Researchers have reported the atomic resolution structure of DsRed (Nat. Struct. Biol. 7, 1133– 1138, 2000), a red fluorescing homolog of green fluorescent protein (GFP) originally isolated from Discosoma coral (Nat. Biotechnol. 17, 969– 973, 1999). Unlike monomeric GFP, four monomers of DsRed self associate at two chemically distinct surfaces to form a tight tetramer in solution and in the crystal structure. According to Mark Wall, the paper's first author, each subunit shows GFP's characteristic paint in a can fold of eleven β strands surrounding a central α-helix, which bears the chromophore generated by cyclization and oxidation of residues Gln66-Tyr67-Gly68. Remarkably, an oxidized bond flattens the main chain of Gln66 extending π bonding of the chromophore and contributing to the far red emission spectrum of the protein. Also, cis peptide bond formation between Phe65 and Gln66 in the chromophore appears important to position the oxidized main chain of Gln66 in-plane with the chromophore and is likely to slow the maturation of DsRed's fluorescence emission spectrum from faint to intense red, which can take up to 48 h. While optimizing DsRed so that fluorescence maturation is faster may be challenging, Wall and coauthors believe the “structural information will allow protein engineers to alter chromophore tuning and oligomeization of DsRed,” making the protein more applicable for use in single and double fluorescent-label studies.