C8 C12 Research Articles

The effect of skin diffusion kinetics of isopropyl ester permeation enhancers on drug permeation: Role of lateral spread and penetration characteristics

The purpose of present work was to study the effects of permeation enhancers’ two kinetic behaviors of simultaneous lateral diffusion and vertical penetration in the skin on its enhancing effect. The skin diffusion kinetics of isopropyl ester permeation enhancers were characterized by the innovative concentric tape peeling study and Raman imaging, which were quantitatively assessed through innovative parameters, namely, lateral-to-vertical penetration amount (CL-V) and lateral-to-vertical penetration distance (DL-V). The enhancement effect of permeation enhancers on drug flurbiprofen (FLU) was assessed by in vitro skin permeation tests, which were confirmed by transdermal water loss and skin resistance study. The relationship between kinetic parameters of permeation enhancers and permeation parameters of FLU was carried out by correlation analysis. The molecular mechanisms of effect of skin diffusion kinetics of permeation enhancers on drug permeation were characterized by molecular docking, modulated-temperature differential scanning calorimetry (MTDSC), Raman spectra, solid-state NMR and molecular dynamic simulation. The results indicated skin diffusion kinetics of short-chain (C8–C12) isopropyl ester permeation enhancers were governed by vertical penetration, while long-chain (C14–C18) ones were characterized by lateral spread. Quadratic correlation between CL-V and enhancement ratio of permeation-retention ratio of FLU (ERQ/R) (R2 = 0.95), DL-V and enhancement ratio of permeation area (ERA) of FLU (R2 = 0.98) indicating that varied skin diffusion kinetics of permeation enhancers directly influenced the barrier function of stratum corneum (SC) and further enhancing drug permeation. In terms of molecular mechanism, long-chain isopropyl ester enhancers had good miscibility with SC, leading to their high CL-V and DL-V, and causing strong interaction strength with SC and resulting in weaker skin barrier function for drug permeation. In summary, in comparison to short-chain isopropyl ester enhancers that relied on penetration, long-chain ones that depended on lateral spread exhibited greater enhancement efficacy, which guided the application of enhancers in transdermal formulations.

Study of the influence of the gas circulation ratio on the production of C5–C18 alkenes in the Fischer–Tropsch synthesis

The process of producing C5+ hydrocarbons, including unsaturated ones, on a zeolite-containing catalyst Сo-Al2O3 /SiO2 /ZSM-5/Al2O3 in flow and flow-circulation modes of operation at a temperature of 250 °C, a pressure of 2.0 MPa, GHSV 1000 h–1 has been studied , H2 /CO ratio = 1.70 in the source gas and circulation ratios of 4, 8 and 16. It was determined that the process indicators (selectivity and productivity for C5+ products) pass through a maximum at a circulation ratio of 8. The use of gas circulation in comparison with flow synthesis mode allows you to regulate the composition of products. An increase in the circulation ratio in the range of 4–16 leads to an increase in the proportion of formed olefins with a hydrocarbon chain length containing 5–20 carbon atoms, from 53.9 wt.% up to 65.7 wt.%. The use of a zeolite-containing catalyst intensifies the formation of C8–C12 alkenes in comparison with the Co-Al2O3 /SiO2 catalyst by 3,3 times – the content increases from 13,5 wt.% up to 44.2 wt.% at similar values of circulation ratio, pressure and H2 /CO ratio = 1.70 in the source gas. It was found that as the circulation ratio increases, the rate of deactivation of the zeolite-containing catalyst decreases, which may be caused by a decrease in the partial pressure of water in the reaction volume.

Molecular-mass distribution of alkylphenolformaldehyde oligomers modified by imidazolines

The molecular weight distribution of monoalkyl(C8–C12)phenolformaldehyde oligomers modified with imidazolines based on sunfl ower or corn oil fatty acids and polyamines – diethylenetriamine, triethylenetetraamine, polyethylene polyamines was determined by gel-chromatography. The influence of the component and quantitative composition on the parameters of the number average and weight average molecular weights, as well as on the polydispersity of oligomers, was studied. Regularities have been revealed and assumptions have been made regarding repeating monoalkyl (C8-C12)phenol-formaldehyde fragments in the composition of oligomeric macromolecules.

