INHIBITION OF ICE CRYSTAL-GROWTH BY PREFERENTIAL PEPTIDE ADSORPTION - A MOLECULAR MODELING STUDY

A molecular modelling approach has been used to study the relative binding of a winter flounder antifreeze peptide (AFP) to the faces and the internal planes, in particular the c-face and the 20 (2) over bar 1 plane, of the ice (Ih) crystal. The in vacuo binding energies of the peptide molecule with the two surfaces differ by a factor of more than three, which could account for the suggested higher affinity of the molecule for the 20 (2) over bar 1 plane than for the c-face or the prism face. The propensities of the molecule to hydrogen bond with these surfaces are not so different. The key difference in the mode of attachment of the molecule to the various surfaces appears to stem from their geometrical features: the c-face and the prism face are flat, precluding intimate physical contact to be made with the peptide, but the 20 (2) over bar 1 plane contains 'ridges' and 'valleys' which produce a near-perfect steric match for the structure of the peptide molecule, so accommodating it in the 'lock and key' fashion.