AffiliationPaterson Laboratories, Christie Hospital and Holt Radium Institute, Manchester, M20 9BX
MetadataShow full item record
AbstractThe semireduced, semioxidized, and OH(.)-adduct radicals of bilirubin (BR) and biliverdin (BV) have been characterized using pulse radiolysis techniques. Laser flash photolysis (265-nm) of these pigments led to monophotonic photoionization with quantum yields of 0.08 for BR and 0.03 for BV. No evidence for triplet formation or for photoisomerization was found after 265-nm laser excitation. However, 347-nm excitation of BR in chloroform led to simultaneous photoisomerization and radical formation, but the radicals are thought to have originated from a pathway other than photoionization. The relevance of these observations to BR photoreactivity is discussed. BR radical ions in alkaline solution did not react with tryptophan (TrpH), but the semioxidized TrpH radical oxidized BR with k = 4.3 X 10(8) dm3 mole-1 sec-1. When human serum albumin (HSA) was oxidized using radiolytically generated azide radicals, a radical transformation involving TrpH and TyrOH residues occurred with k = 3.8 X 10(3) sec-1. When BR was complexed with the protein the transformation rate was reduced to 1.6 X 10(3) sec-1. This was interpreted in terms of a conformational change in the protein. Identification of the probable residues involved provided information about the primary BR binding site which was consistent with an earlier report.
CitationThe radical ions and photoionization of bile pigments. 1983, 96 (3):450-61 Radiat Res
- Photoreactivity of biologically active compounds. XIX: excited states and free radicals from the antimalarial drug primaquine.
- Authors: Kristensen S, Edge R, Tønnesen HH, Bisby RH, Navaratnam S
- Issue date: 2009 Mar 3
- The reactions of cytidine and 2'-deoxycytidine with SO4.- revisited. Pulse radiolysis and product studies.
- Authors: Aravindakumar CT, Schuchmann MN, Rao BS, von Sonntag J, von Sonntag C
- Issue date: 2003 Jan 21
- Oxidation of tryptamine and 5-hydroxytryptamine: a pulse radiolysis and quantum chemical study.
- Authors: Gaikwad P, Priyadarsini KI, Naumov S, Rao BS
- Issue date: 2009 Jul 23
- Oxidation reactions of a bovine serum albumin-bilirubin complex. A pulse radiolysis study.
- Authors: Adhikari S, Gopinathan C
- Issue date: 1996 Jan
- Characterization of the transient species generated by the photoionization of Berberine: a laser flash photolysis study.
- Authors: Cheng LL, Wang M, Zhu H, Li K, Zhu RR, Sun XY, Yao SD, Wu QS, Wang SL
- Issue date: 2009 Sep 1