Have you ever wondered how fish survive in freezing
Arctic oceans, or how an Alaskan beetle withstands
negative 30 degrees? In this episode of The Deep
Dive, we unpack the miraculous world of antifreeze
proteins, AFPs, and ice -structuring proteins,
ISPs. We explore the evolutionary heists, the
quantum -level physics of thermal hysteresis,
and the mind -bending biology that prevents living
cells from turning into solid ice. Plus, discover
how these same biological cheat codes are sitting
in your kitchen freezer right now, and how they
might just be the key to human cryopreservation
and space exploration. Tune in for a fascinating
journey through extreme survival, convergent
evolution, and the future of cryobiology. Have
you ever left a glass bottle of water in the
freezer and just completely forgotten about it?
Oh, definitely. Right. And you come back a few
hours later, maybe the next morning, and you
open the freezer door to an absolute disaster.
It's just shattered glass everywhere. Everywhere.
The water inside froze, it expanded, and it just
violently destroyed its container. Because water
expands when it turns to ice. It's just a fundamental
rule of nature. Exactly. Now... I want you to
take that exact same scenario, but I want you
to shrink it down to the microscopic level. you
know, jagged expanding ice crystals forming not
inside a rigid glass bottle, but inside the incredibly
delicate microscopic cells of a living organism.
That sounds like a nightmare. It really is. By
all the laws of biology, physics, and chemistry,
it should be an absolute death sentence. The
physical expansion alone would just rupture the
cell membranes, shred the internal organelles,
systematically destroy the tissue from the inside
out. It should be game over. Yeah. And yet, if
you look at our planet life... is incredibly
almost absurdly stubborn. It really is. I mean
life absolutely thrives in the freezing, lightless
oceans of Antarctica. It thrives beneath miles
of pack ice in the Arctic and it survives the
bitter sub -zero winters of the Northern Hemisphere.
It's a fundamental biological paradox. It's puzzled
scientists for generations, honestly. Because
they should just freeze. Exactly. We are talking
about environments where the ambient temperature
drops well below the freezing point of water.
And since living things, from a microscopic algae
to a massive fish, are largely made of water.
They're essentially just big bags of water. Right.
So they should theoretically freeze solid the
moment the temperature dips. Their blood should
turn to slush. Their cells should crystallize.
But they don't. And the way they avoid this seemingly
inevitable biological fate is nothing short of
an evolutionary miracle. And that brings us to
the mission for today's deep dive. We are going
to discover the biological cheat codes that allow
life to survive the deep freeze. I like that.
Cheat codes. It really feels like they are hacking
the system. Our source material for this exploration
is a really comprehensive look into a miraculous
class of molecules known as anti -freeze proteins.
Or AFPs, for short. Yes, AFPs. Though, as you'll
find out a bit later today, if you look at a
food label, they are sometimes more commercially
known as ice -structuring proteins. Which is
a brilliant rebrand. It is. Okay, let's unpack
this. Because when I first started reading through
these sources, I thought, uh, I thought this
was just about a few weird fish. But how big
is the scope of this phenomenon, really? The
scope is massive. And frankly, it spans the entire
tree of life. Wow. In this deep dive, we are
going to explore the literal physics of freezing
and how these incredibly specialized proteins
hack those physics. We'll look at the wild evolutionary
leaps that created them too. Exactly. Sometimes
seemingly out of nowhere or through methods that
defy our traditional understanding of genetics,
we will examine the surprising and frankly beautiful
diversity of these molecules across fish, insects,
plants, fungi, and microbes. It's everywhere.
And finally, we will look at how these very same
proteins have made the leap from the freezing
Arctic oceans into commercial everyday applications.
Which is my favorite part. There is a very good
chance that some of the mechanisms we discussed
today are sitting right inside your kitchen freezer
right now. I absolutely love that. It takes something
so alien and just brings it right into your home.
So I want to start by redefining what we mean
by the word antifreeze. That's a good place to
start. Because I think for you, me, and anyone
listening, when you hear that word, your mind
immediately goes to the garage. Right, car maintenance.
You think of that brightly colored neon green
or pink toxic liquid you pour into your car's
radiator before the winter hits. Which is usually
a chemical called ethylene glycol. And it works
by what chemists call colligative properties.
Which is the term that sounds a bit intimidating.
It does. But it essentially means it works by
sheer brute force volume. Right. I was reading
that with car antifreeze, you literally have
to pump a ton of it into the water to get the
freezing point to drop. You're fundamentally
changing the ratio of the liquid. It's like trying
to stop a crowd from dancing by just shoving
an equal number of people who refuse to dance
into the room. That is a brilliant way to put
it. It's a volume game. Just crowding the floor.
And if we connect this to the bigger picture
of a living, breathing organism, a brute force
approach just isn't biologically viable. Because
you can't just fill a fish with neon green chemicals.
Exactly. You cannot simply pump a living fish
full of a traditional solute like ethylene glycol.
And even if it wasn't toxic, you couldn't pump
them full of massive amounts of salt or sugar
to lower their freezing point either. Because
it would completely mess up their internal balance,
right? I mean, fish already have to regulate
their salt levels so carefully. Exactly. It would
cause a massive fatal shift in osmotic pressure.
Osmosis being the water balancing act. Right.
Osmosis is the process that dictates that water
always wants to balance out solute concentrations
across a cell membrane. If a cell suddenly floods
its interior with massive amounts of a solute,
like sugar or salt, just to prevent freezing,
the water outside the cell would rush in to dilute
it. And the cell would swell up. And literally
burst. Or, conversely, If the solute was heavily
concentrated in the blood, it would draw all
the water out of the surrounding tissues, completely
dehydrating the animal from the inside out. So
the animal would basically turn into a piece
of biological beef jerky. Precisely. They would
die of dehydration while surrounded by water.
That is a terrible irony. So the absolute beauty
of antifreeze proteins is that they work in a
non -colligative manner. Meaning they don't rely
on sheer volume at all. Not at all. I was floored
by the numbers in our sources. They note that
AFPs are effective at concentrations 1 300th
to 1 500th of other dissolved solutes. It's a
fraction of a fraction. If we go back to our
room full of dancers, instead of flooding the
room with non -dancers, the organism just sends
in two or three highly trained bouncers to stand
exactly where the dancing starts and shut it
down. I like the bouncer analogy. It is a hyper
precise biochemical surgical strike. They don't
flood the system. They target the problem at
incredibly low concentrations, which completely
minimizes any dangerous effect on the organism's
delicate osmotic pressure. execute that targeted
strike is through a fascinating physical mechanism.
