Ice crystallization under cryogenic cooling in lipid membrane nanoconfined geometry: Time-resolved structural...

Area of Science:

• Materials Science
• Biophysics
• Physical Chemistry

Background:

• Understanding ice nucleation kinetics in lipid/protein/salt mesophases is crucial for protein crystallography and cryopreservation.
• Ice formation can obstruct the determination of protein crystal structures, necessitating methods to retard its growth.

Purpose of the Study:

• To investigate the dynamics of water-to-ice crystallization in a model lipid/protein/salt mesophase at cryogenic temperatures.
• To understand ice nanocrystal nucleation kinetics within confined lipid membranous systems.

Main Methods:

• Utilized time-resolved synchrotron microfocus X-ray diffraction (TR-XRD) with approximately 40,000 frames.
• Studied a monoolein/hemoglobin/salt/water system, a model for protein-loaded lipid cubic phases (LCP).
• Applied cryostream cooling at 100 K to induce and observe crystallization.

Main Results:

• Observed rapid crystallization of metastable cubic ice (Ic) preceding hexagonal ice (Ih) formation.
• Demonstrated that confinement in nanoscale geometry influences ice crystal structure and kinetics.
• Characterized early nanocrystalline states of water-to-ice transformation in a multicomponent system.

Conclusions:

• The study provides insights into water-to-ice transformation dynamics in confined, multicomponent systems.
• Findings are relevant for improving cryopreservation techniques and understanding natural phenomena involving water crystallization.
• Results can inform the rational design of anti-freezing systems and nanoconfinement physics.