Electron Transport in Tissue-Like Material

描述(由申请人提供)：这项研究将提供实验数据，以了解不同种类细胞环境中的电子传输，并能够在能量传输的基本物理水平上，即在假设导致生物变化的化学和生物化学路径的性质之前，对带电粒子轨迹结构模拟进行严格的测试。我们关于辐射造成DNA损伤和细胞突变的生物有效性的大部分知识都是基于对能量沉积初始模式的蒙特卡洛模拟。由于缺乏关于凝聚相相互作用截面的详细信息，蒙特卡罗模拟经常使用从气相数据或从基本上未经检验的理论技术得出的相互作用截面。这些数据中的不确定性可能会对在微观维度上确定能量沉积模式的准确性产生不利影响，例如在DNA中涉及多个受损部位、损伤簇的产生。由于这些代码提供了剂量-反应关系的放射生物学解释所依据的数据，它们是理解辐射照射的生物效应的直接联系，无论这些照射是环境、诊断还是治疗性的。 本工作主要测量凝聚相材料薄膜中快质子输运产生的电子的光谱。光谱，抛射电子能量和发射角度的差异，是在电子传输和它们从材料表面出现后测量的。感兴趣的传输介质包括水、碳氢化合物、寡核苷酸、寡肽和以薄膜和/或冰冻形式存在的DNA。光谱将与蒙特卡罗程序的预测进行比较，蒙特卡罗程序包括气体和/或凝聚相相互作用截面，以测试代码对输入数据细节的敏感性和可靠性。这是对放射生物学中常用的径迹模拟代码中电子传输基本物理的首次直接测试，将为这些代码在放射生物学中的应用提供指导，并增强我们对通过电离辐射导致细胞损伤和突变的能量传输途径不断发展的理解的信心。

DESCRIPTION (provided by applicant): This study will provide experimental data for understanding electron transport in the heterogeneous cellular environment and enable stringent tests of charged-particle track-structure simulation at the level of the underlying physics of energy transport, i.e., prior to assumptions of the nature of chemical and bio-chemical pathways leading to biological alterations. Much of our knowledge of the biological effectiveness of radiation to create DNA damage and cellular mutagenesis is based on Monte Carlo based simulations of the initial patterns of energy deposition. Because of a lack of detailed information on cross sections for interactions in the condensed phase, Monte Carlo simulations often use interaction cross sections derived from gas phase data, or from largely untested theoretical techniques. Uncertainties in these data might have detrimental effects on the accuracy by which patterns of energy deposition can be determined at microscopic dimensions such as are involved in the production of multiply damaged sites, damage clusters, in DNA. Since these codes provide the data upon which radiobiologic interpretations of dose-response relationships are based, they are a direct link to understanding the biological effects of radiation exposures, whether these exposures are environmental, diagnostic, or therapeutic. This work focuses on measurement of the spectra of electrons produced in thin films of condensed phase material by the transit of fast protons. Spectra, differential in ejected electron energy and emission angle, are measured following electron transport and their emergence from the material surface. The transport media of interest include water, hydrocarbons, oligonucleotides, oligopeptides and DNA in thin films and/or frozen as ices. The spectra will be compared to predictions of Monte Carlo codes that incorporate gas and/or condensed phase interaction cross sections to test the sensitivity and reliability of the codes to the details of the input data. This, the first direct test of the fundamental physics of electron transport in track simulation codes commonly used in radiobiology, will provide guidance for the application of these codes in radiobiology and strengthen confidence in our evolving understanding of the energy transport pathways leading to cellular damage and mutagenesis by ionizing radiation.