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SUMMARY:Generalizing Euclidean distance to understand polymer uncrossing a
 nd knotting: A physicist’s foray into protein folding - Professor Steven
  Plotkin (The University of British Columbia)
DTSTART:20140508T131500Z
DTEND:20140508T141500Z
UID:TALK52021@talks.cam.ac.uk
CONTACT:Aron Cohen
DESCRIPTION:Physics often deals quite rightfully with symmetries and conse
 rvation laws\, while molecular biology has historically retained little of
  this distinguished standard. Even the simplest biological macromolecules 
 are aperiodic\, have disordered energetics\, and have enormously vast phas
 e space relevant at biological temperatures. A central biophysical problem
  capturing all of these aspects is the question of how a protein\, once sy
 nthesized by a ribosome in the cell\, spontaneously folds up to it’s bio
 logically functional structure. In this context\, equilibrium and non-equi
 librium statistical mechanics\, as formulated in what has been called the 
 energy landscape theory\, has been essential in understanding protein fold
 ing\, function\, and evolution. Unfortunately however\, geometry\, structu
 re\, and transformation often fade away into the ensemble of a statistical
  mechanical description. A fundamental problem which is nevertheless centr
 al to protein folding and structural comparison of biomolecules is the not
 ion of what *distance* means for higher-dimensional objects such as a poly
 mer. Here we generalize the notion of distance between points to the dista
 nce between non-crossing space curves to uniquely define the Euclidean dis
 tance between two biopolymer conformations. We then tackle the conceptual 
 and practical hurdles required to apply this quantity to the problem of pr
 otein folding\; we find that a simple measure of distance\, with no adjust
 able parameters\, predicts folding rates with remarkable accuracy (a corre
 lation of 0.95). We discuss the implications of this finding. 
LOCATION:Department of Chemistry\, Cambridge\, Pfizer lecture theatre
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