POLYAMINE-POLYNUCLEOTIDE INTERACTIONS

总体目标是了解DNA 塌缩并形成有序的聚集体， 离子条件 整个过程的目的是了解相对 静电的重要性，场地约束，水结构 调制和稳定的新的DNA螺旋几何形状， 离子发挥其影响的方式。 具体的目标是 1. 发展一个一致的统计热力学和动力学 机制，解释了惊人的恒定性os的大小的环形 杆状DNA颗粒被多胺破坏， 六氨合钴（III），与DNA分子量无关， 通过激光散射和电子显微镜测量。 2. 对附近水域的模型进行计算机模拟 带电或极性的表面，这将测试这个想法的可行性， 离子不仅通过静电或结合特定的 位点，而且还通过它们对DNA附近的水结构的影响 表面。 3. 使用化学、抗体和光谱探针和螺旋- 线圈过渡理论，以测试的想法，冷凝的自然 DNA可能是形成的结果， 非B DNA区域（例如Z或P型）的结合， 随机出现的嘌呤-嘧啶交替序列 残基 4. 发展DNA的高分子统计热力学理论 通过将聚合物-聚合物 考虑到不相容性和离子聚合物膨胀，以及 进行光散射和沉降实验， 画出相图与理论相图比较 预期 简单离子和离子聚合物对DNA的压缩是一种 作为病毒颗粒中DNA包装模型， 染色质，并可能导致更好地了解物理 基因表达和DNA调控的潜在机制 复制的

The overall goal is to understand the mechanisms whereby DNA collapses and forms ordered aggregates in response to changes in ionic conditions. The aim throughout is to understand the relative importance of electrostatics, site binding, water structure modulation, and stabilization of novel DNA helix geometries as ways in which ions exert their influence. Specific aims are to 1. Develop a consistent statistical thermodynamic and kinetic mechanism that explains the striking constancy os size of toroidal and rodlike DNA particles collapsed by polyamines and hexammine cobalt(III), independent of the DNA molecular weight, as measured by laser light scattering and electron microscopy. 2. Perform computer simulations on models of water near charged or polar surfaces that will test the plausibility of the idea that ions act not only electrostatically or by binding to specific sites, but also by their effects on water structure near DNA surfaces. 3. Use chemical, antibody, and spectroscopic probes and helix- coil transition theory to test the idea that condensation of natural DNA may be the result of the formation and subsequent association of regions of non-B DNA (e.g. Z or P form) in randomly occurring sequences of alternating purine-pyrimidine residues. 4. Develop a polymer statistical thermodynamic theory of DNA collapse by anionic polypeptides that takes both polymer-polymer incompatibility and ionic polymer expansion into account, and perform light scattering and sedimentation experiments that will map out a phase diagram to compare with theoretical expectations. Compaction of DNA by simple ions and ionic polymers is of interest as a model for DNA packaging in virus particles and chromatin, and may lead to better understanding of the physical mechanisms underlying regulation of gene expression and DNA replication.