Analysis of wavelength-dependent photoisomerization quantum yields in bilirubins by fitting two exciton absorption bands

Autofluorescence of liver tissue and bile: Organ functionality monitoring during ischemia and reoxygenation

“…The lower increase in the AF bilirubin emission may depend on multiple factors affecting bilirubin emission yield and its response to the microenvironment, including changes in the fractions of monomers, dimers/multimers and in the exciton splitting efficiency. This latter phenomenon depends on the sensitivity to the microenvironment of the molecular structure of bilirubin, acting as a bichromophore since it consists of two non completely symmetric pyrrole rings linked by a methylene bridge . Actually, it was already found that the emission yield of pure bilirubin is influenced by the medium, and that the presence of solubilizing agents such as albumin, or CTAB at pre‐ and supra‐micellar concentrations can affect the spectral shape.…”

“…Up to now, bilirubin photophysical properties have been investigated mainly in the visible spectral range, for accurate evaluation of its fractions in the blood, binding capacity of plasma components and perturbation effects from lipids or exogenous drugs, photoisomerization processes and pathogenesis of pigment gallstones in the bile, responding to the need to set‐up and improve diagnostic techniques and therapeutic procedures . Actually, bilirubin as a pure compound in solution with solubilizing agents can give rise to a fluorescence emission, that is solved by means of fitting analysis into two main emission bands, centered at about 515–523 and 570 nm.…”

Ultrafast deactivation of bilirubin: dark intermediates and two-photon isomerization

“…This leads to the helical configuration behind the optical activity reported in chiral environments. 9,11 The lowest excited states of BR are characterized by excitonic coupling of the two dipyrrinone halves, [12][13][14][15] so that the p-system extends to the whole molecule, despite the loss of conjugation in the central methylene group (Scheme 1). Upon optical excitation, BR deactivates rapidly by internal conversion with almost negligible quantum yields for all other possible deactivation routes at room temperature.…”

Modeling and Elucidation of the Kinetics of Multiple Consecutive Photoreactions AB 4 (4Φ) With Φ-order Kinetics. Application to the Photodegradation of Riboflavin

“…Over the last 50 years, a substantial number of compounds exhibiting wavelengthdependent quantum yields were reported despite their "normal" features in fluorescence. [44][45][46][47][48] This strongly points to a limitation of a universal applicability of Kasha's rule in photochemical processes, as suggested, in the late 1970s, by Turro et al 49 The literature…”