Shorter Chain Fatty Acids Research Articles

Variation of Photosynthesis, Fatty Acid Composition, ATPase and Acid Phosphatase Activities, and Anatomical Structure of Two Tea (Camellia sinensis (L.) O. Kuntze) Cultivars in Response to Fluoride

The changes of photosynthetic parameters, water use efficiency (WUE), fatty acid composition, chlorophyll (Chl) content, malondialdehyde (MDA) content, ATPase and acid phosphatase activities, fluoride (F) content, and leaf anatomical structure of two tea cultivars, “Pingyangtezao” (PY) and “Fudingdabai” (FD), after F treatments were investigated. The results show that net photosynthetic rate (P n), stomatal conductance (g s), and transpiration rate (E) significantly decreased in both cultivars after 0.3 mM F treatment, but FD had higher P n, g s, and WUE and lower E than PY. Chl content in PY significantly decreased after 0.2 and 0.3 mM F treatments, while no significant changes were observed in FD. The proportions of shorter chain and saturated fatty acids increased and those of longer chain and unsaturated fatty acids decreased in both cultivars under F treatments. The contents of MDA increased after F treatments but were higher in PY than in FD. In addition, F treatments decreased the activities of ATPase and acid phosphatase and increased F content in both cultivars; however, compared with PY, FD showed higher enzymatic activities and lower F content in roots and leaves. Leaf anatomical structure in FD indicated that cells in leaf midrib region were less injured by F than in PY.

PHARMACEUTICO-ANALYTICAL STUDY OF TRIVIDHA SNEHA PAKA OF KSHEERA BALA TAILA

To assess the differences between trividha paka of Ksheera bala taila namely Mrudu paka, Madhya paka and Khara paka it was subjected to pharmaceutical and analytical studies through organoleptic, physico-chemical and chromatographical methods. The results were significant which revealed. Pharmaceutical study with maximum output of Ksheera bala taila obtained in Mrudu paka and minimum output in Khara paka. Analytical study revealed maximum extraction of unchanged-form active principles found in Madhya paka through the chromatographical method (HPTLC) and refractive index. Saponification value revealed shorter, medium and longer chain fatty acids presence in the Khara paka, Madhya paka and Mrudu paka respectively which has importance in its unique rate of absorption into the body.

Altered Fatty Acid Metabolism Due to Rifampicin-Resistance Conferring Mutations in therpoBGene ofMycobacterium tuberculosis: Mapping the Potential of Pharmaco-metabolomics for Global Health and Personalized Medicine

Abstract We investigated the use of gas chromatography mass spectrometry (GC-MS) metabolomics to better characterize rifampicin-resistance by comparing the fatty acid metabolomes of two rpoB mutant Mycobacterium tuberculosis strains (S522L and S531L) to that of a fully susceptible wild-type parent strain. Using the generated GC-MS metabolite data, principal component analysis (PCA) showed a clear differentiation between all three sample groups analyzed. We subsequently identified those metabolites contributing most to the variation in the data using PCA and partial least squares discriminant analysis (PLS-DA). The altered metabolite markers detected in the rifampicin-resistant mutants indicate a decreased synthesis of various 10-methyl branched-chain fatty acids and cell wall lipids, and an increased use of the shorter-chain fatty acids as carbon sources. Furthermore, the rpoB S531L mutant, previously reported to occur in well over 70% of all clinical rifampicin-resistant M. tuberculosis strains, potentially showed a better capacity for using these alternative energy sources, compared to the less frequently detected rpoB S522L mutant. This study is the first of its kind to associate rifampicin resistance, rpoB mutations, and the β-subunit of RNA polymerase in M. tuberculosis, with an altered fatty acid metabolism, thereby demonstrating the role that pharmaco-metabolomics can play in identifying new markers associated with drug resistance.

