Primary and secondary locations of charge sites in angiotensin II (M + 2H)2+ ions formed by electrospray ionization.
Primary and secondary locations of charge sites in angiotensin II (M + 2H)2+ ions formed by electrospray ionization.
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电喷雾电离形成的血管紧张素 II (M 2H)2 离子中电荷位点的主要和次要位置。
DOI：
10.1016/s1044-0305(99)00115-4
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发表时间：
2000
影响因子：
3.2
通讯作者：
Reiter,JA
中科院分区：
文献类型：
--
作者：
Sullards,MC;Reiter,JA
利用高能串联质谱和分子动力学计算确定了人血管紧张素II亚稳分解（M +2 H）2+离子的电荷位置。电荷分离反应提供了关于多电荷离子中电荷位置的关键信息。释放的最可几动能（Tm. p.）使用动能释放分布（KERD）结合MS/MS（MS 2）、MS/MS/MS（MS 3）和MS/MS/MS/MS（MS 4）实验获得这些分解的结果。最丰富的单电荷和双电荷产物离子来自前体离子结构，其中一个质子位于精氨酸（Arg）侧链上，另一个质子位于远端肽骨架羰基氧上。MS 3 KERD实验明确表明，无论是N-末端胺，也不是天冬氨酸（Asp）侧链的质子化位点。在气相中，由于两个电荷位点之间的库仑排斥力降低，较低碱性肽骨架而不是较近端和碱性组氨酸（His）侧链的质子化是有利的。丰度较低的单电荷和双电荷产物离子来自前体离子结构，其中一个质子位于Arg侧链上，另一个位于His侧链上。这是证明在MS 3和MS 4质量分析离子动能谱实验。有趣的是，（b7″+ OH）2+产物离子，如血管紧张素II的（M +2 H）2+离子，被观察到具有至少两种不同的分解结构，其中电荷位点具有主要和次要位置。
High-energy tandem mass spectrometry and molecular dynamics calculations are used to determine the locations of charge in metastably decomposing (M + 2H)2+ions of human angiotensin II. Charge-separation reactions provide critical information regarding charge sites in mutiply charged ions. The most probable kinetic energy released (Tm.p.) from these decompositions are obtained using kinetic energy release distributions (KERDs) in conjunction with MS/MS (MS2), MS/MS/MS (MS3), and MS/MS/MS/MS (MS4) experiments. The most abundant singly and doubly charged product ions arise from precursor ion structures in which one proton is located on the arginine (Arg) side chain and the other proton is located on a distal peptide backbone carbonyl oxygen. The MS3KERD experiments show unequivocally that neither the N-terminal amine nor the aspartic acid (Asp) side chain are sites of protonation. In the gas phase, protonation of the less basic peptide backbone instead of the more proximal and basic histidine (His) side chain is favored as a result of reduced coulomb repulsion between the two charge sites. The singly and doubly charged product ions of lesser abundance arise from precursor ion structures in which one proton is located on the Arg side chain and the other on the His side chain. This is demonstrated in the MS3and MS4mass-analyzed ion kinetic energy spectrometry experiments. Interestingly, (b7″+ OH)2+product ions, like the (M + 2H)2+ions of angiotensin II, are observed to have at least two different decomposing structures in which charge sites have a primary and secondary location.