def process(self, mol, port):
kT_in_kcal_per_mole = self.kT.value_in_unit(unit.kilocalories_per_mole)
# Retrieve data about which molecule we are processing
title = mol.GetTitle()
with TemporaryDirectory() as output_directory:
try:
# Print out which molecule we are processing
self.log.info('Processing {} in directory {}.'.format(title, output_directory))
# Check that molecule is charged.
if not molecule_is_charged(mol):
raise Exception('Molecule %s has no charges; input molecules must be charged.' % mol.GetTitle())
# Write the specified molecule out to a mol2 file without changing its name.
mol2_filename = os.path.join(output_directory, 'input.mol2')
ofs = oechem.oemolostream(mol2_filename)
oechem.OEWriteMol2File(ofs, mol)
# Undo oechem fuckery with naming mol2 substructures `<0>`
from YankCubes.utils import unfuck_oechem_mol2_file
unfuck_oechem_mol2_file(mol2_filename)
# Run YANK on the specified molecule.
from yank.yamlbuild import YamlBuilder
yaml = self.construct_yaml(output_directory=output_directory)
yaml_builder = YamlBuilder(yaml)
yaml_builder.build_experiments()
self.log.info('Ran Yank experiments for molecule {}.'.format(title))
# Analyze the hydration free energy.
from yank.analyze import estimate_free_energies
(Deltaf_ij_solvent, dDeltaf_ij_solvent) = estimate_free_energies(netcdf.Dataset(output_directory + '/experiments/solvent1.nc', 'r'))
(Deltaf_ij_vacuum, dDeltaf_ij_vacuum) = estimate_free_energies(netcdf.Dataset(output_directory + '/experiments/solvent2.nc', 'r'))
DeltaG_hydration = Deltaf_ij_vacuum[0,-1] - Deltaf_ij_solvent[0,-1]
dDeltaG_hydration = np.sqrt(Deltaf_ij_vacuum[0,-1]**2 + Deltaf_ij_solvent[0,-1]**2)
# Add result to original molecule
oechem.OESetSDData(mol, 'DeltaG_yank_hydration', str(DeltaG_hydration * kT_in_kcal_per_mole))
oechem.OESetSDData(mol, 'dDeltaG_yank_hydration', str(dDeltaG_hydration * kT_in_kcal_per_mole))
self.log.info('Analyzed and stored hydration free energy for molecule {}.'.format(title))
# Emit molecule to success port.
self.success.emit(mol)
except Exception as e:
self.log.info('Exception encountered when processing molecule {}.'.format(title))
# Attach error message to the molecule that failed
# TODO: If there is an error in the leap setup log,
# we should capture that and attach it to the failed molecule.
self.log.error(traceback.format_exc())
mol.SetData('error', str(e))
# Return failed molecule
self.failure.emit(mol)
def test_ncmc_engine_molecule():
"""
Check alchemical elimination for alanine dipeptide in vacuum with 0, 1, 2, and 50 switching steps.
"""
molecule_names = ['pentane', 'biphenyl', 'imatinib']
#if os.environ.get("TRAVIS", None) == 'true':
# molecule_names = ['pentane']
for molecule_name in molecule_names:
from perses.tests.utils import createSystemFromIUPAC
[molecule, system, positions,
topology] = createSystemFromIUPAC(molecule_name)
natoms = system.getNumParticles()
# DEBUG
print(molecule_name)
from openeye import oechem
ofs = oechem.oemolostream('%s.mol2' % molecule_name)
oechem.OEWriteMol2File(ofs, molecule)
ofs.close()
# Eliminate half of the molecule
# TODO: Use a more rigorous scheme to make sure we are really cutting the molecule in half and not just eliminating hydrogens or something.
new_to_old_atom_map = {
atom.index: atom.index
for atom in topology.atoms()
if str(atom.element.name) in ['carbon', 'nitrogen']
}
# DEBUG
print(new_to_old_atom_map)
from perses.rjmc.topology_proposal import TopologyProposal
topology_proposal = TopologyProposal(
new_topology=topology,
new_system=system,
old_topology=topology,
old_system=system,
old_chemical_state_key='',
new_chemical_state_key='',
logp_proposal=0.0,
new_to_old_atom_map=new_to_old_atom_map,
metadata={'test': 0.0})
for ncmc_nsteps in [0, 1, 50]:
f = partial(check_alchemical_null_elimination,
topology_proposal,
positions,
ncmc_nsteps=ncmc_nsteps)
f.description = "Testing alchemical null elimination for '%s' with %d NCMC steps" % (
molecule_name, ncmc_nsteps)
yield f
def generateOEMolFromTopologyResidue(residue,
geometry=False,
tripos_atom_names=False):
"""
Generate an OpenEye OEMol molecule from an OpenMM Topology Residue.
