Mechanisms for Radiation Damage to DNA: LET Effects

DNA 辐射损伤机制：LET 效应

• 批准号: 7798170
• 负责人: MICHAEL Douglas SEVILLA
• 金额: $ 21万
• 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/7798170
• 关键词: Address; Adenine; Anions; Base Sequence; Biomedical Research; Cations; Charge; Complement component C1s; 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）：本研究的目的是阐明不同线性能量转移 (LET) 辐射对 DNA 造成辐射损伤的基本机制。我们的 DNA 辐射损伤综合模型描述了从 DNA 离子自由基和激发态的最初形成，到空穴和电子转移，到糖自由基形成，最后到分子产物的事件，我们将在每个步骤中进行测试，以阐明导致 DNA 辐射损伤的基本过程。 DNA辐射损伤。这些研究是在强调辐射直接影响的条件下进行的，将采用磁共振波谱、密度泛函理论和产物分析技术以及伽马和回旋加速器重离子束辐照。共有三个目标：第一个目标将解决空穴引起的 DNA 辐射损伤中几个尚未解答的主要问题。这一目标将采用专门的 C-8 氘标记的确定序列寡核苷酸来利用我们实验室最近的突破，使我们能够区分 C-8 氘标记的嘌呤碱基（鸟嘌呤或腺嘌呤）上的空穴（阳离子自由基）与未标记的位点。我们还发现，C-8 标记可以将鸟嘌呤和腺嘌呤阳离子自由基与其去质子化形式区分开来。随着这些进展，我们会发现：空穴定位的碱基序列依赖性，b． dsDNA 中特定位点的鸟嘌呤和腺嘌呤阳离子自由基的质子化状态，c．空穴激发时碱基到碱基与碱基到糖转移的程度。我们的第二个目标是识别形成的自由基并跟踪离子束照射 DNA 中 LET 函数的结构。我们将通过 ESR 光谱识别自由基，并确定它们的空间分布和聚类，作为沿辐射轨迹的辐射 LET 的函数。特别重要的是对最近发现的由磷酸糖主链裂解产生的快速链断裂自由基的 LET 依赖性的研究。轨道核心中自由基形成和聚集的性质与理解 DNA 中最重要的损伤（不可修复的多重损伤位点）的形成有关。我们的最终目标是利用理论计算来进一步测试和确认上述研究中提出的分子机制。特别重要的是通过 TD-DFT 理论对基础离子自由基的激发态进行处理，这些基础离子自由基现在与 DNA 链断裂有关，并且随着辐射 LET 的增加而变得更加重要。我们相信，这项努力将使我们能够对对于生物医学研究很重要的基本辐射过程建立新的见解。 公共健康相关性：本研究的目标是通过阐明不同线性能量转移 (LET) 辐射对 DNA 造成损伤的基本机制，开发 DNA 辐射损伤的综合模型。我们的 DNA 辐射损伤模型描述了从 DNA 离子自由基和激发态的最初形成，到空穴和电子转移，到糖自由基形成，最后到分子产物的事件，我们将在每个步骤中进行测试，以阐明产生 DNA 的基本过程辐射损伤。这些研究是在强调辐射直接影响的条件下进行的，将采用伽马和回旋加速器重离子束辐照、磁共振波谱、密度泛函理论和产品分析技术，并将解决对生物医学重要的 DNA 辐射损伤中尚未解答的主要问题。研究。