Tracking the formation of eumelanin from L-Dopa using coupled measurements

Yip, Philip and Sutter, Jens U (2018) Tracking the formation of eumelanin from L-Dopa using coupled measurements. Methods and Applications in Fluorescence, 6. 027001. ISSN 2050-6120 (https://doi.org/10.1088/2050-6120/aa9724)

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Abstract

Melanin plays a crucial role as a pigment all through the animal kingdom. Being a macromolecule just on the divide between an ordered crystalline or a purely amorphous form melanin has proven a challenge to structure-function analysis. Melanin assembles from small molecules much like a jigsaw and much like in a jigsaw the fine detail quickly vanishes in the overall picture. With melanin being first and foremost a photo-active molecule we focus on spectral properties for the characterisation of its structure. We use absorption measurements to illustrate the complex nature of the formation process. To gain a better hold on the formation pathway we use coupled measurements of excitation and emission to identify 'areas of interest' in the excitation-emission matrix (EEM). We then probe one area for characteristic fluorescence lifetimes to track one melanin building block through the formation process. Comparison of the EEMs of L-Dopa derived melanin with natural Sepia melanin shows characteristic differences. We show how the presence of copper ions creates a melanin closer to its natural form.

ORCID iDs

Yip, Philip ORCID logoORCID: https://orcid.org/0000-0003-2725-7474 and Sutter, Jens U ORCID logoORCID: https://orcid.org/0000-0002-3782-6338;