EosFP consists of 226 amino acids.  It has a molecular mass of 25.8 kDa and its pI is 6.9.  Eos has 84% identical residues to Kaede, a fluorescent protein that originated in a different scleractinian coral Trachyphyllia geoffroyi, but can also be irreversibly converted from a green to red emitting form using UV light. Excluding residues Phe-61 and His-62, the chromophore environment and chromophore itself are unaffected by photochemical modification. Wild-type EosFP has a tetrameric arrangement of subunits where each subunit has the same β-can structure as GFP.  This structure includes an 11-stranded barrel and, down the central axis, the fluorophore-containing helix.