Name: Microscopy: Fluorescent Proteins (Roger Tsien)
Uploaded: 2017-04-15T18:19:05.000Z
Duration: 34 min 37 s
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And I'm here today to tell you about fluorescent proteins.

which have made a major impact on microscopy

provide a relatively direct link from molecular and cell biology

more macroscopic levels as well as eventually now

beginning to help us with super-resolution.

And in a way, this is the creature that we most have to thank.

we'll learn a little bit more about him soon.

This is the source of two of the most actually valuable proteins

First, there is the protein that actually enables this jellyfish to glow

when the jellyfish is alarmed in the water,

and the water is disturbed, it emits a glow.

green fluorescent protein, which changes the color from blue to green

to this day, we really don't have a well-accepted explanation

why should it show this remarkable phenomenon

nor do we know why when the jellyfish glows

why was it so important that it glows green instead of blue

why not just change aequorin in the first place to make it glow green directly

but we are very grateful to the jellyfish

So, the example - this is perhaps one of the only videos that we know of where we can show you the

And we are illuminating with ultraviolet light right now.

And you may be able to see that there's a circle here.

There are little dots around the edge; that is the jellyfish glowing.

And this is the green fluorescent protein naturally made by the jellyfish

I'm sorry the beaker is a bit fluorescent.

We should have got a better beaker that didn't have any,

But nevertheless, you can see the jellyfish there.

And it's upside-down and confined to this little beaker.

So we're gonna start here, and you may be able to see

that the jellyfish is slightly moving around.

In this video, we are playing with the illumination

trying to get it nicely aimed at the jellyfish,

and in a moment, we're going to bring in this rod, with which we are going to poke it.

Then we turn out the lights, and we stir.

And during that stirring, that was the light emitted by the jellyfish

- not the light that previously had been applied from a UV lamp.

And maybe, you might have been able to see

Anway, the man who discovered that phenomenon is shown here.

he published his first paper on aequorin.

And that was really the protein he was most interested in.

It had the really exciting job of turning chemical energy into light.

And he also mentioned that he found this contaminant

that got in the way a little bit of the purification

and that it was a greenish protein that fluoresced green

and that later he mentioned that it changed color of the jellyfish from the blue of aequorin to the green of GFP.

Later in 1979, he actually proposed the structure of the chromophore, GFP

but he got it almost absolutely, completely correct.

There were only very very small modifications from later work that came in.

This is a picture of him much later in 2008

That's the violet that's on your left, and then next to it is the tube of GFP.

And this is the last tube in existence that is actually made from real jellyfish that he had kept in his freezer all this time.

Since then, everything has been made by molecular biology

and that's due to this man, here, Douglas Prasher at the center

of the photograph who in 1992 published the cloning of the gene for GFP.

And that was a long struggle. He didn't know what to look for.

And he could not predict that it would become green fluorescent.

that there was no precedent for a protein that made by a biological organism would absorb blue light

We didn't know whether it needed any cofactors.

Normally, in many cases, when biology does this sort of remarkable thing,

with light, it uses small molecule cofactors.

you're seeing me, for example, not because the proteins in your eye directly

absorb the light through the protein, but rather,

because the proteins bind retinal, the pigment that we have

to get from other sources, and that binds into the protein to make the functional protein.

And for all we knew, the fear was that maybe this protein used another cofactor

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Microscopy: Fluorescent Proteins (Roger Tsien)

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