Although the radical ion pair has been frequently invoked as a key intermediate in DNA oxidative damage reactions and photoinduced electron transfer processes, the unambiguous detection and characterization of this species remain formidable and unresolved due to its extremely unstable nature and low concentration. We use the strategy that, at cryogenic temperatures, the transient species could ...

Photocatalytic reactions of enones using metal polypyridyl complexes proceed by very different reaction manifolds in the presence of either Lewis or Brønsted acid additives. Previous work from our lab demonstrated that photocatalytic [2+2] cycloadditions of enones required the presence of a Lewis acidic co-catalyst, presumably to activate the enone and stabilize the key radical anion intermedia...

The blue neutral luciferase flavin radical has been shown not to be in a catalytically significant equilibrium with species leading to emission of light [Kurfürst, M., Ghisla, S., Presswood, R., & Hastings, J. W. (1982) Eur. J. Biochem. 123, 355-361]. It is shown here that this radical can nevertheless react with O2-. to form a species that is competent in light emission. From its properties, t...

Cervical cancer is one of the most common malignancy diagnosed during pregnancy. The experience of the use of neoadjuvant chemotherapy (NACT) with paclitaxel plus cisplatin during pregnancy is limited. Three pregnant women with International Federation of Gynecology and Obstetrics (FIGO) stage IB cervical cancer received NACT with paclitaxel plus cisplatin until fetal lung maturity, and then un...

Cyclooxygenases (COXs) are heme-containing sequence homodimers that utilize tyrosyl radical-based catalysis to oxygenate substrates. Tyrosyl radicals are formed from a single turnover of substrate in the peroxidase active site generating an oxy-ferryl porphyrin cation radical intermediate that subsequently gives rise to a Tyr-385 radical in the cyclooxygenase active site and a Tyr-504 radical n...

The antitumor agent 3-amino-1,2,4-benzotriazine 1,4-dioxide (tirapazamine, TPZ, 1) gains medicinal activity through its ability to selectively damage DNA in the hypoxic cells found inside solid tumors. This occurs via one-electron enzymatic reduction of TPZ to yield an oxygen-sensitive drug radical (2) that leads to oxidatively generated DNA damage under hypoxic conditions. Two possible mechani...

The Maillard reaction occurring between amino group and carbonyl group produces neoformed compounds having certain levels of antioxidant activity depending on the reaction conditions and the type of reactants. In this study, maillard reaction products (MRPs) derived from four model systems including chitosan-glucose (CG), chitosan-fructose (CF), chitosanmaltose (CM) and chitosan-lactose (CL) so...

The solvent dependent photochemistry of fenofibric acid (FA) was studied by femtosecond transient absorption and nanosecond time-resolved resonance Raman experiments and density functional theory calculations. In acetonitrile-rich solution, a typical nπ* triplet state FA ((3)FA) is formed through a highly efficient intersystem crossing and then the (3)FA species undergoes some reaction with wat...

Chromatin and a subunit of chromatin containing a complex of DNA and the core histones--H2A, H2B, H3, and H4--have been prepared from cultured Chinese hamster cells. Comparison of the formation of radiation-induced DNA--protein crosslinks in whole chromatin with that in the DNA--core histone complex has demonstrated that the core histones are the specific proteins involved in crosslinking. gamm...

During the enzymatic cycle of the cytochromes P450, dioxygen binds to the ferrous haemprotein when the resting ferric haemprotein has undergone a one-electron oxidation after substrate binding. A further one-electron reduction generates an intermediate that is isoelectronic with a peroxide dianion coordinated to a ferric iron. Heterolytic cleavage of the omicron--omicron bond generates water an...