WEBVTT

00:00:06.019 --> 00:00:09.192
It's so obvious 
that it's practically proverbial.

00:00:09.192 --> 00:00:12.094
You can't unboil an egg.

00:00:12.094 --> 00:00:15.509
Well, it turns out you can, sort of.

00:00:15.509 --> 00:00:18.291
What thermal energy 
does to the eggs' molecules,

00:00:18.291 --> 00:00:21.481
mechanical energy can undo.

00:00:21.481 --> 00:00:24.338
Eggs are mostly made 
of water and proteins.

00:00:24.338 --> 00:00:28.032
The proteins start off 
folded up into intricate shapes,

00:00:28.032 --> 00:00:31.006
held together by weak chemical bonds.

00:00:31.006 --> 00:00:33.596
Adding heat disrupts those bonds,

00:00:33.596 --> 00:00:39.630
allowing the proteins to unfold,
uncoil, unwind and wiggle freely.

00:00:39.630 --> 00:00:42.671
This process is called denaturing.

00:00:42.671 --> 00:00:45.820
The newly liberated proteins 
bump up against their neighbors

00:00:45.820 --> 00:00:48.807
and start to form 
new bonds with each other,

00:00:48.807 --> 00:00:51.074
more and more as the heat increases,

00:00:51.074 --> 00:00:56.254
until finally, they're so entangled
that they gel into a solid mass,

00:00:56.254 --> 00:00:58.183
a boiled egg.

00:00:58.183 --> 00:01:01.648
That entanglement might look 
permanent, but it's not.

00:01:01.648 --> 00:01:03.521
According to a chemical idea

00:01:03.521 --> 00:01:06.793
called the principle 
of microscopic reversibility,

00:01:06.793 --> 00:01:10.093
anything that happens, 
like egg proteins seizing up,

00:01:10.093 --> 00:01:14.564
can theoretically unhappen
if you retrace your steps.

00:01:14.564 --> 00:01:17.836
But adding more heat will tangle
the proteins further,

00:01:17.836 --> 00:01:20.718
and cooling them down
will only freeze them,

00:01:20.718 --> 00:01:22.322
so here's the trick:

00:01:22.322 --> 00:01:25.273
spin them around ridiculously fast.

00:01:25.273 --> 00:01:26.717
I'm not kidding.

00:01:26.717 --> 00:01:28.198
Here's how it works.

00:01:28.198 --> 00:01:31.853
First, scientists dissolve 
boiled egg whites in water

00:01:31.853 --> 00:01:33.953
with a chemical called urea,

00:01:33.953 --> 00:01:38.957
a small molecule that acts as a lubricant,
coating the proteins' long strands

00:01:38.957 --> 00:01:42.685
and making it easier for them 
to glide past each other.

00:01:42.685 --> 00:01:45.924
Then, they spin that solution 
in a glass tube

00:01:45.924 --> 00:01:49.229
at a breakneck 5000 rotations per minute,

00:01:49.229 --> 00:01:52.640
making the solution 
spread out into a thin film.

00:01:52.640 --> 00:01:54.187
Here's the key part.

00:01:54.187 --> 00:01:57.232
The solution nearest
the wall spins faster

00:01:57.232 --> 00:01:59.575
than the solution closer to the middle.

00:01:59.575 --> 00:02:03.171
That difference in velocity 
creates sheer stresses

00:02:03.171 --> 00:02:06.831
that repeatedly stretch 
and contract the proteins

00:02:06.831 --> 00:02:12.911
until eventually they snap back
into their native shapes and stay there.

00:02:12.911 --> 00:02:15.156
By the time the centrifuge stops spinning,

00:02:15.156 --> 00:02:20.230
the egg white is back 
in its original unboiled state.

00:02:20.230 --> 00:02:23.055
This technique works 
with all sorts of proteins.

00:02:23.055 --> 00:02:27.194
Bigger, messier proteins can be
more resistant to being pulled apart,

00:02:27.194 --> 00:02:31.042
so scientists attach 
a plastic bead to one end

00:02:31.042 --> 00:02:35.897
that adds extra stress
and encourages it to fold up first.

00:02:35.897 --> 00:02:40.104
This unboiling method won't work
with a whole egg in its shell

00:02:40.104 --> 00:02:44.276
since the solution has to spread
throughout a cylindrical chamber.

00:02:44.276 --> 00:02:48.867
But the applications go way beyond
uncooking your breakfast, anyhow.

00:02:48.867 --> 00:02:53.751
Many pharmaceuticals consist of proteins
that are extremely expensive to produce,

00:02:53.751 --> 00:02:57.223
partly because they get stuck 
in tangled up aggregates,

00:02:57.223 --> 00:02:59.179
just like cooked egg whites

00:02:59.179 --> 00:03:03.828
and have to be untangled and refolded
before they can do their jobs.

00:03:03.828 --> 00:03:06.143
This spinning technique has the potential

00:03:06.143 --> 00:03:09.201
to be an easier, cheaper 
and quicker method

00:03:09.201 --> 00:03:11.574
than other ways to refold proteins,

00:03:11.574 --> 00:03:16.102
so it may allow new drugs to be made
available to more people faster.

00:03:16.102 --> 00:03:18.550
And there's one more thing 
you need to keep in mind

00:03:18.550 --> 00:03:21.271
before trying to uncook all of your food.

00:03:21.271 --> 00:03:25.025
Boiling an egg is actually
an unusual cooking process

00:03:25.025 --> 00:03:29.848
because even though it changes the way
proteins are shaped and bound together,

00:03:29.848 --> 00:03:33.154
it doesn't actually change 
their chemical identity.

00:03:33.154 --> 00:03:36.999
Most types of cooking are more like
the famous Maillard reaction,

00:03:36.999 --> 00:03:38.996
which makes chemical changes

00:03:38.996 --> 00:03:43.720
that turn sugars and proteins
into delicious caramel crunchiness

00:03:43.720 --> 00:03:46.516
and are a lot harder to undo.

00:03:46.516 --> 00:03:48.983
So you might be able to unboil your egg,

00:03:48.983 --> 00:03:53.165
but I'm sorry to say 
you can't unfry it...yet.