Lipid oxygen removal

Lipid peroxidation (see Fig. 17.2) is a chain reaction that can be attacked in many ways. The chain reaction can be inhibited by use of radical scavengers (chain termination). Initiation of the chain reaction can be blocked by either inhibiting synthesis. of reactive oxygen species (ROS) or by use of antioxidant enzymes like superoxide dismutase (SOD), complexes of SOD and catalase. Finally, agents that chelate iron can remove free iron and thus reduce Flaber-Weiss-mediated iron/oxygen injury. 

The chloroform solution of lipids (Solution A) is placed in a 50-mL round-bottomed spherical Quick-fit flask. Following evaporation of the solvent in a rotary evaporator at about 37°C, a thin lipid film is formed on the walls of the flask. The film is flushed for about 60 seconds with oxygen-free nitrogen (N2) to ensure complete solvent removal and to replace air. Two milliliters of distilled water and a few glass beads are added into the flask, the stopper is replaced, and the flask shaken vigorously by hand or mechanically until the lipid film has been transformed into a milky suspension. This process is carried out above the liquid-crystalline transition temperature (7/) of the phospholipid component of liposomes (> 7/) by prewarming the water... 

The hydrogens in lipids are linked to carbon, whereas the hydrogen in water is linked to electron-withrawing oxygens. The removal of electrons from aronnd the... 

Dipyridamole has also been shown to have antioxidant effects (19). Antioxidants act to remove harmful reactive-oxygen species and protect low-density lipoproteins (LDL) from oxidation oxidized LDL plays a key role in the development and propagation of atherosclerosis. The antioxidant effects of dipyridamole may be both direct (by scavenging oxygen and hydroxyl radicals, inhibiting lipid peroxidation and oxidative modification of LDL) (20-22) and indirect (via adenosine, which reduces superoxide anion generation). Dipyridamole has been shown to be a more effective anioxidant than ascorbic acid, alpha-tocopherol, or probucol (22). 

Superoxide ion is not highly reactive towards hydrocarbons (i.e., lipids) and is readily removed from biological systems by superoxide dismutase, forming hydrogen peroxide and oxygen. However, the protonated superoxide ion or hydroperoxyl radical, HO, reacts with NADH and alkanes. Although such a reactive... 

To overcome this spin barrier, initiators or catalysts are required to start the lipid oxidation process by removing an electron from either the lipid or oxygen or by changing the electron spin of the oxygen. As only trace amounts of catalysts are needed, many situations that appear to be spontaneous or uncatalyzed are actually driven by contaminants or conditions that have gone undetected or unconsidered. Indeed, in most foods, biological systems, and laboratory experiments, it is fair to say that multiple catalysts and initiators are always operative. 

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