The Molecular Entity¶

The Handle Classes¶

CreateEntity()¶

Creates a new entity. The created entity is empty, that is, it does not contain any atoms, residues, chains, bonds or torsions. To populate the entity, use an entity editor.

Returns:	The newly created EntityHandle

class EntityHandle¶

The entity class represents a molecular structure. Such a structure is in general made up of one or more chains of residues, which in turn are formed by one or more atoms.

The interface of entities is tailored to biological macromolecules, but this does not prevent it to be used for molecules in general: An entity also represent a ligand or a collection of water molecules - hence the rather generic name.

chains¶

List of all chains of this entity. The chains are in the same order they have been added, for example the order they have been listed in a PDB file.

Also available as GetChainList(). To access a single chain, use FindChain().

This property is read-only.

Type:	ChainHandleList (list of ChainHandle)

chain_count¶

Number of chains. Read-only. See GetChainCount().

Type:	int

residues¶

List of all residues of this entity. The returned residues are first sorted by chain and then from N- to C-terminus.

This property is read-only.

Example usage:

for res in ent.residues:
  print(res.name, res.atom_count)

Also available as GetResidueList(). To access a single residue, use FindResidue().

Type:	ResidueHandleList (list of ResidueHandle)

residue_count¶

Number of residues. Read-only. See GetResidueCount().

Type:	int

atoms¶

Get list of all atoms of this entity. To access a single atom, use FindAtom().

This property is read-only. Also available as GetAtomList()

Type:	AtomHandleList (list of AtomHandle)

atom_count¶

Number of atoms. Read-only. See GetAtomCount().

Type:	int

bounds¶

Axis-aligned bounding box of the entity. Read-only

Type:	ost.geom.AlignedCuboid

mass¶

The total mass of the entity in Dalton. Also available as GetMass().

Type:	float

center_of_mass¶

Center of mass. Also available as GetCenterOfMass()

Type:	Vec3

center_of_atoms¶

Center of atoms (not mass-weighted). Also available as GetCenterOfAtoms().

Type:	Vec3

positions¶

Equivalent to calling GetPositions() with sort_by_index = True. This property is read-only and only available if OpenStructure was compiled with an enabled USE_NUMPY flag (see here for details).

Type:	numpy.array

valid¶

Validity of handle.

Type:	bool

GetName()¶

Returns:	Name associated to this entity.
Return type:	str

SetName(name)¶

Parameters:	name (str) – Sets this as new name to be associated to this entity.

FindChain(chain_name)¶

Get chain by name. See also chains

Parameters:	chain_name (str) – Chain identifier, e.g. “A”
Returns:	A valid ChainHandle, if the entity contains a chain with the given name, an invalid ChainHandle otherwise.

GetChainList()¶

See chains

GetChainCount()¶

See chain_count

FindResidue(chain_name, res_num)¶

Get residue by chain name and residue number. See also GetResidueList()

Parameters:	chain_name (str) – Chain identifier, e.g. “A” res_num (ResNum) – residue number
Returns:	A valid ResidueHandle if the chain exists and the chain contains a residue of the given residue number, an invalid ResidueHandle otherwise.

GetResidueList()¶

See residues

GetResidueCount()¶

See residue_count

FindAtom(chain_name, res_num, atom_name)¶

Get atom by chain name, residue number and atom name. See also atoms

Parameters:	chain_name (str) – Chain identifier, e.g. “A” res_num (ResNum) – residue number atom_name (str) – atom name, e.g. CA
Returns:	A valid AtomHandle if an atom matching the parameters could be found, an invalid AtomHandle otherwise

GetAtomList()¶

See atoms

GetAtomCount()¶

See atom_count

EditXCS([edit_mode=mol.EditMode.UNBUFFERED_EDIT])¶

Request XCSEditor for editing the external coordinate system. This call will fail when there are pending changes of the internal coordinate system.

Parameters:	edit_mode (mol.EditMode) – Must be EditMode.BUFFERED_EDIT or EditMode.UNBUFFERED_EDIT. For more details, see the editor documentation.
Returns:	XCSEditor

EditICS([edit_mode=mol.EditMode.UNBUFFERED_EDIT])¶

Request ICSEditor for editing the internal coordinate system, such as torsions, bond lengths and angle between two bonds. This call will fail when there are pending changes of the external coordinate system.

Parameters:	edit_mode (mol.EditMode) – Must be EditMode.BUFFERED_EDIT or EditMode.UNBUFFERED_EDIT. For more details, see the editor documentation.
Returns:	ICSEditor

Select(query, flags=0)¶

Perform a selection on the entity. The result of the selection is an EntityView which (usually) contains only a subset of chains, residues, atoms and bonds of the original entity.

Example Usage:

# select calpha atoms of peptides
calphas = ent.Select('aname=CA and peptide=true')

# select atoms in a box of size 10, centred at the origin
in_box = ent.Select('x=-5:5 and y=-5:5 and z=-5:5')

Parameters:	query (Query / str) – The query to be executed. flags (int / QueryFlag) – An ORed together combination of QueryFlag
Returns:	An entity view.
Raises:	QueryError when the query could not be executed due to syntactic errors.

