Factors affecting the uncaging efficiency of 500 nm light-activatable BODIPY caging group.

Photoremovable protective groups, or caging groups, enable us to regulate the activities of bioactive molecules in living cells upon photoirradiation. Nevertheless, requirement of UV light for activating caging group is a significant limitation due to its cell toxicity and its poor tissue penetration. Our group previously reported a 500 nm light-activatable caging group based on BODIPY scaffold, however, its uncaging efficiency was lower than those of conventional caging groups. Here we show that the uncaging quantum yield (QY) of BODIPY caging group depends upon the driving force of photo-induced electron transfer (PeT). We also found that the uncaging QY increased in less polar solvents. We applied these findings to develop BODIPY-caged capsaicin, which is well localized to low-polarity intracellular compartments, as a tool to stimulate TRPV1 in live cells in response to blue-green light.

The effects of some operational parameters in photodegradation of benzylamine and aniline and their kinetics in aqueous suspension of TiO2 and Pt -loaded TiO2.

Photocatalytic degradation of benzylamine and aniline on TiO2, Pt-modified TiO2, ZnO and ZnS in aqueous solution has been investigated. The degradation of the compounds follows a pseudo-first-order kinetics according to Langmuir-Hinshelwood model. The degradation process of benzylamine and aniline was evaluated by ninhydrin spectrophotometric method using UV-visible spectrophotometer in lambda(max) = 538 and 525 nm, respectively. The results showed the order of Pt/TiO2 > TiO2 > ZnO > ZnS for photocatalytic activity. In addition increasing of the Pt-loading was found to enhance the degradation rate of the compounds up to the optimal amount of 5 wt. % onto the surface of TiO2 so that the rates of degradation were increased about two times. Rate constants for photodegradation of benzylamine and aniline were found to be 1.4 x 10(-3) min(-1) and 0.7 x 10(-3) min(-1) for TiO2 as photocatalyst, while 2.7 x 10(-3) min(-1) and 1.7 x 10(-3) min(-1) for (5 wt.%) Pt/TiO2 as photocatalyst. Running the reactions in various pH (5-11), indicated that the pH = 8 and 10 or Higher are the optimum pH for photocatalytic degradation of benzylamine and aniline respectively. The effects of some other parameters such as amount of photocatalyst, flux of oxygen and irradiation time were evaluated. Furthermore, the Langmuir-Hinshelwood rate constant k(r) and adsorption constant K(A) for the titled compounds are reported.