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Study of Photoinduced Energy and Electron Transfer in α‐Terthienyl‐Bovine Serum Albumin Conjugates: A Laser Flash Photolysis Study *
Author(s) -
Boch R.,
Mohtat N.,
Lear Y.,
Arnason J. T.,
Durst T.,
Scaiano J. C.
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.tb02426.x
Subject(s) - photochemistry , chemistry , flash photolysis , quenching (fluorescence) , singlet oxygen , chromophore , conjugated system , bovine serum albumin , reaction rate constant , electron transfer , electron acceptor , triplet state , electron donor , singlet state , cationic polymerization , aqueous solution , oxygen , kinetics , fluorescence , excited state , organic chemistry , molecule , catalysis , biochemistry , physics , quantum mechanics , nuclear physics , polymer
The photochemistry of α‐terthienyl (α‐T) has been examined in bovine serum albumin (BSA). Freely associated and covalently conjugated α‐T chromophores show similar behavior toward nonpolar quenchers such as oxygen and benzoquinone but show significant differences in the case of quenching by methyl viologen, a water‐soluble cationic electron acceptor; in this case, triplet quenching reveals two distinct α‐T populations, attributed to chromophores in sites showing very different accessibility from the aqueous phase. Rate constants for triplet quenching in BSA are generally slower than those observed in homogeneous solution for free α‐T. For example, in the case of oxygen, the rate constant is about one order of magnitude smaller when α‐T is associated or conjugated with the protein compared with α‐T in solution. While triplet yields for α‐T are essentially the same in solution and in the protein environment, the yield of detectable singlet oxygen is substantially reduced in the protein. This is attributed to a geminate reaction within the protein involving singlet oxygen trapping in the vicinity of the generation site.