Sulfonate Precursors Research Articles

STING-targeted PET tracer for early assessment of tumor immunogenicity in colorectal cancer after chemotherapy.

To optimize chemotherapy regimens and improve the effectiveness of chemotherapy combined with immunotherapy, a PET tracer specifically targeting the stimulator of interferon genes (STING), denoted as [18F]FBTA was used to monitor the early changes in tumor immunogenicity after chemotherapy in colorectal cancer (CRC) mice. The toluene sulfonate precursor was labeled with 18F to produce the STING targeted probe-[18F]FBTA. [18F]FBTA-PET imaging and biodistribution were performed using CRC mice treated with oxaliplatin (OXA) or cisplatin (CDDP). CRC mice were also treated with low (CDDP-LD: 1 mg/kg) or medium (CDDP-MD: 2.5 mg/kg) doses of CDDP, and subjected to PET imaging and biodistribution. The effects of different chemotherapeutic agents and different doses of CDDP on tumor innate immunity were verified by flow cytometry and immunohistochemistry. PET imaging of CRC mice exhibited notably enhanced tumor uptake in the early phase of chemotherapy with treatment with OXA (3.09 ± 0.25%ID/g) and CDDP (4.01 ± 0.18%ID/g), especially in the CDDP group. The PET-derived tumor uptake values have strong correlations with STING immunohistochemical score. Flow cytometry showed both agents led to DCs and macrophages infiltration in tumors. Compared with OXA, CDDP treatment recruits more DCs and macrophages in CRC tumors. Both CDDP-LD and CDDP-MD treatment elevated uptake in CRC tumors, especially in CDDP-MD group. Immunohistochemistry and flow cytometry confirmed CDDP-MD treatment recruits more DCs and macrophages than CDDP-LD treatment. Overall, the STING-targeted tracer-[18F]FBTA was demonstrated to monitor early changes in tumor immunogenicity in CRC mice after chemotherapy. Besides, the STING-targeted strategy may help to select the appropriate chemotherapy regimen, including chemotherapeutic agents and doses, which further improve clinical decision making for combination immunotherapy after chemotherapy for CRC.

Hepatotoxic response of perfluorooctane sulfonamide (PFOSA) in early life stage zebrafish (Danio rerio) is greater than perfluorooctane sulfonate (PFOS)

Perfluorooctane sulfonamide (PFOSA), a typical perfluorooctane sulfonate precursor (PreFOS), has been detected in the aquatic environment globally. However, the effects of PFOSA at levels measured in the environment have not been well characterized in aquatic organisms. In this study, we evaluated the transcriptional, biochemical, histopathological, and morphological effects of PFOSA to characterize the underlying mechanisms of toxicity by using a universal model in aquatic ecotoxicology, zebrafish (Danio rerio). Transcriptional changes in PFOSA-exposed zebrafish predicted hepatic fibrosis and associated immune function. Subsequent, sublethal impacts were observed, which included significant alterations in liver-specific protein levels, increased immune cell numbers, and liver pathological structural damage. In addition, we compared the effects caused by PFOSA and perfluorooctane sulfonate (PFOS) at the same exposure concentration and found a greater hepatotoxic effect of PFOSA relative to PFOS, indicating that the adverse impacts of PFOSA may be more severe. This was the first study to comparatively explore the hepatotoxic response of PFOSA and PFOS in aquatic organisms, which can be used for ecological risk assessments of PreFOS compounds.

Distribution of per- and poly-fluoroalkyl substances and their precursors in human blood

