Photobleaching of merocyanine 540: involvement of singlet molecular oxygen. Photochem Photobiol 1992 Apr;55(4):483-9
Date
04/01/1992Pubmed ID
1620725DOI
10.1111/j.1751-1097.1992.tb04268.xScopus ID
2-s2.0-0026847607 (requires institutional sign-in at Scopus site) 22 CitationsAbstract
The purpose of this study was to assess the mechanism of merocyanine 540 (MC540) photobleaching in a liposomal system. Broad based visible irradiation of MC540 in unilamellar dilauroylphosphatidylcholine (DLPC) vesicles resulted in dye bleaching that was strictly O2 dependent. The rate of self-sensitized photobleaching was enhanced in D2O and inhibited by both azide and histidine, consistent with 1O2 intermediacy (Type II chemistry). Supportive evidence for this mechanism was obtained by using a Type II sensitizer, aluminum phthalocyanine tetrasulfonate (AlPcS lambda max = 678 nm). Irradiation of AlPcS and MC540 in DLPC with lambda greater than 630 nm (absorbed only by AlPcS) light resulted in rapid bleaching of MC540, which was stimulated by D2O and inhibited by azide. A rate constant of 10(7) M-1 s-1 was determined for the chemical quenching of 1O2 by MC540. The rate constant for physical quenching of 1O2 by MC540 was estimated to be ca 10(9) M-1 s-1.
Author List
Singh RJ, 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
LiposomesMolecular Structure
Oxygen
Phosphatidylcholines
Photochemistry
Pyrimidinones
Radiation-Sensitizing Agents
Singlet Oxygen