def buildSugar(self, baseAtoms, pucker):
"""Build a sugar of the specified pucker onto a base
ARGUMENTS:
baseAtoms - a dictionary of base atoms in the form atomName:[x, y, z]
Note that this dictionary MUST contain the C1' atom
pucker - the pucker of the sugar to be built (passed as an integer, either 2 or 3)
RETURNS:
coordinates for a sugar of the specified pucker in anti configuration with the base
"""
#fetch the appropriate sugar structure
if pucker == 3:
sugarAtoms = self.__c3pAtoms
elif pucker == 2:
sugarAtoms = self.__c2pAtoms
else:
raise "BuildInitSugar called with unrecognized pucker: " + str(pucker)
#I don't have to worry about accidentally modifying the original atom dictionaries, since
#rotateAtoms effectively makes a deep copy
#figure out which base atoms to use for alignment
if baseAtoms.has_key("N9"):
Natom = "N9"
Catom = "C4"
else:
Natom = "N1"
Catom = "C2"
#rotate the sugar so the glycosidic bond is at the appropriate angle
#first, calculate an axis for this rotation
translatedBaseN = minus(baseAtoms[Natom], baseAtoms["C1'"])
sugarN = sugarAtoms[Natom]
axis = crossProd(sugarN, translatedBaseN)
angle = torsion(translatedBaseN, axis, (0,0,0), sugarN)
#if either angle or magnitude(axis) is 0, then the glycosidic bond is already oriented appropriately
if not(angle == 0 or magnitude(axis) == 0):
sugarAtoms = rotateAtoms(sugarAtoms, axis, angle)
#next, rotate the sugar so that chi is appropriate
translatedBaseC = minus(baseAtoms[Catom], baseAtoms["C1'"])
curChi = torsion(translatedBaseC, translatedBaseN, [0,0,0], sugarAtoms["O4'"])
sugarAtoms = rotateAtoms(sugarAtoms, translatedBaseN, curChi - STARTING_CHI)
#remove the unnecessary atoms from the sugarAtoms dict
del sugarAtoms["N1"]
del sugarAtoms["N9"]
#translate the sugar to the C1' atom of the base
sugarAtoms = dict([(atom, plus(coords, baseAtoms["C1'"])) for (atom, coords) in sugarAtoms.iteritems()])
return sugarAtoms
def flipBase(self, curBase):
"""Flip the base anti/syn
ARGUMENTS:
curBase - the current base object in the form [baseType, baseCoordinates]
RETURNS:
the base object with rotated coordinates
NOTE:
This function does not necessarily simply rotate about chi. When flipping a purine, it also adjusts
the glycosidic bond position so that it the base a chance of staying in the density
"""
(baseType, curBaseCoords) = curBase
curC1coords = curBaseCoords["C1'"]
newBaseCoords = {}
#translate the base to the origin
for atomName, curAtomCoords in curBaseCoords.items():
newBaseCoords[atomName] = minus(curBaseCoords[atomName], curC1coords)
#the rotation axis is the same as the alignment vector for mutating the base
#for pyrimidines, the axis is C1'-C4
#for purines, the axis is from C1' to the center of the C4-C5 bond
axis = None
if baseType == "C" or baseType == "U":
axis = newBaseCoords["C4"]
else:
axis = plus(newBaseCoords["C4"], newBaseCoords["C5"])
axis = scalarProd(1.0/2.0, axis)
#rotate the base 180 degrees about the axis
newBaseCoords = rotateAtoms(newBaseCoords, axis, 180, curC1coords)
return [baseType, newBaseCoords]
def rotateSugar(antiSugarCoords, atoms, newChi = "syn"):
"""Given a sugar in anti configuration, rotate it to a new configuration (such as syn or high-anti).
