stereochemistry.py

"""@namespace IMP.pmi.restraints.stereochemistry
Restraints for keeping correct stereochemistry.
"""

import IMP
import IMP.core
import IMP.atom
import IMP.container
import IMP.isd
import IMP.pmi.tools
from operator import itemgetter
import math


class ConnectivityRestraint(IMP.pmi.restraints.RestraintBase):
    """Create a restraint between consecutive TempResidue objects
       or an entire PMI Molecule object."""

    def __init__(self,
                 objects,
                 scale=1.0,
                 disorderedlength=False,
                 upperharmonic=True,
                 resolution=1,
                 label=None):
        """
        @param objects - a list of hierarchies, PMI TempResidues OR a
               single Molecule
        @param scale Scale the maximal distance between the beads by this
               factor when disorderedlength is False. The maximal distance
               is calculated as ((float(residuegap) + 1.0) * 3.6) * scale.
        @param disorderedlength - This flag uses either disordered length
               calculated for random coil peptides (True) or zero
               surface-to-surface distance between beads (False)
               as optimal distance for the sequence connectivity restraint.
        @param upperharmonic - This flag uses either harmonic (False)
               or upperharmonic (True) in the intra-pair
               connectivity restraint.
        @param resolution - The resolution to connect things at - only used
               if you pass PMI objects
        @param label - A string to identify this restraint in the
               output/stat file
        """

        hiers = IMP.pmi.tools.input_adaptor(objects, resolution)
        if len(hiers) > 1:
            raise Exception("ConnectivityRestraint: only pass stuff from "
                            "one Molecule, please")
        hiers = hiers[0]
        m = list(hiers)[0].get_model()
        super().__init__(m, label=label)

        self.kappa = 10  # spring constant used for the harmonic restraints
        SortedSegments = []
        for h in hiers:
            try:
                start = IMP.atom.Hierarchy(h).get_children()[0]
            except:  # noqa: E722
                start = IMP.atom.Hierarchy(h)

            try:
                end = IMP.atom.Hierarchy(h).get_children()[-1]
            except:  # noqa: E722
                end = IMP.atom.Hierarchy(h)

            startres = IMP.pmi.tools.get_residue_indexes(start)[0]
            SortedSegments.append((start, end, startres))
        SortedSegments = sorted(SortedSegments, key=itemgetter(2))

        # connect the particles
        self.particle_pairs = []
        for x in range(len(SortedSegments) - 1):

            last = SortedSegments[x][1]
            first = SortedSegments[x + 1][0]

            apply_restraint = True

            # Apply connectivity runless ALL of the following are true:
            #   - first and last both have RigidBodyMember decorators
            #   - first and last are both RigidMembers
            #   - first and last are part of the same RigidBody object

            # Check for both in a rigid body
            if IMP.core.RigidBodyMember.get_is_setup(first) and \
                    IMP.core.RigidBodyMember.get_is_setup(last) and \
                    IMP.core.RigidMember.get_is_setup(first) and \
                    IMP.core.RigidMember.get_is_setup(last):
                # Check if the rigid body objects for each particle are
                # the same object.
                #  if so, skip connectivity restraint
                if IMP.core.RigidBodyMember(first).get_rigid_body() \
                        == IMP.core.RigidBodyMember(last).get_rigid_body():
                    apply_restraint = False

            if apply_restraint:

                nreslast = len(IMP.pmi.tools.get_residue_indexes(last))
                lastresn = IMP.pmi.tools.get_residue_indexes(last)[-1]
                nresfirst = len(IMP.pmi.tools.get_residue_indexes(first))
                firstresn = IMP.pmi.tools.get_residue_indexes(first)[0]

                residuegap = firstresn - lastresn - 1
                if disorderedlength and (nreslast / 2 + nresfirst / 2
                                         + residuegap) > 20.0:
                    # calculate the distance between the sphere centers
                    # using Kohn PNAS 2004
                    optdist = math.sqrt(5 / 3) * 1.93 * \
                        (nreslast / 2 + nresfirst / 2 + residuegap) ** 0.6
                    if upperharmonic:
                        hu = IMP.core.HarmonicUpperBound(optdist, self.kappa)
                    else:
                        hu = IMP.core.Harmonic(optdist, self.kappa)
                    dps = IMP.core.DistancePairScore(hu)
                else:  # default
                    optdist = (0.0 + (float(residuegap) + 1.0) * 3.6) * scale
                    if upperharmonic:  # default
                        hu = IMP.core.HarmonicUpperBound(optdist, self.kappa)
                    else:
                        hu = IMP.core.Harmonic(optdist, self.kappa)
                    dps = IMP.core.SphereDistancePairScore(hu)

