Fig. 5.

Light-switched, repeated swarming of MTs. a Reversible hydrogen bonding of photoresponsive DNA (p-DNA) by light-induced cis–trans isomerization of azobenzene. b Schematic of selective association and dissociation of p-DNA-conjugated MTs under UV and visible light irradiation, respectively. c Visible light (λ = 480 nm, I = 1.3 mW cm⁻²) induced isomerization of azobenzene from the cis to the trans form, which resulted in translational swarming of the p-DNA-conjugated rigid MTs with length of 4 ± 2 µm (average ± s.d.). The swarms were then exposed to UV light (λ = 365 nm, I = 0.4 mW cm⁻²) for 6 min that isomerized the azobenzene from the trans to the cis form. The swarms dissociated into single MTs within 12 min of the onset of photoirradiation. This cycle was repeated three times. Visible light irradiation to flexible MTs with length of 12 ± 1 µm (average ± s.d.) generated swarms with circular motion. d Changes in the association ratio upon repeated irradiation by visible and UV light. The concentration of red and green MTs was 0.6 µM each, and the conjugation ratio of p-DNA1 or p-DNA2 to MTs was ~100%. The concentration of kinesin was 0.8 µM. Scale bars: 20 µm. Error bar: s.e.m.