DISTINCTION AMONG ISOMERIC UNSATURATED FATTY ACIDS AS LITHIATED ADDUCTS

异构不饱和脂肪酸与锂加合物的区别

• 批准号: 6665789
• 负责人: FONG-FU HSU
• 金额: $ 15.75万
• 依托单位: WASHINGTON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-08-01 至 2003-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6665789
• 关键词: biological products; biomedical resource; cardiovascular system; female; human subject; human tissue; lipids; male; proteins; spectrometry

We describe here features of tandem mass spectra of dilithiated adduct ions of unsaturated fatty acids obtained by electrospray ionization mass spectrometry with low-energy collisionally activated dissociation on a triple stage quadrupole instrument. These spectra distinguish among isomeric unsaturated fatty acids and permit assignment of double-bond location. Informative fragment ions reflect cleavage of bonds remote from the charge site on the dilithiated carboxylate moiety. The spectra contain radical cations reflecting cleavage of bonds between the first and second and between the second and third carbon atoms in the fatty acid chain. These ions are followed by a closed-shell ion series with members separated by 14 m/z units that reflect cleavage of bonds between the third and fourth and then between subsequent adjacent pairs of carbon atoms. This ion series terminates at the member reflecting cleavage of the carbon-carbon single bond vinylic to the first carbon -carbon do ublebond. Ions reflecting cleavages of bonds distal to the double bond are rarely observed for monounsaturated fatty acids and are not abundant when they occur. For polyunsaturated fatty acids that contain double bonds separated by a single methylene group, ions reflecting cleavage of carbon-carbon single bonds between double bonds are abundant, but ions reflecting cleavages distal to the final double bond are not. Cleavages between double bonds observed in these spectra can be rationalized by a scheme involving a six-membered transition state and subsequent rearrangement of a bis-allylic hydrogen atom to yield a terminally unsaturated charge-carrying fragment and elimination of a neutral alkene. The location of the b-hydroxy-alkene moiety in ricinoleic acid can be demonstrated by similar methods. These observations offer the opportunity for laboratories that have tandem quadrupole instruments but do not have instruments with high energy CAD capabilities to assign double bond location in unsaturated free fatty acids by mass spectrometric methods without derivatization.

我们在这里描述的串联质谱的特点， 通过电喷雾获得的不饱和脂肪酸的加合离子 低能碰撞激活电离质谱 在三级四极杆仪器上解离。 这些光谱 区别异构不饱和脂肪酸， 双键位置的分配。 信息碎片离子反映 远离三硫化二苯并噻吩上电荷位点的键断裂 羧酸酯部分。 光谱中含有自由基阳离子 第一和第二之间以及第二之间的键断裂 和脂肪酸链中的第三个碳原子。 这些离子 随后是一个封闭的壳层离子系列，成员间隔为14 m/z 反映第三和第四键之间的键断裂的单元， 然后在随后的相邻碳原子对之间。 该离子 系列终止于反映分裂的成员， 碳-碳单键乙烯基连接到第一个碳-碳双键 ublebond。 反映双键远端键断裂的离子 对于单不饱和脂肪酸很少观察到键， 当它们发生时， 多不饱和脂肪酸， 含有被单个亚甲基、离子分开的双键 反映了双键之间碳-碳单键的断裂 是丰富的，但离子反映分裂远端的最后双 债券不是。 在这些中观察到的双键之间的断裂 光谱可以合理化的计划，涉及六元 双烯丙基的过渡态和随后的重排 氢原子以产生末端不饱和的带电荷的 片段和消除中性烯烃。 的位置 蓖麻油酸中的β-羟基-烯烃部分可以通过以下方式证明： 类似的方法。 这些观察提供了机会， 拥有串联四极杆仪器但没有 具有高能CAD功能的仪器，可分配双键 位置 在不饱和游离脂肪酸中， 衍生化