                pt0 = last.get_particle()
                pt1 = first.get_particle()
                self.particle_pairs.append((pt0, pt1))
                r = IMP.core.PairRestraint(
                    self.model, dps, (pt0.get_index(), pt1.get_index()))

                print("Adding sequence connectivity restraint between",
                      pt0.get_name(), " and ", pt1.get_name(), 'of distance',
                      optdist)
                self.rs.add_restraint(r)

    def get_num_restraints(self):
        """ Returns number of connectivity restraints """
        return len(self.rs.get_restraints())

    def get_particle_pairs(self):
        """ Returns the list of connected particles pairs """
        return self.particle_pairs


class ExcludedVolumeSphere(IMP.pmi.restraints.RestraintBase):
    """A class to create an excluded volume restraint for a set of particles
       at a given resolution.
    Can be initialized as a bipartite restraint between two sets of particles.
    # Potential additional function: Variable resolution for each PMI object.
    Perhaps passing selection_tuples with (PMI_object, resolution)
    """
    _include_in_rmf = True

    def __init__(self,
                 included_objects,
                 other_objects=None,
                 resolution=1000,
                 kappa=1.0,
                 label=None):
        """Constructor.
        @param included_objects Can be one of the following inputs:
               IMP Hierarchy, PMI System/State/Molecule/TempResidue,
               or a list/set of them
        @param other_objects Initializes a bipartite restraint between
               included_objects and other_objects
               Same format as included_objects
        @param resolution The resolution particles at which to impose the
               restraint. By default, the coarsest particles will be chosen.
               If a number is chosen, for each particle, the closest
               resolution will be used (see IMP.atom.Selection).
        @param kappa Restraint strength
        """

        self.kappa = kappa
        self.cpc = None
        bipartite = False

        # gather IMP hierarchies from input objects
        hierarchies = IMP.pmi.tools.input_adaptor(included_objects,
                                                  resolution,
                                                  flatten=True)
        included_ps = []
        if other_objects is not None:
            bipartite = True
            other_hierarchies = IMP.pmi.tools.input_adaptor(other_objects,
                                                            resolution,
                                                            flatten=True)
            other_ps = []

        # perform selection
        if hierarchies is None:
            raise Exception("Must at least pass included objects")
        mdl = hierarchies[0].get_model()
        super().__init__(mdl, label=label)

        included_ps = [h.get_particle() for h in hierarchies]
        if bipartite:
            other_ps = [h.get_particle() for h in other_hierarchies]

        # setup score
        ssps = IMP.core.SoftSpherePairScore(self.kappa)
        lsa = IMP.container.ListSingletonContainer(self.model)
        lsa.add(IMP.get_indexes(included_ps))

        # setup close pair container
        if not bipartite:
            rbcpf = IMP.core.RigidClosePairsFinder()
            self.cpc = IMP.container.ClosePairContainer(lsa, 0.0, rbcpf, 10.0)
            evr = IMP.container.PairsRestraint(ssps, self.cpc)
        else:
            other_lsa = IMP.container.ListSingletonContainer(self.model)
            other_lsa.add(IMP.get_indexes(other_ps))
            self.cpc = IMP.container.CloseBipartitePairContainer(
                lsa,
                other_lsa,
                0.0,
                10.0)
            evr = IMP.container.PairsRestraint(ssps, self.cpc)

        self.rs.add_restraint(evr)

    def add_excluded_particle_pairs(self, excluded_particle_pairs):
        # add pairs to be filtered when calculating the score
        inverted = [(p1, p0) for p0, p1 in excluded_particle_pairs]
        lpc = IMP.container.ListPairContainer(self.model)
        lpc.add(IMP.get_indexes(excluded_particle_pairs))
        lpc.add(IMP.get_indexes(inverted))
        icpf = IMP.container.InContainerPairFilter(lpc)
        self.cpc.add_pair_filter(icpf)