Dietary Fatty Acid Intake and Prostate Cancer Survival in Orebro County, Sweden

Although dietary fat has been associated with prostate cancer risk, the association between specific fatty acids and prostate cancer survival remains unclear. Dietary intake of 14 fatty acids was analyzed in a population-based cohort of 525 Swedish men with prostate cancer in Örebro County (1989-1994). Multivariable hazard ratios and 95% confidence intervals for time to prostate cancer death by quartile and per standard deviation increase in intake were estimated by Cox proportional hazards regression. Additional models examined the association by stage at diagnosis (localized: T0-T2/M0; advanced: T0-T4/M1, T3-T4/M0). Among all men, those with the highest omega-3 docosahexaenoic acid and total marine fatty acid intakes were 40% less likely to die from prostate cancer (P(trend) = 0.05 and 0.04, respectively). Among men with localized prostate cancer, hazard ratios of 2.07 (95% confidence interval: 0.93, 4.59; P(trend) = 0.03) for elevated total fat, 2.39 (95% confidence interval: 1.06, 5.38) for saturated myristic acid, and 2.88 (95% confidence interval: 1.24, 6.67) for shorter chain (C4-C10) fatty acid intakes demonstrated increased risk for disease-specific mortality for the highest quartile compared with the lowest quartile. This study suggests that high intake of total fat and certain saturated fatty acids may worsen prostate cancer survival, particularly among men with localized disease. In contrast, high marine omega-3 fatty acid intake may improve disease-specific survival for all men.

Negative allometry of docosahexaenoic acid in the fowl lung and pulmonary surfactant phospholipids

In a recent study (Comp. Biochem. Physiol. B. (2010)155: 301-308) we reported that the fatty acids (FA) of the avian (7 species) total lung phospholipids (PL) (i.e. lung parenchyma and surfactant together) provide allometric properties. To test whether this allometric scaling also occurs in either of the above components, in six gallinaceous species, in a body weight range from 150 g (Japanese quail, Coturnix coturnix japonica) to 19 kg (turkey, Meleagris gallopavo) the PL FA composition (mol%) was determined in the pulmonary surfactant, in native and in thoroughly lavaged lungs (referred to as lung parenchyma). In all three components docosahexaenoic acid (DHA) showed significant and negative allometric scaling (B = -0.056, -0.17 and -0.1, respectively). Surfactant PLs provided further negative allometry for palmitic acid and the opposite was found for palmitoleate and arachidonate. In the lung parenchymal PLs increasing body weight was matched with shorter chain FAs (average FA chain length) and competing n6 and n3 end-product fatty acids (positive allometry for arachidonic acid and negative for DHA). Negative allometric scaling was found for the tissue malondialdehyde concentration in the native and lavaged lungs (B = -0.1582 and -0.1594, respectively). In these tissues strong correlation was found between the MDA concentration and DHA proportion (r = 0.439 and 0.679, respectively), denoting the role of DHA in shaping the allometric properties and influencing the extent of in vivo lipid peroxidation of membrane lipids in fowl lungs.

Changes over time in muscle fatty acid composition of Malaysian mahseer, Tor tambroides, fed different dietary lipid percentage

The effects of four isonitrogenous diets containing different lipid levels on the muscle fatty acid profiles of Malaysian mahseer were evaluated over a period of six weeks from June to July, 2010. A general increase of monounsaturated fatty acid contents in the muscle of fish that were fed the test diets was detected after two weeks. Despite the high total content of long chain n-3 polyunsaturated fatty acid (PUFA) in the formulated diets, the levels of these fatty acids in the muscle did not increase and it may be speculated that the content of long chain n-3 PUFAs in this species was determined by desaturation and elongation of shorter chain fatty acids rather than direct absorption from the diet. Moreover, reduction of muscle n-3 PUFA content after six weeks of feeding showed that a diet containing high level of n-3 PUFA may not be able to provide all the essential fatty acid requirements of T. tambroides .

