Transient Intermediates in Electron and Proton Transfer

电子和质子转移中的瞬态中间体

• 批准号: 0750048
• 负责人: Frantisek Turecek
• 金额: $ 40.62万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-04-01 至 2011-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0750048&HistoricalAwards=false
• 关键词: Transient; Intermediates; Electron; Proton; Transfer

With the support of an award from the Organic and Macromolecular Chemistry Program, Professor Franticek Turecek will address highly reactive molecules, radicals, and cation-radical intermediates that are produced by electron transfer to and deprotonation of cations derived from polar molecules such as peptides, nucleosides, and transition metal complexes. The knowledge gained from the proposed studies will be used to explain the reactivity of transient species relevant to electron-ion and ion-ion recombination processes in biomolecules of current interest and to formulate specific and general mechanisms governing the stability and unimolecular dissociations of a variety of highly reactive and elusive species. The proposed studies of reactive intermediates will employ experimental methods allowing for femtosecond collisional electron transfer in beam experiments, as well as electron capture in isolated ions trapped in electrostatic and magnetic fields. Special model compounds will be synthesized to separate intramolecular interactions by restricting the peptide ion conformational space. Fixed-charge groups will be used to control the energetics of electron attachment and transfer and thus to affect the electronic state(s) that are accessed by ion-electron recombination and collisional electron transfer. Ab initio computational methods will be employed to provide relative, dissociation, and transition state energies to be used for RRKM calculations of unimolecular dissociation and isomerization rate constants. Intellectual meritThe proposed research addresses fundamental and hitherto unresolved questions regarding the dissociations of peptide radicals and cation-radicals. Experiments are proposed that will permit the study of unimolecular dissociations of these transient species on a range of short time scales and under conditions of electron attachment and femtosecond collisional transfer. Electron structure theory calculations are an integral part of the proposed research in both experiment planning and data interpretation.Broader impactsPeptide radicals and cation-radicals have been of considerable interest due to their role as intermediates in mass spectrometric analytical methods for peptide sequencing and detection of protein post-translational modifications. Applications of these methods extend to biology, medicine, and other life sciences, and have been fueled by the availability of commercial instruments for electron capture dissociation and electron transfer dissociation. However, fundamental understanding of the chemistry of transient peptide cation-radicals is essential for the rational use of electron-based methods for peptide and protein sequencing. Studies of ion discharge and immobilization on metal-oxide surfaces have already brought practical results in procedures for the manufacturing of special surfaces for medical implants and selective mass spectrometric detection of phosphopeptides. The proposed research in this area is aimed at gaining insight into the processes leading to biomolecule discharge and immobilization on surfaces.

在有机和高分子化学项目奖项的支持下，Franticek Turecek 教授将研究高反应性分子、自由基和阳离子自由基中间体，这些中间体是通过电子转移到极性分子（如肽、核苷）的阳离子和去质子化而产生的和过渡金属配合物。从拟议研究中获得的知识将用于解释与当前感兴趣的生物分子中电子-离子和离子-离子重组过程相关的瞬态物种的反应性，并制定控制各种物质的稳定性和单分子解离的具体和一般机制。高度反应性和难以捉摸的物种。拟议的反应中间体研究将采用实验方法，允许在束流实验中进行飞秒碰撞电子转移，以及捕获静电和磁场中孤立离子的电子。 将合成特殊的模型化合物，通过限制肽离子构象空间来分离分子内相互作用。固定电荷基团将用于控制电子附着和转移的能量，从而影响通过离子-电子复合和碰撞电子转移获得的电子态。将采用从头计算方法来提供相对、解离和过渡态能量，用于单分子解离和异构化速率常数的 RRKM 计算。 学术价值拟议的研究解决了有关肽自由基和阳离子自由基解离的基本且迄今尚未解决的问题。提出的实验将允许在一系列短时间尺度上以及在电子附着和飞秒碰撞转移的条件下研究这些瞬态物质的单分子解离。电子结构理论计算是实验规划和数据解释中拟议研究的一个组成部分。更广泛的影响肽自由基和阳离子自由基由于它们在肽测序和蛋白质检测的质谱分析方法中作为中间体的作用而引起了相当大的兴趣翻译后修饰。这些方法的应用扩展到生物学、医学和其他生命科学，并且电子捕获解离和电子转移解离的商业仪器的可用性推动了这些方法的应用。然而，对瞬态肽阳离子自由基化学的基本了解对于合理使用基于电子的肽和蛋白质测序方法至关重要。离子放电和金属氧化物表面固定化的研究已经在医疗植入物特殊表面的制造过程和磷酸肽的选择性质谱检测中带来了实际成果。该领域拟议的研究旨在深入了解导致生物分子排出和固定在表面上的过程。