In-situ construction of fluorescent probes for hydrogen peroxide detection in mitochondria and lysosomes with on-demand modular assembling and double turn-on features.

Due to the diverse H2O2 distribution in organelles, fluorescent probes were usually required to be prepared separately, which limited the convenience and practicability. Herein, we reported a flexible strategy to in-situ construct H2O2 fluorescent probes in different organelles. A tetrazine fused probe TP was developed with rapid click reaction capacity and sensitive H2O2 response. When treated with H2O2, the turn-on fluorescence was effectively quenched by the tetrazine part. Only after click reaction with dienophiles, the fluorescence resumed. In application, cells were firstly treated with triphenylphosphorus tagged norbornene (TPP-NB) to label mitochondria, which was followed by the introduction of probe TP to trigger click reaction. The in-situ constructed probe P1 served as a local H2O2 sensor. In a similar way, probe P2 was in-situ constructed in lysosomes via probe TP and morpholine tagged norbornene (MP-NB). With this on-demand modular assembling and double turn-on features, our strategy to construct fluorescent probes presented high flexibility and anti-interference performance, which was expected to inspired more applications in biological studies.

Nitrobenzoxadiazole derivatives of the rat selective toxicant norbormide as fluorescent probes for live cell imaging.

Norbormide [5-(α-hydroxy-α-2-pyridylbenzyl)-7-(α-2-pyridylbenzylidene)-5-norbornene-2,3-dicarboximide] (NRB, 1), an existing but infrequently used rodenticide, is known to be uniquely toxic to rats, but relatively harmless to other rodents and mammals. As a vasoactive agent, NRB induces a species-specific vasocontractile effect that is restricted to the peripheral arteries of the rat. Despite the precise mechanisms behind this phenomenon having yet to be fully clarified, it is postulated that the molecular target of NRB could be located within the plasma membrane of rat peripheral artery myocytes (e.g. rat caudal artery myocytes). As such, the primary objective of this study was to develop a fluorescently labelled derivative of NRB to investigate its subcellular distribution/localization in both NRB-sensitive (freshly isolated rat caudal artery myocytes, FIRCAMs) and NRB-insensitive (human hepatic stellate, LX2) cells. Of the examples prepared, lead structure endo-NRB-NBD-bPA subsequently demonstrated retention of the parent toxicant's pharmacological profile (in terms of its ability to induce both a vasocontractile response in rat caudal artery rings in vitro, and a lethal end-point in rats in vivo). Endo-NRB-NBD-bPA was also shown to be significantly less permeable (an integral feature in the design of fluorescent probes targeting cell-surface receptors) to both LX2 cells and FIRCAMs. Disappointingly, no fluorescence could be observed on the plasma membrane of FIRCAMs stained with endo-NRB-NBD-bPA.

New class of hantaan virus inhibitors based on conjugation of the isoindole fragment to (+)-camphor or (-)-fenchone hydrazonesv.

This work presents the design and synthesis of camphor, fenchone, and norcamphor N-acylhydrazone derivatives as a new class of inhibitors of the Hantaan virus, which causes haemorrhagic fever with renal syndrome (HFRS). A cytopathic model was developed for testing chemotherapeutics against the Hantaan virus, strain 76-118. In addition, a study of the antiviral activity was carried out using a pseudoviral system. It was found that the hit compound possesses significant activity (IC50 = 7.6 ± 2 µM) along with low toxicity (CC50 > 1000 µM). Using molecular docking procedures, the binding with Hantavirus nucleoprotein was evaluated and the correlation between the structure of the synthesised compounds and the antiviral activity was established.

Fungicide isopyrazam degradative response toward extrinsically added fungal and bacterial strains.

