Inclusion of oil from transgenic Camelina sativa in feed effectively supplies EPA and DHA to Atlantic salmon (Salmo salar) grown to market size in seawater pens.

Atlantic salmon were fed either a diet reflecting current commercial feeds with added oil supplied by a blend of fish oil and rapeseed oil (COM), or a diet formulated with oil from transgenic Camelina sativa containing 20% EPA + DHA (TCO). Salmon were grown from smolt to market size (>3 kg) in sea pens under semi-commercial conditions. There were no differences in growth, feed efficiency or survival between fish fed the TCO or COM diets at the end of the trial. Levels of EPA + DHA in flesh of salmon fed TCO were significantly higher than in fish fed COM. A 140 g fillet from TCO-fed salmon delivered 2.3 g of EPA + DHA, 67% of the weekly requirement level recommended by many health agencies, and 1.5-fold more than the 1.5 g of EPA + DHA for COM-fed fish. Oil from transgenic Camelina supported growth and improved the nutritional quality of farmed salmon in terms of increased "omega-3" supply for human consumers.

More Than an Antioxidant: Role of Dietary Astaxanthin on Lipid and Glucose Metabolism in the Liver of Rainbow Trout (Oncorhynchus mykiss).

This study investigated the influence of dietary astaxanthin (AX) on glucose and lipid metabolism in rainbow trout liver. Two iso-nitrogenous and iso-lipidic diets were tested for 12 weeks in rainbow trout with an initial mean weight of 309 g. The S-ASTA diet was supplemented with 100 mg of synthetic AX per kg of feed, whereas the control diet (CTRL) had no AX. Fish fed the S-ASTA diet displayed lower neutral and higher polar lipids in the liver, associated with smaller hepatocytes and lower cytoplasm vacuolization. Dietary AX upregulated adipose triglyceride lipase (atgl), hormone-sensitive lipase (hsl2) and 1,2-diacylglycerol choline phosphotransferase (chpt), and downregulated diacylglycerol acyltransferase (dgat2), suggesting the AX's role in triacylglycerol (TAG) turnover and phospholipid (PL) synthesis. Dietary AX may also affect beta-oxidation with the upregulation of carnitine palmitoyltransferase 1 (cpt1α2). Although hepatic cholesterol levels were not affected, dietary AX increased gene expression of sterol regulatory element-binding protein 2 (srebp2). Dietary AX upregulated the expression of 6-phosphogluconate dehydrogenase (6pgdh) and downregulated pyruvate kinase (pkl). Overall, results suggest that dietary AX modulates the oxidative phase of the pentose phosphate pathway and the last step of glycolysis, affecting TAG turnover, ß-oxidation, PL and cholesterol synthesis in rainbow trout liver.

Stable isotope and fatty acid analysis reveal the ability of sea cucumbers to use fish farm waste in integrated multi-trophic aquaculture.

Stable isotope ratios, carbon (δ13C) and nitrogen (δ15N), and fatty acids validated the trophic connection between farmed fish in a commercial nearshore fish farm and sea cucumbers in the Mediterranean Sea. This dual tracer approach evaluated organic matter transfer in integrated multi-trophic aquaculture (IMTA) and the ability of sea cucumbers to incorporate fish farm waste (fish faeces and uneaten artificial fish feed) into their tissue. Between October 2018 and September 2019, Holothuria (Roweothuria) poli Delle Chiaje, 1824, co-cultured at IMTA sites directly below one of the commercial fish cage , at 10 m and 25 m from the selected fish cage, and at two reference sites over 800 m from the fish farm. Sea cucumbers were sampled from each site in February, May and September, except at 0 m due to mass mortalities recorded here in the first month of study. Isotopic mixing models revealed that fish farm organic waste was the dominant dietary source for H. poli in IMTA at 10 m and 25 m from the cage. The contribution of marine plant-derived organic matter, Posidonia oceanica leaves and rhizomes, was least important. The isotopic signatures of sea cucumber tissues at reference sites were not explained by the sampled food resources. Importantly, fatty acid profiling revealed a high abundance of individual terrestrial plant fatty acids, such as oleic (18:1n-9), linoleic (18:2n-6) and eicosenoic (20:1n-9) acids in sea cucumber tissue at 10 m and 25 m from the fish cage, presumably linked to the terrestrial plant oil content of the fish feeds. At the reference sites, sea cucumber tissues were characterised by higher relative abundance of arachidonic acid (20:4n-6) acid, and the natural marine-based eicosapentaenoic (20:5n-3) and docosahexaenoic (22:6n-3) acids. These analyses revealed important differences in the composition of H. poli between the IMTA and reference locations, driven by aquaculture-derived waste near fish cages. Moreover, this study revealed temporal variation in food availability and quality, and possible differences in the physiological responses of H. poli. Stable isotope analysis and fatty acid profiling provided complementary evidence for the important dietary preferences of H. poli and validated the potential of sea cucumbers to uptake aquaculture organic waste as part of inshore fish-sea cucumber IMTA. It reveals the important implications that an established trophic link has on the viability of using sea cucumbers for the development of IMTA and the sustainable expansion of aquaculture.

Molecular Antioxidant Functions are Enhanced in Atlantic Bluefin Tuna (Thunnus Thynnus, L.) Larvae Fed Selenium-Enriched Rotifers Brachionus Rotundiformis.

Selenium (Se) is an essential trace element for fish with more than 40 selenoproteins identified, many exhibiting antioxidant functions. This study investigated the effect of dietary Se supplementation on physiological parameters, selenoprotein and antioxidant enzyme gene expression in Atlantic bluefin tuna (ABT, Thunnus thynnus) larvae. First-feeding ABT larvae were divided into triplicate groups and fed rotifers Brachionus rotundiformis enriched with five different levels of Se (0, 3, 10, 30, and 100 µg Se·L-1) until 14 days after hatching. Both rotifers and ABT larvae effectively accumulated Se achieving maximum levels in the Se100 treatment (30.05 µg Se·g-1 and 194 ± 38 µg Se·g-1 dry mass, respectively). Larvae showed highest total length when fed Se3 rotifers, whereas flexion index was highest in larvae fed Se10. Selenium supplementation increased the gene expression of selenoproteins gpx1, msrb1, trxr2, selenom, selenop, and selenoe compared to the non-supplemented control (Se0), but only marginal differences were detected between supplementation levels. In contrast, expression of the antioxidant enzymes cat and sod1 were lowest in larvae fed Se100. To conclude, non-Se-enriched rotifers may be suboptimal for first feeding ABT larvae, which showed improved selenoprotein and antioxidant gene expression when fed a diet containing 4.42 µg Se·g-1 dry mass.

Iodine Content of Wild and Farmed Seafood and Its Estimated Contribution to UK Dietary Iodine Intake.

Iodine is an important nutrient for human health and development, with seafood widely acknowledged as a rich source. Demand from the increasing global population has resulted in the availability of a wider range of wild and farmed seafood. Increased aquaculture production, however, has resulted in changes to feed ingredients that affect the nutritional quality of the final product. The present study assessed the iodine contents of wild and farmed seafood available to UK consumers and evaluated its contribution to current dietary iodine intake. Ninety-five seafood types, encompassing marine and freshwater fish and shellfish, of wild and farmed origins, were purchased from UK retailers and analysed. Iodine contents ranged from 427.4 ± 316.1 to 3.0 ± 1.6 µg·100 g-1 flesh wet weight (mean ± SD) in haddock (Melanogrammus aeglefinus) and common carp (Cyprinus carpio), respectively, being in the order shellfish > marine fish > freshwater fish, with crustaceans, whitefish (Gadiformes) and bivalves contributing the greatest levels. Overall, wild fish tended to exhibit higher iodine concentrations than farmed fish, with the exception of non-fed aquaculture species (bivalves). However, no significant differences were observed between wild and farmed Atlantic salmon (Salmo salar), rainbow trout (Oncorhynchus mykiss), and turbot (Psetta maxima). In contrast, farmed European seabass (Dicentrarchus labrax) and seabream (Sparus aurata) presented lower, and Atlantic halibut (Hippoglossus hippoglossus) higher, iodine levels than their wild counterparts, most likely due to the type and inclusion level of feed ingredients used. By following UK dietary guidelines for fish consumption, a portion of the highest oily (Atlantic mackerel, Scomber scombrus) and lean (haddock) fish species would provide two-thirds of the weekly recommended iodine intake (980 µg). In contrast, actual iodine intake from seafood consumption is estimated at only 9.4-18.0% of the UK reference nutrient intake (140 µg·day-1) across different age groups and genders, with females obtaining less than their male equivalents.

Endogenous production of n-3 long-chain PUFA from first feeding and the influence of dietary linoleic acid and the α-linolenic:linoleic ratio in Atlantic salmon (Salmo salar).

Atlantic salmon (Salmo salar) possess enzymes required for the endogenous biosynthesis of n-3 long-chain PUFA (LC-PUFA), EPA and DHA, from α-linolenic acid (ALA). Linoleic acid (LA) competes with ALA for LC-PUFA biosynthesis enzymes leading to the production of n-6 LC-PUFA, including arachidonic acid (ARA). We aimed to quantify the endogenous production of EPA and DHA from ALA in salmon fed from first feeding on diets that contain no EPA and DHA and to determine the influence of dietary LA and ALA:LA ratio on LC-PUFA production. Salmon were fed from first feeding for 22 weeks with three diets formulated with linseed and sunflower oils to provide ALA:LA ratios of approximately 3:1, 1:1 and 1:3. Endogenous production of n-3 LC-PUFA was 5·9, 4·4 and 2·8 mg per g fish and that of n-6 LC-PUFA was 0·2, 0·5 and 1·4 mg per g fish in salmon fed diets with ALA:LA ratios of 3:1, 1:1 and 1:3, respectively. The ratio of n-3:n-6 LC-PUFA production decreased from 27·4 to 2·0, and DHA:EPA ratio increased and EPA:ARA and DHA:ARA ratios decreased, as dietary ALA:LA ratio decreased. In conclusion, with a dietary ALA:LA ratio of 1, salmon fry/parr produced about 28 µg n-3 LC-PUFA per g fish per d, with a DHA:EPA ratio of 3·4. Production of n-3 LC-PUFA exceeded that of n-6 LC-PUFA by almost 9-fold. Reducing the dietary ALA:LA ratio reduced n-3 LC-PUFA production and EPA:ARA and DHA:ARA ratios but increased n-6 LC-PUFA production and DHA:EPA ratio.

Omega-3 Long-Chain Polyunsaturated Fatty Acids, EPA and DHA: Bridging the Gap between Supply and Demand.

The omega-3 (n-3) long-chain polyunsaturated fatty acids (LC-PUFA), eicosapentaenoic (EPA, 20:5n-3) and docosahexaenoic (DHA, 22:6n-3) acids, are well accepted as being essential components of a healthy, balanced diet, having beneficial effects on development and in mitigating a range of pathological conditions. However, their global supply from all the traditional sources of these nutrients is insufficient to satisfy human nutritional requirements. For two decades there has been considerable research carried out into all possible alternatives to the main sources of n-3 LC-PUFA, marine fish oil and fishmeal, driven largely by the aquaculture sector, as both the major user and provider of EPA and DHA. In the last few years these efforts have focused increasingly on the development of entirely new supplies of n-3 LC-PUFA produced de novo. Recently, this has resulted in various new sources of EPA and/or DHA that are already available or likely to available in the near future. In this short review, we briefly summaries the current gap between supply and demand of EPA and DHA for human requirements, the role of aquaculture in providing n-3 LC-PUFA to human consumers, the range of potential novel sources, and suggest how these new products could be used effectively. We conclude that all the new sources have potentially important roles to play in increasing the supply of n-3 LC-PUFA so that they are available more widely and in higher concentrations providing more options and opportunities for human consumers to obtain sufficient EPA and DHA to support more healthy, balanced diets.

