Welcome back to the glowing chemistry series.
By the way, feel free to read the previous episode if you haven't !
- "Black or white? Putting colors together"
- "The glowing fluorescent chemistry and biology"
- "From Phosphorescence to Organic-LED (OLED)"
- "Light from candies - Triboluminescence"
- "The glow stick chemistry - Chemiluminescence"
- "The glowing organisms - Bioluminescence and the lucifer-ase"
- "The glowing mice - Bioluminescence in science application"
Last time we talked about introduction as well as the applications of bioluminescence in biomedical science, and we are going to continue with the Green fluorescent protein. If you haven’t check those post out, please click here and here to find out more.
[Established fluorescent proteins]
Image credits: King & May ]
Jelly fish glow in blue or green?
[GIF credits: JellyClubAdmin ]
Bioluminescence refers to light productions by living organism, which was usually a chemical reaction catalyzed by an enzyme call Luciferase. So it won't be too surprising that the true light emitter in the jelly fish Aequorea victoria is actually the aequorin, an enzyme that catalyse the luciferin oxidation upon the contact with calcium ions. Aequorin gives out chemiluminescence as blue light (~470 nm).
But in reality, the color we observed in the jelly fish Aequorea victoria is a bright green fluorescent (~ 508 nm) instead of blue, WHY ?
The green light observed in the jelly fish is actually emitted by the Green Fluorescent Protein (GFP) which we had introduced previously. But in the deep ocean, sun light could not penetrate too far, so GFP cannot use light from the sun as a light source and itself alone is not enough for the light emission. Meanwhile, jelly fish itself have not evolved to develop an efficient way to generate green light. But instead they have evolved to emitted green light in a more complicated way – involving the use of aequorin to generate the energy, and transfer the energy to GFP for green light emission.
By this way, jelly fish can generate green fluorescent even under dark environment, without the need of a external light source.
The famous Förster Resonance Energy Transfer (FRET)
The energy transfer process described is called the Förster Resonance Energy Transfer (FRET), and only occurred under certain circumstances.
[Redraw from: Claire M Brown ]
As described in the diagram,
a) It required the donor emission (aequorin) and acceptor excitation (GFP) to have a similar wavelength (color)
-- Where in terms of wavelength, the blue emission of aequorin and green excitation of GFP are similar. (emission spectra of aequorin overlaps with the excitation spectra of GFP)
b) Need to have both donor and acceptor in close proximity
-- As GFP is a companion protein to aequorin, aequorin is always close with GFP
c) Need to be in correct orientation
-- Here the proteins orientation between GFP and Aequorin is always fixed for light emission.
Importance of fluorescent protein
The discovery and development of GFP had greatly impacted the biology related research community, for its biological compatible light labeling features that can be used in different biological systems. Aside from GFP, scientists had developed other fluorescent proteins which their works were recognized by the awarding of the Nobel Prize in 2008 to the scientists which contribute heavily to this field.
[3D structure of GFP]
[GIF credits: Tomioka Lab ]
You may not have been benefit from this glowing protein directly, but many of the biological research works were done with the help of such protein!!
Hope you enjoy today's sharing.
Feel free to leave a comment and tell me what you think about it!
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