Python PDBFile.getPositions方法代码示例

# 需要导入模块: from simtk.openmm.app import PDBFile [as 别名]
# 或者: from simtk.openmm.app.PDBFile import getPositions [as 别名]
    def addSolvent(self, forcefield, model='tip3p', boxSize=None, padding=None, positiveIon='Na+', negativeIon='Cl-', ionicStrength=0*molar):
        """Add solvent (both water and ions) to the model to fill a rectangular box.

        The algorithm works as follows:
        1. Water molecules are added to fill the box.
        2. Water molecules are removed if their distance to any solute atom is less than the sum of their van der Waals radii.
        3. If the solute is charged, enough positive or negative ions are added to neutralize it.  Each ion is added by
           randomly selecting a water molecule and replacing it with the ion.
        4. Ion pairs are added to give the requested total ionic strength.

        The box size can be specified in three ways.  First, you can explicitly give a box size to use.  Alternatively, you can
        give a padding distance.  The largest dimension of the solute (along the x, y, or z axis) is determined, and a cubic
        box of size (largest dimension)+2*padding is used.  Finally, if neither a box size nor a padding distance is specified,
        the existing Topology's unit cell dimensions are used.

        Parameters:
         - forcefield (ForceField) the ForceField to use for determining van der Waals radii and atomic charges
         - model (string='tip3p') the water model to use.  Supported values are 'tip3p', 'spce', 'tip4pew', and 'tip5p'.
         - boxSize (Vec3=None) the size of the box to fill with water
         - padding (distance=None) the padding distance to use
         - positiveIon (string='Na+') the type of positive ion to add.  Allowed values are 'Cs+', 'K+', 'Li+', 'Na+', and 'Rb+'
         - negativeIon (string='Cl-') the type of negative ion to add.  Allowed values are 'Cl-', 'Br-', 'F-', and 'I-'. Be aware
           that not all force fields support all ion types.
         - ionicString (concentration=0*molar) the total concentration of ions (both positive and negative) to add.  This
           does not include ions that are added to neutralize the system.
        """
        # Pick a unit cell size.

        if boxSize is not None:
            if is_quantity(boxSize):
                boxSize = boxSize.value_in_unit(nanometer)
            box = Vec3(boxSize[0], boxSize[1], boxSize[2])*nanometer
        elif padding is not None:
            maxSize = max(max((pos[i] for pos in self.positions))-min((pos[i] for pos in self.positions)) for i in range(3))
            box = (maxSize+2*padding)*Vec3(1, 1, 1)
        else:
            box = self.topology.getUnitCellDimensions()
            if box is None:
                raise ValueError('Neither the box size nor padding was specified, and the Topology does not define unit cell dimensions')
        box = box.value_in_unit(nanometer)
        invBox = Vec3(1.0/box[0], 1.0/box[1], 1.0/box[2])

        # Identify the ion types.

        posIonElements = {'Cs+':elem.cesium, 'K+':elem.potassium, 'Li+':elem.lithium, 'Na+':elem.sodium, 'Rb+':elem.rubidium}
        negIonElements = {'Cl-':elem.chlorine, 'Br-':elem.bromine, 'F-':elem.fluorine, 'I-':elem.iodine}
        if positiveIon not in posIonElements:
            raise ValueError('Illegal value for positive ion: %s' % positiveIon)
        if negativeIon not in negIonElements:
            raise ValueError('Illegal value for negative ion: %s' % negativeIon)
        positiveElement = posIonElements[positiveIon]
        negativeElement = negIonElements[negativeIon]

        # Load the pre-equilibrated water box.

        vdwRadiusPerSigma = 0.5612310241546864907
        if model == 'tip3p':
            waterRadius = 0.31507524065751241*vdwRadiusPerSigma
        elif model == 'spce':
            waterRadius = 0.31657195050398818*vdwRadiusPerSigma
        elif model == 'tip4pew':
            waterRadius = 0.315365*vdwRadiusPerSigma
        elif model == 'tip5p':
            waterRadius = 0.312*vdwRadiusPerSigma
        else:
            raise ValueError('Unknown water model: %s' % model)
        pdb = PDBFile(os.path.join(os.path.dirname(__file__), 'data', model+'.pdb'))
        pdbTopology = pdb.getTopology()
        pdbPositions = pdb.getPositions().value_in_unit(nanometer)
        pdbResidues = list(pdbTopology.residues())
        pdbBoxSize = pdbTopology.getUnitCellDimensions().value_in_unit(nanometer)

        # Have the ForceField build a System for the solute from which we can determine van der Waals radii.

        system = forcefield.createSystem(self.topology)
        nonbonded = None
        for i in range(system.getNumForces()):
            if isinstance(system.getForce(i), NonbondedForce):
                nonbonded = system.getForce(i)
        if nonbonded is None:
            raise ValueError('The ForceField does not specify a NonbondedForce')
        cutoff = [nonbonded.getParticleParameters(i)[1].value_in_unit(nanometer)*vdwRadiusPerSigma+waterRadius for i in range(system.getNumParticles())]
        waterCutoff = waterRadius
        if len(cutoff) == 0:
            maxCutoff = waterCutoff
        else:
            maxCutoff = max(waterCutoff, max(cutoff))

        # Copy the solute over.

        newTopology = Topology()
        newTopology.setUnitCellDimensions(box)
        newAtoms = {}
        newPositions = []*nanometer
        for chain in self.topology.chains():
            newChain = newTopology.addChain()
            for residue in chain.residues():
                newResidue = newTopology.addResidue(residue.name, newChain)
                for atom in residue.atoms():
                    newAtom = newTopology.addAtom(atom.name, atom.element, newResidue)
#.........这里部分代码省略.........