class HelixRestraint(IMP.pmi.restraints.RestraintBase):
    """Enforce ideal Helix dihedrals and bonds for a selection
       at resolution 0"""
    def __init__(self,
                 hierarchy,
                 selection_tuple,
                 weight=1.0,
                 label=None):
        """Constructor
        @param hierarchy the root node
        @param selection_tuple (start, stop, molname, copynum=0)
        @param weight
        """
        m = hierarchy.get_model()
        super().__init__(m, weight=weight)
        start = selection_tuple[0]
        stop = selection_tuple[1]
        mol = selection_tuple[2]
        copy_index = 0
        if len(selection_tuple) > 3:
            copy_index = selection_tuple[3]

        sel = IMP.atom.Selection(
            hierarchy, molecule=mol, copy_index=copy_index,
            residue_indexes=range(start, stop+1))
        ps = sel.get_selected_particles(with_representation=False)
        res = [IMP.atom.Residue(p) for p in ps]
        self.r = IMP.atom.HelixRestraint(res)
        self.rs.add_restraint(self.r)
        print('Created helix %s.%i.%i-%i with %i dihedrals and %i bonds'
              % (mol, copy_index, start, stop, self.get_number_of_bonds(),
                 self.get_number_of_dihedrals()))

    def get_number_of_bonds(self):
        return self.r.get_number_of_bonds()

    def get_number_of_dihedrals(self):
        return self.r.get_number_of_dihedrals()


class ResidueBondRestraint(IMP.pmi.restraints.RestraintBase):
    """ Add bond restraint between pair of consecutive
    residues/beads to enforce the stereochemistry.
    """
    def __init__(self, objects, distance=3.78, strength=10.0, jitter=None):
        """Constructor
        @param objects  Objects to restrain
        @param distance Resting distance for restraint
        @param strength Bond constant
        @param jitter Defines the +- added to the optimal distance in
               the harmonic well restraint used to increase the tolerance
        """

        particles = IMP.pmi.tools.input_adaptor(objects, 1, flatten=True)
        m = particles[0].get_model()
        super().__init__(m)

        self.pairslist = []

        if not jitter:
            ts = IMP.core.Harmonic(distance, strength)
        else:
            ts = IMP.core.HarmonicWell(
                (distance - jitter, distance + jitter), strength)

        for ps in IMP.pmi.tools.sublist_iterator(particles, 2, 2):
            pair = []
            if len(ps) != 2:
                raise ValueError("wrong length of pair")
            for p in ps:
                if not IMP.atom.Residue.get_is_setup(p):
                    raise TypeError("%s is not a residue" % p)
                else:
                    pair.append(p)
            print("ResidueBondRestraint: adding a restraint between %s %s"
                  % (pair[0].get_name(), pair[1].get_name()))
            self.rs.add_restraint(
                IMP.core.DistanceRestraint(self.model, ts, pair[0], pair[1]))
            self.pairslist.append(IMP.ParticlePair(pair[0], pair[1]))
            self.pairslist.append(IMP.ParticlePair(pair[1], pair[0]))

    def get_excluded_pairs(self):
        return self.pairslist


class ResidueAngleRestraint(IMP.pmi.restraints.RestraintBase):
    """Add angular restraint between triplets of consecutive
    residues/beads to enforce the stereochemistry.
    """
    def __init__(self, objects, anglemin=100.0, anglemax=140.0, strength=10.0):

        particles = IMP.pmi.tools.input_adaptor(objects, 1, flatten=True)
        m = particles[0].get_model()
        super().__init__(m)

        self.pairslist = []

        ts = IMP.core.HarmonicWell(
            (math.pi * anglemin / 180.0,
             math.pi * anglemax / 180.0),
            strength)

        for ps in IMP.pmi.tools.sublist_iterator(particles, 3, 3):
            triplet = []
            if len(ps) != 3:
                raise ValueError("wrong length of triplet")
            for p in ps:
                if not IMP.atom.Residue.get_is_setup(p):
                    raise TypeError("%s is not a residue" % p)
                else:
                    triplet.append(p)
            print("ResidueAngleRestraint: adding a restraint between %s %s %s"
                  % (triplet[0].get_name(), triplet[1].get_name(),
                     triplet[2].get_name()))
            self.rs.add_restraint(
                IMP.core.AngleRestraint(triplet[0].get_model(), ts,
                                        triplet[0],
                                        triplet[1],
                                        triplet[2]))
            self.pairslist.append(IMP.ParticlePair(triplet[0], triplet[2]))
            self.pairslist.append(IMP.ParticlePair(triplet[2], triplet[0]))

