Relative contributions of water- and methanol-soluble compounds and their hydrophobic/hydrophilic subfractions to the ROS (reactive oxygen species)-generating potential of ambient fine aerosols (D(p) < 2.5 μm) are assessed. ROS-generating (or oxidative) potential of the particulate matter (PM) was measured by the dithiothreitol (DTT) assay. Particles were collected on quartz filters (N = 8) at an urban site near central Atlanta during January-February 2012 using a PM(2.5) high-volume sampler. Filter punches were extracted separately in both water and methanol. Hydrophobic and hydrophilic fractions were then subsequently segregated via a C-18 solid phase extraction column. The DTT assay response was significantly higher for the methanol extract, and for both extracts a substantial fraction of PM oxidative potential was associated with the hydrophobic compounds as evident from a substantial attenuation in DTT response after passing PM extracts through the C-18 column (64% for water and 83% for methanol extract; both median values). The DTT activities of water and methanol extracts were correlated with the water-soluble (R = 0.86) and water-insoluble organic carbon (R = 0.94) contents of the PM, respectively. Brown carbon (BrC), which predominantly represents the hydrophobic organic fraction (referred to as humic-like substances, HULIS), was also correlated with DTT activity in both the water (R = 0.78) and methanol extracts (R = 0.83). Oxidative potential was not correlated with any metals measured in the extracts. These findings suggest that the hydrophobic components of both water-soluble and insoluble organic aerosols substantially contribute to the oxidative properties of ambient PM. Further investigation of these hydrophobic organic compounds could help identify sources of a significant fraction of ambient aerosol toxicity.

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Understanding patterns and processes in biological diversity is a critical task given current and rapid environmental change. Such knowledge is even more essential when the taxa under consideration are important ecological and evolutionary models. One of these cases is the monogonont rotifer cryptic species complex Brachionus plicatilis, which is by far the most extensively studied group of rotifers, is widely used in aquaculture, and is known to host a large amount of unresolved diversity. Here we collate a dataset of previously available and newly generated sequences of COI and ITS1 for 1273 isolates of the B. plicatilis complex and apply three approaches in DNA taxonomy (i.e. ABGD, PTP, and GMYC) to identify and provide support for the existence of 15 species within the complex. We used these results to explore phylogenetic signal in morphometric and ecological traits, and to understand correlation among the traits using phylogenetic comparative models. Our results support niche conservatism for some traits (e.g. body length) and phylogenetic plasticity for others (e.g. genome size).

Three diterpene-benzoate natural products, with novel carbon skeletons and an unusual proposed biosynthesis, were isolated from extracts of the Fijian red alga Callophycus serratus and identified by a combination of X-ray crystallographic, NMR, and mass spectral analyses. Bromophycolide A (1) displayed cytotoxicity against several human tumor cell lines via specific apoptotic cell death. This represents the first discovery of natural products incorporating a diterpene and benzoate skeleton into a macrolide system.The discovery of novel carbon skeletons in natural products research is uncommon, providing new targets for synthetic chemists and pharmacologists, and leading to testable hypotheses regarding biosynthetic mechanisms and ecological function. Red macroalgae are well-known for the production of brominated metabolites, including terpenoids and phenols, yet some taxa within the Rhodophyta remain relatively unstudied. Only six secondary metabolites, one oxylipin and five bromophenols, have been previously characterized from the red algal family Solieriaceae. 1,2 Herein, we report the discovery of a unique structural class of macrolides from Callophycus serratus, an understudied member of the Solieriaceae.We used bioassay-guided fractionation followed by spectroscopic and X-ray crystallographic analyses to identify three novel natural products (1-3) of unusual biosynthetic origin and possessing promising antineoplastic and antimicrobial activities. Supporting Information Available: Additional acknowledgments, experimental details, 2D NMR data (COSY, HSQC, HMBC, NOESY, ROESY), 1 H NMR spectra for 1-3, and X-ray crystallographic data (tables and CIF files) for 1 and 2. This material is available free of charge via the Internet at http://pubs.acs.org. The most abundant natural product from C. serratus, bromophycolide A (1), displayed an [M -H] − molecular ion with m/z 661.0194 and characteristic tribrominated isotopic pattern, suitable for a molecular formula of C 27 H 37 O 4 Br 3 . X-ray diffraction analysis of 1 revealed a 15-membered macrolide within a diterpene-benzoate framework (Figures 1 and 2). The bromine atom within the isopropyl appendage was disordered with respect to the isopropyl methyls over two primary positions, with 70% and 30% occupancies. The Flack parameter was refined to be −0.002(16), indicating that the geometry shown is the absolute configuration. NIH Public AccessThe NMR spectral data of 1 supported the structure derived from X-ray diffraction analysis (Table 1; Supporting Information). HMBC correlations from the methyl groups anchored the carbon skeleton, enabling assignments of all quaternary carbons. COSY and additional HMBC correlations provided the connectivity within spin systems (Supporting Information).From high-resolution mass spectral data, bromophycolide B (2) appeared to be an isomer of 1, with a parent ion with m/z 661.0191. X-ray diffraction analysis of 2 indicated a 16-membered macrolide with absolute stereochemistry predicted as in Figures 1 and 2. Chemical shift...

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Induction of sexual reproduction in Brachionus plicatilis (Monogononta, Rotifera) by a density-dependent chemical cue Abstract-Induction of mixis (sexual reproduction) in rotifers of the genus Brachionus is believed to be triggered by a chemical that is released into the water and accumulates at high population densities. However, direct and conclusive evidence for this hypothesis is thus far lacking. In this study, two mass cultures of the rotifer Brachionus plicatilis were monitored as they grew from low to high population densities. Conditioned water was prepared daily from these cultures, and females were exposed in a bioassay, which consisted of juvenile Brachionus, cultured individually in large volumes that would normally suppress mixis. Conditioned water induced mixis in the bioassay at rates comparable to those found in the mass cultures. Both in bioassay and mass cultures, mixis was essentially absent in the beginning of the experiment, when population densities were very low. The first mictic females appeared at densities of 0.1 females ml Ϫ1 , and their proportion increased rapidly as the populations grew to Ͼ1 female ml Ϫ1 . The maximum rates of mixis in the bioassay were highly significant and reached 51% of those observed in the mass cultures. These results strongly support the hypothesis that mixis in Brachionus plicatilis is induced by a density-dependent chemical cue.