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Access Type
WSU Access
Date of Award
January 2022
Degree Type
Dissertation
Degree Name
Ph.D.
Department
Physics and Astronomy
First Advisor
Christopher V. Kelly
Abstract
Atomic Force Microscopy (AFM) can be used in single-molecule binding studies to measure parameters such as off-rates and binding distances. However, the interpretation of the obtained bond rupture data is marred by the need to use relatively simple models to describe a potentially very complex unbinding process. The unbinding process is typically not describable by a fixed 1-dimensional barrier height of a single bond but is characterized by a spectrum of barrier heights. Moreover, even if data is filtered to exclude clear multiple rupture events, situations where multiple bonds break simultaneously, thus appearing as single rupture events, further complicate the picture. We present a new data analysis method, using maximum likelihood fit, that considers some of these effects. The method is tested on artificial data generated by Monte Carlo simulations and then applied to measure molecular bond rupture data, using the avidin-biotin system as a model system.
As an AFM can measure the force as small as 20 pN, we would like to use a spherical cantilever to measure the force change in the indentation response inside the triglyceride droplet and lipid droplet that is created from phospholipid and triglycerides. We developed a more quantitative way to determine the effect of added phospholipids on triglycerides that could be complementary to the available techniques. We were able to observe the force required to change the surface area of the droplet while the cantilever indents the droplet. We measured force as a function of indentation depth and interpreted that data to explain the surface tension of the triglycerides and the corresponding lipid droplet. The triglyceride's surface tension decreased significantly to 0.30 mN/m in phospholipid solutions from 1.48 mN/m in water and 2.01 mN/m in buffer solution.
Recommended Citation
Tripathi, Ramesh Chandra, "Application Of Atomic Force Microscopy To Single-Molecule Interactions And The Mechanical Properties Of Lipid Droplets" (2022). Wayne State University Dissertations. 3810.
https://digitalcommons.wayne.edu/oa_dissertations/3810