Oil from transgenic Camelina sativa containing over 25 % n-3 long-chain PUFA as the major lipid source in feed for Atlantic salmon (Salmo salar).

Facing a bottleneck in the growth of aquaculture, and a gap in the supply and demand of the highly beneficial n-3 long-chain PUFA (LC-PUFA), sustainable alternatives to traditional marine-based feeds are required. Therefore, in the present trial, a novel oil obtained from a genetically engineered oilseed crop, Camelina sativa, that supplied over 25 % n-3 LC-PUFA was tested as a sole dietary-added lipid source in Atlantic salmon (Salmo salar) feed. Three groups of fish were fed three experimental diets for 12 weeks with the same basal composition and containing 20 % added oil supplied by either a blend of fish oil and rapeseed oil (1:3) (COM) reflecting current commercial formulations, wild-type Camelina oil (WCO) or the novel transgenic Camelina oil (TCO). There were no negative effects on the growth, survival rate or health of the fish. The whole fish and flesh n-3 LC-PUFA levels were highest in fish fed TCO, with levels more than 2-fold higher compared with those of fish fed the COM and WCO diets, respectively. Diet TCO had no negative impacts on the evaluated immune and physiological parameters of head kidney monocytes. The transcriptomic responses of liver and mid-intestine showed only mild effects on metabolism genes. Overall, the results clearly indicated that the oil from transgenic Camelina was highly efficient in supplying n-3 LC-PUFA providing levels double that obtained with a current commercial standard, and similar to those a decade ago before substantial dietary fishmeal and oil replacement.

The potential impact of compositional changes in farmed fish on its health-giving properties: is it time to reconsider current dietary recommendations?

Assessment of national dietary guidelines in a number of European countries reveals that some are based on cohort studies, focusing on total seafood consumption, while others are based on the content of EPA and DHA, distinguishing between oily and other fish. The mean actual intake of fish in most countries is around or below the recommended intake, with differences in intake of fish being present between sex and age groups. Many people do not reach the national recommendation for total fish intake. Dietary recommendations for fish and EPA/DHA are based mainly on data collected more than 10 years ago. However, methods of farmed fish production have changed considerably since then. The actual content of EPA and DHA in farmed salmon has nearly halved as the traditional finite marine ingredients fish meal and fish oil in salmon diets have been replaced with sustainable alternatives of terrestrial origin. As farmed salmon is an important source of EPA and DHA in many Western countries, our intake of these fatty acids is likely to have decreased. In addition, levels of vitamin D and Se are also found to have declined in farmed fish in the past decade. Significant changes in the EPA and DHA, vitamin D and Se content of farmed fish means that average intakes of these nutrients in Western populations are probably lower than before. This may have consequences for the health-giving properties of fish as well as future dietary recommendations for fish intake.

An oil containing EPA and DHA from transgenic Camelina sativa to replace marine fish oil in feeds for Atlantic salmon (Salmo salar L.): Effects on intestinal transcriptome, histology, tissue fatty acid profiles and plasma biochemistry.