Preparation and Characterization of Tributyrin Sub-micron Emulsion as Carrier for Paclitaxel

ABSTRACT − Paclitaxel is a well known anticancer agent and has been a pharmaceutical challenge because of itsextremely poor water-solubility and susceptibility to the p-glycoprotein (p-gp)-mediated efflux in multi-drug resistant(MDR) cancer cells. Tributyrin (TB), a triglyceride with relatively short fatty acid chains, was chosen as solubilizing vehiclefor paclitaxel based on the solubility study (26.6 mg/mL). Tributyrin (10%) o/w emulsion containing paclitaxel (5%), eggphosphatidylcholine (5%) and pegylated phospholipid (0.5%) was prepared by high pressure homogenization to obtain sub-micron-sized emulsion. The mean particle size of the resultant TB emulsion was 395.5 nm. Paclitaxel in TB emulsionshowed higher anticancer activity against human breast cancer cell line, MCF-7, than free form delivered in DMSO solution.On the other hand, its anticancer activity was significantly reduced in MCF-7/ADR, a MDR variant cancer cell line of MCF-7, and recovered by the presence of verapamil, suggesting of the susceptibility to the p-gp mediated efflux even thoughpaclitaxel was encapsulated into emulsion. The TB emulsion showed great potential as a promising vehicle for water-insol-uble anticancer agent, paclitaxel.Key words

Polyphenol fatty acid esters as serine protease inhibitors: a quantum-chemical QSAR analysis

We investigated the ability of polyphenol fatty acid esters to inhibit the activity of serine proteases trypsin, thrombin, elastase and urokinase. Potent protease inhibition in micromolar range was displayed by rutin and rutin derivatives esterified with medium and long chain, mono- and polyunsaturated fatty acids (1e–m), followed by phloridzin and esculin esters with medium and long fatty acid chain length (2a–d, 3a–d), while unmodified compounds showed only little or no effect. QSAR study of the compounds tested provided the most significant parameters for individual inhibition activities, i.e. number of hydrogen bond donors for urokinase, molecular volume for thrombin, and solvation energy for elastase. According to the statistical analysis, the action of elastase inhibitors is opposed to those of urokinase and thrombin. Cluster analysis showed two groups of compounds: original polyphenols together with rutin esters with short fatty acid chain length and rutin esters with long fatty acid chain length.

Role of long-chain and very-long-chain polyunsaturated fatty acids in macular degenerations and dystrophies.

Macular degeneration is a progressive, bilateral eye disorder that damages the macula of the human eye. The most common form of macular degeneration is age-related macular degeneration (AMD), which is the leading cause of irreversible blindness in people older than 50 years in developed countries. Autosomal dominant Stargardt disease-3 (STGD3) is an inherited macular dystrophy that has clinical features similar to dry AMD, but occurs at a much earlier age. It is caused by a mutation in the elongation of very-long-chain fatty acids-like 4 (ELOVL4) gene, which is responsible for encoding the elongase enzyme that converts shorter chain fatty acids into C28-C38 very long-chain polyunsaturated fatty acids (VLCPUFAs, total number of carbons ≥24). Diets rich in long-chain polyunsaturated fatty acids (LCPUFAs) have inverse associations with the progression of AMD and STGD3, and a deficiency in retinal LCPUFAs and VLCPUFAs has been detected in AMD retinas and STGD3 animal models. This article systematically summarizes the roles of LCPUFAs and VLCPUFAs in AMD and STGD3, and discusses future research directions.

Anaerobic oxidation of n-alkenes by sulphate-reducing bacteria from the genus Desulfatiferula: n-Ketones as potential metabolites

