# meld.system.restraints.RdcRestraint

class meld.system.restraints.RdcRestraint(system, scaler, ramp, atom1, atom2, kappa, d_obs, tolerance, force_const, quadratic_cut, weight, alignment_index)[source]

Residual Dipolar Coupling Restraint

__init__(system, scaler, ramp, atom1, atom2, kappa, d_obs, tolerance, force_const, quadratic_cut, weight, alignment_index)[source]

Initialize an RdcRestraint

Parameters
• system (ISystem) – the system this restraint belongs to

• scaler (Optional[RestraintScaler]) – scale the force with alpha

• ramp (Optional[TimeRamp]) – scale the force over time

• atom1 (Union[AtomIndex, PeakMapping]) – the first atom in the RDC

• atom2 (Union[AtomIndex, PeakMapping]) – the second atom in the RDC

• kappa (Quantity) – prefactor for RDC calculation in $$Hz nm^3$$

• d_obs (Quantity) – observed dipolar coupling in $$Hz$$

• tolerance (Quantity) – calculed couplings within tolerance (in $$Hz$$) of d_obs will have zero energy and force

• force_const (Quantity) – force constant in $$kJ/mol/Hz^2$$

• quadratic_cut (Quantity) – force constant becomes linear beyond this deviation in $$s^-1$$

• weight (float) – dimensionless weight to place on this restraint

• alignment_index (int) – which alignment to use

Note

Typical values for kappa are:

• 1H - 1H: $$-360.3 Hz nm^3$$

• 13C - 1H: $$-90.6 Hz nm^3$$

• 15N - 1H: $$36.5 Hz nm^3$$

Methods

 __init__(system, scaler, ramp, atom1, atom2, ...) Initialize an RdcRestraint

Attributes

 atom_index_1 atom_index_2