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首页> 外文学位 >Unimolecular dissociation of gas-phase small sulfinyl radical ions upon low energy collision-induced dissociation.
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Unimolecular dissociation of gas-phase small sulfinyl radical ions upon low energy collision-induced dissociation.

机译：低能碰撞诱导的离解时，气相小的亚磺酰基自由基离子的单分子离解。

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摘要

Protein radicals play important roles in biological systems including their involvement in enzyme catalytic sites, aging, neurodegenerative diseases, and oxidative damage to proteins. Understanding the structure and reactivity of protein radicals, give insight into their reaction dynamics and structural modifications. Several solution studies have been used to study protein radicals, but their transient nature present difficulties. To over the limitations of solution phase studies, gas-phase atnmospheric pressure radical reactions in an electrospray ionization plume were implemented to study the unimolecular dissociation of small cysteinyl radical ions. Coupling radical reactions with tandem mass spectrometry allows more structural information to be obtained for these long-lived radical species.;Cysteinyl sulfinyl radical ions are new members of the gas-phase amino acid radical ion family. To explore the effect of small structural changes on the fragmentation behavior, three sulfur containing amino acids were explored (cysteine, homocysteine, and penicillamine). Intact, N-acetylated, O-methylated cysteinyl sulfinyl radical ions were investigated by low-energy collision-induced dissociation. The dominant fragmentation channel for the protonated cysteine sulfinyl radical ions was a radical-directed C&agr;-Cbeta homolytic cleavage, resulting in the formation of glycyl radical ions and loss of CH2SO. Whereas, the major channel for homocysteine and penicillamine sulfinyl radical ions were charge-directed fragmentation. Homocysteine sulfinyl radical ions resulted in a major loss of H2O followed by a consecutive SH loss. Penicillamine sulfinyl radical ions resulted in two complementary fragmentation channels, formation of a glycyl radical and sulfenic acid. Interestingly, N-acetylation significantly changed the major fragmentation pathway. This tells us that location of charge (proton) significantly modulate the competition between radical- and charge-directed fragmentations. Stable isotopic labeling was used to provide insight to the reaction mechanisms and computational calculations were used to provide energetics to the possible mechanisms.
机译：蛋白质自由基在生物系统中起重要作用，包括它们参与酶催化位点，衰老，神经退行性疾病以及对蛋白质的氧化损伤。了解蛋白质自由基的结构和反应性，可以深入了解其反应动力学和结构修饰。几种溶液研究已用于研究蛋白质自由基，但是它们的瞬时性质存在困难。为了解决溶液相研究的局限性，在电喷雾电离羽中进行了气相大气压自由基反应，以研究小半胱氨酸自由基离子的单分子解离。自由基反应与串联质谱联用可为这些长寿命自由基物种提供更多的结构信息。半胱氨酰亚磺酰基自由基离子是气相氨基酸自由基离子家族的新成员。为了探索小的结构变化对碎片行为的影响，研究了三种含硫氨基酸（半胱氨酸，高半胱氨酸和青霉素）。通过低能碰撞诱导的解离研究了完整的N-乙酰化，O-甲基化的半胱氨酰亚磺酰基自由基离子。质子化的半胱氨酸亚磺酰基自由基离子的主要碎裂通道是自由基定向的C＆agr-Cβ均质裂解，导致糖基自由基离子的形成和CH2SO的损失。而高半胱氨酸和青霉胺亚磺酰基自由基离子的主要通道是电荷导向的碎片。同型半胱氨酸亚磺酰基自由基离子导致H2O大量损失，随后连续SH损失。青霉胺亚磺酰基自由基离子产生两个互补的断裂通道，形成了甘氨酰自由基和亚磺酸。有趣的是，N-乙酰化显着改变了主要的碎裂途径。这告诉我们，电荷（质子）的位置显着调节了自由基和电荷导向的碎片之间的竞争。稳定的同位素标记用于提供对反应机理的了解，而计算计算则用于为可能的机理提供能量。

著录项

  • 作者

    Love, Chasity B.;

  • 作者单位

    Purdue University.;

  • 授予单位 Purdue University.;
  • 学科 Chemistry Physical.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 152 p.
  • 总页数 152
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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