What is the luminous principle of fluorescent protein?

In the ocean, there is a beautiful and magical creature-jellyfish. Jellyfish is an ancient aquatic invertebrate mollusk. Most jellyfish have colorful umbrellas and the ability of self-luminescence, which can emit a little light blue fluorescence, in contrast to the swaying seawater, which often makes people have infinite reverie. No one knows how the luminous ability of jellyfish evolved. These beautiful sea elves are scattered all over the world, dotted with the vast underwater world like stars. For millions of years, these beautiful jellyfish have appeared in the works of poets, painters and photographers like messengers of light, adding a touch of bright color to the history of human art.

▲ jellyfish Victoria jellyfish

Until the mid-20th century, a Japanese scientist, Shimomura Xiu, noticed and began to study the unique luminescence phenomenon of jellyfish, and found that its fluorescence came from a luminescent protein-jellyfish protein, which can emit blue fluorescence and transmit it to another green fluorescent protein, and finally make jellyfish produce green fluorescence. Subsequently, two scientists, martin chalfie and Qian Yongjian, transformed and utilized GFP, and formally introduced it into the whole life science field, which triggered a great revolution in the research technology of cells and protein in the life science field. So far, the method of labeling living cells with modified fluorescent protein has been widely promoted in laboratories all over the world, and Shimomura Xiu, martin chalfie and Qian Yongjian also won the 2008 Nobel Prize in chemistry for their great contributions. Next, we will gradually introduce the brilliant history of jellyfish and green fluorescent protein and the development of human science.

▲ In 2008, the Royal Swedish Academy awarded the Nobel Prize in Chemistry to Japanese scientist Shimomura Xiu (first from left), American scientist martin chalfie (middle) and Chinese-American scientist Qian Yongjian (third from left).

The discovery story of jellyfish protein

Shimomura was one of the first scientists to study the luminous phenomenon of this jellyfish. In 1950s, his Woods Hole Marine Biological Laboratory devoted itself to the study of bioluminescence. During the period of 1955- 196 1, Xiaxiu Village conducted an in-depth study on the luminescent mechanism of Cypridina, and found that this small creature needs a peculiar protein in its body to emit light, and named it luciferase. Unfortunately, Xia Xiucun found that luciferase alone is not enough to emit light-it was discovered many years later that luciferase itself has no luminous ability, but it can catalyze a small molecule compound called fluorescein to make it emit light-but this study made him realize that the luminous ability of many marine organisms may depend on some luminescent protein produced in their bodies. Therefore, he turned to study more marine life to find other protein with luminous ability.

Later, at the suggestion of his mentor Johnson, he finally decided to focus on a kind of research called Victoria jellyfish. To this end, he and Johnson drove to the Friday Harbor Laboratory of the University of Washington several times to salvage a large number of jellyfish, and brought them back to the laboratory in Massachusetts in batches for protein extraction experiments. The previous research on luciferase provided a lot of research experience for Shimomura. He soon discovered that a large number of luminous cells gathered at the edge of the umbrella area of jellyfish, and isolated a luminous protein, which he called "jellyfish protein". This study was published in 1962 Journal of Cell and Comparative Physiology.

It is said that one day, Shimomura took another sample of protein that failed to shine, poured it into the pool before going to work, turned off the light in the laboratory and prepared to go home. Before he left, he routinely looked around the laboratory for a week and was ready to lock the door. The next moment, he was surprised to find that the pool actually emits blue fluorescence! He immediately concluded that something in the pool may have activated the luminous ability of jellyfish protein. In the next few days, he screened all the possible ions and chemical components in the pool one by one, and finally found that calcium ions could activate the luminous ability of jellyfish protein.