Probing the Formation and Conformational Relaxation of Previtamin D and Analogues in Solution and in Lipid Bilayers.

The photosynthesis of vitamin D in mammalian skin results from UV-B irradiation of provitamin D (7-dehydrocholesterol, DHC) at ca. 290 nm. Upon return to the ground state, the hexatriene product, previtamin D, undergoes a conformational equilibration between helical gZg and more planar tZg and tZt forms.

Rhodamine B degradation by nanosized zeolitic imidazolate framework-8 (ZIF-8).

Adsorption and photodegradation of rhodamine B by ZIF-8 nanocrystals were studied using spectroscopic techniques coupled with density functional theory (DFT) cluster calculations. A fast adsorption rate was observed in the dark, but upon exposure to visible light or UV irradiation the adsorption rate noticeably increased. Although several studies previously reported this phenomenon involving bulk ZIF-8 powder, this is the first mechanistic study to our knowledge that demonstrates adsorption and degradation of rhodamine B by nanosized ZIF-8 under various light conditions.

The role of tachysterol in vitamin D photosynthesis - a non-adiabatic molecular dynamics study.

To investigate the role of tachysterol in the photophysical/photochemical regulation of vitamin D photosynthesis, we studied its electronic absorption properties and excited state dynamics using time-dependent density functional theory (TDDFT), second-order approximate coupled cluster theory (CC2), and non-adiabatic surface hopping molecular dynamics in the gas phase. In excellent agreement with experiments, the simulated electronic spectrum shows a broad absorption band with a remarkably higher extinction coefficient than the other vitamin D photoisomers provitamin D, lumisterol, and previtamin D. The broad band arises from the spectral overlap of four different ground state rotamers.