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- import math
- import numpy as np
-
- class Structure:
- def __init__(self, res):
- self.res = res
-
- class Turn(Structure):
-
- def __init__(self, turn_type, res):
- self.turn_type = turn_type
- Structure.res = res
-
- class Bridge(Structure):
-
- def __init__(self, bridge_type, res_num):
- self.bridge_type = bridge_type
- self.res_num = res_num
- Structure.res = res_num
-
- class Helix(Structure):
-
- def __init__(self, residues, res_num):
- self.residues = residues
- self.res_num = res_num
- Structure.res = res_num
-
- def get_turns(residues):
- turns = {}
- for i,res in enumerate(residues):
- for j in range(3,6):
- if(i+j<len(residues)):
- if(res.h_bond(residues[i+j])<-0.5):
- print(j,"TURN", residues[i].resid, residues[i+j].resid)
- turns[residues[i].resid] = Turn(j,residues[i].resid)
- return(turns)
-
- def get_bridges(residues):
- bridges = []
- bridge = {}
- strongest_bridge = {}
- for i in range(1,len(residues)-4):
- E_min = 0
- for j in range(i+2,len(residues)-1):
- # select triplet with the minimal energy
-
- if(residues[i-1].h_bond(residues[j])<-0.5
- and residues[j].h_bond(residues[i+1])<-0.5):
- bridge = {'res1':residues[i-1].h_bond(residues[j]),
- 'res2':residues[j].h_bond(residues[i+1]),
- 'ipos':residues[i].resid,
- 'jpos':residues[j].resid,
- 'btype':"para"}
- # if(residues[i-1].h_bond(residues[j])+
- # residues[j].h_bond(residues[i+1]))<E_min:
- # E_min = residues[i-1].h_bond(residues[j])
- # +residues[j].h_bond(residues[i+1])
- # bridge_type = "para"
-
- if(residues[j-1].h_bond(residues[i])<-0.5
- and residues[i].h_bond(residues[j+1])<-0.5):
- bridge = {'res1':residues[j-1].h_bond(residues[i]),
- 'res2':residues[i].h_bond(residues[j+1]),
- 'ipos':residues[i].resid,
- 'jpos':residues[j].resid,
- 'btype':"para"}
- # if(residues[j-1].h_bond(residues[i])+
- # residues[i].h_bond(residues[j+1]))<E_min:
- # E_min = residues[j-1].h_bond(residues[i])
- # +residues[i].h_bond(residues[j+1])
- # bridge_type = "para"
-
- if(residues[i].h_bond(residues[j])<-0.5
- and residues[j].h_bond(residues[i])<-0.5):
- bridge = {'res1':residues[i].h_bond(residues[j]),
- 'res2':residues[j].h_bond(residues[i]),
- 'ipos':residues[i].resid,
- 'jpos':residues[j].resid,
- 'btype':"anti"}
- # if(residues[i].h_bond(residues[j])+
- # residues[j].h_bond(residues[i]))<E_min:
- # E_min = residues[i].h_bond(residues[j])
- # +residues[j].h_bond(residues[i])
- # bridge_type = "anti"
-
- if(residues[i-1].h_bond(residues[j+1])<-0.5
- and residues[j-1].h_bond(residues[i+1])<-0.5):
- bridge = {'res1':residues[i-1].h_bond(residues[j+1]),
- 'res2':residues[j-1].h_bond(residues[i+1]),
- 'ipos':residues[i].resid,
- 'jpos':residues[j].resid,
- 'btype':"anti"}
- # if(residues[i-1].h_bond(residues[j+1])+
- # residues[j-1].h_bond(residues[i+1]))<E_min:
- # E_min = residues[i-1].h_bond(residues[j+1])
- # +residues[j-1].h_bond(residues[i+1])
- # bridge_type = "anti"
- if(bridge):
- if(bridge['res1']+bridge['res2']<E_min):
- E_min = bridge['res1']+bridge['res2']
- strongest_bridge = bridge
- bridge = {}
- # finally add the strongest bridge at i and j pos
- if(strongest_bridge):
- bridges.append(Bridge(strongest_bridge['btype'],
- strongest_bridge['ipos']))
- bridges.append(Bridge(strongest_bridge['btype'],