Hydrocarbons (C8–C12) separation in porous metallocavitand M-PPX (M = Cu, Ag, Au): From computational insight

High throughput computational approach has been employed to investigate the adsorption and separation of C8–C12 hydrocarbons (HCs) on a tube-shaped metallocavitand, pillarplex (PPX). The Cu (I), Ag (I), and Au (I) seamed PPX and their HC complexes has been examined using density functional theory (DFT), proclaiming Cu-PPX has a higher binding affinity with the HCs whereas Ag-PPX is lower. The thermodynamic properties reveal the host–guest complex is stable at ambient condition. Noncovalent interaction (NCI) analysis shows the interaction of guests within the cavity of PPX is mainly attributed by Van der Waals type. The energy decomposition analysis (EDA) enunciates the percentage contribution of dispersion interaction (ΔEdisp) is 59–62%, the electrostatic (ΔEelct) and orbital (ΔEorb) terms have a moderate contribution towards the total binding energy. The Grand canonical Monte Carlo (GCMC) simulation manifests the Cu-PPX and Au-PPX are the ideal hosts with the optimum capacity to store HCs at ambient conditions. The octane uptake is 18.01, 17.50, and 25.31 cm3STP/g in Cu, Ag and Au-PPX and the uptake reduces upon increasing the HC chain length. The isosteric heat of adsorption (Qst) is corroborated with the computed DFT data at ambient setup. The ideal adsorption solution theory (IAST) claims the C8 selectivity in Cu, Ag and Au-PPX is optimum at 298 K and the increasing temperature from 298 K to 323 K, the selectivity of the C9 and C12 in Cu-PPX and Au-PPX, respectively is remarkable after the complete separation of C8. Hence Cu-PPX and Au-PPX is the potential candidate for industrial use to separate the heavy HCs.

Investigation of the structure and mechanism of the synthesis reaction of monoalkyl(C<sub>8</sub>-C<sub>12</sub>)phenol formaldehyde oligomers modified by imidazolines based on fatty acids of vegetable oils and polyamines by the IR-spectroscopy method

The structures of novolac monoalkyl(C8–C12)phenolformaldehyde oligomers modified with imidazolines based on fatty acids of sunflower or corn oils and polyamines – diethylenetriamine, triethylenetetraamine, polyethylenepolyamines were investigated by IR-spectroscopy. As a result of the analysis of the initial and final products, a reaction mechanism is proposed. Optical densities of the absorption bands of the main functional fragments were calculated, and the regularities of the changes depending on the qualitative and quantitative composition of the oligomers were studied.

Средне-щелочные алкилфенолятные присадки

The article presents the results of research on the sintesis of medium alkaline alkylphenolate additives. Additives are calcium salts of the condensation products of alkylphenols with formaldehyde and ammonia or various amines (monoethanolamine, benzylamine and allylamine) have been synthesized and studied. The physicochemical and functional properties of the synthesized products were studied by standard methods.It has been shown that all aminomethyl derivatives of alkylphenols have multifunctional properties and are superior to their analogs ИХП-101, ИХП-109 and ВНИИНП-370 in terms of their functional properties. In addition, the additives obtained on the basis of nonylphenol in terms of anticorrosion and antioxidant properties are somewhat superior to those obtained on the basis of alkylphenol (C8–C12) due to their homogeneous composition. Thus, all synthesized compounds are multifunctional, and additives containing a secondary nitrogen atom (calcium salt of dialkyldioxybenzylamine) and a benzyl radical at the nitrogen atom (calcium salt of N-benzyldialkyldioxybenzylamine) have the highest antioxidant efficiency.

Pseudomonas veronii strain 7–41 degrading medium-chain n-alkanes and polycyclic aromatic hydrocarbons

Pollution of the environment by crude oil and oil products (represented by various types of compounds, mainly aliphatic, mono- and polyaromatic hydrocarbons) poses a global problem. The strain Pseudomonas veronii 7–41 can grow on medium-chain n-alkanes (C8–C12) and polycyclic aromatic hydrocarbons such as naphthalene. We performed a genetic analysis and physiological/biochemical characterization of strain 7–41 cultivated in a mineral medium with decane, naphthalene or a mixture of the hydrocarbons. The genes responsible for the degradation of alkanes and PAHs are on the IncP-7 conjugative plasmid and are organized into the alk and nah operons typical of pseudomonads. A natural plasmid carrying functional operons for the degradation of two different classes of hydrocarbons was first described. In monosubstrate systems, 28.4% and 68.8% of decane and naphthalene, respectively, were biodegraded by the late stationary growth phase. In a bisubstrate system, these parameters were 25.4% and 20.8% by the end of the exponential growth phase. Then the biodegradation stopped, and the bacterial culture started dying due to the accumulation of salicylate (naphthalene-degradation metabolite), which is toxic in high concentrations. The activity of the salicylate oxidation enzymes was below the detection limit. These results indicate that the presence of decane and a high concentration of salicylate lead to impairment of hydrocarbon degradation by the strain.

