Absolute Configuration of Atropisomeric Polychlorinated Biphenyl 183 Enantiomerically Enriched in Human Samples

Polychlorinated biphenyls (PCBs) are still of serious concern as a potential health hazard due to their persistency and bioacumulation. Of 209 possible PCB congeners, with varying number and position of chlorine atom(s), 19 are chiral. These are mostly highly chlorinated and tend to remain longer against the biological decompositions, suffering biological deracemization in the environment. In this work, we have unequivocally determined the absolute configurations of important chiral PCBs 183 and 171, as well as 132, through the combined theoretical and experimental investigations of the chiroptical properties (circular dichroism and optical rotation), which will be valuable in elucidating the mechanism of biological enantiomer enrichment of PCBs in the environment

Data_for_Descriptions

Chloroplast number in leaf stomatal GCs of Col, Ler, and Ws. Measurements of chloroplast number in arbitrarily selected pairs of GCs ('cell A' and 'cell B') are shown

Cyclodextrin Polymers as Highly Effective Adsorbents for Removal and Recovery of Polychlorobiphenyl (PCB) Contaminants in Insulating Oil

A total of 179 countries (parties) ratified the Stockholm Convention on persistent organic pollutants (POPs) and agreed to destroy polychlorobiphenyls (PCBs) and develop a sound management plan by 2028. Currently, still 3 million tons of PCB-contaminated oil and equipment need to be managed under the Stockholm Convention. Thus, the development of a facile and environmentally benign method to treat large amounts of oil stockpiles contaminated with PCBs is a crucial subject. Herein, we report that cyclodextrin (CD) polymers, which are easily prepared by cross-linking the renewable cyclic oligosaccharide γ-cyclodextrin (γ-CD) with dibasic acid dichlorides, are a new selective and powerful adsorbent to remove PCB contaminants in oil. When PCB (100 ppm)-contaminated oil was passed through a column packed with the terephthaloyl-cross-linked γ-CD polymer (TP-γ-CD polymer) at 80–110 °C, the PCB contaminants were completely removed from the oil. Additionally, methyl esterification of the free carboxylic groups of the TP-γ-CD polymer enabled the complete recovery of the PCBs adsorbed on the polymer (with >99.9% recovery efficiency) by simply washing with acetone. The methyl-esterified TP-γ-CD polymer could be recycled at least 10 times for PCB adsorption without any loss in the adsorption capability. These results revealed that the γ-CD polymers can function as highly effective and powerful adsorbents for the removal and recovery of PCBs from PCB-contaminated oil and, thus, significantly contribute to the protection of the global environment

Data_for_Fig6

Chloroplast number in leaf stomatal GCs of WT, arc5, arc6, and atminE1. Measurements of chloroplast number in arbitrarily selected pairs of GCs ('cell A' and 'cell B') are shown

Enantioselectivity of 2,2′,3,5′,6-Pentachlorobiphenyl (PCB 95) Atropisomers toward Ryanodine Receptors (RyRs) and Their Influences on Hippocampal Neuronal Networks

Nineteen ortho-substituted PCBs are chiral and found enantioselectively enriched in ecosystems. Their differential actions on biological targets are not understood. PCB 95 (2,2′,3,5′,6-pentachlorobiphenyl), a chiral PCB of current environmental relevance, is among the most potent toward modifying ryanodine receptors (RyR) function and Ca²⁺ signaling. PCB 95 enantiomers are separated and assigned a<i>R</i>- and a<i>S</i>-PCB 95 using three chiral-column HPLC and circular dichroism spectroscopy. Studies of RyR1-enriched microsomes show <i>aR</i>-PCB 95 with >4× greater potency (EC₅₀ = 0.20 ± 0.05 μM), ∼ 1.3× higher efficacy (<i>B</i>_max = 3.74 ± 0.07 μM) in [³H]­Ryanodine-binding and >3× greater rates (<i>R</i> = 7.72 ± 0.31 nmol/sec/mg) of Ca²⁺ efflux compared with <i>aS</i>-PCB 95, whereas racemate has intermediate activity. <i>aR</i>-PCB 95 has modest selectivity for RyR2, and lower potency than racemate toward the RyR isoform mixture in brain membranes. Chronic exposure of hippocampal neuronal networks to nanomolar PCB 95 during a critical developmental period shows divergent influences on synchronous Ca²⁺ oscillation (SCO): <i>rac</i>-PCB 95 increasing and <i>aR</i>-PCB 95 decreasing SCO frequency at 50 nM, although the latter’s effects are nonmonotonic at higher concentration. <i>aS-</i>PCB95 shows the greatest influence on inhibiting responses to 20 Hz electrical pulse trains. Considering persistence of PCB 95 in the environment, stereoselectivity toward RyRs and developing neuronal networks may clarify health risks associated with enantioisomeric enrichment of PCBs

