The Effect of Ethylenic and Acetylenic Groups on the Properties of Fatty Acid Monolayers

Welles, Harry L.; Zografi, George; Scrimgeour, Charles M.; Gunstone, Frank D.

doi:10.1021/ba-1975-0144.ch010

Cited by 23 publications

(18 citation statements)

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“…It is well-established that monolayers of cis-D9-octadecenoic acid (oleic acid) are more expanded than those from trans-D9-octadecenoic acid (elaidic acid), which in turn are much less condensed than octadecanoic acid (stearic acid) (Welles et al, 1975). This general principle was confirmed by more recent studies on cis-and trans-D13-docosenoic acids (Vollhardt, 2007).…”

Section: Villeneuve and Othersmentioning

confidence: 74%

Conformational folding of mycobacterial methoxy- and ketomycolic acids facilitated by α-methyl trans-cyclopropane groups rather than cis-cyclopropane units

et al. 2013

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Conformational folding of mycobacterial methoxyand ketomycolic acids facilitated by a-methyl trans-cyclopropane groups rather than cis-cyclopropane units The oxygenated long-chain mycolic acids from many mycobacteria are characterized by the presence of mid-chain cyclopropane groups, which can have either cis-configuration or transconfiguration with an adjacent methyl branch. To determine the effect of these functional groups on mycolic acid conformation, surface pressure (p) versus mean molecular area isotherms of methoxy-(MeO-) mycolic acids (MAs) from Mycobacterium kansasii, Mycobacterium tuberculosis (Mtb) Canetti and Mtb H37Ra, and of keto-MAs from Mycobacterium avium-intracellulare complex (MAC) and Mtb H37Ra were recorded and analysed. The MeO-and keto-MAs from Mtb H37Ra, containing scarcely any trans-cyclopropyl groups, apparently took no fully folded 'Wform' conformations. Keto-MA from MAC, whose trans-cyclopropyl group content is nearly 90 %, showed a very solid W-form conformation. MeO-MAs from M. kansasii and Mtb Canetti gave stable W-form conformations at lower temperatures and surface pressures and extended conformations at higher temperatures and surface pressures; their W-form conformation was not as stable as expected from their cis-cyclopropyl group content, probably because they had a wide range of constituent homologues. Energy level calculations of cis-or a-methyl transcyclopropane-containing model molecules and computer simulation studies confirmed the superior folding properties of the latter functional unit. The present results were compared with those of MeO-and keto-MAs from Mtb and from M. bovis Bacillus Calmette-Gué rin (BCG) reported previously. Among the oxygenated MAs, those having higher trans-cyclopropane content tended to take W-form conformations more firmly, implying that the meromycolate proximal intrachain a-methyl trans-cyclopropane groups facilitated MA folding more than cis-cyclopropane groups. INTRODUCTIONMycobacterial mycolic acids (MAs) are characteristic components of the mycobacterial cell envelope, where major proportions of the acids are covalently bonded to the cell wall penta-arabinosyl units (Minnikin, 1982;Draper, 1998;Dmitriev et al., 2000). As shown in the general structure below, MAs are long chain 2-alkyl branched, 3-hydroxy fatty acids, with two intra-chain groups X and Y in the major chain, termed the meromycolate chain:According to the distal intra-chain functional group X, the MAs in this study are classified into three major groups: a nonoxygenated a-, and two oxygenated groups, methoxy-(MeO-) and keto-MAs. According to the proximal intra-chain group Abbreviations: BCG, Mycobacterium bovis Bacillus Calmette-Gué rin; MAC, Mycobacterium avium-intracellulare complex; MA, mycolic acid; Mtb, Mycobacterium tuberculosis.

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Section: Villeneuve and Othersmentioning

confidence: 74%

Conformational folding of mycobacterial methoxy- and ketomycolic acids facilitated by α-methyl trans-cyclopropane groups rather than cis-cyclopropane units

et al. 2013

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“…Correspondingly, unsaturated fatty acids found wide interest in practical applications in the fields of food, pharmaceutical, and cosmetic industries. For understanding the role of unsaturated fatty acids in biological membrane systems, model studies with Lamgmuir monolayers have been performed focused on the effect of cis–trans isomerization, position, and the number of the double bonds. − These studies have shown that the main characteristics of unsaturated carboxylic acid monolayers deviate considerably from those of the corresponding saturated fatty acids. Both the cis - and the trans -isomers of the unsaturated fatty acids unsaturation cause expansion of the monolayer in comparison to the saturated fatty acids at the same alkyl chain length, but the expansion of the cis -isomers is much larger than that of the trans -isomers because the trans double bond changes the configuration of a saturated alkyl chain much less than does a cis double bond.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamics of the Clusterization Process of trans-Isomers of Unsaturated Fatty Acids at the Air/Water Interface