Separation of Alcohols from n-Tetradecane Using 1-Ethyl-3-methylimidazolium Hydrogensulfate

Extraction of alcohols from n-tetradecane using various extraction solvents has been investigated at a range of temperatures from 295 to 393 K under ambient pressure. On the basis of the experimental liquid–liquid equilibrium data, the distribution ratio and selectivity were calculated for the extraction of 1-octanol, 1-decanol, and 1-dodecanol (C8–C12) in 1-ethyl-3-methylimidazolium hydrogensulfate [C2mim][HSO4] and sulfolane. Results showed that moderate selectivities were obtained in sulfolane with very low distribution coefficients. In contrast, [C2mim][HSO4] showed similar selectivity values with higher distribution coefficients. A study of a number of different 1-alcohols (C4–C12) showed that the decrease in hydrogen bonding compared to the increased van der Waals interactions between n-tetradecane and the higher-chain alcohols decreased the extraction selectivity in [C2mim][HSO4]. Increasing the temperature of the ionic liquid extraction medium resulted in increased chemical extraction for 1-butanol and 1-hexanol due to the formation of the corresponding alkylsulfate ionic liquid. In contrast, the selectivity decreased for 1-octanol, 1-decanol and 1-dodecanol due to the partial dissolution of the corresponding alkylsulfate ionic liquid into the n-tetradecane phase.

Efficient production of mannosylerythritol lipids by a marine yeast Moesziomyces aphidis XM01 and their application as self-assembly nanomicelles

Mannosylerythritol lipids (MELs) are one of the most promising biosurfactants because of their excellent physicochemical properties, high environmental compatibility, and various biological functions. In this study, a mangrove yeast strain Moesziomyces aphidis XM01 was identified and used for efficient extracellular MEL production. The MEL titer reached 64.5 ± 0.7 g/L at flask level within 7 days with the optimized nitrogen and carbon source of 2.0 g/L NaNO3 and 70 g/L soybean oil. Furthermore, during a 10-L two-stage fed-batch fermentation, the final MEL titer reached 113.6 ± 3.1 g/L within 8 days, with prominent productivity and yield of 14.2 g·L−1·day−1 and 94.6 g/g(glucose and soybean oil). Structural analysis indicated that the produced MELs were mainly MEL-A and its fatty acid profile was composed of only medium-chain fatty acids (C8–C12), especially C10 acids (77.81%). Further applications of this compound were evaluated as one-step self-assembly nanomicelles. The obtained MEL nanomicelles showed good physicochemical stability and antibacterial activity. In addition, using clarithromycin as a model hydrophobic drug, the MEL nanomicelles exhibited high loading capacity and could be used for the controlled and sustained drug release in low-pH environments. Therefore, M. aphidis XM01 is an excellent candidate for efficient MEL production, and the prepared MEL nanomicelles have broad application prospects in the pharmaceutical and cosmetic fields.

Efficacy of Enriched Medium-chain Fatty Acids in Virgin Coconut Oil in Their Antibacterial Activity against Food Pathogens

Free fatty acids (FFA) have been previously shown to be an effective bactericidal agent. In this study, the FFA mixture was attempted to isolate from virgin coconut oil (VCO) using lipases and was fractionated to obtain the enriched medium-chain fatty acids (MCFA) to compare its antibacterial efficacy against food pathogens. Three types of lipases – namely, lipozyme TL 100L, Candida rugosa lipase (CRL), and porcine pancreas lipase (PPL) – were used to compare their efficacy in VCO hydrolysis, in which CRL was found to be the most efficient lipase for the process of VCO hydrolysis at the water: buffer ratio of 1:5, lipase concentration of 5310 U/g, pH 7, and temperature of 40 °C. The vacuum-distillation process was successfully found to fractionate the initial FFA into three fractions: Fraction I containing MCFA (C8–C12) plus Fraction II (C12–C14) and Fraction III containing LCFA (C14–C20). Among these fractions, Fraction I was observed to be the most effective anti-agent against four out of five food pathogens (negative result against Salmonella typhimurium), followed by Fraction II and initial FFA. Antimicrobial activities of study fractions were found effective on both Gram-positive strains and Gram-negative strains.

