Solution Structure of Mesobilirubin XIIIa Bridged Between the Propionic Acid Substituents [1]

Crusats, Joaquim; Delgado, Ana; Farrera, Joan‐Anton; Rubires, Raimon; Ribó, Josep M.

doi:10.1007/pl00013483

Cited by 2 publications

(1 citation statement)

References 6 publications

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“…When dissolved in aprotic organic solvents, free PCB adopts mainly a helically coiled form with a ZZZsss-conformation (Structure 1 in Fig. 2) (11)(12)(13)(14)(15)(16). In this neutral form, pyrrole ring B is not protonated but shares the proton with ring C, allowing an internal hydrogen-bonding network to stabilize this conformation.…”

Section: Introductionmentioning

confidence: 99%

Role of the Protein Cavity in Phytochrome Chromoprotein Assembly and Double‐bond Isomerization: A Comparison with Model Compounds

Rohmer

Lang

Gärtner

et al. 2010

Photochem & Photobiology

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Difference patterns of (13)C NMR chemicals shifts for the protonation of a free model compound in organic solution, as reported in the literature (M. Stanek, K. Grubmayr [1998] Chem. Eur. J.4, 1653-1659), were compared with changes in the protonation state occurring during holophytochrome assembly from phycocyanobilin (PCB) and the apoprotein. Both processes induce identical changes in the NMR signals, indicating that the assembly process is linked to protonation of the chromophore, yielding a cationic cofactor in a heterogeneous, quasi-liquid protein environment. The identity of both difference patterns implies that the protonation of a model compound in solution causes a partial stretching of the geometry of the macrocycle as found in the protein. In fact, the similarity of the difference pattern within the bilin family for identical chemical transformations represents a basis for future theoretical analysis. On the other hand, the change of the (13)C NMR chemical shift pattern upon the Pr --> Pfr photoisomerization is very different to that of the free model compound upon ZZZ --> ZZE photoisomerization. Hence, the character of the double-bond isomerization in phytochrome is essentially different from that of a classical photoinduced double-bond isomerization, emphasizing the role of the protein environment in the modulation of this light-induced process.

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Section: Introductionmentioning

confidence: 99%

Role of the Protein Cavity in Phytochrome Chromoprotein Assembly and Double‐bond Isomerization: A Comparison with Model Compounds

Rohmer

Lang

Gärtner

et al. 2010

Photochem & Photobiology

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On the aggregation of bilirubinoids in solution as evidenced by VCD and ECD spectroscopy and DFT calculations

et al. 2017

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Vibrational and electronic circular dichroism (VCD and ECD) spectra of 3 optically active bilirubin analogs with propionic acid groups replaced by (1) 1-(S)-methylpropyl groups, (2) 3-acetoxy-1-(S)-methylpropyl groups, and (3) 1-(S)-2-(R)-dimethyl-2-(methoxycarbonyl)ethyl groups have been recorded at different concentrations in chloroform. The aliphatic chains attached to C-8 and C-12 of the 3 chosen mesobilirubins were modified so as to possess no OH group. The variation of the VCD spectra with concentration is consistent with the formation of dimers at high concentration. Density functional theory and time-dependent density functional theory calculations on monomeric and dimeric forms support such a conclusion. Comparing with previous VCD (ECD) and IR (UV) studies of other mesobilirubin molecules, it is concluded that here, the key feature for aggregation is the missing OH groups on the propionic acid chains. The latter, in synergy with the polar groups of lactam moieties, appear to be involved in intramolecular phenomena and thus favor monomeric forms. Investigation of ECD and UV spectra of the same compounds in mixed DMSO/chloroform solutions provide further clues to the proposed picture.

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Solution Structure of Mesobilirubin XIIIa Bridged Between the Propionic Acid Substituents [1]

Cited by 2 publications

References 6 publications

Role of the Protein Cavity in Phytochrome Chromoprotein Assembly and Double‐bond Isomerization: A Comparison with Model Compounds

Role of the Protein Cavity in Phytochrome Chromoprotein Assembly and Double‐bond Isomerization: A Comparison with Model Compounds

On the aggregation of bilirubinoids in solution as evidenced by VCD and ECD spectroscopy and DFT calculations

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