## Restraints.make_distance() — make distance restraints

`make_distance(atmsel1, atmsel2, aln, spline_on_site, restraint_group, maximal_distance, residue_span_range=(0, 99999), residue_span_sign=True, distance_rsr_model=1, basis_pdf_weight='LOCAL', basis_relative_weight=0.05, spline_dx=0.5, spline_min_points=5, spline_range=4.0, accessibility_type=8, restraint_stdev=(0.1, 1.0), restraint_stdev2=(0.0, 0.0, 0.0), surftyp=1, distngh=6.0, edat=None, io=None, exclude_distance=0.0)`

Requirements:
  topology `&` parameters

> This command calculates and selects new distance restraints. See Restraints.make() for full details.

> Distance restraints are generated for all pairs of atoms where atom is from selection atmsel1 and atom is from selection atmsel2. Moreover, for a restraint to be created, at least one distance in the template structures must be less than maximal_distance (in Å). The mean of this basis pdf is equal to the template distance and its standard deviation is calculated from an analytic model specified by distance_rsr_model. Use model 5 for Cα - Cα distances and model 6 for N-O distances. For models 1 through 6, this standard deviation is transformed by where and are given by restraint_stdev and is a gap weighting function of the form . is the average distance of the two residues involved in the restraint from a gap. For models 3 through 6, this is additionally transformed by where the sum is over each of the atoms involved in the distance, and are given by restraint_stdev2, and is the distance of each residue from a gap. The first six models are polynomials and depend on several structural features of the template and its similarity to the target. The polynomial coefficients are specified in library file `'$PARAMS_LIB'`. When “polynomial model” 7 is selected, the standard deviation of restraints is set to constant . Each basis pdf in the distance pdf corresponds to one template structure with an equivalent distance.

> In addition, the atom pairs restrained by homology-derived restraints must by default not be in a chemical bond, chemical angle, dihedral angle, or on an excluded pairs list. This behavior can be changed by resetting energy_data.excl_local (see conjugate_gradients()).

> If the restrained distance for a given atom pair is less than exclude_distance, that pair is also excluded from the nonbonded list. This is useful if you are building short distance restraints to approximate bonds.

> An 'equivalent' distance is defined as the distance between a pair of equivalent atoms. See Atom.get_equivalent_atom() for the rules for determining equivalency.