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Malathion is a commercially available insecticide that functions by acting as an acetylcholinesterase inhibitor. Of significant concern, if left in the environment, some of the products observed from the degradation of malathion can function as more potent toxins than the parent compound. Accordingly, there are numerous studies revolving around possible degradation strategies to remove malathion from various environmental media. One of the possible approaches is the degradation of malathion by OH˙ radicals which could be produced from both artificial and biological means in the environment. While there is plenty of evidence that OH˙ does in fact degrade malathion, there is little understanding of the underlying mechanism by which OH˙ reacts with malathion. Moreover, it is not known how competitive the radical degradation pathway is with analogous alkaline degradation pathways. Even less is known about the reaction of additional OH˙ radicals with the degradation byproducts themselves. Herein, we demonstrate that OH˙ induced degradation pathways have variable competitiveness with OH- driven degradation pathways and, in some cases, produce quite different reactivity.

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We report new ruthenium complexes bearing the lipophilic bathophenanthroline (BPhen) ligand and dihydroxybipyridine (dhbp) ligands which differ in the placement of the OH groups ([(BPhen)2 Ru(n,n'-dhbp)]Cl2 with n = 6 and 4 in 1A and 2A , respectively). Full characterization data are reported for 1A and 2A and single crystal X-ray diffraction for 1A . Both 1A and 2A are diprotic acids. We have studied 1A , 1B , 2A , and 2B (B = deprotonated forms) by UV-vis spectroscopy and 1 photodissociates, but 2 is light stable. Luminescence studies reveal that the basic forms have lower energy 3 MLCT states relative to the acidic forms. Complexes 1A and 2A produce singlet oxygen with quantum yields of 0.05 and 0.68, respectively, in acetonitrile. Complexes 1 and 2 are both photocytotoxic toward breast cancer cells, with complex 2 showing EC50 light values as low as 0.50 µM with PI values as high as >200 vs. MCF7. Computational studies were used to predict the energies of the 3 MLCT and 3 MC states. An inaccessible 3 MC state for 2B suggests a rationale for why photodissociation does not occur with the 4,4'-dhbp ligand. Low dark toxicity combined with an accessible 3 MLCT state for 1 O2 generation explains the excellent photocytotoxicity of 2.

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Malathion is a commercially available insecticide that functions by acting as an acetylcholinesterase inhibitor. Of more significant concern, if left in the environment, some of the products observed from the degradation of malathion can function as more potent toxins than the parent compound. These compounds may threaten human life if they are present in high quantities during operation in contaminated or industrial areas. Several experimental studies have been performed to elucidate the possible degradation products of malathion under various conditions to probe both the application of potential remediation methods and the environmental fate of the degradation products. However, only limited computational studies have been reported to delineate the mechanism by which malathion degrades under environmental conditions and how these degradation mechanisms are intertwined with one another. Herein, M06-2X DFT computations were employed to develop comprehensive degradation pathways from the parent malathion compound to a multitude of experimentally observed degradation products. These data corroborate experimental observations that multiple degradation pathways (ester hydrolysis and elimination) are in competition with each other, and the end-products can therefore be influenced by environmental factors such as temperature. Furthermore, the products resulting from any of the initial degradation pathways (ester hydrolysis, elimination, or P-S hydrolysis) can continue to degrade under the same conditions into compounds that are also reported to be toxic.