Highly Selective Conversion of CO2 or CO into Precursors for Kerosene-Based Aviation Fuel via an Aldol–Aromatic Mechanism

The extensive emission of CO2 into the atmosphere due to the burning of fossil fuels has urged many countries to move toward decarbonized energy. Based on the concept of carbon neutrality, the European Union Emissions Trading System implemented the aviation carbon tax (ACT), which stimulated the rapid transformation in aviation fuels. To cope with the ACT and mitigate the CO2 emissions from the aviation industry, here, we present a promising route for the synthesis of precursors such as aromatics, alkyl benzenes, and naphthenes, which account for 40–50 vol % fraction of the kerosene-based aviation fuel, from waste CO2 or biomass-derived syngas. The ultra-high selectivity of single-ring aromatics (precursors for the kerosene-based aviation fuel) with a selective range of carbon chain numbers (C8–C12) was achieved (>80% in hydrocarbons at a reaction temperature of 275 °C) via the catalytic hydrogenation of CO2 or CO over a bifunctional catalyst (nano-sized ZnCr2O4/Sbx-H-ZSM-5). In situ diffuse reflectance infrared Fourier transform spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, gas chromatography–mass spectrometry, and reaction analysis revealed that the product distribution was controlled by thermodynamics and the formation of the aromatics followed an “aldol–aromatic” mechanism. The high selectivity of aromatics at the low reaction temperature (i.e., 275 °C) was attributed to the catalyst topology, the closed carbon chain aromatization reaction, and the presence of highly active oxygenated species in the hydrocarbon pool. For the first time, an asymmetric desorption behavior between the active oxygenate species and aromatic hydrocarbons over the ZnCr2O4/Sbx-H-ZSM-5 catalyst is reported with the help of integrated differential phase contrast scanning transmission electron microscopy, which made the reaction highly selective toward aromatics. This strategy gives a carbon-neutral route for the synthesis of kerosene-based aviation fuel precursors and will reduce the burden of the carbon tax on the aviation industry.

Tandem Synthesis of Ultra-High Molecular Weight Drag Reducing Poly-α-Olefins for Low-Temperature Pipeline Transportation.

Ultra-high molecular weight poly-α-olefins are widely used as drag reducing agents (DRAs) for pipeline transportation of oil and refined petroleum products. The synthesis of polyolefin DRAs is based on low-temperature Ziegler–Natta (ZN) polymerization of higher α-olefins. 1-Hexene based DRAs, the most effective at room temperature, typically lose DR activity at low temperatures. The use of 1-hexene copolymers with C8–C12 linear α-olefins appears to offer a solution to the problem of low-temperature drag reducing. The present work aims to develop two-stage synthesis of polyolefin DRAs that is based on selective oligomerization of ethylene in the presence of efficient chromium/aminodiphosphine catalysts (Cr-PNP), followed by polymerization of the olefin mixtures, formed at oligomerization stage, using efficient titanium–magnesium ZN catalyst. We have shown that oligomerization of ethylene in α-olefin reaction media proceeds faster than in saturated hydrocarbons, providing the formation of 1-hexene, 1-octene, and branched C10 and C12 olefins; the composition and the ratio of the reaction products depended on the nature of PNP ligand. Oligomerizates were used in ZN polymerization ‘as is’, without additional treatment. Due to branched character of C10+ hydrocarbons, formed during oligomerization of ethylene, resulting polyolefins demonstrate higher low-temperature DR efficiency at low polymer concentrations (~1 ppm) in comparison with benchmark polymers prepared from the mixtures of linear α-olefins and from pure 1-hexene. We assume that faster solubility and more efficient solvation of the polyolefins, prepared using ‘tandem’ ethylene-based process, represent an advantage of these type polymers over conventional poly(1-hexene) and linear α-olefin-based polymers when used as ‘winter’ DRAs.

Investigating the Uptake and Fate of Poly- and Perfluoroalkylated Substances (PFAS) in Sea Ice Using an Experimental Sea Ice Chamber.