Parameters
----------
residue : simtk.openmm.app.topology.Residue
The topology Residue from which an OEMol is to be created.
An Exception will be thrown if this residue has external bonds.
geometry : bool, optional, default=False
If True, will generate a single configuration with OEOmega.
Note that stereochemistry will be *random*.
tripos_atom_names : bool, optional, default=False
If True, will generate and assign Tripos atom names.
Returns
-------
molecule : openeye.oechem.OEMol
The OEMol molecule corresponding to the topology.
Atom order will be preserved and bond orders assigned.
The Antechamber `bondtype` program will be used to assign bond orders, and these
will be converted back into OEMol bond type assignments.
Note that there is no way to preserve stereochemistry since `Residue` does
not note stereochemistry in any way.
"""
# Raise an Exception if this residue has external bonds.
if len(list(residue.external_bonds())) > 0:
raise Exception(
"Cannot generate an OEMol from residue '%s' because it has external bonds."
% residue.name)
from openeye import oechem
# Create OEMol where all atoms have bond order 1.
molecule = oechem.OEMol()
molecule.SetTitle(residue.name) # name molecule after first residue
for atom in residue.atoms():
oeatom = molecule.NewAtom(atom.element.atomic_number)
oeatom.SetName(atom.name)
oeatom.AddData("topology_index", atom.index)
oeatoms = {oeatom.GetName(): oeatom for oeatom in molecule.GetAtoms()}
for (atom1, atom2) in residue.bonds():
order = 1
molecule.NewBond(oeatoms[atom1.name], oeatoms[atom2.name], order)
# Write out a mol2 file without altering molecule.
import tempfile
tmpdir = tempfile.mkdtemp()
mol2_input_filename = os.path.join(tmpdir,
'molecule-before-bond-perception.mol2')
ac_output_filename = os.path.join(tmpdir,
'molecule-after-bond-perception.ac')
ofs = oechem.oemolostream(mol2_input_filename)
m2h = True
substruct = False
oechem.OEWriteMol2File(ofs, molecule, m2h, substruct)
ofs.close()
# Run Antechamber bondtype
import subprocess
#command = 'bondtype -i %s -o %s -f mol2 -j full' % (mol2_input_filename, ac_output_filename)
command = 'antechamber -i %s -fi mol2 -o %s -fo ac -j 2' % (
mol2_input_filename, ac_output_filename)
[status, output] = getstatusoutput(command)
# Define mapping from GAFF bond orders to OpenEye bond orders.
order_map = {1: 1, 2: 2, 3: 3, 7: 1, 8: 2, 9: 5, 10: 5}
# Read bonds.
infile = open(ac_output_filename)
lines = infile.readlines()
infile.close()
antechamber_bond_types = list()
for line in lines:
elements = line.split()
if elements[0] == 'BOND':
antechamber_bond_types.append(int(elements[4]))
oechem.OEClearAromaticFlags(molecule)
for (bond, antechamber_bond_type) in zip(molecule.GetBonds(),
antechamber_bond_types):
#bond.SetOrder(order_map[antechamber_bond_type])
bond.SetIntType(order_map[antechamber_bond_type])
oechem.OEFindRingAtomsAndBonds(molecule)
oechem.OEKekulize(molecule)
oechem.OEAssignFormalCharges(molecule)
oechem.OEAssignAromaticFlags(molecule, oechem.OEAroModelOpenEye)
# Clean up.
os.unlink(mol2_input_filename)
os.unlink(ac_output_filename)
os.rmdir(tmpdir)
# Generate Tripos atom names if requested.
if tripos_atom_names:
oechem.OETriposAtomNames(molecule)
# Assign geometry
if geometry:
from openeye import oeomega
omega = oeomega.OEOmega()
omega.SetMaxConfs(1)
omega.SetIncludeInput(False)
omega.SetStrictStereo(False)
omega(molecule)
return molecule
def process(self, mol, port):
kT_in_kcal_per_mole = self.kT.value_in_unit(unit.kilocalories_per_mole)
# Retrieve data about which molecule we are processing
title = mol.GetTitle()
with TemporaryDirectory() as output_directory:
try:
# Print out which molecule we are processing
self.log.info('Processing {} in {}.'.format(
title, output_directory))
# Check that molecule is charged.
if not molecule_is_charged(mol):
raise Exception(
'Molecule %s has no charges; input molecules must be charged.'