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Ruthenium complexes bearing protic diimine ligands are cytotoxic to certain cancer cells upon irradiation with blue light. Previously reported complexes of the type [(N,N)2Ru(6,6'-dhbp)]Cl2 with 6,6'-dhbp = 6,6'-dihydroxybipyridine and N,N = 2,2'-bipyridine (bipy) (1A), 1,10-phenanthroline (phen) (2A), and 2,3-dihydro-[1,4]dioxino[2,3-f][1,10]phenanthroline (dop) (3A) show EC50 values as low as 4 µM (for 3A) vs breast cancer cells upon blue light irradiation ( Inorg. Chem. 2017, 56, 7519). Herein, subscript A denotes the acidic form of the complex bearing OH groups, and B denotes the basic form bearing O- groups. This photocytotoxicity was originally attributed to photodissociation, but recent results suggest that singlet oxygen formation is a more plausible cause of photocytotoxicity. In particular, bulky methoxy substituents enhance photodissociation but these complexes are nontoxic ( Dalton Trans 2018, 47, 15685). Cellular studies are presented herein that show the formation of reactive oxygen species (ROS) and apoptosis indicators upon treatment of cells with complex 3A and blue light. Singlet oxygen sensor green (SOSG) shows the formation of 1O2 in cell culture for cells treated with 3A and blue light. At physiological pH, complexes 1A-3A are deprotonated to form 1B-3B in situ. Quantum yields for 1O2 (ϕΔ) are 0.87 and 0.48 for 2B and 3B, respectively, and these are an order of magnitude higher than the quantum yields for 2A and 3A. The values for Ï•Δ show an increase with 6,6'-dhbp derived substituents as follows: OMe < OH < O-. TD-DFT studies show that the presence of a low lying triplet metal-centered (3MC) state favors photodissociation and disfavors 1O2 formation for 2A and 3A (OH groups). However, upon deprotonation (O- groups), the 3MLCT state is accessible and can readily lead to 1O2 formation, but the dissociative 3MC state is energetically inaccessible. The changes to the energy of the 3MLCT state upon deprotonation have been confirmed by steady state luminescence experiments on 1A-3A and their basic analogs, 1B-3B. This energy landscape favors 1O2 formation for 2B and 3B and leads to enhanced toxicity for these complexes under physiological conditions. The ability to convert readily from OH to O- groups allowed us to investigate an electronic change that is not accompanied by steric changes in this fundamental study.

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Polycyclic aromatic azaborines have potential applications as luminophores, novel fluorescent materials, organic light-emitting diodes, and fluorescent sensors. Additionally, their relative structural simplicity should allow the use of computational techniques to design and screen novel compounds in a rapid manner. Herein, the absorption and emission maxima of twelve polycyclic aromatic BN-1,2-azaborine analogues containing the N-BOH moiety were examined to determine a methodology for reliably predicting both the energy and character (local excitation [LE] vs charge transfer [CT]) of the absorption and emission maxima for these compounds. The necessity of implicit solvation models was also investigated. The cam-QTP(01) functional with a small, double-ζ quality basis set provides reliable data compared to EOM-CCSD/cc-pVDZ single-point computations. Of note, commonly used functionals for these applications (B3LYP and ωB97xD) struggle to provide reliable results for both the energy and LE character of the transitions relative to EOM-CCSD computations.

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Environmental stress impedes predation and herbivory by limiting the ability of animals to search for and consume prey. We tested the contingency of this relationship on consumer traits and specifically hypothesized that herbivore mobility relative to the return time of limiting environmental stress would predict consumer effects. We examined how wave-induced water motion affects marine communities via herbivory by highly mobile (fish) vs. slow-moving (pencil urchin) consumers at two wave-sheltered and two wave-exposed rocky subtidal locations in the Galapagos Islands. The exposed locations experienced 99th percentile flow speeds that were 2-5 times greater than sheltered locations, with mean flow speeds >33 cm/s vs. <16 cm/s, 2-7 times higher standing macroalgal cover and 2-3 times lower cover of crustose coralline algae than the sheltered locations. As predicted by the environmental stress hypothesis (ESH), there was a negative relationship between mean flow speed and urchin abundance and herbivory rates on Ulva spp. algal feeding assays. In contrast, the biomass of surgeonfishes (Acanthuridae) and parrotfishes (Labridae: Scarinae) was positively correlated with mean flow speed. Ulva assays were consumed at equal rates by fish at exposed and sheltered locations, indicating continued herbivory even when flow speeds surpassed maximum reported swimming speeds at a rate of 1-2 times per minute. Modeled variation in fish species richness revealed minimal effects of diversity on herbivory rates at flow speeds <40 cm/s, when all species were capable of foraging, and above 120 cm/s, when no species could forage, while increasing diversity maximized herbivory rates at flow speeds of 40-120 cm/s. Two-month herbivore exclusion experiments during warm and cool seasons revealed that macroalgal biomass was positively correlated with flow speed. Fish limited macroalgal development by 65-91% at one exposed location but not the second and by 70% at the two sheltered locations. In contrast, pencil urchins did not affect algal communities at either exposed location, but reduced macroalgae by 87% relative to controls at both sheltered locations. We propose an extension of the ESH that is contingent upon mobility to explain species-specific changes in feeding rates and consumer effects on benthic communities across environmental gradients.

