Enantiomeric Discrimination in Insects: The Role of OBPs and ORs

Olfaction is a complex recognition process that is critical for chemical communication in insects. Though some insect species are capable of discrimination between compounds that are structurally similar, little is understood about how this high level of discrimination arises. Some insects rely on discriminating between enantiomers of a compound, demonstrating an ability for highly selective recognition. The role of two major peripheral olfactory proteins in insect olfaction, i.e., odorant-binding proteins (OBPs) and odorant receptors (ORs) has been extensively studied. OBPs and ORs have variable discrimination capabilities, with some found to display highly specialized binding capability, whilst others exhibit promiscuous binding activity. A deeper understanding of how odorant-protein interactions induce a response in an insect relies on further analysis such as structural studies. In this review, we explore the potential role of OBPs and ORs in highly specific recognition, specifically enantiomeric discrimination. We summarize the state of research into OBP and OR function and focus on reported examples in the literature of clear enantiomeric discrimination by these proteins

Mass balance calculations of illicit drugs in Stoke Bardolph Sewage treatment works, United Kingdom

Work encompassed in this study directly measures illicit drug removal rates in laboratory studies. Researchers employed removal rate data in calculating mass balances in sewage works which is an improvement over prior studies where assumptions on removal rates at Sewage Treatment Works were made. The batch tests data enabled determination of degradation of the compounds at different temperatures and times, using various sludge types after characterization. Mass balances for the Stoke Bardolph Sewage Treatment Works were constructed using the removal rate data from the batch studies. Final effluent concentrations of 10.0 ng L-1 (morphine), and 80.0 ng L-1 (6-monoacetylmorphine), were recorded after a total of 8 hour hydraulic times (8 HRT) from an initial influent concentration of 50 mg L-1. A projected influent concentration of morphine (1.4 g L-1) at Stoke Bardolph was derived from back-calculating measured final effluent concentrations using the same mass balance approach

Harnessing microbial volatiles to replace pesticides and fertilizers

Global agricultural systems are under increasing pressure to deliver sufficient, healthy food for a growing population. Seasonal inputs, including synthetic pesticides and fertilizers, are applied to reduce losses by pathogens, and enhance crop biomass, although their production and application can also incur several economic and environmental penalties. New solutions are therefore urgently required to enhance crop yield whilst reducing dependence on these seasonal inputs. Volatile Organic Compounds (VOCs) produced by soil microorganisms may provide alternative solutions, due to their ability to inhibit fungal pathogens, induce plant resistance against pathogens, and enhance plant growth promotion. This review will highlight recent advances in our understanding of these biological activities of microbial VOCs (mVOCs), providing perspectives on research required to develop them into viable alternatives to current unsustainable seasonal inputs. This can identify potential new avenues for mVOC research and stimulate discussion across the academic community 25 and agri-business sector

Degradation of some illicit compounds in sewage sludge batch tests

The batch tests enabled determination of the degradation of the compounds at different temperatures and times, using various sludge types after characterization. Removal rates of cocaine (91.0%), benzoylecgonine (90.6%), heroin (97.9%), morphine (99.7%), 6 monoacetylmorphine (93.3%) and diazepam (99.7%) were measured after 3 hours equilibration; partition coefficients (Kd) for these six substances ranged from 1.2 – 68.1 Kg L-1. The degradation of compounds at 19 ± 0.5o C was relatively greater but it still occurred slowly at 4 ± 0.5o C, at between 5 and 10%. Work encompassed in this study directly measures illicit drug removal rates in laboratory studies for the first time. The application of batch studies in calculating removal rates in sewage works is an improvement over prior studies where assumptions on removal rates at STW were made

Fate of drugs and their metabolites in the environment

The individual use of these pharmacologically active substances which generate great but underappreciated levels of other toxicologically potent and associated bioactive metabolites through purposeful and inadvertent discharge to the environment via excreta and by illegal disposal has become a global issue. This work reviews aspects of drugs occurrence, metabolism, transport routes, stability, analysis and environmental distribution of these emerging contaminants and highlights current developments in investigating and monitoring their fate and potential effects in aquatic environments. Gas chromatography-mass spectrometry (GCMS) and high performance liquid chromatography are the preferred methods for trace drugs analysis in wastewaters as their measurements depend largely on successful application of a fast and reliable method for qualitative and quantitative determination. The application of this method to the actual influents, effluents, sludge and environmental sediments from sewage treatment works (STWs) allows the assessment of drugs content and the extent at which STW helps in the transport of these pollutants (via different media) into the environment. The capability is also outlined for furthering our understanding of fate and behaviour of drugs with particular reference to illicit drugs, abused pharmaceuticals and environmental processes in our quest to understand the overall issues of drugs and make available exposure data for the aquatic realm

Novel and holistic approaches are required to realise allelopathic potential for weed management

Allelopathy, i.e. plant-plant inhibition via the release of secondary metabolites into the environment, has potential for the management of weeds by circumventing herbicide resistance. However, mechanisms underpinning allelopathy are notoriously difficult to elucidate, hindering real-world application either in the form of commercial bioherbicides or allelopathic crops. Such limited application is exemplified by evidence of limited knowledge of the potential benefits of allelopathy among end-users. Here, we examine potential applications of this phenomenon, paying attention to novel approaches and influential factors requiring greater consideration, with the intention of improving the reputation and uptake of allelopathy. Avenues to facilitate more effective allelochemical discovery are also considered, with a view to stimulating the identification of new compounds and allelopathic species. Synthesis and Applications: We conclude that tackling increasing weed pressure on agricultural productivity would benefit from greater integration of the phenomenon of allelopathy, which in turn would be greatly served by a multi-disciplinary and exhaustive approach, not just through more effective isolation of the interactions involved, but through greater consideration of factors which may influence them in the field, facilitating optimisation of their benefits for weed management

The Automated Root Exudate System (ARES): a method to apply solutes at regular intervals to soils in the field.