Two alkene-degrading sulphate-reducing bacteria from the genus Desulfatiferula ( Desulfatiferula olefinivorans strain LM2801 T and Desulfatiferula sp. strain BE2801) were investigated for their 1-alkene metabolism. Their total cellular fatty acids were predominantly C-even when they were grown on C-even 1-alkene (1-hexadecene), whereas a mixture of fatty acids with C-odd or C-even carbon chains predominated when cells were grown on C-odd 1-alkene (1-pentadecene). This is consistent with the fatty acid composition of other sulphate-reducing strains previously reported to grow on n-alkenes. Linear and 3-OH–fatty acids appear to be the main fatty acids produced by the two Desulfatiferula strains. The analysis of their neutral lipids led to identifying several n-alkanols and n-ketones with the same number of carbon atoms as the alkene growth substrate and with functionality located between C-1 and C-5. Growth of strains LM2801 T and BE2801 on (per) deuterated 1-alkenes provided direct evidence of their anaerobic transformation to corresponding 1-alkanols, n-ketones and linear (3-OH–) fatty acids. These results demonstrate that Desulfatiferula strains oxidize a 1-alkene by oxidation of the double bond at C-1, but also at C-2 to C-5 (after eventual isomerization of the double bond) yielding the corresponding C-2 to C-5 n-ketones (via the corresponding n-alkanols). The formation of specific 3-OH–fatty acids by elongation of shorter chain fatty acids was also demonstrated. Based on our observations, pathways for anaerobic 1-alkene metabolism in sulphate-reducing bacteria from the genus Desulfatiferula are proposed. They indicate that n-ketones can constitute new metabolites of the biodegradation of n-alkenes in anaerobic environments.

Light-Induced Conformational Changes in Photosynthetic Reaction Centers: Impact of Detergents and Lipids on the Electronic Structure of the Primary Electron Donor

Light-induced hypsochromic shifts of the Q(y) absorption band of the bacteriochlorophyll dimer (P) from 865 to 850 nm were identified using continuous illumination of dark-adapted reaction centers (RCs) from Rhodobacter capsulatus when dispersed in the most commonly used detergent, the zwitterionic lauryl N-dimethylamine-N-oxide. Such a shift is known to be the consequence of the decreased degree of delocalization of P. A 2-fold acceleration of the recovery kinetics of P(+) was found in RCs that underwent light-induced structural changes compared to those where the P-band position did not change. The light-induced shift was irreversible except in the presence of a secondary electron donor. Prolonged (15 min) illumination resulted in a shift in the position of the P-band even in neutral or negatively charged detergents. In contrast, RCs reconstituted into liposomes made from lipids with different headgroup charges showed light-induced shifts only if shorter fatty acid chains were used. The light-induced conformational changes caused a prominent decrease of the redox potential of P ranging from 120 to 160 mV depending on the detergent compared to the potential of P in dark-adapted reaction centers. The measured light-induced potential decreases were 55 to 85 mV larger than those reported for reaction centers where the P-band position remained at 865 nm. The influence of structural factors, such as the delocalization of the electron hole on P(+), the involvement of Tyr M210, and the hydrophobic mismatch between the thickness of the hydrophobic belt of the detergent micelles or the lipid bilayer and the RC protein, on the spectral features and electron transfer kinetics is discussed.

Mechanistic and Structural Insights into the Regioselectivity of an Acyl-CoA Fatty Acid Desaturase via Directed Molecular Evolution

Membrane-bound fatty acid desaturases and related enzymes play a pivotal role in the biosynthesis of unsaturated and various unusual fatty acids. Structural insights into the remarkable catalytic diversity and wide range of substrate specificities of this class of enzymes remain limited due to the lack of a crystal structure. To investigate the structural basis of the double bond positioning (regioselectivity) of the desaturation reaction in more detail, we relied on a combination of directed evolution in vitro and a powerful yeast complementation assay to screen for Δx regioselectivity. After two selection rounds, variants of the bifunctional Δ12/Δ9-desaturase from the house cricket (Acheta domesticus) exhibited increased Δ9-desaturation activity on shorter chain fatty acids. This change in specificity was the result of as few as three mutations, some of them near the putative active site. Subsequent analysis of individual substitutions revealed an important role of residue Phe-52 in facilitating Δ9-desaturation of shorter chain acyl substrates and allowed for the redesign of the cricket Δ12/Δ9-desaturase into a 16:0-specific Δ9-desaturase. Our results demonstrate that a minimal number of mutations can have a profound impact on the regioselectivity of acyl-CoA fatty acid desaturases and include the first biochemical data supporting the acyl-CoA acyl carrier specificity of a desaturase able to carry out Δ12-desaturation.

