Figure 2. Photo-isomerization of caCers affects membrane fluidity and lipid domain structure in supported lipid bilayers.

(a) Confocal fluorescence microscopy of SLBs containing a quaternary mixture of DOPC:cholesterol:SM:caCer (10:6.7:5:5 mol ratio) and 0.1 mol% ATTO655-DOPE. Images of SLBs prepared with dark-adapted trans-caCer-3 and trans-caCer-4 revealed phase separation, with taller liquid-ordered (L_o) domains appearing as dark regions in a liquid-disordered (L_d) phase. Scale bars, 10 μm. (b) Atomic force microscopy of SLBs prepared as in (a). Isomerization of caCer-3 (top) and caCer-4 (bottom) to cis with UV-A light (365 nm) resulted in a fluidification inside the L_o domains, as indicated by the appearance of small fluid L_d lakes and an increased L_d/L_o area ratio. This effect was reversed on isomerization back to trans with blue light (470 nm), marked by a drop in the L_d/L_o area ratio. Scale bars, 2 μm. (c) Time-course plotting the normalized L_o area over multiple 365/470 nm irradiation cycles for caCer-3 (top) and caCer-4 (bottom).

Figure 2—video 1. Reversible remodeling of lipid domains by caCer-3.

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DOI: 10.7554/eLife.43230.008

A DOPC:Chol:SM:caCer-3 (10:6.7:5:5 mol ratio) lipid mixture was recorded using high-speed AFM (height images). The isomerization to cis-caCer-3 is marked with a pink circle; isomerization back to trans-caCer-3 is marked with a blue circle. Scale bar = 500 nm. Acquisition = 1.5 s/frame. Video frame rate = 13 fps.

Figure 2—video 2. Reversible remodeling of lipid domains by caCer-4.

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DOI: 10.7554/eLife.43230.009

A DOPC:Chol:SM:caCer-4 (10:6.7:5:5 mol ratio) lipid mixture was recorded using high-speed AFM (error images). The isomerization to cis-caCer-4 is marked with a pink circle; isomerization back to trans-ACe-1 is marked with a blue circle. Scale bar = 500 nm. Acquisition = 1.5 s/frame. Video frame rate = 13 fps.