Premium
Singlet‐Oxygen Generation from Liposomes: A Comparison of 6β‐Cholesterol Hydroperoxide Formation with Predictions from a One‐Dimensional Model of Singlet‐Oxygen Diffusion and Quenching
Author(s) -
Fu Yingxian,
Sima Paul D.,
Kanofsky Jeffrey R.
Publication year - 1996
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1996.tb03071.x
Subject(s) - liposome , singlet oxygen , chemistry , quenching (fluorescence) , phosphatidylcholine , photochemistry , diffusion , oxygen , fluorescence , membrane , organic chemistry , phospholipid , biochemistry , thermodynamics , physics , quantum mechanics
— We measured 6β‐cholesterol hydroperoxide (6β‐CHP), a specific singlet‐oxygen (O 2 (δg)) product, during irradiation of unilamellar dimyristoyl 1‐α‐phosphatidylcholine liposomes containing cholesterol and zinc phthalocyanine (ZnPC). The effects of liposome size, the hydrophobic (O 2 ( 1 δ g )) quencher, β‐carotene, and hydrophilic O 2 ( 1 δ g ) quenchers upon the amount of 6β‐CHP formed were determined and interpreted in terms of a one dimensional model of 2 ( 1 δ g ) quenching and diffusion. The model correctly predicted (1) that the amount of 6β‐CHP was increased with increasing liposome size, (2) that P‐carotene was more effective at reducing 6β‐CHP formation in 400 nm diameter liposomes than 100 nm diameter liposomes and (3) that the hydrophilic quencher, water, was also more effective in large liposomes than in small liposomes. The hydrophobic quencher, β‐carotene, was more effective at reducing the formation of 6β‐CHP than at reducing the 1270 nm O 2 ( 1 δ g ) emission. This difference was found to be due to the size distribution present in the liposome preparations because the difference between the 6β‐CHP data and the 1270 nm emission data was much smaller in liposome preparations with a narrow size distribution. When a significant size distribution was present, the 6β‐CHP data were weighted more heavily with large‐diameter liposomes, while the 1270 nm emission data were weighted more heavily with small‐diameter liposomes.