% mol.GetTitle())
# Write the receptor.
pdbfilename = os.path.join(output_directory, 'receptor.pdb')
with oechem.oemolostream(pdbfilename) as ofs:
res = oechem.OEWriteConstMolecule(ofs, self.receptor)
if res != oechem.OEWriteMolReturnCode_Success:
raise RuntimeError(
"Error writing receptor: {}".format(res))
# Write the specified molecule out to a mol2 file without changing its name.
mol2_filename = os.path.join(output_directory, 'input.mol2')
ofs = oechem.oemolostream(mol2_filename)
oechem.OEWriteMol2File(ofs, mol)
# Undo oechem fuckery with naming mol2 substructures `<0>`
from YankCubes.utils import unfuck_oechem_mol2_file
unfuck_oechem_mol2_file(mol2_filename)
# Run YANK on the specified molecule.
from yank.yamlbuild import YamlBuilder
yaml = self.construct_yaml(output_directory=output_directory)
yaml_builder = YamlBuilder(yaml)
yaml_builder.build_experiments()
self.log.info(
'Ran Yank experiments for molecule {}.'.format(title))
# Analyze the binding free energy
# TODO: Use yank.analyze API for this
from YankCubes.analysis import analyze
store_directory = os.path.join(output_directory, 'experiments')
[DeltaG_binding, dDeltaG_binding] = analyze(store_directory)
"""
# Extract trajectory (DEBUG)
from yank.analyze import extract_trajectory
trajectory_filename = 'trajectory.pdb'
store_filename = os.path.join(store_directory, 'complex.pdb')
extract_trajectory(trajectory_filename, store_filename, state_index=0, keep_solvent=False,
discard_equilibration=True, image_molecules=True)
ifs = oechem.oemolistream(trajectory_filename)
ifs.SetConfTest(oechem.OEAbsCanonicalConfTest()) # load multi-conformer molecule
mol = oechem.OEMol()
for mol in ifs.GetOEMols():
print (mol.GetTitle(), "has", mol.NumConfs(), "conformers")
ifs.close()
os.remove(trajectory_filename)
"""
# Attach binding free energy estimates to molecule
oechem.OESetSDData(mol, 'DeltaG_yank_binding',
str(DeltaG_binding * kT_in_kcal_per_mole))
oechem.OESetSDData(mol, 'dDeltaG_yank_binding',
str(dDeltaG_binding * kT_in_kcal_per_mole))
self.log.info(
'Analyzed and stored binding free energy for molecule {}.'.
format(title))
# Emit molecule to success port.
self.success.emit(mol)
except Exception as e:
self.log.info(
'Exception encountered when processing molecule {}.'.
format(title))
# Attach error message to the molecule that failed
# TODO: If there is an error in the leap setup log,
# we should capture that and attach it to the failed molecule.
self.log.error(traceback.format_exc())
mol.SetData('error', str(e))
# Return failed molecule
self.failure.emit(mol)
def mk_conformers_epik(options, molecule, maxconf=99, verbose=True, pH=7):
"""
Enumerate the list of conformers and associated properties for each protonation and tautomeric state using epik from the Schrodinger Suite.
Parameters
----------
options
molecule : openeye.oechem
The molecule read from the PDB whose protomer and tautomer states are to be enumerated.
maxconf : int, optional, default=128
Maximum number of protomers/tautomers to generate.
pH : float, optional, default=7.0
pH to use for conformer enumeration
Returns
-------
conformers : list of Conformer
The list of protomers/tautomers generated.
