Due to their central role in biochemical processes, fast separation and identification of amino acids (AA) is of importance in many areas of the biomedical field including the diagnosis and monitoring of inborn errors of metabolism and biomarker discovery. Due to the large number of AA together with their isomers and isobars, common methods of AA analysis are tedious and time-consuming because they include a chromatographic separation step requiring pre- or post-column derivatization. Here, we propose a rapid method of separation and identification of sarcosine, a biomarker candidate of prostate cancer, from isomers using differential ion mobility spectrometry (DIMS) interfaced with a tandem mass spectrometer (MS/MS) instrument. Baseline separation of protonated sarcosine from α- and β-alanine isomers can be easily achieved. Identification of DIMS peak is performed using an isomer-specific activation mode where DIMS- and mass-selected ions are irradiated at selected wavenumbers allowing for the specific fragmentation via an infrared multiple photon dissociation (IRMPD) process. Two orthogonal methods to MS/MS are thus added, where the MS/MS(IRMPD) is nothing but an isomer-specific multiple reaction monitoring (MRM) method. The identification relies on the comparison of DIMS-MS/MS(IRMPD) chromatograms recorded at different wavenumbers. Based on the comparison of IR spectra of the three isomers, it is shown that specific depletion of the two protonated α- and β-alanine can be achieved, thus allowing for clear identification of the sarcosine peak. It is also demonstrated that DIMS-MS/MS(IRMPD) spectra in the carboxylic C=O stretching region allow for the resolution of overlapping DIMS peaks.

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由于其在生化过程中的重要作用，氨基酸的快速分离和鉴定在生物医学领域的许多领域都很重要，包括诊断和监测先天性代谢错误和发现生物标志物。由于大量的AA及其同分异构体和等压线，AA分析的常用方法既繁琐又耗时，因为它们包括需要柱前或柱后衍生化的色谱分离步骤。在这里，我们提出了一种使用串联质谱仪（MS / MS）与差分离子迁移谱（DIMS）从异构体中分离和鉴定肌氨酸（一种前列腺癌的生物标志物候选物）的快速方法。可以轻松实现从α-和β-丙氨酸异构体的质子化肌氨酸的基线分离。DIMS峰的鉴定使用异构体特异性活化模式进行，在该模式下，通过红外多光子解离（IRMPD）过程以选定的波数辐照DIMS和质量选择的离子，从而实现特定的片段化。因此，向MS / MS添加了两种正交方法，其中MS / MS（IRMPD）只是异构体特定的多反应监测（MRM）方法。识别依赖于以不同波数记录的DIMS-MS / MS（IRMPD）色谱图的比较。基于三种异构体的红外光谱比较，表明可以实现两种质子化的α-和β-丙氨酸的特定消耗，从而可以清楚地鉴定出肌氨酸峰。

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