Fig. 1: Photostable properties of jellyfish-derived fluorescent protein StayGold.

a–c, Natural fluorescence of C. uchidae. Fluorescent polyps on a shell of N. livescens; the shell is ellipsoidal and measures approximately 1.5 cm by 1.0 cm (a). Fluorescence images of an isolated polyp (b) and a female medusa (c) superimposed on differential interference contrast images. Scale bars, 0.5 mm. d, Normalized excitation (dotted line) and emission (solid line) spectra of a tissue homogenate prepared from C. uchidae medusae. e, Amino acid sequence alignments of CU17S, StayGold, EGFP and DsRed. Residues whose side chains form the interior of the β-barrel are shaded (EGFP and DsRed). Asterisks: residues responsible for chromophore synthesis. The V168A mutation is indicated in red. f, Absorption spectra of CU17S (dotted line) and StayGold (solid line), normalized against the peak at 280 nm. g, Normalized excitation (dotted line) and emission (solid line) spectra of CU17S and StayGold. h, i, Photostability of green-emitting FPs under continuous WF illumination (5.6 W cm⁻²). Plotted as measured intensity versus time (top) or as intensity versus normalized total exposure time with an initial emission rate of 1,000 photons/s/molecule (bottom). h, Purified protein (1 μM) in polyacrylamide gel. The data are shared with Fig. 2b. i, Expressed in human (HeLa) cells in HBSS. j, k, Fluorescence images of StayGold-expressing and mNeonGreen-expressing (j) or EGFP-expressing (k) cells (stable HeLa cell transformants) at the indicated times (minutes:seconds). Illumination intensity: 16 W cm⁻². The gray scale indicates the lowest and highest intensities of the image. Scale bars, 20 μm. See Supplementary Video 1. l, log–log plot of bleaching half-time (Y) of StayGold (solid circles) or EGFP (open circles) and irradiance (X). Data were fitted to the equation log(Y) = −αlog(X) + c. α values were 0.90 and 0.96 for StayGold and EGFP, respectively. m, Chromophore maturation of StayGold (solid circles) and mNeonGreen (open circles) after cDNA transfection. Fluorescence intensity divided by the transfected cell occupation area was plotted every 6 hours and normalized to the maximum value. Data points are shown as means ± s.e.m. (n = 4 different experiments).