Identification and Characterization of Oxidative Metabolites of 1‑Chloropyrene

Polycyclic aromatic hydrocarbons (PAHs) and chlorinated PAHs (ClPAHs) are ubiquitous contaminants that bind to the aryl hydrocarbon receptor (AhR) and exhibit mutagenic potential. It is difficult to monitor human exposure levels to ClPAHs because the exposure routes are complicated, and environmental concentrations are not always correlated with the levels of PAHs. Urinary PAH metabolites are useful biomarkers for evaluating PAH exposure, and ClPAH metabolites may therefore contribute to the estimation of ClPAH exposure. One of the most abundant ClPAHs present in the environment is 1-chloropyrene (ClPyr), and urinary ClPyr metabolites have the potential to be good biomarkers to evaluate the level of exposure to ClPAHs. Since the metabolic pathways involving ClPAHs are still undetermined, we investigated the effect of human cytochrome P450 enzymes on ClPyr and identified three oxidative metabolites by liquid chromatography–tandem mass spectrometry and nuclear magnetic resonance. We found that ClPyr was metabolized most efficiently by the P450 1A1 enzyme, followed by the 1B1 and 1A2 enzymes. Similar to ClPyr, these metabolites were shown to have agonist activity for the human AhR. We detected these metabolites when ClPyr reacted with a pooled human liver S9 fraction as well as in human urine samples. These results suggest that the metabolites may be used as biomarkers to evaluate the extent of exposure to ClPAHs

Plastid phenotypes in leaf PCs of <i>Arabidopsis</i> WT, <i>arc5</i>, <i>arc6</i>, and <i>atminE1</i>.

<p>(A–J) Images of plastid-targeted YFP in the third-fourth leaf petioles of 4-week-old WT (A), <i>arc5</i> (B, E, H), <i>arc6</i> (C, F, I), and <i>atminE1</i> (D, G, J) seedlings. CLSM images of maximal intensity projection are shown. Giant plastids (arrows), putative dividing plastids (arrowheads), stomata (double arrowheads), and mini-plastids (asterisks) are indicated. Bar = 10 μm.</p

Involvement of STH7 in light-adapted development in <i>Arabidopsis thaliana</i> promoted by both strigolactone and karrikin

<p>Strigolactones (SLs) and karrikins (KARs) regulate photomorphogenesis. GR24, a synthetic SL and KAR₁, a KAR, inhibit the hypocotyl elongation of <i>Arabidopsis thaliana</i> in a weak light. GR24 and KAR₁ up-regulate the expression of <i>STH7</i>, encoding a transcription factor belonging to the double B-box zinc finger subfamily. In this study, we used <i>STH7</i>-overexpressing (<i>STH7ox</i>) lines and functionally defective <i>STH7</i> (<i>STH7</i>-<i>SRDX</i>) mutants to investigate roles of SLs and KARs in photomorphogenesis of <i>Arabidopsis</i>. Hypocotyl elongation of <i>STH7</i>-<i>SRDX</i> mutants was less sensitive to both GR24 and KAR₁ treatment than that of wild-type <i>Arabidopsis</i> under weak light conditions. Furthermore, the chlorophyll and anthocyanin content was increased in <i>STH7ox</i> lines when de-etiolated with light and GR24-treated plants had enhanced anthocyanin production. GR24 and KAR₁ treatment significantly increased the expression level of photosynthesis-related genes <i>LHCB1</i> and <i>rbcS</i>. The results strongly suggest that SL and KAR induce photomorphogenesis of <i>Arabidopsis</i> in an STH7-dependent manner.</p> <p>Strigolactone response is mediated by D14 and KAI2 while karrikin response is mediated by only KAI2.</p

