Past Event: Oden Institute Seminar

The elusiveness of knots in polymers and proteins

Mehran Kardar, Professor, Department of Physics Massachusetts Institute of Technology

Abstract

The abundance of knots in human art and culture indicates a long history of fascination and interest. The scientific classification of knots, however, begins with the work of three Scottish physicists, Thompson, Maxwell, and Tait. This talk will examine knots in polymers, synthetic or biological. Somewhat contrary to intuition, physical considerations (energy or entropy) are found to favor tight knots, with the entanglements localized on relatively small segments. Knots are also statistically rare in swollen (coil) polymers, but abundant in compact (globular) configurations. Yet, investigation of the Protein Data Bank reveals very few knotted structures in globular proteins. I shall discuss some intriguing examples of this set, including the most complicated protein knot (circa 2007) appearing in Human ubiquitin hydrolase, and new knots from the 2008 additions.