    def get_excluded_pairs(self):
        return self.pairslist


class ResidueDihedralRestraint(IMP.pmi.restraints.RestraintBase):
    """Add dihedral restraints between quadruplet of consecutive
    residues/beads to enforce the stereochemistry.
    Give as input a string of "C" and "T", meaning cys (0+-40)
    or trans (180+-40) dihedral. The length of the string must be #residue-3.
    Without the string, the dihedral will be assumed trans.
    """
    def __init__(self, objects, stringsequence=None, strength=10.0):

        particles = IMP.pmi.tools.input_adaptor(objects, 1, flatten=True)
        m = particles[0].get_model()
        super().__init__(m)

        self.pairslist = []

        if stringsequence is None:
            stringsequence = "T" * (len(particles) - 3)

        for n, ps in enumerate(
                IMP.pmi.tools.sublist_iterator(particles, 4, 4)):
            quadruplet = []
            if len(ps) != 4:
                raise ValueError("wrong length of quadruplet")
            for p in ps:
                if not IMP.atom.Residue.get_is_setup(p):
                    raise TypeError("%s is not a residue" % p)
                else:
                    quadruplet.append(p)
            dihedraltype = stringsequence[n]
            if dihedraltype == "C":
                anglemin = -20.0
                anglemax = 20.0
                ts = IMP.core.HarmonicWell(
                    (math.pi * anglemin / 180.0,
                     math.pi * anglemax / 180.0),
                    strength)
                print("ResidueDihedralRestraint: adding a CYS restraint "
                      "between %s %s %s %s"
                      % (quadruplet[0].get_name(), quadruplet[1].get_name(),
                         quadruplet[2].get_name(), quadruplet[3].get_name()))
            if dihedraltype == "T":
                anglemin = 180 - 70.0
                anglemax = 180 + 70.0
                ts = IMP.core.HarmonicWell(
                    (math.pi * anglemin / 180.0,
                     math.pi * anglemax / 180.0),
                    strength)
                print("ResidueDihedralRestraint: adding a TRANS restraint "
                      "between %s %s %s %s"
                      % (quadruplet[0].get_name(),
                         quadruplet[1].get_name(), quadruplet[2].get_name(),
                         quadruplet[3].get_name()))
            self.rs.add_restraint(
                IMP.core.DihedralRestraint(self.model, ts,
                                           quadruplet[0],
                                           quadruplet[1],
                                           quadruplet[2],
                                           quadruplet[3]))
            self.pairslist.append(
                IMP.ParticlePair(quadruplet[0], quadruplet[3]))
            self.pairslist.append(
                IMP.ParticlePair(quadruplet[3], quadruplet[0]))


class ElasticNetworkRestraint:
    """Add harmonic restraints between all pairs
    """
    def __init__(self, hierarchy, selection_tuples=None, resolution=1,
                 strength=0.01, dist_cutoff=10.0, ca_only=True):
        """Constructor
        @param hierarchy Root hierarchy to select from
        @param selection_tuples Selecting regions for the restraint
               [[start,stop,molname,copy_index=0],...]
        @param resolution Resolution for applying restraint
        @param strength Bond strength
        @param dist_cutoff Cutoff for making restraints
        @param ca_only Selects only CAlphas. Only matters if resolution=0.
        """

        particles = []
        self.m = hierarchy.get_model()
        for st in selection_tuples:
            copy_index = 0
            if len(st) > 3:
                copy_index = st[3]
            if not ca_only:
                sel = IMP.atom.Selection(
                    hierarchy, molecule=st[2],
                    residue_indexes=range(st[0], st[1]+1),
                    copy_index=copy_index)
            else:
                sel = IMP.atom.Selection(
                    hierarchy, molecule=st[2],
                    residue_indexes=range(st[0], st[1]+1),
                    copy_index=copy_index,
                    atom_type=IMP.atom.AtomType("CA"))
            particles += sel.get_selected_particles()

        self.weight = 1
        self.label = "None"
        self.pairslist = []

