REACTIVE INTERMEDIATES IN PHOTOCHEMICAL REACTION OF BIOLOGICALLY RELEVANT PURINES

人体皮肤暴露于持续的紫外线阳光下会导致各种 病理影响，如：晒伤，某些形式的皮肤癌，老化 和免疫系统紊乱。 在分子水平上， 已经解释了光诱导的基础病变的核 acids. 有报道嘌呤光产物在紫外线照射 也可能导致这些有害影响的DNA。 稳定的产品 DNA的嘌呤部分或参与这些反应的活性中间体 光化学过程尚未被详细研究。 在这 我们的主要目标是： 1.继续研究和表征激发态， 参与光化学反应的活性中间体， 嘌呤二核苷、寡核苷酸和 多核苷酸用作DNA模型化合物。 这些将被描述为 从它们的吸收光谱和动力学行为获得的激光 闪光光解技术。 2.嘌呤自由基阳离子与生物活性物质的反应研究 重要分子如氨基酸、糖和氧气使用激光 flash技术 3.确定和表征光销毁中的主要产品 嘌呤核苷、核苷酸和二核苷的作用机制， 将这些产物与它们的短寿命中间体前体相关联。 这些目标将通过进行量子产率测量来实现 并使用光谱分析技术。 4.鉴定参与嘌呤光引发的 与被认为是侧链模型的分子的交联反应 氨基酸链和氨基酸。

The exposure of human skin to continuous UV sunlight can cause a variety of pathological effects such as: sunburn, certain forms of skin cancer, aging and disorders in the immune system. At the molecular level these 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 these photochemical processes have not been studied in detail. In this continuation proposal our main objectives are to: 1. Continue with the study and characterization of excited states and reactive intermediates participating in the photochemical and photodestruction reactions of purine dinucleosides, oligo, and polynucleotides used as DNA model compounds. These will be characterized from their absorption spectra and kinetic behavior obtained with laser flash photolysis techniques. 2. Study the reactions of purine radical cations with biologically important molecules such as amino acids, sugars and with oxygen using laser flash techniques. 3. Identify and characterize the major products in the photodestruction mechanism of purine nucleosides, nucleotides and dinucleosides and correlate these products to their short lived intermediate precursors. These goals will be accomplished by performing quantum yield measurements and using spectroanalytical techniques. 4. Identify the intermediates participating in the purine photoinitiated cross-linking reactions with molecules considered to be models for the side chains of amino acids and with the amino acids.