ALISON SWEENEY: There is a vast literature on vertebrate lens
biochemistry.
We've got this whole sort of messy gemisch
of proteins in there.
But a squid lens is infinitely more elegant than our eye.
The resolution of their eyes is approaching that of humans.
And their retinas are much more sensitive
than ours are to light.
And when you dig into the nitty gritty of how nature figured it
out, I'm forever blown away at the level of nuance
to get it to work.
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My name is Alison Sweeney.
And I study the evolution of novel materials in nature.
Organisms are made of stuff.
A tree is made of wood, and a human
is made of skin, and bones, and muscles.
So we can think of these things as materials
the way engineers do and ask the question,
how did they get that way over the course of evolution?
And if you were a Martian who swooped down and scooped up
exactly one animal off of Earth, you
are more likely than not to get something
transparent and bioluminescent that
came from 400 meters in the ocean
because that's where 99% of the space is.
And if you were really interested in how does it work,
probably you should be studying animals from the deep ocean.
So midwater squid just hang out in this pretty darn empty void.
Far as you're concerned, life on Earth
is this infinite, three-dimensional, featureless,
watery realm, which means that there's not a lot of structure
other than the light itself.
People are often surprised to learn how much light
is actually down there.
So at 400 meters depth, there is as much light at noon
as there is on a full moon night on land.
If you're a squid that's been evolving for 400 million years
to live at that depth, you can see great.
You probably have as much visual perception
as we do at noon because their eyes are much more sensitive.
One of the things that makes squid eyes as sensitive as they
are is the design of their lens.
If you want to be more sensitive to light,
you want to bend light as quickly
as you can to your retinas.
So you focus as much light as possible
on a given spot on the retina as you can.
To do that, you want a really bendy, powerful lens,
but you don't get a very crisp image out of a spherical lens.
Squids have figured out how to fix this
by making the lens denser at the center
and less dense at the edge so that you
get a completely crisp image at every point on the retina.
It's really sort of a neat trick to find a way to put proteins
together in a whole bunch of different densities,
such that none of them are going to require any energy
to maintain that structure.
And they will never coagulate over
the lifetime of the animal.
A lens is literally made of S-crystallins.
All of the stuff in there is S-crystallin protein.
Everybody thought that you just had
sort of a bunch of these dissolved in solution.
And the thing that made them weird
was that they never broke, and they never aggregated.
So we got squid.
And we pulled their lenses out.
And then we stuck squid lens tissue in a vacuum chamber
that is situated in the middle of an X-ray flight tube.
The X-ray source sends a beam of X-rays through your sample.
When the X-rays hit the sample, they're going to scatter off.
And the pattern of X-rays that we observe on the detector
tells us what the structure of the sample
is before the X-rays.
What we saw was a squid lens genuinely self-assembles
into this really cool higher order
complex optical structure.
So self-assembly is this concept that I
would like to figure out how to make a Lego castle,
that if I had a bunch of little bricks, put it into a bag,
and shake the bag, the castle will just come out again.
That's essentially what the squid lens proteins do.
It's non-trivial to make these things.
If we knew how to make a little lens that built itself out
of basically free materials, we would do that.
We don't know how to do that.
And the beauty of evolution is you don't
have to know what you're doing.
You just have to keep changing it until it works.
So by studying how the evolutionary process has found
self-assembly that works, basically
we can leverage 400 million years
of iterative learning to show us how to make shortcuts
at the engineering bench.
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