Poly- and perfluoroalkyl substances (PFAS) are contaminants of emerging Arctic concern and are present in the marine environments of the polar regions. Their input to and fate within the marine cryosphere are poorly understood. We conducted a series of laboratory experiments to investigate the uptake, distribution, and release of 10 PFAS of varying carbon chain length (C4–C12) in young sea ice grown from artificial seawater (NaClsolution). We show that PFAS are incorporated into bulk sea ice during ice formation and regression analyses for individual PFAS concentrations in bulk sea ice were linearly related to salinity (r2 = 0.30 to 0.88, n = 18, p < 0.05). This shows that their distribution is strongly governed by the presence and dynamics of brine (high salinity water) within the sea ice. Furthermore, long-chain PFAS (C8–C12), were enriched in bulk ice up to 3-fold more than short-chain PFAS (C4–C7) and NaCl. This suggests that chemical partitioning of PFAS between the different phases of sea ice also plays a role in their uptake during its formation. During sea ice melt, initial meltwater fractions were highly saline and predominantly contained short-chain PFAS, whereas the later, fresher meltwater fractions predominantly contained long-chain PFAS. Our results demonstrate that in highly saline parts of sea ice (near the upper and lower interfaces and in brine channels) significant chemical enrichment (ε) of PFAS can occur with concentrations in brine channels greatly exceeding those in seawater from which it forms (e.g., for PFOA, εbrine = 10 ± 4). This observation has implications for biological exposure to PFAS present in brine channels, a common feature of first-year sea ice which is the dominant ice type in a warming Arctic.

Milk Composition of Free-Ranging Impala (Aepyceros melampus) and Tsessebe (Damaliscus lunatus lunatus), and Comparison with Other African Bovidae.

Simple SummaryUntil now, the milk composition of impala and tsessebe has been unknown. Our study showed that the composition of impala milk was 5.56 ± 1.96% fat, 6.60 ± 0.51% protein, and 4.36 ± 0.94% lactose, and that of tsessebe milk was 8.44 ± 3.19%, 5.15 ± 0.49%, and 6.10 ± 3.85%, respectively. The fatty acid composition and protein properties also differed. The data of these two species were subjected to an interspecies comparison with 13 other antelope species by statistical methods. This showed that the milk of tsessebe is similar to that of its relatives of the Alcelaphinae sub-family. Although the impala is a close relative of the Alcelaphinae, its milk composition finds comparison with a different sub-class, the Hippotraginae. The information contributes to the phylogenetic properties of milk and milk evolution.The major nutrient and fatty acid composition of the milk of impala and tsessebe is reported and compared with other Bovidae and species. The proximate composition of impala milk was 5.56 ± 1.96% fat, 6.60 ± 0.51% protein, and 4.36 ± 0.94% lactose, and that of tsessebe milk was 8.44 ± 3.19%, 5.15 ± 0.49%, and 6.10 ± 3.85%, respectively. The high protein content of impala milk accounted for 42% of gross energy, which is typical for African Bovids that use a “hider” postnatal care system, compared to the 25% of the tsessebe, a “follower”. Electrophoresis showed that the molecular size and surface charge of the tsessebe caseins resembled that of other Alcelaphinae members, while that of the impala resembled that of Hippotraginae. The milk composition of these two species was compared by statistical methods with 13 other species representing eight suborders, families, or subfamilies of African Artiodactyla. This showed that the tsessebe milk resembled that of four other species of the Alcelaphinae sub-family and that the milk of this sub-family differs from other Artiodactyla by its specific margins of nutrient contents and milk fat with a high content of medium-length fatty acids (C8–C12) above 17% of the total fatty acids.

Atmospheric particulate represents a source of C8-C12 perfluoroalkyl carboxylates and 10:2 fluorotelomer alcohol in tree bark.

In this study, we analyzed 30 legacy and emerging poly- and perfluoroalkyl substances (PFASs) in paired atmospheric particulate and bark samples collected around a Chinese fluorochemical manufacturing park (FMP), with the aim to explore the sources of PFASs in tree bark. The results showed that PFASs in atmospheric particulate and tree bark samples were consistently dominated by perfluorooctanoate (mean 73ng/g; 44pg/m3), perfluorohexanoate (47ng/g; 36pg/m3), perfluorononanoate (9.1ng/g; 8.8pg/m3), and 10:2 fluorotelomer alcohol (10:2 FTOH; 5.6ng/g; 12pg/m3). Spatially, concentrations of C8-C12 perfluoroalkyl carboxylates (PFCAs) and 10:2 FTOH all showed a similar and exponentially decreased trend in both bark and atmospheric particulate samples with the increasing distance from the FMP. For the first time, we observed strongly significant (Spearman's correlation coefficient=0.53-0.79, p<0.01) correlations between bark and atmospheric particulate concentrations for C8-C12 PFCAs and 10:2 FTOH over 1-2 orders of magnitude, suggesting that the continues trapping of atmospheric particulates resulted in the accumulation of these compounds in bark. Overall, this study provides the first evidence that atmospheric particulate is an obvious source of C8-C12 PFCAs and 10:2 FTOH in tree bark. This result may further contribute to the application of tree bark as an indicator of certain PFASs in atmospheric particulate.