"""
from schrodinger import structure # Requires Schrodinger Suite
# Write mol2 file.
if verbose: print "Writing input file as mol2..."
outmol = oechem.OEMol(molecule)
ofs = oechem.oemolostream()
ofs.open('epik-input.mol2')
oechem.OEWriteMolecule(ofs, outmol)
ofs.close()
# Use low level writer to get atom names correct.
ofs = oechem.oemolostream()
ofs.open('epik-input.mol2')
for (dest_atom, src_atom) in zip(outmol.GetAtoms(), molecule.GetAtoms()):
dest_atom.SetName(src_atom.GetName())
oechem.OEWriteMol2File(ofs, outmol, True)
ofs.close()
# Write mol2 file.
if verbose: print "Writing input file as sdf..."
outmol = oechem.OEMol(molecule)
ofs = oechem.oemolostream()
ofs.open('epik-input.sdf')
oechem.OEWriteMolecule(ofs, outmol)
ofs.close()
# Write pdb file.
if verbose: print "Writing input file as pdb..."
outmol = oechem.OEMol(molecule)
ofs = oechem.oemolostream()
ofs.open('epik-input.pdb')
oechem.OEWriteMolecule(ofs, outmol)
ofs.close()
# Write input for epik.
if verbose: print "Converting input file to Maestro format..."
reader = structure.StructureReader("epik-input.mol2")
writer = structure.StructureWriter("epik-input.mae")
for st in reader:
writer.append(st)
reader.close()
writer.close()
# Run epik to enumerate protomers/tautomers and get associated state penalties.
if verbose: print "Running Epik..."
cmd = '%s/epik -imae epik-input.mae -omae epik-output.mae -pht 10.0 -ms 100 -nt -pKa_atom -ph %f -WAIT' % (os.environ['SCHRODINGER'], pH)
output = commands.getoutput(cmd)
if verbose: print output
# Convert output from epik from .mae to .sdf.
if verbose: print "Converting output file to SDF..."
reader = structure.StructureReader("epik-output.mae")
writer = structure.StructureWriter("epik-output.sdf")
for st in reader:
writer.append(st)
reader.close()
writer.close()
# Also convert to .mol2.
if verbose: print "Converting output file to MOL2..."
reader = structure.StructureReader("epik-output.mae")
writer = structure.StructureWriter("epik-output.mol2")
for st in reader:
writer.append(st)
reader.close()
writer.close()
# Find minimum charge.
ifs = oechem.oemolistream()
ifs.open('epik-output.mol2')
molecule = oechem.OEGraphMol()
min_formal_charge = 1000
while oechem.OEReadMolecule(ifs, molecule):
# Check aromaticity.
oechem.OEAssignAromaticFlags(molecule)
# Assign formal charge
oechem.OEAssignFormalCharges(molecule)
formal_charge = 0
for atom in molecule.GetAtoms():
formal_charge += atom.GetFormalCharge()
# Keep most negative formal charge
min_formal_charge = min(min_formal_charge, formal_charge)
ifs.close()
if verbose: print "Minimum formal charge = %d" % min_formal_charge
# Read conformers from SDF and mol2 (converted from Epik).
if verbose: print "Reading conformers from SDF..."
ifs_sdf = oechem.oemolistream()
ifs_sdf.SetFormat(oechem.OEFormat_SDF)
ifs_sdf.open('epik-output.sdf')
sdf_molecule = oechem.OEGraphMol()
ifs_mol2 = oechem.oemolistream()
ifs_mol2.open('epik-output.mol2')
mol2_molecule = oechem.OEGraphMol()
conformer_index = 1
conformers = list()
while oechem.OEReadMolecule(ifs_sdf, sdf_molecule):
if verbose: print "Conformer %d" % conformer_index
# Read corresponding mol2 molecule.
oechem.OEReadMolecule(ifs_mol2, mol2_molecule)
oechem.OEAssignAromaticFlags(mol2_molecule) # check aromaticity
# Make a copy of the mol2 molecule.
molecule = oechem.OEMol(mol2_molecule)
# Set name
name = options.ligand+'%02d' % conformer_index
molecule.SetTitle(name)
# Assign formal charge
oechem.OEAssignFormalCharges(molecule)
formal_charge = 0.0
for atom in molecule.GetAtoms():
formal_charge += atom.GetFormalCharge()
if verbose: print "formal charge: %d" % formal_charge
# DEBUG: Write mol2 file before assigning charges.
if verbose: print "Writing %s to mol2..." % name
outmol = oechem.OEMol(molecule)
ofs = oechem.oemolostream()
ofs.open(name + '.mol2')
oechem.OEWriteMolecule(ofs, outmol)
ofs.close()
# Assign canonical AM1BCC charges.
try:
if verbose: print "Assigning AM1-BCC charges..."
