def test_masked_superimposition(seed):
"""
Take two models of the same structure and superimpose based on a
single, randomly chosen atom.
Since two atoms can be superimposed perfectly, the distance between
the atom in both models should be 0.
"""
path = join(data_dir, "1l2y.mmtf")
fixed = strucio.load_structure(path, model=1)
mobile = strucio.load_structure(path, model=2)
# Create random mask for a single atom
np.random.seed(seed)
mask = np.full(fixed.array_length(), False)
mask[np.random.randint(fixed.array_length())] = True
# The distance between the atom in both models should not be
# already 0 prior to superimposition
assert struc.distance(fixed[mask], mobile[mask])[0] \
!= pytest.approx(0, abs=5e-4)
fitted, transformation = struc.superimpose(fixed, mobile, mask)
assert struc.distance(fixed[mask], fitted[mask])[0] \
== pytest.approx(0, abs=5e-4)
fitted = struc.superimpose_apply(mobile, transformation)
struc.distance(fixed[mask], fitted[mask])[0] \
== pytest.approx(0, abs=5e-4)
def test_superimposition_array(path):
pdbx_file = pdbx.PDBxFile()
pdbx_file.read(path)
fixed = pdbx.get_structure(pdbx_file, model=1)
mobile = fixed.copy()
mobile = struc.rotate(mobile, (1, 2, 3))
mobile = struc.translate(mobile, (1, 2, 3))
fitted, transformation = struc.superimpose(fixed, mobile,
(mobile.atom_name == "CA"))
assert struc.rmsd(fixed, fitted) == pytest.approx(0)
fitted = struc.superimpose_apply(mobile, transformation)
assert struc.rmsd(fixed, fitted) == pytest.approx(0)
def test_superimposition_array(path):
"""
Take a structure and rotate and translate a copy of it, so that they
are not superimposed anymore.
Then superimpose these structure onto each other and expect an
almost perfect match.
"""
fixed = strucio.load_structure(path, model=1)
mobile = fixed.copy()
mobile = struc.rotate(mobile, (1, 2, 3))
mobile = struc.translate(mobile, (1, 2, 3))
fitted, transformation = struc.superimpose(fixed, mobile)
assert struc.rmsd(fixed, fitted) == pytest.approx(0, abs=6e-4)
fitted = struc.superimpose_apply(mobile, transformation)
assert struc.rmsd(fixed, fitted) == pytest.approx(0, abs=6e-4)
ku_file = biotite.temp_file("ku.cif")
# Download and parse structure files
file = rcsb.fetch("1JEY", "mmtf", biotite.temp_dir())
ku_dna = strucio.load_structure(file)
file = rcsb.fetch("1JEQ", "mmtf", biotite.temp_dir())
ku = strucio.load_structure(file)
# Remove DNA and water
ku_dna = ku_dna[(ku_dna.chain_id == "A") | (ku_dna.chain_id == "B")]
ku_dna = ku_dna[~struc.filter_solvent(ku_dna)]
ku = ku[~struc.filter_solvent(ku)]
# The structures have a differing amount of atoms missing
# at the the start and end of the structure
# -> Find common structure
ku_dna_common = ku_dna[struc.filter_intersection(ku_dna, ku)]
ku_common = ku[struc.filter_intersection(ku, ku_dna)]
# Superimpose
ku_superimposed, transformation = struc.superimpose(
ku_dna_common, ku_common, (ku_common.atom_name == "CA"))
# We do not want the cropped structures
# -> apply superimposition on structures before intersection filtering
ku_superimposed = struc.superimpose_apply(ku, transformation)
# Write PDBx files as input for PyMOL
cif_file = pdbx.PDBxFile()
pdbx.set_structure(cif_file, ku_dna, data_block="ku_dna")
cif_file.write(ku_dna_file)
cif_file = pdbx.PDBxFile()
pdbx.set_structure(cif_file, ku_superimposed, data_block="ku")
cif_file.write(ku_file)
# Visualization with PyMOL...
# biotite_static_image = ku_superimposition.png
def assemble_peptide(sequence):
res_names = [seq.ProteinSequence.convert_letter_1to3(r) for r in sequence]
peptide = struc.AtomArray(length=0)
for res_id, res_name, connect_angle in zip(
np.arange(1,
len(res_names) + 1), res_names,
itertools.cycle([120, -120])):
# Create backbone
atom_n = struc.Atom([0.0, 0.0, 0.0], atom_name="N", element="N")
atom_ca = struc.Atom([0.0, N_CA_LENGTH, 0.0],
atom_name="CA",
element="C")
coord_c = calculate_atom_coord_by_z_rotation(atom_ca.coord,
atom_n.coord, 120,
CA_C_LENGTH)
atom_c = struc.Atom(coord_c, atom_name="C", element="C")
coord_o = calculate_atom_coord_by_z_rotation(atom_c.coord,
atom_ca.coord, 120,
C_O_DOUBLE_LENGTH)
atom_o = struc.Atom(coord_o, atom_name="O", element="O")
coord_h = calculate_atom_coord_by_z_rotation(atom_n.coord,
atom_ca.coord, -120,
N_H_LENGTH)
atom_h = struc.Atom(coord_h, atom_name="H", element="H")
backbone = struc.array([atom_n, atom_ca, atom_c, atom_o, atom_h])
backbone.res_id[:] = res_id
backbone.res_name[:] = res_name
# Add bonds between backbone atoms
bonds = struc.BondList(backbone.array_length())
bonds.add_bond(0, 1, struc.BondType.SINGLE) # N-CA
bonds.add_bond(1, 2, struc.BondType.SINGLE) # CA-C
bonds.add_bond(2, 3, struc.BondType.DOUBLE) # C-O
bonds.add_bond(0, 4, struc.BondType.SINGLE) # N-H
backbone.bonds = bonds
# Get residue from dataset
residue = info.residue(res_name)
# Superimpose backbone of residue
# with backbone created previously
_, transformation = struc.superimpose(
backbone[struc.filter_backbone(backbone)],
residue[struc.filter_backbone(residue)])
residue = struc.superimpose_apply(residue, transformation)
# Remove backbone atoms from residue because they are already
# existing in the backbone created prevoisly
side_chain = residue[~np.isin(
residue.
