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import sys
import math
import simtk.openmm.app.element as element
import simtk.unit as unit
elements = {}
for elem in element.Element._elements_by_symbol.values():
num = elem.atomic_number
if num not in elements or elem.mass < elements[num].mass:
elements[num] = elem
OTHER = 0
ATOMS = 1
CONNECT = 2
CONNECTIVITY = 3
RESIDUECONNECT = 4
section = OTHER
residueAtoms = {}
residueBonds = {}
residueConnections = {}
types = []
masses = {}
resAtomTypes = {}
vdwEquivalents = {}
vdw = {}
charge = {}
bonds = []
angles = []
torsions = []
impropers = []
charge14scale = 1.0/1.2
epsilon14scale = 0.5
skipResidues = ['CIO', 'IB'] # "Generic" ions defined by Amber, which are identical to other real ions
skipClasses = ['OW', 'HW'] # Skip water atoms, since we define these in separate files
def addAtom(residue, atomName, atomClass, element, charge):
if residue is None:
return
residueAtoms[residue].append([atomName, len(types)])
types.append((atomClass, element, charge))
def addBond(residue, atom1, atom2):
if residue is None:
return
residueBonds[residue].append((atom1, atom2))
def addExternalBond(residue, atom):
if residue is None:
return
if atom != -1:
residueConnections[residue] += [atom]
# Load input files.
for inputfile in sys.argv[1:]:
if inputfile.endswith('.lib') or inputfile.endswith('.off'):
# Read a library file
for line in open(inputfile):
if line.startswith('!entry'):
fields = line.split('.')
residue = fields[1]
if residue in skipResidues:
residue = None
continue
key = fields[3].split()[0]
if key == 'atoms':
section = ATOMS
residueAtoms[residue] = []
residueBonds[residue] = []
residueConnections[residue] = []
elif key == 'connect':
section = CONNECT
elif key == 'connectivity':
section = CONNECTIVITY
elif key == 'residueconnect':
section = RESIDUECONNECT
else:
section = OTHER
elif section == ATOMS:
fields = line.split()
atomName = fields[0][1:-1]
atomClass = fields[1][1:-1]
if fields[6] == '-1':
# Workaround for bug in some Amber files.
if atomClass[0] == 'C':
elem = elements[6]
elif atomClass[0] == 'H':
elem = elements[1]
else:
raise ValueError('Illegal atomic number: '+line)
else:
elem = elements[int(fields[6])]
charge = float(fields[7])
addAtom(residue, atomName, atomClass, elem, charge)
elif section == CONNECT:
addExternalBond(residue, int(line)-1)
elif section == CONNECTIVITY:
fields = line.split()
addBond(residue, int(fields[0])-1, int(fields[1])-1)
elif section == RESIDUECONNECT:
# Some Amber files have errors in them, incorrectly listing atoms that should not be
# connected in the first two positions. We therefore rely on the "connect" section for
# those, using this block only for other external connections.
for atom in [int(x)-1 for x in line.split()[2:]]:
addExternalBond(residue, atom)
elif inputfile.endswith('.in'):
lines = open(inputfile).read().split('\n')
i = 2
while True:
if lines[i].strip() == 'STOP':
break
i += 1
residue = lines[i].strip()
# Hack to get unique residue names, since different files use the same names.
if inputfile.endswith('nt.in'):
residue = 'N'+residue
if inputfile.endswith('ct.in'):
residue = 'C'+residue
residueAtoms[residue] = []
residueBonds[residue] = []
residueConnections[residue] = []
atoms = []
mainchain = []
i += 7
while len(lines[i].rstrip()) > 0:
fields = lines[i].split()
atoms.append((fields[1], fields[2], float(fields[10]))) # (name, type, charge)
if fields[3] == 'M':
mainchain.append(len(atoms)-1)
bondedTo = int(fields[4])-4
if bondedTo >= 0:
addBond(residue, len(atoms)-1, bondedTo)
i += 1
while True:
if lines[i].strip() == 'LOOP':
i += 1
while len(lines[i].rstrip()) > 0:
fields = lines[i].strip().split()
bondFrom = [j for j in range(len(atoms)) if fields[0] == atoms[j][0]][0]
bondTo = [j for j in range(len(atoms)) if fields[1] == atoms[j][0]][0]
addBond(residue, bondFrom, bondTo)
i += 1
if lines[i].strip() != 'DONE':
i += 1
continue
for atom in atoms:
try:
el = element.Element.getBySymbol(atom[1][0])
except:
el = None
addAtom(residue, atom[0], atom[1], el, atom[2])
