Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9607084 | Journal of Photochemistry and Photobiology B: Biology | 2005 | 7 Pages |
Abstract
Both the neurotransmitter serotonin and the unnatural amino acid 5-hydroxytryptophan (5HT), contain the 5-hydroxyindole chromophore. The photochemistry of 5HT is being investigated in relation to the multiphoton excitation of this chromophore to produce a characteristic photoproduct with green fluorescence ('hyperluminescence'). Laser flash photolysis (308 nm) of 5HT in aqueous solution at neutral pH produces both the neutral 5-indoloxyl radical (λmax 400-420 nm) and another transient absorption with λmax 480 nm and lifetime of 2 μs in deaerated solutions. Based on quenching by oxygen and β-carotene, the species at 480 nm is identified as the triplet excited state of 5HT. In acidic solution a new oxygen-insensitive intermediate with λmax 460 is assigned to the radical cation of 5HT. Time-resolved measurements of luminescence at 1270 nm have shown that the triplet state of 5HT is able to react with oxygen to form singlet excited oxygen (1O2â) with a quantum yield of â¼Â 0.1. However, 5HT has also been found to be an effective quencher of singlet oxygen with a second order rate constant of 1.3 Ã 108 dm3 molâ1 sâ1. The results are discussed in the light of recent observations on the multiphoton-excited photochemistry of serotonin.
Related Topics
Physical Sciences and Engineering
Chemical Engineering
Bioengineering
Authors
S. Dad, R.H. Bisby, I.P. Clark, A.W. Parker,