New de novo sources of omega 3 (n-3) long chain polyunsaturated fatty acids (LC-PUFA) are required as alternatives to fish oil in aquafeeds in order to maintain adequate levels of the beneficial fatty acids, eicosapentaenoic and docosahexaenoic (EPA and DHA, respectively). The present study investigated the use of an EPA+DHA oil derived from transgenic Camelina sativa in Atlantic salmon (Salmo salar) feeds containing low levels of fishmeal (35%) and fish oil (10%), reflecting current commercial formulations, to determine the impacts on tissue fatty acid profile, intestinal transcriptome, and health of farmed salmon. Post-smolt Atlantic salmon were fed for 12-weeks with one of three experimental diets containing either a blend of fish oil/rapeseed oil (FO), wild-type camelina oil (WCO) or transgenic camelina oil (DCO) as added lipid source. The DCO diet did not affect any of the fish performance or health parameters studied. Analyses of the mid and hindgut transcriptomes showed only mild effects on metabolism. Flesh of fish fed the DCO diet accumulated almost double the amount of n-3 LC-PUFA than fish fed the FO or WCO diets, indicating that these oils from transgenic oilseeds offer the opportunity to increase the n-3 LC-PUFA in farmed fish to levels comparable to those found a decade ago.

Nutritional Evaluation of an EPA-DHA Oil from Transgenic Camelina sativa in Feeds for Post-Smolt Atlantic Salmon (Salmo salar L.).

Vegetable oils (VO) are possible substitutes for fish oil in aquafeeds but their use is limited by their lack of omega-3 (n-3) long-chain polyunsaturated fatty acids (LC-PUFA). However, oilseed crops can be modified to produce n-3 LC-PUFA such as eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, representing a potential option to fill the gap between supply and demand of these important nutrients. Camelina sativa was metabolically engineered to produce a seed oil with around 15% total n-3 LC-PUFA to potentially substitute for fish oil in salmon feeds. Post-smolt Atlantic salmon (Salmo salar) were fed for 11-weeks with one of three experimental diets containing either fish oil (FO), wild-type Camelina oil (WCO) or transgenic Camelina oil (DCO) as added lipid source to evaluate fish performance, nutrient digestibility, tissue n-3 LC-PUFA, and metabolic impact determined by liver transcriptome analysis. The DCO diet did not affect any of the performance or health parameters studied and enhanced apparent digestibility of EPA and DHA compared to the WCO diet. The level of total n-3 LC-PUFA was higher in all the tissues of DCO-fed fish than in WCO-fed fish with levels in liver similar to those in fish fed FO. Endogenous LC-PUFA biosynthetic activity was observed in fish fed both the Camelina oil diets as indicated by the liver transcriptome and levels of intermediate metabolites such as docosapentaenoic acid, with data suggesting that the dietary combination of EPA and DHA inhibited desaturation and elongation activities. Expression of genes involved in phospholipid and triacylglycerol metabolism followed a similar pattern in fish fed DCO and WCO despite the difference in n-3 LC-PUFA contents.

Thermochemistry of HO2 + HO2 → H2O4: Does HO2 Dimerization Affect Laboratory Studies?

Self-reaction is an important sink for the hydroperoxy radical (HO2) in the atmosphere. It has been suggested (Denis, P. A.; Ornellas, F. R. J. Phys. Chem. A, 2009, 113 (2), 499-506) that the minor product hydrogen tetroxide (HO4H) may act as a reservoir of HO2. Here, we compute the thermochemistry of HO2 self-reactions to determine if either HO4H or the cyclic hydrogen-bound dimer (HO2)2 can act as reservoirs. We computed electronic energies using coupled-cluster calculations in the complete basis set limit, CCSD(T)/CBS[45]//CCSD(T)/cc-pVTZ. Our model chemistry includes corrections for vibrational anharmonicity in the zero-point energy and vibrational partition functions, core-valence correlation, scalar relativistic effects, diagonal Born-Oppenheimer, spin-orbit splitting, and higher-order corrections. We compute the Gibbs energy of dimerization to be (-20.1 ± 1.6) kJ/mol at 298.15 K (2σ uncertainty), and (-32.3 ± 1.5) kJ/mol at 220 K. For atmospherically relevant [HO2] = 10(8) molecules per cm(3), our thermochemistry indicates that dimerization will be negligible, and thus H2O4 species are atmospherically unimportant. Under conditions used in laboratory experiments ([HO2] > 10(12) molecules per cm(3), 220 K), H2O4 formation may be significant. We compute two absorption spectra that could be used for laboratory detection of HO4H: the OH stretch overtone (near-IR) and electronic (UV) spectra.