The current research is a pioneer in the evaluation of isopyrazam biodegradation, which has been performed utilizing soil-isolated microbes. Biodisintegrative assays of pure fungal strains, namely Aspergillus flavus (AF), Penicillium chrysogenum (PC), Aspergillus niger (AN), Aspergillus terreus (AT), and Aspergillus fumigatus (AFu), and bacterial strains, namely Xanthomonas axonopodis (XA) and Pseudomonas syringae (PS), were utilized. Initial isopyrazam concentration (10 mg/L) was prepared with an individual microbial suspension and monitored for 35 days. Isopyrazam biotransformation was analyzed quantitatively and qualitatively by UV-visible spectrophotometery and gas chromatography-mass spectroscopy. P. syringae (R2 = 0.90) and X. axonopodis (R2 = 0.88) displayed maximal potential to metabolize the fungicide (86% and 80%, respectively) while forming intermediate metabolites, including 3-difluoromethyl-1-methyl-1H-pyrazole-4-carboxylic acid ((S)-9-hydroxy-9-isopropyl-1,2,3,4-tetrahydro-1,4-methanonaphthalen-5-yl)-amide, 3-difluoromethyl-1H-pyrazole-4-carboxylic acid, and 3-difluoromethyl-1-methyl-1H-pyrazole-4-amide. Isopyrazam degradation by all strains, AT, PC, AFu, AN, AF, XA, and PS, was found to be 11%, 18%, 21%, 21%, 18%, 30%, 80%, and 86%, respectively, after 35 days, elucidating the effectiveness of all the utilized strains in degrading isopyrazam at varying rates. The descending order of half-lives (days) obtained is as follows: AT (56.8) > PC (44.7) > AFu (40.7) > AN (39.6) > AF (32.6) > XA (28.1) > PS (21) days. Current research can influence imperative and significant environment-friendly bioremedial strategies for xenobiotic eradication from the ecological compartments.

Biocatalysis for terpene-based polymers.

Accelerated generation of bio-based materials is vital to replace current synthetic polymers obtained from petroleum with more sustainable options. However, many building blocks available from renewable resources mainly contain unreactive carbon-carbon bonds, which obstructs their efficient polymerization. Herein, we highlight the potential of applying biocatalysis to afford tailored functionalization of the inert carbocyclic core of multicyclic terpenes toward advanced materials. As a showcase, we unlock the inherent monomer reactivity of norcamphor, a bicyclic ketone used as a monoterpene model system in this study, to afford polyesters with unprecedented backbones. The efficiencies of the chemical and enzymatic Baeyer-Villiger transformation in generating key lactone intermediates are compared. The concepts discussed herein are widely applicable for the valorization of terpenes and other cyclic building blocks using chemoenzymatic strategies.

Strategies toward Organic Carbon Monoxide Prodrugs.

Carbon monoxide is widely acknowledged as an important gasotransmitter in the mammalian system with importance on par with that of nitric oxide. It has also been firmly established as a potential therapeutic agent with a wide range of indications including organ transplantation, cancer, bacterial infection, and inflammation-related conditions such as colitis and sepsis. One major issue in developing CO based therapeutics is its delivery in a pharmaceutically acceptable form. Currently, there are generally five forms of deliveries: inhaled CO, photosensitive CO-releasing molecules, encapsulated CO, CO dissolved in drinks, and molecules that would release CO under physiological conditions without the need for light. For over a decade, the last category only included metal-based CO releasing molecules. What had been missing were organic CO prodrugs, which release CO under physiological conditions with tunable rates and in response to various exogenous and endogenous triggers such as water, chemical reagents, esterase, ROS, and changes in pH. This Account describes our work in this area as well as the demonstration for these organic prodrugs to recapitulate CO's pharmacological effects both in vitro and in vivo. Generally, two categories of CO prodrugs have been developed in our lab. Both can be considered as precursors of norbornadien-7-ones, which readily undergo cheletropic reaction under very mild conditions to extrude CO. The first category of CO prodrugs capitalizes on the inter- and intramolecular inverse electron demand Diels-Alder (DAinv) reaction to trigger CO release under physiological conditions. As for the bimolecular CO prodrugs, we proposed a new concept of "enrichment triggered CO release" by conjugating both components with a mitochondria-targeting moiety to achieve targeted CO delivery with improved biological outcomes in vitro and in vivo. As for the unimolecular CO prodrugs, the release half-lives can be readily tuned from minutes to days by varying the substituents on the dienone ring, the tethering linker, and the alkyne. Some significant structure-release rates relationships (SRRs) have been unveiled. An esterase-activated CO prodrug and a cascade prodrug system for co-delivery of CO and another payload have also been devised using such an intramolecular click and release strategy. The second category of CO prodrugs leverage on an elimination reaction to generate norbornadien-7-ones for CO release from norborn-2-en-7-ones. In the case of pH-sensitive ones, the CO release is triggered by ß-elimination, and the release rate can be quantitatively predicted using the Hammett constant of the substituents on the leaving group. The ROS-activated ones take advantage of ROS-induced selenoxide elimination to achieve targeted CO delivery to disease sites with elevated ROS level. We strongly believe that these CO prodrugs could serve as powerful tools for CO-associated biological studies and are promising candidates for ultimate clinical applications.