#assign_canonical_am1bcc_charges(molecule)
assign_simple_am1bcc_charges(molecule)
except Exception as e:
print str(e)
continue
# Get Epik data.
epik_Ionization_Penalty = float(oechem.OEGetSDData(sdf_molecule, "r_epik_Ionization_Penalty"))
epik_Ionization_Penalty_Charging = float(oechem.OEGetSDData(sdf_molecule, "r_epik_Ionization_Penalty_Charging"))
epik_Ionization_Penalty_Neutral = float(oechem.OEGetSDData(sdf_molecule, "r_epik_Ionization_Penalty_Neutral"))
epik_State_Penalty = float(oechem.OEGetSDData(sdf_molecule, "r_epik_State_Penalty"))
epik_Tot_Q = int(oechem.OEGetSDData(sdf_molecule, "i_epik_Tot_Q"))
# Compute number of protons.
nprotons = epik_Tot_Q - min_formal_charge + 1
# Compute effective pKa.
import numpy as np
kT = 298 * 6.022e23 * 1.381e-23 / 4184 # kcal/mol for 298 K
pKa = options.pH - epik_State_Penalty / (nprotons * kT * np.log(10))
print "effective pKa = %8.3f" % pKa
# DEBUG
print "%24s : pKa penalty %8.3f kcal/mol | tautomer penalty %8.3f kcal/mol | total state penalty %8.3f\n" % (name, epik_Ionization_Penalty, epik_State_Penalty - epik_Ionization_Penalty, epik_State_Penalty)
# Create a conformer and append it to the list.
conformer = Conformer(name, epik_Tot_Q, molecule, state_penalty=epik_State_Penalty)
conformers.append(conformer)
print epik_Tot_Q # DEBUG
# Increment counter.
conformer_index += 1
ifs_sdf.close()
ifs_mol2.close()
if verbose: print "%d protomer/tautomer states were enumerated" % len(conformers)
return conformers
def create_openeye_molecule(pdb, options, verbose=True):
"""
Create OpenEye molecule from PDB representation.
The molecule will have hydrogens added and be normalized, but the overall geometry will not be altered.
Parameters
----------
pdb : Pdb
The PDB-extracted entries for the ligand.
Returns
-------
molecule : openeye.oechem.OEMol
Molecule representation.
options : options struct
Options structure.
"""
# Create a molecule container.
molecule = oechem.OEGraphMol()
# Open a PDB file reader from the stored PDB string representation of HETATM and CONECT records.
print pdb.pdb_extract
ifs = oechem.oemolistream()
ifs.openstring(pdb.pdb_extract)
flavor = oechem.OEIFlavor_Generic_Default | oechem.OEIFlavor_PDB_Default | oechem.OEIFlavor_PDB_ALL
ifs.SetFlavor(oechem.OEFormat_PDB, flavor)
oechem.OEReadPDBFile(ifs, molecule)
# Add explicit hydrogens.
oechem.OEDetermineConnectivity(molecule)
oechem.OEFindRingAtomsAndBonds(molecule)
oechem.OEAssignAromaticFlags(molecule) # check aromaticity
oechem.OEPerceiveBondOrders(molecule)
# We must assign implicit hydrogens first so that the valence model will be correct.
oechem.OEAssignImplicitHydrogens(molecule)
oechem.OEAssignFormalCharges(molecule)
# Now add explicit hydrogens.
polarOnly = False
set3D = True
oechem.OEAddExplicitHydrogens(molecule, polarOnly, set3D)
# TODO: Sequentially number hydrogen atoms.
# Perceive stereochemostry.
oechem.OEPerceiveChiral(molecule)
# Set title.
molecule.SetTitle(options.ligand)
# Write out PDB form of this molecule.
# TODO: Fix atom numbering.
#if verbose: print "Writing input molecule as PDB..."
