Coexistence of dihydrogen, blue- and red-shifting hydrogen bonds in an ultrasmall system: Valine

(Figure presented) Conformational space of valine: Dihydrogen, blue- and red-shifting H bonds coexist in the single molecule, valine (see picture). All functional groups of valine participate in H bonding and the amino and carboxyl group play the dual role of H-bond donor and acceptor. As all known H-bond types coexist in valine, a unifying concept of hydrogen bonding is depicted. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.