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SPECTRAL STUDY OF THE PHOTOCHEMISTRY OF DIPYRROLE MODELS FOR BILIRUBIN BOUND TO HUMAN SERUM ALBUMIN
Author(s) -
Lamola Angelo A.,
Braslavsky Silvia E.,
Schaffner Kurt,
Lightner David A.
Publication year - 1983
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.1751-1097.1983.tb04471.x
Subject(s) - human serum albumin , chemistry , isomerization , circular dichroism , photochemistry , fluorescence , quantum yield , bilirubin , excited state , singlet state , aqueous solution , solubility , kinetics , serum albumin , stereochemistry , organic chemistry , chromatography , biochemistry , medicine , physics , quantum mechanics , gastroenterology , nuclear physics , catalysis
—Dipyrromethenones, which include xanthobilirubinic acid (I), its methyl ester (II) and the endo‐ vinyl analog of neoxanthobilirubinic acid methyl ester (“half bilirubin” methyl ester) (III) bind to human serum albumin (HSA) and thereby exhibit greatly increased fluorescence as well as induced circular dichroism in their long wavelength transitions. As determined from fluorescence studies, the “tightness” of the binding to HSA is, inter alia , inversely related to the inherent solubility of the dipyrromethenone in aqueous buffer. Fast (ps) configurational isomerization ( Z → E ) is the major pathway for decay of the first excited (singlet) states of the HSA‐bound dipyrromethenones. A quantum yield of − 0.4 is associated with the Z → E isomerization. Binding to HSA enhances the lifetimes of the less thermodynamically stable E ‐isomers. The results of these studies of “half bilirubins” allow a clear evaluation of the effects of protein binding upon the photophysics and photochemistry of bilirubin.