        # create score
        self.rs = IMP.pmi.create_elastic_network(
            particles, dist_cutoff, strength)
        for r in self.rs.get_restraints():
            a1, a2 = r.get_inputs()
            self.pairslist.append(IMP.ParticlePair(a1, a2))
            self.pairslist.append(IMP.ParticlePair(a2, a1))
        print('ElasticNetwork: created', self.rs.get_number_of_restraints(),
              'restraints')

    def set_label(self, label):
        self.label = label
        self.rs.set_name(label)
        for r in self.rs.get_restraints():
            r.set_name(label)

    def add_to_model(self):
        IMP.pmi.tools.add_restraint_to_model(self.m, self.rs)

    def get_restraint(self):
        return self.rs

    def set_weight(self, weight):
        self.weight = weight
        self.rs.set_weight(weight)

    def get_excluded_pairs(self):
        return self.pairslist

    def get_output(self):
        output = {}
        score = self.weight * self.rs.unprotected_evaluate(None)
        output["_TotalScore"] = str(score)
        output["ElasticNetworkRestraint_" + self.label] = str(score)
        return output


class CharmmForceFieldRestraint:
    """ Enable CHARMM force field """
    def __init__(self, root, ff_temp=300.0, zone_ps=None, zone_size=10.0,
                 enable_nonbonded=True, enable_bonded=True,
                 zone_nonbonded=False):
        """Setup the CHARMM restraint on a selection. Expecting atoms.
        @param root             The node at which to apply the restraint
        @param ff_temp          The temperature of the force field
        @param zone_ps          Create a zone around this set of particles
               Automatically includes the entire residue (incl. backbone)
        @param zone_size        The size for looking for neighbor residues
        @param enable_nonbonded Allow the repulsive restraint
        @param enable_bonded    Allow the bonded restraint
        @param zone_nonbonded   EXPERIMENTAL: exclude from nonbonded all
               sidechains that aren't in zone!
        """

        kB = (1.381 * 6.02214) / 4184.0

        self.mdl = root.get_model()
        self.bonds_rs = IMP.RestraintSet(self.mdl, 1.0 / (kB * ff_temp),
                                         'BONDED')
        self.nonbonded_rs = IMP.RestraintSet(self.mdl, 1.0 / (kB * ff_temp),
                                             'NONBONDED')
        self.weight = 1.0
        self.label = ""

        # setup topology and bonds etc
        if enable_bonded:
            ff = IMP.atom.get_heavy_atom_CHARMM_parameters()
            topology = ff.create_topology(root)
            topology.apply_default_patches()
            topology.setup_hierarchy(root)
            if zone_ps is not None:
                limit_to_ps = IMP.pmi.topology.get_particles_within_zone(
                    root, zone_ps, zone_size, entire_residues=True,
                    exclude_backbone=False)
                r = IMP.atom.CHARMMStereochemistryRestraint(root,
                                                            topology,
                                                            limit_to_ps)
                self.ps = limit_to_ps
            else:
                r = IMP.atom.CHARMMStereochemistryRestraint(root, topology)
                self.ps = IMP.core.get_leaves(root)
            print('init bonds score', r.unprotected_evaluate(None))
            self.bonds_rs.add_restraint(r)
            ff.add_radii(root)

        atoms = IMP.atom.get_by_type(root, IMP.atom.ATOM_TYPE)
        # non-bonded forces
        if enable_nonbonded:
            if (zone_ps is not None) and zone_nonbonded:
                print('stereochemistry: zone_nonbonded is True')
                # atoms list should only include backbone plus zone_ps!
                backbone_types = ['C', 'N', 'CB', 'O']
                sel = IMP.atom.Selection(
                    root, atom_types=[IMP.atom.AtomType(n)
                                      for n in backbone_types])
                backbone_atoms = sel.get_selected_particles()
                sel_ps = IMP.pmi.topology.get_particles_within_zone(
                    root, zone_ps, zone_size, entire_residues=True,
                    exclude_backbone=True)

                self.nbl = IMP.container.CloseBipartitePairContainer(
                    IMP.container.ListSingletonContainer(backbone_atoms),
                    IMP.container.ListSingletonContainer(sel_ps),
                    4.0)
            else:
                cont = IMP.container.ListSingletonContainer(self.mdl, atoms)
                self.nbl = IMP.container.ClosePairContainer(cont, 4.0)
            if enable_bonded:
                self.nbl.add_pair_filter(r.get_full_pair_filter())
            pairscore = IMP.isd.RepulsiveDistancePairScore(0, 1)
            pr = IMP.container.PairsRestraint(pairscore, self.nbl)
            self.nonbonded_rs.add_restraint(pr)
        print('CHARMM is set up')

    def set_label(self, label):
        self.label = label
        self.rs.set_name(label)
        for r in self.rs.get_restraints():
            r.set_name(label)

