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

Abstract

In model systems, we have studied side effects which may be induced by light during phototherapy of hyperbilirubinemia (jaundice) in newborn infants, with the aim of reducing the Z,Z-bilirubin IXα (Z,Z-BR IXα) level. We have shown that the sensitizing effect of Z,Z-BR IXα, localized at strong binding sites of the human serum albumin (HSA) macromolecule, is primarily directed at the amino acid residues of the carrier protein and does not involve the molecules of the enzyme (lactate dehydrogenase (LDH)) present in the buffer solution. The detected photodynamic damage to LDH is due to sensitization by bilirubin photoisomers, characterized by lower HSA association constants and located (in contrast to native Z,Z-BR IXα) on the surface of the HSA protein globule. Based on study of the spectral characteristics of the photoproducts of Z,Z-BR IXα and comparison of their accumulation kinetics in solution and the enzyme photo-inactivation kinetics, we concluded that the determining role in sensitized damage to LDH is played by lumirubin. The photosensitization effect depends on the wavelength of the radiation used for photoconversion of bilirubin. When (at the beginning of exposure) we make sure that identical numbers of photons are absorbed by the pigment in the different spectral ranges, the side effect is minimal for radiation corresponding to the long-wavelength edge of the bilirubin absorption band. We have shown that for a bilirubin/HSA concentration ratio >2 (when some of the pigment molecules are sorbed on the surface of the protein globule), the bilirubin can act as a photosensitizing agent for the enzyme present in solution. We discuss methods for reducing unfavorable side effects of light on the body of newborn infants during phototherapy of hyperbilirubinemia.Key words: hyperbilirubinemia of newborns, bilirubin, lumirubin, photoisomerization of bilirubin, photoproducts of bilirubin, photodynamic damage, absorption and fluorescence spectra.

Noninvasive, continuous fluorescence monitoring of bilirubin photodegradation

“…33 Thus, the distance between neighboring albumin globules' surfaces is comparable to the size of a globule itself (B10 nm). It is known that fluorescence lifetime for HSA-bound 4Z,15Z-bilirubin is scaled to the picosecond range, 34,35 meaning that there can be no nonradiative energy transfer through a distance of 10 nm, 36 and the main mechanism of energy transfer is reabsorption of fluorescent light.…”

Easy Diagnosis of Jaundice: A Smartphone-Based Nanosensor Bioplatform Using Photoluminescent Bacterial Nanopaper for Point-of-Care Diagnosis of Hyperbilirubinemia

“…The unconjugated isomer is a water insoluble form of BR that is stabilized via intramolecular H-bonding. In the presence of blue light, the configurational isomerization occurs and lumirubins are formed. − Since BR is an oxygen-sensitive molecule, in the presence of dissolved oxygen in the samples, the photooxidation process occurs following the photoisomerization and subsequently the polar, colorless, and water-soluble oxidation products are formed (Scheme B). − Through this photoreaction, the dipyrrinone chromophore gets free from intermolecular hydrogen bonds and the molecule breaks into smaller pieces. , Although this photoisomerization reaction occurs slowly in the body, at the microfluidic level and thin layers it can change faster.…”

Fabrication of the Enzyme‐less Voltammetric Bilirubin Sensor Based on Sol‐gel Imprinted Polymer

“…However, when bonded to its natural carrier, albumin, the quantum yield increases in aqueous solution. The bilirubinÀ albumin complex has a fluorescence emission of 520 nm [10]. Several reports of bilirubin measurements are available with fluorimetric methods [11][12][13][14][15][16][17].…”