Assistant Professor Joonil Seog
Joint appointment with the Fischell Department of Bioengineering
Ph.D., Massachusetts Institute of Technology, 2003
Room 1140 Jeong H. Kim Engineering Building
Phone: (301) 405-1885
Fax: (301) 314-2029
Structure-function relationships of biological molecules using single molecule force spectroscopy; nanomechanics of biopolymers and synthetic macromolecules.
In my lab, we are interested in studying the structure-function relationship of biological molecules at the molecular level using high resolution force spectroscopy. Biological molecules such as proteins, glycoprotein, and polysaccharides are designed such a way to perform their unique function which in turn determines macroscopic tissue level properties. With the development of tools that can measure very small forces, we can directly probe molecular level forces to find out molecular origin of macroscopic behavior. For example, the study of the giant muscle protein titin using atomic force microscopy showed how a single titin molecule provides a muscle with passive elasticity during muscle stretching in its physiological condition. In another example, the intermolecular interaction of the highly charged polysaccharides molecules that exist abundantly in cartilage was directly measured using the same technique. By comparing the data obtained at molecular level with the data obtained from a macroscopic tissue level experiment, it was found out that electrostatic repulsive interactions between these molecules contributes to about half of compressive resistance of the cartilage tissue. These are very exciting moments for scientists since we can now explain macroscopic mechanical behaviors of tissue from molecular viewpoint, obtained from direct force measurement at molecular level. This molecular viewpoint also provides insight about the structure-function relationship of biological molecules as well as the guidance about how to engineer biological materials or synthetic biomaterials to enhance or optimize their performance.
We utilize high resolution force spectroscopy such as atomic force microscopy or optical tweezer to study intermolecular interactions of biological molecules and mechanical properties of single biological molecules. When you unfold a single protein by stretching it, the unfolding force is usually in the range of 10 to 200 picoNewton (pN, 10-12 Newton), depending on pulling rate and when you compress densely packed molecular layer on the surface, the compressive resistance can go up to several nanoNewton (nN, 10-9 Newton) depending on the environment and the nature of the intermolecular interaction. Thanks to the development of high resolution force spectroscopy, these tiny forces can be measured at a great accuracy with high spatial resolution. The force measurement at the single or multimolecular level gives important information about kinetics and thermodynamics as well as the nature of the interaction. This fundamental information is very important to our ability to control the interactions between the molecules, and it will eventually provide a useful insight to improve medical devices and biomaterials for tissue engineering or drug delivery applications by optimizing molecular level interactions. In addition, the information obtained from single molecule experiments will help prepare nanostructural materials with tailored nanomechanical properties to be used as building blocks for nanoscale devices, or to probe cell-biomaterial interaction at a molecular level in well-defined environments.
Hwang, W. et al., Surface Induced Nanofiber Growth by Self-Assembly of a Silk-Elastin-like Protein Polymer. Langmuir 25 (21), 12682-12686 (2009).
Seog, J. et al., Nanomechanics of opposing glycosaminoglycan macromolecules. Journal of Biomechanics 38 (9), 1789-1797 (2005).
Seog, J., Dean, D.M., Frank, E.H., Ortiz, C., & Grodzinsky, A.J., Preparation of end-grafted polyelectrolyte brushes on nanoscale probe tips using an electric field. Macromolecules 37 (3), 1156-1158 (2004).
Dean, D., Seog, J., Ortiz, C., & Grodzinsky, A.J., Molecular-level theoretical model for electrostatic interactions within polyelectrolyte brushes: Applications to charged glycosaminoglycans. Langmuir 19 (13), 5526-5539 (2003).
Seog, J. et al., Direct measurement of glycosaminoglycan intermolecular interactions via high-resolution force spectroscopy. Macromolecules 35 (14), 5601-5615 (2002).
Dean, D., Seog, J., Ortiz, C., & Grodzinsky, A., Modeling of electrostic forces between glycosaminoglycan molecules. Abstracts of Papers of the American Chemical Society 224, U428-U428 (2002).
Seog, J. et al., Modeling and measurement of glycosaminoglycan electrostatic interactions. Abstracts of Papers of the American Chemical Society 221, U344-U345 (2001).
Cho, K., Seog, J., & Ahn, T.O., Morphology and toughening behaviour of diallyl isophthalate resin/polyarylate alloy. Polymer 37 (9), 1541-1549 (1996).
"Unfolding behavior of Rossmann fold integrin I domain measured directly using optical tweezer"; J. Seog, J. Dill, X. Zhang, C. Cecconi, M. Kim, M. Shimaoka, C. Bustamante, and T. Springer. Single Molecule Biophysics Winter Workshop, Aspen, CO. February 2007
"Structure-Function of MAdCAM-1 revealed by single-molecule force spectroscopy"; X. Zhang, J. Seog, and T.A. Springer. Experimental Biology, San Francisco, CA. April 2006
"Effect of solution conditions on nanoscale interactions between opposing glycosaminoglycan brushes"; J. Seog, D. Dean, S. Wong-Palms, A. Plaas, A. Grodzinsky, C. Ortiz. The Annual March Meeting of American Physical Society in Austin, TX. March 2003
"Measurement of GAG-GAG nano-electromechanical interactions via high resolution force spectroscopy"; J. Seog, E. Frank, D. Dean, S. Wong-Palms, A. Plaas, A. Grodzinsky, C. Ortiz. The Annual March Meeting of the American Physical Society in Indianapolis, IN. March 2002
"Measurement of GAG-GAG nano-electromechanical interaction using high resolution force spectroscopy"; J. Seog, E. Frank, D. Dean, A. Plaas, S. Wong-Palms, A. Grodzinsky, and C. Ortiz. 48th Annual Meeting of the Orthopedic Research Society in Dallas, TX. February 2002
"Modeling and measurement of glycosaminoglycan electrostatic interactions"; J. Seog, D. Dean, A. Plaas, S. Wong-Palms, A. Grodzinsky, and C. Ortiz. 221st American Chemical Society National Meeting in San Diego, CA. April 2001
"Cartilage molecular mechanics: detection of GAG electrostatic interactions by high-resolution force spectroscopy"; J. Seog, D. Dean, A. Plaas, S. Wong-Palms, I. Lee, P. Laibinis, A. Grodzinsky, and C. Ortiz. 47th Annual Meeting of the Orthopedic Research Society in San Francisco, CA. February 2001
- Member of American Physical Society
- Member of American Chemistry Society
- Member of Biophysical Society