They don't just float around randomly. They selectively
seek out and bind to specific crystalline forms
of ice the microsecond they begin to form. Just
grabbing them. Essentially creating a physical
blockade that stops the ice nucleation process
dead in its tracks. And this leads us to a term
in the source material that I absolutely have
to geek out over. Oh, I know which one you mean.
The term is thermal hysteresis. I'm not gonna
lie, it sounds like an incredible sci -fi band
name. It really does. But it is actually the
core fundamental mechanism of how AFPs keep these
creatures alive. It is a great term, and it is
the key to everything we are talking about today.
Hysteresis generally refers to a phenomenon where
the state of a system depends on its history,
or where there's a lag in a reaction. Okay. To
break thermal hysteresis down for you in this
context, it is effectively the artificial gap
created between the melting point of water and
the freezing point of water. Right, because normally
those two things are the exact same temperature.
Water freezes at zero degrees Celsius and ice
melts at zero degrees Celsius. It's a two -way
street at the exact same intersection. Exactly.
Under normal thermodynamic laws, it's a perfectly
balanced equilibrium. But when an organism possesses
antifreeze proteins, it breaks that equilibrium.
Those proteins physically wedge themselves at
the microscopic interface between the solid ice
crystal and the liquid water surrounding it.
And by doing this, they kinetically inhibit the
growth of the ice crystal. They push the freezing
point down while the melting point remains exactly
the same. I love the phrasing in the source material.
It stops the thermodynamically favored growth.
Yes. Physics says, I am at zero degrees, I want
to freeze, I need to freeze. And the protein
steps right in the middle of that chemical reaction
and says, access denied. That is a perfect way
to visualize it. The proteins literally cover
the water -accessible surfaces of the microscopic
ice crystals. They hold open this gap, this hysteresis.
They create a state of tension where the water
should be ice, but it is forced to remain liquid.
And looking at the data from the sources, the
maximum level of thermal hysteresis shown by
fish AFPs is approximately negative 3 .5 degrees
Celsius. Which is about 29 .3 degrees Fahrenheit.
Now, when I first read that, I thought, wait,
negative 3 .5 degrees? That doesn't sound like
a massive drop. It doesn't sound like much. I
was expecting them to push it down to negative
50 or something. Yeah, sure. But then the material
clarified why that is exactly, perfectly what
they need. Right, because aquatic organisms are
typically only exposed to water temperatures
that drop to about negative 1 or negative 2 degrees
Celsius below freezing. Because ocean water itself
generally freezes around negative 1 .9 degrees
Celsius. The salt content lowers the freezing
point of the ocean itself. Exactly. So if the
fish's blood is protected down to negative 3
.5, that gives them an absolutely perfect, comfortable
safety buffer. but there is a catch here, isn't
there? It's not a flawless magic shield. This
raises an important question about the limits
of biology, and you are right to point it out.
The catch is that the rate of cooling absolutely
matters. These proteins are incredible marvels
of engineering, but they are still physical molecules
floating in a fluid. Many time to work. They
require a little bit of time to physically find
the nascent ice crystals. orient themselves and
bind to them. So if there is a sudden rapid plunge
in temperature? It can actually substantially
decrease the thermal hysteresis value. Oh, wow.
The freezing point drops so fast and the ice
grows with such violent speed that the proteins
simply cannot keep up. They are overwhelmed.
Consequently, these organisms can still easily
freeze to death if the temperature drops too
abruptly. So they need the cold to arrive at
a relatively natural gradual pace. Yes, so their
internal defenses can mobilize and cap the ice
crystals as they form. So it is this dynamic,
high -stakes battle between the speed of the
temperature drop and the physical reaction time
of the proteins. It's a race. That is incredibly
dramatic when you think about it happening inside
the blood vessels of a tiny fish. and it perfectly
sets up something else I found fascinating in
the sources, which is... Not every organism uses
these proteins the exact same way. The material
outlines two very distinct survival camps. I'll
admit, one makes total sense to me, and the other
sounds completely insane. I think I know where
you're going with this. Can you clarify the difference
between the freeze -avoidant species and the
freeze -tolerant species? Gladly. The first camp
is the freeze -avoidant species, which is the
one that... probably makes the most intuitive
sense. Right. These are the organisms, like the
fish we just discussed, that use AFPs to prevent
their body fluids from freezing entirely. Their
singular goal is zero internal ice. They hold
the line, they use the proteins to create that
thermal hysteresis gap, and as long as they stay
within that temperature buffer they remain completely
liquid. But as we just discussed with the cooling
rates, if the temperature drops too low or too
fast, the AFP function is overwhelmed, ice grows
rapidly throughout their body fluids, and they
die. Yes. For them, any significant internal
freezing is fatal. It's an all -or -nothing defense
mechanism. The shield either holds, or the organism
perishes. But the second camp, the freeze -tolerant
species. This is the one where my mind just gets
blown. It is truly remarkable. Freeze -tolerant
species actually survive the freezing of their
internal body fluids. They don't just tolerate
the cold. They tolerate turning into ice. For
these organisms, the AFPs aren't trying to stop
the freeze entirely. They aren't trying to maintain
a purely liquid state. So what are they doing?
Instead, they act as what we call cryoprotectants.
Meaning, they manage the freezing process rather
than preventing it? Exactly. But how does that
not shred their cells like the glass bottle in
the freezer? Because they inhibit something called
recrystallization. Recrystallization? When ice
first forms, it usually starts as lots of very
tiny microscopic crystals. On their own, these
tiny crystals aren't immediately lethal. Okay.
But over time, thermodynamics pushes those tiny
crystals to fuse together into larger, much more
stable, and much more destructive ice crystals.
The large crystals that act like microscopic
knives, slicing through cell membranes and destroying
tissue. Okay, so the AFPs in freeze -tolerant
species, they bind to the tiny crystals and stop
them from fusing together. Yes, they keep the
ice small and manageable. This stabilizes the
cell membranes and prevents the massive tissue
damage. the deadly knives into harmless sand.
