Fungal melanins differ in planar stacking distances.

Area of Science:

• Biophysics
• Materials Science
• Mycology

Background:

• Melanins are challenging to study due to their amorphous and insoluble nature.
• Limited structural techniques exist for analyzing melanin.
• Current models propose stacked planar structures, often analyzed by X-ray diffraction.

Purpose of the Study:

• To structurally characterize fungal melanins using X-ray diffraction.
• To compare the inferred stacking parameters of different fungal melanins.
• To investigate the universal structural features of melanins.

Main Methods:

• X-ray diffraction analysis of melanins isolated from Cryptococcus neoformans, Aspergillus niger, Wangiella dermatitides, and Coprinus comatus.
• Comparison of diffraction parameters with synthetic melanin and neuromelanin.
• Exclusion of capsular polysaccharide interference in Cryptococcus neoformans analysis.

Main Results:

• Fungal melanins exhibit inferred stacking distances intermediate between synthetic melanin and neuromelanin.
• A broad non-Bragg feature was observed in the capsular polysaccharide of C. neoformans, suggesting gel organization.
• The stacking peak appears to be a universal feature distinguishing melanins.

Conclusions:

• Fungal melanins possess unique stacking distances compared to other melanin types.
• All melanins likely share a fundamental diffracting unit of planar graphitic assemblies.
• The stacking peak is a potential characteristic feature for melanin identification and characterization.