CreateFullView()¶

Creates an entity view containing all chains, residues, atoms and bonds of this entity.

# these two lines are identical
full=ent.Select('')
full=ent.CreateFullView()

Returns:	EntityView

CreateEmptyView()¶

Creates an entity view pointing to this entity, but otherwise empty. This method is usually the starting point for manual entity view creation, e.g.:

view=ent.CreateEmtpyView()
for atom in ent.atoms:
  if ComplicatedPredicate(atom):
     view.AddAtom(atom)

Returns:	EntityView

Copy()¶

Creates a deep copy of the entity.

Returns:	A new EntityHandle that is an exact copy of this entity.

Note

alternative atom positions are not handled yet.

GetCenterOfAtoms()¶

Get center of atoms, that is the average atom position of the entity. Use GetCenterOfMass() to calculate the mass-weighted center of the entity.

Returns:	Vec3

GetCenterOfMass()¶

Calculates the center of mass of the entity. Use GetCenterOfAtoms() to calculate the non-mass-weighted center of the entity.

Returns:	Vec3

GetGeometricCenter()¶

Calculates the mid-point of the axis aligned bounding box of the entity.

Returns:	Vec3

GetMass()¶

See mass

GetPositions(sort_by_index=True)¶

Returns:	Array of atom positions for this entity.
Return type:	numpy.array (shape [atom_count, 3])
Parameters:	sort_by_index – If True, the atoms are sorted by their index. Otherwise, they are sorted as they appear in the atoms list.

This method is only available if OpenStructure was compiled with an enabled USE_NUMPY flag (see here for details).

FindWithin(pos, radius)¶

Find all atoms in sphere of given radius centred at pos. To turn the returned list of atoms into an EntityView, use CreateViewFromAtomList().

Parameters:	pos (Vec3) – Center of sphere radius (float) – The radius of the sphere
Returns:	AtomHandleList (list of AtomHandle)

IsValid()¶

See valid

class ChainHandle¶

A chain of one or more residues. Chains are always part of an entity.

name¶

The chain name. The name uniquely identifies the chain in the entity. In most cases, the chain name is one character. This is restriction of the PDB file format. However, you are free to use longer names as long as you don’t want to save them as PDB files

This property is read-only. To change the name, use an XCSEditor.

Also available as GetName()

Type:	str

type¶

Describes the type of the chain.

Type:	ChainType.

description¶

Details about the chain. Not categorised, just text.

residues¶

List of all residues of this chain. The residues are sorted from N- to C-terminus. Usually the residue numbers are in ascending order (see in_sequence).

This property is read-only.

Example usage:

chain=ent.FindChain("A")
for res in chain.residues:
  print(res.name, res.atom_count)

Also available as GetResidueList(). To access a single residue, use FindResidue().

Type:	ResidueHandleList (list of ResidueHandle)

in_sequence¶

Whether the residue numbers are in ascending order. For example:

chain=ent.FindChain("A")
print(chain.residues) # [A.GLY1, A.GLY2, A.GLY4A, A.GLY4B]
print(chain.in_sequence) # prints true

chain=ent.FindChain("B")
print(chain.residues) # [B.GLY1, B.GLY4, B.GLY3]
print(chain.in_sequence) # prints false

residue_count¶

Number of residues. Read-only. See GetResidueCount().

Type:	int

atoms¶

Get list of all atoms of this chain. To access a single atom, use FindAtom().

This property is read-only. Also available as GetAtomList()

Type:	AtomHandleList (list of AtomHandle)

bounds¶

Axis-aligned bounding box of the chain. Read-only

Type:	ost.geom.AlignedCuboid

mass¶

The total mass of this chain in Dalton. Also available as GetMass()

Type:	float

center_of_mass¶

Center of mass. Also available as GetCenterOfMass()

Type:	Vec3

center_of_atoms¶

Center of atoms (not mass weighted). Also available as GetCenterOfAtoms().

Type:	Vec3

valid¶

Validity of handle.

Type:	bool

FindResidue(res_num)¶

Get residue by residue number. See also residues.

Parameters:	res_num (ResNum) – residue number
Returns:	A valid ResidueHandle if the chain contains a residue with matching residue number, an invalid ResidueHandle otherwise.

GetResidueList()¶

See residues

GetResidueCount()¶

See residue_count

FindAtom(res_num, atom_name)¶

Get atom by residue number and atom name. See also atoms

Parameters:	res_num (ResNum) – residue number atom_name (str) – atom name, e.g. CA
Returns:	A valid AtomHandle if an atom matching the parameters could be found, an invalid AtomHandle otherwise

GetAtomList()¶

See atoms

GetName()¶

See name

GetType()¶

See type

GetDescription()¶

See description

IsValid()¶

See valid

class ResidueHandle¶

The residue is either used to represent complete molecules or building blocks in a polymer, e.g. in a protein, DNA or RNA. A residue consists of one or more atoms. Residues are always part of a ChainHandle, even if they are ligands or water molecules where the concept of a chain does not apply.

name¶

The residue name is usually a str of 3 characters, e.g. GLY for glycine or ALA for alanine, but may be shorter, e.g. G for guanosine, or longer for structures loaded from formats other than PDB.

