科学家发现皮肤色素和河流颜色物质之间隐藏的结构联系

Eumelanin, the brown-black pigment that darkens human skin, and natural organic matter (NOM), the substance that turns rivers, lakes, and soils amber and brown, would seem to have little in common. One is manufactured inside living cells to shield them from ultraviolet light. The other is the leftover residue of dead organisms, broken down over time by sunlight and microbes. Yet a new study from researchers at Ohio State University and Texas A&M University finds that these two materials behave almost identically when they absorb and re-emit light — and the explanation lies in nanoscale architecture so small it had gone largely unnoticed until now.

The study, published in ACS Central Science, proposes that both eumelanin and NOM are built from the same basic optical unit: stacks of just a few flat, ring-shaped molecules layered on top of one another like an extremely short stack of pancakes, only a few nanometers tall. According to the researchers, these “few-layered” stacks are the true light-absorbing and light-emitting components in both substances, regardless of the wildly different chemistry that produced them.

“Synthesizing the molecular building blocks in eumelanin and NOM is akin to two very different approaches for creating a diverse set of words,” said Bern Kohler, professor of chemistry and biochemistry at Ohio State and one of the study’s senior authors, in a university statement. “Melanin synthesis is like giving someone multiple copies of the alphabet and asking them to make words, while NOM synthesis is like using scissors to cut words out of books from a library.”

“This fundamental understanding of how eumelanin and NOM absorb and respond to light could ultimately help guide rational design of carbon-based materials,” Madhu said. “By bringing together two materials that have so far been studied separately, this work gives researchers a framework they can build on to understand related carbon materials.”

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