atom_name, ["N", "CA", "C", "O", "OXT", "H", "H2", "H3", "HXT"])]
# Assemble backbone with side chain (including HA)
# and set annotation arrays
residue = backbone + side_chain
residue.bonds.add_bond(
np.where(residue.atom_name == "CA")[0][0],
np.where(residue.atom_name == "CB")[0][0], struc.BondType.SINGLE)
residue.bonds.add_bond(
np.where(residue.atom_name == "CA")[0][0],
np.where(residue.atom_name == "HA")[0][0], struc.BondType.SINGLE)
residue.chain_id[:] = "A"
residue.res_id[:] = res_id
residue.res_name[:] = res_name
peptide += residue
# Connect current residue to existing residues in the chain
if res_id > 1:
index_prev_ca = np.where((peptide.res_id == res_id - 1)
& (peptide.atom_name == "CA"))[0][0]
index_prev_c = np.where((peptide.res_id == res_id - 1)
& (peptide.atom_name == "C"))[0][0]
index_curr_n = np.where((peptide.res_id == res_id)
& (peptide.atom_name == "N"))[0][0]
index_curr_c = np.where((peptide.res_id == res_id)
& (peptide.atom_name == "C"))[0][0]
curr_residue_mask = peptide.res_id == res_id
# Adjust geometry
curr_coord_n = calculate_atom_coord_by_z_rotation(
peptide.coord[index_prev_c], peptide.coord[index_prev_ca],
connect_angle, C_N_LENGTH)
peptide.coord[curr_residue_mask] -= peptide.coord[index_curr_n]
peptide.coord[curr_residue_mask] += curr_coord_n
# Adjacent residues should show in opposing directions
# -> rotate residues with even residue ID by 180 degrees
if res_id % 2 == 0:
coord_n = peptide.coord[index_curr_n]
coord_c = peptide.coord[index_curr_c]
peptide.coord[curr_residue_mask] = struc.rotate_about_axis(
atoms=peptide.coord[curr_residue_mask],
axis=coord_c - coord_n,
angle=np.deg2rad(180),
support=coord_n)
# Add bond between previous C and current N
peptide.bonds.add_bond(index_prev_c, index_curr_n,
struc.BondType.SINGLE)
# Add N-terminal hydrogen
atom_n = peptide[(peptide.res_id == 1) & (peptide.atom_name == "N")][0]
atom_h = peptide[(peptide.res_id == 1) & (peptide.atom_name == "H")][0]
coord_h2 = calculate_atom_coord_by_z_rotation(atom_n.coord, atom_h.coord,
-120, N_H_LENGTH)
atom_h2 = struc.Atom(coord_h2,
chain_id="A",
res_id=1,
res_name=atom_h.res_name,
atom_name="H2",
element="H")
peptide = struc.array([atom_h2]) + peptide
peptide.bonds.add_bond(0, 1, struc.BondType.SINGLE) # H2-N
# Add C-terminal hydroxyl group
last_id = len(sequence)
index_c = np.where((peptide.res_id == last_id)
& (peptide.atom_name == "C"))[0][0]
index_o = np.where((peptide.res_id == last_id)
& (peptide.atom_name == "O"))[0][0]
coord_oxt = calculate_atom_coord_by_z_rotation(peptide.coord[index_c],
peptide.coord[index_o],
connect_angle, C_O_LENGTH)
coord_hxt = calculate_atom_coord_by_z_rotation(coord_oxt,
peptide.coord[index_c],
connect_angle, O_H_LENGTH)
atom_oxt = struc.Atom(coord_oxt,
chain_id="A",
res_id=last_id,
res_name=peptide[index_c].res_name,
atom_name="OXT",
element="O")
atom_hxt = struc.Atom(coord_hxt,
chain_id="A",
res_id=last_id,
res_name=peptide[index_c].res_name,
atom_name="HXT",
element="H")
peptide = peptide + struc.array([atom_oxt, atom_hxt])
peptide.bonds.add_bond(index_c, -2, struc.BondType.SINGLE) # C-OXT
peptide.bonds.add_bond(-2, -1, struc.BondType.SINGLE) # OXT-HXT
return peptide