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Spatially resolved force spectroscopy with the atomic force microscope.

机译：使用原子力显微镜的空间分辨力光谱。

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摘要

The atomic force microscope (AFM), a relatively new tool for investigating interaction forces between nanometer-scale objects, can provide fundamental insight into biological structure. This thesis presents advances for measuring and mapping interaction forces with the AFM and applications of these techniques to the study of bilayer-bilayer interactions.;First, I present an experimental approach, called D-D mapping, for producing relative charge density maps of biological surfaces using an AFM. This approach uses isoforce surfaces collected at different salt concentrations to remove topography and isolate electrostatic contributions to the tip-sample interaction force. This approach is quantitative for surface potentials below 25 mV, avoids tip-sample contact which can damage the sample or contaminate the tip, and does not require values of the cantilever spring constant, tip radius or tip charge---values which are particularly difficult to determine. I demonstrate D-D mapping on mechanically roughened mica, stacked bilayers of dipalmitolphosphatidylserine, dipalmitolphosphatidylcholine patches on mica, and bacteriorhopsin membranes on mica.;Second, I present a framework for determining the tip-sample interaction potential from perturbations to the thermally driven motion of the cantilever that arise when local interaction potentials add to the free AFM cantilever potential. I examine the behavior of the free cantilever in air and in water, measure the total and interaction potentials of an AFM cantilever in a low salt aqueous solution, and validate the approach by reconstructing the classical electrical double-layer force law from the force gradients derived from the potentials. I also present three-dimensional representations of the total and interaction potentials as a function of tip-sample separation.;I also present software analysis tools modify, display, and analyze AFM data sets. Such tools were either wholly inadequate or nonexistent when I began my thesis.;Finally, I investigate interaction forces near membrane surfaces. Force curves collected with the bare tip on solid-phase lipid bilayers show complex membrane punch through behaviors. Force curves with a fluid phase bilayer on the tip and substrate show possible fusion events and formation of membrane tethers.
机译：原子力显微镜（AFM）是研究纳米级物体之间相互作用力的一种相对较新的工具，可以提供对生物学结构的基本了解。本文介绍了利用原子力显微镜测量和绘制相互作用力的研究进展，以及这些技术在双层-双层相互作用研究中的应用。首先，我提出了一种称为DD映射的实验方法，该方法可使用以下方法生成生物表面的相对电荷密度图原子力显微镜。该方法使用在不同盐浓度下收集的isoforce表面来消除形貌并隔离静电对尖端样品相互作用力的作用。对于低于25 mV的表面电势，此方法是定量的，避免了针尖与样品的接触会损坏样品或污染针尖，并且不需要悬臂弹簧常数，针尖半径或针尖电荷的值-这些值特别困难确定。我展示了在机械粗糙的云母上的DD映射，云母上的二棕榈糖醇磷脂酰丝氨酸叠层双层，云母上的二棕榈糖醇磷脂酰胆碱贴片以及云母上的细菌视紫红质膜。当局部相互作用电势加到自由的AFM悬臂电势上时，就会出现这种情况。我检查了空气和水中自由悬臂的行为，测量了低盐水溶液中AFM悬臂的总电势和相互作用电势，并通过从得出的力梯度重建经典的双层电势定律验证了该方法从潜力。我还介绍了总电位和相互作用电位的三维​​表示形式，作为尖端样品分离的函数。我还介绍了软件分析工具，用于修改，显示和分析AFM数据集。当我开始论文时，这些工具要么完全不足，要么根本不存在。最后，我研究了膜表面附近的相互作用力。用固相脂质双层上的裸露尖端收集的力曲线显示了复杂的膜穿透行为。在尖端和基底上具有液相双层的力曲线显示可能的融合事件和膜系链的形成。

著录项

  • 作者

    Heinz, William Frederick.;

  • 作者单位

    The Johns Hopkins University.;

  • 授予单位 The Johns Hopkins University.;
  • 学科 Chemistry Biochemistry.;Biophysics General.
  • 学位 Ph.D.
  • 年度 2000
  • 页码 195 p.
  • 总页数 195
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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