Fig. 2: Photoswitchable molecules used to functionalize phospholipids.

a Azobenzene consists of two benzene rings (red), linked via a nitrogen double bond (orange). In the trans form, it shows a planar structure. The cis form is characterized by a twisted geometry. Trans-to-cis switching is achieved with UV-A light of 365 nm and the back-switch from cis-to-trans with visible blue light of 465 nm or heat. b Hemithioindigo photoswitches consist of a thioindigo (red) and a stilbene part (orange). Photoisomerization from the thermodynamically stable Z state to the metastable E form is possible with purple light of >400 nm, while back-switching is achieved with green light of 500 nm or heat. Tables 1, 2 summarize photoswitchable phospholipids’ chemical structures and photoswitch positions.