File S1 - Melanin from the Nitrogen-Fixing Bacterium Azotobacter chroococcum: A Spectroscopic Characterization

Supporting figures. Figure S1, UV-VIS absorption spectrum of the dark brown compound(s) obtained from Azotobacter chroococcum in NaOH. Figure S2, FTIR spectrum (in KBr pellet under complete dry condition in nitrogen atmosphere) obtained from synthetic melanin purchased from SIGMA ALDRICH. Figure S3, a) Calculated 13C-NMR chemical shift values using the Chem Ultra software for 5,6-dihydroxyindole and its tautomer b) Calculated 13C-NMR chemical shift values using the Chem Ultra software for 5,6-dihydroxyindole-2-carboxylic acid and its tautomer, Figure S4, Calculated 13C-NMR chemical shift values using the Chem Ultra software for the proposed putative structure(s) of the protomolecules of melanin hetero-polymers obtained from the nitrogen-fixing soil bacterium Azotobacter chroococcum. (DOC)