Position Of Double Bond Research Articles

Study of Trans Fatty Acid Formation in Oil by Heating Using Model Compounds.

The intake of trans fatty acids (TFAs) in foods changes the ratio of low density lipoprotein (LDL) to high density lipoprotein (HDL) cholesterol in blood, which causes cardiovascular disease. TFAs are formed by trans isomerization of unsaturated fatty acids (UFAs). The most recognized formation mechanisms of TFAs are hydrogenation of liquid oil to form partially hydrogenated oil (PHO,) and biohydrogenation of UFAs to form TFA in ruminants. Heating oil also forms TFAs; however, the mechanism of formation, and the TFA isomers formed have not been well investigated. In this study, the trans isomerization mechanism of unsaturated fatty acid formation by heating was examined using the model compounds oleic acid, trioleate, linoleic acid, and trilinoleate for liquid plant oil. The formation of TFAs was found to be suppressed by the addition of an antioxidant and argon gas. Furthermore, the quantity of formed TFAs correlated with the quantity of formed polymer in trioleate heated with air and oxygen. These results suggest that radical reactions form TFAs from UFAs by heating. Furthermore, trans isomerization by heating oleic acid and linoleic acid did not change the original double bond positions. Therefore, the distribution of TFA isomers formed was very simple. In contrast, the mixtures of TFA isomers formed from PHO and ruminant UFAs are complicated because migration of double bonds occurs during hydrogenation and biohydrogenation. These findings suggest that trans isomerization by heating is executed by a completely different mechanism than in hydrogenation and biohydrogenation.

Online Ozonolysis Combined with Ion Mobility-Mass Spectrometry Provides a New Platform for Lipid Isomer Analyses.

One of the most significant challenges in contemporary lipidomics lies in the separation and identification of lipid isomers that differ only in site(s) of unsaturation or geometric configuration of the carbon-carbon double bonds. While analytical separation techniques including ion mobility spectrometry (IMS) and liquid chromatography (LC) can separate isomeric lipids under appropriate conditions, conventional tandem mass spectrometry cannot provide unequivocal identification. To address this challenge, we have implemented ozone-induced dissociation (OzID) in-line with LC, IMS, and high resolution mass spectrometry. Modification of an IMS-capable quadrupole time-of-flight mass spectrometer was undertaken to allow the introduction of ozone into the high-pressure trapping ion funnel region preceding the IMS cell. This enabled the novel LC-OzID-IMS-MS configuration where ozonolysis of ionized lipids occurred rapidly (10 ms) without prior mass-selection. LC-elution time alignment combined with accurate mass and arrival time extraction of ozonolysis products facilitated correlation of precursor and product ions without mass-selection (and associated reductions in duty cycle). Unsaturated lipids across 11 classes were examined using this workflow in both positive and negative ion modalities, and in all cases, the positions of carbon-carbon double bonds were unequivocally assigned based on predictable OzID transitions. Under these conditions, geometric isomers exhibited different IMS arrival time distributions and distinct OzID product ion ratios providing a means for discrimination of cis/trans double bonds in complex lipids. The combination of OzID with multidimensional separations shows significant promise for facile profiling of unsaturation patterns within complex lipidomes including human plasma.

Isolation of the New Antiplasmodial Butanolide, Malleastrumolide A, from Malleastrum sp. (Meliaceae) from Madagascar.

An extract of Malleastrum sp. (Meliaceae) collected in Madagascar by the Madagascar International Cooperative Biodiversity Group was found to have antimalarial activity, with an IC50 value between 2.5 and 5μgml-1 . After purification by liquid-liquid partition, chromatography on a Diaion open column, C18 SPE and C18 reversed phase HPLC, the new butanolide, malleastrumolide A, was isolated. The structure of malleastrumolide A was determined by mass spectrometry, NMR, and ECD. The double bond position was determined by cross-metathesis and mass spectrometry. The compound has antiproliferative activity against the A2780 ovarian cancer cell line with an IC50 value of 17.4μm and antiplasmodial activity against the drug-resistant Dd2 strain of Plasmodium falciparum with an IC50 value of 2.74μm.

