Lichtgesteuerte Proteinbindung einer biologisch relevanten β-Faltblattstruktur

Spatio-temporal control of cellular uptake achieved by photoswitchable cell-penetrating peptides

A thermostable azobenzene building block serves as a switch for activating cell-penetrating peptides with excellent spatio-temporal control.

Optical Control of Insulin Secretion Using an Incretin Switch

Incretin mimetics are set to become a mainstay of type 2 diabetes treatment. By acting on the pancreas and brain, they potentiate insulin secretion and induce weight loss to preserve normoglycemia. Despite this, incretin therapy has been associated with off-target effects, including nausea and gastrointestinal disturbance. A novel photoswitchable incretin mimetic based upon the specific glucagon-like peptide-1 receptor (GLP-1R) agonist liraglutide was designed, synthesized, and tested. This peptidic compound, termed LirAzo, possesses an azobenzene photoresponsive element, affording isomer-biased GLP-1R signaling as a result of differential activation of second messenger pathways in response to light. While the trans isomer primarily engages calcium influx, the cis isomer favors cAMP generation. LirAzo thus allows optical control of insulin secretion and cell survival.

Genetically encoding photoswitchable click amino acids in Escherichia coli and mammalian cells

The ability to reversibly control protein structure and function with light would offer high spatiotemporal resolution for investigating biological processes. To confer photoresponsiveness on general proteins, we genetically incorporated a set of photoswitchable click amino acids (PSCaas), which contain both a reversible photoswitch and an additional click functional group for further modifications. Orthogonal tRNA-synthetases were evolved to genetically encode PSCaas bearing azobenzene with an alkene, keto, or benzyl chloride group in E. coli and in mammalian cells. After incorporation into calmodulin, the benzyl chloride PSCaa spontaneously generated a covalent protein bridge by reacting with a nearby cysteine residue through proximity-enabled bioreactivity. The resultant azobenzene bridge isomerized in response to light, thereby changing the conformation of calmodulin. These genetically encodable PSCaas will prove valuable for engineering photoswitchable bridges into proteins for reversible optogenetic regulation.

Light-controlled tools

Spatial and temporal control over chemical and biological processes plays a key role in life, where the whole is often much more than the sum of its parts. Quite trivially, the molecules of a cell do not form a living system if they are only arranged in a random fashion. If we want to understand these relationships and especially the problems arising from malfunction, tools are necessary that allow us to design sophisticated experiments that address these questions. Highly valuable in this respect are external triggers that enable us to precisely determine where, when, and to what extent a process is started or stopped. Light is an ideal external trigger: It is highly selective and if applied correctly also harmless. It can be generated and manipulated with well-established techniques, and many ways exist to apply light to living systems--from cells to higher organisms. This Review will focus on developments over the last six years and includes discussions on the underlying technologies as well as their applications.

A chiral cyclotrisazobiphenyl: synthesis and photochemical properties

A chiral cyclotrisazobiphenyl macrocycle was synthesized conveniently in three steps from the literature known 3,3'-diaminobimesityl in 37-38% overall yield. Irradiation with 302 nm, 365 nm or visible light allows access to different photostationary states (PSSs). These PSSs can be conveniently read out by CD-spectroscopy as each of them exhibits a positive, a negative, or no signal, respectively, at 275 nm.

Synthesis and isomerization studies of cyclotrisazobiphenyl

We report an efficient synthesis of cyclotris[(E)-3'-(biphenyl-3-yldiazenyl)] compounds (CTBs). An unsubstituted CTB molecule is accessible in four steps in 10% yield overall, whereas a hexa(methoxymethyl ether) CTB analogue was prepared in nine steps (26% yield). The final macrocyclization step was accomplished in up to 80% yield by using a metal-template effect. Furthermore, the photochromic properties were investigated, and all four isomers were detected and characterized by NMR spectroscopy. A strong influence from the solvent and the irradiation wavelength on the switching process was observed. Irradiation in pyridine yielded the highest amount of the all-Z isomer in the photostationary state. For a full conversion to the all-E isomer, the reaction has to be heated to 45 °C. The isomerization to the all-E isomer is slow at room temperature, with a half-life time of the all-Z isomer of more than nine days in dimethyl sulfoxide (DMSO). Conditions were established to access each possible isomer as the major component in the photostationary state.