1
00:00:06,019 --> 00:00:09,192
It's so obvious 
that it's practically proverbial.

2
00:00:09,192 --> 00:00:12,094
You can't unboil an egg.

3
00:00:12,094 --> 00:00:15,509
Well, it turns out you can, sort of.

4
00:00:15,509 --> 00:00:18,291
What thermal energy 
does to the eggs' molecules,

5
00:00:18,291 --> 00:00:21,481
mechanical energy can undo.

6
00:00:21,481 --> 00:00:24,338
Eggs are mostly made 
of water and proteins.

7
00:00:24,338 --> 00:00:28,032
The proteins start off 
folded up into intricate shapes,

8
00:00:28,032 --> 00:00:31,006
held together by weak chemical bonds.

9
00:00:31,006 --> 00:00:33,596
Adding heat disrupts those bonds,

10
00:00:33,596 --> 00:00:39,630
allowing the proteins to unfold,
uncoil, unwind and wiggle freely.

11
00:00:39,630 --> 00:00:42,671
This process is called denaturing.

12
00:00:42,671 --> 00:00:45,820
The newly liberated proteins 
bump up against their neighbors

13
00:00:45,820 --> 00:00:48,807
and start to form 
new bonds with each other,

14
00:00:48,807 --> 00:00:51,074
more and more as the heat increases,

15
00:00:51,074 --> 00:00:56,254
until finally, they're so entangled
that they gel into a solid mass,

16
00:00:56,254 --> 00:00:58,183
a boiled egg.

17
00:00:58,183 --> 00:01:01,648
That entanglement might look 
permanent, but it's not.

18
00:01:01,648 --> 00:01:03,521
According to a chemical idea

19
00:01:03,521 --> 00:01:06,793
called the principle 
of microscopic reversibility,

20
00:01:06,793 --> 00:01:10,093
anything that happens, 
like egg proteins seizing up,

21
00:01:10,093 --> 00:01:14,564
can theoretically unhappen
if you retrace your steps.

22
00:01:14,564 --> 00:01:17,836
But adding more heat will tangle
the proteins further,

23
00:01:17,836 --> 00:01:20,718
and cooling them down
will only freeze them,

24
00:01:20,718 --> 00:01:22,322
so here's the trick:

25
00:01:22,322 --> 00:01:25,273
spin them around ridiculously fast.

26
00:01:25,273 --> 00:01:26,717
I'm not kidding.

27
00:01:26,717 --> 00:01:28,198
Here's how it works.

28
00:01:28,198 --> 00:01:31,853
First, scientists dissolve 
boiled egg whites in water

29
00:01:31,853 --> 00:01:33,953
with a chemical called urea,

30
00:01:33,953 --> 00:01:38,957
a small molecule that acts as a lubricant,
coating the proteins' long strands

31
00:01:38,957 --> 00:01:42,685
and making it easier for them 
to glide past each other.

32
00:01:42,685 --> 00:01:45,924
Then, they spin that solution 
in a glass tube

33
00:01:45,924 --> 00:01:49,229
at a breakneck 5000 rotations per minute,

34
00:01:49,229 --> 00:01:52,640
making the solution 
spread out into a thin film.

35
00:01:52,640 --> 00:01:54,187
Here's the key part.

36
00:01:54,187 --> 00:01:57,232
The solution nearest
the wall spins faster

37
00:01:57,232 --> 00:01:59,575
than the solution closer to the middle.

38
00:01:59,575 --> 00:02:03,171
That difference in velocity 
creates sheer stresses

39
00:02:03,171 --> 00:02:06,831
that repeatedly stretch 
and contract the proteins

40
00:02:06,831 --> 00:02:12,911
until eventually they snap back
into their native shapes and stay there.

41
00:02:12,911 --> 00:02:15,156
By the time the centrifuge stops spinning,

42
00:02:15,156 --> 00:02:20,230
the egg white is back 
in its original unboiled state.

43
00:02:20,230 --> 00:02:23,055
This technique works 
with all sorts of proteins.

44
00:02:23,055 --> 00:02:27,194
Bigger, messier proteins can be
more resistant to being pulled apart,

45
00:02:27,194 --> 00:02:31,042
so scientists attach 
a plastic bead to one end

46
00:02:31,042 --> 00:02:35,897
that adds extra stress
and encourages it to fold up first.

47
00:02:35,897 --> 00:02:40,104
This unboiling method won't work
with a whole egg in its shell

48
00:02:40,104 --> 00:02:44,276
since the solution has to spread
throughout a cylindrical chamber.

49
00:02:44,276 --> 00:02:48,867
But the applications go way beyond
uncooking your breakfast, anyhow.

50
00:02:48,867 --> 00:02:53,751
Many pharmaceuticals consist of proteins
that are extremely expensive to produce,

51
00:02:53,751 --> 00:02:57,223
partly because they get stuck 
in tangled up aggregates,

52
00:02:57,223 --> 00:02:59,179
just like cooked egg whites

53
00:02:59,179 --> 00:03:03,828
and have to be untangled and refolded
before they can do their jobs.

54
00:03:03,828 --> 00:03:06,143
This spinning technique has the potential

55
00:03:06,143 --> 00:03:09,201
to be an easier, cheaper 
and quicker method

56
00:03:09,201 --> 00:03:11,574
than other ways to refold proteins,

57
00:03:11,574 --> 00:03:16,102
so it may allow new drugs to be made
available to more people faster.

58
00:03:16,102 --> 00:03:18,550
And there's one more thing 
you need to keep in mind

59
00:03:18,550 --> 00:03:21,271
before trying to uncook all of your food.

60
00:03:21,271 --> 00:03:25,025
Boiling an egg is actually
an unusual cooking process

61
00:03:25,025 --> 00:03:29,848
because even though it changes the way
proteins are shaped and bound together,

62
00:03:29,848 --> 00:03:33,154
it doesn't actually change 
their chemical identity.

63
00:03:33,154 --> 00:03:36,999
Most types of cooking are more like
the famous Maillard reaction,

64
00:03:36,999 --> 00:03:38,996
which makes chemical changes

65
00:03:38,996 --> 00:03:43,720
that turn sugars and proteins
into delicious caramel crunchiness

66
00:03:43,720 --> 00:03:46,516
and are a lot harder to undo.

67
00:03:46,516 --> 00:03:48,983
So you might be able to unboil your egg,

68
00:03:48,983 --> 00:03:53,165
but I'm sorry to say 
you can't unfry it...yet.