Materials Science and Engineering Seminar Series: Joonil Seog
Dynamic Self-Assembly of Biomacromolecules Probed Using Optical Tweezers
Joint, Department of Materials Science and Engineering and Fischell Department of Bioengineering
University of Maryland
Single molecule studies have made huge impact on our understanding of how biomolecules interact each other. The capability of monitoring one molecule at a time reveals not only the averaged properties from bulk ensemble measurements but also entire distribution of relevant properties with subpopulations and infrequent events. The time evolution of individual molecular behavior also provided the mechanistic insights of the biological events, which cannot be observed in ensemble experiments. Using optical tweezers, unfolding and refolding process of cell adhesion molecule was studied at the single molecule level. The molecule exhibited stepwise multiple transitions in a specific order during unfolding processes, showing mechanical hierarchy in a single protein domain. In the force clamping experiment, three intermediate states were observed when the molecule hops between unfolded state and refolded state. The strong correlation between folding behavior and protein dynamics in allosteric regulation was revealed. The optical tweezers is also applied to understand the unpackaging process of DNA: cationic polymer complex which is critical step in gene delivery. During extension/relaxation cycles, the mechanical decondensation and recondensation of DNA: cationic polymer complex showed significant dependency on the pH level. The relationship between transfection efficiency and mechanical behaviors of the condensed complex is established to provide molecular design parameters for enhanced gene delivery carrier.