Interfacial Ice Density Fluctuations Inform Surface Ice-Philicity.

Area of Science:

• Surface science
• Computational chemistry
• Biophysics

Background:

• Surface ice-philicity governs ice nucleation and binding, but its relationship with surface features is poorly understood, especially for heterogeneous surfaces like proteins.
• Analogous to hydrophobicity studies, ice-philic surfaces may exhibit enhanced ice-like density fluctuations.
• Characterizing ice-philicity is crucial for understanding ice interactions in biological and material systems.

Purpose of the Study:

• To investigate the link between surface properties and ice-philicity using molecular simulations.
• To establish a quantitative measure for ice-philicity based on interfacial ice-density fluctuations.
• To characterize the ice-philicity of both model surfaces and complex biological molecules, such as antifreeze proteins.

Main Methods:

• Molecular simulations and enhanced sampling techniques were employed.
• A family of model surfaces with varying wetting coefficients (k) was analyzed.
• Interfacial ice-density fluctuations were used as a metric for ice-philicity.

Main Results:

• The free energy of ice-density fluctuations decreases monotonically with increasing wetting coefficient (k).
• For fcc systems, the (110) surface demonstrated higher ice-philicity than (111) or (100) surfaces due to topographical complementarity with ice basal planes.
• The ice-binding site (IBS) of the spruce budworm antifreeze protein (sbwAFP) showed enhanced ice-density fluctuations, indicating higher ice-philicity compared to non-binding sites (NBSs).

Conclusions:

• Interfacial ice-like fluctuations serve as a reliable measure for surface ice-philicity.
• The study provides a method to characterize the ice-philicity of heterogeneous surfaces, including proteins.
• Findings elucidate the molecular basis of ice-surface interactions and offer insights for designing ice-interacting materials.