N,N,N-Tris(tert-butoxycarbonyl)-l-arginine: five isoforms whose obtainment depends on procedure and scrupulous NMR confirmation of their structures

l-arginine is often covalently linked to vectors for gene or drug delivery as a means of increasing their transfection activity and reducing toxicity. This strategy relies on the protection of basic nitrogen atoms, for example, by employing the tert-butoxycarbonyl group. Our aim in the present work was to prepare the widely described α N, ω N, ω′ N-tris(tert-butyloxycarbonyl)-l-arginine as a single isomer in high yield and with high levels of purity for use in the esterification of dendrimers with several peripheral hydroxyl groups. Following three reported protocols which assured this goal, we observed the unexpected formation of four additional isomers. Using the first procedure, α N, ω N, ω′ N-tris(tert-butyloxycarbonyl)-l-arginine was never obtained. The second procedure delivered the desired compound as a mixture of geometric isomers (E/Z), while the third protocol led to a single isomer in high yield and purity, but with an unreported symmetrical structure. Since Boc protection is transient, this discovery would seem to be of little interest, but preliminary results from an ongoing investigation of the behavior of each of the isomers obtained in the esterification reactions of interest has shown that their reactivity depends on their structure. Although this research is ongoing, here we report a detailed description of these unexpected results, along with an NMR investigation focusing on the double-bond geometry and position which enabled confirmation of the structures.

Fatty Acid Profiling of Tropical Microalgae and Cyanobacteria Strains Isolated From Southwest Indian Ocean Islands

Tropical microalgae and cyanobacteria have natural potential virtues that can be used in a wide range of bioproducts. Indeed, they represent a large biodiversity and benefit from favorable environmental conditions. In this context, 27 isolated marine tropical strains have been studied for their total lipid content, lipid class’s distribution and fatty acids composition. Their potential use for applications in the field of biodiesel and nutritional products has been evaluated by the determination of various parameters estimated in relation to the carbon chain size and the amount and/or position of double bonds in fatty acids (as example, the cetane number, the iodine value, the polyunsaturated/saturated acids ratio, the omega 6 and 3 ratio (n6/n3)). The dinoflagellates Prorocentrum lima and Amphidinium massartii, and the cyanobacteria Leptolyngbya sp. RS01 have good characteristics for biodiesel production whereas Spirulina sp. has a good profile of fatty acids for nutritional application.

Synthesis of novel hybrid steroid dimers by BF3·Et2O-catalyzed aldol condensation of 2-formyl-estradiol diacetate and steroid sapogenins

BF3·Et2O-catalyzed aldol condensation of steroid sapogenins with 2-formyl-estradiol diacetate afforded two novel classes of steroid dimers in which an estrogenic core is attached to the spirostanic side chain of an steroid sapogenin through an exocyclic double bond in position C-23, or through a spiro centre in C-22.

Decarboxylation of Fatty Acids with Triruthenium Dodecacarbonyl: Influence of the Compound Structure and Analysis of the Product Mixtures.

Recently, the decarboxylation of oleic acid (9(Z)-octadecenoic acid) catalyzed by triruthenium dodecacarbonyl, Ru3(CO)12, to give a mixture of heptadecenes with concomitant formation of other hydrocarbons, heptadecane and C17 alkylbenzenes, was reported. The product mixture, consisting of about 77% heptadecene isomers, 18% heptadecane, and slightly >4% C17 alkylbenzenes, possesses acceptable diesel fuel properties. This reaction is now applied to other fatty acids of varying chain length and degree of saturation as well as double-bond configuration and position. Acids beyond oleic acid included in the present study are lauric (dodecanoic), myristic (tetradecanoic), palmitic (hexadecanoic), stearic (octadecanoic), petroselinic (6(Z)-octadecenoic), elaidic (9(E)-octadecenoic), asclepic (11(Z)-octadecenoic), and linoleic (9(Z),12(Z)-octadecadienoic) acids. Regardless of the chain length and degree of unsaturation, a similar product mixture was obtained in all cases with a mixture of alkenes predominating. Monounsaturated fatty acids, however, afforded the alkane with one carbon less than the parent fatty acid as the most prominent component in the mixture. Alkylbenzenes with one carbon atom less than the parent fatty acid were also present in all product mixtures. The number of isomeric alkenes and alkylbenzenes depends on the number of carbons in the chain of the parent fatty acid. With linoleic acid as the starting material, the amount of alkane was reduced significantly with alkenes and alkylaromatics enhanced compared to the monounsaturated fatty acids. Two alkenes, 9(E)-tetradecene and 1-hexadecene, were also studied as starting materials. A similar product mixture was observed but with comparatively minor amount of alkane formed and alkene isomers dominating at almost 90%. The double-bond position and configuration in the starting material do not influence the pattern of alkene isomers in the product mixture. The results underscore the multifunctionality of the Ru3(CO)12 catalyst, which promotes a reaction sequence including decarboxylation, isomerization, desaturation, hydrogenation, and cyclization (aromatization) to give a mixture of hydrocarbons simulating petrodiesel fuels. A reaction pathway is proposed to explain the existence of these products, in which alkenes are dehydrogenated to alkadienes and then, under cyclization, to the observed alkylaromatics. The liberated hydrogen can then saturate alkenes to the corresponding alkane.