High-resolution, vacuum-ultraviolet absorption spectrum of boron trifluoride.

In the course of investigations of thermal neutron detection based on mixtures of (10)BF3 with other gases, knowledge was required of the photoabsorption cross sections of (10)BF3 for wavelengths between 135 and 205 nm. Large discrepancies in the values reported in existing literature led to the absolute measurements reported in this communication. The measurements were made at the SURF III Synchrotron Ultraviolet Radiation Facility at the National Institute of Standards and Technology. The measured absorption cross sections vary from 10(-20) cm(2) at 135 nm to less than 10(-21) cm(2) in the region from 165 to 205 nm. Three previously unreported absorption features with resolvable structure were found in the regions 135-145 nm, 150-165 nm, and 190-205 nm. Quantum mechanical calculations, using the TD-B3LYP/aug-cc-pVDZ variant of time-dependent density functional theory implemented in Gaussian 09, suggest that the observed absorption features arise from symmetry-changing adiabatic transitions.

Cavity ringdown spectroscopy of the hydroxy-methyl-peroxy radical.

We report vibrational and electronic spectra of the hydroxy-methyl-peroxy radical (HOCH2OO(•) or HMP), which was formed as the primary product of the reaction of the hydroperoxy radical, HO2(•), and formaldehyde, HCHO. The ν1 vibrational (OH stretch) spectrum and the à ← X̃ electronic spectrum of HMP were detected by infrared cavity ringdown spectroscopy (IR-CRDS), and assignments were verified with density functional calculations. The HMP radical was generated in reactions of HCHO with HO2(•). Free radical reactions were initiated by pulsed laser photolysis (PLP) of Cl2 in the presence of HCHO and O2 in a flow reactor at 300-330 Torr and 295 K. IR-CRDS spectra were measured in mid-IR and near-IR regions over the ranges 3525-3700 cm(-1) (ν1) and 7250-7800 cm(-1) (à ← X̃) respectively, at a delay time 100 µs after photolysis. The ν1 spectrum had an origin at 3622 cm(-1) and exhibited partially resolved P- and R-branch contours and a small Q-branch. At these short delay times, spectral interference from HOOH and HCOOH was minimal and could be subtracted. From B3LYP/6-31+G(d,p) calculations, we found that the anharmonic vibrational frequency and band contour predicted for the lowest energy conformer, HMP-A, were in good agreement with the observed spectrum. In the near-IR, we observed four well spaced vibronic bands, each with partially resolved rotational contours. We assigned the apparent origin of the à ← X̃ electronic spectrum of HMP at 7389 cm(-1) and two bands to the blue to a progression in ν15', the lowest torsional mode of the à state (ν15' = 171 cm(-1)). The band furthest to the red was assigned as a hot band in ν15″, leading to a ground state torsional frequency of (ν15″ = 122 cm(-1)). We simulated the spectrum using second order vibrational perturbation theory (VPT2) with B3LYP/6-31+G(d,p) calculations at the minimum energy geometries of the HMP-A conformer on the X̃ and à states. The predictions of the electronic origin frequency, torsional frequencies, anharmonicities, and rotational band contours matched the observed spectrum. We investigated the torsional modes more explicitly by computing potential energy surfaces of HMP as a function of the two dihedral angles τHOCO and τOOCO. Wave functions and energy levels were calculated on the basis of this potential surface; these results were used to calculate the Franck-Condon factors, which reproduced the vibronic band intensities in the observed electronic spectrum. The transitions that we observed all involved states with wave functions localized on the minimum energy conformer, HMP-A. Our calculations indicated that the observed near-IR spectrum was that of the lowest energy X̃ state conformer HMP-A, but that this conformer is not the lowest energy conformer in the à state, which remains unobserved. We estimated that the energy of this lowest conformer (HMP-B) of the à state is E0 (Ã, HMP-B) ≈ 7200 cm(-1), on the basis of the energy difference E0(HMP-B) - E0(HMP-A) on the à state computed at the B3LYP/6-31+G(d,p) level.

