Evaluating the “Darkness” of Melanin Materials.

We developed a mathematical process to quantify the apparent darkness of solutions containing melanin-like materials. The visible portion of their UV-Vis spectra is model using an exponential equation. Linear regression analysis provides the constants that define this exponential equation. Using these constants, the exponential equation is integrated between 400nm to 900nm to obtain the area-under-the-curve (AUC) of the visible portion of the UV-Vis spectra. This process was applied to data collected from various melanin-like materials discussed in earlier reports. By comparing the AUC values of different samples one can readily compare the “darkness” of melanins and evaluate the impact varying reaction conditions may have on this physical property. We revisited the results of earlier reports and discuss additional points related to the UV-protective properties attributed to melanins.