives self‐assembly of an intermixed morphology with a donor/acceptor (D/A) ball‐and‐socket interface, which enables faster electron transfer from HBC to C₆₀. The supramolecular assembly and faster electron transfer rates in the shape complementary heterojunction lead to a larger active volume and enhanced exciton dissociation rate. This work provides fundamental mechanistic insights on the improved efficiency of organic photovoltaic devices that incorporate these concave/convex D/A materials.     

Vibrio cholerae Evades Neutrophil Extracellular Traps by the Activity of Two Extracellular Nucleases

The Gram negative bacterium Vibrio cholerae is the causative agent of the secretory diarrheal disease cholera, which has traditionally been classified as a noninflammatory disease. However, several recent reports suggest that a V. cholerae infection induces an inflammatory response in the gastrointestinal tract indicated by recruitment of innate immune cells and increase of inflammatory cytokines. In this study, we describe a colonization defect of a double extracellular nuclease V. cholerae mutant in immunocompetent mice, which is not evident in neutropenic mice. Intrigued by this observation, we investigated the impact of neutrophils, as a central part of the innate immune system, on the pathogen V. cholerae in more detail. Our results demonstrate that V. cholerae induces formation of neutrophil extracellular traps (NETs) upon contact with neutrophils, while V. cholerae in return induces the two extracellular nucleases upon presence of NETs. We show that the V. cholerae wild type rapidly degrades the DNA component of the NETs by the combined activity of the two extracellular nucleases Dns and Xds. In contrast, NETs exhibit prolonged stability in presence of the double nuclease mutant. Finally, we demonstrate that Dns and Xds mediate evasion of V. cholerae from NETs and lower the susceptibility for extracellular killing in the presence of NETs. This report provides a first comprehensive characterization of the interplay between neutrophils and V. cholerae along with new evidence that the innate immune response impacts the colonization of V. cholerae in vivo. A limitation of this study is an inability for technical and physiological reasons to visualize intact NETs in the intestinal lumen of infected mice, but we can hypothesize that extracellular nuclease production by V. cholerae may enhance survival fitness of the pathogen through NET degradation.     

Multiple Delivery of siRNA against Endoglin into Murine Mammary Adenocarcinoma Prevents Angiogenesis and Delays Tumor Growth

Endoglin is a transforming growth factor-β (TGF- β) co-receptor that participates in the activation of a signaling pathway that mediates endothelial cell proliferation and migration in angiogenic tumor vasculature. Therefore, silencing of endoglin expression is an attractive approach for antiangiogenic therapy of tumors. The aim of our study was to evaluate the therapeutic potential of small interfering RNA (siRNA) molecules against endoglin in vitro and in vivo. Therapeutic potential in vitro was assessed in human and murine endothelial cells (HMEC-1, 2H11) by determining endoglin expression level, cell proliferation and tube formation. In vivo, the therapeutic potential of siRNA molecules was evaluated in TS/A mammary adenocarcinoma growing in BALB/c mice. Results of our study showed that siRNA molecules against endoglin have a good antiangiogenic therapeutic potential in vitro, as expression of endoglin mRNA and protein levels in mouse and human microvascular endothelial cells after lipofection were efficiently reduced, which resulted in the inhibition of endothelial cell proliferation and tube formation. In vivo, silencing of endoglin with triple electrotransfer of siRNA molecules into TS/A mammary adenocarcinoma also significantly reduced the mRNA levels, number of tumor blood vessels and the growth of tumors. The obtained results demonstrate that silencing of endoglin is a promising antiangiogenic therapy of tumors that could not be used as single treatment, but as an adjunct to the established cytotoxic treatment approaches.     

Interactions of Archaeal Chromatin Proteins Alba1 and Alba2 with Nucleic Acids

Background

Architectural proteins have important roles in compacting and organising chromosomal DNA. There are two potential histone counterpart peptide sequences (Alba1 and Alba2) in the Aeropyrum pernix genome (APE1832.1 and APE1823).

Methodology/Principal Findings

These two peptides were expressed and their interactions with various DNAs were studied using a combination of various experimental techniques: surface plasmon resonance, UV spectrophotometry, circular dichroism–spectropolarimetry, gel-shift assays, and isothermal titration calorimetry.

Conclusions/Significance

Our data indicate that there are significant differences in the properties of the Alba1 and Alba2 proteins. Both of these Alba proteins can thermally stabilise DNA polynucleotides, as seen from UV melting curves. Alba2 and equimolar mixtures of Alba1/Alba2 have greater effects on the thermal stability of poly(dA-dT).poly(dA-dT). Surface plasmon resonance sensorgrams for binding of Alba1, Alba2, and equimolar mixtures of Alba1/Alba2 to DNA oligonucleotides show different binding patterns. Circular dichroism indicates that Alba2 has a less-ordered secondary structure than Alba1. The secondary structures of the Alba proteins are not significantly influenced by DNA binding, even at high temperatures. Based on these data, we conclude that Alba1, Alba2, and equimolar mixtures of Alba1/Alba2 show different properties in their binding to various DNAs.     