Perceptual Quality of Nonesterified Fatty Acids Varies with Fatty Acid Chain Length.

Nonesterified fatty acids (NEFA) are effective taste stimuli. The quality they impart has not been well characterized. Sourness, and "fattiness" have been reported, but an irritation component has also been described and how these transition with gradations of aliphatic chain length has not been systematically studied. This study examined intensity and quality ratings of NEFA ranging from C2 to C18. Oral sites and the time course of sensations were also monitored. Given all NEFA contain carboxylic acid moieties capable of donating hydrogen ions, the primary stimulus for sour taste, testing was conducted with and without sour adaptation to explore the contribution of sour taste across the range of NEFA. Short-chain NEFA (C2-C6) were rated as predominantly sour, and this was diminished in C2 and C4 by sour adaptation. Medium-chain NEFA (C8-C12) were rated as mainly irritating with long-chain NEFA (C18) described mostly as bitter. The latter may reflect the lack of "fatty" lexicon to describe the sensation. Short-chain NEFA were mostly localized to the anterior tongue and were of rapid onset. The sensation from medium-chain NEFA was attributed to the lateral tongue, whereas medium- and long-chain NEFA sensations were predominantly localized to the back of the tongue and throat and had a longer lag time. The findings indicate there is a systematic transition of NEFA taste quality and irritation with increments in chain length and this is consistent with multiple modes of transduction.

Molecular Distributions of Diacids, Oxoacids, and α‐Dicarbonyls in Summer‐ and Winter‐Time Fine Aerosols From Tianjin, North China: Emissions From Combustion Sources and Aqueous Phase Secondary Formation

AbstractTo understand the characteristics and sources of organic aerosols (OA) in North China, we studied diacids, oxoacids, and α‐dicarbonyls in summer‐ and winter‐time fine aerosols (PM2.5) collected from Tianjin. Oxalic (C2) acid was found to be the most abundant diacid species, followed by succinic (C4), malonic (C3), and sebacic (C8) acids, respectively. Glyoxylic (ωC2) was the most abundant oxoacids followed by pyruvic acid. Concentrations of total diacids, oxoacids, and α‐dicarbonyls in winter were 2–3 times higher than those in summer, but their mass fractions in PM2.5 were exactly the opposite. On average, total diacids carbon accounted for 2.9% in total carbon and 3.3% in organic carbon (OC) in summer and 1.8% and 2.0%, respectively, in winter. Their contributions to water‐soluble OC (WSOC) was almost the same in both seasons (5.5% and 5.3%, respectively). Molecular distributions, mass ratios of selected diacid (C3, C4, M, F, C6, Ph, and C9) species, and the linear relations among the selected species (including ∑C2–C4 and ∑C8–C12) and with inorganic markers (K+ and SO42−) implied that the diacids and related compounds are mainly originated from coal combustion and biomass burning emissions and produced in the atmosphere by both in situ photochemical reactions at local scale and aging during long‐range transport in both summer and winter. This study revealed that diacids and related compounds and WSOC are increased with increasing SO42− and they are produced in the aqueous phase, implying that the reduction in NOx and SO2 emissions could possibly control the water‐soluble OA loading over North China.

