College of Science

Seminar: Samrat Dutta [Northern Arizona University]

[BIOPHYSICS SEMINAR] Improving health with biophysics: AFM-based single molecule studies of cancer drugs and muscle function

Jan 23, 2018 11:00 AM to Jan 23, 2018 12:00 PM at 8-241

Biomolecules like DNA and proteins exist in a state of dynamic equilibrium among many states, each with a different biological function. In order to determine the function of a biomolecule accurately, it is important that we measure its conformational and mechanical properties one molecule at a time, in contrast to ensemble experiments that average over different states and may therefore miss important biological details. This talk presents atomic force microscopy (AFM) based single molecule studies focused on studying: (1) cancer-drug-DNA interactions; and (2) mechanical properties of the N2A domain of the muscle protein titin.

Our understanding of how the mechanical and conformational properties of a single DNA molecule change due to its interaction with cancer drugs is incomplete. We developed several single molecule methods based on simulations and statistical analyses of AFM images to determine changes in the conformational and mechanical properties of DNA molecules treated with two different cancer drugs, cisplatin and Pt-Acramtu. We found that a GG-cisplatin biadduct induces a 35o - 38o bend angle and a slight softening of the DNA around the bend. Moreover, we found that treatment of DNA with Pt-Acramtu does not change the stiffness of DNA, but it does cause the DNA to aggregate and degrade. Understanding these properties will help us in understanding how DNA repair proteins interact with DNA molecules treated with cancer drugs, ultimately helping in the discovery of more effective cancer drugs. Mechanical properties of immunoglobulin (Ig) domains in titin remain uncharacterized, further limiting our understanding on how force is produced by a muscle. For our studies of titin, we developed an AFM based single molecule force spectroscopy method to determine the mechanical stability of Ig80-Ig81 domains contained in titin’s N2A domain. Our result show that mechanical stability of Ig80-Ig81 domains increases significantly in the presence of calcium, which may contributed to the overall force generated by a muscle. 

Elucidation of these drug-induced DNA conformational and mechanical changes, and chemical signal-induced mechanical changes in titin will contribute in the development of better cancer drugs and therapies for muscle diseases.

10:50 am Refreshments

11:00 am Seminar

Building 8, Room 241