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Scalar J-Coupling Restraints

X-PLOR has an energy term for fitting scalar couplings to the Karplus relation.

$\begin{displaymath} J = A \cos^2 (\theta+P) + B \cos (\theta+P) + C. \end{displaymath}$

(22.1)

where $\theta$ is the dihedral angle for the three-bond coupling,

, and

are so-called Karplus coefficients, and

is a phase.

The refinement energy term is $E_{COUP} = K_{COUP}(J-J_{obs})^2.$ The reference is Garrett et al. (1994).

Xplor-NIH 2025-03-21