# Hack for figuring out external bonds. We'll have to fix up disulfide bonds and capping groups manually.
if len(mainchain) > 0 and not inputfile.endswith('nt.in'):
addExternalBond(residue, mainchain[0])
if len(mainchain) > 1 and not inputfile.endswith('ct.in'):
addExternalBond(residue, mainchain[-1])
i += 1
break
elif inputfile.endswith('.dat'):
# Read a force field file.
block = 0
continueTorsion = False
for line in open(inputfile):
line = line.strip()
if block == 0: # Title
block += 1
elif block == 1: # Mass
fields = line.split()
if len(fields) == 0:
block += 1
else:
masses[fields[0]] = float(fields[1])
elif block == 2: # Hydrophilic atoms
block += 1
elif block == 3: # Bonds
if len(line) == 0:
block += 1
elif '-' in line:
fields = line[5:].split()
bonds.append((line[:2].strip(), line[3:5].strip(), fields[0], fields[1]))
elif block == 4: # Angles
if len(line) == 0:
block += 1
else:
fields = line[8:].split()
angles.append((line[:2].strip(), line[3:5].strip(), line[6:8].strip(), fields[0], fields[1]))
elif block == 5: # Torsions
if len(line) == 0:
block += 1
else:
fields = line[11:].split()
periodicity = int(float(fields[3]))
if continueTorsion:
torsions[-1] += [float(fields[1])/float(fields[0]), fields[2], abs(periodicity)]
else:
torsions.append([line[:2].strip(), line[3:5].strip(), line[6:8].strip(), line[9:11].strip(), float(fields[1])/float(fields[0]), fields[2], abs(periodicity)])
continueTorsion = (periodicity < 0)
elif block == 6: # Improper torsions
if len(line) == 0:
block += 1
else:
fields = line[11:].split()
impropers.append((line[:2].strip(), line[3:5].strip(), line[6:8].strip(), line[9:11].strip(), fields[0], fields[1], fields[2]))
elif block == 7: # 10-12 hbond potential
if len(line) == 0:
block += 1
elif block == 8: # VDW equivalents
if len(line) == 0:
block += 1
else:
fields = line.split()
for atom in fields[1:]:
vdwEquivalents[atom] = fields[0]
elif block == 9: # VDW type
block += 1
vdwType = line.split()[1]
if vdwType not in ['RE', 'AC']:
raise ValueError('Nonbonded type (KINDNB) must be RE or AC')
elif block == 10: # VDW parameters
if len(line) == 0:
block += 1
else:
fields = line.split()
vdw[fields[0]] = (fields[1], fields[2])
else:
# Assume it's a frcmod file.
block = ''
continueTorsion = False
first = True
for line in open(inputfile):
line = line.strip()
if len(line) == 0 or first:
block = None
first = False
elif block is None:
block = line
elif block.startswith('MASS'):
fields = line.split()
masses[fields[0]] = float(fields[1])
elif block.startswith('BOND'):
fields = line[5:].split()
bonds.append((line[:2].strip(), line[3:5].strip(), fields[0], fields[1]))
elif block.startswith('ANGL'):
fields = line[8:].split()
angles.append((line[:2].strip(), line[3:5].strip(), line[6:8].strip(), fields[0], fields[1]))
elif block.startswith('DIHE'):
fields = line[11:].split()
periodicity = int(float(fields[3]))
if continueTorsion:
torsions[-1] += [float(fields[1])/float(fields[0]), fields[2], abs(periodicity)]
else:
torsions.append([line[:2].strip(), line[3:5].strip(), line[6:8].strip(), line[9:11].strip(), float(fields[1])/float(fields[0]), fields[2], abs(periodicity)])
continueTorsion = (periodicity < 0)
elif block.startswith('IMPR'):
fields = line[11:].split()
impropers.append((line[:2].strip(), line[3:5].strip(), line[6:8].strip(), line[9:11].strip(), fields[0], fields[1], fields[2]))
elif block.startswith('NONB'):
fields = line.split()
vdw[fields[0]] = (fields[1], fields[2])
# Reduce the list of atom types. If multiple hydrogens are bound to the same heavy atom,
# they should all use the same type.
removeType = [False]*len(types)
for res in residueAtoms:
if res not in residueBonds:
continue
atomBonds = [[] for _ in residueAtoms[res]]
for bond in residueBonds[res]:
atomBonds[bond[0]].append(bond[1])
atomBonds[bond[1]].append(bond[0])
for index, atom in enumerate(residueAtoms[res]):
hydrogens = [x for x in atomBonds[index] if types[residueAtoms[res][x][1]][1] == element.hydrogen]
for h in hydrogens[1:]:
removeType[residueAtoms[res][h][1]] = True
residueAtoms[res][h][1] = residueAtoms[res][hydrogens[0]][1]
newTypes = []
replaceWithType = [0]*len(types)
for i in range(len(types)):
if not removeType[i]:
newTypes.append(types[i])
replaceWithType[i] = len(newTypes)-1
types = newTypes
for res in residueAtoms:
for atom in residueAtoms[res]:
atom[1] = replaceWithType[atom[1]]
