Beyond freezing: amorphous water in biomimetic soft nanoconfinement

TL;DR

This study demonstrates that synthetic lipids with specific modifications can create nanoconfinement environments that preserve amorphous water at extremely low temperatures, revealing complex phase behaviors through advanced characterization and simulations.

Contribution

Introduction of a new lipid family enabling biomimetic nanoconfinement of amorphous water down to 10 K, with detailed phase diagram analysis.

Findings

Amorphous water maintained at 10 K within lipid nanoconfinements.

Complex lipid/water phase diagram with multiple liquid crystalline phases.

Molecular dynamics simulations support experimental phase behavior.

Abstract

Water is a ubiquitous liquid with unique physico-chemical 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 into a hexagonal structure, thus creating a state of amorphous water. In this work we introduce a family of synthetic lipids with designed cyclopropyl modification in the hydrophobic chains that exhibit unique liquid-crystalline behaviour at low temperature, enabling maintenance of amorphous water down to 10 K due to nanoconfinement in a bio-mimetic milieu. Small and Wide Angle X-ray Scattering, Elastic and Inelastic Neutron Scattering, Nuclear Magnetic Resonance Spectroscopy and Differential Scanning Calorimetry, complemented by Molecular Dynamics Simulations, unveil a complex lipid/water phase diagram, in which bicontinuous cubic and lamellar liquid crystalline phases containing sub-zero liquid, glassy, or ice water emerge as a competition between the two components, each pushing towards its thermodynamically favoured state.