Coumarin-based octopamine phototriggers and their effects on an insect octopamine receptor.

We have developed and characterized efficient caged compounds of the neurotransmitter octopamine. For derivatization, we introduced [6-bromo-8-(diethylaminomethyl)-7-hydroxycoumarin-4-yl]methoxycarbonyl (DBHCMOC) and {6-bromo-7-hydroxy-8-[(piperazin-1-yl)methyl]coumarin-4-yl}methoxycarbonyl (PBHCMOC) moieties as novel photo-removable protecting groups. The caged compounds were functionally inactive when applied to heterologously expressed octopamine receptors (AmOctα1R). Upon irradiation with UV-visible or IR light, bioactive octopamine was released and evoked Ca2+ signals in AmOctα1R-expressing cells. The pronounced water solubility of compounds 2-4 in particular holds great promise for these substances as excellent phototriggers of this important neurotransmitter.

[8-[Bis(carboxymethyl)aminomethyl]-6-bromo-7-hydroxycoumarin-4-yl]methyl moieties as photoremovable protecting groups for compounds with COOH, NH2, OH, and C=O functions.

We introduce a variant of coumarin-based photoactivatable protecting groups and use it exemplarily for caging of a carboxylic acid, an amine, a phenol, and a carbonyl compound. The caged compounds are efficiently photolyzed at long-wavelength UV/vis irradiation. Compared to the corresponding (6-bromo-7-hydroxycoumarin-4-yl)methyl (Bhc) derivatives, the novel coumarin-type caged compounds are distinguished by (i) dramatically increased solubilities in aqueous buffers, (ii) lower pK(a) values of the C7 hydroxyl of the coumarin chromophore, thus permitting efficient photorelease at lower pH, and (iii) higher photolysis quantum yields in the case of photoprotected carbonyl compounds. The primary step of the photocleavages occurs with rate constants of about 10(9) s(-1).

{7-[Bis(carboxymethyl)amino]coumarin-4-yl}methoxycarbonyl derivatives for photorelease of carboxylic acids, alcohols/phenols, thioalcohols/thiophenols, and amines.

Light-induced release of biomolecules from inactive precursor molecules represents a powerful method to study cellular processes with high temporal and spatial resolution. Here we report the synthesis and photochemistry of a series of {7-[bis(carboxymethyl)amino]coumarin-4-yl}methyl carboxylates, carbonates, carbamates, and thiocarbonates as potential phototriggers for compounds with COOH, OH, NH(2), and SH functions. The compounds are soluble in aqueous buffer, show low fluorescence, and are efficiently photolysed by irradiation with UV/Vis or IR light to release carboxylates, alcohols, phenols, amines, thioalcohols, or thiophenols.

Caged capsaicins: New tools for the examination of TRPV1 channels in somatosensory neurons.

The vanilloid capsaicin, N-(4-hydroxy-3-methoxybenzyl)-8-methylnon-6-enamide, is the pungent ingredient of chili peppers and is used in pain research as an activating ligand of heat-sensitive transduction channels in nociceptive neurons. Here we describe the synthesis and application of two capsaicin derivatives modified at the hydroxy function of the vanillyl motif: alpha-carboxy-4,5-dimethoxy-2-nitrobenzyl-caged (CDMNB-caged) capsaicin and {7-[bis(carboxymethyl)amino]coumarin-4-yl}methoxycarbonyl-caged (BCMACMOC-caged) capsaicin. These compounds show dramatically reduced pungency, but release active capsaicin upon irradiation with UV light. CDMNB-caged capsaicin can be used to perform concentration-jump experiments, while BCMACMOC-caged capsaicin is membrane-impermeant and can be applied selectively to the intracellular or extracellular sides of a plasma membrane. Both compounds can serve as valuable research tools in pain physiology.