Thesis Defence: Characterization of Force-dependent DNA Dissociation

Dyuti Raghu, supervised by Dr. Isaac Li, will defend their thesis titled “Characterization of Force-dependent DNA Dissociation” in partial fulfillment of the requirements for the degree of Master of Science in Chemistry.

An abstract for Dyuti Raghu’s thesis is included below.

Defences are open to all members of the campus community as well as the general public. Registration is not required for in-person defences.

Abstract

Mechanical forces are a key component of regulating cellular processes. In biological systems, forces act at a molecular level to modulate interactions, initiate signalling pathways, and drive essential physiological processes. Understanding the role force plays at a cellular level requires tools that can probe these interactions with sensitivity and precision. Tension gauge tethers (TGTs) are DNA duplexes that are used as tension sensors to quantify the forces involved in important cellular processes and are widely used in the field of mechanobiology. Despite their widespread use, certain mechanical properties of TGTs that are required to interpret their signal are undefined. The research presented in this thesis characterizes the force-dependent dissociation of DNA with varying force application geometries and salt concentration. By developing a novel force spectroscopy method, Tether Force Spectroscopy (TFS), for measuring rupture kinetics of irreversible interactions and using this to investigate TGT dissociation, the results show that as the number of shearing base pairs in the TGT sequence increases, the mean rupture force increases as the duplex gets stronger. The results also indicate that increasing salt concentration does not have a visible effect on the rupture kinetics. These results show that TGT rupture is not governed by a single threshold and is a distribution dependent on the loading rate and the force application geometry. This provides more insight into the mechanical properties of TGTs and how these should be taken into context when interpreting their signal. This research refines a widely used measurement tool in mechanobiology, improving its reliability for quantifying forces in cellular environments.