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Five ruthenium catalysts described herein facilitate self-sensitized carbon dioxide reduction to form carbon monoxide with a ruthenium catalytic center. These catalysts include four new and one previously reported CNC pincer complexes featuring a pyridinol derived N-donor and N-heterocyclic carbene (NHC) C-donors derived from imidazole or benzimidazole. The complexes have been characterized fully by spectroscopic and analytic methods, including X-ray crystallography. Introduction of a 2,2'-bipyridine (bipy) coligand and phenyl groups on the NHC ligand was necessary for rapid catalysis. [(CNC)Ru(bipy)(CH3CN)](OTf)2 is among the most active and durable photocatalysts in the literature for CO2 reduction without an external photosensitizer. The role of the structure of this complex in catalysis is discussed, including the importance of the pincer's phenyl wingtips, the bipyridyl ligand, and a weakly coordinating monodentate ligand.

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Climate change increases local climatic variation and unpredictability, which can alter ecological interactions and trigger wildlife disease outbreaks. Here we describe an unprecedented multi-species outbreak of wild fish disease driven by a climate perturbation. The 2015-16 El Niño generated a +2.5 °C sea surface temperature anomaly in the Galapagos Islands lasting six months. This coincided with a novel ulcerative skin disease affecting 18 teleost species from 13 different families. Disease signs included scale loss and hemorrhagic ulcerated patches of skin, fin deterioration, lethargy, and erratic behavior. A bacterial culture isolated from skin lesions of two of the affected fish species was identified by sequencing of the 16S rRNA gene as a Rahnella spp. Disease prevalence rates were linearly correlated with density in three fish species. In January 2016, disease prevalence reached 51.1% in the ring-tailed damselfish Stegastes beebei (n = 570) and 18.7% in the king angelfish Holacanthus passer (n = 318), corresponding to 78% and 86% decreases in their populations relative to a 4.5-year baseline, respectively. We hypothesize that this outbreak was precipitated by the persistent warm temperatures and lack of planktonic productivity that characterize extreme El Niño events, which are predicted to increase in frequency with global warming.

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We report the crystallography, emission spectra, femtosecond pump-probe spectroscopy, and density functional theory computations for a series of ruthenium complexes that comprise a new class of chelating triphenylphosphine based ligands with an appended sulfoxide moiety. These ligands differ only in the presence of the para-substitutent (e.g., H, OCH3, CF3). The results show a dramatic range in photoisomerization reactivity that is ascribed to differences in the electron density of the phosphine ligand donated to the ruthenium and the nature of the excited state.

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The first example of a CNC pincer ligand with a central pyridinol ligand is reported in a nickel(ii) complex. This metal complex can be protonated or deprotonated reversibly in situ to switch on or off the photocatalytic performance towards CO2 reduction. The O- substituent appears essential for catalysis.

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Kelp forests provide important ecosystem services, yet coastal kelp communities are increasingly altered by anthropogenic impacts. Kelp forests in remote, offshore locations may provide an informative contrast due to reduced impacts from local stressors. We tested the hypothesis that shallow kelp assemblages (12-15 m depth) and associated fish and benthic communities in the coastal southwest Gulf of Maine (GOM) differed significantly from sites on Cashes Ledge, 145 km offshore by sampling five coastal and three offshore sites at 43.0 +/- 0.07° N latitude. Offshore sites on Cashes Ledge supported the greatest density (47.8 plants m2) and standing crop biomass (5.5 kg m2 fresh weight) of the foundation species Saccharina latissima kelp at this depth in the Western North Atlantic. Offshore densities of S. latissima were over 150 times greater than at coastal sites, with similar but lower magnitude trends for congeneric S. digitata. Despite these differences, S. latissima underwent a significant 36.2% decrease between 1987 and 2015 on Cashes Ledge, concurrent with a rapid warming of the GOM and invasion by the kelp-encrusting bryozoan Membranipora membranacea. In contrast to kelp, the invasive red alga Dasysiphonia japonica was significantly more abundant at coastal sites, suggesting light or dispersal limitation offshore. Spatial differences in fish abundance mirrored those of kelp, as the average biomass of all fish on Cashes Ledge was 305 times greater than at the coastal sites. Remote video censuses of cod (Gadus morhua), cunner (Tautaogolabrus adspersus), and pollock (Pollachius virens) corroborated these findings. Understory benthic communities also differed between regions, with greater abundance of sessile invertebrates offshore. Populations of kelp-consuming sea urchins Stronglyocentrotus droebachiensis, were virtually absent from Cashes Ledge while small urchins were abundant onshore, suggesting recruitment limitation offshore. Despite widespread warming of the GOM since 1987, extraordinary spatial differences in the abundance of primary producers (kelp), consumers (cod) and benthic communities between coastal and offshore sites have persisted. The shallow kelp forest communities offshore on Cashes Ledge represent an oasis of unusually high kelp and fish abundance in the region, and as such, comprise a persistent abundance hotspot that is functionally significant for sustained biological productivity of offshore regions of the Gulf of Maine.

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Nine new polycyclic aromatic BN-1,2-azaborine analogues containing the N-BOH moiety were synthesized using a convenient two-step, one-pot procedure. Characterization of the prepared compounds show the luminescence wavelength and the quantum yields of the azaborines were tunable by controlling the power and location of the donor and acceptor substituents on the chromophore. UV-visible spectroscopy and density functional theory (DFT) computations revealed that the addition of electron-donating moieties to the isoindolinone hemisphere raised the energy of the HOMO, resulting in the reduction of the HOMO-LUMO gap. The addition of an electron-accepting moiety to the isoindolinone hemisphere and an electron-donating group to the boronic acid hemisphere decreased the HOMO-LUMO gap considerably, leading to emission properties from partial intramolecular charge transfer (ICT) states. The combined effect of an acceptor on the isoindolinone side and a donor on the boronic acid side (strong acceptor-π-donor) gave the most red-shifted absorption. The polycyclic aromatic BN-1,2-azaborines emitted strong fluorescence in solution and in the solid-state with the largest red-shifted emission at 640 nm and a Stokes shift of Δλ = 218 nm, or Δν = 8070 cm-1.

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Predators select prey so as to maximize energy and minimize manipulation time. In order to reduce prey detection and handling time, individuals must actively select their foraging space (microhabitat) and populations exhibit morphologies that are best suited for capturing locally available prey. We explored how variation in diet correlates with habitat type, and how these factors influence key morphological structures (mouth gape, eye diameter, fin length, fin area, and pectoral fin ratio) in a common microcarnivorous cryptic reef fish species, the triplefin Helcogrammoides cunninghami. In a mensurative experiment carried out at six kelp-dominated sites, we observed considerable differences in diet along 400 km of the Chilean coast coincident with variation in habitat availability and prey distributions. Triplefins preferred a single prey type (bivalves or barnacles) at northern sites, coincident with a low diversity of foraging habitats. In contrast, southern sites presented varied and heterogeneous habitats, where triplefin diets were more diverse and included amphipods, decapods, and cumaceans. Allometry-corrected results indicated that some morphological structures were consistently correlated with different prey items. Specifically, large mouth gape was associated with the capture of highly mobile prey such as decapods, while small mouth gape was more associated with cumaceans and copepods. In contrast, triplefins that capture sessile prey such as hydroids tend to have larger eyes. Therefore, morphological structures co-vary with habitat selection and prey usage in this species. Our study shows how an abundant generalist reef fish exhibits variable feeding morphologies in response to the distribution of potential habitats and prey throughout its range.