Myosin-cross-reactive antigen (MCRA) protein from Bifidobacterium breve is a FAD-dependent fatty acid hydratase which has a function in stress protection

BackgroundThe aim of this study was to determine the catalytic activity and physiological role of myosin-cross-reactive antigen (MCRA) from Bifidobacterium breve NCIMB 702258. MCRA from B. breve NCIMB 702258 was cloned, sequenced and expressed in heterologous hosts (Lactococcus and Corynebacterium) and the recombinant proteins assessed for enzymatic activity against fatty acid substrates.ResultsMCRA catalysed the conversion of palmitoleic, oleic and linoleic acids to the corresponding 10-hydroxy fatty acids, but shorter chain fatty acids were not used as substrates, while the presence of trans-double bonds and double bonds beyond the position C12 abolished hydratase activity. The hydroxy fatty acids produced were not metabolised further. We also found that heterologous Lactococcus and Corynebacterium expressing MCRA accumulated increasing amounts of 10-HOA and 10-HOE in the culture medium. Furthermore, the heterologous cultures exhibited less sensitivity to heat and solvent stresses compared to corresponding controls.ConclusionsMCRA protein in B. breve can be classified as a FAD-containing double bond hydratase, within the carbon-oxygen lyase family, which may be catalysing the first step in conjugated linoleic acid (CLA) production, and this protein has an additional function in bacterial stress protection.

Fatty acid composition of the blubber and dermis of adult male Atlantic walruses (Odobenus rosmarus rosmarus) in Svalbard, and their potential prey

Blubber biopsies were collected from 18 adult male walruses from Svalbard, Norway. The biopsies were taken vertically through the skin and the entire blubber layer down to, but not including, the muscle layer. Fatty acid (FA) compositions of inner blubber, outer blubber and dermis of the walruses and of potential prey organisms were determined. The three layers differed significantly from one another in FA composition. Generally, the inner blubber contained more long-chained monounsaturated, saturated and polyunsaturated FAs, while the outer blubber and dermis contained more short-chained monounsaturated FAs. This stratification is similar to what has been observed in other marine mammal species. However, differences between layers were less pronounced than in most other species, possibly because the extremely thick overlying dermis of walruses provides an insulating shield, which affects the FA composition of the outer blubber. The FA composition of the potential prey organisms was different from that of the blubber of the walruses, although more similar to the inner blubber than to the outer blubber or dermis. FA composition in the inner blubber was not significantly correlated with age (assessed by tusk volume), while the FA composition of the outer blubber and dermis were significantly correlated with age.

Simulated Distillation for Biofuel Analysis

Simulated distillation (SimDis) is a gas chromatographic method and has evolved into an indispensable tool in petroleum industries to determine the distillation behavior of different petroleum products and to ensure fuel quality. In contrast to classic physical distillation, SimDis exhibits a range of advantages that include comparatively very small sample amounts and the possibility of automation, which are of great importance in fields of research and in the development of novel fuels. Within this work we could show that SimDis can also be used to characterize not only boiling behaviors of fossil fuels, but also alternative fuels as different kinds of biodiesel. Analysis of different kinds of biodiesel and biodiesel blends, as presented in our work, shows that shorter chain fatty acid methyl esters, as can be found in coconut oil, can significantly change the distillation characteristic to a more favorable distillation curve, which resembles a fossil diesel fuels boiling behavior. The second part of our work shows that there is a good correlation between data obtained using SimDis and conventional distillation, also in case of biodiesel. SimDis therefore can easily be used to classifiy novel biofuels, for example, also bidodiesel made of algae or novel oilseed, regarding boiling characteristics and quality.