This property is read-only. To change the name of the residue, use EditorBase.SetResidueName().

number¶

The number of this residue. The residue number has a numeric part and an insertion-code. This property is read-only. Also available as GetNumber().

Type:	ResNum

one_letter_code¶

For amino acids, and nucleotides the one_letter_code is an alpha-numeric character. For unknown or more exotic residues, the one letter code is set to ‘?’.

Example

This code-snippet shows how to get the sequence string from a list of residues.

print(''.join([r.one_letter_code for r in chain.residues]))

Type:	str

atoms¶

Get list of all atoms of this residue. To access a single atom, use FindAtom().

This property is read-only. Also available as GetAtomList()

Type:	AtomHandleList (list of AtomHandle)

bounds¶

Axis-aligned bounding box of the residue. Read-only.

Type:	ost.geom.AlignedCuboid

mass¶

The total mass of this residue in Dalton. Also available as GetMass().

Type:	float

center_of_mass¶

Center of mass. Also available as GetCenterOfMass()

Type:	Vec3

center_of_atoms¶

Center of atoms (not mass weighted). Also available as GetCenterOfAtoms().

Type:	Vec3

chain¶

The chain this residue belongs to. Read-only. Also available as GetChain()

Type:	ChainHandle

phi_torsion¶

The PHI dihedral angle between this residue and the next. For residues that are not amino acids, residues that do not have all atoms required or residues that do not have bonds between the four atoms involved in the torsion, the PHI torsion is an invalid handle.

Read-only. Also available as GetPhiTorsion()

Type:	TorsionHandle

psi_torsion¶

The PSI dihedral angle between this residue and the previous. For residues that are not amino acids, residues that do not have all atoms required or residues that do not have bonds between the four atoms involved in the torsion, the PSI torsion is an invalid handle.

Read-only. Also available as GetPsiTorsion()

Type:	TorsionHandle

chem_class¶

The chemical class of the residue.

Type:	ChemClass

chem_type¶

The chemical type of the residue. The type is only properly set if a compound library is used.

Type:	ChemType

sec_structure¶

The secondary structure of the residue.

Type:	SecStructure

is_ligand¶

Whether the residue is a ligand. When loading PDB structures, this property is set based on the HET records. This also means, that this property will most likely not be set properly for all except PDB files coming from pdb.org. Also available as IsLigand(), SetIsLigand().

is_protein¶

Whether the residue is considered to be part of a protein. This is set when loading a structure if the residue forms a feasible peptide bond to the previous or next residue (see IsBondFeasible()). Also available as IsProtein(), SetIsProtein(). In contrast to IsPeptideLinking() this excludes residues which are not connected to neighbouring residues such as CA-only residues or badly positioned ones.

peptide_linking¶

Whether residue can form peptide bonds. This is determined based on chem_class which is set when loading the structure.

Type:	bool

index¶

Residue index (starting at 0) within chain.

central_atom¶

Central atom used for rendering traces. For peptides, this is usually the CA atom. For nucleotides, this is usually the P atom.

Type:	AtomHandle

central_normal¶

Normal computed for central_atom. Only defined for peptides and nucleotides if all required atoms available. Otherwise, the (1,0,0) vector is returned.

Type:	Vec3

valid¶

Validity of handle.

Type:	bool

next¶

Residue after this one in the same chain. Invalid handle returned if there is no next residue. Residues are ordered as in ChainHandle.residues independently on whether they are connected or not (see InSequence() to check for connected residues).

Type:	ResidueHandle

prev¶

Residue before this one in the same chain. Otherwise same behaviour as next.

Type:	ResidueHandle

FindAtom(atom_name)¶

Get atom by atom name. See also atoms

Parameters:	atom_name (str) – atom name, e.g. CA
Returns:	A valid AtomHandle if an atom with the given name could be found, an invalid AtomHandle otherwise

HasAltAtoms()¶

Returns whether the residue has any alternative atom groups

Return type:	bool

HasAltAtomGroup(group_name)¶

Returns whether the residue has a certain alternative atom group

Parameters:	group_name (str) – Group of interest
Return type:	bool

GetAltAtomGroupNames()¶

Returns names of all alternative atom groups in residue

Return type:	list of str

GetCurrentAltGroupName()¶

Returns the currently active alternative atom group, empty str if residue has no alternative atom groups

Return type:	str

SwitchAtomPos(group_name)¶

Switches the atoms in residue to the specified alternative atom group

Parameters:	group_name (str) – Group of interest
Return type:	bool
Returns:	Whether the switch was successful (e.g. False if no such group exists)

GetAtomList()¶

See atoms

IsPeptideLinking()¶

See peptide_linking

GetChain()¶

See chain

GetCenterOfAtoms()¶

See center_of_atoms

GetCenterOfMass()¶

See center_of_mass

GetPhiTorsion()¶

See phi_torsion

GetPsiTorsion()¶

See psi_torsion

GetChemType()¶

See chem_type

GetIndex()¶

See index

GetCentralAtom()¶

SetCentralAtom()¶

See central_atom

GetCentralNormal()¶

See central_normal

IsValid()¶

See valid

class AtomHandle¶

Represents an atom in a molecular structure. Atoms are always part of a residue.

name¶

The atom name, usually a capitalized string consisting of the element and an position indicator, e.g. G1. In general, the atom name uniquely identifies an atom within a residue. However, this is not enforced and there may be more than one atoms with the same name.

