Photochemistry of kynurenine, a tryptophan metabolite: properties of the triplet state.
Photolysis of aqueous kynurenine (KN) solutions results in the formation of triplet kynurenine TKN. In low pH solutions, triplet formation occurs with almost 100% efficiency, while in neutral solutions the triplet quantum yield is PhiT = 0.018 +/- 0.004. The dissociation constant of TKN, which is attributed to deprotonation of the anilino group, has a pKa value of 4.7. Similar triplet absorption spectra were obtained under direct and acetone-sensitized photolysis. The large difference in quantum yields as a function of pH is attributed to excited-state properties of the first excited singlet state of KN. The rate constant quenching for TKN by oxygen is kq = 2 x 10(9) M(-1) s(-1).
Tsentalovich
Yuri P
YP
International Tomography Center, Institutskaya 3a, Novosibirsk, Russia 630090, Novosibirsk State University, 630090 Novosibirsk, Russia. yura@tomo.nsc.ru
Snytnikova
Olga A
OA
Sherin
Peter S
PS
Forbes
Malcolm D E
MD
D000096:Acetone; D000818:Animals; D003459:Crystallins / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007737:Kynurenine / Q000737:chemistry*; D008027:Light; D008956:Models, Chemical; D010777:Photochemistry / Q000379:methods*; D010782:Photolysis; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet; D013997:Time Factors; D014364:Tryptophan / Q000737:chemistry*; D014867:Water / Q000737:chemistry
D003459:Crystallins; D014867:Water; D000096:Acetone; D007737:Kynurenine; D014364:Tryptophan