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The mystery of antifreeze proteins: How do they protect cells from cold?
In cold environments, organisms need special adaptations to survive. Antifreeze Proteins (AFPs) or ice-structuring proteins are a class of polypeptide chains produced by certain animals, plants, fungi and bacteria that enable these organisms to survive at temperatures below the freezing point of water. These proteins inhibit ice growth and recrystallization by binding to small ice crystals, thereby reducing the lethal effects on cells.
Antifrosins are unique in that they can exert their effects at relatively low concentrations, and their mechanism is much more efficient than more common antifreeze agents such as ethylene glycol.
How antifreeze proteins work
The working principle of antifreeze proteins is not just to lower the freezing point, but also involves the so-called "thermal hysteresis". This phenomenon describes the difference between the melting and freezing points of ice crystals. After the addition of antifreeze proteins, the growth of ice crystals is inhibited because these proteins cover the water contact surface of the ice, hindering the thermodynamically favored growth of ice crystals.
For example, antifreeze proteins in fish have shown a thermal hysteresis of about -3.5°C in experiments, allowing them to survive in extremely cold waters.
Freeze-resistant survival strategies: Freeze tolerance and freezing avoidance
Based on the function of antifreeze proteins, organisms can be divided into two categories: "freeze-tolerant" and "freezing-avoiding". Freeze-avoiding organisms can completely prevent the freezing of their body fluids, while freeze-tolerant organisms can withstand the freezing of their body fluids to a certain extent without dying. Such organisms may use antifreeze proteins as protectants to prevent cells from being damaged during the freezing process.
Diversity of antifreeze proteins
There are many known antifreeze proteins, especially those from different organisms, whose structures and properties vary. For example, antifreeze glycoproteins (AFGPs) from Antarctic fish can remain effective in low-temperature environments. These proteins possess complex structures such as α-helical structures based on long peptide chains. On the other hand, antifreeze proteins in plants mainly play a role in inhibiting ice recrystallization, and their thermal hysteresis activity is relatively weak.
Antifreeze proteins have also been found in insects. These proteins have higher activity and highly repetitive structures, which enable them to adapt to extreme low temperature conditions.
Evolution of antifreeze proteins
As for the evolution of antifreeze proteins, scientists point out that the diversity of these proteins may have appeared shortly after the sea level glaciated. This process led to the extinction of some species, while certain organisms with antifreeze proteins were able to survive and adapt to the new living environment. This phenomenon of independently evolving adaptations is called convergent evolution.
Application Prospects
Currently, the research on antifreeze proteins is not limited to basic science, but also shows its potential applications in industry, food preservation and medical treatment. By extracting the properties of antifreeze proteins through artificial synthesis or genetic engineering technology, we may be able to develop more effective antifreeze agents, improve food preservation technology, and increase the tolerance of biological materials to extreme conditions.
The scientific community continues to deepen its research on antifreeze proteins. We can't help but ask, with the advancement of technology, what impact will these antifreeze secrets from nature have on human life in the future?
