  Large molecules have complex potential-energy surfaces with many local
minima. They exhibit multiple stereo-isomers, even at very low temperatures. In
this paper we discuss the different approaches for the manipulation of the
motion of large and complex molecules, like amino acids or peptides, and the
prospects of state- and conformer-selected, focused, and slow beams of such
molecules for studying their molecular properties and for fundamental physics
studies. Accepted for publication in Faraday Disc. 142 (2009), DOI:
10.1039/b820045a
