| Summary: | 碩士 === 國立陽明大學 === 生醫光電工程研究所 === 94 === A �趁174 double-strand DNA fragment was generated using polymerase chain reaction (PCR) and then cloned into a pYES3/CT/LacZ vector, resulting in ��/Z. Plasmid ��/Z was used as the basis to generate single DNA molecular with digoxigenin on one end and biotin on the other end. The digoxigenin-labeled end is adhered to a small polystyrene particle coated anti-digoxigenin (2�慆 in diameter) in an optical trap, while the biotinylation end is adhered to a big polystyrene particle coated streptavidin (20�慆 in diameter). We made the big particle seating on a cover glass surface which was placed on a PZT stage. Thus, with the smaller particle trapped by optical tweezers, the DNA sample can be stretched (or held loose) by moving the PZT driven translational stage on which the cover glass was mounted. When the dsDNA is stretched tightly, it is supposed there are two elastic forces affect on the small particle at the same time: the DNA and optical tweezers. We have measured the elasticity of DNA as a function of its length. In addition, the value of DNA spring constant we obtained from our experiment was a range from 0.95pN/�慆 to 8.73pN/�慆. We assume KDNA become larger with the increasing number of double-strand DNA connected to both particles. The linear relationship is supposed to exist between KDNA and the increasing number of double-strand DNA and it would lead to know the KDNA of one double-strand DNA.
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