Type:	str

qualified_name¶

The qualified name consists of the atom name as well as a unique residue identifier and chain name. For CA of a glycine with residue number 2 of chain A, the qualified name is “A.GLY2.CA”.

Type:	str

element¶

The atom’s element. Note that this may return an empty string. Also available as GetElement(). Read-only.

Type:	str

mass¶

The atom’s mass in Dalton. Also available as GetMass(). Read-only.

Type:	float

pos¶

The atom’s position in global coordinates, transformed by the entity transformation. Also available as GetPos().

Read-only.

Type:	Vec3

original_pos¶

The atom’s untransformed position in global coordinates. Also available as GetOriginalPos().

Read-only.

Type:	Vec3

radius¶

The van-der-Waals radius of the atom. Also available as GetRadius(). Read/write.

Type:	float

occupancy¶

The atom’s occupancy in the range 0 to 1. Read/write. Also available as GetOccupancy(), SetOccupancy().

Type:	float

b_factor¶

The atom’s temperature factor. Read/write. Also available as GetBFactor(), SetBFactor().

Type:	float

charge¶

The atom’s charge. Also available as GetCharge(), SetCharge().

Type:	float

residue¶

The residue this atom belongs to. Read-only.

Type:	ResidueHandle

is_hetatom¶

Indicates whether this atom is a HETATM. When loading a structure from a PDB file, all non-standard aminoacid and nucleotide atoms as well as ligands are marked as HETATM.

bonds¶

List of bonds this atom is involved in. The bonds are in no particular order. Also available as GetBondList().

Type:	list of bond handles

index¶

Atom index (starting at 0) within entity.

Type:	int

hash_code¶

A unique identifier for this atom. Note that a deep copy of an entity (see EntityHandle.Copy()) will have atoms with differing identifiers. Shallow copies of the entity preserve the identifier. Atom views on a handle have different identifiers, but the atom view handles (see AtomView.handle) have the same identifier.

Type:	int

valid¶

Validity of handle.

Type:	bool

FindBondToAtom(other_atom)¶

Finds and returns the bond formed between this atom and other_atom. If no bond exists between the two atoms, an invalid BondHandle is returned.

Parameters:	other_atom (AtomHandle) – The other atom
Return type:	BondHandle

GetBondCount()¶

Return type:	int

GetBondList()¶

See bonds

Return type:	BondHandleList

GetBondPartners()¶

Get list of atoms this atom is bonded with. This method exists as a shortcut to determine all the bonding partners of an atom and avoids code like this:

bond_parters=[]
for bond in atom.bonds:
  if bond.first==atom:
    bond_partners.append(bond.second)
  else:
    bond_partners.append(bond.first)

Return type:	AtomHandleList

GetCharge()¶

See charge

Return type:	float

GetElement()¶

See element

Return type:	str

GetEntity()¶

The entity this atom belongs to

Return type:	EntityHandle

GetHashCode()¶

See hash_code

Return type:	int

GetIndex()¶

See index

Return type:	int

GetMass()¶

See mass

Return type:	float

GetName()¶

See name

Return type:	str

GetOriginalPos()¶

Return type:	Vec3

GetPos()¶

See pos

Return type:	Vec3

GetQualifiedName()¶

See qualified_name

Return type:	str

GetRadius()¶

See radius

Return type:	float

GetResidue()¶

See residue

Return type:	ResidueHandle

IsHetAtom()¶

See is_hetatom

Return type:	bool

IsValid()¶

See valid

The View Classes¶

class EntityView¶

An entity view represents a structural subset of an EntityHandle. For an introduction ,see Introduction to the mol Module.

chains¶

List of all chains of this entity. The chains are in the same order they have been added.

Also available as GetChainList(). To access a single chain, use FindChain().

This property is read-only.

Type:	ChainViewList (list of ChainView)

chain_count¶

Number of chains. Read-only. See GetChainCount().

Type:	int

residues¶

List of all residues of this entity. The returned residues are first sorted by chain and then from N- to C-terminus.

This property is read-only.

Example usage:

for res in ent.residues:
  print(res.name, res.atom_count)

Also available as GetResidueList(). To access a single residue, use FindResidue().

Type:	ResidueViewList (list of ResidueView)

residue_count¶

Number of residues. Read-only. See GetResidueCount().

Type:	int

atoms¶

Get list of all atoms of this entity. To access a single atom, use FindAtom().

This property is read-only. Also available as GetAtomList()

Type:	AtomViewList (list of AtomView)

atom_count¶

Number of atoms. Read-only. See GetAtomCount().

Type:	int

bounds¶

Axis-aligned bounding box of the entity view. Read-only.

