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Spectral study of the photochemistry of di pyrrole models for bilirubin bound to human serum albumin


, : Spectral study of the photochemistry of di pyrrole models for bilirubin bound to human serum albumin. Photochemistry & Photobiology 37(3): 263-270

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 inversely related to the inherent solubility of the dipyrromethenone in aqueous buffer. Fast (ps) configurational isomerization (Z .fwdarw. E) is the major pathway for decay of the 1st excited (singlet) states of the HSA-bound dipyrromethenones. A quantum yield of .apprx. 0.4 is associated with the Z .fwdarw. 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. [The orange-yellow bile pigment bilirubin-IX.alpha., is the pigment associated with jaundice.].

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Accession: 006459959

PMID: 6844423

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