Tetsuo Nagano's group at Tokyo University does research on fluorescent pigments, to analyze the molecules in living cells. In the course of this research, the Group has developed a new red fluorescent pigment, called Tokyo Magenta.
"In terms of small organic molecules, most fluorescent pigments are fluorescein-based, and those all fluoresce green. Of course, all kinds of pigments have been made, with different wavelengths giving red, orange, or yellow. But fluorescein pigments are used because they have superior properties for bioscience research. They're highly soluble in water and have low toxicity. So, while that kind of green pigment is used often, useful fluorescent pigments with other colors haven't really been produced."Tokyo Magenta is based on a green fluorescein pigment developed previously by the Nagano Group. By replacing oxygen atoms with silicon, the excited states of the molecules have been changed, producing a red color. Because this pigment is structurally equivalent to the original fluorescein, pigments with two colors can be used together, to analyze the movement of multiple biological molecules in living cells.
"The first important thing we did was to give the red pigment a function. So this pigment fluoresces red when it detects an enzyme called β-galactosidase. By developing a pigment that targets a different molecule, we've achieved the ability to detect different substances that are produced by tumors, by dyeing cells with the two colors. We hope this will become a tool for diagnosing pathologically, from two angles, whether cancer is present or not."Also, because Tokyo Magenta fluoresces at a longer wavelength than the fluorescein, the light penetrates tissue more effectively. It's hoped that this will enable the discovery of biological molecules that haven't been visible before.
"From now on, we'd like to use this fluorescent substance to develop all kinds of fluorescent probes that can detect a variety of biological molecules. One thing we'd like to do is use this new approach to investigate complicated processes inside the body. Also, as I'm in the School of Pharmaceutical Sciences, I'd like to use this method to develop new diagnostic pharmaceuticals, something that leads to treatment. Such developments might be decades away, but I'd like to start working on them in the near future."
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