Reduction of nonpolar amino acids to amino alcohols to enhance volatility for high-precision isotopic analysis.
Reduction of nonpolar amino acids to amino alcohols to enhance volatility for high-precision isotopic analysis.
复制标题
将非极性氨基酸还原为氨基醇，以增强高精度同位素分析的挥发性。
DOI：
10.1021/ac000604l
复制
发表时间：
2001
影响因子：
7.4
通讯作者：
Brenna,JT
中科院分区：
文献类型：
--
作者：
Zaideh,BI;Saad,NM;Lewis,BA;Brenna,JT
氨基酸在气相色谱-连续流动同位素比值质谱仪(GCC-−-IRMS)之前常规使用含碳基团进行衍生化。衍生物C污染分析物C，因为整个衍生物被燃烧成二氧化碳。提取分析物的同位素比率需要进行校正程序。我们提出了一种将六种非极性氨基酸还原为相应的氨基醇的方法，展示了一种从所得到的强氢键分析物中产生可接受的峰形的GC策略，并对氨基酸及其相应的氨基醇进行了同位素分析，以评估任何可能的同位素分馏。丙氨酸、缬氨酸、亮氨酸、异亮氨酸、蛋氨酸或苯丙氨酸在以I2为电泳剂的四氢呋喃中被还原。用2g分析物进行反应，以允许通过常规元素分析-IRMS进行同位素分析。通过红外光谱、熔点和GC对所有反应进行了定量评价。反应混合物的回收率为60−84%。使用厚的固定相(5μm)毛细管柱实现了六种氨基醇混合物的GC分离，以避免熔融石英毛细管壁上的氢键拖尾。GCC−红外光谱测定氨基醇的重复性平均SD(δ13C)=0.2 5±0.19‰。用与红外光谱联用的元素分析仪测得氨基酸的δ13C与用GCC−红外光谱测得的氨基醇的绝对差值为Δδ13C=0.14‰，无一般趋势。用2毫克的分析物进行反应，得到等量的色谱图。这些数据表明，该还原方法不会引起同位素分馏，可用于连续流动同位素分析，以避免添加污染碳。
Amino acids are routinely derivatized using carbon-containing groups prior to gas chromatography continuous-flow isotope ratio mass spectrometry (GCC−IRMS). Derivative C contaminates analyte C because the entire derivatized compound is combusted to CO2. Correction procedures are required to extract the analyte isotope ratio. We present a method for reduction of six nonpolar amino acids to their corresponding amino alcohols, demonstrate a GC strategy to produce acceptable peak shapes from the resulting strongly H-bonding analytes, and present isotopic analysis for amino acids and their corresponding amino alcohols to evaluate any possible isotopic fractionation. Alanine, valine, leucine, isoleucine, methionine, or phenylalanine was reduced using NaBH4in THF with I2as an electrophile. Reactions were performed with 2 g of analyte to permit isotopic analysis by conventional elemental analysis-IRMS. All reactions were quantitative as assessed by IR spectra, melting points, and GC. Recovery from the reaction mixture was 60−84%. GC separation of a mixture of the six amino alcohols was achieved using a thick stationary-phase (5 μm) capillary column to avoid tailing due to hydrogen bonding to the walls of the fused-silica capillary. The reproducibility of GCC−IRMS determinations of amino alcohols averaged SD(δ13C) = 0.25 ± 0.19‰. The absolute differences between δ13C of amino acids measured by an elemental analyzer coupled to IRMS and amino alcohols measured by GCC−IRMS was Δδ13C = 0.14‰ and showed no general trend. Reactions performed with 2 mg of analyte yielded equivalent chromatograms. These data indicate that the reduction method does not induce isotopic fractionation and can be used for continuous-flow isotopic analysis to avoid addition of contaminating carbon.