Department of Biophysics and Structural Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine, Peking Union Medical College, 5 Dongdan San Tiao, Beijing 100005, PR China.
Anal Chim Acta. 2013 Sep 10;794:82-9. doi: 10.1016/j.aca.2013.07.060. Epub 2013 Aug 2.
The blood free fatty acids (FFAs), which provide energy to the cell and act as substrates in the synthesis of fats, lipoproteins, liposaccharides, and eicosanoids, involve in a number of important physiological processes. In the present study, matrix-assisted laser desorption/ionization-Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICR MS) with ammonia-treated N-(1-naphthyl) ethylenediamine dihydrochloride (ATNEDC) as a novel MALDI matrix in a negative ion mode was employed to directly quantify serum FFAs. Multiple point internal standard calibration curves between the concentration ratios of individual fatty acids to internal standard (IS, C17:0) versus their corresponding intensity ratios were constructed for C14:0, C16:1, C16:0, C18:0, C18:1, C18:2, C18:3, C20:4, and C22:6, respectively, in their mixture, with correlation coefficients between 0.991 and 0.999 and limits of detection (LODs) between 0.2 and 5.4μM, along with the linear dynamic range of more than two orders of magnitude. The results indicate that the multiple point internal standard calibration could reduce the impact of ion suppression and improve quantification accuracy in the MALDI mode. The quantitative results of nine FFAs from 339 serum samples, including 161 healthy controls, 118 patients with hyperglycemia and 60 patients without hyperglycemia show that FFAs levels in hyperglycemic patient sera are significantly higher than those in healthy controls and patients without hyperglycemia, and elevated FFA levels are also associated with increased levels of fasting blood glucose (FBG) in hyperglycemic patient sera. Serum FFAs were identified on the basis of the observed accurate molecular masses and reliable isotope distributions obtained by MALDI-FTICR MS.
血液游离脂肪酸（FFAs）为细胞提供能量，并作为脂肪、脂蛋白、糖脂和类二十烷酸合成的底物，参与许多重要的生理过程。在本研究中，采用基质辅助激光解吸/电离-傅里叶变换离子回旋共振质谱（MALDI-FTICR MS），使用氨处理的 N-（1-萘基）乙二胺二盐酸盐（ATNEDC）作为新型 MALDI 基质，在负离子模式下直接定量血清 FFAs。在混合物中，构建了 14:0、16:1、16:0、18:0、18:1、18:2、18:3、20:4 和 22:6 等单个脂肪酸与内标（IS，C17:0）的浓度比与相应强度比之间的多点内标校准曲线，相关系数在 0.991 和 0.999 之间，检测限（LOD）在 0.2 和 5.4μM 之间，线性动态范围超过两个数量级。结果表明，多点内标校准可以减少 MALDI 模式下的离子抑制影响，提高定量准确性。对 339 份血清样本（包括 161 名健康对照者、118 名高血糖患者和 60 名非高血糖患者）中 9 种 FFAs 的定量结果表明，高血糖患者血清中的 FFAs 水平明显高于健康对照组和非高血糖患者，且升高的 FFA 水平与高血糖患者血清中空腹血糖（FBG）的升高水平相关。根据 MALDI-FTICR MS 获得的准确分子质量和可靠同位素分布，鉴定了血清 FFAs。
