Improving the in vivo predictability of an on-line HPLC stable free radical decoloration assay for antioxidant activity in methanol-buffer medium

The pivotal role of ROS (reactive oxygen species) in various (patho)physiological processes has stimulated research on the potential of intervening in these processes with antioxidants (AO). In vitro model systems to investigate AO activity against the various ROS are a valuable tool in classifying antioxidants. To improve the in vivo predictability of the results obtained, we have modified and characterized the widely used DPPH (2,2'-diphenyl-1-picrylhydrazyl) on-line decoloration assay. Previous investigations using the DPPH reaction in a pure methanolic medium exhibit slow kinetics and a reaction going to completion. In this study, a medium which includes an aqueous buffer at physiological pH has been applied, resulting in the rapid establishment of equilibrium. The results obtained in an aqueous medium at physiological pH are expected to be more relevant for extrapolation to in vivo circumstances than previously published findings. The antioxidants investigated are classified according to the results obtained and the relevance of their behavior to in vivo situations is discussed. Special emphasis is put on the significance of the results for prediction of redox-cycling characteristics and structure-activity relationships. (c) 2006 Elsevier Inc. All rights reserved

Galactic kinematics with RAVE data

We analyze the distribution of G and K type stars towards the Galactic poles using RAVE and ELODIE radial velocities, 2MASS photometric star counts, and UCAC2 proper motions. The combination of photometric and 3D kinematic data allows us to disentangle and describe the vertical distribution of dwarfs, sub-giants and giants and their kinematics. We identify discontinuities within the kinematics and magnitude counts that separate the thin disk, thick disk and a hotter component. The respective scale heights of the thin disk and thick disk are 225$\pm$10 pc and 1048$\pm$36 pc. We also constrain the luminosity function and the kinematic distribution function. The existence of a kinematic gap between the thin and thick disks is incompatible with the thick disk having formed from the thin disk by a continuous process, such as scattering of stars by spiral arms or molecular clouds. Other mechanisms of formation of the thick disk such as `created on the spot' or smoothly `accreted' remain compatible with our findings.Comment: 15 pages, 13 EPS figures and 1 tabl