# Create the XML output.
def fix(atomClass):
if atomClass == 'X':
return ''
return atomClass
print "<ForceField>"
print " <AtomTypes>"
for index, type in enumerate(types):
if type[1] is None:
el = ""
mass = 0
else:
el = type[1].symbol
mass = type[1].mass.value_in_unit(unit.amu)
print """ <Type name="%d" class="%s" element="%s" mass="%s"/>""" % (index, type[0], el, mass)
print " </AtomTypes>"
print " <Residues>"
for res in sorted(residueAtoms):
print """ <Residue name="%s">""" % res
for atom in residueAtoms[res]:
print " <Atom name=\"%s\" type=\"%d\"/>" % tuple(atom)
if res in residueBonds:
for bond in residueBonds[res]:
print """ <Bond from="%d" to="%d"/>""" % bond
if res in residueConnections:
for bond in residueConnections[res]:
print """ <ExternalBond from="%d"/>""" % bond
print " </Residue>"
print " </Residues>"
print " <HarmonicBondForce>"
processed = set()
for bond in bonds:
signature = (bond[0], bond[1])
if signature in processed:
continue
if any([c in skipClasses for c in signature]):
continue
processed.add(signature)
length = float(bond[3])*0.1
k = float(bond[2])*2*100*4.184
print """ <Bond class1="%s" class2="%s" length="%s" k="%s"/>""" % (bond[0], bond[1], str(length), str(k))
print " </HarmonicBondForce>"
print " <HarmonicAngleForce>"
processed = set()
for angle in angles:
signature = (angle[0], angle[1], angle[2])
if signature in processed:
continue
if any([c in skipClasses for c in signature]):
continue
processed.add(signature)
theta = float(angle[4])*math.pi/180.0
k = float(angle[3])*2*4.184
print """ <Angle class1="%s" class2="%s" class3="%s" angle="%s" k="%s"/>""" % (angle[0], angle[1], angle[2], str(theta), str(k))
print " </HarmonicAngleForce>"
print " <PeriodicTorsionForce>"
processed = set()
for tor in reversed(torsions):
signature = (fix(tor[0]), fix(tor[1]), fix(tor[2]), fix(tor[3]))
if signature in processed:
continue
if any([c in skipClasses for c in signature]):
continue
processed.add(signature)
tag = " <Proper class1=\"%s\" class2=\"%s\" class3=\"%s\" class4=\"%s\"" % signature
i = 4
while i < len(tor):
index = i//3
periodicity = int(float(tor[i+2]))
phase = float(tor[i+1])*math.pi/180.0
k = tor[i]*4.184
tag += " periodicity%d=\"%d\" phase%d=\"%s\" k%d=\"%s\"" % (index, periodicity, index, str(phase), index, str(k))
i += 3
tag += "/>"
print tag
processed = set()
for tor in reversed(impropers):
signature = (fix(tor[2]), fix(tor[0]), fix(tor[1]), fix(tor[3]))
if signature in processed:
continue
if any([c in skipClasses for c in signature]):
continue
processed.add(signature)
tag = " <Improper class1=\"%s\" class2=\"%s\" class3=\"%s\" class4=\"%s\"" % signature
i = 4
while i < len(tor):
index = i//3
periodicity = int(float(tor[i+2]))
phase = float(tor[i+1])*math.pi/180.0
k = float(tor[i])*4.184
tag += " periodicity%d=\"%d\" phase%d=\"%s\" k%d=\"%s\"" % (index, periodicity, index, str(phase), index, str(k))
i += 3
tag += "/>"
print tag
print " </PeriodicTorsionForce>"
print """ <NonbondedForce coulomb14scale="%g" lj14scale="%s">""" % (charge14scale, epsilon14scale)
sigmaScale = 0.1*2.0/(2.0**(1.0/6.0))
for index, type in enumerate(types):
atomClass = type[0]
q = type[2]
if atomClass in vdwEquivalents:
atomClass = vdwEquivalents[atomClass]
if atomClass in vdw:
params = [float(x) for x in vdw[atomClass]]
if vdwType == 'RE':
sigma = params[0]*sigmaScale
epsilon = params[1]*4.184
else:
sigma = (params[0]/params[1])**(1.0/6.0)
epsilon = 4.184*params[1]*params[1]/(4*params[0])
else:
sigma = 1
epsilon = 0
if sigma == 0 or epsilon == 0:
sigma, epsilon = 1, 0
if q != 0 or epsilon != 0:
print """ <Atom type="%d" charge="%s" sigma="%s" epsilon="%s"/>""" % (index, q, sigma, epsilon)
print " </NonbondedForce>"
print "</ForceField>"
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