That is exactly it. What's fascinating here is
that to pull this off, these freeze -tolerant
organisms often work in conjunction with another
type of protein altogether. Called ice -nucleating
proteins, or INPs. Yes. Now wait, I had to read
this twice in the notes. They actually have a
protein specifically dedicated to starting the
freezing process. Why would they want to do that?
It sounds counterintuitive, but it's a stroke
of genius. The INPs intentionally trigger the
freezing process at relatively high sub -zero
temperatures. Oh. Because if they control when
it freezes, they control how it freezes. Exactly.
They take control of the environment. By initiating
the freeze early and predictably, it allows the
organism to control the rate of ice propagation.
It's a slow... managed rollout of ice. The INPs
start the fire, so to speak, in a controlled
manner, while the AFPs ensure the resulting iced
crystals stay incredibly small and harmless.
It is a highly choreographed biologically controlled
freeze that allows the organism to survive being
effectively frozen solid for months at a time.
It's brilliant biological engineering. They aren't
fighting nature. They are conducting it. So now
that we have the physics down, the hysteresis,
the bouncers at the door, the managed freezing,
let's dive into the animals themselves. Let's
do it. Because the history of how we even figure
this out is a great story. Let's set the scene.
It is the 1950s. We have a Norwegian scientist
named Scollander. A pioneer in the field. He
is out on boats in the freezing, brutal conditions
of the Arctic. He is pulling up these fish from
the dark water and he is just absolutely baffled.
Because they should be dead. He is taking temperature
readings, and the water is definitively colder
than the known freezing point of the fish's blood.
By all rights, the moment these fish are pulled
out, or even while they are swimming, they should
be solid blocks of ice floating in the sea. He
suspects there must be some sort of antifreeze
dissolved in their blood, but the analytical
tools of the 1950s just aren't quite there to
let him pin it down. He knows it's happening,
but he can't prove how. It was an incredible
biological mystery. It really was. It wasn't
until a couple of decades later, in the late
1960s, that an animal biologist named Arthur
de Vries finally managed to isolate the culprit.
And he was working in the Antarctic, right? He
was. And through rigorous chemical isolation
techniques, he discovered a unique class of molecules
in their blood that he called antifreeze glycoproteins,
or AFGPs. Antifreeze glycoproteins. And this
discovery completely changed how we viewed cold
weather biology. But my favorite part of the
source material is why these fish had them in
the first place. Yes. And if we connect this
to the bigger picture, to understand why debris
found these highly specialized proteins in Antarctic
fish, we have to zoom way, way out. Like geological
time scales. Exactly. We have to look back at
the geological and climatic history of the entire
planet. The sources detail some incredible data
pulled from deep sea ocean drilling cores. Those
are the literal cylinders of Earth pulled from
the ocean floor. Yes. That allows scientists
scientists to read the history of the planet's
climate like the rings of a tree. And those cores
reveal an incredible dramatic story. Over 30
million years ago, a massive planet -altering
geological shift occurred. The continents were
shifting, and this led to the formation of the
Antarctic Circumpolar Current. This is that massive,
incredibly powerful ocean current that constantly,
relentlessly circles the entire continent of
Antarctica, right? It is. And when that current
formed 30 million years ago, it effectively created
a dynamic physical wall around Antarctica. Wow.
It isolated the continent and its surrounding
waters from the warmer, more temperate ocean
currents of the rest of the globe. It basically
cut off the global central heating. Exactly.
This initiated a massive planetary cooling event
in the southern hemisphere. The oceans around
Antarctica plummeted in temperature, turning
into the freezing, hostile environments we know
today. And what happened to the life there? Well,
as a result of this sudden, in geological terms,
deep freeze, there was a mass extinction. The
vast majority of Tellios species, which are the
ray -finned fishes. Yes, the ray -finned fishes
that populated those waters simply couldn't withstand
the freezing temperatures. Their blood crystallized,
their populations were decimated. It was an icy
apocalypse for the fish down there, but not all
of them. No. A specific, seemingly unremarkable
suborder of fish called the notothenioids managed
to survive. And why do they survive? Because
by pure evolutionary chance, they had evolved
this precise genetic adaptation. the antifreeze
glycoprotein gene. Just a lucky roll of the genetic
dice. While the rest of the fish died off in
droves, the nototheneoids didn't just scrape
by, they thrived. They diversified. They evolved
into numerous different species and essentially
took over all the newly emptied ecological niches
left behind by the mass extinction. It's the
ultimate evolutionary success story. They basically
looked around and said, oh, the water is freezing
and everyone else is dead. Great. More real estate
for us. They inherited the entire bottom of the
world because of one genetic quirk. But here's
where the genetics get really, truly crazy. Our
notes highlight a mind -bending fact about convergent
evolution. This is one of my favorite examples.
We just talked about the Antarctic nototheneoids
down at the South Pole 30 million years ago.
Now, I want you to look all the way up at the
North Pole at a fish called the Arctic Northern
Cod. Right. These two groups of fish are separated
by the entire plant. They live in completely
different oceans. They diverged from each other
evolutionarily somewhere between 7 to 15 million
years ago. They are not closely related at all.
And yet... Scientists look at their blood and
they both have nearly identical antifreeze glycoproteins.
This is a textbook prime example of convergent
evolution. Two completely unrelated species separated
by thousands of miles facing the exact same brutal
environmental pressure. Freezing waters. Independently
arrive at the exact same biochemical solution.
It is nature finding the optimal answer to a
problem twice. But what is truly phenomenal,
and what had geneticists thrilling, is how they
arrived at that solution. They built the exact
same protein, but they used entirely different
genetic blueprints and raw materials to do it.
Alright, I was reading about where these genes
actually came from. So the Antarctic nautothenioids,
they evolved their antifreeze gene from a digestive
enzyme. The material specifically calls it an
ancestral pancreatic, trypsinogen -like, serine,
protease gene. Which is a very long way of saying
it was a gene responsible for making an enzyme
that breaks down food in the fish's pancreas.