Many studies have examined per- and poly-fluoroalkyl substances (PFASs) in human blood. However, the distribution of PFASs in human blood remains not well known, especially for perfluorooctane sulfonate (PFOS) precursors. In this study, human blood samples (n = 162) were collected from general Chinese population, and then the isomer-specific partitioning of PFASs between human plasma and red blood cells (RBCs) were investigated. Perfluorooctanoate (PFOA) and PFOS were consistently the predominant PFASs in both human plasma and RBCs. In human blood, among C4–C7 perfluoroalkyl carboxylates (PFCAs), the calculated mean mass fraction in plasma (Fp) values increased from 0.76 to 0.82 with the increasing chain length. C7–C13 PFCAs exhibited a trend of gradually decreasing mean Fp with chain length. Among PFAS precursors, 6:2 fluorotelomer phosphate diester had the highest mean Fp value (0.87 ± 0.11). Calculated Fp values of N-methyl perfluorooctanesulfonamide (N-MeFOSA) and N-ethyl perfluorooctanesulfonamide (N-EtFOSA) were 0.66 ± 0.13 and 0.70 ± 0.12, respectively. Individual branched isomers consistently had greater Fp values than their corresponding linear isomers for PFOA, PFHxS, and perfluoroctane sulfonamide. To our knowledge, this study first reports the distribution of N-MeFOSA and N-EtFOSA in human blood, contributing to the better understanding of the occurrence and fate of PFASs in humans.

Identification and quantification of perfluorooctane sulfonamide isomers by liquid chromatography–tandem mass spectrometry

Characterization of the isomers perfluorooctane sulfonamide (PFOSA), a key intermediate of the perfluorooctane sulfonate (PFOS) precursors, is a prerequisite to understand the contribution of precursors to PFOS in the environmental and biological matrices. However, the lack of commercial standards makes quantification of the PFOSA isomers in complex matrices a big challenge. For the first time, a liquid chromatography-tandem mass spectrometry (LC–MS/MS) method was established to identify and quantify PFOSA isomers. Improvement on chromatographic separation with selected reaction monitoring allowed full resolution of six monomethyl branched isomers of PFOSA. The isomers were identified and quantified using a series of characteristic fragment ions and the specific product ions of molecular anion m/z 498: m/z 78 (n-), m/z 169 (iso-), m/z 419 (1m-), m/z 164 (2m-), m/z 259 (3m-), m/z 269 (4m-) and m/z 219 (5m-PFOSA). With the aid of 19F nuclear magnetic resonance to define one technical product as standard, the developed method was used to quantify PFOSA isomers in other technical products and spiked fish blood samples. The results indicated that the developed method displayed strong application prospect for measuring trace level of PFOSA isomers in complex samples. The method detection limits for all isomers were in the range of 0.1–1 pg/g ww for blood samples.

A facile synthesis of graphene nanoribbon-quantum dot hybrids and their application for composite electrolyte membrane in direct methanol fuel cells

In this work, we report the concept of synthesizing graphene nanoribbon-graphene quantum dot (GNR-GQD) hybrids with even grafting of GQD on GNR sheet in a facile single step process under ultrasonication in chlorosulfonic acid. Further, diazotization route is followed for the preparation of 4-benzenediazonium sulfonate precursor to sulfonate both GNR and GQD to form sulfonated graphene nanoribbons-sulfonated graphene quantum dots (sGNR-sGQD) nanohybrids. Synergistic and structure dependent effect of nanohybrids is seen via its dispersion in sulfonated poly(ether ether ketone) (sPEEK) to form nanocomposite membrane. sPEEK/sGNR-sGQD (1.5 wt %) nanocomposite membrane shows remarkable direct methanol fuel cell (DMFC) performance compared to pristine sPEEK and Nafion 117 with 40% increment in peak power density along with higher durability up to 100 h due to better physicochemical properties like water uptake, ion exchange capacity, proton conductivity, and reduced methanol crossover to suggest its potential which includes diverse membrane applications.

Sulfluramid use in Brazilian agriculture: A source of per- and polyfluoroalkyl substances (PFASs) to the environment

