Extra Fysisch Colloquium Universiteit Leiden

Studying the Adsorption of Antifreeze Glycoproteins (AFGP 8) on Mica by AFM

Osnat Younes-Metzler, Department of Physics, Technische Universität München

Location: LION, C.J. Gorterzaal – 173 Oortgebouw Time: 16.00 hrs

Antifreeze glycoproteins (AFGPs) are unique biomolecules found in several arctic and antarctic fish. These novel compounds allow these organisms to survive cold conditions by inhibiting the growth of ice. AFGPs do not prevent the formation of ice, but instead these proteins operate by modifying the ice morphology and inhibiting the further growth of ice. Biological antifreeze proteins provide an impressive example of macromolecules with specific recognition capabilities for inorganic structures. During the past decade, a great deal of effort has been expended to more thoroughly understand the mechanism by which biological antifreeze proteins bind to ice and inhibit its growth. Although it has been proposed that the hydrophilic interactions between polar hydroxyl groups on the disaccharides and the water molecules on the ice surface are extremely important, others believe that entropic and enthalpic contributions from hydrophobic residues are crucial in the binding of AFGP to the ice surface. Here, we studied the adsorption, as well as surface patterning, of antifreeze glycoprotein fraction 8 (AFGP 8) on mica via a solvent evaporation method. A strong affinity of this protein to hydrophilic surface of the mica was observed. In a successful attempt of surface patterning, lines of AFGP 8 particles and gridlike patterns were formed as a result of the receding of the droplet contact line and the accumulation of the solute during evaporation. The solution concentration strongly affects the protein line spacing. The average height of the protein was measured to be 8.1+/-2.5 Å, which may be attributed to the height of a single molecule.