Exactly. So somewhere along the line over millions
of years, a gene that was meant to help digest
a meal accidentally duplicated, mutated, and
somehow transformed into a gene that perfectly
stops ice from forming in the blood. That alone
is wild. But the northern cod in the Arctic.
their evolutionary path was entirely different
and much more recent. The sources say it happened
only about 3 .2 million years ago. And their
antifreeze gene didn't evolve from a pre -existing
working gene like a digestive enzyme? No. It
emerged from non -coding DNA. Non -coding DNA.
Which is what people sometimes colloquially call
junk DNA, right? Just the biological filler material
that doesn't seem to do anything. Exactly. It
was previously thought to be just evolutionary
baggage. But the COD's antifreeze protein emerged
via tandem duplications of a very short sequence
of this non -coding DNA. Specifically, a tiny
unit of amino acids. Thranningalaninealanine.
It just duplicated over and over, right out of
the dark, non -coding regions of the genome.
I saw a term in the material describing this,
the Proto -ORF model. I will be honest, I need
you to translate that into English for me, because
it sounds incredibly complex. It is a cutting
edge concept in genetics. ORF stands for open
reading frame. It is effectively a section of
DNA that has the potential to be read and translated
into a protein. The Proto -ORF model describes
a very rare occurrence where a new gene essentially
pre -exists as a fully formed, potentially useful
sequence in the non -coding DNA. It is just sitting
there in the dark, silent. Before the regulatory
elements, the genetic on switches even exists
to activate it. So it's like a fully built furnished
house sitting in the middle of nowhere, just
waiting for someone to finally run a power line
to it. That is a brilliant analogy. The house
is there, but the lights are off. And then boom.
a massive environmental pressure like a rapidly
cooling freezing ocean comes along. Through random
mutation, a regulatory switch is flipped, the
power line is connected, and this non -coding
junk DNA suddenly illuminates and becomes a highly
functional, life -saving protein. So the Cod
literally hacked its own junk DNA to survive
the freezing Arctic. I absolutely love that.
It's incredible. But if you think that hacking
your own DNA is wild, we have to talk about the
smelt. Because we just discussed convergent evolution,
where two animals invent the same thing independently.
But there's another evolutionary curveball in
the source material regarding a different type
of antifreeze. Type II AFPs. These are found
in three specific fish. The sea raven, the smelt,
and the herring. Now, the notes point out a statistical
impossibility. The smelt and the herring share
up to 98 % of the introns for this specific antifreeze
gene. Which, as you alluded to, is statistically
impossible to achieve through independent convergent
evolution. We need to define introns quickly.
Introns are the non -coding sections of an RNA
transcript. When a cell reads a gene to make
a protein, it makes a rough draft of RNA, and
then it literally splices out and throws away
the introns before the final protein is made.
They are the cutting room floor scraps of genetics.
Precisely. Now, for two widely divergent lineages
of fish, the smelt and the herring, to share
98 % of these highly specific, seemingly useless
cutting room floor sequences implies something
much, much more direct than convergent evolution.
The smelt didn't independently evolve this gene
over millions of years. The scientific consensus,
backed by undeniable genomic evidence, is that
the smelt actually stole it from the herring.
I'm sorry, I need to pause here. Yeah. They stole
a gene. Yes. Like a genetic heist. Yeah. How
does a fish steal a gene from another fish? It
is a phenomenon known as horizontal or lateral
gene transfer. We see it all the time in bacteria.
It's how they share antibiotic resistance so
quickly. But it is extremely, exceedingly rare
in complex vertebrates like fish. The theory,
which is heavily supported by the presence of
transposable elements. Basically jumping genes.
Exactly. Jumping genes in the smelt gene that
are otherwise uniquely characteristic of the
herring. The theory is that this transfer happened
during mating. Wait, herring and smelt don't
mate with each other, do they? No, but they do
spawn in the same freezing chaotic water columns.
It is believed that during spawning, smelt sperm
cells were somehow exposed to degraded or free
-floating foreign herring DNA in the water. Just
floating around. Through a microscopic stroke
of unimaginable statistical luck, a smelt sperm
cell absorbed that herring DNA, integrated the
antifreeze gene into its own payload, and then
successfully fertilized a smelt egg. That is
staggering. A microscopic sperm cell just bumps
into some floating genetic debris from a completely
different species, absorbs it, and suddenly the
entire subsequent lineage of smelt has a survival
superpower. They literally acquired it horizontally
across species lines. It totally upends the idea
of evolution being this slow branching tree.
It's more like a tangled web where sometimes
you just grab a power up from the guy swimming
next to you. It truly is a paradigm shifting
discovery in evolutionary biology. It shows how
opportunistic life can be. can be under extreme
pressure. Nature is absolutely wild. And just
to show you that, listen, the sheer diversity
of these proteins, the sources give us a roster
of different fish AFPs. We've talked deeply about
the glycoproteins. But there are four other completely
distinct structural types of antifreeze proteins
in fish. Let's run through them quickly, because
I want to give a sense of how many ways nature
solves this one problem. OK. First, there's type
I. This is found in the winter flounder and various
sculpins. The material notes that this is the
best documented one because it was the first
to have its 3D structure fully mapped out by
scientists. It looks like a single long amphipathic
alpha helix. Let's clarify that term amphipathic
because it is crucial to how these proteins work.
Amphipathic means the molecule has distinct faces
with entirely different properties. Imagine a
long cylinder. One side of the cylinder is highly
hydrophobic, meaning it actively repels water.
The opposite side is hydrophilic, meaning it
attracts water. Got it. And nestled within this
structure is a highly specific face made of threonine
and asparagine amino acids. This exact architectural
arrangement is what allows it to bind to ice,
which we will detail much more closely when we
look at the micromechanics. OK, so a two -faced
cylinder. Then you have type I hip. And hip simply
stands for hyperactive. found in right eye flounders.
And compared to the standard type I, it is a
massive molecule. The notes say it's about 32
kilodaltons, making it a dimeric molecule. Domeric
simply meaning it is composed of two identical
halves or monomers bound together. It operates
as a twin system. Right. And because of this
massive twin structure, it is incredibly effective
at depressing freezing temperatures. It has multiple
ice binding sites. It's like having an antifreeze
molecule with extra hands to grab onto the ice
crystal from multiple angles. Following that,
we have the type 3 AFPs, which are found in the
Antarctic eel pout. These are fascinating because,
similar to the digestive enzyme we discussed
earlier, they evolved from a completely different
functional gene. In this case, a sialic acid
synthase gene, or SAS. Through a complex gene
duplication event? This SAS gene actually lost
its N -terminal part. It basically lost a chunk
of itself. And the remaining fragment evolved
into a highly compact, globular, highly effective
antifreeze protein. It shows yet another completely
unique evolutionary pathway. And finally, type
4, found in longhorn sculpins. This one is an
alpha helical bundle. It's incredibly rich in
glutamate and glutamine amino acids. Just stepping
back for a second. In fish alone, we have at
least five completely distinct structural molecules.