    def add_to_model(self):
        IMP.pmi.tools.add_restraint_to_model(self.mdl, self.bonds_rs)
        IMP.pmi.tools.add_restraint_to_model(self.mdl, self.nonbonded_rs)

    def get_restraint(self):
        return self.rs

    def get_close_pair_container(self):
        return self.nbl

    def set_weight(self, weight):
        self.weight = weight
        self.rs.set_weight(weight)

    def get_output(self):
        output = {}
        bonds_score = self.weight * self.bonds_rs.unprotected_evaluate(None)
        nonbonded_score = \
            self.weight * self.nonbonded_rs.unprotected_evaluate(None)
        score = bonds_score+nonbonded_score
        output["_TotalScore"] = str(score)
        output["CHARMM_BONDS"] = str(bonds_score)
        output["CHARMM_NONBONDED"] = str(nonbonded_score)
        return output


class PseudoAtomicRestraint:
    """Add bonds and improper dihedral restraints for the CBs
    """
    def __init__(
        self, rnums, representation, selection_tuple, strength=10.0, kappa=1.0,
            jitter_angle=0.0, jitter_improper=0.0):
        '''
        need to add:
        ca-ca bond
        ca-cb is a constraint, no restraint needed
        ca-ca-ca
        cb-ca-ca-cb
        '''

        self.m = representation.prot.get_model()
        self.rs = IMP.RestraintSet(self.m, "PseudoAtomic")
        self.rset_angles = IMP.RestraintSet(self.m, "PseudoAtomic_Angles")
        self.rset_bonds = IMP.RestraintSet(self.m, "PseudoAtomic_Bonds")
        self.weight = 1
        self.label = "None"
        self.pairslist = []

        for rnum in rnums:
            ca, cb = self.get_ca_cb(
                IMP.pmi.tools.select_by_tuple(representation,
                                              (rnum, rnum, 'chainA'),
                                              resolution=0))
            if cb is not None:
                nter = False
                cter = False
                ca_prev, cb_prev = self.get_ca_cb(
                    IMP.pmi.tools.select_by_tuple(representation,
                                                  (rnum - 1, rnum - 1,
                                                   'chainA'), resolution=0))
                ca_next, cb_next = self.get_ca_cb(
                    IMP.pmi.tools.select_by_tuple(representation,
                                                  (rnum + 1, rnum + 1,
                                                   'chainA'), resolution=0))
                if ca_prev is None:
                    nter = True
                else:
                    if ca_next is None:
                        cter = True
                    else:
                        if (nter and cter):
                            continue

                # adding a bond restraint between CA and CB
                # h=IMP.core.Harmonic(6.0,kappa)
                # dps=IMP.core.DistancePairScore(h)
                # pr=IMP.core.PairRestraint(dps,IMP.ParticlePair(ca,cb))
                # self.pairslist.append((ca,cb))
                # self.rset_bonds.add_restraint(pr)

                # creating improper dihedral restraint
                # hus=IMP.core.Harmonic(2.09,kappa)
                hupp = IMP.core.HarmonicUpperBound(
                    2.09 +
                    jitter_angle /
                    0.5,
                    kappa)
                hlow = IMP.core.HarmonicLowerBound(
                    2.09 -
                    jitter_angle /
                    0.5,
                    kappa)
                if not nter:
                    # ar13=IMP.core.AngleRestraint(hus,ca_prev,ca,cb)
                    # self.rset_angles.add_restraint(ar13)
                    ar13u = IMP.core.AngleRestraint(hupp, ca_prev, ca, cb)
                    ar13l = IMP.core.AngleRestraint(hlow, ca_prev, ca, cb)
                    self.rset_angles.add_restraint(ar13u)
                    self.rset_angles.add_restraint(ar13l)
                if not cter:
                    # ar23=IMP.core.AngleRestraint(hus,ca_next,ca,cb)
                    # self.rset_angles.add_restraint(ar23)
                    ar23u = IMP.core.AngleRestraint(hupp, ca_next, ca, cb)
                    ar23l = IMP.core.AngleRestraint(hlow, ca_next, ca, cb)
                    self.rset_angles.add_restraint(ar23u)
                    self.rset_angles.add_restraint(ar23l)
                if not nter and not cter:
                    # hus2=IMP.core.Harmonic(0,kappa)
                    # idr=IMP.core.DihedralRestraint(hus2,ca,ca_prev,ca_next,cb)
                    # self.rset_angles.add_restraint(idr)