et al. 2012

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In the frameworks of the quantum-chemical semiempirical PM3 method, the thermodynamic parameters of trans-isomers of unsaturated carboxylic acids at the air/water interface were studied. Systems with 18-26 carbon atoms in the alkyl chain and different positions of the double bond are considered. Using quantum-chemical semiempirical PM3 method enthalpy, Gibbs' energy of monomers' formation from the elementary compounds and absolute entropy of trans-unsaturated carboxylic acids are calculated. It has been shown that thermodynamic parameters mentioned above for isomers with the same number of carbon atoms in the hydrocarbon chain but different position of double bond are practically the same within the margin of error. For dimers, trimers, and tetramers of the four trans-unsaturated carboxylic acids, the thermodynamic parameters of clusterization were calculated. It is shown that the position of double bond does not significantly affect the values of thermodynamic parameters of formation and clusterization of carboxylic acids with equal alkyl chain lengths. The only exception is the case that the double bond is in the ω-position (extremely distanced from the carboxylic group). In this case, the number of intermolecular interactions between alkyl chains is changed. Spontaneous clusterization of trans- in the standard conditions is possible for molecules that possess more than 16-17 carbon atoms in the alkyl chain. These threshold values exceed the corresponding values that were calculated previously using the quantum-chemical PM3 method for saturated carboxylic acids (12-13 carbon atoms in the alkyl chain) and are a little bit smaller than the corresponding parameters for cis-unsaturated carboxylic acids (18-19 carbon atoms). These values agree with experimental parameters. Also, the calculated structural parameters of trans-unsaturated carboxylic acids' monolayer for the unit cell with a = 6.98 Å, b = 8.30 Å, and for the molecular tilt angle with 64.95° agree with the experimental parameters.

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“…This lack of a constant value of the complexation constants at high pHs may indicate that sodium (10) ions become the potential determining and that the SBM cannot be applied for the oleic acid droplets at high pH values. The maximum surface charge On was calculated to be-64 l~C/cm 2 for a cross-section area of the carboxylic group of oleic acid molecules in vertically oriented monolayers in contact with water equal to 25 A 2 [21,22]. The extrapolation of pQ shown in Figure 2 yields the intrinsic ionization constant p/~.t = 4.4, almost as was found for the monolayer of carboxylic copolymer studied by Ter-Minassian-Saraga and Thomas [9].…”

Section: Determination Of Ki~ Tmentioning

confidence: 53%

An estimation of the surface ionization constant of oleic acid in aqueous sodium chloride solution

Drzymala

1987

Colloid & Polymer Sci

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Abstract:The zeta potential (r measurements and the site binding theory were utilized for calculations of the parameters of the electrical double layer (edl), ionization, and complexation constants for oleic acid-aqueous sodium chloride solution interface. Assuming that ~ is equal to the diffuse layer potential (~a) of the edl, the charge of the diffuse part of the edl was calculated from the Gouy-Chapman equation. The intrinsic ionizaiton constant was then determined by an extrapolation method to be pK int = 4.4. Subsequently, the surface potential (~o) was calculated, and it was found that ~r changes by 50 mV per pH unit (50 mV/pH) or 42.5 mWpH for 10 -3 and 10 -2 M NaCI, respectively. For further calculations, the integral capacity of the outer zone of the compact part of the edl was F assumed to be K2 = 30 ~ for both ionic strengths. It was established that the intrinsic complexation constant for the binding of Na + ions with the surface of oleic acid is pK~ta = 2.9 _+ 0.5 if the integral capacity of the inner zone of the compact edl (K1) is 80 ~ for 10 -3 M NaC1, but 280 ~ for 10 -2 M NaC1. The use of the same K1 value for both ionic strengths gives a different pK~ for different NaC1 concentrations, and also provides unrealistic surface charge (0o) values greater for 10-3 M NaC1 than for 10-2 M NaC1, at the same pH of the solution.

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The Effect of Ethylenic and Acetylenic Groups on the Properties of Fatty Acid Monolayers

Cited by 23 publications

References 0 publications

Conformational folding of mycobacterial methoxy- and ketomycolic acids facilitated by α-methyl trans-cyclopropane groups rather than cis-cyclopropane units

Conformational folding of mycobacterial methoxy- and ketomycolic acids facilitated by α-methyl trans-cyclopropane groups rather than cis-cyclopropane units

Thermodynamics of the Clusterization Process of trans-Isomers of Unsaturated Fatty Acids at the Air/Water Interface

An estimation of the surface ionization constant of oleic acid in aqueous sodium chloride solution

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