ARGUMENTS:
antiSugarCoords - a dictionary containing a sugar in anti configuration in the format atomName: [x, y, z]
typically, this dictionary is generated by a BuildInitSugar object
atoms - a dictionary containing base coordinates in the format atomName: [x, y, z]
OPTIONAL ARGUMENTS:
newChi - the chi value to rotate the sugar to
may be "syn", "high-anti", or a number (in degrees)
defaults to "syn"
RETURNS:
synSugarCoords - a dictionary containing a sugar in syn configuration in the format atomName: [x, y, z]
"""
if newChi == "syn":
newChi = SYN_CHI
elif newChi == "high-anti":
newChi = HIGH_ANTI_CHI
#translate the sugar coordinates to the origin
synSugarCoords = dict([(atom, minus(coords, atoms["C1'"])) for (atom, coords) in antiSugarCoords.iteritems()])
#rotate the sugar
if atoms.has_key("N9"):
baseN = "N9"
else:
baseN = "N1"
axis = minus(atoms[baseN], atoms["C1'"])
synSugarCoords = rotateAtoms(synSugarCoords, axis, newChi - STARTING_CHI, atoms["C1'"])
return synSugarCoords
def flipBase(self, curBase):
"""Flip the base anti/syn
ARGUMENTS:
curBase - the current base object in the form [baseType, baseCoordinates]
RETURNS:
the base object with rotated coordinates
NOTE:
This function does not necessarily simply rotate about chi. When flipping a purine, it also adjusts
the glycosidic bond position so that it the base a chance of staying in the density
"""
(baseType, curBaseCoords) = curBase
curC1coords = curBaseCoords["C1'"]
newBaseCoords = {}
#translate the base to the origin
for atomName, curAtomCoords in curBaseCoords.items():
newBaseCoords[atomName] = minus(curBaseCoords[atomName], curC1coords)
#the rotation axis is the same as the alignment vector for mutating the base
#for pyrimidines, the axis is C1'-C4
#for purines, the axis is from C1' to the center of the C4-C5 bond
axis = None
if baseType == "C" or baseType == "U":
axis = newBaseCoords["C4"]
else:
axis = plus(newBaseCoords["C4"], newBaseCoords["C5"])
axis = scalarProd(1.0/2.0, axis)
#rotate the base 180 degrees about the axis
newBaseCoords = rotateAtoms(newBaseCoords, axis, 180, curC1coords)
return [baseType, newBaseCoords]
def mutateBase(self, curBase, newBaseType):
"""Change the base type.
ARGUMENTS:
curBase - the current base object in the form [baseType, baseCoordinates]
newBaseType - the base type to mutate to
RETURNS:
baseObj - a list of [baseType, baseCoordinates]
"""
(curBaseType, curBaseCoords) = curBase
#calculate the vectors used to align the old and new bases
#for pyrimidines, the vector is C1'-C4
#for purines, the vector is from C1' to the center of the C4-C5 bond
curAlignmentVector = None
if curBaseType == "C" or curBaseType == "U":
curAlignmentVector = minus(curBaseCoords["C4"], curBaseCoords["C1'"])
else:
curBaseCenter = plus(curBaseCoords["C4"], curBaseCoords["C5"])
curBaseCenter = scalarProd(1.0/2.0, curBaseCenter)
curAlignmentVector = minus(curBaseCenter, curBaseCoords["C1'"])
#calculate the alignment vector for the new base
newBaseCoords = self.__baseStrucs[newBaseType]
newAlignmentVector = None
if newBaseType == "C" or newBaseType == "U":
newAlignmentVector = newBaseCoords["C4"]
else:
newAlignmentVector = plus(newBaseCoords["C4"], newBaseCoords["C5"])
newAlignmentVector = scalarProd(1.0/2.0, newAlignmentVector)
#calculate the angle between the alignment vectors
rotationAngle = -angle(curAlignmentVector, [0,0,0], newAlignmentVector)
axis = crossProd(curAlignmentVector, newAlignmentVector)
#rotate the new base coordinates
newBaseCoords = rotateAtoms(newBaseCoords, axis, rotationAngle)
