Ultrafast Electronic Relaxation in 6-Methyluracil and 5-Fluorouracil in Isolated and Aqueous Conditions: Substituent and Solvent Effects.

We report ultrafast extreme ultraviolet photoelectron spectroscopy of 6-methyluracil (6mUra) and 5-fluorouracil (5FUra) in the gas phase and 6mUra and 5-fluorouridine in an aqueous environment. In the gas phase, internal conversion (IC) occurs from ππ* to nπ* states in tens of femtoseconds, followed by intersystem crossing to the ππ* state in several picoseconds. In an aqueous solution, 6mUra undergoes IC almost exclusively to the ground state (S) in about 100 fs, which is essentially the same process as that for unsubstituted uracil, but much faster than that for thymine (5-methyluracil).

Formation of Long-Lived Dark States during Electronic Relaxation of Pyrimidine Nucleobases Studied Using Extreme Ultraviolet Time-Resolved Photoelectron Spectroscopy.

Ultrafast electronic relaxation of nucleobases from ππ* states to the ground state (S) is considered essential for the photostability of DNA. However, transient absorption spectroscopy (TAS) has indicated that some nucleobases in aqueous solutions create long-lived nπ*/ππ* dark states from the ππ* states with a high quantum yield of 0.4-0.

Inhibitory effect of astraxanthin combined with Flavangenol on oxidative stress biomarkers in streptozotocin-induced diabetic rats.

In this study, the effect of dietary antioxidants, such as astaxanthin and Flavangenol, and a combination of both, in counteracting oxidative stress in streptozotocin-induced diabetes was investigated. Streptozotocin-induced diabetic rats were divided into four groups: control, astaxanthin, Flavangenol, and combined astaxanthin and Flavangenol (mix group). Each group other than the control group was fed with an astaxanthin diet (0.