Induction of Wavelength-Dependent Photochemistry in Bilirubins by Serum Albumin

McDonagh, Antony F.; Agati, Giovanni; Lightner, David A.

doi:10.1007/pl00013473

Cited by 9 publications

(9 citation statements)

References 26 publications

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“…The Φ ZE value is comparable to that of (Z)xanthobilirubic acid (Figure 1); Φ ZE ∼ 0.19 obtained in methanol containing 0.1% NH 4 OH (λ irr in the range of = 390− 470 nm). 17 The magnitudes of the Z → E and E → Z isomerization quantum yields for 1a were nearly the same in the irradiation wavelength range of 360−410 nm, but they increased approximately by a factor of 2 at longer irradiation wavelengths (490 nm). The observed dependence can be rationalized within the concept of nonequilibration of excited rotamers (NEER).…”

Section: ■ Results and Discussionmentioning

confidence: 89%

Wavelength-Dependent Photochemistry and Biological Relevance of a Bilirubin Dipyrrinone Subunit

et al. 2020

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Phototherapy is a standard treatment for severe neonatal jaundice to remove toxic bilirubin from the blood. Here, the wavelength-dependent photochemistry of vinylneoxanthobilirubic acid methyl ester, a simplified model of a bilirubin dipyrrinone subunit responsible for a lumirubin-like structural rearrangement, was thoroughly investigated by liquid chromatography and mass and absorption spectroscopies, with the application of a multivariate curve resolution analysis method supplemented with quantum chemical calculations. Irradiation of the model chromophore leads to reversible Z → E photoisomerization followed by reversible photocyclization to a sevenmembered ring system (formed as a mixture of diastereomers). Both the isomerization processes are efficient (Φ ZE ∼ Φ EZ ∼ 0.16) when irradiated in the wavelength range of 360−410 nm, whereas the E-isomer cyclization (Φ c = 0.006−0.008) and cycloreversion (Φ −c = 0.002−0.004) reactions are significantly less efficient. The quantum yields of all processes were found to depend strongly on the wavelength of irradiation, especially when lower energy photons were used. Upon irradiation in the tail of the absorption bands (490 nm), both the isomers exhibit more efficient photoisomerization (Φ ZE ∼ Φ EZ ∼ 0.30) and cyclization (Φ c = ∼0.07). In addition, the isomeric bilirubin dipyrrinone subunits were found to possess important antioxidant activities while being substantially less toxic than bilirubin.

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Section: ■ Results and Discussionmentioning

confidence: 89%

Wavelength-Dependent Photochemistry and Biological Relevance of a Bilirubin Dipyrrinone Subunit

et al. 2020

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“…The moist pellet from 10 to 15 million cells (∼20 μl) was mixed with 80–100 μl of 0.1 M di‐octamylamine acetate in methanol, sonicated, and centrifuged. Twenty microliters of the supernatant were chromatographed by reversed phase high‐performance liquid chromatography (HPLC) as described previously (26).…”

Section: Methodsmentioning

confidence: 99%

Reversal of HO‐1 related cytoprotection with increased expression is due to reactive iron

1999

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It is often postulated that the cytoprotective nature of heme oxygenase (HO‐1) explains the inducible nature of this enzyme. However, the mechanisms by which protection occurs are not verified by systematic evaluation of the physiological effects of HO. To explain how induction of HO‐1 results in protection against oxygen toxicity, hamster fibroblasts (HA‐1) were stably transfected with a tetracycline response plasmid containing the full‐length rat HO‐1 cDNA construct to allow for regulation of gene expression by varying concentrations of doxycycline (Dox). Transfected cells were exposed to hyperoxia (95% O2/5% CO2) for 24 h and several markers of oxidative injury were measured. With varying concentrations of Dox, HO activity was regulated between 3‐ and 17‐fold. Despite cytoprotection with low (less than fivefold) HO activity, high levels of HO‐1 expression (greater than 15‐fold) were associated with significant oxygen cytotoxicity. Levels of non‐heme reactive iron correlated with cellular injury in hyperoxia whereas lower levels of heme were associated with cytoprotection. Cellular levels of cyclic GMP and bilirubin were not significantly altered by modification of HO activity, precluding a substantial role for activation of guanylate cyclase by carbon monoxide or for accumulation of bile pigments in the physiological consequences of HO‐1 overexpression. Inhibition of HO activity or chelation of cellular iron prior to hyperoxic exposure decreased reactive iron levels in the samples and significantly reduced oxygen toxicity. We conclude that there is a beneficial threshold of HO‐1 overexpression related to the accumulation of reactive iron released in the degradation of heme. Therefore, despite the ready induction of HO‐1 in oxidant stress, accumulation of reactive iron formed makes it unlikely that exaggerated expression of HO‐1 is a cytoprotective response.—Suttner, D. M., Dennery, P. A. Reversal of HO‐1 related cytoprotection with increased expression is due to reactive iron. FASEB J. 13, 1800–1809 (1999)

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“…These results are confirmed by its low fluorescence yields (Φ f < 5 × 10 −4 ), low yields of triplet states (<0.01), and the absence of efficient bleaching of the chromophore. 12,20,28,29 However, the relaxation processes of excited BR appear to be governed by complex mechanisms that are not fully known. 21 A few other studies at short time scales using femtosecond fluorescence upconversion measurements suggested that the initial deactivation process extends from the 100 fs to the 50 ps time scale, and the initial fast component was attributed to a conical intersection in the vicinity of the Franck−Condon region.…”

Section: Introductionmentioning

confidence: 99%

Computational Characterization of “Dark” Intermediates in the Ultrafast Deactivation of Photoexcited Bilirubin

Upadhyaya

2018

J. Phys. Chem. A

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The characterization of various intermediates in the ultrafast deactivation of photoexcited (Z,Z)-bilirubin-IXα was carried out using different computational methods. Various excited states of (Z,Z)-bilirubin-IXα and their respective vertical excitation energies were calculated using time-dependent density functional theory (TD-DFT) employing the Coulomb-attenuating method (CAM) combined with the B3LYP functional, which is known to predict accurate results on the charge transfer excitation process. Optimized geometries and absorption spectra were determined in chloroform solvent using the polarizable continuum model incorporating the integral equation formalism. The optimized geometries of different conformers of bilirubin (ZZ, ZE, EZ, and EE) along with their relative energies and vertical excitation energies were obtained. The geometry of the first excited state, S 1 , for the ZZ conformer was optimized using TD-DFT. The computational study suggests that excited-state intramolecular proton transfer (ESIPT) plays a major role in the deactivation process of (Z,Z)-bilirubin-IXα on a shorter time scale. The lactam−lactim tautomerism that arises from the ESIPT process gives rise to various intermediates of (Z,Z)-bilirubin-IXα. The computational results nicely corroborate the experimental findings available in the literature.

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Induction of Wavelength-Dependent Photochemistry in Bilirubins by Serum Albumin

Cited by 9 publications

References 26 publications

Wavelength-Dependent Photochemistry and Biological Relevance of a Bilirubin Dipyrrinone Subunit

Wavelength-Dependent Photochemistry and Biological Relevance of a Bilirubin Dipyrrinone Subunit

Reversal of HO‐1 related cytoprotection with increased expression is due to reactive iron

Computational Characterization of “Dark” Intermediates in the Ultrafast Deactivation of Photoexcited Bilirubin

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