Back to Search Start Over

Highly Emissive Biological Bilirubin Molecules : Shedding New Light on the Phototherapy Scheme

Authors :
El-Zohry, Ahmed M.
Diez-Cabanes, Valentin
Pastore, Mariachiara
Ahmed, Taha
Zietz, Burkhard
El-Zohry, Ahmed M.
Diez-Cabanes, Valentin
Pastore, Mariachiara
Ahmed, Taha
Zietz, Burkhard
Publication Year :
2021

Abstract

Bilirubin (BR) is the main end-product of the hemoglobin catabolism. For decades, its photophysics has been mainly discussed in terms of ultrafast deactivation of the excited state in solution, where, indeed, BR shows a very low green emission quantum yield (EQY), 0.03%, resulting from an efficient nonradiative isomerization process. Herein, we present, for the first time, unique and exceptional photophysical properties of solid-state BR, which amend by changing the type of crystal, from a closely packed alpha crystal to an amorphous loosely packed beta crystal. BR alpha crystals show a very bright red emission with an EQY of ca. 24%, whereas beta crystals present, in addition, a low green EQY of ca. 0.5%. By combining density functional theory (DFT) calculations and time-resolved emission spectroscopy, we trace back this dual emission to the presence of two types of BR molecules in the crystal: a stiff monomer, M1, distorted by particularly strong internal H-bonds and a floppy monomer, M2, having a structure close to that of BR in solution. We assign the red strong emission of BR crystals to M1 present in both the alpha and beta crystals, while the low green emission, only present in the amorphous (beta) crystal, is interpreted as M2 emission. Efficient energy-transfer processes from M2 to M1 in the closely packed a crystal are invoked to explain the absence of the green component in its emission spectrum. Interestingly, these unique photophysical properties of BR remain in polar solvents such as water. Based on these unprecedented findings, we propose a new model for the phototherapy scheme of BR inside the human body and highlight the usefulness of BR as a strong biological fluorescent probe.

Details

Database :
OAIster
Notes :
English
Publication Type :
Electronic Resource
Accession number :
edsoai.on1269459375
Document Type :
Electronic Resource
Full Text :
https://doi.org/10.1021.acs.jpcb.1c05308