Interaction configurations of H2O molecules absorbed in isolated plant cuticles by infrared spectrometry

In a previous article, spectrometric arguments were used to determine the two interaction configurations adopted by H2O molecules present in isolated ivy leaf cuticles which are in equilibrium with atmospheric water molecules. In this article, on the same basis, the configurations of H2O molecules at a higher concentration of water supplied as a droplet deposited on cuticle surfaces are determined. Addition of heavy water allows us to determine the single alcohol site which exchanges its H atom with a D atom in these conditions. The majority of added molecules which are inserted in the cuticle adopt configurations similar to those of volatile H2O molecules which are in equilibrium with atmosphere. An appreciable number of molecules, however, display new configurations. These results show the interest of infrared spectrometry in following hydration processes in biological membranes.