Type:	ost.geom.AlignedCuboid

handle¶

The underlying handle of the entity view. Also available as GetHandle().

Type:	EntityHandle

valid¶

Validity of view.

Type:	bool

GetName()¶

Returns:	GetName() of entity handle.
Return type:	str

SetName(name)¶

Parameters:	name (str) – Passed to SetName() of handle.

CreateEmptyView()¶

See EntityHandle.CreateEmptyView()

Return type:	EntityView

CreateFullView()¶

Returns a copy of this entity. Provided for duck-typing <http://en.wikipedia.org/wiki/Duck_typing> purposes.

Return type:	EntityView

AddChain(chain_handle[, view_add_flags])¶

Add chain to view. By default, only the chain is added to the view, but not its residues and atoms. This behaviour can be changed by passing in an appropriate set of view_add_flags.

The following example just adds a chain without residues and atoms:

pdb = ost.io.LoadPDB(<PDB file name>)
v = pdb.CreateEmptyView()
v.AddChain(pdb.chains[0])

To get the chain with residues and atoms, go like:

pdb = ost.io.LoadPDB(<PDB file name>)
v = pdb.CreateEmptyView()
v.AddChain(pdb.chains[0], ost.mol.INCLUDE_ALL)

Note that the view above still lacks bonds which can be added with the AddAllInclusiveBonds() method.

Parameters:	chain_handle (ChainHandle) – The chain handle to be added. view_add_flags (int / ViewAddFlag) – An ORed together combination of ViewAddFlag
Return type:	ChainView

AddResidue(residue_handle[, view_add_flags])¶

Add residue to view. If the residue’s chain is not already part of the view, it will be added. By default, only the residue is added, but not its atoms. This behaviour can be modified by passing in an appropriate combination of ViewAddFlag.

Parameters:	residue_handle (ResidueHandle) – The residue handle to be added view_add_flags (int / ViewAddFlag) – An ORed together combination of ViewAddFlag
Return type:	ResidueView

AddAtom(atom_handle[, view_add_flags])¶

Add the atom to view. The chain and residue of the atom are added to the view if they haven’t already been added.

Parameters:	atom_handle (AtomHandle) – The atom handle view_add_flags (int / ViewAddFlag) – An ORed together combination of ViewAddFlag
Return type:	AtomView

AddBond(bond_handle)¶

Add bond to the view.

Parameters:	bond_handle (BondHandle) – Bond to be added
Returns:	True if the bond has been added, false if the bond was already present in the view.
Return type:	bool

AddAllInclusiveBonds()¶

Convenience method to add all bonds to the view for which both of the bond partners are in the view. This method is useful when manually assembling views.

RemoveChain(chain)¶

Remove chain and all its residues from the entity view.

Parameters:	chain (ChainView) – The chain to be removed. May be invalid

RemoveResidue(residue)¶

Remove residue from view.

Parameters:	residue (ResidueView) – The residue to be removed. May be invalid

RemoveAtom(atom)¶

Remove atom from view

Parameters:	atom (AtomView) – The atom to be removed. May be invalid

GetAngle(atom1, atom2, atom3)¶

Parameters:	atom1 (AtomHandle) – atom2 (AtomHandle) – atom3 (AtomHandle) –
Return type:	float

FindWithin(pos, radius)¶

Find all atoms that are within radius of the given position. See EntityHandle.FindWithin().

Parameters:	pos (Vec3) – Center of sphere radius (float) – The radius of the sphere
Returns:	AtomHandleList (list of AtomHandle)

FindChain(chain_name)¶

Find chain by name.

Parameters:	chain_name (str) – Chain identifier, e.g. “A”
Returns:	The chain if present in the view, an invalid ChainView otherwise
Return type:	ChainView

FindResidue(residue)¶

Find residue view of pointing to the given handle.

Parameters:	residue (ResidueHandle) – Residue handle
Returns:	The residue view pointing the the handle, or an invalid handle if the residue is not part of the view
Return type:	ResidueView

FindAtom(chain_name, res_num, atom_name)¶

Parameters:	chain_name (str) – The chain name res_num (ResNum or int) – The residue number atom_name (str) – The name of the atom
Return type:	AtomView

Select(query, flags=0)¶

Perform selection on entity view. See EntityHandle.Select().

Parameters:	query (Query / str) – The query flags (int / QueryFlag) – An ORed together combination of QueryFlag
Return type:	EntityView

Copy()¶

Returns a deep copy of the entity view. The effect is identical to calling

the_copy=view.Select(')

Return type:	EntityView

GetMass()¶

Get total mass of view.

Return type:	float

GetCenterOfMass()¶

Get the center of mass. For a non-mass-weighted center, see GetCenterOfAtoms().

Return type:	Vec3

GetGeometricCenter()¶

Get the geometric center (the center of the axis-aligned bounding box).

Return type:	Vec3

GetGeometricStart()¶

Return type:	Vec3

GetCenterOfAtoms()¶

Calculates the center of atoms. For a mass-weighted center, use GetCenterOfMass().

