Single Molecule Force Extension Measurement on Semi-Flexible Biopolymers Using Magnetic Tweezers
Polymers are pervasive in modern society and are commonly encountered in a wide-range of industrial processes. Polymer chains exhibit complex dynamical phenomena in solutions undergoing convective transport, and a proper understanding of chain dynamics is key to optimizing process conditions. The molecular structure of a polymer chain ultimately determines the macroscopic mechanical response and overall physical properties of polymer solutions and melts. Therefore, the study of polymer chain dynamics is essential to understanding the relationship between polymer chain structure and function. In this thesis, the elasticity of semi-flexible polymers is characterized using double stranded lambda-phage DNA. Single DNA molecules are studied using magnetic tweezers and an inverted fluorescence microscope. Magnetic forces in the piconewton range are applied to individual DNA molecules, and the relative chain extension due to applied force is directly measured and shown to be between 15% and 75% of the polymer contour length (16.3 µm for lambda-phage DNA). The results obtained from this experiment compare favorably to the analytical formula for DNA elasticity derived by Marko and Siggia and previous experimental data obtained using an optical tweezers assay. In addition, a magnetic tweezers set up has been designed, constructed and validated, and this single molecule assay can be further used to study novel polymeric systems, such as chemically-modified single stranded DNA, a flexible polymer. Overall, the research presented in this thesis provides the groundwork for novel investigation of novel polymeric systems at the single molecule level.
single molecule, force extension, semi-flexible polymers, biopolymers, magnetic tweezers, double stranded DNA, lambda-phage DNA, fluorescence microscopy, polymer
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign