Mechanisms for Radiation Damage to DNA: LET Effects

DNA 辐射损伤机制：LET 效应

• 批准号: 8225286
• 负责人: MICHAEL Douglas SEVILLA
• 金额: $ 20.37万
• 依托单位: OAKLAND UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1987
• 资助国家: 美国
• 起止时间: 1987-07-01 至 2013-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8225286
• 关键词: Address; Adenine; Anions; Base Sequence; Biomedical Research; Cations; Charge; Cyclotrons; DNA; DNA Damage; DNA Structure; DNA strand break; Dependence; Deuterium; Development; Electron Spin Resonance Spectroscopy; Electron Transport; Electrons; Event; Free Radicals; Goals; Guanine; Heavy Ions; High-LET Radiation; Ions; Knowledge; Label; Laboratories; Lead; Lesion; Linear Energy Transfer; Location; Magnetic Resonance Spectroscopy; Measures; Methods; Modeling; Molecular; Monitor; Nature; Oxidation-Reduction; Pathway interactions; Process; Purines; Radiation; Radiation Induced DNA Damage; Relative (related person); Research; Role; Running; Sampling; Secondary to; Series; Signal Transduction; Site; Spatial Distribution; Stretching; Structure; Sugar Phosphates; System; Techniques; Testing; Theoretical model; Thymine; Time; Vertebral column; Work; base; density; ds-DNA; insight; irradiation; molecular orbital; protonation; public health relevance; purine; radiation effect; sugar; theories; time use

DESCRIPTION (provided by applicant): The goal of this research is to elucidate fundamental mechanisms of radiation damage to DNA by radiations of varying linear energy transfer (LET). Our comprehensive model for DNA radiation damage that describes events from the initial formation of DNA ion radicals and excited states, to hole and electron transfer, to sugar radical formation and finally to molecular products will be tested at each step to clarify the fundamental processes resulting in DNA radiation damage. These studies, which are performed under conditions that emphasize the direct effect of radiation, will employ magnetic resonance spectroscopies, density functional theory and product analysis techniques as well as gamma and cyclotron heavy ion beam irradiations. There are three aims: The first aim will address several of the major unanswered questions in DNA radiation damage induced by holes. This aim will employ specifically C-8 deuterium labeled defined sequence oligos to exploit a recent breakthrough in our laboratory that allows us to distinguish a hole (cation radical) at a C-8 deuterium labeled purine base (guanine or adenine) from an unlabeled site. We have also found that the C-8 labeling allows the distinction of the guanine and adenine cation radicals from their deprotonated forms. With these developments we will find: a. the base sequence dependence of hole localization, b. the protonation states of guanine and adenine cation radicals at specific sites in dsDNA, c. the extent of base-to- base versus base-to-sugar transfer on hole excitation. Our second aim will identify radicals formed and track structure as a function of LET in ion beam irradiated DNA. We will identify radicals via ESR spectroscopy and ascertain their spatial distribution and clustering as a function of the LET of the radiation along the radiation track. Especially important will be a study of the LET dependence of recently discovered prompt strand break radicals that result from cleavage of the sugar phosphate backbone. The nature of the radical formation and clustering in the track core is pertinent to understanding the formation of the most important lesion in DNA the unrepairable multiply damaged site. Our final aim will employ theoretical calculations to further test and confirm molecular mechanisms proposed in the above studies. Especially significant will be treatment by TD- DFT theory of excited states of base ion radicals which are now implicated in DNA strand breaks and become more significant as the LET of the radiation increases. We believe this effort will allow us to establish new insights into fundamental radiation processes important for biomedical research. PUBLIC HEALTH RELEVANCE: The goal of this research is to develop a comprehensive model of DNA radiation damage by elucidating fundamental mechanisms of damage to DNA by radiations of varying linear energy transfer (LET). Our model for DNA radiation damage that describes events from the initial formation of DNA ion radicals and excited states, to hole and electron transfer, to sugar radical formation and finally to molecular products will be tested at each step to illuminate the fundamental processes resulting in DNA radiation damage. These studies, which are performed under conditions that emphasize the direct effect of radiation, will employ gamma and cyclotron heavy ion beam irradiations, magnetic resonance spectroscopies, density functional theory and product analysis techniques and will address major unanswered questions in DNA radiation damage important to biomedical research.

描述（由申请人提供）：这项研究的目的是通过不同的线性能量转移（LET）的辐射来阐明对DNA辐射损害的基本机制。我们针对DNA辐射损伤的综合模型，描述了从DNA离子自由基和激发态的初始形成到孔和电子转移，到糖自由基形成，最后到分子产物的事件，将在每个步骤中进行测试，以阐明基本过程，从而导致基本过程DNA辐射损伤。这些研究是在强调辐射直接作用的条件下进行的，将采用磁共振光谱，密度功能理论和产品分析技术以及伽马和回旋型重离子束照射。有三个目的：第一个目标将解决孔引起的DNA辐射损害中的几个主要未解决问题。该目标将采用特殊的C-8氘标记为已定义的序列寡素来利用我们实验室的最新突破，使我们能够在C-8氘标记的嘌呤碱基（鸟嘌呤或腺嘌呤）上区分一个孔（阳离子自由基）与未遗漏的部位。我们还发现，C-8标记允许鸟嘌呤和腺嘌呤阳离子自由基与它们的去质子化形式的区别。通过这些发展，我们会发现：孔定位的基本序列依赖性b。 dsdna的特定部位的鸟嘌呤和腺嘌呤阳离子自由基的质子化状态，c。孔激发对基碱与基底转移的范围。我们的第二个目标将识别形成的自由基和轨道结构，这与离子束辐照DNA的函数。我们将通过ESR光谱识别自由基，并确定其空间分布和聚类，这是沿辐射轨道辐射的函数的函数。尤其重要的是，研究最近发现的依赖性的依赖性是由于磷酸糖骨架的裂解而导致的迅速链断裂自由基。轨道核心中自由基形成和聚类的性质与理解DNA中最重要的病变的形成相关。我们的最终目标将采用理论计算来进一步测试并确认上述研究中提出的分子机制。特别重要的是，TD-DFT理论的治疗理论的基础离子自由基的激发态现在与DNA链断裂有关，并且随着辐射的升高的增加而变得更加重要。我们认为，这项努力将使我们能够对生物医学研究重要的基本辐射过程建立新的见解。 公共卫生相关性：这项研究的目的是通过通过不同的线性能量转移（LET）辐射来阐明对DNA损害的基本机制来开发DNA辐射损伤的全面模型。我们的DNA辐射损伤的模型描述了从DNA离子自由基和激发态的初始形成到孔和电子转移，到糖自由基形成，最后到分子产物的事件，将在每个步骤进行测试，以照亮基本过程，从而导致DNA中的基本过程辐射损坏。这些研究是在强调辐射直接效应的条件下进行的，将采用γ和回旋子重离子束辐照，磁共振光谱，密度功能理论和产品分析技术，并将解决对DNA辐射对生物医学重要损害重要的未解决的问题研究。