N-Ethyl perfluorooctane sulfonamide (EtFOSA) is a perfluorooctane sulfonate (PFOS) precursor and the active ingredient in sulfluramid, a pesticide which is used extensively in Brazil for management of leaf cutting ants. Here we investigate the occurrence of EtFOSA, PFOS, and other per- and polyfluoroalkyl substances (PFASs) in soil, eucalyptus leaves, water (ground, riverine, and coastal (estuarine/marine)) and coastal sediment from an agricultural region of Bahia State, Brazil. This area contains a larger number of eucalyptus plantations where sulfluramid is suspected to be applied. Soil, leaves, and coastal water (marine/estuarine) contained ∑PFAS concentrations of up to 5400 pg g−1, 979 pg g−1, and 1020 pg L−1, respectively, with PFAS profiles generally dominated by PFOS and perfluorooctane sulfonamide (FOSA). Coastal sediment contained ∑PFAS concentrations of up to 198 pg g−1, with PFOS, FOSA, and perfluorooctanoic acid (PFOA) being the most frequently observed PFASs. These substances are all potential EtFOSA transformation products, pointing to sulfluramid as a possible source. In riverine water, ∑PFAS concentrations of up to 8930 pg L−1 were observed. PFOS and PFOA were detected in all river water samples. Groundwater also exhibited PFAS contamination (5730 pg L−1 ∑PFASs), likely from sulfluramid use. The observation of other PFASs (e.g. perfluorobutanoic acid) in freshwater suggests that other PFAS sources (in addition to sulfluramid) may be important in this region. Overall, these data support the hypothesis that sulfluramid use contributes to the occurrence of PFASs in the Brazilian environment.

Isolation, Identification, and Biodegradation Behaviors of a Perfluorooctane Sulfonic Acid Precursor (PreFOSs) Degrading Bacterium from Contaminated Soil

Transformation of perfluorooctane sulfonate (PFOS) precursors (PreFOSs) is considered an additional source of PFOS in the environment and biota. A PreFOSs-degrading bacterium PF1, which was able to utilize PreFOSs as the sole carbon and energy source for growth, was isolated from contaminated soil collected from the surroundings of a fluoride factory. According to its morphology and 16S rDNA gene sequence analysis, strain PF1 was identified as Hyphomicrobium sp. The degradation rates of perfluorooctane sulfonamide (PFOSA) and N-ethyl perfluorooctane sulfonamide (N-EtFOSA) by PF1 were 14.6% and 8.2% (30℃; pH=7.0-7.2), respectively, whereas PF1 was unable to degrade PFOS. PFOSA could be biodegraded to PFOS. N-EtFOSA could be biodegraded to perfluorooctane sulfonamide acetic acid (FOSAA), PFOSA, and PFOS; PFOS was the predominant metabolite. Based on the above analysis, the proposed metabolic pathway of PFOSA by strain PF1 is deamination to form PFOS. Two possible degradation pathways are proposed for N-EtFOSA: ① deethylation of N-EtFOSA to produce PFOSA, followed by deamination to form PFOS, and ②oxidation of N-EtFOSA to FOSAA followed by sequential dealkylation to produce PFOSA, and then transformation to PFOS by deamination.

Biotransformation and responses of antioxidant enzymes in hydroponically cultured soybean and pumpkin exposed to perfluorooctane sulfonamide (FOSA)

Perfluorooctane sulfonamide (FOSA) is an important perfluorooctane sulfonate (PFOS) precursor used for commercial applications. In order to investigate the transformation and responses of selected antioxidant and degradation enzymes of FOSA in the plants, in vivo exposure of soybean (Glycine max L. Merrill) and pumpkin (Cucurbita maxima L.) were conducted in the solution-plant microcosms. FOSA was readily taken up by soybean and pumpkin roots and translocated to shoots, and metabolized to PFOS, perfluorohexane sulfonate (PFHxS) and perfluorobutane sulfonate (PFBS). Although morphological and biomass effects were not visible, significant changes in oxidative stress response were observed except for thiobarbituric acid reactive substances (TBARS). Superoxide dismutase (SOD) and peroxidase (POD) activities were significantly increased by 19.2–30.8% and 19.2–20.7% in soybean (8–12 d) respectively, and increased by 39.2–92.8% and 21.1–37.6% in pumpkin (3–12 d) respectively, suggesting an activation of the antioxidant defense system in the plants exposed to FOSA. Glutathione-S-transferase (GST) activities were decreased in soybean (2–12 d) with 9.0–36.1% inhibition and increased in pumpkin (3–12 d) with 22.5–47.3% activation respectively; cytochrome P450 (CYP450) activities were increased markedly in soybean and pumpkin with 13.2–53.6% and 26.7–50.2% activation respectively, giving indirect evidences on the involvement of CYP450 and GST in degradation of FOSA in plants.

