Structure Prediction from Melanin Spectra amidst Dynamical Heterogeneity

Melanin is a biopolymer pigment that plays a central role in skin photoprotection. Its extensive chemical and dynamical heterogeneity impart this property through a broad featureless ultraviolet/visible absorption spectrum. Conventionally, the ra- tional design of synthetic photoprotective pigments revolves around establishing the structure-spectra correlation and developing biomimetic materials with desired optical properties. This approach fails to explain the mechanistic details of melanin’s absorption spectrum because it arises from an ensemble of structures rather than a local minimum on the potential energy surface. Here, we propose an inverse design approach to establish a correlation between melanin’s electronic spectrum in various wavelength domains and the structures in a thermal ensemble. Our study elucidates the contributions of dominant chromophore units and structural motifs to different regions of the broad spectrum of melanin.