The <i>Arabidopsis arc5</i> and <i>arc6</i> mutations differentially affect plastid morphology in pavement and guard cells in the leaf epidermis

<div><p>Chloroplasts, or photosynthetic plastids, multiply by binary fission, forming a homogeneous population in plant cells. In <i>Arabidopsis thaliana</i>, the division apparatus (or division ring) of mesophyll chloroplasts includes an inner envelope transmembrane protein ARC6, a cytoplasmic dynamin-related protein ARC5 (DRP5B), and members of the FtsZ1 and FtsZ2 families of proteins, which co-assemble in the stromal mid-plastid division ring (FtsZ ring). FtsZ ring placement is controlled by several proteins, including a stromal factor MinE (AtMinE1). During leaf mesophyll development, <i>ARC6</i> and <i>AtMinE1</i> are necessary for FtsZ ring formation and thus plastid division initiation, while <i>ARC5</i> is essential for a later stage of plastid division. Here, we examined plastid morphology in leaf epidermal pavement cells (PCs) and stomatal guard cells (GCs) in the <i>arc5</i> and <i>arc6</i> mutants using stroma-targeted fluorescent proteins. The <i>arc5</i> PC plastids were generally a bit larger than those of the wild type, but most had normal shapes and were division-competent, unlike mutant mesophyll chloroplasts. The <i>arc6</i> PC plastids were heterogeneous in size and shape, including the formation of giant and mini-plastids, plastids with highly developed stromules, and grape-like plastid clusters, which varied on a cell-by-cell basis. Moreover, unique plastid phenotypes for stomatal GCs were observed in both mutants. The <i>arc5</i> GCs rarely lacked chlorophyll-bearing plastids (chloroplasts), while they accumulated minute chlorophyll-less plastids, whereas most GCs developed wild type-like chloroplasts. The <i>arc6</i> GCs produced large chloroplasts and/or chlorophyll-less plastids, as previously observed, but unexpectedly, their chloroplasts/plastids exhibited marked morphological variations. We quantitatively analyzed plastid morphology and partitioning in paired GCs from wild-type, <i>arc5</i>, <i>arc6</i>, and <i>atminE1</i> plants. Collectively, our results support the notion that ARC5 is dispensable in the process of equal division of epidermal plastids, and indicate that dysfunctions in ARC5 and ARC6 differentially affect plastid replication among mesophyll cells, PCs, and GCs within a single leaf.</p></div

Plastid phenotypes in leaf stomatal GCs in <i>Arabidopsis</i> WT, <i>arc5</i>, <i>arc6</i>, and <i>atminE1</i> plants.

<p>(A–I) Images of plastid-targeted YFP in the third-fourth leaf petioles of 4-week-old seedlings from the WT (A), <i>arc5</i> (B–D), <i>arc6</i> (E–G), and <i>atminE1</i> (H, I). CLSM images of maximal intensity projection (top panels) and merged with DIC (bottom panels) are shown. (J, K) Images of YFP-labeled plastids in GCs reconstructed from a series of optical sections generated by CLSM, taken at 0.3 or 0.6 μm intervals. The GC pairs in panels (J) and (K) are identical to those in panels (D) and (G), respectively. (L) Epifluorescence microscopy images of GCs in the third-fourth leaf petioles of 4-week-old seedlings from <i>arc6</i>. Images of YFP (top panels) and DIC (bottom panels) are shown. Bar = 10 μm.</p