| Summary: | 博士 === 國立交通大學 === 光電工程系所 === 95 === Optical tweezers are appropriate for molecular or cell biology research because their properties of non-invasive and non-mechanical contact to biological sample and the trapping force is compatible to lots of biological materials’ forces. In this thesis, we used optical tweezers to study the adhesion between a single Klebsiella pneumoniae type 3 fimbria and collagen IV. Different MrkD adhesin variants on the fimbriae are known to display distinct adherence capability for the bacteria to bind extracellular matrix proteins. For this reason, we measured the adhesive force between different MrkD adhesin variants and collagen IV for the first time. The MrkDv1 adhesin and collagen IV are nearly not adhered. The adhesive force between each of the single fimbria carrying MrkDv2, MrkDv3, and MrkDv4 adhesin variants and collagen IV are 2.03 ± 0.03 pN, 3.79 ± 0.12 pN, and 2.87 ± 0.15 pN, respectively. We also used optical tweezers to measure the adhesive force between integrinαIIbβ3-expressing CHO cells and rhodostomin. The interesting result shows that the adhesive force of wild type and mutant rhodostomin are 4.5 pN and 1,81 pN, respectively.
Since a molecular coated bead is usually used in the optical tweezers experiments. The tiny displacement of the bead in the optical trap needs to be precisely detected. In the previous biological experiments, we only measured the 1-D displacement. However, we realized that the 3-D displacements of the bead should be considered. Therefore, we built a single particle tracking (SPT) system which is capable of high spatial and temporal resolutions. Our SPT system has a spatial resolution of 5.5 nm in transverse direction and 11.5 nm in axial direction. If only 2D tracking of the bead is considered, the tracking range can reach 300 nm 300 nm. If the 3D tracking of the bead is needed, the tracking range would reduce to 200 nm 200 nm 200 nm.
At last, we setup a dual beam optical tweezers system. At least one optical trap can be arbitrarily moved in the field of view. By delicately designing the methodology, the adhesion or extension experiment of biological materials may only need 2D or 1D tracking of the bead. Thus, the tracking range may increase. We sincerely hope that this dual beam optical tweezers with a SPT system can be applied to more adhesion and extension properties studies in the near future.
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