Foliar application of benzovindiflupyr shows non-fungicidal effects in wheat plants.

BACKGROUND: The fungicide benzovindiflupyr belongs to the class of succinate dehydrogenase inhibitors (SDHIs). Certain SDHIs have shown plant physiological effects, so-called secondary effects, that appeared to be related to the plant water status. Therefore, the effect of benzovindiflupyr on transpiration of leaves and whole wheat plants was studied under controlled conditions. Furthermore, wheat yield trials under controlled and natural drought stress in the field were conducted. RESULTS: Transpiration of detached wheat leaves was reduced by benzovindiflupyr in a dose-dependent manner. Similarly, whole-plant transpiration decreased for several days following application of this fungicide. In 16 field trials under drought stress conditions that were classified as disease-free, treatment of wheat plants at the flag leaf stage or at heading with benzovindiflupyr showed a grain yield increase (+5.2%; P ≤ 0.01) that was partially attributed to an increased thousand-grain weight. CONCLUSIONS: Water saving during pre-anthesis as a result of benzovindiflupyr application may be associated with better seed setting and filling under dry field conditions in wheat. The results of this research provide new insights into secondary effects of SDHIs that lead directly to yield improvements. © 2017 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Functional and Nonfunctional Forms of CquiOR91, an Odorant Selectivity Subunit of Culex quinquefasciatus.

In Culex quinquefasciatus, CquiOR91 is the ortholog of 2 larvae-specific odorant receptors (ORs) from Anopheles gambiae (Agam\Or40, previously shown to respond to several odorant ligands including the broad-spectrum repellent N,N-diethyl-3-methylbenzamide, DEET) and Aedes aegypti (Aaeg\Or40). When we cloned full-length CquiOR91 from a Culex quinquefasciatus larval head RNA sample, we found 2 alleles of this OR, differing at 9 residues. Functional analysis using the Xenopus oocyte expression system and 2-electrode voltage clamp electrophysiology revealed one allele (CquiOR91.1) to be nonfunctional, whereas the other allele (CquiOR91.2) was functional. Receptors formed by CquiOR91.2 and Cqui\Orco responded to (-)-fenchone, (+)-fenchone, and DEET, similar to what has been reported for Agam\Or40. We also identified 5 novel odorant ligands for the CquiOR91.2 + Cqui\Orco receptor: 2-isobutylthiazole, veratrole, eucalyptol, d-camphor, and safranal, with safranal being the most potent. To explore possible reasons for the lack of function for CquiOR91.1, we generated a series of mutant CquiOR91.2 subunits, in which the residue at each of the 9 polymorphic residue positions was changed from what occurs in CquiOR91.2 to what occurs in CquiOR91.1. Eight of the 9 mutant versions of CquiOR91.2 formed functional receptors, responding to (-)-fenchone. Only the CquiOR91.2 Y183C mutant was nonfunctional. The reverse mutation (C183Y) conferred function on CquiOR91.1 , which became responsive to (-)-fenchone and safranal. These results indicate that the "defect" in CquiOR91.1 that prevents function is the cysteine at position 183.

Regio-selective lipase catalyzed hydrolysis of oxanorbornane-based sugar-like amphiphiles at air-water interface: A polarized FT-IRRAS study.

Interfacial hydrolysis of oxanorbornane-based amphiphile (Triol C16) by Candida rugosa lipase was investigated using real-time polarized Fourier transform-infrared reflection absorption spectroscopy (FT-IRRAS). The kinetics of hydrolysis was studied by analyzing the ester carbonyl ν(CO) stretching vibration band across the two dimensional (2D) array of molecules at the confined interface. In particular, we demonstrate Triol C16 to form Michaelis-Menten type complex, like that of lipid-substrate analogues, where the Triol C16 head group remained accessible to the catalytic triad of the lipase. The enzyme-induced selective cleavage of the ester bond was spectroscopically monitored by the disappearance of the intense ν(CO) resonance at 1736cm-1. Consequently, the in situ spectroscopic measurements evidenced selective ester hydrolysis of Triol C16 yielding Tetrol C2OH and Palmitic acid, which remained predominantly in the undissociated form at the interface. The conformation sensitive amide I (majorly ν(CO)) and the interfacial water reorganization suggested 2D ordering of the enzyme molecules following which interfacial reactions were employed towards probing the enzyme kinetics at the air/water interface. The investigation demonstrated further the potential of IRRAS spectroscopy for real-time monitoring the hydrolytic product formation and selectivity at biomimetic interfaces.

