Topic
Dihedral angle
About: Dihedral angle is a research topic. Over the lifetime, 15718 publications have been published within this topic receiving 174904 citations.
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TL;DR: In this article, the ground state splitting was found to be 11.44 cm-1, and this, used with the recently reported torsion at 317 cm−1, yields the barriers hindering internal rotation.
Abstract: Several hydrogen peroxide infrared absorption bands have been obtained under 0.2 cm—1 resolution. They demonstrate both doubling due to internal rotation and effects due to the inertial asymmetry. The ground‐state rotational constants are found to be: A″=10.068 cm—1, B″=0.8740, C″=0.8384. These parameters indicate a wide dihedral angle for H2O2, as proposed in the following structure: OO bond=1.475 A, OH bond=0.950 A, dihedral angle=119.8°, and OOH angle=94.8°.The constants are applied to the microwave data for H2O2 and the deuterated species. The ground‐state splitting is found to be 11.44 cm—1, and this, used with the recently reported torsion at 317 cm—1, yields the barriers hindering internal rotation. They are Vcis=1300 cm—1 and Vtrans=300 cm—1. A simple correlation of the infrared doublings is attempted.
274 citations
TL;DR: The peptide's structure was calculated by means of simulated annealing and a newly developed protocol that ensures that all of conformational space, consistent with the structural constraints, is searched completely, resulting in a high-quality structure that has thus far not been amenable to single-crystal diffraction studies.
Abstract: The three-dimensional structure of the chemotactic peptide N-formyl-l-Met-l-Leu-l-Phe-OH was determined by using solid-state NMR (SSNMR). The set of SSNMR data consisted of 16 (13)C-(15)N distances and 18 torsion angle constraints (on 10 angles), recorded from uniformly (13)C,(15)N- and (15)N-labeled samples. The peptide's structure was calculated by means of simulated annealing and a newly developed protocol that ensures that all of conformational space, consistent with the structural constraints, is searched completely. The result is a high-quality structure of a molecule that has thus far not been amenable to single-crystal diffraction studies. The extensions of the SSNMR techniques and computational methods to larger systems appear promising.
266 citations
TL;DR: In this article, a three-dimensional structure of two carbon nanotubes (CN) joined by a connecting region containing a pentagon and heptagon pair is given by the use of a projection method.
Abstract: A three-dimensional structure of two carbon nanotubes (CN) joined by a connecting region containing a pentagon and heptagon pair is given by the use of a projection method. The connecting joint is uniquely determined for the given two chiral vectors of CN by a vector which defines a three-dimensional dihedral angle. The tunneling conductance is calculated for a metal-metal CN junction and a metal-semiconducting CN junction. The calculated results clearly show that these junctions work as the smallest semiconductor devices.
265 citations
TL;DR: The conformation of the 7-membered hydrogen-bonded ring of the dipeptides has been elucidated and an empirically found stereochemical dependence of the constant 3 J NHCH upon the dihedral angle θ of the fragment has served as basis for discussing the possible conformations of the extended form of the Dipeptide molecules in polar solvents.
261 citations
TL;DR: The effects of different non-bonded parameters of force fields for NMR structure calculation on the quality of the resulting NMR solution structures were investigated using Interleukin 4 as a model system and optimal parameters are available in the new version of the PARALLHDG force field.
Abstract: The effects of different non-bonded parameters of force fields for NMR structure calculation on the quality of the resulting NMR solution structures were investigated using Interleukin 4 as a model system. NMR structure ensembles were calculated with an ab initio protocol using torsion angle dynamics. The calculations were repeated with five different non-bonded energy functions and parameters. The resulting ensembles were compared with the available X-ray structures, and their quality was assessed with common structure validation programs. In addition, the impact of torsion angle restraints and dihedral energy terms for the sidechains and the backbone was studied. The further improvement of the quality by refinement in explicit solvent was demonstrated. The optimal parameters, including those necessary for water refinement, are available in the new version of the PARALLHDG force field.
261 citations