Beitr�ge zur Chemie der Pyrrolpigmente, 21. Mitt.: R�ntgenphotoelektronenspektrometrische Untersuchungen des N1s-Niveaus von Gallenpigmenten

Falk, Heinz; Grubmayr, Karl; Thirring, K.; Gurker, N.

doi:10.1007/bf00913020

Cited by 8 publications

(2 citation statements)

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“…However, the X-ray crystallographic studies of verdins by Sheldrick [ 26 ] and BR by Bonnett [ 27 , 28 ] and others [ 29 , 30 , 31 , 32 ] confirmed the lactam structure, with both pigments showing the characteristic shorter amide C=O bond lengths. The lactam tautomer was doubly confirmed by Falk from X-ray photoelectron spectroscopy, with a focus on the end-ring nitrogens [ 33 ] and by 15 N-NMR for the pigments in solution [ 34 ].…”

Section: Introduction and Historical Notementioning

confidence: 99%

“…It is relevant to state that X-ray crystallography also revealed important aspects of the conformation of BV and BR. In the solid, the former adopts a porphyrin-like shape that is not planar but twisted into a helical lockwasher shape with a 16° dihedral angle pivoting on C-10 [ 33 , 37 ]. Thus, BV is intrinsically chiral, but the two enantiomeric helices, which easily interconvert, are equally present in isotropic solutions of BV and, consequently, exhibit no optical activity.…”

Section: Introduction and Historical Notementioning

confidence: 99%

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Insights into the Structures of Bilirubin and Biliverdin from Vibrational and Electronic Circular Dichroism: History and Perspectives

et al. 2023

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In this work we review research activities on a few of the most relevant structural aspects of bilirubin (BR) and biliverdin (BV). Special attention is paid to the exocyclic C=C bonds being in mostly Z rather than E configurations, and to the overall conformation being essentially different for BR and BV due to the presence or absence of the double C=C bond at C-10. In both cases, racemic mixtures of each compound of either M or P configuration are present in achiral solutions; however, imbalance between the two configurations may be easily achieved. In particular, results based on chiroptical spectroscopies, both electronic and vibrational circular dichroism (ECD and VCD) methods, are presented for chirally derivatized BR and BV molecules. Finally, we review deracemization experiments monitored with ECD data from our lab for BR in the presence of serum albumin and anesthetic compounds.

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Section: Introduction and Historical Notementioning

confidence: 99%

Section: Introduction and Historical Notementioning

confidence: 99%

Insights into the Structures of Bilirubin and Biliverdin from Vibrational and Electronic Circular Dichroism: History and Perspectives

et al. 2023

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ChemInform Abstract: CONTRIBUTIONS TO THE CHEMISTRY OF PYRROLE PIGMENTS, 21: X‐RAY PHOTOELECTRON SPECTROMETRIC INVESTIGATIONS OF THE N1S LEVEL OF BILE PIGMENTS

Falk¹,

Grubmayr²,

Thirring³

et al. 1979

Chemischer Informationsdienst

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Bilirubin Chemistry, Ionization and Solubilization by Bile Salts

Ostrow

Celic

1984

Hepatology

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Bilirubin is a linear tetrapyrrole whose conformation is affected by internal hydrogen bonds formed between the carboxyl side chains and dipyrromethenone rings. Structural variations include: constitutional isomerism of the vinyl or carboxyethyl side chains, geometric isomerism of the methene bridges, tautomerism of the lactam groups, conformational rotations about the central methylene bridge and ionization of one or both carboxyl groups. Aggregation of the dianion into dimers and multimers may occur. The pK,' values of the two carboxyl groups are affected greatly by the environment and may differ widely in micellar solutions like bile. Solubility of bilirubin in water is less than 1 nM at pH = 7 and about 0.1 at pH = 8. Nonetheless, it dissolves poorly in most lipid solvents, except for asymmetrical chloroalkanes. Hydrogen bond-breaking solvents, especially dimethyl sulfoxide, are most effective in solubilizing bilirubin. In bile salt solutions, solubility of bilirubin is well above the concentrations of unconjugated bilirubin found in normal human gallbladder bile, and is impaired by lecithin but unaffected by cholesterol. At physiological pH in bile salt solutions, bilirubin is predominantly in its monoanion form that binds readily to the micelles. In such solutions, addition of physiological concentrations of calcium precipitates calcium bilirubinate, leaving residual bilirubin concentrations of up to 15 rc.M in 50 mM taurocholate or close to the maximum bilirubin concentrations in normal bile. Studies in which disodium bilirubinate is dissolved in bile salt solutions and pH is adjusted to the physiological range reveal that metastable supersaturation with bilirubin may occur and that a mesophase may also form in the presence of lecithin, akin to that seen with cholesterol. These results form a basis for understanding the precipitation of calcium bilirubinate from bile during pigment gallstone formation.Bilirubin is a linear tetrapyrrole of the biladiene-a,c type, consisting of two asymmetrical dipyrromethenones connected by a methylene bridge (1) (Figure 1). In the natural 1x0-Z,Z isomer that predominates in uiuo, each dipyrrolic half-molecule carries a carboxyethyl side chain that might be expected to render the pigment a highly polar, ionized and water-soluble molecule at physiological pH values. However, in its fully protonated (diacid) form, each of the two carboxyl groups forms internal hydrogen bonds with the -C=O and two >NH in the dipyrromethenone rings in the opposite half of the molecule (2). Collectively, these two trios of hydrogen bonds stabilize the bilirubin molecule in a rigid conformation that resembles a ridge tile or partially folded book (2), in

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Beitr�ge zur Chemie der Pyrrolpigmente, 21. Mitt.: R�ntgenphotoelektronenspektrometrische Untersuchungen des N1s-Niveaus von Gallenpigmenten

Cited by 8 publications

References 14 publications

Insights into the Structures of Bilirubin and Biliverdin from Vibrational and Electronic Circular Dichroism: History and Perspectives

Insights into the Structures of Bilirubin and Biliverdin from Vibrational and Electronic Circular Dichroism: History and Perspectives

ChemInform Abstract: CONTRIBUTIONS TO THE CHEMISTRY OF PYRROLE PIGMENTS, 21: X‐RAY PHOTOELECTRON SPECTROMETRIC INVESTIGATIONS OF THE N1S LEVEL OF BILE PIGMENTS

Bilirubin Chemistry, Ionization and Solubilization by Bile Salts

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