Control of Bilayer Transport through a Photoswitchable Membrane-Stiffening Agent.

The mobility of proteins in the bilayer membrane is affected by (local) changes in lipid environment, which is important to their biological functioning. Artificial molecular systems that-to some extent-imitate tasks of membrane-embedded proteins are increasingly developed, however, they are usually controlled through responsive units in their core structure. Here we present an alternative approach based on an amphiphilic stiff-stilbene derivative that enables control of membrane fluidity by light.

Monodirectional Photocycle Drives Proton Translocation.

Photoisomerization of retinal is pivotal to ion translocation across the bacterial membrane and has served as an inspiration for the development of artificial molecular switches and machines. Light-driven synthetic systems in which a macrocyclic component transits along a nonsymmetric axle in a specific direction have been reported; however, unidirectional and repetitive translocation of protons has not been achieved. Herein, we describe a unique protonation-controlled isomerization behavior for hemi-indigo dyes bearing N-heterocycles, featuring intramolecular hydrogen bonds.

Artificial transmembrane signal transduction mediated by dynamic covalent chemistry.

Reversible formation of covalent adducts between a thiol and a membrane-anchored Michael acceptor has been used to control the activation of a caged enzyme encapsulated inside vesicles. A peptide substrate and papain, caged as the mixed disulfide with methane thiol, were encapsulated inside vesicles, which contained Michael acceptors embedded in the lipid bilayer. In the absence of the Michael acceptor, addition of thiols to the external aqueous solution did not activate the enzyme to any significant extent.

Push-Pull Stiff-Stilbene: Proton-Gated Visible-Light Photoswitching and Acid-Catalyzed Isomerization.

Donor-acceptor substituted stiff-stilbene is shown to undergo isomerization induced by visible light avoiding the need for harmful UV light. This visible-light photoswitching is inhibited by protonation of the dimethylamino-donor unit, disrupting the push-pull character and thus, gating of the photochromic properties is allowed by acid/base addition. Remarkably, the addition of a mild acid also triggers fast thermal back-isomerization, which is unprecedented for stiff-stilbene photoswitches usually having a very high energy barrier for this process.