Analogues of the 2-carboxyl-6-hydroxyoctahydroindole (CHOI) unit from diverging Pd-catalyzed allylations: Selectivity as a function of the double bond position

Pd-catalyzed allylations of cyclic bis-allylic substrates, carried out either as two separate steps or in a pseudo-domino fashion, can generate 2-carboxyl-hexahydroindoles bearing an unsaturation in different positions. Sequential homologation, and epoxidation or syn-dihydroxylation steps were investigated to access analogues of the bicyclic 2-carboxyl-6-hydroxyoctahydroindole motif of aeruginosins, a family of peptides displaying serine protease inhibitor activity.

Identification and Characterization of Phospholipids with Very Long Chain Fatty Acids in Brewer's Yeast.

Yeast lipids and fatty acids (FA) were analyzed in Saccharomyces pastorianus from seven breweries and in the dietary yeast supplement Pangamin. GC-MS identified more than 30 FA, half of which were very-long chain fatty acids (VLCFA) with hydrocarbon chain lengths of ≥22 C atoms. Positional isomers ω-9 and ω-7 were identified in FA with C18-C28 even-numbered alkyl chains. The most abundant ω-7 isomer was cis-vaccenic acid. The structure of monounsaturated FA was proved by dimethyl disulfide adducts (position of double bonds and cis geometric configuration) and by GC-MS of pyridyl carbinol esters. Ultra-high performance liquid chromatography-tandem mass spectrometry with negative electrospray ionization identified the phospholipids phosphatidylethanolamine, phosphatidylinositol and phosphatidylcholine, with more than 150 molecular species. Wild-type unmutated brewer's yeast strains conventionally used for the manufacture of food supplements were found to contain VLCFA.

Determination of Double Bond Positions in Polyunsaturated Fatty Acids Using the Photochemical Paternò-Büchi Reaction with Acetone and Tandem Mass Spectrometry.

The positions of double bonds along the carbon chain of methylene interrupted polyunsaturated fatty acids are unique identifiers of specific fatty acids derived from biochemical reactions that occur in cells. It is possible to obtain direct structural information as to these double bond positions using tandem mass spectrometry after collisional activation of the carboxylate anions of an acetone adduct at each of the double bond positions formed by the photochemical Paternò-Büchi reaction with acetone. This reaction can be carried out by exposing a small portion of an inline fused silica capillary to UV photons from a mercury vapor lamp as the sample is infused into the electrospray ion source of a mass spectrometer. Collisional activation of [M - H]- yields a series of reverse Paternò-Büchi reaction product ions that essentially are derived from cleavage of the original carbon-carbon double bonds that yield an isopropenyl carboxylate anion corresponding to each double bond location. Aldehydic reverse Paternò-Büchi product ions are much less abundant as the carbon chain length and number of double bonds increase. The use of a mixture of D0/D6-acetone facilitates identification of these double bonds indicating product ions as shown for arachidonic acid. If oxygen is present in the solvent stream undergoing UV photoactivation, ozone cleavage ions are also observed without prior collisional activation. This reaction was used to determine the double bond positions in a 20:3 fatty acid that accumulated in phospholipids of RAW 264.7 cells cultured for 3 days.

