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Professor Taekjip Ha, Johns Hopkins University

May 23, 2016 - 4:30pm
Braun Lecture Hall
S.G. Mudd Building
Stanford University

“Revisiting and Repurposing the Double Helix”

About the Seminar: 

DNA is an iconic molecule that forms a double helical structure, providing the basis for genetic inheritance, and its physical properties have been studied for decades. In this talk, I will present evidence that surprising physical properties of DNA such as flexibility and self-association may be important for biological functions [1,2]. In addition, I will present a new application of DNA where mechanical modulations of cell behavior can be studied at the single molecule level using rupturable DNA tethers [3]. We found that cells can change their behavior dramatically in response to just two molecules strongly tugging on them [4].


[1] R. Vafabakhsh and T. Ha, “Extreme bendability of DNA less than 100 base pairs long revealed by single molecule cyclization”, Science 337, 1097-1101 (2012).

[2] T. Ngo, Q. Zhang, R. Zhou, J. G. Yodh and T. Ha, “Asymmetric unwrapping of nucleosomes under tension directed by DNA local flexibility”, Cell 160, 1135-1144 (2015).

[3] X. Wang and T. Ha, “Defining Single Molecular Forces Required to Activate Integrin and Notch Signaling”, Science 340, 991-994 (2013).

[4] M. Roein-Peikar, Q. Xu, X. Wang and T. Ha, “Ultrasensitivity of cell adhesion to the presence of mechanically strong ligands,” Physical Review X (2016).

About the Speaker: 

Dr. Taekjip Ha is a Bloomberg Distinguished Professor of Biophysics and Biophysical Chemistry, Biophysics, and Biomedical Engineering at Johns Hopkins University School of Medicine. He is also an investigator with the Howard Hughes Medical Institute. He uses sophisticated physical techniques to manipulate and visualize the movements of single molecules to understand basic biological processes involving DNA and other molecules.  His study is focused on pushing the limits of single-molecule detection methods to study protein–nucleic acid and protein-protein complexes and the mechanical basis of their interactions and functions – both in vitro and in vivo – that are important for genome maintenance.
Dr. Ha received his undergraduate degree in Physics, from Seoul National University, Seoul, Republic of Korea in 1990.  He earned his Ph.D. In Physics from the University of Berkeley in 1996. After postdoctoral training at Stanford University, he was a Physics professor at University of Illinois at Urbana-Champaign for fifteen years until 2015.
Dr. Ha serves as a member of Editorial Boards for Science, Cell, eLife, PRX, Structure, PCCP, Physical Biology and Cancer Convergence. He is a member of the National Academy of Science and an elected fellow of the American Academy of Arts and Sciences.

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