An electron spin resonance study of merocyanine 540-mediated type I reactions in liposomes. Photochem Photobiol 1991 Jan;53(1):39-45
Date
01/01/1991Pubmed ID
1851304DOI
10.1111/j.1751-1097.1991.tb08465.xScopus ID
2-s2.0-0025928466 (requires institutional sign-in at Scopus site) 19 CitationsAbstract
The merocyanine 540 (MC540)-mediated reduction of nitroxide spin labels in a liposomal system was examined using electron spin resonance (ESR) spectroscopy. Spin label reduction was light driven, and occurred in liposomes composed of both fully-saturated (dimyristoyl) and mono-unsaturated (1-palmitoyl-2-oleoyl) phosphatidylcholine. Loss of the nitroxide ESR signal was enhanced by the physiological electron donors glutathione, cysteine, and NADPH; and was strongly inhibited by the presence of molecular oxygen. Nitroxides reduced in the presence of MC540 alone could be regenerated either by purging the sample with air or by the addition of ferricyanide, indicating that the ESR signal loss was due to reduction to the corresponding hydroxylamines. Only partial regeneration was attained for nitroxides reduced in the presence of glutathione, cysteine, or NADPH. Reduction rates for the lipophilic spin labels, 5-, 12-, and 16-doxyl stearic acid, were not influenced by the position of the nitroxide moiety along the alkyl chain, however reduction of spin labels occupying primarily the aqueous phase was much slower. These studies demonstrate that MC540 can initiate oxidation/reduction (Type I) reactions. Such Type I processes may augment the effects of singlet oxygen in MC540-mediated photodynamic therapy.
Author List
Feix JB, Kalyanaraman BAuthors
Jimmy B. Feix PhD Professor in the Biophysics department at Medical College of WisconsinBalaraman Kalyanaraman PhD Professor in the Biophysics department at Medical College of Wisconsin
MESH terms used to index this publication - Major topics in bold
CysteineElectron Spin Resonance Spectroscopy
Glutathione
Liposomes
NADP
Oxidation-Reduction
Pyrimidinones
Radiation-Sensitizing Agents
Structure-Activity Relationship