Return type:	Vec3

GetBondCount()¶

Get number of bonds

Return type:	int

GetBondList()¶

See bonds

Return type:	BondHandleList

GetHandle()¶

See handle

Return type:	EntityHandle

GetGeometricEnd()¶

Return type:	Vec3

GetChainList()¶

See chains

GetChainCount()¶

See chain_count

GetResidueList()¶

See residues

GetResidueCount()¶

See residue_count

GetAtomList()¶

See atoms

GetAtomCount()¶

See atom_count

IsValid()¶

See valid

class ChainView¶

A view representation of a ChainHandle. Mostly, the same functionality is provided as for the handle.

name¶

The chain name. The name uniquely identifies the chain in the entity. In most cases, the chain name is one character. This is a restriction of the PDB file format. However, you are free to use longer names as long as you don’t want to save them as PDB files.

This property is read-only. To change the name, use an XCSEditor.

Also available as GetName()

Type:	str

residues¶

List of all residues of this chain. The residues are sorted from N- to C-terminus. Usually the residue numbers are in ascending order (see in_sequence).

This property is read-only.

Example usage:

chain=ent.FindChain("A")
for res in chain.residues:
  print(res.name, res.atom_count)

Also available as GetResidueList(). To access a single residue, use FindResidue().

Type:	ResidueViewList (list of ResidueView)

in_sequence¶

Whether the residue numbers are in ascending order. For example:

chain=ent.FindChain("A")
print(chain.residues) # [A.GLY1, A.GLY2, A.GLY4A, A.GLY4B]
print(chain.in_sequence) # prints true

chain=ent.FindChain("B")
print(chain.residues) # [B.GLY1, B.GLY4, B.GLY3]
print(chain.in_sequence) # prints false

atoms¶

Get list of all atoms of this chain. To access a single atom, use FindAtom().

This property is read-only. Also available as GetAtomList()

Type:	AtomViewList (list of AtomView)

bounds¶

Axis-aligned bounding box of the chain. Read-only

Type:	ost.geom.AlignedCuboid

mass¶

The total mass of this chain in Dalton. Also available as GetMass()

Type:	float

center_of_mass¶

Center of mass. Also available as GetCenterOfMass()

Type:	Vec3

center_of_atoms¶

Center of atoms (not mass weighted). Also available as GetCenterOfAtoms().

Type:	Vec3

handle¶

The chain handle this view points to. Also available as GetHandle().

Type:	ChainHandle

in_sequence

Whether the residue numbers are in ascending order. Note that the value of in_sequence is independent from the value of ChainHandle.in_sequence.

Type:	bool

geometric_center¶

Mid-point of the axis aligned bounding box of the entity.

Type:	Vec3

valid¶

Validity of view.

Type:	bool

AddAtom(atom_handle[, view_add_flags])¶

Add atom to the view. If the residue of the atom is not already part of the view, it will be added. If the atom does not belong to chain, the result is undefined.

Parameters:	atom_handle (AtomHandle) – The atom to be added view_add_flags (int / ViewAddFlag) – An ORed together combination of ViewAddFlag
Return type:	AtomView

AddResidue(residue_handle[, view_add_flags])¶

Add residue to the view. If the atom does not belong to chain, the result is undefined. By default, only the residue, but no atoms are added to the view. To change the behavior, pass in a suitable combination of ViewAddFlag.

Parameters:	residue_handle (ResidueHandle) – The residue handle to be added. view_add_flags (int / ViewAddFlag) – An ORed together combination of ViewAddFlag
Return type:	ResidueView

FindAtom(res_num, atom_name)¶

Find atom with the given residue number and atom name.

Parameters:	res_num (ResNum) – The residue number atom_name (str) – The atom name
Returns:	The atom view, or an invalid atom view if no atom with the given parameters is part of the view.
Return type:	AtomView

FindResidue(res_num)¶

Find residue by residue number.

Parameters:	res_num (ResNum) –
Return type:	ResidueView
Returns:	The residue view, or an invalid residue view if no residue with the given residue number is in the view.

GetCenterOfAtoms()¶

See center_of_atoms

GetCenterOfMass()¶

See center_of_mass

GetEntity()¶

The parent entity.

GetGeometricCenter()¶

See geometric_center

GetHandle()¶

See handle

GetMass()¶

See mass

GetName()¶

See name

GetResidueByIndex(index)¶

Returns the residue view at index. If index is negative or bigger than the number of residues minus one, an invalid ResidueView is returned.

Parameters:	index (int) – The index
Return type:	ResidueView

GetResidueList()¶

See residues

InSequence()¶

See in_sequence

IsValid()¶

See valid

RemoveResidue(residue)¶

Remove residue from chain. If the residue is not part of the view, the chain is left unchanged.

Parameters:	residue (ResidueView) – The residue view. May be invalid
Return type:	None

RemoveResidues()¶

Remove all residues from this chain view

Select(query, flags=0)¶

Perform query on chain view. See EntityHandle.Select().

Parameters:	query (Query / str) – The query flags (int / QueryFlag) – An ORed together combination of QueryFlag
Return type:	EntityView

class ResidueView¶

A view representation of a ResidueHandle. Mostly, the same functionality is provided as for the handle.

handle¶

The residue handle this view points to. Also available as GetHandle().

