Colloquium Natural and Life Sciences - Jay Siegel

Dynamic Symmetry to Reveal Internal Molecular Motions

Normally we talk about symmetry of an object in terms of mirror planes and rotations axis that are actually transformations of the Cartesian coordinates that describe the structure of the object. In the case of molecules it is sometimes convenient to describe the structure by internal coordinates (bond lengths, bond angles, torsions). Transformation of these coordinates can also occur as internal motions of the molecule, such as rotation about a bond or inversion of an umbrella structure. These motions are dynamic symmetries and by controlling the “static" (Cartesian coordinate symmetry) in contrast to the “dynamic” (internal coordinate symmetry) we can detect molecular motions important to the concepts of molecular machines.