Behavior of N-ethyl perfluorooctane sulfonamido acetic acid (N-EtFOSAA) in biosolids amended soil-plant microcosms of seven plant species: Accumulation and degradation

Perfluorooctane sulfonate (PFOS) precursors have been found extensively in sewage sludge and biosolids-amended soils. The degradation of these precursors are regarded as a significant source of PFOS in the environment. In this study, the accumulation of N-ethyl perfluorooctane sulfonamido acetic acid (N-EtFOSAA) in the plants of seven species, namely alfalfa, lettuce, maize, mung bean, radish, ryegrass, and soybean from biosolids-amended soil, and the degradation kinetics of N-EtFOSAA in soil-plant microcosms were evaluated over 60 days. N-EtFOSAA was found in the roots of all plant species, while was not in stems and leaves. The root concentration factors of N-EtFOSAA ranged 0.52–1.37 (pmol/groot)/(pmol/gsoil). Stepwise multiple regression analysis was used to elucidate the accumulation of N-EtFOSAA in the roots of plants. The results showed that the root protein and lipid contents explain 85.0% of the variation in root N-EtFOSAA levels (P < 0.05). Four degradation products, including N-ethyl perfluorooctane sulfonamide (N-EtFOSA), perfluorooctane sulfonamide acetate (FOSAA), perfluorooctane sulfonamide (FOSA) and PFOS were found in soils and plant roots, stems and leaves, indicating the degradation of N-EtFOSAA in soil-plant system. Degradation kinetics fitted a first-order kinetic model well. Degradation rate constants of N-EtFOSAA in the microcosms with plants ranged 0.063–0.165 d−1, which was 1.40–3.6 times higher than those without plants. Degradation rate constant of maize was relatively higher than those of other plant species. The results is the first to reveal N-EtFOSAA accumulation in plants and degradation in soil-plant microcosms.

Kinetic analysis of aerobic biotransformation pathways of a perfluorooctane sulfonate (PFOS) precursor in distinctly different soils

With the phaseout of perfluorooctane sulfonate (PFOS) production in most countries and its well known recalcitrance, there is a need to quantify the potential release of PFOS from precursors previously or currently being emitted into the environment. Aerobic biodegradation of N-ethyl perfluorooctane sulfonamidoethanol (EtFOSE) was monitored in two soils from Indiana, USA: an acidic forest silt loam (FRST-48, pH = 5.5) and a high pH agricultural loam (PSF-49, pH = 7.8) with similar organic carbon contents (2.4 and 2.6%) for 210 d and 180 d, respectively. At designated times, triplicate samples were sacrificed for which headspace samples were taken followed by three sequential extractions. Extracts were analyzed using HPLC-tandem mass spectrometry. Measured profiles of EtFOSE degradation and generation/degradation of subsequent metabolites were fitted to the Indiana soils data as well as to a previously published data set for a Canadian soil using an R-based model (KinGUII) to explore pathways and estimate half-lives (t1/2) for EtFOSE and metabolites. EtFOSE degradation ranged from a few days to up to a month. PFOS yields ranged form 1.06–5.49 mol% with the alkaline soils being four to five times higher than the acidic soil. In addition, a direct pathway to PFOS had to be invoked to describe the early generation of PFOS in the Canadian soil. Of all metabolites, the sulfonamidoacetic acids were the most persistent (t1/2 ≥ 3 months) in all soils. We hypothesized that while pH-pKa dependent speciation may have impacted rates, differences in microbial communities between the 3 soils arising from varied soil properties including pH, nutrient levels, soil management, and climatic regions are likely the major factors affecting pathways, rates, and PFOS yields.

Syntheses of Combretastatins D-1, D-2, and D-4 via Ring Contraction by Flash Vacuum Pyrolysis.