- strongest_bridge['jpos']))
- if(len(bridges)>0):
- return(bridges)
- else:
- return(False)
-
- def get_helix(residues, turns):
- i = 1
- helix = []
- while i <= len(residues):
- if(i in turns.keys() and i-1 in turns.keys()):
- k = 0
- temp_res = []
- while(i+k in turns):
- k+=1
- temp_res.append(residues[i])
- if(k>2):
- print(k,"- HELIX at", residues[i].resid)
- helix.append(Helix(temp_res,residues[i].resid))
- i = i+k
- else:
- i+=1
- return(helix)
-
- def get_ladder(bridges):
- ladders = {}
- for i in range(len(bridges)):
- k = 1
- while bridges[i] == bridges[i+k]:
- k+=1
- if k>1:
- ladders[bridges[i].res_num] = k-1
-
- def get_bends(residues):
- bends = {}
- for i in range(2,len(residues)-2):
- angle = vector_angles(vectors_substr(position_vector(residues[i].atoms["CA"].coords),
- position_vector(residues[i-2].atoms["CA"].coords)),
- vectors_substr(position_vector(residues[i+2].atoms["CA"].coords),
- position_vector(residues[i].atoms["CA"].coords)))
- if(angle>70):
- print("angle", residues[i].resid, angle)
- bends[residues[i].resid] = angle
- return(bends)
-
- def vector_from_pos(a, b):
- xAB = b[0]-a[0]
- yAB = b[1]-a[1]
- zAB = b[2]-a[2]
- coord_AB = [xAB,yAB,zAB]
- return coord_AB
-
- def vector_norm(v):
- norm = math.sqrt(v[0]**2 + v[1]**2 + v[2]**2)
- return norm
-
- def dot_product(v1,v2):
- dot_product = v1[0]*v2[0] + v1[1]*v2[1] + v1[2]*v2[2]
- return(dot_product)
-
- def position_vector(c):
- vector = vector_from_pos([0,0,0],c)
- return vector
-
- def vectors_substr(v1, v2):
- return ([v1[0]-v2[0],
- v1[1]-v2[1],
- v1[2]-v2[2]])
-
- def vector_angles(v1,v2):
- dot_prod = dot_product(v1,v2)
- norm_v1 = vector_norm(v1)
- norm_v2 = vector_norm(v2)
- term = dot_prod/(abs(norm_v1)*abs(norm_v2))
- rad_angle = math.acos(term)
- deg_angle = rad_angle*(180/math.pi)
- return deg_angle
-
- def calc_dihedral(u1, u2, u3, u4):
- """ Calculate dihedral angle method. From bioPython.PDB
- (adapted to np.array)
- Calculate the dihedral angle between 4 vectors
- representing 4 connected points. The angle is in
- [-pi, pi].
-
- Adapted function of dihedral_angle_from_coordinates.py
- by Eric Alcaide.
- Source : https://gist.github.com/EricAlcaide
- URL : https://gist.github.com/EricAlcaide/30d6bfdb8358d3a57d010c9a501fda56
- """
- #convert coords to numpy arrays
- u1 = np.array(u1)
- u2 = np.array(u2)
- u3 = np.array(u3)
- u4 = np.array(u4)
-
- a1 = u2 - u1
- a2 = u3 - u2
- a3 = u4 - u3
-
- v1 = np.cross(a1, a2)
- v1 = v1 / (v1 * v1).sum(-1)**0.5
- v2 = np.cross(a2, a3)
- v2 = v2 / (v2 * v2).sum(-1)**0.5
- porm = np.sign((v1 * a3).sum(-1))
- rad = np.arccos((v1*v2).sum(-1) / ((v1**2).sum(-1) * (v2**2).sum(-1))**0.5)
- if not porm == 0:
- rad = rad * porm
-
- deg_angle = rad*(180/math.pi)
- return deg_angle
-
-
- def get_chirality(residues):
-
- for i in range(1,len(residues)-2):
- chirality = {}
- angle = calc_dihedral(residues[i-1].atoms["CA"].coords,
- residues[i].atoms["CA"].coords,
- residues[i+1].atoms["CA"].coords,
- residues[i+2].atoms["CA"].coords)
-
- if(angle>0 and angle<=180):
- sign="+"
- print("angle", residues[i].resid, "+", angle)
-
- if(angle<=0 and angle > -180):
- sign="-"
- print("angle", residues[i].resid, "-", angle)
-
- chirality[residues[i].resid] = sign
-
- return chirality
-
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