Department of Chemistry, University of Nebraska - Lincoln, 711 Hamilton Hall, Lincoln, NE, 68588-0304, USA.
Nebraska Center for Integrated Biomolecular Communication, University of Nebraska - Lincoln, Lincoln, NE, 68588-0304, USA.
J Am Soc Mass Spectrom. 2019 Oct;30(10):2037-2040. doi: 10.1007/s13361-019-02272-w. Epub 2019 Aug 5.
Estradiol is an estrogenic steroid that can undergo glucuronidation at two different sites, which results in two estradiol glucuronide regioisomers. These isomers can be produced by different enzymes and can have different biological activities before being eliminated from the body. Although there have been previous methods that can distinguish the two isomers, these methods often have long acquisition times or high cost per analysis. In this study, traveling wave ion mobility spectrometry (TWIMS) coupled with mass spectrometry (MS) was employed to separate estradiol glucuronides using alkali metal adduction in positive ion mode, where the sodiated dimer adduct provided adequate separation both in single-component standards and in two-component mixtures. Additionally, in negative ion mode, tandem mass spectrometry (MS/MS) was used to quantitatively determine the relative composition of the two isomers. This was possible due to differences in the energetic requirements for loss of the glucuronic acid, which was characterized by energy-resolved collision-induced dissociation (CID). This work demonstrated that the intensity of the glucuronic acid neutral loss product as compared with the intensity of the intact precursor ion can be used to determine the percentage of each isomer present in a mixture. Overall, TWIMS successfully separated estradiol glucuronide isomers in positive ion mode and MS/MS via CID enables relative quantitation of each isomer in negative ion mode.
雌二醇是一种雌激素类固醇，可在两个不同部位发生葡糖醛酸化，从而产生两种雌二醇葡糖苷酸差向异构体。这些异构体可以由不同的酶产生，在从体内消除之前可能具有不同的生物学活性。尽管以前有一些方法可以区分这两种异构体，但这些方法通常需要较长的采集时间或每次分析的成本较高。在这项研究中，采用 traveling wave ion mobility spectrometry (TWIMS) 结合质谱 (MS)，在正离子模式下使用碱金属加成来分离雌二醇葡糖苷酸，其中钠离子二聚体加合物在单一组分标准品和双组分混合物中均提供了足够的分离度。此外，在负离子模式下，串联质谱 (MS/MS) 用于定量测定两种异构体的相对组成。这是由于失去葡糖醛酸所需的能量要求不同，这是通过能量分辨碰撞诱导解离 (CID) 来表征的。这项工作表明，与完整的前体离子强度相比，葡糖醛酸中性损失产物的强度可用于确定混合物中每种异构体的存在百分比。总体而言，TWIMS 成功地在正离子模式下分离了雌二醇葡糖苷酸异构体，而通过 CID 的 MS/MS 则可在负离子模式下对每种异构体进行相对定量。
