By Josh Perry, Editor
Researchers from ETH Zurich and the University of Zurich (Switzerland) pinpointed a method for preventing water from forming ice crystals even at extreme sub-zero temperatures by confining it in tiny channels within a novel lipid compound.
Three-dimensional model of the novel lipid mesophase: This cubic motif is repeated regularly in the material. (Peter Rüegg/ETH Zurich)
According to a report from ETH Zurich, the researchers developed a new class of lipids called lipidic mesophase. The lipids spontaneously aggregate into soft membranes that form a network of uniform channels less than one nanometer in diameter.
“What’s so special about this structure is that – unlike in an ice-cube tray – there is no room in the narrow channels for water to form ice crystals, so it remains disordered even at extreme sub-zero temperatures,” the article explained. “The lipids don’t freeze either.”
Scientists used liquid helium to cool a lipidic mesophase to as low as -263°C (10 degrees above absolute zero) but no ice crystals formed. The water was described as “glassy”.
“It is the water content in the mixture that determines the temperatures at which the geometry of the mesophase changes,” the article continued. “If, for example, the mixture contains 12 percent water by volume, the structure of the mesophase will transition at about -15°C from a cubic labyrinth to a lamellar structure.”
While researchers focused on using these materials for future study of proteins and biomolecules, there could be potential applications where freezing must be prevented.
The research as recently published in Nature Nanotechnology. The abstract read:
“Water is a ubiquitous liquid with unique physicochemical properties, whose nature has shaped our planet and life as we know it. Water in restricted geometries has different properties than in bulk. Confinement can prevent low-temperature crystallization of the molecules into a hexagonal structure and thus create a state of amorphous water.
“To understand the survival of life at subzero temperatures, it is essential to elucidate this behaviour in the presence of nanoconfining lipidic membranes. Here we introduce a family of synthetic lipids with designed cyclopropyl modifications in the hydrophobic chains that exhibit unique liquid-crystalline behaviour at low temperature, which enables the maintenance of amorphous water down to ~10 K due to nanoconfinement.
“The combination of experiments and molecular dynamics simulations unveils a complex lipid–water phase diagram in which bicontinuous cubic and lamellar liquid crystalline phases that contain subzero liquid, glassy or ice water emerge as a competition between the two components, each pushing towards its thermodynamically favoured state.”