Research ArticleCELL BIOLOGY

Light-induced dynamic structural color by intracellular 3D photonic crystals in brown algae

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Science Advances  11 Apr 2018:
Vol. 4, no. 4, eaan8917
DOI: 10.1126/sciadv.aan8917
  • Fig. 1 Morphology and structural color of C. tamariscifolia.

    (A) C. tamariscifolia at collection site showing structural color. (B) Low-magnification (scale bar, 500 μm) image of a specimen with two different colors. Close-up of tips of blue (C) and green (D) specimens. Scale bars, 50 μm. (E and F) Single vesicles in the epidermal cells of two different specimens under a high-magnification optical microscope. Scale bars, 2 μm).

  • Fig. 2 Structure and composition of OPCs.

    (A) Cryo-SEM image of an epidermal cell. Scale bar, 2 μm. Arrows indicate OPC (solid) and chloroplast (dashed) positions within the cell. (B) Cross section of a single epidermal cell (TEM image). Scale bar, 2.5 μm. (C) Nanospheres in quasi–close-packed configuration. Scale bar, 1 μm. (D) False-color fluorescence confocal images of epidermal cells for chlorophyll (green) and Nile red lipophilic dye (red). Scale bar, 10 μm. (E) Sketch of position for OPCs (blue) and chloroplast (green) within the epidermal cells.

  • Fig. 3 Optical properties of OPCs.

    (A) In vivo normal-incidence reflectance measurements for three different OPCs (filled curves). Single-line curves correspond to simulations for an FCC lattice of spheres with φ = 186 (dotted), 204 (dashed), and 224 nm (dotted-dashed line). In all cases, nsph = 1.48 and ncyt = 1.35. The number of monolayers forming the opal was N = 18 (dotted and dash-dotted) and N = 17 (dashed). (B) Angular reflectance measurements for a single OPC. The dotted line shows calculation for the central reflectance wavelength of an opal using effective refractive index approximation φ = 200 nm. (C) Single-cell structural color decay under continuous local illumination. Images extracted from movie S2 at times 0, 9, and 40 s. Scale bars, 3 μm. (D) Reflectance decay of a single OPC under continuous illumination.

  • Fig. 4 Light-induced iridescence dynamics.

    (A) Stereomicrograph of C. tamariscifolia specimen in LC (top), after 12 hours in DC (middle), and return to LC (bottom) after illumination for 12 hours. (B) Details of the same specimen in (A) for DC (left) and LC (right) with dark/light adaptation periods of 12 hours, respectively. (C) Evolution of structural color intensity (IB/IRGB) during illumination and dark periods. Red and gray lines show continuous light and dark adaptation, respectively, for 24 hours. The solid blue line shows structural color for an illumination pattern with a duty cycle of LC 6 hours/DC 4 hours during 24 hours. Gray areas delimited by dotted lines highlight times where the illumination lamp is ON to trigger LC.

  • Fig. 5 Structural color decay by lattice expansion.

    (A) TEM images of a single vesicle used to study the lattice expansion under different conditions. (B) Statistical analysis (see fig. S9) of the distance between particles forming the OPCs for brown (LC) and blue (DC). Data suggest an expansion of the lattice for brown specimens. (C) Simulations of reflectance of an FCC lattice of spheres under different lattice expansions. d is the lattice parameter and Δd the lattice parameter expansion (d = do + Δd). do = √2φ, the case for which the spheres with diameter φ are close-packed. The blue-shadowed area shows reflectance calculated for a random distribution of the same spheres. All other parameters in the simulation are the same used in Fig. 3A.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/4/eaan8917/DC1

    fig. S1. High-magnification in vivo optical microscopy (115×) images of the epidermal region.

    fig. S2. Position of the OPCs and chloroplast in the epidermal cells.

    fig. S3. Energy-dispersive x-ray analysis over several epidermal cells containing OPCs.

    fig. S4. Statistical analysis of single OPC properties.

    fig. S5. Arrangement of the spheres within the OPCs.

    fig. S6. Relevant spectra and intensities for the light sources used in the experiments.

    fig. S7. Dynamics of structural color.

    fig. S8. Calculated reflectance of an OPC as a function of cytoplasm refractive index.

    fig. S9. Statistical analysis of lattice expansion on OPCs between dark and light conformation.

    fig. S10. Sketches of possible mechanism for light flux redirectioning into the chloroplast.

    movie S1. Three-dimensional autofluorescence confocal false-color maps showing the relative position between OPCs (red) and chloroplasts (green) within the epidermal cells.

    movie S2. Structural color decay for the two OPCs shown in Fig. 3C.

    movie S3. Structural color decay filmed with stereomicroscope under low magnification.

    movie S4. Fast decay of structural color for OPCs under continuous illumination.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. High-magnification in vivo optical microscopy (115×) images of the epidermal region.
    • fig. S2. Position of the OPCs and chloroplast in the epidermal cells.
    • fig. S3. Energy-dispersive x-ray analysis over several epidermal cells containing OPCs.
    • fig. S4. Statistical analysis of single OPC properties.
    • fig. S5. Arrangement of the spheres within the OPCs.
    • fig. S6. Relevant spectra and intensities for the light sources used in the experiments.
    • fig. S7. Dynamics of structural color.
    • fig. S8. Calculated reflectance of an OPC as a function of cytoplasm refractive index.
    • fig. S9. Statistical analysis of lattice expansion on OPCs between dark and light conformation.
    • fig. S10. Sketches of possible mechanism for light flux redirectioning into the chloroplast.
    • Legends for movies S1 to S4

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    Other Supplementary Material for this manuscript includes the following:

    • movie S1 (.avi format). Three-dimensional autofluorescence confocal false-color maps showing the relative position between OPCs (red) and chloroplasts (green) within the epidermal cells.
    • movie S2 (.avi format). Structural color decay for the two OPCs shown in Fig. 3C.
    • movie S3 (.avi format). Structural color decay filmed with stereomicroscope under low magnification.
    • movie S4 (.avi format). Fast decay of structural color for OPCs under continuous illumination.

    Files in this Data Supplement:

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