Caveolin-1-dependent and -independent membrane domains

Lipid rafts defined as cholesterol- and sphingomyelin-rich domains have been isolated from different cell types that vary greatly in their lipid profiles. Here, we investigated the contribution of the structural protein caveolin-1 (Cav1) to the overall lipid composition and domain abundance in mouse embryonic fibroblasts (MEFs) from wild-type (WT) or Cav1-deficient (Cav1−/−) animals. Our findings show that Cav1 expression had no effect on free (membrane-associated) cholesterol levels. However, Cav1−/−-deficient cells did have a higher proportion of sphingomyelin, decreased abundance of unsaturated phospholipids, and a trend toward shorter fatty acid chains in phosphatidylcholine. We isolated detergent-resistant membranes (DRMs), nondetergent raft domains (NDR), and cholesterol oxidase (CO)-sensitive domains and assessed the abundance of ordered domains in intact cells using the fluorescent dye Laurdan. Despite differences in phospholipid composition, we found that cholesterol levels in DRMs, NDR, and CO-sensitive domains were similar in both cell types. The data suggest that Cav1 is not required to target cholesterol to lipid rafts and that CO does not specifically oxidize caveolar cholesterol. In contrast, the abundance of ordered domains in adherent cells is reduced in Cav1−/− compared with WT MEFs, suggesting that cell architecture is critical in maintaining Cav1-induced lipid rafts.

Catabolism of flocculosin, an antimicrobial metabolite produced by Pseudozyma flocculosa

Flocculosin is an unusual cellobiose lipid secreted by the yeast-like fungus Pseudozyma flocculosa as part of its biocontrol arsenal against other fungi. Recent observations have suggested that the fungus degrades flocculosin to use it as a nutrient source during periods of food limitation. In this work, we sought to identify the catabolic steps leading to the degradation of flocculosin and its subsequent use by P. flocculosa. To this end, we characterized the catabolism of flocculosin through identification of degradation intermediates in a deprived medium using mass spectrometry. As the pH of the medium increased, the molecule was quickly deacylated and lost its antimicrobial activity thereby explaining conflicting results concerning the antimicrobial activity of this class of glycolipid. Following removal of both acetyl groups and the short fatty acid chain under alkaline conditions, the molecule was quickly and completely metabolized by P. flocculosa. Protein purification of culture filtrates confirmed the presence of degradative enzymes produced by P. flocculosa. These enzymes were found to degrade 3,15-dihydroxy-hexadecyl cellobioside (DHC) but not the acylated molecule, thus confirming the protective role of these groups against catabolism. These results are the first evidence of glycolipid degradation by producing organism and suggest that flocculosin can be recycled by P. flocculosa as a nutrient in addition to protecting its ecological niche.

Use of Biodiesel-Derived Crude Glycerol for Producing Eicosapentaenoic Acid (EPA) by the Fungus Pythium irregulare

Crude glycerol is a major byproduct for the biodiesel industry. Producing value-added products through microbial fermentation on crude glycerol provides opportunities to utilize a large quantity of this byproduct. The objective of this study is to explore the potential of using crude glycerol for producing eicosapentaenoic acid (EPA, 20:5 n-3) by the fungus Pythium irregulare . When P. irregulare was grown in medium containing 30 g/L crude glycerol and 10 g/L yeast extract, EPA yield and productivity reached 90 mg/L and 14.9 mg/L x day, respectively. Adding pure vegetable oils (flaxseed oil and soybean oil) to the culture greatly enhanced the biomass and the EPA production. This enhancement was due to the oil absorption by the fungal cells and elongation of shorter chain fatty acids (e.g., linoleic acid and alpha-linolenic acid) into longer chain fatty acid (e.g., EPA). The major impurities contained in crude glycerol, soap and methanol, were inhibitory to fungal growth. Soap can be precipitated from the liquid medium through pH adjustment, whereas methanol can be evaporated from the medium during autoclaving. The glycerol-derived fungal biomass contained about 15% lipid, 36% protein, and 40% carbohydrate, with 9% ash. In addition to EPA, the fungal biomass was also rich in the essential amino acids lysine, arginine, and leucine, relative to many common feedstuffs. Elemental analysis by inductively coupled plasma showed that aluminum, calcium, copper, iron, magnesium, manganese, phosphorus, potassium, silicon, sodium, sulfur, and zinc were present in the biomass, whereas no heavy metals (such as mercury and lead) were detected. The results show that it is feasible to use crude glycerol for producing fungal biomass that can serve as EPA-fortified food or feed.

