Optical activity and stereochemistry of linear oligopyrroles and bile pigments

Boiadjiev, Stefan E.; Lightner, David A.

doi:10.1016/s0957-4166(99)00037-3

Cited by 101 publications

(49 citation statements)

References 132 publications

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“…1) of BR was increased by complexation with BSA. 15,16 This means that the (P+) conformation was interconverted to the (M-) conformation on BSA. At this time the molecular structure of BR was altered, as shown by changes in not only the dihedral angle and orbit overlap, 3,4 but also hydrogen bonds, as shown in Fig earlier stage, the induced CD spectra showed no obvious signals more than noises, which might suggest that the complexation interconverting (P+) to (M-) enantiomer is so slow at the interface that the chiral equilibrium between the (M+) and (P-) conformations was not shifted at this stage, though chloroform can be bound to BSA and may alter the complexation rate between BR and BSA at the interface.…”

Section: Spectroscopic Measurementsmentioning

confidence: 99%

“…5 There are an interplanar dihedral angle (θ) and a small π-orbital overlap between both dipyrrinones of the BR molecule so as to interact through their locally excited states by resonance splitting (electrostatic interaction of the local electric dipole transition moments), states. 15,16 According to the exciton chirality rule, 15,16 dipyrrinone-dipyrrinone intramolecular exciton interactions (exciton coupling) coming from either of the BR conformation of (P+) and (M-) can generate CD spectra with opposite signs. It is possible that the equilibrium racemic state is broken and an induced optical activity can be generated, [3][4][5][6][7][8] because either enantiomer of the (P+) and (M-) forms of BR binds with an external chiral protein, such as BSA.…”

Section: Introductionmentioning

confidence: 99%

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Resonance Raman Spectroscopic Study on Chiral Aggregation of Bilirubin-Bovine Serum Albumin Complex Formed at Liquid/Liquid Interface

Yin

Watarai

2007

ANAL. SCI.

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Resonance Raman spectroscopy assisted by centrifugal liquid membrane/circular dichroism (CLM-CD) and UV/Vis absorption spectroscopies was applied to measure the binding state of bilirubin (BR) in the complex with bovine serum albumin (BSA) formed at a heptane/water interface. The bisignate Cotton effects in the interfacial CD spectra and the red shift and linewidth increase of the BR absorption band around 450 nm indicated the formation of the BR-BSA complex at the interface and the chiral conversion of BR molecules in the aggregates. The resonance Raman spectra of BR observed at the interface suggested that the interfacial BR-BSA complex formed during the initial 15 min after the contact of the two phases had a similar structure with that in solution, but after 15 min were forming aggregates coexisting with solid micro-particles. These experimental results strongly suggested that the chiral interconversion of BR from (P+) conformation to (M-) conformation in the interfacial complex was accompanied by aggregation of the BR-BSA complexes. In the present study, resonance Raman microscopic spectrometry was proved to be highly useful for characterizing the solid like aggregate formed at the liquid/liquid interface. 3 The dashed lines show intramolecular hydrogen bondings that link the dipyrrinones to opposing propionic acids. θ denotes the dihedral angle (see the text for details).

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Section: Spectroscopic Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Resonance Raman Spectroscopic Study on Chiral Aggregation of Bilirubin-Bovine Serum Albumin Complex Formed at Liquid/Liquid Interface

Yin

Watarai

2007

ANAL. SCI.

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“…1) and correlations between pigment propeller stereochemistry (M and P) and CD spectroscopy have been drawn on the basis of exciton coupling theory. 8,9,12,18,22 …”

Section: Exciton Chiralitymentioning

confidence: 99%

“…4) and the predictions of the exciton chirality rule. 8,9,12,18,19,22 Curiously, when ammonia gas is added to a solution of 1 in CHCl 3 the Cotton effect magnitudes decrease with increasing NH 3 concentration. At sufficiently high concentration the Cotton effect signs invert and the intensity grows, reaching a plateau where the magnitudes are comparable to or greater than those of 1 in pure CHCl 3 .…”

Section: Chirality Inversionmentioning

confidence: 99%

Chirality inversion in the bilirubin molecular exciton

Boiadjiev

Lightner

2001

Chirality

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The bichromophoric pigment bilirubin acts as a molecular exciton in its UV-visible and circular dichroism (CD) spectroscopy. In both polar and nonpolar solvents, an optically active analog, (beta R,beta 'R)-dimethylmesobilirubin-XIII alpha (1), exhibits intense bisignate CD Cotton effects in the region of its long wavelength UV-vis absorption near 400 nm: Delta epsilon(434)(max) + 337, Delta epsilon(389)(max) - 186 (CHCl(3)), and Delta epsilon(431)(max) + 285, Delta epsilon(386)(max) - 177 (CH(3)OH). However, introduction of an amine into a CHCl(3) solution of 1 causes the Cotton effect signs to become inverted, e.g., after addition of NH(3), Delta epsilon(433)(max) - 345, Delta epsilon(389)(max) + 243, and after addition of ethylene diamine, Delta epsilon(435)(max) - 420, Delta epsilon(390)(max) + 299. The sign inversions imply inversion of molecular chirality of the bilirubin and the phenomenon appears to be general for amines, including alpha,omega-diamines. 1,8-Diaminooctane was found to be more effective than longer or shorter chain analogs in producing CD sign inversion.

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“…Remote constraints between atoms that are not directly linked to each other can occur within a single molecule that may give rise to conformational chirality. 2 Secondary interactions between proteins and ligands induce chirality in configurationally achiral molecules. 3,4 Furthermore, secondary chemical forces may create a handed property by aligning neighboring chiral molecules.…”

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confidence: 99%

Supramolecular exciton chirality of carotenoid aggregates

et al. 2003

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The conventional organic chemistry concept of chirality relates to single molecules. This article deals with cases in which exciton chirality is generated by the interaction of associated carotenoids. The handed property responsible for exciton signals in these systems is due to the alignment of neighboring molecules held together by secondary chemical forces. Their mutual positions are characterized by the overlay angle. Experimental manifestation is obtained by spectroscopic studies on carotenoid aggregates. Compared to molecular spectra, both UV/visible and circular dichroism spectroscopic observations reveal modified absorption bands and induced Cotton effects of opposite sign (exciton couplets), respectively. A new term, "supramolecular exciton chirality," is suggested for these phenomena, allowing the detection of weak chemical interactions not readily accessible for experimental studies, although highly important in the mechanism of biological processes.

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Optical activity and stereochemistry of linear oligopyrroles and bile pigments

Cited by 101 publications

References 132 publications

Resonance Raman Spectroscopic Study on Chiral Aggregation of Bilirubin-Bovine Serum Albumin Complex Formed at Liquid/Liquid Interface

Resonance Raman Spectroscopic Study on Chiral Aggregation of Bilirubin-Bovine Serum Albumin Complex Formed at Liquid/Liquid Interface

Chirality inversion in the bilirubin molecular exciton

Supramolecular exciton chirality of carotenoid aggregates

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