Differential Regulation of Matrix-Metalloproteinases and Their Tissue Inhibitors in Patients with Aneurysmal Subarachnoid Hemorrhage

Background

Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are involved in vascular remodeling, (neuro)inflammation, blood-brain barrier breakdown and neuronal apoptosis. Proinflammatory mechanisms are suggested to play an important role during early brain injury and cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH). This study aimed to analyze MMP-3, MMP-9, TIMP-1 and TIMP-3 in patients with SAH and their respective association with cerebral vasospasm (CVS).

Methods

Blood samples were collected in 20 SAH patients on days 1 to 7, 9, 11, 13 and 15 and 20 healthy age and gender matched volunteers. Serum MMPs and TIMPs were analyzed using enzyme-linked immunosorbent assay. Doppler sonographic CVS was defined as a mean blood flow velocity above 120 cm/sec in the middle cerebral artery. When discharged from hospital and at 6 month follow-up neurological outcome was evaluated using the Glasgow Outcome Score and the modified Rankin Scale.

Results

MMP-9 was higher in SAH patients compared to healthy controls (p<0.001). Patients with CVS (n = 11) had elevated MMP-9 serum levels compared to patients without CVS (n = 9, p<0.05). Higher MMP-9 was observed in the presence of cerebral ischemia associated with cerebral vasospasm (p<0.05). TIMP-1 was increased in patients with SAH on day 4 (p<0.05). There was an imbalance of the MMP-9/TIMP-1 ratio in favor of MMP-9 in SAH patients, in particular those with CVS (p<0.001). MMP-3 and TIMP-3 were significantly lower in SAH patients throughout day 4 and day 7, respectively (p<0.05). We did not find an association between MMP-, TIMP levels and neurological outcome after 6 months.

Conclusions

MMP-3 and -9 are differentially regulated in SAH patients with both enzymes showing peak levels correlating with the development of CVS. The inhibitors TIMP-1 and -3 were low during the acute phase after SAH and increased later on which might suggest a preponderance of pro-inflammatory mechanisms.     

Transcription profiling during the cell cycle shows that a subset of Polycomb-targeted genes is upregulated during DNA replication

Genome-wide gene expression analyses of the human somatic cell cycle have indicated that the set of cycling genes differ between primary and cancer cells. By identifying genes that have cell cycle dependent expression in HaCaT human keratinocytes and comparing these with previously identified cell cycle genes, we have identified three distinct groups of cell cycle genes. First, housekeeping genes enriched for known cell cycle functions; second, cell type-specific genes enriched for HaCaT-specific functions; and third, Polycomb-regulated genes. These Polycomb-regulated genes are specifically upregulated during DNA replication, and consistent with being epigenetically silenced in other cell cycle phases, these genes have lower expression than other cell cycle genes. We also find similar patterns in foreskin fibroblasts, indicating that replication-dependent expression of Polycomb-silenced genes is a prevalent but unrecognized regulatory mechanism.     

Adding parasites to the guppy-predation story: insights from field surveys

Studies of phenotypic variation in nature often consider only a single potential selective agent. In such cases, it remains an open question as to whether variation attributed to that single measured agent might be influenced by some other unmeasured agent. Previous research has shown that phenotypic variation in the Trinidadian guppy (Poecilia reticulata) is strongly influenced by predation regime, and we here ask whether parasitism might represent an additional important selective agent shaping this variation. We performed a field survey of 26 natural guppy populations of known predation regime in northern Trinidad. We quantified levels of parasitism of guppies by the monogenean ecotoparasite, Gyrodactylus, and examined whether this parasite was associated with guppy body size or male colour. Spatial variation in Gyrodactylus parasitism was consistent between years, and parasite prevalence was generally, but not always, higher at high-predation sites than at low-predation sites. Consistent with previous work, predation regime was related to guppy size and some aspects of male colour, whereas parasitism showed few and only minor associations with the same traits. Moreover, a consideration of parasitism did not alter any interpretations regarding associations between guppy traits and predation regimes. These results suggest that parasitism, at least as quantified in the present study, does not play a major role in shaping variation in guppy body size or colour. Nevertheless, considerable variation in these traits, even within a predation regime, suggests the likely importance of other selective agents beyond just predation regime.     

The age of terrestrial carbon export and rainfall intensity in a temperate river headwater system

Riverine dissolved organic carbon (DOC) supports the production of estuaries and coastal ecosystems, constituting one of the most actively recycled pools of the global carbon cycle. A substantial proportion of DOC entering oceans is highly aged, but its origins remain unclear. Significant fluxes of old DOC have never been observed in temperate headwaters where terrestrial imports take place. Here, we studied the radiocarbon age of DOC in three streams draining forested headwater catchments of the river Mulde (Ore Mountains, Germany). In a 4 week summer precipitation event DOC aged at between 160 and 270 years was delivered into the watershed. In one stream, the DOC was modern but depleted in radiocarbon compared to other hydrological conditions. The yield was substantial and corresponded to 20–52 % of the annual DOC yields in wet and dry years, respectively. The analysis of long-term data suggested that the DOC export in extreme precipitation events added to the annual yield and was not compensated for by lower exports in remaining periods. We conclude that climate change, along with additional processes associated with human activities, channels old soil carbon into more rapidly cycled carbon pools of the hydrosphere.