Modular Design of Poly(norbornenes) for Organelle-Specific Imaging in Tumor Cells.

Through modular ROMP (ring-opening metathesis polymerization) directly from monomeric norbornenes of bioactive peptides, rhodamine B chromophore, and PEG solubilizer, we designed and synthesized a series of water-soluble poly(norbornenes) with organelle-specific imaging capability in tumor cells. For the selection of FxrFxK, TAT, and SV40 peptide sequences, these fluorescence probes exhibited different targeting specificity toward mitochondria, lysosome, and nucleolus, respectively, based on the same poly(norbornene) backbonds. More importantly, the ROMP strategy enables selective combination from various monomers and allows programmable biofunctionalization via peptide sequence permutations, which would greatly extend the biomedical applications such as imaging, diagnosis, and therapy for these synthetic polymers.

Conformational landscape and the selectivity of cytochrome P450cam.

Conformational heterogeneity and dynamics likely contribute to the remarkable activity of enzymes but are challenging to characterize experimentally. These features are of particular interest within the cytochrome P450 class of monooxygenases, which are of great academic, medicinal, and biotechnological interest as they recognize a broad range of substrates, such as various lipids, steroid precursors, and xenobiotics, including therapeutics. Here, we use linear and 2D IR spectroscopy to characterize the prototypical P450, cytochrome P450cam, bound to three different substrates, camphor, norcamphor, or thiocamphor, which are hydroxylated with high, low, and intermediate regioselectivity, respectively. The data suggest that specific interactions with the substrate drive the population of two different conformations, one that is associated with high regioselectivity and another associated with lower regioselectivity. Although Y96 mediates a hydrogen bond thought necessary to orient the substrate for high regioselectivity, the population and dynamics of the conformational states are largely unaltered by the Y96F mutation. This study suggests that knowledge of the conformational landscape is central to understanding P450 activity, which has important practical ramifications for the design of therapeutics with optimized pharmacokinetics, and the manipulation of P450s, and possibly other enzymes, for biotechnological applications.

Two-step protein labeling by using lipoic acid ligase with norbornene substrates and subsequent inverse-electron demand Diels-Alder reaction.

Inverse-electron-demand Diels-Alder cycloaddition (DAinv ) between strained alkenes and tetrazines is a highly bio-orthogonal reaction that has been applied in the specific labeling of biomolecules. In this work we present a two-step labeling protocol for the site-specific labeling of proteins based on attachment of a highly stable norbornene derivative to a specific peptide sequence by using a mutant of the enzyme lipoic acid ligase A (LplA(W37V) ), followed by the covalent attachment of tetrazine-modified fluorophores to the norbornene moiety through the bio-orthogonal DAinv . We investigated 15 different norbornene derivatives for their selective enzymatic attachment to a 13-residue lipoic acid acceptor peptide (LAP) by using a standardized HPLC protocol. Finally, we used this two-step labeling strategy to label proteins in cell lysates in a site-specific manner and performed cell-surface labeling on living cells.

Site-specific enzymatic introduction of a norbornene modified unnatural base into RNA and application in post-transcriptional labeling.

Inverse electron demand Diels-Alder cycloadditions have proven to be extremely useful for mild and additive-free orthogonal labeling of biomolecules, amongst others, for RNA labeling in vitro and in a cellular context. Here we present a method for site-specific introduction of an alkene modification into RNA via T7 in vitro transcription. For this, an unnatural, hydrophobic base pairing system developed by Romesberg and coworkers was modified introducing one or two norbornene moieties at predefined positions into RNA oligonucleotides in an in vitro transcription reaction. This allows post-transcriptional functionalization of these RNA molecules with tetrazine derivatives containing for instance fluorophores or biotin.

Characterization of potent fusion inhibitors of influenza virus.

