The molecule is a dicarboxylic acid dianion obtained by deprotonation of the carboxy groups of (3E)-phycoerythrobilin; major species at pH 7.3. It is a dicarboxylic acid dianion and a linear tetrapyrrole anion. It is a conjugate base of a (3E)-phycoerythrobilin.
3-[(2Z,5Z)-2-[[3-(2-carboxylatoethyl)-5-[[(2R)-4-ethenyl-3-methyl-5-oxo-1,2-dihydropyrrol-2-yl]methyl]-4-methyl-1H-pyrrol-2-yl]methylidene]-5-[[(3E,4R)-3-ethylidene-4-methyl-5-oxopyrrol-2-yl]methylidene]-4-methylpyrrol-3-yl]propanoate