Root exudation is a key component of nutrient and carbon dynamics in terrestrial ecosystems. Exudation rates vary widely by plant species and environmental conditions, but our understanding of how root exudates affect soil functioning is incomplete, in part because there are few viable methods to manipulate root exudates in situ. To address this, we devised the Automated Root Exudate System (ARES), which simulates increased root exudation by applying small amounts of labile solutes at regular intervals in the field. The ARES is a gravity-fed drip irrigation system comprising a reservoir bottle connected via a timer to a micro-hose irrigation grid covering c. 1 m2; 24 drip-tips are inserted into the soil to 4-cm depth to apply solutions into the rooting zone. We installed two ARES subplots within existing litter removal and control plots in a temperate deciduous woodland. We applied either an artificial root exudate solution (RE) or a procedural control solution (CP) to each subplot for 1 min day-1 during two growing seasons. To investigate the influence of root exudation on soil carbon dynamics, we measured soil respiration monthly and soil microbial biomass at the end of each growing season. The ARES applied the solutions at a rate of c. 2 L m-2 week-1 without significantly increasing soil water content. The application of RE solution had a clear effect on soil carbon dynamics, but the response varied by litter treatment. Across two growing seasons, soil respiration was 25% higher in RE compared to CP subplots in the litter removal treatment, but not in the control plots. By contrast, we observed a significant increase in microbial biomass carbon (33%) and nitrogen (26%) in RE subplots in the control litter treatment. The ARES is an effective, low-cost method to apply experimental solutions directly into the rooting zone in the field. The installation of the systems entails minimal disturbance to the soil and little maintenance is required. Although we used ARES to apply root exudate solution, the method can be used to apply many other treatments involving solute inputs at regular intervals in a wide range of ecosystems

Optical properties of earth-abundant semiconductors for renewable energy

The research described primarily addresses the experimental determination of optical properties in emerging photovoltaic (PV) materials. Work proceeds with two specific aims: to consolidate and clarify experimental practice on the determination of optical properties in polycrystalline systems, then to apply any findings in investigations of the relatively unstudied semiconductors copper nitride and copper antimony sulphide, which fulfil many of the requirements for next generation PV materials: earth-abundance, scalability, bipolar doping, near-optimal band gaps, strong absorption, and beneficial transport properties. While the literature already offers extensive theoretical treatments of optical phenomena and the propagation of light, somewhat less-discussed is the task of practical determination of optical properties via the inversion of measured spectra. In the most general cases inversion may be non-trivial even for simple systems: no global solutions may exist. Furthermore, emerging thin-film photovoltaic technologies may utilise material which, whilst commercially attractive, may not be suited for study by reflection/transmission spectroscopy, while researchers often choose rather elementary spectral reduction approaches where more desirable alternatives exist. After reviewing various models, methods and issues, a self-consistent code is described which determines absorption spectra with improved accuracy. Practical work on copper nitride Cu3N and copper antimony sulphide CuSbS2 comprises experimental and first-principles investigations. Optical studies via FTIR and spectroscopic ellipsometry establish absorption and refractive index spectra for both materials; in each case, strong absorption (exceeding 6e4/cm) is found just beyond the absorption onset. Direct band gaps, average phonon energies and Bose-Einstein electron-phonon interaction strengths are determined by fitting the temperature-dependence of the absorption edge. Atypically small temperature-dependence of the direct gap is found in Cu3N (along with an optically-active TO-phonon mode), whilst in CuSbS2 a possible excitonic state is seen at low-temperature just above the absorption onset; a symmetry analysis suggests distinctly enhanced absorption for this state: further work with oriented single crystals is proposed. Structural investigations by x-ray diffraction and Rietveld or Pawley refinement find Cu3N and CuSbS2 geometries broadly consistent with prior findings. Credible thermal expansion is finally established in Cu3N between 4.2 and 280 K by temperature-dependent XRD; very little expansion is seen below 100 K: further synchrotron work is proposed. A quasi-harmonic model estimates the Cu3N zero Kelvin lattice parameter, Debye temperature and average Gruneisen parameter. Density-functional theory calculations on Cu3N and CuSbS2 suggest band structures and symmetries, band gap evolution, selection rules for optical dipole transitions, valence-band density of states (supported via x-ray photoelectron spectroscopy), and evaluate potential structural distortions: such as perovskite rigid-unit modes

Scents and sex: insect pheromones

Pheromones are chemical signals (semiochemicals) that act between members of the same species, sex pheromones being the signals that facilitate sexual reproduction. Many organisms use such semiochemicals, but it is insects to which the main research attention has been directed. This article will therefore concentrate on the insect sex pheromones