Mechanic studies of radical-induced DNA damage

DNA由双螺旋中的两条反向平行的多核苷酸链组成，所述双螺旋由通过糖-磷酸单位互连的重复碱基（G、C、A、T）组成。DNA不是稳定的分子。它经常受到细胞内产生的自由基的攻击，这是由于在呼吸中使用氧作为末端电子受体。此外，DNA是电离辐射（X射线，带电粒子），紫外线和各种化学氧化剂的关键目标。自由基和氧化剂与DNA的反应导致许多不同的修饰，这最终决定了其潜在的有害影响。该研究计划涉及DNA损伤形成的化学机制。尽管大多数研究都集中在简单核酸亚基的自由基反应上，但今天很清楚，导致DNA损伤的自由基的命运是由DNA聚合物的局部螺旋结构决定的。当反应性物质附着在DNA上时，它们倾向于与邻近的碱基和糖单元反应，产生新型损伤，在某些情况下涉及两个DNA碱基之间形成共价键。在未来5年中，我的目标是阐明由DNA的四种碱基之一腺嘌呤的活性氮物种引起的DNA损伤的机制。最近，我们开发了一种新的系统，以产生反应物种的腺嘌呤在DNA中，其中一个稳定的前体分子的反应物种是第一次纳入到DNA中，然后它被激活的光或电离辐射。这种方法使我们能够控制DNA中活性物质的性质和初始位置。我们的研究计划将有助于了解DNA损伤的新机制，双链螺旋对这些反应的影响，并可能有助于开发靶向细胞DNA并使其对辐射敏感的药物。

DNA consists of two anti-parallel polynucleotide strands in a double helix, composed of repeating bases (G,C,A,T) interconnected by sugar-phosphate units. DNA is not a stable molecule. It is constantly under attack by free radicals generated within cells as a result of using oxygen as a terminal electron acceptor in respiration. In addition, DNA is a critical target for ionizing radiation (X-rays, charged particles), ultraviolet light, and diverse chemical oxidants. The reaction of free radicals and oxidants with DNA results in a multitude of different modifications, which ultimately determines its potentially deleterious effects. This research proposal deals with the chemical mechanisms of formation of DNA damage. Although the majority of studies have focused on free radical reactions of simple nucleic acid subunits, it is clear today that the fate of radicals leading to DNA damage is determined by the local helical structure of DNA polymers. When reactive species are attached to DNA, they have a tendency to react with neighboring base and sugar units to give novel types of damage involving in certain cases the formation of a covalent bond between two DNA bases. My objective over the next 5 years is to elucidate the mechanisms of DNA damage induced by reactive nitrogen species of one of the four bases of DNA, adenine. Recently, we developed a novel system to generate reactive species of adenine in DNA in which a stable precursor molecule of the reactive species is first incorporated into DNA and then it is activated by light or ionizing radiation. This method allows us to control the nature and initial position of reactive species in DNA. Our research program will help understand novel mechanisms of DNA damage, the influence of the double stranded helix on these reactions, and possibly assist in the development of drugs that target and sensitize cellular DNA to radiation.