Microwave spectra of the six monodeuteriophenols. Molecular structure, dipole moment, and barrier to internal rotation of phenol

Pedersen, Thorvald; Larsen, N. W.; Nygaard, Lise

doi:10.1016/0022-2860(69)85029-5

Cited by 155 publications

(46 citation statements)

References 14 publications

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“…CNDO/S-CI calculations on isoalloxazine-phenol complexes were performed using the parameters and isoalloxazine molecular geometry from previous work [27,28]. The phenol molecular structure was taken from the literature [32,33].…”

Section: Methodsmentioning

confidence: 99%

On the Enigma of Old Yellow Enzyme's Spectral Properties

Eweg

Müller

Berkel

1982

European Journal of Biochemistry

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Old yellow enzyme (NADPH oxidoreductase) in the free and complexed state was thoroughly investigated by the following techniques : absorption, circular dichroism, fluorescence/phosphorescence and electron paramagnetic resonance spectroscopy and fluorescence/phosphorescence decay measurements, applied over a wide range of temperature (7 -293 K). The data obtained were interpreted by comparison with results from similar measurements on free FMN, existing spectral data on isoalloxazine model systems and theoretical data.The results clearly demonstrate the inadequacy of a simple phenolate-FMN donor-acceptor charge-transfer complex to explain the phenomena occurring upon the addition of phenols to old yellow enzyme. Instead it was found that the phenolate anion interferes strongly with an existing tight complex between FMN and the apoprotein, probably an H-bonded structure in which FMN is tautomerized and interacts with an L-chiral center. This is concluded from a separate electronic transition with an origin at 496 nm, thus far not recognized as such, and the circular dichroism observed.The emission is dominated by that of free FMN, although protein-bound FMN seems also to become luminescent in glassy solution at 143 K. A second fluorescence/phosphorescence emission appears upon excitation of both native and complexed old yellow enzyme in the ultraviolet. This emission is quenched by the addition of phenol to the enzyme, shows a large (3000-cm-') blue shift on going to a low-temperature glass and is tentatively assigned to excimers of nucleic acids. Long-wavelength excitation with a synchronously pumped, mode-locked Rhodamine 6-G dye laser revealed a third, extremely weak emission in both native old yellow enzyme and its complexes. It decays with a lifetime of about 3 ns at 143 K. Electron paramagnetic resonance spectra revealed the presence of a low amount of an unpaired spin in old yellow enzyme. Owing to an unusual relaxational behaviour it could only be observed below 15 K and, again, the signal was measured in both the native enzyme and its complexes. Possible assignment and consequences of this observation are discussed.In frozen aqueous solutions of the enzyme-phenolate complex, a phase transition was discovered at which the colour of the complex reverted to that of the native enzyme. Subsequent melting restored the original colour.The observed phenomena and existing literature data lead to the conclusion that the only model from which no apparent inconsistencies emerge is that of a very complicated network of hydrogen-bonded structures in the protein. These involve several, partly unknown, chromophores. Phenols interfere with this network, leading to the formation of the long-wavelength absorption band in old yellow enzyme.The spectral changes induced by the binding of a lowmolecular-weight compound to old yellow enzyme (NADPH oxidoreductase) were initially regarded to be sufficiently mysterious to refer to this unknown compound as 'regreening factor' [I]. After the identification of this 'regreening factor'...

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Section: Methodsmentioning

confidence: 99%

On the Enigma of Old Yellow Enzyme's Spectral Properties

Eweg

Müller

Berkel

1982

European Journal of Biochemistry

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“…They are obtained from the fit of microwave transitions given in ref. [61] to the Hamiltonian used in the study by Ratzer et al [15] in order to be based on the same model as the dimer rotational constants. The ground-state COM distance of the d 6 -d 6 cluster is calculated using the rotational constants from ref.…”

Section: Determination Of the Structurementioning

confidence: 99%

Determining the Intermolecular Structure in the S₀ and S₁ States of the Phenol Dimer by Rotationally Resolved Electronic Spectroscopy

Schmitt¹,

Böhm²,

Ratzer³

et al. 2006

ChemPhysChem

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The rotationally resolved UV spectra of the electronic origins of five isotopomers of the phenol dimer have been measured. The complex spectra are analyzed using a fitting strategy based on a genetic algorithm. The intermolecular geometry parameters have been determined from the inertial parameters for both electronic states and compared to the results of ab initio calculations. In the electronic ground state, a larger hydrogen-bond length than in the ab initio calculations is found together with a smaller tilt angle of the aromatic rings, which shows a more pronounced dispersion interaction. In the electronically excited state, the hydrogen-bond length decreases, as has been found for other hydrogen-bonded clusters of phenol, and the two aromatic rings are tilted less toward each other.

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“…The phenol molecule itself is planar in the vapor phase [35,36]. In case of two phenolic hydroxyl moieties the special position of their hydrogen atoms shown in Figure 1 is optimal in the CNDO/:!…”

Section: Con Formationmentioning

confidence: 98%

Biological response as a function of conformation, chirality, and electronic characteristics: A catecholamine study

Scharfenberg¹,

Sauer²

1980

Int J of Quantum Chemistry

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The hypothesis is introduced, that nonrigid drug molecules interact with biological receptors in a well-defined but unknown conformation that need not belong to an energy minimum. A verification of this assumption has to include a match of conformation and chirality. Even the different action of pairs of nonrigid enantiomers allow one to recognize uniquely the important role of conformations because flexible molecules are partially able to avoid wrong attachment to the receptor. According to a simple model, a monotonic relation between biological activity and rotational barriers (and/or torque constants) can be expected and, by means of rank correlation analysis of adrenergic activities, has been found, too. In order to apply the latter method, particularities concerning quantitative structureactivity analyses of nonrigid and/or chiral molecules are worked out. We optimized conformations by means of analytically calculated first partials of the energy and a quasi-Newton method. Using a convenient numerical method, it was shown that coplanar conformations of catecholamines are generally unstable. Moreover, C N D 0 / 2 proved to be a reliable method for conformational studies, in which rotations about conjugated bonds [l] are not considered.

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Microwave spectra of the six monodeuteriophenols. Molecular structure, dipole moment, and barrier to internal rotation of phenol

Cited by 155 publications

References 14 publications

On the Enigma of Old Yellow Enzyme's Spectral Properties

On the Enigma of Old Yellow Enzyme's Spectral Properties

Determining the Intermolecular Structure in the S₀ and S₁ States of the Phenol Dimer by Rotationally Resolved Electronic Spectroscopy

Biological response as a function of conformation, chirality, and electronic characteristics: A catecholamine study

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Microwave spectra of the six monodeuteriophenols. Molecular structure, dipole moment, and barrier to internal rotation of phenol

Cited by 155 publications

References 14 publications

On the Enigma of Old Yellow Enzyme's Spectral Properties

On the Enigma of Old Yellow Enzyme's Spectral Properties

Determining the Intermolecular Structure in the S0 and S1 States of the Phenol Dimer by Rotationally Resolved Electronic Spectroscopy

Biological response as a function of conformation, chirality, and electronic characteristics: A catecholamine study

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Determining the Intermolecular Structure in the S₀ and S₁ States of the Phenol Dimer by Rotationally Resolved Electronic Spectroscopy