A central theme of this group of proposals is the use of quantifiable mechanical perturbation at the microscopic scale to elicit and study cellular mechano-responses. This requirement necessitates the development of quantitative microscopic force transduction methods to apply external forces at selected cell locations. Further, the magnitude and frequency of the applied force have to precisely controlled. The resultant cellular responses to be monitored non-invasively using high sensitivity fluorescence microscopy with 3-D resolution. We propose to establish a core fluorescence microscope facility housing a two-photon confocal microscope with quantitative micro-manipulation capability to serve this common need. The traditional approach to study mechanotransduction on the microscopic level is the use of gradient optical trap (optical tweezers). Optical tweezers have been used in studies ranging from monitoring the deformability of cellular cytoskeleton to the measurement of force generated by a single molecular motor. Optical force on the order of pico- newtons is generated on micro size particles held at the local point of light. After coupling these particles to the cell membrane surface receptors, mechanical perturbation can be applied at specific locations. Our projects further require generating different models of mechanical deformations of the cytoskeleton. A number of these deformation modes of mechanical deformations of the cytoskeleton. A number of these deformation modes are achieved by applying stress at multiple cellular locations and will require the simultaneous manipulation of multiple particles. We will develop a novel multiple trap optical tweezer system where up to four individual particles can be simultaneously manipulated.
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