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Updated: Oct 9, 2025

Determining the Ice-binding Planes of Antifreeze Proteins by Fluorescence-based Ice Plane Affinity
Published on: January 15, 2014
Diffusion Attachment Model for Long Helical Antifreeze Proteins to Ice.
Kartik Kamat1, Pavithra M Naullage2, Valeria Molinero2
1Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, California 93106, United States.
Antifreeze proteins (AFPs) bind ice, but most orientations are blocked. This study reveals how restricted AFP orientations create an entropic barrier, slowing ice binding and impacting biological environments.
Area of Science:
- Protein-ice interactions
- Biophysical chemistry
- Molecular dynamics
Background:
- Potent antifreeze proteins (AFPs) are rigid helical structures.
- AFPs bind ice at specific orientations, with one side contacting the ice surface.
- Most AFP orientations are sterically inaccessible upon approaching ice.
Purpose of the Study:
- To explore the effect of inaccessible orientations on AFP adsorption rate to ice.
- To develop a theory predicting the rate constant for AFP adsorption (k_on).
- To quantify the entropic barrier to AFP adsorption.
Main Methods:
- Developed a diffusion-controlled adsorption kinetics theory.
- Accounted for orientational restrictions during AFP adsorption.
- Calculated the entropic barrier for various AFPs.
Main Results:
- The adsorption rate constant (k_on) decreases with AFP length and diameter.
- k_on is inversely proportional to the AFP binding surface area.
- Restricted orientations create an entropic barrier of approximately 7-9 k_B*T for AFP adsorption.
Conclusions:
- Entropic barriers due to restricted AFP orientations significantly impact ice binding kinetics.
- These entropic and diffusion resistances can be comparable in confined biological spaces.
- The findings provide insights into AFP function in biological environments.
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