Free Radial Introduction

¡@¡@ In our oxygen metabolite system, we may produce Reactive Oxygen Species(ROS). ROS is thought to result from random damage to protein, lipids and DNA, and hence shorten the life span.
¡@¡@The below fiqure is a diagram of ROS pathway.
¡@¡@The ROS often is produced by oxidases when oxidases generate incompletely reduced oxygen species-superoxide(O2-¡E) and hydroxyl radial(OH¡E). Hydroxyl radial is particularly reactive and dangerous. Hydroxyl radical damages proteins in various ways and damages membrane by initiation the oxidation of fatty acid in membrane lipids, a process termed lipid peroxidation. It also damages nucleic acid, both by causing polynucleotide strand breakage and by changing the structure of DNA bases.
¡@¡@ Superoxide is relatively nontoxic. But because it contains an unpaired electron, and it can bind another free radial, nitric oxide(NO¡E),a biological signaling agent in many tissue.The product is peroxynitrite(OONO-), and it can cause lipid peroxidation and protein damage.