                    hus2upp = IMP.core.HarmonicUpperBound(
                        jitter_improper,
                        kappa)
                    hus2low = IMP.core.HarmonicLowerBound(
                        -
                        jitter_improper,
                        kappa)
                    idru = IMP.core.DihedralRestraint(
                        hus2upp,
                        ca,
                        ca_prev,
                        ca_next,
                        cb)
                    idrl = IMP.core.DihedralRestraint(
                        hus2low,
                        ca,
                        ca_prev,
                        ca_next,
                        cb)
                    self.rset_angles.add_restraint(idru)
                    self.rset_angles.add_restraint(idrl)
        self.rs.add_restraint(self.rset_bonds)
        self.rs.add_restraint(self.rset_angles)

    def get_ca_cb(self, atoms):
        ca = None
        cb = None
        for a in atoms:
            if IMP.atom.Atom(a).get_atom_type() == IMP.atom.AtomType("CA"):
                ca = a.get_particle()
            elif IMP.atom.Atom(a).get_atom_type() == IMP.atom.AtomType("CB"):
                cb = a.get_particle()
        return ca, cb

    def set_label(self, label):
        self.label = label
        self.rs.set_name(label)
        for r in self.rs.get_restraints():
            r.set_name(label)

    def add_to_model(self):
        IMP.pmi.tools.add_restraint_to_model(self.m, self.rs)

    def get_restraint(self):
        return self.rs

    def set_weight(self, weight):
        self.weight = weight
        self.rs.set_weight(weight)

    def get_excluded_pairs(self):
        return self.pairslist

    def get_output(self):
        output = {}
        score = self.weight * self.rs.unprotected_evaluate(None)
        output["_TotalScore"] = str(score)
        output["PseudoAtomicRestraint_" + self.label] = str(score)
        return output


class SymmetryRestraint:
    """Create harmonic restraints between the reference and (transformed)
       clones.

    @note Wraps IMP::core::TransformedDistancePairScore with an
          IMP::core::Harmonic
    """
    def __init__(self, references, clones_list, transforms,
                 label='', strength=10.0, ca_only=False):
        """Constructor
        @param references Can be one of the following inputs:
               IMP Hierarchy, PMI System/State/Molecule/TempResidue,
               or a list/set of them
        @param clones_list List of lists of the above
        @param transforms Transforms moving each selection to the first
               selection
        @param label Label for output
        @param strength            The elastic bond strength
        @param ca_only Optionally select so only CAlpha particles are used
        """

        refs = IMP.pmi.tools.input_adaptor(references, flatten=True)
        self.mdl = refs[0].get_model()
        self.rs = IMP.RestraintSet(self.mdl, "Symmetry")
        self.weight = 1
        self.label = label
        if len(clones_list) != len(transforms):
            raise Exception(
                'Error: There should be as many clones as transforms')

        harmonic = IMP.core.Harmonic(0., strength)
        for tmp_clones, trans in zip(clones_list, transforms):
            clones = IMP.pmi.tools.input_adaptor(tmp_clones, flatten=True)
            if len(clones) != len(refs):
                raise Exception("Error: len(references)!=len(clones)")
            pair_score = IMP.core.TransformedDistancePairScore(harmonic, trans)
            for p0, p1 in zip(refs, clones):
                if not ca_only or (
                        IMP.atom.Atom(p0).get_atom_type()
                        == IMP.atom.AtomType("CA") and
                        IMP.atom.Atom(p1).get_atom_type()
                        == IMP.atom.AtomType("CA")):
                    r = IMP.core.PairRestraint(
                        self.mdl, pair_score, [p0.get_particle_index(),
                                               p1.get_particle_index()])
                    self.rs.add_restraint(r)
        print('created symmetry network with',
              self.rs.get_number_of_restraints(), 'restraints')

    def set_label(self, label):
        self.label = label
        self.rs.set_name(label)
        for r in self.rs.get_restraints():
            r.set_name(label)

    def add_to_model(self):
        IMP.pmi.tools.add_restraint_to_model(self.mdl, self.rs)

    def get_restraint(self):
        return self.rs

    def set_weight(self, weight):
        self.weight = weight
        self.rs.set_weight(weight)

    def get_excluded_pairs(self):
        return self.pairslist

    def get_output(self):
        output = {}
        score = self.weight * self.rs.unprotected_evaluate(None)
        output["SymmetryRestraint_" + self.label] = str(score)
        output["_TotalScore"] = str(score)
        return output