Ozone-induced dissociation on a traveling wave high-resolution mass spectrometer for determination of double-bond position in lipids.

The position of C=C within fatty acyl chains affects the biological function of lipids. Ozone-induced dissociation mass spectrometry (OzID-MS) has great potential in determination of lipid double-bond position, but has generally been implemented on low-resolution ion trap mass spectrometers. In addition, most of the OzID-MS experiments carried out so far were focused on the sodiated adducts of lipids; fragmentation of the most commonly observed protonated ions generated in LC/MS-based lipidomics workflow has been less explored. Ozone generated in line from an ozone generator was connected to the trap and transfer gas supply line of a Synapt G2 high-resolution mass spectrometer. Protonated ions of different phosphatidylcholines (PC) were generated by electrospray ionization through direct infusion. Different parameters, including traveling wave height and velocity, trap entrance and DC potential, were adjusted to maximize the OzID efficiency. sn-positional isomers and cis/trans isomers of lipids were compared for their reactivity with ozone. Traveling wave height and velocity were tuned to prolong the encounter time between lipid ions and ozone, and resulted in improved OzID efficiency, as did increasing trapping region DC and entrance potential. Under optimized settings, at least 1000 times enhancement in OzID efficiency was achieved compared to that under default settings for monounsaturated PC standards. Monounsaturated C=C in the sn-2 PC isomer reacted faster with ozone than the sn-1 isomer. Similarly, the C=C in trans PC reacted faster than in cis PC. This is the first implementation of OzID in the trap and transfer region of a traveling wave enabled high-resolution mass spectrometer. The OzID reaction efficiency is significantly improved by slowing down ions in the trap region for their prolonged interaction with ozone. This will facilitate application of high-resolution OzID-MS in lipidomics.

Highly diastereoselective synthesis of novel 2,3,4-trisubstituted chromanes via the reaction of 3-nitro-2-(trihalomethyl)- and 3-nitro-2-phenyl-2H-chromenes with 1-morpholinocyclopentene

The reaction of 3-nitro-2-trifluoro(trichloro)methyl- and 3-nitro-2-phenyl-2H-chromenes with 1-morpholinocyclopentene under the conditions of kinetic or thermodynamic control led to the formation of products due to enamine addition at the C-4 atom of chromene as individual cis,trans- or trans,trans-isomers, differing by the position of double bond in the enamine moiety. Hydrolysis of these compounds in dilute HCl did not cause changes of pyran ring configuration and provided the respective 4-(cyclopentanon-2-yl)chromanes with anti-configuration of hydrogen atoms at the С-4 and С-2′ atoms. Stereochemistry of the obtained compounds was confirmed by X-ray structural analysis.

Morphological analysis of soot agglomerates from biodiesel surrogates in a coflow burner

The effects of unsaturation (including the C–C double bond's position in the alkyl chain) and the ester moiety in the fuel molecule on the morphology of soot particles in a laminar coflow diffusion flame are studied. The effects of the ester moiety are evaluated by comparing an n-decane flame with a biodiesel surrogate flame (composed of 50%/50% molar blend of n-decane and methyl octanoate). The effects of the unsaturation and the position of C–C double bond in the alkyl chain are analysed by comparing 1-decene, 5-decene and n-decane flames. Particles were collected thermophoretically on Transmission Electron Microscopy (TEM) carbon coated copper grids. TEM images are analysed to obtain parameters related to the size of the agglomerates such as radius of gyration, and morphological parameters such as fractal dimension and prefactor of the power-law relationship. The results show that the average primary particle diameter, the size of the agglomerates and the number of primary particles composing the agglomerates increase along the flame length to around two thirds of the flame length and then decrease as a consequence of oxidation becoming dominant over soot nucleation and growth. The fractal dimension of the agglomerates does not change significantly along the different pathlines of the flames. However, effects of the fuel chemical structure are clear. The lowest fractal dimensions are observed for the oxygenated fuel and the highest ones for the unsaturated fuels, with higher fractal dimension when the double bond is located at the edge of the molecule. The same trends are observed for agglomerate sizes: smallest agglomerates are observed for the oxygenated fuel and largest ones for the unsaturated fuels. This suggests that low soot-emitting fuels reduce their size as a consequence of oxidation while keeping their agglomeration skeletal structure.