Kinetics of n-butoxy and 2-pentoxy isomerization and detection of primary products by infrared cavity ringdown spectroscopy.

The primary products of n-butoxy and 2-pentoxy isomerization in the presence and absence of O(2) have been detected using pulsed laser photolysis-cavity ringdown spectroscopy (PLP-CRDS). Alkoxy radicals n-butoxy and 2-pentoxy were generated by photolysis of alkyl nitrite precursors (n-butyl nitrite or 2-pentyl nitrite, respectively), and the isomerization products with and without O(2) were detected by infrared cavity ringdown spectroscopy 20 µs after the photolysis. We report the mid-IR OH stretch (ν(1)) absorption spectra for δ-HO-1-C(4)H(8)•, δ-HO-1-C(4)H(8)OO•, δ-HO-1-C(5)H(10)•, and δ-HO-1-C(5)H(10)OO•. The observed ν(1) bands are similar in position and shape to the related alcohols (n-butanol and 2-pentanol), although the HOROO• absorption is slightly stronger than the HOR• absorption. We determined the rate of isomerization relative to reaction with O(2) for the n-butoxy and 2-pentoxy radicals by measuring the relative ν(1) absorbance of HOROO• as a function of [O(2)]. At 295 K and 670 Torr of N(2) or N(2)/O(2), we found rate constant ratios of k(isom)/k(O(2)) = 1.7 (±0.1) × 10(19) cm(-3) for n-butoxy and k(isom)/k(O(2)) = 3.4(±0.4) × 10(19) cm(-3) for 2-pentoxy (2σ uncertainty). Using currently known rate constants k(O(2)), we estimate isomerization rates of k(isom) = 2.4 (±1.2) × 10(5) s(-1) and k(isom) ≈ 3 × 10(5) s(-1) for n-butoxy and 2-pentoxy radicals, respectively, where the uncertainties are primarily due to uncertainties in k(O(2)). Because isomerization is predicted to be in the high pressure limit at 670 Torr, these relative rates are expected to be the same at atmospheric pressure. Our results include corrections for prompt isomerization of hot nascent alkoxy radicals as well as reaction with background NO and unimolecular alkoxy decomposition. We estimate prompt isomerization yields under our conditions of 4 ± 2% and 5 ± 2% for n-butoxy and 2-pentoxy formed from photolysis of the alkyl nitrites at 351 nm. Our measured relative rate values are in good agreement with and more precise than previous end-product analysis studies conducted on the n-butoxy and 2-pentoxy systems. We show that reactions typically neglected in the analysis of alkoxy relative kinetics (decomposition, recombination with NO, and prompt isomerization) may need to be included to obtain accurate values of k(isom)/k(O(2)).

Rate of gas phase association of hydroxyl radical and nitrogen dioxide.

The reaction of OH and NO(2) to form gaseous nitric acid (HONO(2)) is among the most influential in atmospheric chemistry. Despite its importance, the rate coefficient remains poorly determined under tropospheric conditions because of difficulties in making laboratory rate measurements in air at 760 torr and uncertainties about a secondary channel producing peroxynitrous acid (HOONO). We combined two sensitive laser spectroscopy techniques to measure the overall rate of both channels and the partitioning between them at 25°C and 760 torr. The result is a significantly more precise value of the rate constant for the HONO(2) formation channel, 9.2 (±0.4) × 10(-12) cm(3) molecule(-1) s(-1) (1 SD) at 760 torr of air, which lies toward the lower end of the previously established range. We demonstrate the impact of the revised value on photochemical model predictions of ozone concentrations in the Los Angeles airshed.