New inhibitors of influenza viruses are needed to combat the potential emergence of novel human influenza viruses. We have identified a class of small molecules that inhibit replication of influenza virus at picomolar concentrations in plaque reduction assays. The compound also inhibits replication of vesicular stomatitis virus. Time of addition and dilution experiments with influenza virus indicated that an early time point of infection was blocked and that inhibitor 136 tightly bound to virions. Using fluorescently labeled influenza virus, inhibition of viral fusion to cellular membranes by blocked lipid mixing was established as the mechanism of action for this class of inhibitors. Stabilization of the neutral pH form of hemagglutinin (HA) was ruled out by trypsin digestion studies in vitro and with conformation specific HA antibodies within cells. Direct visualization of 136 treated influenza virions at pH 7.5 or acidified to pH 5.0 showed that virions remain intact and that glycoproteins become disorganized as expected when HA undergoes a conformational change. This suggests that exposure of the fusion peptide at low pH is not inhibited but lipid mixing is inhibited, a different mechanism than previously reported fusion inhibitors. We hypothesize that this new class of inhibitors intercalate into the virus envelope altering the structure of the viral envelope required for fusion to cellular membranes.

GC-MS and LC-(high-resolution)-MS(n) studies on the metabolic fate and detectability of camfetamine in rat urine.

Camfetamine (N-methyl-3-phenyl-norbornan-2-amine; CFA) belongs as amphetamine-type stimulant to the so-called new psychoactive substances. CFA is an analogue of fencamfamine, an appetite suppressant developed in the 1960s. The described effects of CFA are slight stimulation and increased vigilance and the side effects are tachycardia, paranoia, and sleeplessness. The aims of the presented work were to study the metabolic fate and the detectability of CFA in urine and to elucidate which cytochrome-P450 (CYP) isoenzymes are involved in the main metabolic steps. For metabolism studies, rat urine samples were isolated by solid-phase extraction without and after enzymatic cleavage of conjugates. The phase I metabolites were separated and identified after/without acetylation by gas chromatography-mass spectrometry (GC-MS) and/or liquid chromatography-high resolution-linear ion trap mass spectrometry (LC-HR-MS(n)), respectively, and the phase II metabolites by LC-HR-MS(n). From the identified metabolites, the following main metabolic pathways were deduced: N-demethylation, aromatic mono or bis-hydroxylation followed by methylation of one hydroxy group, hydroxylation of the norbornane ring, combination of these steps, and glucuronidation and/or sulfation of the hydroxy metabolites. The N-demethylation was catalyzed by CYP2B6, CYP2C19, CYP2D6, and CYP3A4, the aromatic hydroxylation by CYP2C19 and CYP2D6, and the aliphatic hydroxylation was catalyzed by CYP1A2, CYP2B6, CYP2C19, and CYP3A4. Finally, the intake of a common user's dose of CFA could be confirmed in rat urine using the authors' GC-MS and the LC-MS(n) standard urine screening approaches via CFA and several metabolites, with the hydroxy-aryl CFA and the corresponding glucuronide being the most abundant.

Surface water mineralization of isopyrazam according to OECD 309: observations on implementation of the new data requirement within agrochemical regulation.

A surface water mineralization study (according to the Organisation for Economic Co-operation and Development [OECD] guideline OECD 309) is a new requirement in European Union agrochemical regulations; therefore, industry has little experience with this test. The guideline allows for a number of options within the test design, notably the options to conduct the study under diffuse light and to include an inoculum of suspended sediment. The present study was designed to investigate the potential impact of these options on the degradation rate of a representative compound. The fungicide, isopyrazam, was chosen as it was previously shown to be susceptible to metabolism by phototrophic organisms under a fluorescent light-dark cycle. The impact of diffuse light was investigated at light intensities representative of those at depth in large, open water bodies (<7% of the incident intensity), and it was demonstrated that metabolism of isopyrazam by phototrophic microorganisms was rapid (median degradation time for 50% of the test compound [DT50] < 50 d), whereas degradation in continuous darkness was negligible. Furthermore, investigation at 2 different light intensities resulted in similar degradation rates, indicating that this transformation mechanism was not proportional to light intensity, provided that there was sufficient light for photosynthesis to occur. Inclusion of suspended sediment did not have a significant impact on the degradation rate of isopyrazam, except at extremely high sediment concentrations, which were not considered representative of conditions in large, open water bodies.

