Karplus equation for NMR coupling constants
E467020
The Karplus equation for NMR coupling constants is an empirical relationship that links three-bond scalar coupling values between nuclei to the dihedral angle between them, enabling the determination of molecular conformations from NMR data.
Statements (49)
| Predicate | Object |
|---|---|
| instanceOf |
NMR parameter correlation
ⓘ
conformational analysis tool ⓘ empirical relationship ⓘ |
| appliesTo |
H–C–C–H dihedral angles
ⓘ
three-bond couplings across a single bond ⓘ vicinal proton–proton couplings ⓘ |
| assumes |
coupling constant is periodic in dihedral angle
ⓘ
maximum coupling near 180 degrees ⓘ minimum coupling near 90 degrees ⓘ |
| calibratedBy |
experimental NMR data
ⓘ
quantum chemical calculations ⓘ |
| category |
NMR structural restraints
ⓘ
empirical structure–property relationships ⓘ |
| dependsOn |
dihedral angle θ between coupled nuclei
ⓘ
empirical parameters A, B, and C ⓘ |
| describes |
3J spin–spin coupling constants
ⓘ
three-bond scalar coupling constants ⓘ |
| field |
nuclear magnetic resonance spectroscopy
ⓘ
physical chemistry ⓘ structural chemistry ⓘ |
| hasVariant |
Karplus equation for 3J(HN,Hα) in proteins
NERFINISHED
ⓘ
Karplus-like equations for heteronuclear couplings ⓘ generalized Karplus equation NERFINISHED ⓘ |
| historicalContext | introduced in the 1950s ⓘ |
| involves |
cosine-squared angular dependence
ⓘ
periodicity of 360 degrees in θ ⓘ |
| limitation |
accuracy decreases for highly substituted systems
ⓘ
does not explicitly include dynamic averaging ⓘ parameters are system-dependent ⓘ |
| mathematicalForm | J = A cos²(θ) + B cos(θ) + C ⓘ |
| namedAfter | Martin Karplus NERFINISHED ⓘ |
| parameter |
A
ⓘ
B ⓘ C ⓘ |
| predicts | magnitude of 3J coupling constants ⓘ |
| relatedTo |
J-coupling based structure refinement
ⓘ
Ramachandran plot analysis in proteins ⓘ |
| relates |
3J coupling constants to dihedral angles
ⓘ
NMR coupling constants to molecular conformation ⓘ |
| sensitivityTo |
bond geometry
ⓘ
electronegativity of substituents ⓘ substituent effects ⓘ |
| usedFor |
conformational analysis of organic molecules
ⓘ
determining dihedral angles from NMR data ⓘ peptide and protein structure determination ⓘ protein backbone torsion angle estimation ⓘ validating molecular dynamics simulations ⓘ |
| usedIn |
solid-state NMR adaptations
ⓘ
solution-state NMR spectroscopy ⓘ |
Referenced by (1)
Full triples — surface form annotated when it differs from this entity's canonical label.