Scientists uncover a key chemical structure in pigment molecule

Newly revealed properties of melanin ‘ingredient’ could advance bioelectronics.

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Melanins are ubiquitous biopolymers produced from phenols and catechols by oxidation. They provide photoprotection, pigmentation, and redox activity to most life forms and inspire synthetic materials with desirable optical, electronic, and mechanical properties.

However, melanin’s chemical structures remain elusive, creating uncertainty about their roles and preventing the design of synthetic mimics with tailored properties. In the study, an international team of researchers isolated a key molecule involved in melanin synthesis.

Scientists studied a molecule that has several physical properties of eumelanin. In a laboratory, Melanin can be created naturally from a small number of straightforward chemical compounds that mix or react to make the colored substance. The team was able to effectively synthesize and examine one of its molecule-sized ingredients thanks to the work of Jean-Philip Lumb from McGill University and Lluis Blancafort from the University of Girona.

Even without further alterations, they discovered that it shared many characteristics with the finished product, Melanin.

Bern Kohler, an Ohio Eminent Scholar and professor of chemistry and biochemistry at The Ohio State University, said, “Melanin is like a complex dish that you cook from just a few ingredients. Since melanin granules in the skin contain billions of atoms, it was surprising to see melanin-like properties emerge in a molecule containing only a few dozen atoms.”

“As a spectroscopist – or a scientist who investigates the interactions between matter and light, what I found most remarkable is the brilliant green color of the melanin-like molecule, which can absorb deep red light.”

“That’s very hard for a small molecule to do. This is one of the smallest organic molecules known that can absorb long wavelengths out into the infrared.”

“Its unusual optical and magnetic properties make the melanin-mimicking molecule an attractive prospect for advancing bioelectronics research, a field that aims to connect electronics and living biological materials to fabricate new technologies or therapies for medical treatments.”

The study’s findings also imply that altering how humans obtain energy from their surroundings may be possible through the use of Melanin.

Kohler said“Like solar energy conversion, part of our strategy for alternative energy is to absorb photons of light from across the solar spectrum. That’s what eumelanin does, rather naturally.”

Future studies will focus on melanin-like characteristics in associated kinds of compounds. In the short term, Kohler believes the team’s discovery of a molecule that resembles Melanin will motivate other labs to focus more intently on how Melanin’s properties may emerge from other unexpectedly small molecular units. Such advancements could increase accessibility to synthetic biomaterial substitutes. 

Journal Reference:

  1. Wang, X., Kinziabulatova, L., Bortoli, M. et al. Indole-5,6-quinones display hallmark properties of eumelanin. Nat. Chem. (2023). DOI: 10.1038/s41557-023-01175-4

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