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    Department of Mathematics and Department of Mathematical Sciences
                   The Johns Hopkins University

                              JOINT SEMINAR

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Erica Flapan                                   December 13, 2001
Department of Mathematics                      211 Krieger Hall (Note Place)
Pomona College                                 Seminar: 4:30 p.m. (and time)

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                      WHEN TOPOLOGY MEETS CHEMISTRY


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                               ABSTRACT

Stereochemistry is the study of the 3-dimensional structure of molecules, 
and geometric topology is the study of those properties of geometric objects
that are invariant under continuous deformation.  It is not obvious that
these two fields have anything in common.  In fact, not long ago there was
little communication between researchers in these two areas.  Prior to forty
years ago, analyzing the topological properties of existing molecular
structures was not very difficult, because as topological objects, the
graphs of all of the molecular structures known at the time could be
deformed into a plane.  Thus understanding the stereochemistry of a molecule
only required the evaluation of its geometry and not its topology.
Recently, knots and links and other non-planar molecules have been
synthesized whose structures and properties come from their topology as well
as their geometry.  These molecules are often large enough that they no
longer have the rigidity that is characteristic of small molecules, so
understanding their deformations is an important part of understanding their
structure.  In this talk we will discuss how topology can be used to help us
undertand the symmetries of such flexible molecules.