Physicists at Jackson State University and Howard University are enlisting one of nature’s tiniest wonders in the fight against cancer.
What if fireflies could make rainbows? What if, in addition to dazzling us with their flickering green trails, they could light the night in red or bathe the sky in blue? There’s a scientific movement afoot to answer that very question. The ultimate goal, however, isn’t to turn the luminous bugs into Christmas-in-July light displays; it’s to develop a new weapon in the fight against cancer.
Jackson State University’s Jian-Ge Zhou and Wilbur Walters and Howard University’s Quinton Williams are a part of that effort. And with the help of sophisticated computational tools, they’ve now devised recipes that could allow luciferins—the molecules that give fireflies their fire—to emit in colors ranging everywhere from bluish green to orange.
Fireflies summon light from deep down in their bellies: Each burst is the result of a chain reaction that starts when a protein called luciferase latches onto to a comparatively tiny luciferin molecule. The color of the luciferin’s light burst depends not only on the makeup of the molecule itself but on the structure of the enveloping luciferase. In that respect, luciferins aren’t all that different from you and I: The way a person expresses herself depends not only on her personality (whether she’s shy or outgoing, silly or serious) but on who’s nearby (close friends, recent acquaintances, or perhaps a boss). Loosely speaking, the same goes for luciferins.
To alter the color of a luciferin’s burst, then, you can either modify the luciferin itself or modify the structure of the luciferase that surrounds it. The problem is, the effects of those modifications are hard to know in advance; testing the various scenarios experimentally would be a tedious process of trial and error.
So Zhou and company turned instead to simulations. Using a technique known as density functional theory, they simulated the effects of swapping out single atoms in a luciferin molecule—a carbon for a nitrogen here; a sulfur for an oxygen there, and so forth. They then determined how those luciferins behaved in the presence of different luciferases. They found that with relatively subtle tweaks, they could access entirely new parts of the color spectrum, including bluish-green, pure yellow, and orange.
That’s good news for the field of bioimaging, where luciferins have emerged as a promising tool. Red luciferins harvested from sea pansies and introduced into mice have been shown to emit bursts of light whenever a particular cancer-fighting drug, rapamycin, encounters its target. That behavior can potentially be harnessed to image tumors, assess the effectiveness of treatments, or both. But if such techniques are to gain wide usage, biologist will need a richer color palette at their disposal. They will, in a manner of speaking, need fireflies that can make rainbows. If the new simulations from Jackson State-Howard team are any indication, that dream may not be as farfetched as it sounds.
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