A tandem MS precursor-ion scan approach to identify variable covalent modification of albumin Cys34: a new tool for studying vascular carbonylation
作者:Giancarlo Aldini、Luca Regazzoni、Marica Orioli、Isabella Rimoldi、Roberto Maffei Facino、Marina Carini
DOI:10.1002/jms.1419
日期:2008.11
We developed a liquid chromatography electrospray ionisation multi-stage mass spectrometry (LC-ESI-MS/MS) approach based on precursor-ion scanning and evaluated it to characterize the covalent modifications of Cys34 human serum albumin (HSA) caused by oxidative stress and reactive carbonyl species (RCS) adduction. HSA was isolated and digested enzymatically to generate a suitable-length peptide (LQQCPF) containing the modified tag residue. The resulting LQQCPF peptides were identified by LC-ESI-MS/MS in precursor-ion scan mode and further characterized in product-ion scan mode. The product ions for precursor-ion scanning were selected by studying the MS/MS fragmentation of a series of LQQCPF derivatives containing Cys34 modified with different α,β-unsaturated aldehydes and di and ketoaldehydes. We used a Boolean logic to enhance the specificity of the method: this reconstitutes a virtual current trace (vCT) showing the peaks in the three precursor-ion scans, marked by the same parent ion. The method was first evaluated to identify and characterize the Cys34 covalent adducts of HSA incubated with 4-hydroxy-hexenal, 4-hydroxy-trans-2-nonenal (HNE) and acrolein (ACR). Then we studied the Cys34 modification of human plasma incubated with mildly oxidized low-density lipoproteins (LDL), and the method easily identified the LQQCPF adducts with HNE and ACR. In other experiments, plasma was oxidized by 2,2'-azobis(2-amidinopropane) HCl (AAPH) or by Fe2+/H2O2. In both conditions, the sulfinic derivative of LQQCPF was identified and characterized, indicating that the method is suitable not only for studying RCS-modified albumin, but also to check the oxidative state of Cys34 as a marker of oxidative damage. Copyright © 2008 John Wiley & Sons, Ltd.
我们开发了一种基于前驱体-离子扫描的液相色谱电喷雾离子化多级质谱(LC-ESI-MS/MS)方法,并对其进行了评估,以确定由氧化应激和活性碳(RCS)加成引起的人血清白蛋白(HSA)Cys34共价修饰的特征。分离 HSA 并进行酶解,生成含有修饰标签残基的合适长度的多肽(LQQCPF)。生成的 LQQCPF 肽在前体离子扫描模式下通过 LC-ESI-MS/MS 进行鉴定,并在产物离子扫描模式下进一步表征。通过研究一系列含有用不同的 α、β-不饱和醛、二醛和酮醛修饰的 Cys34 的 LQQCPF 衍生物的 MS/MS 片段,选择了用于前体-离子扫描的产物离子。我们使用布尔逻辑来提高该方法的特异性:它重建了一个虚拟电流痕量(vCT),显示三个前体离子扫描中的峰值,并以相同的母离子标记。首先对该方法进行了评估,以确定和描述与 4-羟基-己烯醛、4-羟基-反式-2-壬烯醛(HNE)和丙烯醛(ACR)共孵育的 HSA 的 Cys34 共价加合物。然后,我们研究了与轻度氧化的低密度脂蛋白(LDL)共孵育的人体血浆中的 Cys34 修饰,该方法很容易鉴定出 LQQCPF 与 HNE 和 ACR 的加合物。在其他实验中,血浆被 2,2'-偶氮双(2-脒基丙烷)盐酸盐(AAPH)或 Fe2+/H2O2 氧化。在这两种条件下,LQQCPF 的亚硫酸衍生物都得到了鉴定和表征,表明该方法不仅适用于研究 RCS 修饰的白蛋白,也适用于检测作为氧化损伤标志物的 Cys34 的氧化状态。Copyright © 2008 John Wiley & Sons, Ltd. All Rights Reserved.