We report the syntheses of combretastatins D-2 and D-4 as well as a formal synthesis of combretastatin D-1 by a conceptually new route harnessing a ring-contracting flash vacuum pyrolytic extrusion of sulfur dioxide from the respective 16-membered sulfone precursors. Via flash vacuum pyrolysis, even metaparacyclophanes as small and strained as the hitherto unknown oxa[1.5]metaparacyclophane could be prepared as a side product en route to combretastatin D-2 by synchronous extrusion of SO2 and CO2.

Oxysulfate/oxysulfide of Tb3+ obtained by thermal decomposition of terbium sulfate hydrates under different atmospheres

The terbium oxysulfate/oxysulfide Tb2O2SO4/Tb2O2S were prepared from two different precursors: Tb(DAS)3·2H2O and Tb2(SO4)3·8H2O, utilizing two different atmospheres of thermal decomposition. The reaction of Tb4O7 with aqueous solution of H2SO4 (2 mol L−1) produces Tb2(SO4)3·8H2O; after isolation and purification, it was reacted with Ba(DAS)2·H2O in aqueous solution to produce Tb2(DAS)3·2H2O precursor. Both of the terbium sulfonate Tb(DAS)3·2H2O and terbium sulfate Tb2(SO4)3·8H2O precursors were analyzed in two different atmospheres of thermal treatment; in air atmosphere, terbium oxysulfate Tb2O2SO4 was obtained as the end product; and in reducing (CO) atmosphere, terbium oxysulfide Tb2O2S one was obtained. Thus, it was observed that the change of precursor can result in obtaining different size of particles. Moreover, it was also observed that the terbium oxysulfate Tb2O2SO4 obtained from sulfonate precursor at 1223 K, while from sulfate one at 1323 K. Similarly, the terbium oxysulfide Tb2O2S obtained from both sulfonate and sulfate precursors did not show significant difference, at 1013 K from sulfonate and 1033 K from sulfate precursor.

Comparative hepatic in vitro depletion and metabolite formation of major perfluorooctane sulfonate precursors in arctic polar bear, beluga whale, and ringed seal

Perfluorooctane sulfonate (PFOS) has been reported to be among the most concentrated persistent organic pollutants in Arctic marine wildlife. The present study examined the in vitro depletion of major PFOS precursors, N-ethyl-perfluorooctane sulfonamide (N-EtFOSA) and perfluorooctane sulfonamide (FOSA), as well as metabolite formation using an assay based on enzymatically viable liver microsomes for three top Arctic marine mammalian predators, polar bear (Ursus maritimus), beluga whale (Delphinapterus leucas), and ringed seal (Pusa hispida), and in laboratory rat (Rattus rattus) serving as a general mammalian model and positive control. Rat assays showed that N-EtFOSA (38nM or 150ngmL−1) to FOSA metabolism was >90% complete after 10min, and at a rate of 23pmolmin−1mg−1 protein. Examining all species in a full 90min incubation assay, there was >95% N-EtFOSA depletion for the rat active control and polar bear microsomes, ∼65% for ringed seals, and negligible depletion of N-EtFOSA for beluga whale. Concomitantly, the corresponding in vitro formation of FOSA from N-EtFOSA was also quantitatively rat≈polar bear>ringed seal>>>beluga whale. A lack of enzymatic ability and/or a rate too slow to be detected likely explains the lack of N-EtFOSA to FOSA transformation for beluga whale. In the same assays, the depletion of the FOSA metabolite was insignificant (p>0.01) and with no concomitant formation of PFOS metabolite. This suggests that, in part, a source of FOSA is the biotransformation of accumulated N-EtFOSA in free-ranging Arctic ringed seal and polar bear.

Gold nanocatalysts supported on heterostructured PbSO4-MCF mesoporous materials for CO oxidation

Metal oxides are commonly used as the supports of gold nanoparticles for catalytic CO oxidation, whereas metal salts are rarely considered suitable supports. In the present work, we developed a new kind of gold nanocatalyst supported on heterostructured PbSO4-MCF mesoporous materials that was prepared by an in situ growth method using dodecylbenzenesulfonate (SDBS) as a sulfonate precursor. It was found that an Au/PbSO4-MCF (SDBS) catalyst preheated at 300°C showed high CO conversion below 100°C. In addition, the stability of selected catalysts was studied as a function of time on stream. Because of the alteration of surface properties, these Au nanocatalysts were highly sinter-resistant.