Biotransformation of (+)-fenchone by Salmonella typhimurium OY1002/2A6 expressing human CYP2A6 and NADPH-P450 reductase.

In this study, biotransformation of (+)-fenchone (compound 1) by Salmonella typhimurium OY1002/2A6 expressing human CYP2A6 and NADPH-P450 reductase yielded two oxidized metabolites, namely, (+)-(1S,6R)-6-endo-hydroxyfenchone (compound 2) and (+)-(1S,6S)-6-exo-hydroxyfenchone (compound 3). The conversion rate of compound 1 to compound 2 and 3 was 2.4% and 5.2%, respectively. This is the first study that succeeded in metabolizing compound 1 to obtain large amounts of metabolite 2 and 3 by using S. typhimurium OY1002/2A6 expressing human CYP2A6 and NADPH-P450 reductase.

Design and synthesis of prodrugs of the rat selective toxicant norbormide.

Norbormide [5-(α-hydroxy-α-2-pyridylbenzyl)-7-(α-2-pyridylbenzylidene)-5-norbornene-2,3-dicarboximide] (NRB), an existing but infrequently used rodenticide, is known to be uniquely toxic to rats but relatively harmless to other rodents and mammals. However, one major drawback of NRB as a viable rodenticide relates to an evolutionary aversion developed by the rat leading to sub-lethal dosing due to either its unpleasant 'taste' or rapid onset of effects. A series of NRB prodrugs were prepared in an effort to 'mask' this acute response. Their synthesis and biological evaluation (in vitro vasoconstrictory activity, in vitro hydrolytic and enzymatic stability and lethality/palatability in vivo) is described. Compound 19 displayed the most promising profile with respect to a delay in the onset of symptoms and was subsequently demonstrated to be significantly more palatable to rats.

Time-dependent fifth-order bands in nominally third-order 2D IR vibrational echo spectra.

Progress in the field of 2D IR vibrational spectroscopy has been bolstered by the production of intense mid-IR laser pulses. As higher-energy pulses are employed, a concomitant increase occurs in the likelihood of fifth-order contributions to the 2D IR spectra. We report the appearance of fifth-order signals in 2D IR spectra of CO bound to the active site of the enzyme cytochrome P450(cam) with the substrate norcamphor. Two bands with novel time dependences, one on the diagonal and one off-diagonal, are not accounted for by normal third-order interactions. These bands are associated with a ν = 1-2 vibrational transition frequency. Both bands decay to 0 and then grow back in with opposite sign. The diagonal band is positive at short time, decays to 0, reappears with negative sign, before eventually decaying to 0. The off-diagonal band is negative at short time, decays to 0, reappears positive, and then decays to 0. The appearance and time dependence of these bands are characterized. Understanding these fifth-order bands is useful because they may be misidentified with time-dependent bands that arise from other processes, such as chemical exchange, vibrational coupling, or energy transfer. The presence and unusual time dependences of the fifth-order bands are reproduced with model calculations that account for the fact that vibrational relaxation from the ν = 2 to 1 level is approximately a factor of 2 faster than that from the ν = 1 to 0 level.

Historic trends of dechloranes 602, 603, 604, dechlorane plus and other norbornene derivatives and their bioaccumulation potential in lake ontario.

Temporal trends and seasonal variation of Dechloranes (Dec) 602, 603, 604, and Chlordene Plus (CP) in Niagara River suspended sediment, a Lake Ontario sediment core, and Lake Ontario lake trout were investigated, with Mirex and Dechlorane Plus (DP) included for comparison. Temporal concentration trends were generally consistent in each of the media for all compounds with the lowest concentrations observed in or after the late 1990s. In Niagara River suspended sediments, all compounds showed seasonal variation over a year with distinct profiles observed. The relative concentration patterns observed were total DP > Mirex > Dec 602 and Dec 604 > Dec 603 > CP in suspended sediments and sediment cores, whereas Mirex was highest in lake trout, followed by Dec 602 and DP. Dec 602 concentrations were 50 to 380 times greater than those of DP in lake trout, indicating Dec 602 has a greater bioaccumulation potential. The estimated biota-sediment accumulation factor (BSAF) for Dec 602 was much greater than for DP in Lake Ontario, and was greater than those calculated for PBDEs, indicating that assessment of some dechlorane compounds is merited if use is ongoing or planned.