#outmol = oechem.OEMol(molecule)
#ofs = oechem.oemolostream()
#flavor = oechem.OEOFlavor_Generic_Default | oechem.OEOFlavor_PDB_Default
#ofs.SetFlavor(oechem.OEFormat_PDB, flavor)
#ofs.open(options.ligand + '.pdb')
#oechem.OEWriteMolecule(ofs, outmol)
#ofs.close()
# Write mol2 file for this molecule.
if verbose: print "Writing input molecule as mol2..."
outmol = oechem.OEMol(molecule)
ofs = oechem.oemolostream()
filename = options.ligand + '.mol2'
ofs.open(filename)
oechem.OEWriteMolecule(ofs, outmol)
ofs.close()
# Use low level writer to get atom names correct.
ofs = oechem.oemolostream()
ofs.open(filename)
for (dest_atom, src_atom) in zip(outmol.GetAtoms(), molecule.GetAtoms()):
dest_atom.SetName(src_atom.GetName())
oechem.OEWriteMol2File(ofs, outmol, True)
ofs.close()
# Read and write in PDB format.
if verbose: print "Converting mol2 to PDB..."
ifs = oechem.oemolistream()
ofs = oechem.oemolostream()
if ifs.open(options.ligand + '.mol2'):
if ofs.open(options.ligand + '.pdb'):
for mol in ifs.GetOEGraphMols():
oechem.OEWriteMolecule(ofs, mol)
return molecule
def run_epik(molecule, maxconf=99, verbose=False, outfile=None):
"""
Enumerate the list of conformers and associated properties for each protonation and tautomeric state using epik from the Schrodinger Suite.
Parameters
----------
options
molecule : openeye.oechem
The molecule read from the PDB whose protomer and tautomer states are to be enumerated.
maxconf : int, optional, default=128
Maximum number of protomers/tautomers to generate.
verbose : bool, optiona, default=False
If True, outputs more information.
outfile : file, optional, default=None
If specified, record compiled pKas to this output file.
"""
from schrodinger import structure # Requires Schrodinger Suite
# Write mol2 file.
if verbose: print "Writing input file as mol2..."
outmol = oechem.OEMol(molecule)
ofs = oechem.oemolostream()
ofs.open('epik-input.mol2')
oechem.OEWriteMolecule(ofs, outmol)
ofs.close()
# Use low level writer to get atom names correct.
ofs = oechem.oemolostream()
ofs.open('epik-input.mol2')
for (dest_atom, src_atom) in zip(outmol.GetAtoms(), molecule.GetAtoms()):
dest_atom.SetName(src_atom.GetName())
oechem.OEWriteMol2File(ofs, outmol, True)
ofs.close()
# Write mol2 file.
if verbose: print "Writing input file as sdf..."
outmol = oechem.OEMol(molecule)
ofs = oechem.oemolostream()
ofs.open('epik-input.sdf')
oechem.OEWriteMolecule(ofs, outmol)
ofs.close()
# Write pdb file.
if verbose: print "Writing input file as pdb..."
outmol = oechem.OEMol(molecule)
ofs = oechem.oemolostream()
ofs.open('epik-input.pdb')
oechem.OEWriteMolecule(ofs, outmol)
ofs.close()
# Write input for epik.
if verbose: print "Converting input file to Maestro format..."
reader = structure.StructureReader("epik-input.mol2")
writer = structure.StructureWriter("epik-input.mae")
for st in reader:
writer.append(st)
reader.close()
writer.close()
# Run epik to enumerate predicted pKas.
if verbose: print "Running Epik..."
cmd = '%s/epik -imae epik-input.mae -omae epik-output.mae -scan -lowest_pka 1.0 -highest_pka 12.0 -WAIT' % (os.environ['SCHRODINGER'])
output = commands.getoutput(cmd)
if verbose: print output
# Extract pKas from Epik output.
cmd = 'grep conjugate epik-output.log'
output = commands.getoutput(cmd)
pKas = list()
for line in output.split('\n'):
print "> %s" % line
# Extract information
pKa = float(line[0:7].strip())
type = line[9:13]
atom_index = int(line[24:28].strip())
notes = line[31:]
state = dict({ 'pKa' : pKa, 'type' : type, 'atom_index' : atom_index, 'notes' : notes })
pKas.append(state)
print "pKa %8.3f %s atom %d type %s" % (pKa, type, atom_index, notes)
# Store output.
command = 'cp epik-output.log epik-output.%s.log' % molecule.GetTitle()
commands.getoutput(command)
# Write pKas only to file, if desired.
if outfile:
outfile.write('%s %d' % (molecule.GetTitle(), len(pKas)))
for pKa in pKas:
outfile.write(' %8.2f' % (pKa['pKa']))
outfile.write('\n')
return
