The Photochemistry of Bilirubin

Sensitizing effect of Z,Z-bilirubin IXα and its photoproducts on enzymes in model solutions

“…Note that when using a broadband lamp source, the increase in the absorption in the given range of the spectrum is not so pronounced [15]. This has resulted in some authors [15] doubting the presence of a photoproduct with absorption maximum in the range λ = 530-700 nm.…”

“…Note that when using a broadband lamp source, the increase in the absorption in the given range of the spectrum is not so pronounced [15]. This has resulted in some authors [15] doubting the presence of a photoproduct with absorption maximum in the range λ = 530-700 nm. In this connection, we should note that one of the maxima in the absorption spectrum of lumirubin, according to data in [7], is located in the λ = 590 nm region, while the maximum for biliverdin is located in the range 660-750 nm [14,15].…”

“…This has resulted in some authors [15] doubting the presence of a photoproduct with absorption maximum in the range λ = 530-700 nm. In this connection, we should note that one of the maxima in the absorption spectrum of lumirubin, according to data in [7], is located in the λ = 590 nm region, while the maximum for biliverdin is located in the range 660-750 nm [14,15]. However, according to the results of chromatography studies, the increase in optical density in the 530-700 nm region does not correlate either with the increase in the lumirubin concentration or with the increase in the concentration of biliverdin, detected in trace amounts [49].…”

“…2), accompanied by accumulation of colorless products based on monopyrrole and dipyrrole moieties and also biliverdin, formed as a result of oxidation of the methylene bridge and characterized by an extended absorption band with a maximum at about λ = 660-750 nm (depending on the type of solvent) [14,15]. According to [14][15][16], one of the mechanisms for photodegradation of bilirubin involves participation of singlet oxygen in this process (self-sensitized oxidation). In fact, according to a number of indirect estimates, the triplet level of bilirubin has an energy of 150 kJ/cm 2 [14], which makes it possible to generate singlet oxygen since for the latter, the energy of the S 1 level is 1 ∆ g = 94 kJ/cm 2 .…”

“…According to [7], one of the absorption bands of lumirubin is characterized by a maximum at λ = 337 nm, while its photoproducts absorb at 350-370 nm. In the λ = 380 nm, there is also an absorption band from biliverdin, which is practically nonfluorescent and does not have a sensitizing effect [14,15]. In addition to the indicated compounds, some contribution to the observed increase in absorption in the UV region can also come from the products of bilirubin-sensitized degradation of tryptophan amino acid residues of HSA (formylkynurenine, kynurenine), absorbing in the λ = 360 nm region and capable of generating singlet oxygen and having a photodynamic effect [37].…”