Boreal pollen contain ice-nucleating as well as ice-binding 'antifreeze' polysaccharides.
Ice nucleation and growth is an important and widespread environmental process. Accordingly, nature has developed means to either promote or inhibit ice crystal formation, for example ice-nucleating proteins in bacteria or ice-binding antifreeze proteins in polar fish. Recently, it was found that birch pollen release ice-nucleating macromolecules when suspended in water. Here we show that birch pollen washing water exhibits also ice-binding properties such as ice shaping and ice recrystallization inhibition, similar to antifreeze proteins. We present spectroscopic evidence that both the ice-nucleating as well as the ice-binding molecules are polysaccharides bearing carboxylate groups. The spectra suggest that both polysaccharides consist of very similar chemical moieties, but centrifugal filtration indicates differences in molecular size: ice nucleation occurs only in the supernatant of a 100 kDa filter, while ice shaping is strongly enhanced in the filtrate. This finding may suggest that the larger ice-nucleating polysaccharides consist of clusters of the smaller ice-binding polysaccharides, or that the latter are fragments of the ice-nucleating polysaccharides. Finally, similar polysaccharides released from pine and alder pollen also display both ice-nucleating as well as ice-binding ability, suggesting a common mechanism of interaction with ice among several boreal pollen with implications for atmospheric processes and antifreeze protection.
Bielefeld University, Faculty of Chemistry, Atmospheric and Physical Chemistry, D-33615 Bielefeld, Germany.
Katharina
K
Dreischmeier
Bielefeld University, Faculty of Chemistry, Atmospheric and Physical Chemistry, D-33615 Bielefeld, Germany.
Carsten
C
Budke
Bielefeld University, Faculty of Chemistry, Atmospheric and Physical Chemistry, D-33615 Bielefeld, Germany.|Bielefeld University, Faculty of Chemistry, Physical and Biophysical Chemistry, D-33615 Bielefeld, Germany.
Lars
L
Wiehemeier
Bielefeld University, Faculty of Chemistry, Physical and Biophysical Chemistry, D-33615 Bielefeld, Germany.
Tilman
T
Kottke
Bielefeld University, Faculty of Chemistry, Atmospheric and Physical Chemistry, D-33615 Bielefeld, Germany.|Bielefeld University, Center for Molecular Materials, D-33615 Bielefeld, Germany.
Thomas
T
Koop
D000064:Acclimatization; D029662:Betula / Q000737:chemistry / Q000378:metabolism*; D005615:Freezing; D007053:Ice; D011058:Pollen / Q000737:chemistry / Q000378:metabolism*; D011134:Polysaccharides / Q000737:chemistry / Q000378:metabolism*
D007053:Ice; D011134:Polysaccharides