DNA & PROTEIN DNA COMPLEXES

Martin Guthold于1997年12月1日加入该项目， 外部生物学家在他们的研究中使用nanoManipulator。 他还将继续对DNA进行调查。 我们有 启动了DNA和蛋白质-DNA复合物的研究， nanoManipulator和补充生化研究。 现在可以常规地获得空气中DNA的高分辨率图像。 在空气中吸附在云母上的DNA的初始推动实验中，我们 能够在可控物质中破坏DNA 经过适当校准后 悬臂的横向力常数，我们将确定 DNA断裂力 实验来确定摩擦力， 摩擦系数和活化能来移动DNA在 目前正在进行表面处理。 我们已经确定了结合能 的25 bp DNA片段吸附到云母上，用于一组 条件 该片段的吸附自由能为： 确定为约4.2 kT，计算了熵能量损失 约为1 kT，因此，结合焓约为 3.2 kT的 将对不同的缓冲液和 底物条件和不同长度的DNA片段。 我们 正在开发一个理论框架来描述 DNA到底物上。 使用一个简单的模型，我们推导出公式 对于自由能，焓和熵的长度依赖性， 吸附作用 包括上述参数的完整模型 加上摩擦参数和运动的激活能， 表面将在未来发展。

Martin Guthold joined the project December 1, 1997 to work with external biologists using the nanoManipulator in their investigations. He will also be continuing his investigations of DNA. We have initiated an investigation of DNA and protein-DNA complexes using the nanoManipulator and complementary biochemical studies. High-resolution images of DNA in air can now be obtained routinely. In initial pushing experiments of DNA adsorbed on mica in air, we were able to rupture DNA in a controlled matter. After proper calibration of the lateral force constant of the cantilever we will determine the rupture force of DNA. Experiments to determine the frictional force, the friction coefficient and the activation energy to move DNA on the surface are currently pursued. We have determined the binding energy of a 25 bp DNA fragment for adsorption onto mica for one set of conditions. The free energy of adsorption for this fragment was determined to be about 4.2 kT, the entropic energy loss was calculated to be about 1 kT, and the enthalpy of binding was, therefore, about 3.2 kT. Binding experiments will be done for different buffer and substrate conditions and for DNA fragments of different length. We are developing a theoretical framework to describe the adsorption of DNA to a substrate. Using a simple model, we have derived formulas for the length dependence of the free energy, enthalpy and entropy of adsorption. A complete model including the aforementioned parameters plus frictional parameters and the activation energy for motion on the surface will be developed in the future.