Determination of stable isotopic enrichment in individual plasma amino acids by chemical ionization mass spectrometry.
Determination of stable isotopic enrichment in individual plasma amino acids by chemical ionization mass spectrometry.
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通过化学电离质谱法测定个体血浆氨基酸中的稳定同位素富集。
DOI：
10.1021/ac50037a028
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发表时间：
1979
影响因子：
7.4
通讯作者：
D. Bier
中科院分区：
文献类型：
--
作者：
D. Matthews;E. Ben;D. Bier
使用N-乙酰基正丙酯氨基酸衍生物的化学电离选择离子监测-气相色谱-质谱（CI-SIM-GCMS），可以测量单个血浆氨基酸中的同位素富集，而不管标记（1 SN、13 C、18 O、2 H）的选择或分子中的位置。使用1 SN标记的氨基酸的结果表明，CI-SIM-GCMS可以检测0.08at.%由于Schoenheimer和Rittenberg首次报道了在给大鼠喂食10 N-氨后测定氨基酸中的氮-15富集（1），氮-15标记化合物在研究氨基酸代谢途径中发挥了重要作用。然而，关于体内氨基酸转氨率的定量信息仍然不可用。尽管血浆样品中所有氨基酸的15 N富集的总和可以容易地测量，但是没有用于测量生理样品中每个单独氨基酸中的15 N富集（或13 C、15 O或2 H富集）的方便技术。唯一报道人体中每种氨基酸中loN富集的研究是Giordano等人的研究。(2)他们给正常和尿毒症受试者注射13 N-尿素，并测量10 N与血清白蛋白氨基酸的结合。对于每个水解的血清白蛋白样品，这些工作人员使用馏分收集液相色谱法分离氨基酸，使每个氨基酸分别与N2反应，然后使用双入口双收集器同位素比质谱仪测量每个N2样品的10 N富集。对于单个样品，整个过程需要50多个小时的努力。用于分离氨基酸的液相色谱的替代方法是气相色谱。当使用组合的气相色谱-质谱法（GCMS）时，
Using chemical Ionization-selected ion monitoring-gas chromatography-mass spectrometry (CI-SIM-GCMS) of the N-acetyl, n-propyl ester amino acidderivatives, isotopic enrichment can be measured in individual plasma amino acids regardless of choice of label (1SN, 13C, 180, 2H) or position in the molecule. Results using 1SN-Iabeled amino acids show that CI-SIM-GCMS can detect 0.08 at.% excess isotope in plasma amino acids from less than 100/uL of plasma.Since Schoenheimer and Rittenberg first reported the measurement of nitrogen-15 enrichment in amino acids after feeding 10N-ammonia to rats (1), nitrogen-15 labeled com-pounds have played an important role in investigating amino acid metabolic pathways. Yet, quantitative information concerning in vivo amino acid transamination rates is still not available. Although the sum of 15N enrichments of all amino acids in a plasma sample can be measured easily, there is no convenient technique for measuring 15N enrichment (or 13C, lsO, or 2H enrichment for that matter) in each individual amino acid in a physiological sample. The only study to report loN enrichments in each of the amino acids in man was the study by Giordano et al.(2) who administered 13N-ureato normal and uremic subjects and measured theincorporation of l0N into the amino acids of serum albumin. For each hydrolyzed serum albumin sample, these workers separated the amino acids using fraction collecting liquid chromatography, reacted each amino acid separately to N2, and then, measured eachN2 sample for l0N enrichment using a dual-inlet dual-collector isotope ratio mass spectrometer. For a single sample, the entire process requires more than 50 hours effort. An alternative to liquid chromatography for the separation of the amino acids is gas chromatography. When combined gas chromatography-mass spectrometry (GCMS) is used, the