Blycoproteins, type I cylinders, type I hyperactive
twins, type III globular fragments, and type
IV bundles. They all look completely different.
They all evolve completely independently. And
they're all designed to do the exact same thing.
Stop ice. It's a testament to evolutionary pressure.
But as we pivot away from the ocean, we learn
that the macrofauna, the big fish, are not the
only ones playing this high stakes game. We have
to look at the micro world. We have to look at
the microbes, the fungi, and the fascinating
paradox of plants. Let's start with the sea ice
ecosystem. When you look at a documentary about
the polar ice caps, the ice just looks like dead
frozen sterile water. But it's not. It is absolutely
teeming with life. Diatoms, which are a type
of microscopic algae absolutely dominate the
polar sea ice communities. Specifically, species
like Fragillaryopsis cylindrus. Yes, and these
diatoms possess AFPs that belong to a large complex
multi -gene family. They need them because they
actually live inside the tiny, brine -filled
channels within the sea ice itself. But what
is really intriguing about this specific family
of ice -binding proteins is that it isn't just
found in diatoms. The exact same homologs are
represented across wildly different unrelated
taxa. in the sea ice ecosystem. You find variations
of these ice binding proteins in psychrophilic
or cold loving bacteria. You find them in cold
tolerant fungi like the snow mold fungi that
survive under the winter pack snow. And wait,
I have to bring this up because it shocked me.
The notes say you even find them in edible mushrooms,
like the enoki and shiitake mushrooms. They absolutely
do. The enoki mushrooms I literally put in my
ramen last week have antifreeze proteins. They
do. It's how they survive sudden frosts in their
natural environments. Wow. And the fact that
we find this same family of proteins in diatoms,
bacteria, snow mold, and your dinner mushrooms
points to one of two things. What's that? Either...
There is a deeply ancient shared ancestral origin
for these proteins among all microorganisms dating
back hundreds of millions of years. Or... Or
we are looking at an incredibly vast complex
network of horizontal gene transfer. Like the
smell to the herring. Occurring constantly in
the microscopic sea ice community. The idea of
a global microscopic gene sharing network under
the ice is incredible. Okay, but my absolute
favorite microbe from the source material has
to be the ciliate consortium. This little single
-celled organism has an ice -binding protein
called AFC -IBP, and it is an absolute masterclass
in freeze tolerance. It is a perfect example
of what we discussed earlier. Remember our distinction
between freeze tolerance versus freeze avoidance.
The Euclid's Fecardiae protein doesn't focus
entirely on creating a massive thermal hysteresis
gap to prevent ice formation entirely. Instead,
it is exceptionally good at ice recrystallization
inhibition. It works efficiently all the way
down to a staggering negative 7 .4 degrees Celsius.
It allows the ice to form around it, but perfectly
manages the crystal size to prevent its single
cell from being punctured. And the science gets
even cooler. Researchers actually took the specific
gene for this Euclid's Focardianta freeze protein,
isolated it, and inserted it into the genome
of standard E. coli bacteria in a lab. And the
result? The newly modified E. coli survived significantly
longer periods at zero degrees Celsius. This
little single -celled ciliates genetic code is
so robust, so perfectly engineered by nature,
that you just plug it into a standard lab bacterium
like a software update and instantly upgrade
its cold resistance. Which, as you can imagine,
has massive implications for biotechnology and
synthetic biology, which we will certainly get
to. But first, we need to address the plants.
Because as the sources note, the classification
of AFPs became much, much more complicated in
the 1990s when antifreeze proteins were finally
discovered in plants, specifically in winter
rye leaves. The plant exception. So I'm picturing
a field of winter rye covered in snow. What makes
plant AFPs so fundamentally different from the
fish and the microbes we've been talking about?
What's fascinating here is that plant AFPs, which
are often classified by botanists as dehydrins,
operate on a slightly different biological paradigm.
First off, if you measure them, they exhibit
much weaker thermal hysteresis activity compared
to the hyperactive fish or insect AFPs. Their
primary physiological function isn't really to
prevent ice formation altogether. They know they're
going to freeze. They can't swim away to deeper,
warmer water. They're literally rooted in the
freezing ground. Exactly. They are entirely immobile.
So like the ciliate we just discussed, they are
heavily focused on managing the inevitable. They
inhibit the recrystallization of ice. They let
the water in their cellular spaces freeze, but
the dehydrants stop those ice crystals from growing
large enough to shred the plant's delicate vascular
system. They are the elegant managers of the
cold. They let the frost in, but they dictate
the terms. But the evolutionary origin of these
plant proteins is what really caught my eye in
the reading, because it's a completely different
origin story than the digestive enzymes of the
fish. It is a brilliant, highly resourceful pivot
by nature. Analysis shows that most plant AFPs
actually evolved from pathogenesis -related proteins.
Pathogenesis. Yeah. Meaning proteins that originally
evolved to fight off diseases. Precisely. They
originally evolved as defense mechanisms to fight
off fungal infections and other pathogens. And
what is truly remarkable, what makes it a biological
marvel, is that some of these plant antifreeze
proteins still retain their original antifungal
properties. They are pulling double duty. They
are protecting the plant from deadly, expanding
ice crystals in the dead of winter, while simultaneously
fighting off opportunistic fungal pathogens that
might try to take advantage of the stressed freezing
plant. It's a two -for -one survival tool, a
shield against both ice and disease. It is incredibly
elegant. but if plants are the elegant managers
of the gold, kinsects are the absolute biological
tanks. Here's where it gets really interesting.
You think a fish surviving at negative two degrees
Celsius is impressive. Our sources introduce
us to the spruce budworm. During the extreme
brutal winter months in northern forests, this
little moth larva resists freezing at temperatures
approaching negative 30 degrees Celsius. Just
for context, that is negative 22 degrees Fahrenheit.