Effects of decontaminated fish oil or a fish and vegetable oil blend on persistent organic pollutant and fatty acid compositions in diet and flesh of Atlantic salmon ( Salmo salar).

The health benefits of seafood are well documented and based on the unique supply of n-3 highly unsaturated fatty acids (HUFA). Aquaculture now contributes about 50 % of food-grade seafood globally and Atlantic salmon (Salmo salar) is a rich source of n-3 HUFA. However, salmon and other oily fish can accumulate lipophilic persistent organic pollutants (POP), including dioxins (PCDD/F), polychlorinated biphenyls (PCB) and polybrominated diphenyl ethers (PBDE), derived largely from feed. In the present study, triplicate groups of salmon, of initial weight 0.78 kg, were fed one of three experimental diets for 11 weeks. The diets were coated with either a northern fish oil (FO) with a high POP content (cNFO), the same oil that had been decontaminated (deNFO) or a blend of southern fish oil, rapeseed and soyabean oils (SFO/RO/SO). Dietary PCDD/F+dioxin-like PCB (DL-PCB) concentrations were 17.36, 0.45 and 0.53 ng toxic equivalents (TEQ)/kg, respectively. After 11 weeks, the flesh concentrations in fish fed the cNFO, deNFO and SFO/RO/SO diets were 6.42, 0.34 and 0.41 ng TEQ/kg, respectively. There were no differences in flesh EPA and DHA between fish fed the cNFO or deNFO diets although EPA and DHA were reduced by 50 and 30 %, respectively, in fish fed the SFO/RO/SO diet. Thus, decontaminated FO can be used to produce salmon high in n-3 HUFA and low in POP. Salmon produced using deNFO would be of high nutritional value and very low in POP and would utilise valuable fish oils that would otherwise be destroyed due to their high pollutant concentrations.

The role of torsion/torsion coupling in the vibrational spectrum of cis-cis HOONO.

A three-dimensional model of the vibrational dynamics of HOONO is investigated. This model focuses on the couplings between the OH stretch vibration and the two torsions. The model is based on electronic energies, calculated at the CCSD(T)/cc-pVTZ level of theory and basis and dipole moment functions calculated at the CCSD/aug-cc-pVDZ level. The resulting points were fit to explicit functional forms, and the energies, wave functions, and intensities were evaluated using an approach in which the OH stretching motion was adiabatically separated from the torsional modes. It is found that the HOON torsion is strongly coupled to both the OONO torsion and OH stretch. Despite this, many of the conclusions that were drawn from earlier two-dimensional treatments, which did not include the OONO torsion, hold up on a semiquantitative level. In addition, we use this model to investigate the assignment of recently reported matrix isolated spectra of HOONO and DOONO. Finally, by comparing the results of this three-dimensional calculation to two-dimensional calculations and to the results of second-order perturbation theory, we investigate the question of how one determines the size of the reduced-dimensional system that is needed to describe the vibrational spectrum of molecules, like HOONO, that contain several large amplitude motions.

DNA-mediated delivery of lipophilic molecules via hybridization to DNA-based vesicular aggregates.

A scheme is presented for stabilizing hydrophobic molecules and releasing them into aqueous solution via DNA hybridization. A tetradecyl hydrophobic tail is covalently attached to synthetic oligomers, and the resulting amphiphilic molecules take up substantial amounts of orange OT and pyrene dyes in aqueous environments. The resulting structures do not affect the surface tension and are predominantly spherical as shown by light scattering and TEM, and the pyrene fluorescence is consistent with a hydrophobic environment. It is concluded that the amphiphilic DNA creates vesicular domains upon which the hydrophobic dyes reside and are stabilized in solution. Upon exposure to the complementary strand, the pyrene dye is released from the structures, showing that the scheme can be used for unlabeled or DNA-mediated drug delivery.