Persistence of Perfluoroalkyl Acid Precursors in AFFF-Impacted Groundwater and Soil

Several classes of polyfluorinated chemicals that are potential precursors to the perfluorinated carboxylates and sulfonates are present in aqueous film-forming foams (AFFF). To assess the persistence of these AFFF-derived precursors, groundwater, soil, and aquifer solids were obtained in 2011 from an unlined firefighter training area at a U.S. Air Force Base where AFFF was regularly used between 1970 and 1990. To measure the total concentration of perfluorinated carboxylate and sulfonate precursors in archived AFFF formulations and AFFF-impacted environmental samples, a previously developed assay that uses hydroxyl radical to oxidize precursors to perfluorinated carboxylates was adapted for these media. This assay was employed along with direct measurement of 22 precursors found in AFFF and a suite of other poly- and perfluoroalkyl substances (PFASs). On a molar basis, precursors accounted for 41-100% of the total concentration of PFASs in archived AFFF formulations. In the training area, precursors measured by the oxidation assay accounted for an average of 23% and 28% of total PFASs (i.e., precursors and perfluorinated carboxylates and sulfonates) in groundwater and solids samples, respectively. One precursor in AFFF, perfluorohexane sulfonamide amine, was observed on several highly contaminated soil and aquifer solids samples, but no other precursors present in AFFF formulations were detected in any samples at this field site. Suspected intermediate transformation products of precursors in AFFF that were directly measured accounted for approximately half of the total precursor concentration in samples from the training site. The fraction of PFASs consisting of perfluorinated carboxylates and sulfonates was greater in groundwater and solid samples than in any archived AFFF formulations, suggesting that much of the mass of precursors released at the site was converted to perfluorinated carboxylates and sulfonates. The precursors that have persisted at this site may generate significant amounts of additional perfluorinated carboxylates and sulfonates upon remediation of contaminated groundwater or aquifer solids.

Alternative synthesis for the preparation of 16α‐[18F]fluoroestradiol

We have developed a new precursor, 3,17β-O-bis(methoxymethyl)-16β-O-p-nitrobenzenesulfonylestriol (14c) of 16α-[(18) F]fluoroestradiol ([(18) F]FES). Although we could not selectively protect the C17 alcohol in the presence of the C16 alcohol, we were able to prepare and chromatographically isolate the desired C16 TBDMS, C17,C3-dimethoxymethyl (diMOM) protected estriol derivative and convert into the ultimate fluorination precursor. The MOM protective group proved to be more quickly removed than the cyclic sulfate group. The di-MOM protective precursor at the C3 and C17 alcohols instead of a cyclic sulfate group shortened hydrolysis time. We prepared three different sulfonate precursors at C16 alcohol. After checking their reactivity in the [(18) F]fluorination step and considering the stability of the precursors, we obtained the best results with nosylate precursor 14c.

Guanidinium vs. Ammonium Surfactants in Soft‐Templating Approaches: Nanostructured Silica and Zwitterionic i‐Silica from Complementary Precursor–Surfactant Ion Pairs

