(photo credit: courtesy The Hebrew University of Jerusalem )
For 50 years researchers have been baffled by the enigma of natural antifreeze
production in animals and plants living in cold climates. The natural antifreeze
proteins (AFP) serve as a survival mechanism and prevent organic fluids from
crystallizing and forming ice.
However, a team of Israeli, American and
Canadian scientists that investigated this process believe that it has found an
explanation and recently published their work in the American journal PNAS
(Proceedings of the National Academy of Sciences).
Working on unraveling
the AFP enigma were Dr. Ido Braslavsky of the Hebrew University and Ohio
University, in collaboration with Prof. Peter Davies of Queens University
in Ontario and Prof. Alex Groisman of the University of California in San
The significance of the scientists’ findings offer important
insight on a scientific and practical level. For example, low-fat ice cream
already uses fish AFPs to prevent ice recrystallization, allowing it to maintain
its soft and creamy texture. These proteins can also be used in other frozen
foods for maintaining the desired texture without additional fats, researchers
In medicine, AFPs can be used to improve the quality of sperm,
ovules and embryos stored in a frozen state. Additionally, it can improve the
cyropreservation of organs for transplantation. They can also be used for
cryosurgery and agriculture purposes.
Other studies on AFPs focus on
preparation of recombinant plants and fish with improved survival rates in cold
climates and conditions that lead to dehydration.
such recombinant crops may improve food dispersion over the world.
production of antifreeze proteins in living things is one of the major
evolutionary routes taken by a variety of organisms. These include fish,
insects, bacteria, plants and fungi. To understand how this mechanism works is
significant not only in itself, but also has important implications for
improving food and medicine production around the world, the researchers
Members of the academic community continue to this day to discuss
and debate on the chemistry and physics behind the interactions of AFPs and
In particular, there is an ongoing argument over whether the binding
of certain proteins to ice is reversible. Additionally, opinions vary on whether
the continued presence of these proteins in a solution prevents ice
The challenge in unraveling these questions is finding viable
solutions to produce an experiment in a controlled setting. The growth and
tracking of tiny ice crystals in an environment that mimics the surroundings of
the antifreeze proteins in nature give rise to a host of technical
To circumvent such problems, Israeli and North American
researchers studied the antifreeze protein of the yellow mealworm. This protein
is a hyperactive AFP with a potency to arrest ice growth hundreds of times
greater than the potency of those present in fish and plants.
fluorescent marker version of the AFP was biochemically created in order to
allow for direct observation under a microscopic lens.
The protein was
then injected into custom-designed microfluidic devices with minute diameter
The microfluidic devices were then placed in cooling units
engineered with a temperature control at the level of a few thousandth of a
degree, so that ice crystals of 20 to 50 micrometers could be grown and melted
controllably, all under microscopic observation.
Using this specialized
system, researchers were able to show that the ice grown and incubated in an
antifreeze solution remains coated with protein and thus, protected.
was then shown that the AFPs bind ice directly and strongly enough so as to
prevent the ice from growth even after there is no longer any further presence
of protein in the solution.