Desmosine (Des) and isodesmosine (Isodes), cross-linking amino acids in the biomolecule elastin, may be used as biomarkers for various pathological conditions associated with elastin degradation. The current study presents a novel approach to quantify Des and Isodes using matrix-assisted laser desorption ionization (MALDI)-tandem mass spectrometry (MS²) in a linear ion trap coupled to a vacuum MALDI source. MALDI-MS² analyses of Des and Isodes are performed using stable-isotope-labeled desmosine d₄ (labeled-Des) as an internal standard in different biological fluids, such as urine and serum. The method demonstrated linearity over two orders of magnitude with a detection limit of 0.02 ng/μL in both urine and serum without enrichment prior to mass spectrometry, and relative standard deviation of < 5%. The method is used to evaluate the time-dependent degradation of Des upon UV irradiation (254 nm) and found to be consistent with quantification by ¹H NMR. This is the first characterized MALDI-MS² method for quantification of Des and Isodes and illustrates the potential of MALDI-ion trap MS² for effective quantification of biomolecules. The reported method represents improvement over current liquid chromatography-based methods with respect to analysis time and solvent consumption, while maintaining similar analytical characteristics.

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生物分子弹性蛋白中的交联氨基酸Desmosine（Des）和Isodesmosine（Isodes）可用作与弹性蛋白降解相关的各种病理学状况的生物标志物。当前的研究提出了一种在耦合至真空MALDI源的线性离子阱中使用基质辅助激光解吸电离（MALDI）串联质谱（MS ²）定量Des和Isode的新颖方法。使用稳定同位素标记的desmosine d ₄对Des和Isodes进行MALDI-MS ²分析（标记为Des）作为不同生物体液（例如尿液和血清）中的内标。该方法在两个数量级上表现出线性，在尿液和血清中的检出限均为0.02 ng /μL，质谱分析前未富集，相对标准偏差<5％。该方法用于评估紫外线辐射（254 nm）时Des的时间依赖性降解，发现与¹ H NMR定量结果一致。这是定量分析Des和Isode的第一种特征化MALDI-MS ²方法，它说明了MALDI离子阱MS ²的潜力用于有效定量生物分子。报告的方法在保持相似的分析特性的同时，相对于当前的基于液相色谱的方法，在分析时间和溶剂消耗方面均表现出改进。

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