Fig. 5: Mechanical actions using microflow of DNA condensates.
From: Remote-controlled mechanical and directional motions of photoswitchable DNA condensates
a Schematic of mechanical action of state-transitioning DNA upon non-photoresponsive DNA. b Summary table of (c, e, g) generated flow modes and their observed temperature ranges for different insertion sites of Azo in the SE. Dissolving temperature TD for the corresponding SEs (Fig. 3) are also related. c, d “Spread” mode due to UV-induced fast diffusion. c Upon UV irradiation, photoresponsive (Yi) DNA favors a fast gel-to-dissociated state transition, leading to a fast spread of non-photoresponsive Y0 DNA in the outward direction. i = 2x1x5, 3x5, 1x7. d (Top) Merged fluorescence and (bottom) PC images of a Y2x1x5/L0/Y0 condensate captured (leftmost) before and (rightmost) after UV irradiation at 30°C. (Middle) Time-sequential fluorescence images of spreading Y0 particles in response to UV irradiation. e, f “Collapse” mode due to a UV-induced gel-to-liquid state transition. e Upon UV irradiation, Yi condensate shows a gel-to-liquid state transition, resulting in a collapse of Y0 gel particles. i = 1x7. f Merged fluorescence and PC images of a Y1x7/L0/Y0 condensate captured (leftmost) before and (rightmost) after UV irradiation at 45°C. (Middle) Time-sequential fluorescence images of collapsing Y0 particles in UV irradiation. g, h “Spread and collect” mode in alternating UV/Vis irradiation. g Initially, Yi and Y0 condensates coexist in a condensate as a liquid state. Upon UV irradiation, a Yi liquid condensate shows “spread” behavior due to a liquid-to-dissociated state transition and releases Y0 condensates; upon switching to Vis irradiation, the dissociated Yi shows reversing flow due to Vis-induced reassociation of SEs, and collects the released Y0 condensates. h Merged fluorescence and PC images of a Y3x5/L0/Y0 condensate captured (top leftmost) before UV, (rightmost) after UV, and (bottom leftmost) after additional Vis irradiation at 55°C. Time-sequential fluorescence images of (top middle, left-to-right) spreading Y0 condensates under UV irradiation and (bottom, right-to-left) their collection after switching to Vis. Yellow dashed-line curves mark the advancing periphery of the condensate as an eye guide. Irradiation intensities: (UV, 360–370 nm) 3.3 mW cm–2; (Vis) 7.0 mW cm–2 (460–495 nm for FAM), 4.8 mW cm–2 (520–550 nm for Cy3). Scale bars: 50 µm.
