Bond Rotation

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Bruce P Branchaud - One of the best experts on this subject based on the ideXlab platform.

Jeanmarie Lehn - One of the best experts on this subject based on the ideXlab platform.

Yufen Zhao - One of the best experts on this subject based on the ideXlab platform.

  • investigation of the c n Bond Rotation of spirophosphorane carbamates by dynamic nmr and dft calculation
    Tetrahedron, 2015
    Co-Authors: Pei Zhao, Yanyan Wang, Miaomiao Peng, Yufen Zhao
    Abstract:

    Abstract Spirophosphorane carbamates are a new type of pentacoordinate phosphorus compounds. In order to explore internal Rotation, the dynamic 1H NMR, 31P NMR and molecular theory calculations were employed to investigate the Rotation barriers of the N–C( O) Bond of symmetrical and asymmetrical spirophosphorane carbamates. The Gibbs free activation, ΔG≠, was calculated by Eyring equation. The results showed that the Rotation barriers of spirophosphorane carbamates were about 16–18 kcal/mol, and the Rotation isomers coexisted at room temperature. Moreover, it was found that the benzyl group attached to amide nitrogen increased the C–N Bond Rotation barriers of spirophosphorane carbamates. Furthermore, the preferred conformation of spirophosphorane carbamates was presumed by density functional theory (DFT), and the conformation of solid state were also confirmed by X-ray diffraction analysis.

  • Investigation of the C–N Bond Rotation of spirophosphorane carbamates by dynamic NMR and DFT calculation
    Tetrahedron, 2015
    Co-Authors: Pei Zhao, Yanyan Wang, Miaomiao Peng, Yufen Zhao
    Abstract:

    Abstract Spirophosphorane carbamates are a new type of pentacoordinate phosphorus compounds. In order to explore internal Rotation, the dynamic 1H NMR, 31P NMR and molecular theory calculations were employed to investigate the Rotation barriers of the N–C( O) Bond of symmetrical and asymmetrical spirophosphorane carbamates. The Gibbs free activation, ΔG≠, was calculated by Eyring equation. The results showed that the Rotation barriers of spirophosphorane carbamates were about 16–18 kcal/mol, and the Rotation isomers coexisted at room temperature. Moreover, it was found that the benzyl group attached to amide nitrogen increased the C–N Bond Rotation barriers of spirophosphorane carbamates. Furthermore, the preferred conformation of spirophosphorane carbamates was presumed by density functional theory (DFT), and the conformation of solid state were also confirmed by X-ray diffraction analysis.

Lutz Greb - One of the best experts on this subject based on the ideXlab platform.

Klaas J Hellingwerf - One of the best experts on this subject based on the ideXlab platform.

  • on the involvement of single Bond Rotation in the primary photochemistry of photoactive yellow protein
    Biophysical Journal, 2011
    Co-Authors: Andreas D Stahl, Marijke Hospes, Kushagra Singhal, Ivo H M Van Stokkum, Rienk Van Grondelle, Marie Louise Groot, Klaas J Hellingwerf
    Abstract:

    Prior experimental observations, as well as theoretical considerations, have led to the proposal that C4-C7 single-Bond Rotation may play an important role in the primary photochemistry of photoactive yellow protein (PYP). We therefore synthesized an analog of this protein's 4-hydroxy-cinnamic acid chromophore, (5-hydroxy indan-(1E)-ylidene)acetic acid, in which Rotation across the C4-C7 single Bond has been locked with an ethane bridge, and we reconstituted the apo form of the wild-type protein and its R52A derivative with this chromophore analog. In PYP reconstituted with the Rotation-locked chromophore, 1), absorption spectra of ground and intermediate states are slightly blue-shifted; 2), the quantum yield of photochemistry is ∼60% reduced; 3), the excited-state dynamics of the chromophore are accelerated; and 4), dynamics of the thermal recovery reaction of the protein are accelerated. A significant finding was that the yield of the transient ground-state intermediate in the early phase of the photocycle was considerably higher in the Rotation-locked samples than in the corresponding samples reconstituted with p-coumaric acid. In contrast to theoretical predictions, the initial photocycle dynamics of PYP were observed to be not affected by the charge of the amino acid residue at position 52, which was varied by 1), varying the pH of the sample between 5 and 10; and 2), site-directed mutagenesis to construct R52A. These results imply that C4-C7 single-Bond Rotation in PYP is not an alternative to C7=C8 double-Bond Rotation, in case the nearby positive charge of R52 is absent, but rather facilitates, presumably with a compensatory movement, the physiological Z/E isomerization of the blue-light-absorbing chromophore.