It is unimaginably cold. To survive temperatures
that extreme, the proteins involved have to be
incredibly robust. Insect AFPs are generally
referred to in the literature as hyperactive.
They have a significantly greater thermal hysteresis
value than most fish AFPs. They have to because
the air temperatures they face are vastly colder
than any liquid ocean. Structurally, insect AFPs
are highly repetitive. They form a shape that
biochemists call a beta solenoid or a coil structure.
I was trying to visualize this. Imagine a tightly
wound spring, like from a mattress, but instead
of being perfectly round, one entire side of
the spring is completely flattened out. That
flat side is the ice binding surface. That is
a highly accurate visualization. And nature has
engineered several distinct variations of this
flattened coil across different species of bugs.
For instance, let's look at the tenebrio and
dendroids beetles. Their proteins are heavily
reinforced. They have internal disulfide bonds
that act like microscopic structural braces,
holding the coils rigidly together. And on that
flat ice -binding side of the coil, they have
a double row of an amino acid called threonine.
It's like armored plating. Very much so. But
then compare that to the rage their proteins
have even longer repeats. They don't rely on
those internal disulfide bonds for bracing. Instead,
they form what is called a compressed beta sandwich
structure. And instead of a double row, they
boast a formidable four rows of threonine residues
on their ice binding surface. They maximize the
contact area with the ice. And then you have
the midges, which use a structurally similar
solenoid coil. But their flat ice binding surface
consists of a single row of tyrosine residues
instead of threonine. It's exactly like looking
at different models of armored vehicles. They
all have the exact same goal, survive the battlefield
of winter. But the armor plating, the internal
bracing, the structural layout is arranged completely
differently depending on the specific evolutionary
path they took. But then I asked about the snow
fleas, because they are famous here in North
America, especially in Canada. You see them literally
hopping around on the surface of the snow on
relatively warm winter days. They aren't actually
true insects. They are springtails, which are
a type of primitive six -legged arthropod. And
their AFPs, despite living in the snow, are totally
different from the beetles, right? Completely
different. The similarity entirely ends at the
fact that they have a flat ice -binding surface.
The snow flea AFP is roughly 50 % composed of
the amino acid glycine. It doesn't form a beta
solenoid coil. Instead, it folds into a dense
bundle of what are called polyproline type 2
helices. And instead of using threonine or tyrosine
to bind to the ice like the beetles and midges,
its ice -binding face is dominated by small hydrophobic
residues like alanine. Again, convergent evolution.
A totally different genetic path, a totally different
molecular shape, but they still arise at a flat
surface that perfectly sticks to ice. But I want
to drop a bombshell from the sources right now.
Freeze you. Because we have spent this entire
deep dive talking about antifreeze proteins,
the P in AFP, amino acids folding into complex
shapes. But the Alaskan beetle... scientifically
known as upocereboids, has an antifreeze that
isn't even a protein at all. This was a landmark
discovery published in the Proceedings of the
National Academy of Sciences in 2009. It challenged
everything we thought we knew about cryobiology.
The Alaskan beetle produces a hyperactive antifreeze
molecule that is actually a non -protein polymer.
It is composed of saccharides and fatty acids.
It's a complex sugar polymer known as a xylomanin.
A sugar antifreeze. Exactly. It uses a chain
of sugars to do the exact same job as the complex
beta -solenoid proteins. It proves, unequivocally,
that nature found multiple, completely independent,
radically different biochemical pathways to fight
freezing. Evolution isn't restricted to just
rearranging amino acids into proteins. It can
literally build a highly effective, hyperactive
ice blocking shield out of complex sugars and
fats. That is staggering to me. It really makes
you wonder what else is out there in the extreme
environments of our planet that we simply haven't
discovered yet. What other bizarre molecular
combinations are keeping bugs alive in Siberia
or the deep Arctic? But whether it's a sugar
polymer like the xylomanin or a heavily armored
beta solenoid protein in a beetle or a microscopic
zipper in a flounder, it begs the ultimate mechanical
question. How does it physically work? How does
a tiny microscopic molecule actually grab onto
something as slippery, as rigid, and as dynamically
growing as an ice crystal? It all comes down
to a process that scientists call the adsorption
inhibition mechanism. To truly visualize this,
you have to understand how ice naturally grows
at a microscopic level. When water begins to
freeze in a solution, The water molecules slow
down and form a lattice. These nascent ice crystals
normally exhibit what crystallographers call
basal and prism faces. They tend to grow outward
as round, flat disks. Okay, so picture a microscopic,
dynamically growing Hockey puck. Exactly. The
hockey puck wants to keep expanding outward,
adding water molecules to its edges. What the
antifreeze proteins do is they target and adsorb,
meaning they physically adhere to the surface
of the non -basal planes of the ice crystal.
By attaching themselves to these specific structural
faces of the ice lattice, they create physical
roadblocks. They block the crystal from growing
in its thermodynamically favored direction. It's
like trying to build a brick wall and someone
keeps gluing unstackable steel plates randomly
onto your bricks. You just can't keep building.
But how do the proteins actually stick? Ice is
incredibly slippery. Because initially, according
to the sources, scientists thought it was all
about hydrogen bonding. Like the proteins were
tiny molecular magnets locking onto the oxygen
and hydrogen atoms in the water molecules of
the ice. That was indeed the prevailing, widely
accepted theory proposed by Raymond and de Vries,
the pioneer we mentioned earlier, back in 1977.
It made intuitive sense. However, biology and
physical chemistry are rarely that simple. Later
researchers decided to rigorously test this hydrogen
bonding theory by purposefully mutating the proteins
in the lab. They systematically altered or removed
the specific parts of the protein that were supposed
to be facilitating this magnetic -like hydrogen
bonding. If the 1977 theory held up perfectly,
the mutated proteins should have completely failed
to bind to the ice. They should have been useless.
But they weren't. The hypothesized massive decrease
in antifreeze activity was not observed. The
mutated proteins still stopped the ice. Which
means hydrogen bonding wasn't the main anchor
holding them there, so if it's not a magnetic
attraction, what is actually holding them to
this slippery ice? The current scientific consensus,
derived from decades of intense study, X -ray
crystallography, and advanced molecular modeling
programs, points to a highly complex mix of interactions.