#calculate the normals of the base planes
curNormal = None
if curBaseType == "C" or curBaseType == "U":
curNormal = crossProd(minus(curBaseCoords["N3"], curBaseCoords["N1"]), minus(curBaseCoords["C6"], curBaseCoords["N1"]))
else:
curNormal = crossProd(minus(curBaseCoords["N3"], curBaseCoords["N9"]), minus(curBaseCoords["N7"], curBaseCoords["N9"]))
newNormal = None
if newBaseType == "C" or newBaseType == "U":
newNormal = crossProd(minus(newBaseCoords["N3"], newBaseCoords["N1"]), minus(newBaseCoords["C6"], newBaseCoords["N1"]))
else:
newNormal = crossProd(minus(newBaseCoords["N3"], newBaseCoords["N9"]), minus(newBaseCoords["N7"], newBaseCoords["N9"]))
#calculate the angle between the normals
normalAngle = -angle(curNormal, [0,0,0], newNormal);
normalAxis = crossProd(curNormal, newNormal)
#rotate the new base coordinates so that it falls in the same plane as the current base
#and translate the base to the appropriate location
newBaseCoords = rotateAtoms(newBaseCoords, normalAxis, normalAngle, curBaseCoords["C1'"])
return [newBaseType, newBaseCoords]
def findBase(self, mapNum, sugar, phos5, phos3, baseType, direction = 3):
"""Rotate the sugar center by 360 degrees in ROTATE_SUGAR_INTERVAL increments
ARGUMENTS:
mapNum - the molecule number of the Coot map to use
sugar - the coordinates of the C1' atom
phos5 - the coordinates of the 5' phosphate
phos3 - the coordinates of the 3' phosphate
baseType - the base type (A, C, G, or U)
OPTIONAL ARGUMENTS:
direction - which direction are we tracing the chain
if it is 5 (i.e. 3'->5'), then phos5 and phos3 will be flipped
all other values will be ignored
defaults to 3 (i.e. 5'->3')
RETURNS:
baseObj - a list of [baseType, baseCoordinates]
"""
if direction == 5:
(phos5, phos3) = (phos3, phos5)
#calculate the bisector of the phos-sugar-phos angle
#first, calculate a normal to the phos-sugar-phos plane
sugarPhos5Vec = minus(phos5, sugar)
sugarPhos3Vec = minus(phos3, sugar)
normal = crossProd(sugarPhos5Vec, sugarPhos3Vec)
normal = scalarProd(normal, 1.0/magnitude(normal))
phosSugarPhosAngle = angle(phos5, sugar, phos3)
bisector = rotate(sugarPhos5Vec, normal, phosSugarPhosAngle/2.0)
#flip the bisector around (so it points away from the phosphates) and scale its length to 5 A
startingBasePos = scalarProd(bisector, -1/magnitude(bisector))
#rotate the base baton by 10 degree increments about half of a sphere
rotations = [startingBasePos] #a list of coordinates for all of the rotations
for curTheta in range(-90, -1, 10) + range(10, 91, 10):
curRotation = rotate(startingBasePos, normal, curTheta)
rotations.append(curRotation) #here's where the phi=0 rotation is accounted for
for curPhi in range(-90, -1, 10) + range(10, 91, 10):
rotations.append(rotate(curRotation, startingBasePos, curPhi))
#test electron density along all base batons
for curBaton in rotations:
curDensityTotal = 0
densityList = []
for i in range(1, 9):
(x, y, z) = plus(sugar, scalarProd(i/2.0, curBaton))
curPointDensity = density_at_point(mapNum, x, y, z)
curDensityTotal += curPointDensity
densityList.append(curPointDensity)
curBaton.append(curDensityTotal) #the sum of the density (equivalent to the mean for ordering purposes)
curBaton.append(median(densityList)) #the median of the density
curBaton.append(min(densityList)) #the minimum of the density
#find the baton with the max density (as measured using the median)
#Note that we ignore the sum and minimum of the density. Those calculations could be commented out,