Fatty Acid Profile in Milk Fat from Qinghai Plateau Yak at Different Altitudes and Parities

Qinghai Plateau yak are the most important grazing livestock for milk and beef production on the Qinghai-Tibetan plateau because they are adapted to extremes of cold environment and higher elevation and can be grazed throughout the year. Milk samples (n = 47) from Qinghai Plateau yak cows of different parities and milk samples (n = 6) from Qinghai yellow cattle cows were analyzed using gas chromatography-mass spectrophotometry. Differences in fatty acid profiles of Qinghai Plateau yak milk fat from rangelands at 3 different elevations, at 2 parities, and between species were compared. Additionally, fatty acid profiles of forages from different elevations were analyzed. Fatty acid percentages (g/100 g total fatty acids) in milk fat of Qinghai Plateau yak from different rangelands were largely similar, but there were differences (P < 0.05) in individual fatty acids, including conjugated linoleic acid. There were also elevation differences in fatty acid percentages (e.g., cis-9, cis-12 C18:2 and cis-9, cis-12, cis-15 C18:3; g/100 g total fatty acids) of forage plants. Milk from multiparous Qinghai Plateau yak cows showed greater (P < 0.01) percentages of C18:1 and C18:2, total unsaturated fatty acids, total monounsaturated fatty acids, and total polyunsaturated fatty acids and lesser (P < 0.01) percentages of total saturated fatty acids than primiparous counterparts. The cis-9, trans-11 conjugated linoleic acid isomer percentage in milk fat from multiparous cows was greater (P < 0.01) than from primiparous cows. The study results also suggested that short-chained, medium-chained, and saturated fatty acid percentages of milk fat were greater (P < 0.05) for Qinghai Plateau yak compared with those of Qinghai yellow cattle.

The effect of fatty acid surfactants on the uptake of nitric acid to deliquesced NaCl aerosol

Abstract. Surface active organic compounds have been observed in marine boundary layer aerosol. Here, we investigate the effect such surfactants have on the uptake of nitric acid (HNO3), an important removal reaction of nitrogen oxides in the marine boundary layer. The uptake of gaseous HNO3 on deliquesced NaCl aerosol was measured in a flow reactor using HNO3 labelled with the short-lived radioactive isotope 13N. The uptake coefficient γ on pure deliquesced NaCl aerosol was γ=0.5±0.2 at 60% relative humidity and 30 ppb HNO3(g). The uptake coefficient was reduced by a factor of 5–50 when the aerosol was coated with saturated linear fatty acids with carbon chain lengths of 18 and 15 atoms in monolayer quantities. In contrast, neither shorter saturated linear fatty acids with 12 and 9 carbon atoms, nor coatings with the unsaturated oleic acid (C18, cis-double bond) had a detectable effect on the rate of HNO3 uptake. It is concluded that it is the structure of the monolayers formed, which determines their resistance towards HNO3 uptake. Fatty acids (C18 and C15), which form a highly ordered film in the so-called liquid condensed state, represent a significant barrier towards HNO3 uptake, while monolayers of shorter-chain fatty acids (C9, C12) and of the unsaturated oleic acid form a less ordered film in the liquid expanded state and do not hinder the uptake. Similarly, high contents of humic acids in the aerosol, a structurally inhomogeneous, quite water soluble mixture of oxidised high molecular weight organic compounds did not affect HNO3 uptake. As surfactant films on naturally occurring aerosol are expected to be less structured due to their chemical inhomogeneity, it is likely that their inhibitory effect on HNO3 uptake is smaller than that observed here for the C15 and C18 fatty acid monolayers.