By Dave DeFusco
When water freezes, ice crystals grow quickly, spreading across surfaces and binding together. For humans, that can mean frozen windshields, icy sidewalks and frostbite. For fish, insects and plants living continuously in very cold environments, ice can be deadly by puncturing cells and damaging tissues.
To fight this, nature has evolved special tools called antifreeze proteins (AFPs). These proteins attach themselves to ice crystals and prevent them from getting bigger, even at temperatures far below the temperature where water freezes. Exactly how AFPs work has been a long-standing scientific puzzle.
A recent study, 鈥,鈥 published in The Journal of Physical Chemistry, takes a major step toward solving that mystery.
The research, co-authored by Yitzhar Shalom, a graduate of the Katz School of Science and Health and YU鈥檚 Stern College for Women, Dr. Fredy Zypman, a professor in the M.A. in Physics, and Dr. Ran Drori, senior author and Katz School industry professor and associate professor in the Stern College for Women, shows that when antifreeze proteins are engineered to work together in groups rather than alone, they don鈥檛 just add their strengths, they multiply them.
To understand the breakthrough, imagine three versions of an antifreeze protein:
- Monomer: A single unit of the protein, like one Lego block.
- Dimer: Two units linked together.
- Multimer: A large assembly of 12 units, like a full Lego structure.
The researchers tested how well each version could stop ice from growing. Unsurprisingly, the single unit was weakest, the pair worked a little better and the 12-unit multimer was strongest, however the key discovery was why the multimer worked so well.
鈥淲e found that once the first subunit of the multimer attaches to ice, it makes it much easier for the next one to attach and then the next,鈥 said Shalom. 鈥淚t鈥檚 a cooperative effect; each step helps the next one happen faster. That鈥檚 why the multimer binds to ice 11 times faster than the single-unit protein.鈥
To measure this, the team used fluorescence microscopy, a technique that lets scientists watch proteins light up as they stick to ice. This way, they could see how quickly the proteins covered an ice surface.
鈥淥ur analysis required us to refine the traditional mathematical models of how molecules stick to surfaces,鈥 said Zypman. 鈥淭he revised model allowed us to capture this cooperative behavior in the multimer, something the old models couldn鈥檛 explain.鈥
This modeling was essential for linking what the team saw under the microscope to the broader physics of how ice grows or, in this case, how it stops growing.
Antifreeze proteins have fascinated scientists for decades, not only for what they teach us about life in extreme environments but also for their practical potential. They could improve food storage, make crops more frost-resistant, protect organs during freezing for transplants and even prevent dangerous ice buildup on airplane wings. Efforts to design synthetic versions, however, have fallen short, largely because the details of how AFPs actually work remained murky.
鈥淲hat we鈥檙e showing here is that the secret isn鈥檛 just in the protein itself, but in how proteins can work together,鈥 said Drori. 鈥淭hat cooperative binding is what gives the multimer its superior activity. Understanding this opens the door to designing better antifreeze materials, both biological and synthetic.鈥
This work not only explains a new mechanism of ice-binding, it also provides a framework for designing future proteins. By showing that speed of binding is linked directly to antifreeze activity, the researchers have given scientists a measurable target to aim for when creating new antifreeze solutions.
For Shalom, the project was also a chance to push the boundaries of what鈥檚 known. 鈥淭he exciting part is that we鈥檙e not just describing nature, we鈥檙e engineering it,鈥 he said. 鈥淲e鈥檙e learning the rules of how these proteins work and then using those rules to make them even better.鈥
As Drori put it: 鈥淚ce can be destructive, but proteins have evolved incredible ways to stop it. By understanding those tricks, we can learn to control ice in ways that were once unimaginable.鈥
