| A critical issue in the biomechanics of macromolecules in living cells is the effects of mechanical forces. To gain insight into the alterations of these molecules, the effect of viscous drag force on the conformational changes of DNA molecules is examined using a novel shearing apparatus developed in this work. This new testing apparatus successfully allows the controlled straining of a viscous fluid containing fluorescently labeled DNA molecules while visually examining their real-time dynamics in situ. By examining the conformational changes of DNA at different strain rates, a connection between the mechanical parameter (shear strain rate) and the biochemical effect (conformational changes) for the DNA molecules is established.; As a step toward an understanding of biomechanical forces influencing protein transport through the cytoskeleton and the functionality of motor proteins, a complementary set of experiments involving the dynamics of protein transport is conducted. A new type of protein called green fluorescent protein (GFP) is used which allows the examination of specific processes within cells without invasively disrupting the cellular functions. The dynamic transport mechanisms are examined using a baculovirus expression system (BEVS) to produce the necessary recombinant proteins.; In tissue engineering, cells are often placed into a polymer scaffolding for controlled attachment, spreading, and growth. However, the microstructural features of the scaffold can affect cell shape, thus influencing the growth and functionality of the cell. From a mechanics point of view, cell shape is largely controlled by the deformation of the cytoskeleton, especially the actin filament network. Since scaffoldings are often fabricated using polymer fibers, mechanics issues involved in cell attachment, spreading and growth on polymer fibers are important in tissue engineering. To examine the effect of fiber diameter on cell shape change, in this work, a specific device and experimental procedures are developed to secure polymer fibers of different diameters for the culturing of endothelial cells on these fibers.; To examine the cellular and molecular biomechanics issues, it was necessary to design and fabricate new experimental systems. The experimental devices and techniques developed in this work not only have enabled us to perform new experiments, but also can be modified for other biomechanics experiments on macromolecules, living polymer systems, and cells. Further, unlike the traditional mechanics studies with a well established theoretical framework, the thesis work performed here is highly interdisciplinary. The current theoretical frame-work linking mechanics to biochemistry is still in its infancy, thus it is necessary to perform experiments first to understand the underlying mechanisms and the basic processes involved in cellular and molecular biomechanics and bioengineering. (Abstract shortened by UMI.)... |
