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Your search keyword '"Torsion -- Analysis"' showing total 7 results
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7 results on '"Torsion -- Analysis"'

1. Mechanisms of exchange modulation in trimethylenemethane-type biradicals: the roles of conformation and spin density

Author

Shultz, David A., Fico, Rosario M., Jr., Hyoyoung Lee, Kampf, Jeff W., Kirschbaum, Kristin, Pinkerton, A. Alan, and Boyle, Paul D.

Subjects
Methyl groups -- Research, Methane -- Research, Torsion -- Analysis, Nitro compounds -- Atomic properties, Nitro compounds -- Magnetic properties, Electron spin, Chemistry
Abstract

A torsional dependence of electron spin-spin exchange coupling in trimethylenemethane (TMM)-type dinitroxide biradicals is described. This torsional dependence is compared with an analogous series of TMM-type bis(semiquinone) biradicals.

Published
2003

2. Ab initio study of the effects of torsion angles on carbon-13 nuclear magnetic resonance chemical shielding in N-formyl-L-alanine amide, N-formyl-L-valine amide, and some simple model compounds: applications to protein NMR spectroscopy

Author

Dios, Angel C. de and Oldfield, Eric

Subjects
Torsion -- Analysis, Proteins -- Research, Chemistry
Abstract

Gauge-including atomic orbital method is employed to study the influence of torsion angles on 13C NMR shielding in different amino compounds, which are related to the origin of nonequivalent chemical shifts, exhibited in proteins. Shielding studies are performed with helical and sheet conformations to find the influence of folding. Side chain conformations influence the coupling constants.

Published
1994

3. Torsional barriers in alpha-keto amides: model studies related to the binding site of FK506

Author

Bach, Robert D., Mintcheva, Iliana, Kronenberg, William J., and Schlegel, H. Bernhard

Subjects
Amides -- Analysis, Binding sites (Biochemistry) -- Analysis, Torsion -- Analysis, Biological sciences, Chemistry
Abstract

Methyl substituents on N,N-dimethyl-alpha-ketopropanamide reveal steric reactions. N, N-dimethyl-alpha-ketopropanamide moves away from planarity and causes the lack of a syn-conformer as a local minimum due to the interaction. Crystal geometry of FK506 reveals orthogonal orientation which shows a torsional profile and the size of the obstacle for C-C bond rotation. These features are similar in the compound due to the reaction. Easy exchange of the cis and trans structures for the amide bond in FK506 at ambient temperatures is revealed by the size of the C-N rotational obstacle in the compound.

Published
1993

4. Torsion potential in polydiacetylene: accurate computations on oligomers extrapolated to the polymer limit

Author

Sears, John S., Chance, Ronald R., and Bredas, Jean-Luc

Subjects
Acetylene -- Chemical properties, Acetylene -- Optical properties, Oligomers -- Structure, Oligomers -- Chemical properties, Optoelectronics -- Analysis, Torsion -- Analysis, Chemistry
Abstract

Computationally efficient, wave-function-based electronic structure methods on increasingly larger oligomers are used to obtain reliable estimates of the torsional barriers in model diacetylene oligomers. The results from the accurate exploration for the polymer limit values provide insight into the impact of polymer torsions upon the properties of polydiacetylenes.

Published
2010

5. Determination of molecular torsion angles using nuclear singlet relaxation

Author

Tayler, Michael C.D., Marie, Sabrina, Ganesan, A., and Levitt, Malcolm H.

Subjects
Carbenes -- Structure, Carbenes -- Chemical properties, Magnetization -- Analysis, Nuclear magnetic resonance spectroscopy -- Usage, Torsion -- Analysis, Chemistry
Abstract

The exponential relaxation time constant ([T.sub.S] of a nuclear singlet state is affected by the proximity of neighboring NMR-active nuclei. The sensitivity has provided a new way for determining torsional angles plus other molecular structural details in the isotropic solution phase.

Published
2010

6. Limits on variations in protein backbone dynamics from precise measurements of scalar couplings

Author

Vogeli, Beat, Jinfa Ying, Grishaev, Alexander, and Bax, Ad

Subjects
Scalar field theory -- Analysis, Protein biosynthesis -- Research, Torsion -- Analysis, Chemistry
Abstract

Various methods are employed for precise measurements of different scalar couplings, which are then used to study the limits on the variations of protein backbone dynamics. The analysis reveals that the positioning of hydrogens is the main factor that reduces the accuracy of the extraction of the torsion angle from the backbone.

Published
2007

7. Stereospecific measurements of the vicinal 1H-31P coupling constants for the diastereotopic C5' methylene protons in a DNA dodecamer with a 13C/2H doubly labeled residue. Conformational analysis of the torsion angle beta

Author

Tate, Shin-ichi, Kubo, Yoshihiro, Ono, Akira, and Kainosho, Masatsune

Subjects
Stereochemistry -- Analysis, Torsion -- Analysis, DNA -- Measurement, Chemistry
Abstract

A new spin-echo difference spectroscopy technique measures the (super 3)J(sub HP) coupling constant, applicable to DNA/RNA oligomers. It shows stereoselective deuteration at C5' with nearly twice the (5'S)-2H surplus than (5'R)-2H-labelled diastereomers. The vicinal (super 1)H-(super 31)P coupling constants for DNA dodecamer methylene protons are found, and torsion angle beta is also analyzed.

Published
1995

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