Clathrate-Water Interface Control by 2D Janus Amphiphilic Peptide Nanosheets for Ice Recrystallization Inhibition

<b>: </b>Ice-binding proteins (IBPs) in natural, which are known as the important components for preventing organisms from freezing damage, have been of significant interest for freezing point depression. Their ice recrystallization inhibition (IRI) capability has been investigated mainly at local atomic interactions between binding planes of ice crystals and ice-binding moieties. However, IBPs have a specific structure at the macroscale and the flat region on the protein surface binds to ice. We emulated the structural binding of IBPs to ice through the peptide assembly nanostructure. Amphiphilic peptides can be a versatile building block for the fabrication of hierarchical nanostructures based on a couple of non-covalent interactions of amino acids. We designed amphiphilic peptides with aromatic ring, alkyl chain, and negative charge to adjust mutual interaction between peptides. These peptides formed a β-sheet structure to further assemble a two-dimensional (2D) nanosheet with one side hydrophilic and the other side hydrophobic. The ice-binding moieties, coupled to one end of the peptide sequence, were located on the surface of the 2D nanosheet binding with water molecules on the ice crystal surface. The hydrophobic alkyl chains on the other side shielded ice crystal from water molecules which have the potential of becoming ice, thereby inducing IRI. This Janus 2D nanostructure served like a patch which is applied to the surface of the ice crystals, forming a depletion layer of water molecule between the ice crystals. Furthermore, we demonstrated that IRI ability is better when peptides with ice-binding moieties are formed into 2D morphology than into one-dimensional (1D) morphology via subtle modulation of peptide sequence because 2D morphology has a large contact area which can form bonds with water molecules.