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Angle torsional

Spectroscopists sometimes use additional terms in their Fourier series expansion to describe torsional properties in molecules. We have not found any [Pg.87]

In an extension to experiments which measure internuclear distances, Levitt and co-workers and Griffin and co-workers have presented ingenious methods which allow the measurement of torsional angles [148, 149]. The methods involve the creation of MQC between a pair of nuclei (selective isotopic labelling is required), which may be homonuclear, e. g. or heteronudear, e. g. A spin- [Pg.312]


Atomistically detailed models account for all atoms. The force field contains additive contributions specified in tenns of bond lengtlis, bond angles, torsional angles and possible crosstenns. It also includes non-bonded contributions as tire sum of van der Waals interactions, often described by Lennard-Jones potentials, and Coulomb interactions. Atomistic simulations are successfully used to predict tire transport properties of small molecules in glassy polymers, to calculate elastic moduli and to study plastic defonnation and local motion in quasi-static simulations [fy7, ( ]. The atomistic models are also useful to interiDret scattering data [fyl] and NMR measurements [70] in tenns of local order. [Pg.2538]

The first study in which a full CASSCE treatment was used for the non-adiabatic dynamics of a polyatomic system was a study on a model of the retinal chromophore [86]. The cis-trans photoisomerization of retinal is the primary event in vision, but despite much study the mechanism for this process is still unclear. The minimal model for retinal is l-cis-CjH NHj, which had been studied in an earlier quantum chemisti7 study [230]. There, it had been established that a conical intersection exists between the Si and So states with the cis-trans defining torsion angle at approximately a = 80° (cis is at 0°). Two... [Pg.305]

The second method for representing a molecule in 3D space is to use internal coordinates such as bond lengths, bond angles, and torsion angles. Internal coordinates describe the spatial arrangement of the atoms relative to each other. Figure 2-91 illustratc.s thi.s for 1,2-dichlorocthanc. [Pg.93]

A set of rules determines how to set up a Z-matrix properly, Each line in the Z-matiix represents one atom of the molecule. In the first line, atom 1 is defined as Cl, which is a carbon atom and lies at the origin of the coordinate system. The second atom, C2, is at a distance of 1.5 A (second column) from atom 1 (third column) and should always be placed on one of the main axes (the x-axis in Figure 2-92). The third atom, the chlorine atom C13, has to lie in the xy-planc it is at a distanc e of 1.7 A from atom 1, and the angle a between the atoms 3-1-2 is 109 (fourth and fifth columns). The third type of internal coordinate, the torsion angle or dihedral r, is introduced in the fourth line of the Z-matiix in the sixth and seventh column. It is the angle between the planes which arc... [Pg.93]

Figure 2-91. Internal coordinates of 1,2-dichloroethane bond lengths and r2, bond angle a, and torsion angle r. Figure 2-91. Internal coordinates of 1,2-dichloroethane bond lengths and r2, bond angle a, and torsion angle r.
Spanned by tbc atoms 4, 2, and 1, and 2, 1, and 3 (tlic ry-planc), Except of the first three atoms, each atom is described by a set of three internal coordinates a distance from a previously defined atom, the bond angle formed by the atom with two previous atoms, and the torsion angle of the atom with three previous atoms. A total of 3/V - 6 internal coordinates, where N is the number of atoms in the molecule, is required to represent a chemical structure properly in 3D space. The number (,3N - 6) of internal coordinates also corresponds to the number of degrees of freedom of the molecule. [Pg.94]

Figure 2-102. Dependence of the potential energy ctirve of n-butane on the torsion angle r between carbon atoins C2 and C3. Figure 2-102. Dependence of the potential energy ctirve of n-butane on the torsion angle r between carbon atoins C2 and C3.
Usually, two conformations are regarded as geometrically different if their minimized RMS deviation is equal to or larger than 0.3 A in Cartesian space RMSx z)> or 30 " in torsion angle space (RMSja). respectively. [Pg.108]

Figure 2-107. Derivation of the torsion angle library (TA Library). Figure 2-107. Derivation of the torsion angle library (TA Library).
Figure 2-108. Derivation of a syrMbolic potential energy function from the torsion angle distribution of a torsion fragment. Figure 2-108. Derivation of a syrMbolic potential energy function from the torsion angle distribution of a torsion fragment.
Figure 2-108 shows the correspondence between a histogram and the derived empirical energy function for the torsion angle fragment C-N H)-C(H)(H -C. [Pg.111]

