Dresden 2003 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
DF: Dielektrische Festkörper
DF 5: Gl
äser II (gemeinsam FV DF/DY)
DF 5.4: Vortrag
Dienstag, 25. März 2003, 15:30–15:45, HSZ/403
Water in plant cell walls can be supercooled to 200 K and freezes to a new form of amorphous ice — •Martin Müller1, Helmut Schober2 und Gero Vogl3 — 1Institut f. Exp. u. Angew. Physik, Uni Kiel, 24098 Kiel — 2ILL, B. P. 156, F-38042 Grenoble Cedex 9 — 3Inst. f. Materialphysik, Uni Wien, Strudlhofgasse 4, A-1090 Wien
Many unique features of water in plant cell walls have been reported over the last decades. Water adsorbed to the disordered regions of cellulose, the main constituent of plant cell walls, exhibits liquid dynamics below 0 ∘C and is therefore termed “non-freezing”. The water molecules are thought to be inserted between individual hydrogen bonded cellulose chains, and they do not form crystalline ice networks. However, neither the structural properties of water in cellulose nor the nature of the freezing transition are fully understood. Here we show that neutron scattering techniques provide the missing clues for a structural and dynamic model of water in plant cell walls below 0 ∘C. Upon cooling, an increasing part of the water molecules freezes in a gradual, heterogeneous glass transition to a new type of amorphous ice. The remainder is supercooled and is liquid down to 200 K with its dynamics being strongly retarded. The confinement in disordered cellulose hinders water crystallization and, thus, protects cell walls from frost damage.