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SUMMARY:Some spiral structures in biology - Professor Chris Calladine\, CU
 ED
DTSTART:20121102T140000Z
DTEND:20121102T150000Z
UID:TALK40678@talks.cam.ac.uk
CONTACT:Ms Helen Gardner
DESCRIPTION:Biological structures\, unlike those designed and constructed 
 by human structural engineers\, are built by a process of self-assembly. T
 he internal machinery of biological cells produces molecular building-bloc
 ks in accordance with information encoded in the DNA\, and these then find
  their appointed place in the assembly under construction.   The simplest 
 possible self-assembled structure is a uniform helix\, or spiral: repeated
  addition of identical building-blocks in a regular pattern make a uniform
  helix\, which is the simplest space-curve.\nIn this talk I shall discuss 
 three particular spiral structures built from molecular components.\n1.   
 The α-helix\, an important motif in protein structures\; and in particula
 r the way in which two α-helices can be programmed to assemble into a “
 coiled coil” arrangement.\n2.   The DNA double-helix.  How it can switch
  between the classical “A” and “B” geometries\;  and how this kind
  of change enables us to understand sequence-dependent curvature and flexi
 bility of the molecule – which is important in the recognition of DNA se
 quences by contacting proteins.\n3.   Bacterial flagellar filaments – th
 e corkscrew-like organelles which\, when rotated by their motors\, enable 
 bacteria such as E.coli to swim in their watery environment and navigate t
 owards nutrients.  Here the building-block\, much larger than those of exa
 mples 1 and 2\, is a protein molecule which contains a “switch” featur
 e\; and this enables the filament to change from a left-handed to a right-
 handed corkscrew when it is driven in reverse.\nThese examples illustrate 
 the power of evolution to develop highly sophisticated variants of the sim
 plest kind of self-assembled biological structures.  Geometry provides an 
 indispensable tool in elucidating the subtle structural phenomena seen in 
 these helices.  \n
LOCATION:Oatley Seminar Room\, Department of Engineering
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