Natural antioxidant polyphenols on inflammation management: Anti-glycation activity vs metalloproteinases inhibition

ABSTRACTThe diet polyphenols are a secondary metabolites of plants able to act on inflammation process. Their anti-inflammatory activity is articulated through several mechanisms that are related to their antioxidative and radical scavengers properties. Our work is focused on a novel approach to inflammatory disease management, based on anti-glycative and matrix metalloproteinases (MMPs) inhibition effects, as a connected phenomena. To better understand these correlation, polyphenols Structure–Activity Relationship (SAR) studies were also reported. The antioxidant polyphenols inhibit the AGEs at different levels of the glycation process in the following ways: (1) prevention of Amadori adduct oxidation; (2) trapping reactive dycarbonyl compounds; (3) attenuation of receptor for AGEs (RAGE) expression. Moreover, several flavonoids with radical scavenging property showed also MMPs inhibition interact directly with MMPs or indirectly via radical scavengers and AGEs reduction. The essential polyphenols features involved in these mechanisms are C2-C3 double bond and number and position of hydroxyl, glycosyl and O-methyl groups. These factors induce a change in molecular planarity interfering with the hydrogen bond formation, electron delocalization and metal ion chelation. In particular, C2-C3 double bond improve the antioxidant and MMPs inhibition, while the hydroxylation, glycosylation and methylation induce a positive and negative correlation, respectively.

Charge transfer dissociation of phosphocholines: gas-phase ion/ion reactions between helium cations and phospholipid cations.

Phospholipid cations formed by electrospray ionization were subjected to excitation and fragmentation by a beam of 6keV helium cations in a process termed charge transfer dissociation (CTD). The resulting fragmentation pattern in CTD is different from that of conventional collision-induced dissociation, but analogous to that of metastable atom-activated dissociation and electron-induced dissociation. Like collision-induced dissociation, CTD yields product ions indicative of acyl chain lengths and degrees of unsaturation in the fatty acyl moieties but also provides additional structural diagnostic information, such as double bond position. Although CTD has not been tested on a larger lipid sample pool, the extent of structural information obtained demonstrates that CTD is a useful tool for lipid structure characterization, and a potentially useful tool in future lipidomics workflows. CTD is relatively unique in that it can produce a relatively strong series of 2+ product ions with enhanced abundance at the double bond position. The generally low signal-to-noise ratios and spectral complexity of CTD make it less appealing than OzID or other radical-induced methods for the lipids studies here, but improvements in CTD efficiency could make CTD more appealing in the future. Copyright © 2017 John Wiley & Sons, Ltd.

Broad Separation of Isomeric Lipids by High-Resolution Differential Ion Mobility Spectrometry with Tandem Mass Spectrometry.

Maturation of metabolomics has brought a deeper appreciation for the importance of isomeric identity of lipids to their biological role, mirroring that for proteoforms in proteomics. However, full characterization of the lipid isomerism has been thwarted by paucity of rapid and effective analytical tools. A novel approach is ion mobility spectrometry (IMS) and particularly differential or field asymmetric waveform IMS (FAIMS) at high electric fields, which is more orthogonal to mass spectrometry. Here we broadly explore the power of FAIMS to separate lipid isomers, and find a ~75% success rate across the four major types of glycero- and phospho- lipids (sn, chain length, double bond position, and cis/trans). The resolved isomers were identified using standards, and (for the first two types) tandem mass spectrometry. These results demonstrate the general merit of incorporating high-resolution FAIMS into lipidomic analyses. Graphical Abstract ᅟ.

