Increased cerebral output of free radicals during hypoxia: implications for acute mountain sickness?

Bailey DM, Taudorf S, Berg RMG, Lundby C, McEneny J, Young IS, Evans KA, James PE, Shore A, Hullin DA, McCord JM, Pedersen BK, Moller K. Increased cerebral output of free radicals during hypoxia: implications for acute mountain sickness? Am J Physiol Regul Integr Comp Physiol 297: R1283-R1292, 2009. First published September 2, 2009; doi: 10.1152/ajpregu.00366.2009.-This study examined whether hypoxia causes free radical-mediated disruption of the blood-brain barrier (BBB) and impaired cerebral oxidative metabolism and whether this has any bearing on neurological symptoms ascribed to acute mountain sickness (AMS). Ten men provided internal jugular vein and radial artery blood samples during normoxia and 9-h passive exposure to hypoxia (12.9% O-2). Cerebral blood flow was determined by the Kety-Schmidt technique with net exchange calculated by the Fick principle. AMS and headache were determined with clinically validated questionnaires. Electron paramagnetic resonance spectroscopy and ozone-based chemiluminescence were employed for direct detection of spin-trapped free radicals and nitric oxide metabolites. Neuron-specific enolase (NSE), S100 beta, and 3-nitrotyrosine (3-NT) were determined by ELISA. Hypoxia increased the arterio-jugular venous concentration difference (a-v(D)) and net cerebral output of lipid-derived alkoxyl-alkyl free radicals and lipid hydroperoxides (P

Rates for repair of pBR 322 DNA radicals by thiols as measured by the gas explosion technique: evidence that counter-ion condensation and co-ion depletion are significant at physiological ionic strength.

Rates of rapair of pBR 322 plasmid DNA radicals by thiols of varying net charge (Z) at pH 7 and physiological ionic strength were measured using the oxygen explosion technique. The extent of conversion of supercoiled to relaxed circular plasmid was measured by HPLC as a function of the time of oxygen exposure before or after irradiation, the time-courses being fitted by a pseudo-first-order kinetic expression with k1 = k2[RSH]. Values of k2 (M-1 S-1) were: 2.1 x 10(5) (GSH, Z = -1), 1.4 x 10(6) (2-mercaptoethanol, Z = 0), 1.2 x 10(7) (cysteamine, Z = +1), 6.6 x 10(7) (WR-1065 or N-(2-mercaptoethyl)-1,3-diamino?? propane, Z = +2). The approximately 6-fold increase in rate with each unit increase in Z is attributed to concentration of cationic thiols near DNA as a consequence of counter-ion condensation and reduced levels of anionic thiols near DNA owing to co-ion depletion. The results are quantitatively consistent with chemical repair as a significant mechanism for radioprotection of cells by neutral and cationic thiols under aerobic conditions, but indicate that repair by GSH will compete effectively with oxygen only at low oxygen tension.

Dissociative electron attachment to C2F5 radicals

Dissociative electron attachment to the reactive C2F5 molecular radical has been investigated with two complimentary experimental methods; a single collision beam experiment and a new flowing afterglow Langmuir probe technique. The beam results show that F- is formed close to zero electron energy in dissociative electron attachment to C2F5. The afterglow measurements also show that F- is formed in collisions between electrons and C2F5 molecules with rate constants of 3.7 × 10-9 cm3 s-1 to 4.7 × 10-9 cm3 s-1 at temperatures of 300–600 K. The rate constant increases slowly with increasing temperature, but the rise observed is smaller than the experimental uncertainty of 35%.

Aerobic oxidation catalysis with stable radicals

Selective oxidation reactions are challenging when carried out on an industrial scale. Many traditional methods are undesirable from an environmental or safety point of view. There is a need to develop sustainable catalytic approaches that use molecular oxygen as the terminal oxidant. This review will discuss the use of stable radicals (primarily nitroxyl radicals) in aerobic oxidation catalysis. We will discuss the important advances that have occurred in recent years, highlighting the catalytic performance, mechanistic insights and the expanding synthetic utility of these catalytic systems.

Identifying the distinct features of geometric structures for hole trapping to generate radicals on rutile TiO2(110) in photooxidation using density functional theory calculations with hybrid functional

Using density functional theory calculations with HSE 06 functional, we obtained the structures of spin-polarized radicals on rutile TiO2(110), which is crucial to understand the photooxidation at the atomic level, and further calculate the thermodynamic stabilities of these radicals. By analyzing the results, we identify the structural features for hole trapping in the system, and reveal the mutual effects among the geometric structures, the energy levels of trapped hole states and their hole trapping capacities. Furthermore, the results from HSE 06 functional are compared to those from DFT + U and the stability trend of radicals against the number of slabs is tested. The effect of trapped holes on two important steps of the oxygen evolution reaction, i.e. water dissociation and the oxygen removal, is investigated and discussed.