Nobel Prize in Chemistry for the year 2008 was awarded "for the discovery and development of the green fluorescent protein, GFP". Three scientists shared this prize: Osamu Shimomura, Martin Chalfie and Roger Tsien, and I was awestruck to learn the stories behind their discoveries.
Now, coming to the molecule, GFP is a fluorescent protein with it's emission maxima at 509nm, and has been one of the vastly used visual markers in molecular biology today.
Shimomura was one of the earliest to discover the significance of GFP when he was studying the bioluminescence property of jellyfish. Many of us would have observed a spectacular image of a glowing jellyfish, which is due to the emission of a specific kind of a protein expressed in these organisms. When Shimomura isolated the protein from the jellyfish, to his surprise, he observed that the proteins emitted blue light instead of green. Further studies showed that jellyfish contains another protein which absorbed the blue light and emitted green light, which led to its bioluminescence. This phenomenon is nothing but Forster's Resonance Energy Transfer (FRET), and I was trilled to know that jellyfish too makes use of it !
In 1988, Chalfie heard about GFP, and realized that it can be harnessed for in vivo bioimaging. He further came up with molecular biology methods to introduce GFP gene into the DNA of a small worm called C. elegans. His methods showed self expression of GFP by cells, and led to it's usage in imaging various organelles and organisms.
The real mechanism of the fluorescence emission was unveiled by Tsien. He showed a one to one correspondence with the structure and emission of GFPs. He further tweaked the structure of GFP to vary the emission maxima of the fluorescence, and thus engineered the emission mechanism. In time, his group also added further fluorescent molecules from other natural sources to the tag collection, which continues to expand.
I like to mention another key person who was involved in this discovery - Douglas C. Prasher. In fact, Prasher was the first to clone and sequence the gene of GFP, but unfortunately, he lost his tenure as a professor and could not continue his research on GFP. It was sad to know that he is now a courtesy shuttle-bus driver. It highlights that a so-called 'good system' can still err in making the right choice.
To conclude, in today's molecular biology, one cannot imagine the absence of fluorescent markers. It has now become integral part of biological research, and has led to deeper insights in understanding biology at the molecular scale. This prize was a celebration for basic science, and signifies the importance of analytical methods, and shows that revealing secrets of nature always leads to enlightenment.
Very intriguing post Pavan!! Ask any neuroscientist about GFP and it would be their one of the favorite molecule and so is mine, which I exploit this molecule routinely on fruit-flies brains in order to mapping specific neurons to specific behavior. Well there is no second thought that Douglas Prasher was the pioneer of such wonderful technique using GFP as tracer molecule. Two decades ago in 1987, he cloned the full length GFP gene and could express in an alien system and could demonstrate the fluorescence. This was such genius of Prasher that not only showed the full length gene had all the necessary information for the stabilization of protein in the heterologus system but also sparked the GFP revolution. He managed to show extremely small sized protein when tagged with GFP, can be seen under fluorescent microscope. It was such a huge leap for molecular biologist in the field of biological science where one could map the exact site of protein action by the virtue of a tagged light-bulb (GFP). This is what I’d say “COOL”. However the field has moved on, and now we’ve more fancy techniques such as “Brain-bow”, red- fluorescent protein (RFP), Yellow- fluorescent protein (YFP) to name a few. RFP—derived from a brilliant red sea anemone purchased in a Moscow pet shop—can reveal body tissues more vividly than other fluorescent proteins in use today. The Russian researchers who developed the new protein said it can render cancers and other target tissues easily visible in living animals, making them glow like Christmas bulbs.
ReplyDeleteWhereas, “Brain-bow” technique bows to scientist at Harvard University where a rainbow was created in the brain by inserting fluorescence genes from coral, jellyfish and bacteria, and making mice brain shine, revealing complex neuronal connections. Tracking neurons goes back to as early as 1873, by Camillo Golgi, the famous Italian physician, but it colors just a few neurons at a time, while as many as 90 various colors can be visualized through Brainbow at a time in brain cells. The following colorful paintings are amongst the most sophisticated pictures of neuronal connections ever obtained (See below). Furthermore, Brainbow exploits a similar scheme like color generation on a computer or TV screen, where a television monitor mixes red, green and blue to depict a wide array of colors, the combination of three or more fluorescent proteins in neurons can generate many different hues. Nonetheless, it reveals very interesting, and previously unrecognized, patterns of neuron arrangement and in author words “Instead of having a vision of just one cell within a circuit, you have a vision of the circuit itself."
Still, one needs million dollars worth scopes in order to use this technique and works only on genetically manipulated animals, which are major caveats in the field. It's not like the Golgi stain, where you can just look through a normal microscope. With the Golgi stain, you can do everything, including humans.
@ Shailesh, thanks a lot for those interesting and very knowledgeable comments...your views as working scientist indeed gives us better insights into this wonderful phenomenon...
ReplyDeleteGolgi stain sounds an interesting method...will look at it...
Nice post Pavan!..I had read the story of Prasher before but, had never wikied him..Somehow I feel sad with the shortsightedness of the system..Somehoe, I feel if we find some brilliant people, just let them be. Give them all facilities we can and give them atleast 10 years of time to prove themselves.still, if they are unable to prove, then may be take away the tenure position.Imagine Einstein being told to leave a university because he didn't publish for 5 years!!..thankfully, that didn't happen
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