Temporal and spatial discrepancies of VOCs in an industrial-dominant city in China during summertime

Ozone (O3) pollution is currently problematic to cities across the globe. Many non-methane hydrocarbons (NMHCs) are efficient O3 precursors. In this study, target volatile organic compounds (VOCs), including oxygenated VOCs (known as carbonyls), were monitored at eight sampling sites distributed in urban and suburban in the typical and industrial-dominant city of Shaoxing, Zhejiang province, China. At the suburban sites, C8–C12 alkanes, aromatics with lower reactivity (kOH <13 × 10−12 cm3 mol−1 s−1) and acetonitrile were more abundant than urban ones due to higher emissions from diesel-fueled trucks and biomass burning. In general, higher abundances of total quantified NMHCs (ΣNMHC) were found on high O3 (HO) days. The increments of formaldehyde (C1) and O3 were higher in urban than suburban, while a reverse trend was seen for acetaldehyde (C2). Substantial and local biogenic inputs of C2 were found in suburban in the afternoon when both temperature and light intensity reached maximum of the day. In urban, higher increment was found for O3 than the carbonyls, representing that the secondary formation of O3 was more efficient. Distance decay gradient of most representative NMHCs were positively correlated to the distances from a westernmost industrial origin located at the upwind location. The net loss rates of the NMHCs ranged from −0.009 to −0.11 ppbv km−1, while the higher rates were seen for the most reactive species like C2–C4 alkenes. The results and interpretation of this study are informative to establish efficient local control measures for O3 and the related percussors for the microscale industrial cities in China.

Legacy and emerging per- and polyfluoroalkyl substances (PFASs) in multi-media around a landfill in China: Implications for the usage of PFASs alternatives

To date, per- and polyfluoroalkyl substances (PFASs) in environmental media surrounding landfills have not attracted much attention. In this study, six legacy PFASs, six short-chain analogues and five emerging alternatives were investigated in groundwater, surface water and sediment samples taken in the vicinity of a valley-type landfill, which had been in operation for over 20 years. Total PFAS concentrations of 110–236 ng/L, 17.3–163 ng/L and 7.91–164 ng/g dw were detected in the surface water, groundwater and sediment samples, respectively. Overall, perfluorooctanoic acid (PFOA) was the dominant PFAS in surface water, but elevated concentrations of perfluorobutanoic acid (PFBA) and perfluoropentanoic acid (PFPeA) were detected in the surface water samples taken adjacent to the landfill, suggesting that the landfill contributed to these compounds. PFBA was the dominant PFAS in the groundwater and sediments. The concentrations of long-chain perfluoroalkyl carboxylic acids (PFCAs) (C8–C12) in the sediment samples correlated significantly with the TOC, Al2O3 and Fe2O3 contents. The partitioning behaviors of PFCAs in the water-sediment system varied depending on the CF2 moiety units. For the long-chain PFCAs, positive correlations between the average LogKd and the number of CF2 moieties were found to be statistically significant, whereas negative correlations were observed for the short-chain PFCAs (C4–C7). The ratios of short-chain analogues and emerging alternatives versus their respective legacy PFOA and perfluorooctane sulfonate (PFOS) in surface water suggested an increasing trend of short-chain analogues, such as PFBA. The potential health risks of PFOS and PFOA, determined by calculating the estimated daily intake (EDI), were found to be negligible via the drinking groundwater exposure pathway, but more comprehensive studies on the human health risks of PFASs from landfills are essential.

Novel Cyclic Lipopeptide Antibiotics: Effects of Acyl Chain Length and Position.

Multidrug-resistant bacteria are a global health problem. One of the last-resort antibiotics against Gram-negative bacteria is the cyclic lipopeptide colistin, displaying a flexible linker with a fatty acid moiety. The aim of the present project was to investigate the effect on antimicrobial activity of introducing fatty acid moieties of different lengths and in different positions in a cyclic peptide, S3(B), containing a flexible linker. The lipidated analogues of S3(B) were synthesized by 9-fluorenylmethoxycarbonyl (Fmoc) solid-phase peptide synthesis. Following assembly of the linear peptide by Fmoc solid-phase peptide synthesis, on-resin head-to-tail cyclization and fatty acid acylation were performed. The antimicrobial activity was determined against the ESKAPE pathogens, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli. Furthermore, hemolytic activity was determined against human erythrocytes. A total of 18 cyclic lipopeptides were synthesized and characterized. It was found that introduction of fatty acids in positions next to the flexible linker was more strongly linked to antimicrobial activity. The fatty acid length altered the overall hydrophobicity, which was the driving force for both high antimicrobial and hemolytic activity. Peptides became highly hemolytic when carbon-chain length exceeded 10 (i.e., C10), overlapping with the optimum for antimicrobial activity (i.e., C8–C12). The most promising candidate (C8)5 showed antimicrobial activity corresponding to that of S3(B), but with an improved hemolytic profile. Finally, (C8)5 was further investigated in a time-kill experiment.