# but they may be useful at some point in the future. When we look at higher resolutions maybe?
# Besides, they're fast calculations.)
baseDir = max(rotations, key = lambda x: x[4])
#rotate the stock base+sugar structure to align with the base baton
rotationAngle = angle(self.__baseStrucs["C"]["C4"], [0,0,0], baseDir)
axis = crossProd(self.__baseStrucs["C"]["C4"], baseDir[0:3])
orientedBase = rotateAtoms(self.__baseStrucs["C"], axis, rotationAngle)
#rotate the base about chi to find the best fit to density
bestFitBase = None
maxDensity = -999999
for curAngle in range(0,360,5):
rotatedBase = rotateAtoms(orientedBase, orientedBase["C4"], curAngle, sugar)
curDensity = 0
for curAtom in ["N1", "C2", "N3", "C4", "C5", "C6"]:
curDensity += density_at_point(mapNum, rotatedBase[curAtom][0], rotatedBase[curAtom][1], rotatedBase[curAtom][2])
#this is "pseudoChi" because it uses the 5' phosphate in place of the O4' atom
pseudoChi = torsion(phos5, sugar, rotatedBase["N1"], rotatedBase["N3"])
curDensity *= self.__pseudoChiInterp.interp(pseudoChi)
if curDensity > maxDensity:
maxDensity = curDensity
bestFitBase = rotatedBase
baseObj = ["C", bestFitBase]
#mutate the base to the appropriate type
if baseType != "C":
baseObj = self.mutateBase(baseObj, baseType)
return baseObj
def mutateBase(self, curBase, newBaseType):
"""Change the base type.
ARGUMENTS:
curBase - the current base object in the form [baseType, baseCoordinates]
newBaseType - the base type to mutate to
RETURNS:
baseObj - a list of [baseType, baseCoordinates]
"""
(curBaseType, curBaseCoords) = curBase
#calculate the vectors used to align the old and new bases
#for pyrimidines, the vector is C1'-C4
#for purines, the vector is from C1' to the center of the C4-C5 bond
curAlignmentVector = None
if curBaseType == "C" or curBaseType == "U":
curAlignmentVector = minus(curBaseCoords["C4"], curBaseCoords["C1'"])
else:
curBaseCenter = plus(curBaseCoords["C4"], curBaseCoords["C5"])
curBaseCenter = scalarProd(1.0/2.0, curBaseCenter)
curAlignmentVector = minus(curBaseCenter, curBaseCoords["C1'"])
#calculate the alignment vector for the new base
newBaseCoords = self.__baseStrucs[newBaseType]
newAlignmentVector = None
if newBaseType == "C" or newBaseType == "U":
newAlignmentVector = newBaseCoords["C4"]
else:
newAlignmentVector = plus(newBaseCoords["C4"], newBaseCoords["C5"])
newAlignmentVector = scalarProd(1.0/2.0, newAlignmentVector)
#calculate the angle between the alignment vectors
rotationAngle = -angle(curAlignmentVector, [0,0,0], newAlignmentVector)
axis = crossProd(curAlignmentVector, newAlignmentVector)
#rotate the new base coordinates
newBaseCoords = rotateAtoms(newBaseCoords, axis, rotationAngle)
#calculate the normals of the base planes
curNormal = None
if curBaseType == "C" or curBaseType == "U":
curNormal = crossProd(minus(curBaseCoords["N3"], curBaseCoords["N1"]), minus(curBaseCoords["C6"], curBaseCoords["N1"]))
else:
curNormal = crossProd(minus(curBaseCoords["N3"], curBaseCoords["N9"]), minus(curBaseCoords["N7"], curBaseCoords["N9"]))
newNormal = None
if newBaseType == "C" or newBaseType == "U":
newNormal = crossProd(minus(newBaseCoords["N3"], newBaseCoords["N1"]), minus(newBaseCoords["C6"], newBaseCoords["N1"]))
else:
newNormal = crossProd(minus(newBaseCoords["N3"], newBaseCoords["N9"]), minus(newBaseCoords["N7"], newBaseCoords["N9"]))
#calculate the angle between the normals
normalAngle = -angle(curNormal, [0,0,0], newNormal);
normalAxis = crossProd(curNormal, newNormal)
#rotate the new base coordinates so that it falls in the same plane as the current base
#and translate the base to the appropriate location
newBaseCoords = rotateAtoms(newBaseCoords, normalAxis, normalAngle, curBaseCoords["C1'"])
