Name: ドリュー・ベリー - 驚くべき分子機械 (Drew Berry - Astonishing Molecular Machines)
Uploaded: 2021-01-14T05:30:48.000Z
Duration: 14 min 27 s
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What I am going to show you are the astonishing molecular machines that create the living

fabric of your body. Now, molecules are really, really tiny, and by tiny I mean really.

They're smaller than the wave length of light. We have no way to directly observe them,

but through science we do have a fairly good idea of what's going on down at the molecular scale.

But, so what we can do is actually tell you about the molecules but we don't really have

a direct way of showing you the molecules. One way around this is to draw pictures,

and this idea is actually nothing new,  scientists have always created pictures as part

of their thinking and discovery process. They draw pictures of what they are observing with their

eyes, through technology like telescopes and microscopes, and also what they are thinking

about in their minds. I've picked two well known examples because they both...

they're very well known for expressing science through art, and I start with Galileo, who used

the world's first telescope to look at the moon, and he transformed our understanding of the moon.

The perception of the 17th century was the moon was a perfect heavenly sphere, but

what Galileo saw was a rocky, barren world, which he expressed through his water colour painting.

Another scientist with very big ideas, the superstar of biology, is Charles Darwin,

with this famous entry in his note book.  He begins in the top left hand corner with I think,

and then sketches out the first tree of life, which is his perception of how all the species,

all living things on Earth, are connected through evolutionary history, the origin of

species through natural selection, and divergence from an ancestral population.

Even as a scientist, I used to go to lectures by molecular biologists and find them completely

incomprehensible, with all the fancy technical language and jargon that they would use in

describing their work, until I encountered the artworks of David Goodsell, who was a

molecular biologist at the Scripps Institute. And his pictures are all, everything is accurate,

it's all to scale, and his work illuminated for me what the molecular world inside us

is like. So in the top left hand corner you've got this yellow-green area, this is a transaction

through blood. The yellow-green areas is the fluids of blood which is mostly water,

but it is also antibodies, sugars, hormones,  that kind of thing, and the red region is a slice

into a red blood cell, and those red molecules are haemoglobin, they are actually red, that's

what gives blood its colour, and haemoglobin acts as a molecular sponge to soak up the

oxygen in your lungs and then carry it to other parts of the body. I was very much inspired

by this image many years ago, and I wondered whether we could use computer graphics to

represent the molecular world. What would it look like, and that's how I really began.

This is DNA in its classic double helix form, and it's from X-ray crystallography, so it's

an accurate model of DNA. If we unwind the double helix and unzip the two strands, you

see these things that look like teeth, those are the letters of genetic code, the 25,000

genes you've got written in your DNA.  This is what they typically talk about,

the genetic code, this is what they are talking about. But I want to talk about a different aspect

of DNA science, and that is the physical nature of DNA, and it's these two strands that run

in opposite directions, for reasons I can't go into right now, but they physically run

in opposite directions, which creates a number of complications for your living cells, as

you're about to see, most particularly when DNA is being copied. And so, what I am about

to show you is an accurate representation of the actual DNA replication machine that's

occurring right now inside your body, as at least 2002 biology. So DNA is entering the

production line from the left hand side, and it hits this collection, this miniature biochemical

machines that are pulling apart the DNA strands and making an exact copy. So DNA comes in

and hits this, this blue donut shaped structure, and it's ripped apart into its two strands.

One strand can be copied directly, and it can be seen spooling off, down to the bottom there,

but things aren't so simple for the other strand, because it must be copied backwards,

so it's thrown out repeatedly in these loops and copied, one section at a time, creating

two new DNA molecules. Now, you have billions of this machine, right now, whirring away

inside you, copying your DNA with exquisite fidelity. It's an accurate representation

and it is pretty much at the correct speed for what is occurring inside you.

I've left out error correction and a  bunch of other things.

This was work from a number of years ago...

Thank you, this was work from a number of years ago, but what I show you next is updated

science, it's updated technology. So again, we begin with DNA, and it's jiggling, wiggling

there because of the surrounding super molecules, which I've stripped away so you can see something.

DNA is about 2 nanometres across, which is really quite tiny, but in each one of your cells,

each strand of DNA is about 30-40 million nanometres long, so to keep the DNA organised,

to keep, ah, regulated access to the genetic code, it's wrapped around these purple proteins,

I've labelled them purple here, it's packaged up and bundled up. This is, all of this field

of view, is a single strand of DNA. This huge package of DNA is called a chromosome, and

I'll come back to chromosomes in a minute. We're pulling out, we're zooming out, out

through a nuclear pore, which is sort of the gateway to this compartment which holds all

the DNA called the nucleus. All of this field of view is about a semester's worth of biology

and I've got seven minutes, so we're not going to be able to do that today.

This is the way a living cell looks down a light microscope, and it's been filmed under

time lapse which is why you can see it moving. The nuclear envelope breaks down, the sausage

shaped things are the chromosomes, and we'll focus on them. They go through this very striking

motion that is focused on these little red spots. When the cell feels like it's ready

to go, it rips apart the chromosome. One set of DNA goes to one side, the other side gets

the other set of DNA, identical copies of DNA, and then the cell splits down the middle.

And again, you have billions of cells undergoing this process right now inside of you.

Now we're going to rewind and just focus on the chromosomes, and look at its structure and

describe it. So again, here we are at that equator moment. The chromosomes line up and

if we isolate just one chromosome, we're going to pull it out and have a look at its structure.

So this is one of the biggest molecular structures that you have, well at least as

far as we've discovered so far, inside of us. So this is a single chromosome, and you

have two strands of DNA in each chromosome, one is bundled up into one sausage, the other

strand is bundled up into the other sausage. These things that look like whiskers, that

are sticking out from either side are the dynamic scaffold in the cell, they're called

microtubules but their name is not so important, but what we're going to focus on is this

red region, I've labelled it red here, and it's the interface between the dynamic scaffolding

and the chromosomes. It is obviously central to the movement of the chromosomes. We have

no idea, really, as to how it's achieving that movement. We've been studying this thing

they call the kinetochore for over a hundred years, with intense study, and we are still

just beginning to discover what it's all about. It is made up of about 200 different

types of proteins, thousands of proteins in total. It is a signal broadcasting system.

It broadcasts through chemical signals, telling the rest of the cell when it's ready,

when it feels that everything is aligned and ready to go, for the separation of the chromosomes.

It is able to couple onto the growing and shrinking microtubules. It's transiently,

it's involved with the growing of the microtubules, and it's able to transiently couple onto them.

It's also a tension sensing system. It is able to feel when the cell is ready,

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ドリュー・ベリー - 驚くべき分子機械 (Drew Berry - Astonishing Molecular Machines)

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