AFM imaging of extracellular ice nucleators

Area of Science:

• Biophysics
• Materials Science
• Food Science

Background:

• Ice nucleators initiate water crystallization at temperatures above -10 °C.
• Extracellular ice nucleators (ECINs) are cell-membrane derived proteins retaining ice nucleation activity.
• ECINs have potential applications in food preservation and energy-efficient freezing.

Purpose of the Study:

• Investigate the surface morphology of nano-thin ECIN layers.
• Determine the effect of immobilization methods and material properties on ECIN activity.
• Explore practical applications of ECIN layers in food science.

Main Methods:

• Atomic Force Microscopy (AFM) in tapping mode to image ECIN surface morphology.
• Layer-by-layer deposition to immobilize ECINs onto polyelectrolyte multilayers.
• Testing ice nucleation activity of ECIN layers in food solutions.

Main Results:

• AFM revealed globular and rod-like structures on nano-thin ECIN layers.
• ECIN activity was retained on silicon wafer surfaces as nano-thin layers.
• Higher ECIN concentration led to faster nucleation, higher temperatures, and denser layers.
• Protein aggregate size reduction (via centrifugation) decreased ice nucleation activity.

Conclusions:

• Nano-thin ECIN layers maintain significant ice nucleation properties.
• ECIN layer properties (density, thickness) are influenced by solution concentration and preparation methods.
• ECIN layers offer potential for accelerated freezing and enhanced frozen food stability.