Natural Deuterium Distribution in Fatty Acids Isolated from Peanut Seed Oil: A Site‐Specific Study by Quantitative 2H NMR Spectroscopy
Natural Deuterium Distribution in Fatty Acids Isolated from Peanut Seed Oil: A Site‐Specific Study by Quantitative 2H NMR Spectroscopy
复制标题
从花生籽油中分离的脂肪酸中的天然氘分布：通过定量 2H NMR 光谱进行的位点特异性研究
作者：
Jia Duan;I. Billault;F. Mabon;R. Robins
定量2H核磁共振光谱已被用于测量从同一种植物油中提取的长链脂肪酸中自然丰度的氘的分布。选用花生籽油，因其油酸和亚油酸含量适宜。采用酯交换法制备脂肪酸甲酯，并采用改性氧化硅柱层析法分离得到脂肪酸甲酯。为了测定最大位置上氘(D)的自然同位素分馏，对纯化后的油酸甲酯和亚油酸甲酯进行化学裂解，并通过定量2H核磁共振谱测定（D/H）i值。因此有可能证明，在油酸到亚油酸的脱饱和过程中，氘发生了分馏。此外，先前观察到的氘在去饱和位点的分布得到证实，（D/H）i的交替模式也得到证实，这与相关氢原子的起源有关。从脂肪酸生物合成过程中所涉及的酶——合成酶和去饱和酶——所固有的动力学同位素效应的角度讨论了所获得的数据。
Quantitative 2H NMR spectroscopy has been used to measure the distribution of deuterium at natural abundance in long‐chain fatty acids extracted from the same vegetable oil. Peanut seed oil was selected, due to its suitable oleic and linoleic acid content. The methyl esters of the fatty acids were prepared by transesterification and isolated by modified argentation column chromatography on silica. In order to measure the natural isotopic fractionation of deuterium (D) at the maximum number of positions, the purified methyl oleate and methyl linoleate were chemically cleaved and the (D/H)i values determined by quantitative 2H NMR spectroscopy. It was thus possible to demonstrate that fractionation in deuterium occurs during the desaturation of oleate to linoleate. Furthermore, the previously observed distribution of deuterium at the sites of desaturation is confirmed, as is the alternating pattern of (D/H)i, which relates to the origin of the pertinent hydrogen atoms. The data obtained are discussed in terms of the kinetic isotopic effects intrinsic to the enzymes—synthetases and desaturases—involved in the biosynthesis of fatty acids.