Research ArticleMICROROBOTS

Micrometer-sized molecular robot changes its shape in response to signal molecules

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Science Robotics  01 Mar 2017:
Vol. 2, Issue 4, eaal3735
DOI: 10.1126/scirobotics.aal3735
  • Fig. 1 Design and microscopic images of amoeba-like molecular robots.

    (A) Overall schematics of the robots in the inactive (a) and active (b) states; magnified schematics of the liposomal membrane when kinesins are detached from (c) or attached to (d) the membrane; and schematics of the clutch mechanism (e and f). The arrows in (b) and (d) indicate the driving force of the kinesin motor. (B and C) Phase-contrast microscopy images of the robots and fluorescence images of microtubules in the inactive (B) and active states (C). The white arrowheads in (C) indicate microtubules on the membrane. Scale bars, 10 μm.

  • Fig. 2 Analysis of continuous shape change in inactive and active robots.

    (A and B) Schematics of a robot and the clutch in the inactive (A) and active state (B). (C) Image sequences of a robot in the inactive state, as visualized by a laser scanning confocal microscope: Green and magenta show kinesins and microtubules, respectively. Scale bar, 20 μm. (D) Color map of r/rmax of the inactive robot shown in (C): The radius was defined as the distance from the center of mass to the periphery, as shown in the image at t = 900 s; the gray arrowheads on the right side of the color map indicate the times at which the images shown in (C) were captured. (E) Image sequences of a robot in the active state visualized by laser scanning confocal microscope: The white arrowheads in the images at t = 100 and 700 s indicate microtubules on the membrane. Scale bar, 20 μm. (F) Color map of r/rmax of the active robot shown in (E): The values were measured using the same method as that in (D); the gray arrowheads on the right side of the color map indicate the times at which the images shown in (E) were captured.

  • Fig. 3 Switching shape change of individual robot.

    (A and B) Schematics of switching mechanism using prDNA signals: from inactive to active (A) and from active to inactive (B). (C) Robot image sequences show transition from inactive to active, as visualized by a laser scanning confocal microscope; the connector prDNA signal was input at t = 300 s; the white arrowhead at t = 770 s indicates the microtubule attachment on the membrane. Scale bar, 10 μm. (D) Color map of r/rmax of the inactive robot shown in (C): The values were obtained using the same method described in Fig. 2D; the gray arrowheads on the right side of the color map indicate the times of the images shown in (C). (E) Robot image sequences show the transition from active to inactive; the releaser prDNA signal was also input at t = 300 s, and the white arrowhead at t = 60 s indicates the microtubule attachment on the membrane. Scale bar, 10 μm. (F) Color map of r/rmax of the robot shown in (E); the gray arrowheads on the right side of the color map indicate the times at which the images shown in (F) were captured.

  • Fig. 4 SD of the radius of the robot.

    (A) Inactive and active states of the robots shown in Fig. 2 (C and E). (B) Switching from inactive to active and from active to inactive states of the robots shown in Fig. 3 (C and E). Bold lines in (A) and (B) indicate the average values of 10 frame images.

Supplementary Materials

  • robotics.sciencemag.org/cgi/content/full/2/4/eaal3735/DC1

    Fig. S1. Single cholesterol–modified anchor encapsulated in the liposome.

    Fig. S2. Flow chart of preparation methods for inner and outer solutions of one sample.

    Fig. S3. Confocal images under the condition of 0 mM ATP.

    Fig. S4. Signal responsiveness of robot and clutch function confirmed by premixing DNA signals.

    Fig. S5. Polyacrylamide gel electrophoresis.

    Fig. S6. Statistical mean values of r/rmax in active and inactive robots under a field of microscopic view.

    Fig. S7. Confocal microscopic images of the liposomes under the condition of DOPC/cholesterol/DSPE-PEG2000 = 8.9/1/0.1.

    Fig. S8. Confocal microscopic images of the liposomes under the condition of DOPC/cholesterol/DSPE-PEG2000 = 8/1.9/0.1.

    Fig. S9. Atomic force microscopy images of the lipid bilayer membrane on a mica surface.

    Fig. S10. Structural formula of a photocleavage site denoted by -X- in table S1.

    Fig. S11. Switching function of clutch induced by prDNA signals.

    Fig. S12. Measurement of DNA strand displacement in giant liposome.

    Fig. S13. Variation in energy required for shape change (ΔE) as a function of time.

    Fig. S14. Transition from active to inactive states of robot without DNA signal.

    Fig. S15. Microtubule protrusions from robot.

    Table S1. DNA sequences.

    Table S2. Final concentration of each chemical species in inner and outer solutions for robot.

    Movie S1. Continuous shape change in robot with clutch engaged.

    Movie S2. Switching of the shape of the robot from inactive to active states using photoresponsive connector DNA signal.

    Movie S3. Switching of the shape of the robot from active to inactive states using a photoresponsive releaser DNA signal.

    Movie S4. Rotational 3D view of robot with microtubule protrusions.

    Movie S5. Shape-changing behavior in robots after freezing and thawing.

    References (5355)

  • Supplementary Materials

    Supplementary Material for:

    Micrometer-sized molecular robot changes its shape in response to signal molecules

    Yusuke Sato, Yuichi Hiratsuka, Ibuki Kawamata, Satoshi Murata, Shin-ichiro M. Nomura*

    *Corresponding author. Email: nomura{at}molbot.mech.tohoku.ac.jp

    Published 1 March 2017, Sci. Robot. 2, eaal3735 (2017)
    DOI: 10.1126/scirobotics.aal3735

    This PDF file includes:

    • Fig. S1. Single cholesterol–modified anchor encapsulated in the liposome.
    • Fig. S2. Flow chart of preparation methods for inner and outer solutions of one sample.
    • Fig. S3. Confocal images under the condition of 0 mM ATP.
    • Fig. S4. Signal responsiveness of robot and clutch function confirmed by premixing DNA signals.
    • Fig. S5. Polyacrylamide gel electrophoresis.
    • Fig. S6. Statistical mean values of r/rmax in active and inactive robots under a field of microscopic view.
    • Fig. S7. Confocal microscopic images of the liposomes under the condition of DOPC/cholesterol/DSPE-PEG2000 = 8.9/1/0.1.
    • Fig. S8. Confocal microscopic images of the liposomes under the condition of DOPC/cholesterol/DSPE-PEG2000 = 8/1.9/0.1.
    • Fig. S9. Atomic force microscopy images of the lipid bilayer membrane on a mica surface.
    • Fig. S10. Structural formula of a photocleavage site denoted by -X- in table S1.
    • Fig. S11. Switching function of clutch induced by prDNA signals.
    • Fig. S12. Measurement of DNA strand displacement in giant liposome.
    • Fig. S13. Variation in energy required for shape change (ΔE) as a function of time.
    • Fig. S14. Transition from active to inactive states of robot without DNA signal.
    • Fig. S15. Microtubule protrusions from robot.
    • Table S1. DNA sequences.
    • Table S2. Final concentration of each chemical species in inner and outer solutions for robot.
    • Legends for movies S1 to S5
    • References (5355)

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Continuous shape change in robot with clutch engaged.
    • Movie S2 (.mp4 format). Switching of the shape of the robot from inactive to active states using photoresponsive connector DNA signal.
    • Movie S3 (.mp4 format). Switching of the shape of the robot from active to inactive states using a photoresponsive releaser DNA signal.
    • Movie S4 (.mp4 format). Rotational 3D view of robot with microtubule protrusions.
    • Movie S5 (.mp4 format). Shape-changing behavior in robots after freezing and thawing.

    Files in this Data Supplement: