Date of Award

Spring 1-1-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical & Biochemical Engineering

First Advisor

Daniel K. Schwartz

Second Advisor

Theodore W. Randolph

Third Advisor

John F. Carpenter

Fourth Advisor

Jennifer N. Cha

Fifth Advisor

Joel L. Kaar

Abstract

Biopolymers, such as proteins and nucleic acids, are omnipresent in modern applications. The need to control interfacial molecular systems is becoming increasingly important in order to develop more sophisticated biopolymer-based technologies. Non-covalent interactions such as electrostatic, van der Waals, and hydrophobic interactions are integral in interfacial phenomena. These interactions dictate how molecules adsorb, desorb, and diffuse at interfaces. By understanding how these forces affect molecular dynamics, we can better design biopolymer-based technologies. Interfacial adsorption and interaction mechanisms are studied using polarized light microscopy and single-molecule total internal reflection fluorescence microscopy (TIRFM). Polarized light microscopy allows for the detection of birefringence within liquid crystal layers, corresponding to molecular orientation, while TIRFM allows detection of single-molecule adsorption, desorption and diffusion events at an interface. Using these techniques, mechanisms for the formation of surfactant-biopolymer complexes, electrostatically-driven protein adsorption, and protein layer formation are identified. From these results, single stranded DNA-surfactant complexes are found to increase the surfactant area per molecule leading to liquid crystal realignment. Electrostatic repulsion affected elementary adsorption of protein to a charged interface without affecting either elementary desorption or interfacial diffusion. Protein layer formation mechanisms were identified by comparing dynamic signatures and applying new analysis techniques to molecular trajectories. The development of surfactant-protein complexes creates protective effects preventing interfacial protein gelation. The work done in this thesis led to higher-order analysis of molecular trajectories. The new analysis techniques led to the development a new single-molecule micro-rheological technique, providing an unprecedented level of mechanistic interpretation of developing viscoelastic layers.

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