Another way is to define an improper torsion angle e- (for atoms 1-2-3-4 in Figure 7-11 in combination with a potential lihe V((r- = fc l-cos2fi.-), which has its minima at <> = 0 and 7t. This of course implies the risk that, if the starting geometry is far from reality, the optimi2 ation will perhaps lead to the wrong local minimum. [Pg.344]

You can include geometric restraints—for interatomic distances, bond angles, and torsion angles—in any molecular dynamics calculation or geometry optim i/.ation. Here are some applications of restrain ts ... [Pg.81]

Evalii atm g average distances, angles, and torsion angles, pins their deviations, can facilitate understanding of detailed molecular properties and functional characteristics. [Pg.87]

Example Yon can monitor improper torsion angles to determine wh ich side of a substrate m olecn le faces the active site of a protein. Select three atoms on the substrate molecule and a fourth in the active site. These atom s define an improper torsion angle. Save th is selection as a named selection. Then observe a plot of this improper torsion angle (in the Molecular Dynam ics Results dialog... [Pg.87]


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Amino acid side chains torsion angles

Amino acids torsion angles

Analysis and Torsion Angles (Bucourt)

Angle dihedral torsion

Anomeric effect torsional angles

Backbone torsion angle

Backbone torsion angles molecular dynamics

Backbone torsion angles restraints

Bond and torsion angles

Butane torsional angle

Cellulose glycosidic torsion angles

Chemical shifts torsion angles with

Conformations, anti torsional angles

Constraints torsion angle

Coupling constants torsion angles

Crystal structures, torsion angle pattern

Dihedral angle torsions, interactions

Disaccharides torsional angles

Endocyclic torsion angles

Ethane torsion angles

Ethane, bond angles torsional strain

Four and More Torsion Angles

Gauche torsion angles

Generalized torsional angle

Glycosidic torsion angle fluctuations

Glycosidic torsion angle, variable

Helix torsion angles

Ideal torsion angle

Improper torsional angle

Internal torsion angle

Karplus relationship, determination torsional angles

Loop Prediction with Torsion Angle Sampling

Main chain torsion angles

Molecular torsion angle deformation

N-C torsional angle

Nucleoside torsion angles

Peptide structure torsion angles of, table

Peptide torsion angles

Polymers torsional angle

Polypeptide torsion angles

Potential energy as a function of torsion angle for ethane

Proline rings, torsion angles

Protein torsion angle

Ring torsion angle

Stereoisomerism torsional angles

Strain torsional angle deformation

Structure, three-dimensional torsional angles

Three Torsion Angles

Toluene Torsional angles

Topology of proteins Torsion angles

Torsion Angle Concept in Conformational Analysis (Bucourt)

Torsion Angle Constraints Stereochemical Searching

Torsion Angle Constraints from Chemical Shifts

Torsion Angle Constraints from Scalar Coupling Constants

Torsion Angle Library

Torsion angl

Torsion angl

Torsion angle

Torsion angle

Torsion angle convention

Torsion angle deformation

Torsion angle determination

Torsion angle driver

Torsion angle dynamics

Torsion angle flexibility

Torsion angle fluctuations

Torsion angle force constants

Torsion angle functions

Torsion angle molecular

Torsion angle space

Torsion angle, chain conformation geometry

Torsion angles What are they

Torsion angles conformations

Torsion angles energy calculations

Torsion angles linkages

Torsion angles molecular dynamics

Torsion angles nucleic acid backbones

Torsion angles parameters

Torsion angles patterns, angle distributions

Torsion angles peptide bond

Torsion angles shifts

Torsion angles variation

Torsion angles, and

Torsion angles, cellulosics

Torsion angles, definition

Torsion angles, hydroperoxides

Torsion angles, internal degrees

Torsion angles, internal degrees freedom

Torsion angles, peptide bond side-chain

Torsion/torsional angle/bend

Torsional angle change

Torsional angle distribution

Torsional angle driver

Torsional angle energy function

Torsional angle parameters

Torsional angle rotation

Torsional angle, definition

Torsional angles Subject

Torsional angles proper

Torsional angles, molecular

Torsional bond angles

Trans torsion angles

Two Torsion Angles

Variation with torsion angle

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