Van der Waals forces, which are very weak, distance
-dependent intermolecular forces, play a significant
role. Along with that is surface complementarity.
Essentially, the physical shape of the protein
perfectly flawlessly matches the microscopic
physical topography of the ice crystal, locking
together like an impossibly complex puzzle piece.
But the primary driving force, the main contributor,
seems to be largely hydrophobic interactions.
Hyndrophobic meaning water repelling. So the
protein basically uses its water repelling side
to forcefully push away the liquid water in the
blood, which effectively forces its other flat
complementary side perfectly against the solid
ice matrix. Yes. And we can look back at the
type IAFPs from the winter flounder as a prime,
easily visualizable example of this micromechanic
in action. Because of its amphipathic, two -faced
structure, it acts quite literally like a microscopic
zipper. The hydroxyl groups of the critical threonine
residues on the flat side of the protein align
perfectly to bind to the oxygen atoms in the
ice lattice along a very specific directional
plane. It literally zips itself onto the ice
nucleation structure. Once zipped on, it creates
a rigid barrier, subsequently regarding the growth
of the pyramidal planes of the ice and depressing
the freeze point. A microscopic zipper driven
by water repulsion holding a growing ice crystal,
completely hostage. It's almost poetry. But our
sources also tell us that these biological zippers
don't always work entirely alone. Sometimes they
bring friends to the fight to make sure the ice
stays locked down. Yes, in the literature we
call these secondary molecules enhancers. In
beetles, for example, the highly hyperactive
antifreeze proteins are often accompanied by
other molecules circulating in their hemolymph,
their equivalent of blood. These include polycarboxylates,
specifically citrate and other compounds called
thomatin -like proteins. These enhancers interact
with the AFPs and dramatically, exponentially
increase their thermal hysteresis activity. They
act as an amplifier. They boost the signal of
the freeze protection. Exactly. And the biochemical
machinery involved in this whole process is incredibly,
unimaginably delicate. Researchers looked closely
at the dendroids beetle's highly evolved antifreeze
protein and in the lab they chemically modified
a single solitary amino acid. arginine. They
just tweaked one tiny part of the structure.
That one microscopic modification resulted in
the complete and total loss of the protein's
thermal hysteresis ability. It was instantly
rendered completely useless. It proves how highly
specific, how unimaginably fine -tuned this evolutionary
lock -and -key mechanism really is. You change
one tiny pin in the lock, the whole door just
flies open to the freezing cold. The beetle dies.
It's a game of absolute microscopic precision.
And speaking of fine -tuned mechanisms, I have
to mention a genuinely mind -bending study from
2010 that was detailed in our notes, because
we keep calling them anti -freeze proteins. But
scientists discovered that AFPs don't just inhibit
freezing, because they bind so stably, so perfectly
to the ice matrix, they can actually inhibit
melting. In a laboratory setting, they were able
to create superheated water ice crystals. They
created ice that physically stays solid at temperatures
where it should technically, thermodynamically,
be liquid water. Which is a phenomenal physical
feat. It perfectly illustrates why the scientific
community is shifting its terminology. These
proteins are not just simple anti -free solutes.
They are truly profoundly ice -structuring proteins.
They actively dictate and manipulate the structural
integrity of ice in both directions, preventing
it from forming when it should, and conversely,
preventing it from dismantling and melting when
it should. In that concept, the ability to physically
structure and control ice provides the perfect
transition to the final major area of our deep
dive today. Because once humanity discovers a
biological cheat code as powerful as this, we
are absolutely without a doubt going to figure
out how to harness it. First, let's talk about
that name change. There has been a significant
PR rebrand in the commercial space. You will
notice that food scientists and massive corporations
are pushing hard to rename AFPs to ice -structuring
proteins, or ISPs. Why? Because when average,
everyday consumers read the word antifreeze on
the back of their food packaging, their mind
immediately, understandably, goes to that toxic,
neon -essiling glycol in their car radiator.
Even though the biological proteins and the car
chemicals have absolutely nothing in common besides
their end goal of managing ice, the name antifreeze
is a complete nightmare for marketing. It is
a very necessary distinction for public understanding
and commercial acceptance because, as you alluded
to, the commercial applications of these proteins
are not some far -off sci -fi future. They're
already here, right now. So what does this all
mean for you? You might actually be eating these
highly evolved ice structuring proteins right
now. Indeed. The multinational consumer goods
company Unilever recognized the immense multi
-billion dollar potential of these ice structuring
proteins for the global food industry, specifically
the frozen dessert sector. Years ago, they underwent
rigorous testing and secured official approval
across the United States, the UK, the European
Union, China, Australia, and many other nations
to use these exact proteins in commercial ice
cream production. They utilize a highly specific
genetically modified yeast to safely produce
the exact same antifreeze proteins originally
found in those freezing deep sea fish. And they
put them directly into mass market products like
popular popsicles and the highly successful Breyers
light double turned ice cream bars. OK, but taking
a step back, why? Why on earth does my vanilla
ice cream need fish antifreeze in it? To solve
the absolute greatest enemy of the commercial
ice cream industry. temperature fluctuation.
Let's trace the journey of ice cream. When it
is manufactured, it is perfectly smooth. But
then it has to be transported. It might sit on
a slightly warm loading dock for 20 minutes.
It goes into a delivery truck. It goes into the
grocery store freezer, which goes through defrost
cycles. Then it goes into your grocery cart as
you walk around the store. Then it thaws slightly
on your kitchen counter before you finally put
it back into your home freezer. During every
single one of those slate temperature fluctuations,
the microscopic smooth ice crystals inside the
ice cream melt slightly and then refreeze. And
when they refreeze, they undergo that exact same
recrystallization process we talked about earlier
with the freeze -tolerant plants and bugs. Thermodynamics
forces those tiny crystals to fuse into larger,
jagged, crunchy ice crystals. Which completely
ruins the texture. It gets that weird icy, crunchy,
freezer -burnt texture that everyone hates. Exactly.
