REACTIVE INTERMEDIATES IN PHOTOCHEMICAL REACTION OF BIOLOGICALLY RELEVANT PURINES

根据美国癌症协会的数据， 的皮肤恶性肿瘤将在美国每年被诊断出来。 这些 以及衰老和免疫系统紊乱是 由于暴露而对基因组DNA进行光氧化修饰 太阳紫外线辐射的影响。 在分子水平上 这些有害效应已经用光诱导的 核酸中的碱基损伤。 有报道说嘌呤 紫外线照射的DNA中的光产物，这也可能导致这些 有害影响。 DNA嘌呤部分的稳定产物或 参与光化学过程的活性中间体 没有被研究在相同的细节，因为是案件的 嘧啶碱基。 在这一延续性建议中，我们的主要目标是 是： 1.分离并表征光销毁中的产物 嘌呤衍生物的作用机制 这些将与他们的 已确定并与产品进行比较的短寿命中间体 在高强度纳秒激光照射期间形成。 2.鉴定嘌呤中的中间体和表征产物 光引发的交联反应， 氨基酸侧链的模型和与氨基酸。 3.研究紫外光产生的活性自由基反应 嘌呤如自由基阳离子和自由基 阴离子与生物分子，并建立其参与程度 光降解机制。 所有这些信息将有助于 了解嘌呤在DNA光化学中的作用。

According to the American Cancer Society, more than 600,000 new cases of skin malignancies will be diagnosed in the U.S. each year. These as well as aging and disorders in the immune system are examples of photooxidatiave modifications to genomic DNA as a result of exposure of living organisms to solar UV radiation. At the molecular level these deleterious effects have been explained in terms of photoinduced base lesions in the nucleic acids. There have been reports of purine photoproducts in UV irradiated DNA which could also lead to these deleterious effects. Stable products of the purine moieties of DNA or reactive intermediates participating in the photochemical processes have not been studied in the same detail as is the case of the pyrimidine bases. In this continuation proposal our main objectives are to: 1. Isolate and characterize the products in the photodestruction mechanism of purine derivatives. These will be correlated to their short lived intermediates already identified and compared to products formed during high intensity nanosecond laser irradiation. 2. Identify intermediates and characterize products in the purine photoinitiated cross-linking reactions with molecules considered to be models for the side chain of amino acids and with amino acids. 3. Study reactions of reactive free radicals produced by the UV photoionization of purines such as the radical cation and the radical anion with biomolecules and to establish their extent of participation in the photodegradation mechanism. All this information will help to understand the role of purines in the DNA photochemistry.