Unlocking the molecular structure of fungal melanin using 13C biosynthetic labeling and solid-state NMR

Shiying Tian, Javier Garcia-Rivera, Bin Yan, Arturo Casadevall, Ruth E. Stark

Research output: Contribution to journalArticle

Abstract

Melanins are enigmatic pigments found in all biological kingdoms that are associated with a variety of functions, including microbial virulence. Despite being ubiquitous in nature, melanin pigments have long resisted atomic-level structural examination because of their insolubility and amorphous organization. Cryptococcus neoformans is a human pathogenic fungus that melanizes only when provided with exogenous substrate, thus offering a unique system for exploring questions related to melanin structure at the molecular level. We have exploited the requirement for exogenous substrate in melanin synthesis as well as the capabilities of high-resolution solid-state nuclear magnetic resonance (NMR) to establish the predominantly aliphatic composition of L-dopa melanin and to introduce 13C labels that permit the identification of proximal carbons in the developing biopolymer. By swelling solid melanin samples in organic solvents and using two-dimensional heteronuclear NMR in conjunction with magic-angle spinning, we have identified chemical bonding patterns typical of alkane, alkene, alcohol, ketone, ester, and indole functional groups. These findings demonstrate the feasibility of a novel approach to determining the structure of melanin using metabolic labeling and NMR spectroscopy.

Original languageEnglish (US)
Pages (from-to)8105-8109
Number of pages5
JournalBiochemistry
Volume42
Issue number27
DOIs
StatePublished - Jul 15 2003
Externally publishedYes

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ASJC Scopus subject areas

  • Biochemistry

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