Page 6 - Science Focus (issue 15)
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If you want to study the crucial proteins flashes” [2]. After noticing that this sink contained
related to cancer, aging, or Alzheimer’s disease, or seawater drained from his fish tanks, this meant
if you want to understand the neural developments that something within the seawater had allowed
in the brain…would you think of a jellyfish? for the remnants to emit light.
Most of you would say “No way! What do His research then made tremendous progress
jellyfishes have to do with us?” – after testing every component of seawater, he
identified that calcium was a crucial factor for the
In a way you are right, jellyfishes are extremely
different from humans, and won’t be affected by bioluminescence. From there, he narrowed down
the luminescent substance gradually to a single
many of our diseases.
protein which he called aequorin [2] – the protein
But they do have a unique feature – they give that emits blue light.
off a bioluminescent glow. This has intrigued
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scientists for decades – what exactly are the But this didn’t account for why the jellyfish would
substances within these jellyfishes that create this glow green. That’s when Shimomura hypothesized
effect? that there is another protein that coexists with
aequorin, and is responsible for absorbing the
This is the story of a marine biologist and higher-energy blue light, and using it to emit lower-
organic chemist, Osamu Shimomura. He has spent energy green light. Further experiments proved his
19 summers with his colleagues, collecting millions theory was correct. He narrowed down the source
of crystal jellyfishes, Aequorea victoria, from Friday of the green glow, and subsequently discovered
Harbor in Washington [1]. These jellyfishes had rings a fairly small but important protein – the green
of organs within their “umbrella” that generate fluorescent protein (GFP) [3].
green bioluminescence. However, isolating these
organs and studying how they worked proved to Another breakthrough came in 1987, when
be challenging. Shimomura attempted multiple American microbiologist, Douglas Prasher, studied
extraction methods and conditions, but many in detail the DNA and protein sequence of GFP.
He proposed that GFP could be used to tag
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were to no avail.
proteins, by taking advantage of the genetics
In one summer afternoon in 1961, Shimomura and protein production in a cell [4]. This would be
tested if a change in pH would affect the a more practical way to study proteins, as most
bioluminescent glow. Some pH levels triggered proteins are colorless and too small to be seen with
only a faint glow but not the intense glow he was microscopy techniques directly. If GFP could be
looking for. Towards the end of the day, he tossed linked to a target protein, followed by excitation
the remains of his unsuccessful experiment into with high-energy light, the target protein could
a nearby sink, and that was when he saw the be tracked within a cell by detecting the green
inside of the sink being lit up with “bright blue fluorescence signal.