Optimizing the yield of transient mono-dimethyl disulfide adducts for elucidating double bond positions of long chain alkenones

Long chain alkenones (LCAs) are among the most successful biomarkers for paleotemperature reconstructions. However, fundamental questions regarding the biosynthesis and cellular functions of alkenones in haptophyte algae remain poorly understood. Recent discoveries of LCAs with double bond positions and chain lengths that differ from common structures further highlight the importance of continued research into structural variations of this important class of lipid biomarkers to improve LCA applications as temperature proxies. Double bond positions on alkyl chains can be effectively determined by preparing mono-double bond adducts with dimethyl disulfide (DMDS-1), and subsequent gas chromatography–mass spectrometry (GC–MS) analysis. However, previously published procedures for adduct preparation were originally designed for mono-unsaturated fatty acids, and generally produce low product yields when applied to alkenones. Here we demonstrate that the problem originates mainly from DMDS and alkenone overreaction at high temperatures for long time periods, and, secondarily, insufficient amount of iodine catalyst. The overreaction results in DMDS reacting with multiple double bonds, and the possible formation of intermolecular linkages, creating non-volatile products. These products are of little use for elucidating alkenone structures. We demonstrate that by reducing the reaction temperature and time, and by using an optimal amount of iodine, we can maximize the yield of transient DMDS-1 adducts for alkenone structure determination.

CompMS2Miner: An Automatable Metabolite Identification, Visualization, and Data-Sharing R Package for High-Resolution LC-MS Data Sets.

A long-standing challenge of untargeted metabolomic profiling by ultrahigh-performance liquid chromatography-high-resolution mass spectrometry (UHPLC-HRMS) is efficient transition from unknown mass spectral features to confident metabolite annotations. The compMS2Miner (Comprehensive MS2 Miner) package was developed in the R language to facilitate rapid, comprehensive feature annotation using a peak-picker-output and MS2 data files as inputs. The number of MS2 spectra that can be collected during a metabolomic profiling experiment far outweigh the amount of time required for pain-staking manual interpretation; therefore, a degree of software workflow autonomy is required for broad-scale metabolite annotation. CompMS2Miner integrates many useful tools in a single workflow for metabolite annotation and also provides a means to overview the MS2 data with a Web application GUI compMS2Explorer (Comprehensive MS2 Explorer) that also facilitates data-sharing and transparency. The automatable compMS2Miner workflow consists of the following steps: (i) matching unknown MS1 features to precursor MS2 scans, (ii) filtration of spectral noise (dynamic noise filter), (iii) generation of composite mass spectra by multiple similar spectrum signal summation and redundant/contaminant spectra removal, (iv) interpretation of possible fragment ion substructure using an internal database, (v) annotation of unknowns with chemical and spectral databases with prediction of mammalian biotransformation metabolites, wrapper functions for in silico fragmentation software, nearest neighbor chemical similarity scoring, random forest based retention time prediction, text-mining based false positive removal/true positive ranking, chemical taxonomic prediction and differential evolution based global annotation score optimization, and (vi) network graph visualizations, data curation, and sharing are made possible via the compMS2Explorer application. Metabolite identities and comments can also be recorded using an interactive table within compMS2Explorer. The utility of the package is illustrated with a data set of blood serum samples from 7 diet induced obese (DIO) and 7 nonobese (NO) C57BL/6J mice, which were also treated with an antibiotic (streptomycin) to knockdown the gut microbiota. The results of fully autonomous and objective usage of compMS2Miner are presented here. All automatically annotated spectra output by the workflow are provided in the Supporting Information and can alternatively be explored as publically available compMS2Explorer applications for both positive and negative modes ( https://wmbedmands.shinyapps.io/compMS2_mouseSera_POS and https://wmbedmands.shinyapps.io/compMS2_mouseSera_NEG ). The workflow provided rapid annotation of a diversity of endogenous and gut microbially derived metabolites affected by both diet and antibiotic treatment, which conformed to previously published reports. Composite spectra (n = 173) were autonomously matched to entries of the Massbank of North America (MoNA) spectral repository. These experimental and virtual (lipidBlast) spectra corresponded to 29 common endogenous compound classes (e.g., 51 lysophosphatidylcholines spectra) and were then used to calculate the ranking capability of 7 individual scoring metrics. It was found that an average of the 7 individual scoring metrics provided the most effective weighted average ranking ability of 3 for the MoNA matched spectra in spite of potential risk of false positive annotations emerging from automation. Minor structural differences such as relative carbon-carbon double bond positions were found in several cases to affect the correct rank of the MoNA annotated metabolite. The latest release and an example workflow is available in the package vignette ( https://github.com/WMBEdmands/compMS2Miner ) and a version of the published application is available on the shinyapps.io site ( https://wmbedmands.shinyapps.io/compMS2Example ).