But by adding these ice structuring proteins
into the mix, Unilever completely controls the
ice crystal growth during those inevitable temperature
fluctuations. Just like in the freeze tolerant
organisms, the AFPs bind to the tiny ice crystals
the moment they start to refreeze, and they physically
stop them from growing larger. This structural
control allows Unilever to produce incredibly
dense, rich creamy and notably reduced fat ice
cream with far fewer artificial chemical additives
because the biological protein is doing all the
heavy lifting of maintaining the smooth microscopic
texture. It is brilliant engineering. Now whenever
we mention genetically modified yeast and the
insertion of fish genes into mass market food,
it is important that we impartially address the
concerns noted in our reading. There are anti
-GMO organizations and consumer advocacy groups
that have raised concerns suggesting that Introducing
these novel antifreeze proteins might cause inflammation
or allergic reactions in humans. It is a concern
that has been raised publicly, yes. However,
analyzing the data strictly from an objective,
toxicological, and historical standpoint, the
human intake of these specific AFPs in our diet
is already quite substantial and has been for
millennia. Historically, humans living in temperate
and northern regions have consumed these exact
proteins naturally for centuries. Every single
time they eat a cold -water fish, winter harvested
vegetables, or cold tolerant edible mushrooms.
Based on this extensive history of natural human
consumption, the overwhelming scientific and
regulatory consensus is that their functional
ice binding properties do not impart any toxicological
or allergenic effects on the human body. And
as for the transgenic yeast process itself, using
a modified yeast to brew the protein, the source
material is very clear that this is standard,
deeply established practice in the modern food
and medical industries. This is the exact identical
biotechnology used to produce modern insulin
for diabetics. It is the exact same process used
to produce the rennet that is used to make almost
all modern mass -produced cheese. You isolate
the specific gene you want, you insert it into
a fast -growing yeast, and you let the yeast
act as a microscopic brewery to safely, cleanly
produce the protein in massive vats. And from
an ecological and sustainability standpoint,
producing it in use is vastly, immeasurably superior.
It makes industrial production highly efficient
and more importantly, it absolutely prevents
the industry from having to harvest and kill
thousands, if not millions of deep sea fish just
to extract trace amounts of the protein from
their blood. It's a win -win. We save the ocean
ecosystems and we get perfectly smooth ice cream
that survives the trip home from the grocery
store. But perfecting the texture of dessert
is really just the tip of the iceberg, pun fully
unabashedly intended, because the future commercial
and medical applications currently being researched
are massive. We are looking at agricultural revolutions,
increasing the freeze tolerance of vital crop
plants to extend harvest seasons and protect
against devastating sudden frosts, improving
farm fish production in much colder climates
to ensure global food security, lengthening the
shelf life and nutritional integrity of frozen
foods worldwide. improving the pinpoint precision
of cryosurgery, where doctors use extreme cold
to target and destroy cancer cells. The agricultural
and surgical applications are incredible, but
then there are the absolute holy grails of cryomedicine.
We are talking about the ability to dramatically
enhance the preservation of human organs and
delicate tissues for transplants. Right now,
as you may know, the window to transport a donated
heart or liver is incredibly frustratingly short.
You cannot freeze a donor organ because the resulting
ice crystals will immediately rupture the cell
membranes and destroy the tissue beyond repair.
If we can master the use of synthesized AFPs
to safely freeze, transport, and then flawlessly
thaw human organs without cellular damage, it
would fundamentally revolutionize global transplant
medicine. Beyond that, there is active research
into advanced therapies for severe hypothermia
and potentially the ultimate most ambitious frontier
of all, human cryopreservation, often referred
to as cryonics. The theoretical ability to safely
freeze an entire human body, halt all biological
degradation, and revive it decades or centuries
later. without massive, irreversible cellular
damage. It sounds like pure science fiction,
the stuff of space operas and futuristic movies,
but the biological blueprint, the exact molecular
mechanism to make it happen, already exists.
It has been perfected. It is floating right now
in the blood of an Antarctic fish and the hemolymph
of an Alaskan beetle. To quickly recap the incredible
mind -expanding journey we've been on today,
we started with deep sea drilling cores revealing
a 30 million year old climate catastrophe, a
mass extinction that forcefully pushed surviving
fish to blindly evolve their own digestive enzymes
into a biological antifreeze. We learned about
smelt pulling off an impossible evolutionary
heist to steal survival DNA directly from herring.
We scaled all the way down to microscopic diatoms
and edible fungi surviving the brutal sea ice.
And we looked at heavily armored bugs that can
comfortably, casually survive negative 30 degrees
Celsius. We decoded the complex microscopic zipper
mechanisms and hydrophobic forces that physically
locked down expanding ice crystals. And finally,
We traced how all of this ancient evolutionary
brilliance has been captured by modern biotechnology
to keep your Breyers ice cream perfectly smooth.
It is a profound, humbling demonstration of nature's
relentless adaptability. But there is one final,
entirely unmentioned thread to pull from our
source material that I want to leave you with
today. Up until very recently, we were entirely
dependent on biological sources. But in 2021,
a breakthrough occurred. Scientists at the E
.P. Schofell in Switzerland and the University
of Warwick successfully created an entirely artificial
imitation of antifreeze proteins in the lab.
We are no longer strictly reliant on harvesting
or brewing nature's designs. Human science can
now actively synthesize these ice structuring
mechanisms from scratch. Furthermore, consider
the Alaskan beetle we discussed, the one that
completely bypassed proteins and uses a non -protein
sugar polymer, xylomanin, to easily survive the
freezing tundra. This convergence of synthetic
biology and non -protein cryoprotectants raises
a highly provocative question. If humans can
now artificially synthesize these complex ice
structuring mechanisms, and if nature has already
proven that you don't even need complex fragile
proteins to do it, what does this mean for the
future of human space exploration? Could we synthetically
adapt human biology or perhaps the delicate crops
we need to sustain us to comfortably survive
the deeply frozen hostile environments of Mars
or the icy radiation blasted moons of Jupiter
like Europa? Could an artificial mass synthesized
xylomanon be the key biological shield that eventually
protects the first human colonists from the lethal
sub -zero vacuum of deep space? That is an incredible
profound thought to end on. from a small fish
swimming in the dark freezing waters of an ancient
Antarctica to the very real potential for human
survival on the frozen surface of another planet.
Thank you so much for joining us on this deep
dive. I guarantee you are going to look at the
winter frost on your window and your next bowl
of vanilla ice cream in a completely different
light.