Optical manipulation of sphingolipid biosynthesis using photoswitchable ceramides

Ceramides are central intermediates of sphingolipid metabolism that also function as potent messengers in stress signaling and apoptosis. Progress in understanding how ceramides execute their biological roles is hampered by a lack of methods to manipulate their cellular levels and metabolic fate with appropriate spatiotemporal precision. Here, we report on clickable, azobenzene-containing ceramides, caCers, as photoswitchable metabolic substrates to exert optical control over sphingolipid production in cells. Combining atomic force microscopy on model bilayers with metabolic tracing studies in cells, we demonstrate that light-induced alterations in the lateral packing of caCers lead to marked differences in their metabolic conversion by sphingomyelin synthase and glucosylceramide synthase. These changes in metabolic rates are instant and reversible over several cycles of photoswitching. Our findings disclose new opportunities to probe the causal roles of ceramides and their metabolic derivatives in a wide array of sphingolipid-dependent cellular processes with the spatiotemporal precision of light

Seasgrass Productivity Elevates Ωar and Calcification Rates in Acropora Cervicornis

Carbon fluxes associated with seagrass bed metabolism are known to cause an elevation in the aragonite saturation state (Ωar) of the overlying water. It has been hypothesized that corals located downstream could experience a boost in their ability to calcify. Given that seagrass biomass and productivity are known to be stimulated by ocean acidification (OA) conditions, the possibility exists that the rise in Ωar could increase as OA conditions become more severe. If true, corals on patch reefs ringed by extensive seagrass beds, as is common on the Florida Reef Tract, could potentially be buffered to some degree from the ill effects of OA. A patch reef fringed by seagrass beds located near Broad Key (25.334N, 80.199W) served as the in situ study site. The in situ growth rates of Acropora cervicornis corals located in the seagrass bed and on the patch reef were measured to gauge the response of the corals to the increase in Ωar. Several Lagrangian drifts were conducted to quantify the increase in Ωar as a parcel of water flowed over the seagrass bed to the patch reef. A lab study was set up to evaluate the calcification response of Acropora cervicornis to changes in pCO2 from ambient (390ppm) to projected (900ppm) pCO2 conditions. Using the results of the lab study it was found that the calcification response of A. cervicornis to a unit change in Ωar was 21.6%, which is a similar response to pCO2 as other coral species as observed by Chan and Connolly, 2011. A second model was created to calculate the benefit of seagrass productivity on the calcification rates of Acorpora cervicornis based on the results of the lab study and Lagrangian drifts. This model found that seagrass the benthic community, which was predominantly composed of Thalassia testudinum, was capable of enhancing calcification rates of Acorpora cervicornis by 7% on average ranging from 0% to 22%. It is unclear, however, how much of an impact seagrass beds will have in the future as various stressors threaten their existence

Bioinspired photocontrollable microstructured transport device

A transportation device can be tunably controlled by the ultraviolet actuation of a liquid crystal elastomer.</jats:p

Tin-Functionalized Azobenzenes as Nucleophiles in Stille Cross-Coupling Reactions

The metalation of azobenzene by halogen–metal exchange typically leads to a reduction of the azo group to give hydrazine derivatives as major byproducts, instead of the desired metalated azobenzene species. In cross-coupling reactions, azobenzenes therefore usually serve as electrophiles, which greatly limits the scope of the reaction. To solve this problem, we have developed a mild and fast method to stannylate azobenzenes in high yields. This research shows that these stannylated azobenzenes can be used as nucleophilic components in Stille cross-coupling reactions with aryl bromides. The cross-coupling products were obtained in high yields ranging from 70 to 93%. With this reversal of the nucleophilic and electrophilic components, cross-coupling products are now accessible in which the aromatic rings coupled to the azobenzene bear functional groups that are sensitive to metalation

Efficient reversible photoisomerisation with large solvodynamic size-switching of a main chain poly(azobenzene-<i>alt</i>-trisiloxane)

Main-chain azobenzene containing polysiloxane with high switching efficiency.</p