AbstractWe investigated the behaviour of guanidinium and ammonium surfactants as structure‐directing agents in template‐directed hydrolysis/polycondensation processes. For this purpose, a series of guanidinium surfactants was synthesised from long‐chain‐substituted primary amines. In a first series of experiments, we compared nanostructured silicas obtained by means of template‐directed hydrolysis/polycondensation reactions of TEOS in the presence of either guanidinium‐ or ammonium‐based surfactants. We observed that typical MCM‐41‐type silicas displaying a 2D hexagonal architecture were obtained in the presence of ammonium surfactants such as cetyltrimethylammonium bromide (CTAB). In contrast, the use of guanidinium surfactants led to the formation of hollow silica spheres or spherical silica nanoparticles. Secondly, we investigated the use of ammonium and guanidinium surfactants in the formation of periodic mesoporous organosilicas containing ionic groups (i‐silica). In particular, we studied template‐directed hydrolysis/polycondensation reactions of zwitterionic ammonium sulfonate and ammonium carboxylate precursors. We observed that both reactions involving the ammonium sulfonate precursor yielded structured i‐silicas. In contrast, hydrolysis/polycondensation reactions of the ammonium carboxylate precursor afforded structured materials only in the presence of the guanidinium surfactant, whereas amorphous materials were obtained in the presence of CTAB. This result reflects specific surfactant–precursor interactions and suggests that the nature of both surfactant and precursor determine the formation of i‐silica materials displaying regular architectures on a mesoscopic length scale.

Spatial and Temporal Trends of Perfluorinated Compounds in Beluga Whales (Delphinapterus leucas) from Alaska

Wildlife from remote locations have been shown to bioaccumulate perfluorinated compounds (PFCs) in their tissues. Twelve PFCs, consisting of perfluorinated carboxylic (PFCA) and sulfonic (PFSA) acids as well as the perfluorooctane sulfonate (PFOS) precursor perfluorooctane sulfonamide (PFOSA), were measured in livers of 68 beluga whales (Delphinapterus leucas) collected from two subpopulations, Cook Inlet and eastern Chukchi Sea, in Alaska between 1989 and 2006. PFOS and PFOSA were the dominant compounds measured in both beluga stock populations, with overall median concentrations of 10.8 ng/g and 22.8 ng/g, respectively. Long-chain perfluorocarboxylates, PFCAs (9 to 14 carbons), were detected in more than 80% of the samples. Perfluoroundecanoic acid (PFUnA) and perfluorotridecanoic acid (PFTriA) made up a large percentage of the PFCAs measured with median concentrations of 8.49 ng/g and 4.38 ng/g, respectively. To compare differences in location, year, sex, and length, backward stepwise multiple regression models of the individual and total PFC concentrations were used. Spatially, the Cook Inlet belugas had higher concentrations of most PFCAs and PFOS (p < 0.05); however, these belugas had a lower median concentration of PFOSA when compared to belugas from the eastern Chukchi Sea (p < 0.05). Temporal trends indicated most PFCAs, PFHxS, PFOS, and PFOSA concentrations increased from 1989 to 2006 (p < 0.05). Males had significantly higher concentrations of PFTriA, ΣPFCA, and PFOS (p < 0.05). Perfluorononanic acid (PFNA) and PFOS showed a significant decrease in concentration with increasing animal length (p < 0.05). These observations suggest the accumulation of PFCs in belugas is influenced by year, location, sex, and length.

Periodic mesoporous organosilica from zwitterionic precursors

Mesoporous hybrid silica bearing zwitterionic species were synthesized via template-directed hydrolysis-polycondensation reactions from zwitterionic ammonium sulfonate precursors. The formation of the nanostructured phases involves specific precursor-template interactions. The obtained materials are efficient heterogeneous catalysts in Biginelli reactions.

2-Benzothiazolyl Propargyl Sulfides: Versatile Precursors for Enantiopure Allenes, E-α,β-Unsaturated Ketones and Z-Sulfonylalkenes

A novel, stereospecific route to allenes is described. The approach proceeds via a retro-ene reaction, initiated by lithium aluminium hydride mediated cleavage of benzothiazole from the respective (chiral) 2-benzothiazolyl propargyl sulfone precursors. As such, allenes in up to 92% yield are formed under evolution of sulfur dioxide at ambient temperature. Furthermore, a new and mild way to generate E-α,β-unsaturated ketones has been discovered. These substrates are formed in around 50% yield by treating 2-benzothiazolyl propargyl sulfides with hydrogen peroxide and a catalytic amount of ammonium molybdate at room temperature. In the course of this research it was also found that treatment of 2-benzothiazolyl propargyl sulfones with sodium borohydride led to reduction of the triple bond exclusively to the Z-double bond.