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SUMMARY:Single Molecule Force-Spectroscopy Maps the Details of the Protein
  Free Energy Landscape - Dr Jasna Brujic (Fernandez Lab\, University of Co
 lumbia)
DTSTART:20060602T100000Z
DTEND:20060602T110000Z
UID:TALK5044@talks.cam.ac.uk
CONTACT:vh233
DESCRIPTION:Understanding the effect of mechanical stress on biological sy
 stems is of fundamental importance since it is a key parameter always pres
 ent in Nature. In particular\, it is thought that force has played an impo
 rtant role in the evolution of proteins\, such that they can perform their
  function\, i.e. fold and unfold\, under stress. The development of novel 
 single molecule AFM techniques in combination with protein engineering tec
 hniques has paved the path for the study of the mechanical design of modul
 ar proteins. The possibility of holding the protein at a constant force pe
 rmits us for the first time to examine the folding and unfolding trajector
 y of a protein under a stretching force.\n\nI will present a kinetic analy
 sis of the unfolding times of the protein to measure the diversity of mech
 anical unfolding pathways. We find a surprisingly broad distribution of un
 folding rates that follows a power law. This result is exciting because it
  suggests that the underlying free energy landscape consists of an exponen
 tially distributed density of states\, reminiscent of spin-glasses. Our re
 sults predict the existence of a ``glass transition'' force below which th
 e folded conformations interconvert between local minima on multiple time-
 scales. These novel techniques open the field of statistical energy landsc
 ape theories of protein folding to experimentation.\n\nQuestions about the
  validity of the two-state or funnel models for folding\, the folding free
  energies\, the corresponding end-to-end length fluctuations\, as well as 
 the cooperative nature of folding multiple protein domains will then lead 
 us into a rich discussion. 
LOCATION:Small Lecture Theature\, Cavendish Laboratory\, Department of Phy
 sics
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