class FusionRestraint:
    """Creates a restraint between the termini two polypeptides, to simulate
       the sequence connectivity."""
    def __init__(self, nterminal, cterminal, scale=1.0, disorderedlength=False,
                 upperharmonic=True, resolution=1, label="None"):
        """
        @param nterminal -  single PMI2 Hierarchy/molecule at the nterminal
        @param cterminal -  single PMI2 Hierarchy/molecule at the cterminal
        @param scale Scale the maximal distance between the beads by this
               factor when disorderedlength is False.
               The maximal distance is calculated as
               ((float(residuegap) + 1.0) * 3.6) * scale.
        @param disorderedlength - This flag uses either disordered length
                     calculated for random coil peptides (True) or zero
                     surface-to-surface distance between beads (False)
                     as optimal distance for the sequence connectivity
                     restraint.
        @param upperharmonic - This flag uses either harmonic (False)
                     or upperharmonic (True) in the intra-pair
                     connectivity restraint.
        @param resolution - The resolution to connect things at - only used
               if you pass PMI objects
        @param label - A string to identify this restraint in the
               output/stat file
        """
        self.label = label
        self.weight = 1.0
        ssn = IMP.pmi.tools.get_sorted_segments(nterminal)
        ssc = IMP.pmi.tools.get_sorted_segments(cterminal)
        nter_lastres = ssn[-1][1]
        cter_firstres = ssc[0][0]
        self.m = nter_lastres.get_model()

        self.kappa = 10  # spring constant used for the harmonic restraints

        optdist = (3.6) * scale
        if upperharmonic:  # default
            hu = IMP.core.HarmonicUpperBound(optdist, self.kappa)
        else:
            hu = IMP.core.Harmonic(optdist, self.kappa)
        dps = IMP.core.SphereDistancePairScore(hu)

        pt0 = nter_lastres.get_particle()
        pt1 = cter_firstres.get_particle()
        r = IMP.core.PairRestraint(self.m, dps,
                                   (pt0.get_index(), pt1.get_index()))
        self.rs = IMP.RestraintSet(self.m, "fusion_restraint")
        print("Adding fusion connectivity restraint between", pt0.get_name(),
              " and ", pt1.get_name(), 'of distance', optdist)
        self.rs.add_restraint(r)

    def set_label(self, label):
        self.label = label

    def get_weight(self):
        return self.weight

    def add_to_model(self):
        IMP.pmi.tools.add_restraint_to_model(self.m, self.rs)

    def get_restraint(self):
        return self.rs

    def set_weight(self, weight):
        self.weight = weight
        self.rs.set_weight(weight)

    def get_output(self):
        output = {}
        score = self.weight * self.rs.unprotected_evaluate(None)
        output["_TotalScore"] = str(score)
        output["FusionRestraint_" + self.label] = str(score)
        return output

    def evaluate(self):
        return self.weight * self.rs.unprotected_evaluate(None)


class PlaneDihedralRestraint(IMP.pmi.restraints.RestraintBase):

    """Restrain the dihedral between planes defined by three particles.

    This restraint is useful for restraining the twist of a string of
    more or less identical rigid bodies, so long as the curvature is mild.
    """

    def __init__(self, particle_triplets, angle=0., k=1., label=None,
                 weight=1.):
        """Constructor
        @param particle_triplets List of lists of 3 particles. Each triplet
                                 defines a plane. Dihedrals of adjacent planes
                                 in list are scored.
        @param angle Angle of plane dihedral in degrees
        @param k Strength of restraint
        @param label Label for output
        @param weight Weight of restraint
        @note Particles defining planes should be rigid and more or less
              parallel for proper behavior
        """
        model = particle_triplets[0][0].get_model()
        super().__init__(model, label=label, weight=weight)

        angle = math.pi * angle / 180.
        ds = IMP.core.Cosine(.5 * k, 1, -angle)
        for i, t1 in enumerate(particle_triplets[:-1]):
            t2 = particle_triplets[i + 1]
            q1 = [t1[1], t1[0], t2[0], t2[1]]
            q2 = [t1[2], t1[0], t2[0], t2[2]]
            self.rs.add_restraint(
                IMP.core.DihedralRestraint(self.model, ds, *q1))
            self.rs.add_restraint(
                IMP.core.DihedralRestraint(self.model, ds, *q2))