Model of singlet oxygen scavenging by α-tocopherol in biomembranes

✍ Scribed by M. Fragata; F. Bellemare

• Publisher: Elsevier Science
• Year: 1980
• Tongue: English
• Weight: 361 KB
• Volume: 27
• Category: Article
• ISSN: 0009-3084
• DOI: 10.1016/0009-3084(80)90015-8

✦ Synopsis

Quenching of singlet molecular oxygen (JAgO2) by a-tocopherol (I) involves the hydroxy function of the chromanol ring of I. In phosphatidylcholine (PC) uni-and multilamellar vesicles this structural element of I is localized at the interface polar headgroup/hydrophobic core. A dielectric constant of • ~ 25 was determined for this special region of the PC bilayer. The ratio ko/ka of rate constants of quenching processes (ko) and irreversible reactions (ka) of I with IAgOz increases with decreasing polarity of the solvent. In ethanolic solutions where • = 25.5, kolkR is about 40. Extrapolation of these results to phospholipid bilayers suggests that at the nearness of the ester carbonyl oxygen of the PC fatty acid moieties, a-tocopherol can deactivate approximately 40 IAgOz molecules before being destroyed. It is concluded that in vivo, one may expect to find a higher ko/ka ratio if the chromanol ring of I hides within the more hydrophobic interiors of the membrane surface peptides.