Understanding the hydration of cellulose for antifreeze biopolymer design

Irregular freeze-thaw cycles pose a huge threat to infrastructure and life in cold regions such as the arctic. In nature, there exist several organisms such as arctic fish and bacteria, which survive extreme cold by producing antifreeze proteins that prevent ice-formation. Drawing inspiration from nature, we demonstrated in our previous work that cellulose, the most abundant biopolymer on earth, binds to multiple ice-planes and could also be potentially used to design antifreeze agents to prevent ice-growth. A key issue surrounding the development of such antifreeze materials is the incomplete understanding of the phase-change phenomena of the melting of ice and the freezing of water. In this work, we show that the degree of tetrahedrality—a many-body geometrical descriptor—that we used to explain the binding of cellulose to ice, can be further developed into a model that explains the hydration of cellulose near the ice planes. This statistical model can be extended to spatial and temporal dimensions and allows the characterization of water/ice molecules surrounding the antifreeze materials. We use this model for coarse-grained molecule dynamics simulations of water and cellulose to explain how the water molecules are confined near the cellulose to facilitate the ice-binding process and disrupt ice-growth. Finally, we show that this model can describe the hydration at both the atomistic and the coarse-grained length scales.