Mechanism of photosensitized oxidation of tyrosine by gallium or zinc phthalocyanine in homogeneous and aqueous micellar media.
The mechanism of the photo-oxidation of tyrosine (Tyr) sensitized by sulphonated phthalocyanine at pH 10 in homogeneous aqueous solution or aqueous cetyltrimethylammonium chloride (CTAC) micellar medium was studied by kinetic analysis and laser flash photolysis. Cationic CTAC micelles promote the importance of a type I mechanism in the photo-oxidation of Tyr sensitized by sodium tetrasulphonated chlorogallium phthalocyanine (GaTSPC) whereas they have little effect on the photo-oxidation of Tyr sensitized by sodium disulphonated zinc phthalocyanine (ZnDSPC). In all cases studied, it was shown that the type I mechanism (electron transfer) takes place more easily using GaTSPC as sensitizer, whereas, using ZnDSPC as sensitizer, a type II mechanism (involving 1O2) predominates. The results are discussed according to the mutual position of the sensitizer and the substrate in the aqueous micellar medium and the ability of the triplet state of the phthalocyanine to abstract an electron from Tyr.
Zhang
X F
XF
Institute of Photographic Chemistry, Academia Sinica, Beijing, China.
Xu
H J
HJ
D001386:Azides; D007834:Lasers; D008027:Light; D008665:Metalloporphyrins; D008823:Micelles; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010782:Photolysis; D017319:Photosensitizing Agents; D019810:Sodium Azide; D013053:Spectrophotometry; D014443:Tyrosine
D001386:Azides; D008665:Metalloporphyrins; D008823:Micelles; D017319:Photosensitizing Agents; D014443:Tyrosine; D019810:Sodium Azide