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Diastereoselectivity and Site Dependency in the Photochemistry of Ketoprofen in the Bovine Serum Albumin Matrix †
Author(s) -
Monti Sandra,
Manet Ilse,
Manoli Francesco,
Morrone Raffaele,
Nicolosi Giovanni,
Sortino Salvatore
Publication year - 2006
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 - 10.1562/2005-07-11-ra-608
Subject(s) - bovine serum albumin , circular dichroism , chemistry , diastereomer , ketoprofen , enantiomer , photodissociation , serum albumin , matrix (chemical analysis) , stereochemistry , photochemistry , chromatography , biochemistry
The photodegradation of the S(+)‐ and R(–)‐ketoprofen (KP) enantiomers in the bovine serum albumin matrix was studied by steady‐state photolysis with the use of λ irr > 320 nm and transient absorption spectroscopy with λ exc = 355 nm, at 1/1 and 2/1 KP/BSA molar ratios. R(–)‐KP was found to be more labile than S(+). Triplet ketoprofen species were evidenced with lifetimes of 400 ns for S(+) and 600 ns for R(–)‐KP. Further longer‐lived transients with lifetimes of 2.6 and 6.0 μs for S(+) and R(–), respectively, were detected. On the basis of the binding constants of the drug enantiomers to the two main binding sites of the protein, obtained from circular dichroism experiments, the individual disappearance quantum yields of the 1:l and 2:l diastereomeric KP:BSA complexes could be estimated. The photoreactivity in the BSA matrix was rationalized on the basis of diastereoselective photodecarboxy‐lation in the two main protein sites.