Type:	ResidueHandle

name¶

The residue name is usually a str of 3 characters, e.g. GLY for glycine or ALA for alanine, but may be shorter, e.g. G for guanosine, or longer for structures loaded from formats other than PDB.

This property is read-only. To change the name of the residue, use EditorBase.SetResidueName().

number¶

The number of this residue. The residue number has a numeric part and an insertion-code. This property is read-only. Also available as GetNumber().

Type:	ResNum

one_letter_code¶

For amino acids, and nucleotides the one_letter_code is an alpha-numeric character. For unknown or more exotic residues, the one letter code is set to ‘?’.

Example

This code-snippet shows how to get the sequence string from a list of residues.

print(''.join([r.one_letter_code for r in chain.residues]))

Type:	str

bounds¶

Axis-aligned bounding box of the residue view. Read-only

Type:	ost.geom.AlignedCuboid

mass¶

The total mass of this residue in Dalton. Also available as GetMass().

Type:	float

center_of_mass¶

Center of mass. Also available as GetCenterOfMass()

Type:	Vec3

center_of_atoms¶

Center of atoms (not mass weighted). Also available as GetCenterOfAtoms().

Type:	Vec3

chain¶

The chain this residue belongs to. Read-only. Also available as GetChain()

Type:	ChainView

handle

The residue handle this view points to

Type:	ResidueHandle

atoms¶

Get list of all atoms of this residue. To access a single atom, use FindAtom().

This property is read-only. Also available as GetAtomList()

Type:	AtomHandleList (list of AtomHandle)

index¶

Residue index (starting at 0) within chain view.

RemoveAtom(atom_view)¶

Remove atom from residue and all associated bonds. If the atom is not part of the view, the residue view is left unchanged.

Parameters:	atom_view (AtomView) – The atom to be removed. May be an invalid handle
Return type:	None

GetHandle()¶

See handle

GetMass()¶

See mass

GetChain()¶

See chain

FindAtom(atom_name)¶

Find atom by name. Returns the atom, or an invalid atom if no atoms with the given name is part of the view.

Parameters:	atom_name (str) –
Return type:	AtomView

GetIndex()¶

See index

GetCenterOfMass()¶

See center_of_mass

IsAtomIncluded(atom_handle)¶

Returns true if the given atom is part of the view, false if not.

Parameters:	atom_handle (AtomHandle) –
Return type:	bool

GetGeometricCenter()¶

See geometric_center

AddAtom(atom_handle[, flags])¶

Add atom to the view.

Parameters:	atom_handle (AtomHandle) – Atom handle to be added flags (int / ViewAddFlag) – An ORed together combination of ViewAddFlag
Return type:	AtomView

GetCenterOfAtoms()¶

See center_of_atoms

GetAtomList()¶

See atoms

Select(query, flags=0)¶

Perform selection on residue view. See EntityHandle.Select().

Parameters:	query (Query / str) – The query flags (int / QueryFlag) – An ORed together combination of QueryFlag
Return type:	EntityView

class AtomView¶

A view representation of an AtomHandle. Mostly, the same functionality is provided as for the handle.

handle¶

The underlying AtomHandle of the atom view. Also available as GetHandle().

Type:	AtomHandle

hash_code¶

A unique identifier for this atom view. Note, that this is not the same as for the atom handle (see AtomHandle.hash_code).

Type:	int

GetHandle()¶

See handle

GetHashCode()¶

See hash_code

Functions¶

Residue Numbering¶

class ResNum(num, ins_code='\0')¶

Number for a residue. The residue number has a numeric part and an (optional) insertion-code. You can work with this object as if it was an integer and comparison will look first at the numeric part and then the insertion-code. All access to existing objects is read-only. Openstructure supports a range of (-8388608 to 8388607) for the numeric part. However, the PDB format only supports a range of (-999, 9999). This becomes relevant when a structure is saved in PDB format where an IOException is raised if the PDB range is not respected.

Parameters:	num (int) – Numeric part of residue number. ins_code (str) – Alpha-numeric part of residue number (optional insertion code). Only first character kept.

num¶

Numeric part of residue number.

Type:	int

ins_code¶

Alpha-numeric part of residue number (insertion code). Single character.

Type:	str

GetNum()¶

Returns:	num

GetInsCode()¶

Returns:	ins_code

ChainType¶

A ChainType fills the ChainHandle.type attribute. Different types are described in the ChainType enum. The type is set with an editor in EditorBase.SetChainType(). Further convenience functions are described here.

class ChainType¶

The ChainType enum enumerates all types defined by the PDB for the MMCif file format. Following values are supported:

CHAINTYPE_POLY, CHAINTYPE_NON_POLY, CHAINTYPE_WATER, CHAINTYPE_POLY_PEPTIDE_D, CHAINTYPE_POLY_PEPTIDE_L, CHAINTYPE_POLY_DN, CHAINTYPE_POLY_RN, CHAINTYPE_POLY_SAC_D, CHAINTYPE_POLY_SAC_L, CHAINTYPE_POLY_DN_RN, CHAINTYPE_UNKNOWN, CHAINTYPE_MACROLIDE, CHAINTYPE_CYCLIC_PSEUDO_PEPTIDE, CHAINTYPE_POLY_PEPTIDE_DN_RN, CHAINTYPE_N_CHAINTYPES

Where CHAINTYPE_N_CHAINTYPES holds the number of different types available.