Polydatin and its derivatives inhibit fatty acid desaturases in microorganisms

Antioxidant plant polyphenols resveratrol and its glycoside polydatin at 500 μg/L were found to have two distinct effects on yeasts and algae depending on the cell content of polyunsaturated fatty acids (PUFA). In yeasts that do not produce PUFA, resveratrol (0.5 mg/L) increased resistance to biosynthesized ethanol (an important property in winemaking) to 22% EtOH in Saccharomyces cerevisiae and 14% EtOH in Torulaspora delbrückii, the fatty acid content being changed only slightly, whereas in the PUFA‐producing algae Desmodesmus quadricauda and Euglena gracilis both compounds act as inhibitors of Δ4 desaturases blocking the formation of both even‐ and odd‐numbered PUFA having the first double‐bond in position 4. This leads to the biotechnologically desirable accumulation of the health‐beneficial polyunsaturated fatty acids (PUFAs), docosapentaenoic (DPA), and docosahexaenoic acid (DHA).Practical applications: Employing natural stilbene compounds has far‐reaching use in biotechnological applications such as the production of ethanol used for biofuels or production of wine and beer. It allows the production of beer with higher alcohol content, without resorting to the use of consumer‐unacceptable genetically modified yeast. In brewing, when the yeast is often repeatedly reused to ferment fresh wort, higher resistance of yeast in the presence of these compounds can lead to an increase in the number of yeast reuses and thereby reduce economic costs of the brewery needed for preparation of inocula. Using polydatin as inhibitor of Δ4 desaturase in Euglena and Desmodesmus algae blocks the biosynthesis of both even‐ and odd‐numbered PUFAs having a double bond in position 4. This leads to a change in the content of fatty acids and accumulation of biosynthetic precursors, e.g., 22:5n‐3 acid that has more favorable pharmacological effects than docosahexaenoic acid (22:6n‐3)Natural stilbenes such as polydatin and resveratrol have not yet been known as inhibitors of desaturases. We found that they alter the fatty acid composition in microorganisms containing PUFA (algae) by inhibiting Δ4 desaturase and thus blocking the biosynthesis of specific PUFAs. Inhibition of Δ4 desaturase produces oils with a higher proportion of DPA. Moreover, these compounds increase yeast resistance to ethanol.

Protonation of Long Chain Fatty Acids at the Membrane-Water Interface

Long-chain free fatty acids (FA) play an important role in several physiological and pathological processes such as lipid fusion, alteration of membrane permeability and fluidity, as well as regulation of enzyme and protein activity. FA-facilitated membrane proton transport (flip-flop) and FA-dependent proteinaceous proton transport (as in the case of mitochondrial uncoupling proteins) are governed by the difference between FA's pK and the pH in the immediate membrane vicinity1,2. So far, a quantitative understanding of the process is hampered by the shift in the pK value of carboxylic groups that occurs upon moving the FA from the aqueous solutions into the membrane. Its molecular origin is not understood, conceivably because the reported pKa values for the same FA are scattered between 5 and 10.5. Here we systematically obtained the dependence of apparent pKa values on chain length, number and position of double bonds by measuring the zeta-potential of liposomes reconstituted with FA at different pH. pKa ranged from 6.4 to 7.6. Combining the zeta potential measurements with molecular dynamic simulations, we found that pK is determined by the interplay between the energetic costs for burying a charged moiety into the bilayer and the hydrophobic interactions between the free and lipid-bound fatty acid chains.1. Pohl, E. E., Voltchenko, A. M. & Rupprecht, A. Flip-flop of hydroxy fatty acids across the membrane as monitored by proton-sensitive microelectrodes. Biochim.Biophys.Acta 1778, 1292-1297 (2008).2. Rupprecht, A. et al. Role of the transmembrane potential in the membrane proton leak. Biophys.J. 98, 1503-1511 (2010).