return [newBaseType, newBaseCoords]
def findBase(self, mapNum, sugar, phos5, phos3, baseType, direction = 3):
"""Rotate the sugar center by 360 degrees in ROTATE_SUGAR_INTERVAL increments
ARGUMENTS:
mapNum - the molecule number of the Coot map to use
sugar - the coordinates of the C1' atom
phos5 - the coordinates of the 5' phosphate
phos3 - the coordinates of the 3' phosphate
baseType - the base type (A, C, G, or U)
OPTIONAL ARGUMENTS:
direction - which direction are we tracing the chain
if it is 5 (i.e. 3'->5'), then phos5 and phos3 will be flipped
all other values will be ignored
defaults to 3 (i.e. 5'->3')
RETURNS:
baseObj - a list of [baseType, baseCoordinates]
"""
if direction == 5:
(phos5, phos3) = (phos3, phos5)
#calculate the bisector of the phos-sugar-phos angle
#first, calculate a normal to the phos-sugar-phos plane
sugarPhos5Vec = minus(phos5, sugar)
sugarPhos3Vec = minus(phos3, sugar)
normal = crossProd(sugarPhos5Vec, sugarPhos3Vec)
normal = scalarProd(normal, 1.0/magnitude(normal))
phosSugarPhosAngle = angle(phos5, sugar, phos3)
bisector = rotate(sugarPhos5Vec, normal, phosSugarPhosAngle/2.0)
#flip the bisector around (so it points away from the phosphates) and scale its length to 5 A
startingBasePos = scalarProd(bisector, -1/magnitude(bisector))
#rotate the base baton by 10 degree increments about half of a sphere
rotations = [startingBasePos] #a list of coordinates for all of the rotations
for curTheta in range(-90, -1, 10) + range(10, 91, 10):
curRotation = rotate(startingBasePos, normal, curTheta)
rotations.append(curRotation) #here's where the phi=0 rotation is accounted for
for curPhi in range(-90, -1, 10) + range(10, 91, 10):
rotations.append(rotate(curRotation, startingBasePos, curPhi))
#test electron density along all base batons
for curBaton in rotations:
curDensityTotal = 0
densityList = []
for i in range(1, 9):
(x, y, z) = plus(sugar, scalarProd(i/2.0, curBaton))
curPointDensity = density_at_point(mapNum, x, y, z)
curDensityTotal += curPointDensity
densityList.append(curPointDensity)
curBaton.append(curDensityTotal) #the sum of the density (equivalent to the mean for ordering purposes)
curBaton.append(median(densityList)) #the median of the density
curBaton.append(min(densityList)) #the minimum of the density
#find the baton with the max density (as measured using the median)
#Note that we ignore the sum and minimum of the density. Those calculations could be commented out,
# but they may be useful at some point in the future. When we look at higher resolutions maybe?
# Besides, they're fast calculations.)
baseDir = max(rotations, key = lambda x: x[4])
#rotate the stock base+sugar structure to align with the base baton
rotationAngle = angle(self.__baseStrucs["C"]["C4"], [0,0,0], baseDir)
axis = crossProd(self.__baseStrucs["C"]["C4"], baseDir[0:3])
orientedBase = rotateAtoms(self.__baseStrucs["C"], axis, rotationAngle)
#rotate the base about chi to find the best fit to density
bestFitBase = None
maxDensity = -999999
for curAngle in range(0,360,5):
rotatedBase = rotateAtoms(orientedBase, orientedBase["C4"], curAngle, sugar)
curDensity = 0
for curAtom in ["N1", "C2", "N3", "C4", "C5", "C6"]:
curDensity += density_at_point(mapNum, rotatedBase[curAtom][0], rotatedBase[curAtom][1], rotatedBase[curAtom][2])
#this is "pseudoChi" because it uses the 5' phosphate in place of the O4' atom
pseudoChi = torsion(phos5, sugar, rotatedBase["N1"], rotatedBase["N3"])
curDensity *= self.__pseudoChiInterp.interp(pseudoChi)
if curDensity > maxDensity:
maxDensity = curDensity
bestFitBase = rotatedBase
baseObj = ["C", bestFitBase]
#mutate the base to the appropriate type
if baseType != "C":
baseObj = self.mutateBase(baseObj, baseType)
return baseObj