ChainTypeFromString(identifier)¶

Create a ChainType item for a given string.

Parameters:	identifier (str) – String to request a type for.
Raises:	runtime_error if identifier is unrecognised.
Returns:	ChainType

StringFromChainType(type)¶

Return the String identifier for a given type.

Parameters:	type (ChainType) – To be translated
Raises:	runtime_error if type is unrecognised.
Returns:	str

ViewAddFlag¶

class ViewAddFlag¶

Defines flags controlling behaviour of routines adding handles to views:

• INCLUDE_ATOMS - Include all atoms when adding a residue handle to a view
• INCLUDE_RESIDUES - Include all residues when adding a chain to a view
• INCLUDE_CHAINS - Include all chains when creating a new entity view
• INCLUDE_ALL = INCLUDE_ATOMS | INCLUDE_RESIDUES | INCLUDE_CHAINS - Convenience flags to include all substructures
• CHECK_DUPLICATES - If set, it will be checked that no duplicates are created when adding a new handle

Flags can be ORed to combine them.

SecStructure¶

class SecStructure(type)¶

Defines a secondary structure type following the types defined by DSSP.

Parameters:	type (SecStructure.Type / str) – Type to be set for this object.

IsHelical()¶

Returns:	True, if the set type is any type of helix (i.e. ALPHA_HELIX, PI_HELIX or THREE_TEN_HELIX)

IsExtended()¶

Returns:	True, if the set type is any type of beta sheet (i.e. EXTENDED, BETA_BRIDGE)

IsCoil()¶

Returns:	True, if the set type is any type of coil (i.e. TURN, BEND or COIL)

__str__()¶

Returns:	The character corresponding to the set type (see SecStructure.Type)

class SecStructure.Type¶

Enumerates all popssible secondary structure types distinguished by DSSP. Their values with the corresponding character code are listed here:

ALPHA_HELIX = ‘H’ PI_HELIX = ‘I’ THREE_TEN_HELIX = ‘G’ EXTENDED = ‘E’

BETA_BRIDGE = ‘B’ TURN = ‘T’ BEND = ‘S’ COIL = ‘C’

ChemClass¶

class ChemClass(chem_class)¶

The chemical class is used to broadly categorize residues based on their chemical properties. For example, peptides belong to some PEPTIDE_LINKING class. Possible values as constant variable names and as characters:

PEPTIDE_LINKING = ‘P’ D_PEPTIDE_LINKING = ‘D’ L_PEPTIDE_LINKING = ‘L’ RNA_LINKING = ‘R’ DNA_LINKING = ‘S’ NON_POLYMER = ‘N’

L_SACCHARIDE = ‘X’ D_SACCHARIDE = ‘Y’ SACCHARIDE = ‘Z’ WATER = ‘W’ UNKNOWN = ‘U’

The constants are defined directly within the mol module. Python can implicitly convert characters to objects of this type. Note however that only the first character of a str object is considered!

Parameters:	chem_class (str) – Chemical class to set.

IsPeptideLinking()¶

Returns:	True, if set class is PEPTIDE_LINKING, D_PEPTIDE_LINKING or L_PEPTIDE_LINKING

IsNucleotideLinking()¶

Returns:	True, if set class is RNA_LINKING or DNA_LINKING

ChemType¶

class ChemType¶

The chemical type of a residue is a classification of all compounds obtained from the PDB component dictionary. For example, ions belong to the class IONS, amino acids to AMINOACIDS. Possible values as constant variable names and as characters:

IONS = ‘I’ NONCANONICALMOLS = ‘M’ SACCHARIDES = ‘S’ NUCLEOTIDES = ‘N’ AMINOACIDS = ‘A’

COENZYMES = ‘E’ WATERCOORDIONS = ‘C’ DRUGS = ‘D’ WATERS = ‘W’ UNKNOWN = ‘U’

Python can implicitly convert characters to objects of this type. Note however that only the first character of a str object is considered!

Parameters:	chem_type (str) – Chemical type to set.

IsIon()¶

Returns:	True, if set type is IONS or WATERCOORDIONS

IsNucleotide()¶

Returns:	True, if set type is NUCLEOTIDES

IsSaccharide()¶

Returns:	True, if set type is SACCHARIDES

IsAminoAcid()¶

Returns:	True, if set type is AMINOACIDS

IsCoenzyme()¶

Returns:	True, if set type is COENZYMES

IsDrug()¶

Returns:	True, if set type is DRUGS

IsNonCanonical()¶

Returns:	True, if set type is NONCANONICALMOLS

IsWater()¶

Returns:	True, if set type is WATERS

IsKnown()¶

Returns:	True, if set type is not UNKNOWN