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A Kinetic Study of the Photodynamic Effect on Tryptophan Methyl Ester and Tryptophan Octyl Ester in DOPC Vesicles
Author(s) -
Posadaz Ariana,
Correa N. Mariano,
Biasutti M. Alicia,
García Norman A.
Publication year - 2010
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.1751-1097.2009.00641.x
Subject(s) - chemistry , vesicle , tryptophan , reaction rate constant , rose bengal , quenching (fluorescence) , phosphatidylcholine , aqueous solution , photochemistry , phospholipid , fluorescence , kinetics , organic chemistry , amino acid , biochemistry , membrane , physics , quantum mechanics
The photodynamic effect on tryptophan methyl ester (trpME) and tryptophan octyl ester (trpOE), using the O2(1Δ g )‐photosensitizers Rose Bengal (RB) and Perinaphthenone (PN) has been studied in large unilamellar vesicles (LUVs) of the phospholipid 1,2‐di‐oleoyl‐sn‐glycero‐3‐phosphatidylcholine (DOPC) by stationary photolysis and time‐resolved methods. This work reports on the influence of both the site (O 2 ( 1 Δ g )) generation and the location of the tryptophan derivatives (trpD), on the photo‐oxidation process in a compartmentalized system. The apparent rate constant values for chemical quenching of O 2 ( 1 Δ g ) by trpOE ( k r,app ), was higher in vesicles than in water. Also, the ratio between apparent reactive and overall rate constant values for the deactivation of O 2 ( 1 Δ g ) ( k r,app / k t,app ), increases in vesicles as compared with water, when the oxidative species is generated in the lipidic region or at the interface. Nevertheless, this quotient is lower than the corresponding value in water when O 2 ( 1 Δ g ) is generated in the aqueous pseudophase. For trpME, the k r,app / k t,app values in vesicles and in water are quite similar, confirming the fact that trpME is located in the water pseudophase. Results are discussed in terms of relative protection against O 2 ( 1 Δ g ) attack in a microheterogeneous medium as compared with water.