- Synthesis and use of deuterated palmitic acids to decipher the cryptoregiochemistry of a Δ13 desaturation
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(Chemical Equation Presented) The synthesis of two hexadeuterated palmitic acids differing in the position of the diagnostic labels, and their use to decipher the cryptoregiochemistry of a Δ13 desaturation are described. A dithiane and a triple bond functionalities were used to introduce the diagnostic (C 13 or C14) and tagging (C8 and C9) labels, respectively, in the palmitic acid skeleton. Using these probes, the cryptoregiochemistry of the Δ13 desaturation involved in the biosynthesis of Thaumetopoea pityocampa sex pheromone was studied by means of kinetic isotope effect determinations. Transformation of both (Z)-11-hexadecenoic and 11-hexadecynoic acids into (Z, Z)-11,13-hexadecadienoic and (Z)-13-hexadecen-11-ynoic acids, respectively, is initiated by abstraction of the hydrogen atom at the C13 position, followed by the fast elimination of the C14 hydrogen to give the double bond.
- Abad, Jose-Luis,Serra, Montserrat,Camps, Francisco,Fabrias, Gemma
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- Synthesis of Deuterium Labelled (11S,12R)- and (11R,12S)--Palmitic Acids; a Facile Route to Highly Labelled Fatty Acids
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Chiral, highly deuterated palmitic acids are synthesised from 2,2'-bithienyl in three steps by two alkylations and reductive desulfurisation for the introduction of twelve deuterium atoms.The chiral building blocks are obtained from α,β-unsaturated acids by enantiospecific reduction with broken cells of the microorganism Clostridium tyrobutyricum.
- Froessl, Christian,Boland, Wilhelm
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- Mild and Direct Multiple Deuterium-Labeling of Saturated Fatty Acids
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We have established a mild and direct platinum on carbon (Pt/C)-catalyzed multi-deuterium labeling of various saturated fatty acids including bioactive compounds with high deuterium efficiencies in a mixed solvent of isopropyl alcohol and deuterium oxide
- Yamada, Tsuyoshi,Park, Kwihwan,Yasukawa, Naoki,Morita, Kosuke,Monguchi, Yasunari,Sawama, Yoshinari,Sajiki, Hironao
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supporting information
p. 3277 - 3282
(2016/10/21)
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- Deuterium kinetic isotope effects on the dissociation of a protein-fatty acid complex in the gas phase
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Deuterium kinetic isotope effects (KIEs) are reported for the first time for the dissociation of a protein-ligand complex in the gas phase. Temperature-dependent rate constants were measured for the loss of neutral ligand from the deprotonated ions of the 1:1 complex of bovine β-lactoglobulin (Lg) and palmitic acid (PA), (Lg + PA)n- → Lgn- + PA, at the 6- and 7- charge states. At 25 °C, partial or complete deuteration of the acyl chain of PA results in a measurable inverse KIE for both charge states. The magnitude of the KIEs is temperature dependent, and Arrhenius analysis of the rate constants reveals that deuteration of PA results in a decrease in activation energy. In contrast, there is no measurable deuterium KIE for the dissociation of the (Lg + PA) complex in aqueous solution at pH 8. Deuterium KIEs were calculated using conventional transition-state theory with an assumption of a late dissociative transition state (TS), in which the ligand is free of the binding pocket. The vibrational frequencies of deuterated and non-deuterated PA in the gas phase and in various solvents (n-hexane, 1-chlorohexane, acetone, and water) were established computationally. The KIEs calculated from the corresponding differences in zero-point energies account qualitatively for the observation of an inverse KIE but do not account for the magnitude of the KIEs nor their temperature dependence. It is proposed that the dissociation of the (Lg + PA) complex in aqueous solution also proceeds through a late TS in which the acyl chain is extensively hydrated such that there is no significant differential change in the vibrational frequencies along the reaction coordinate and, consequently, no significant KIE.
- Liu, Lan,Michelsen, Klaus,Kitova, Elena N.,Schnier, Paul D.,Brown, Alex,Klassen, John S.
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scheme or table
p. 5931 - 5937
(2012/05/07)
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- Synthesis and use of stereospecifically deuterated analogues of palmitic acid to investigate the stereochemical course of the Δ11 desaturase of the processionary moth
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Thaumetopoea pityocampa pheromone glands contain desaturases that, after several sequential reactions from palmitic acid, catalyze the formation of a unique enyne fatty acid, which is the immediate sex pheromone precursor. In this article, we describe the synthesis of different stereospecifically deuterium-labeled and isotopically tagged palmitic acid probes needed to decipher the stereochemical course of the T. pityocampa Δ11 desaturase. The synthesis of probes has been carried out by a chemoenzymatic route, in which the key step is the kinetic lipase-catalyzed resolution of racemic mixtures of secondary propargyl alcohols. The presence of the acetylenic bond simplifies the absolute configuration determination of the resolved alcohols. Moreover, it allows the introduction of the isotopic tag by deuteration. By use of the probes thus prepared, experimental evidence is presented that the Δ11 desaturase of T. pityocampa transforms palmitic acid into (Z)-11-hexadecenoic acid by removal of the pro-(R)-hydrogen atoms from both C11 and C12.
- Abad, Jose-Luis,Villorbina, Gemma,Fabrias, Gemma,Camps, Francisco
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p. 7108 - 7113
(2007/10/03)
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- Sites of Photolytic Intermolecular Cross-Linking between Fatty Acyl Chains in Phospholipids Carrying a Photoactivable Carbene Precursor
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A number of sn-glycero-3-phosphorylcholines containing the photosensitive ω-undecanoyl group in the sn-2 position and a dideuterated palmitic or stearic acid with both deuteriums on specific carbon atoms along the hydrocarbon chain in the sn-1 position were synthesized.Photolysis of either sonicated vesicles or multilamellar dispersions prepared from these synthetic phospholipids gave extensive intermolecularly cross-linked products.The distribution of the sites of cross-linking was determined by an analysis of cross-linked dimeric fatty esters by using low-resolution electron impact mass spectrometry.The predominance of the benzylic cleavage with a γ-hydrogen abstraction in the mass spectra of these diesters rendered such a quantitation relatively easy.Mass spectral analysis showed that there is a broad distribution in the cross-linking positions along the deuterated sn-1 chain, with the amount of cross-linking increasing toward the hydrophobic core of the bilayer.These results are in agreement with the conformational mobility of the fatty acyl chains and the localization of the photosensitive diazirinophenoxy group in the middle of the bilayer.
- Radhakrishnan, Ramachandran,Costello, Catherine E.,Khorana, H. Gobind
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p. 3990 - 3997
(2007/10/02)
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