FAQ#

Is there a sequence database available?#

Yes! As of the latest release (2024-02), there is now an interface to fetch the full database of sequences for all PDB files available in the pinder dataset.

>>> from pinder.core.index.utils import get_sequence_database
>>> seq_db = get_sequence_database()
>>> seq_db
                                            pdb                                           sequence  pdb_kind
0                    7sqc__ME1_A0A2K3DEG1-L.pdb  QKERVAFVTAVAEMAKNPQNIEALQQAGAMALLRPLLLDNVPSIQQ...    ligand
1                      5f2y__C1_UNDEFINED-R.pdb                          GEIAKALREIAKALREXAWAHREEA  receptor
2        2xvr__F51_P19726--2xvr__G55_P19726.pdb  LTADVLIYDIEDAMNHYDVRSEYTSQLGESLAMAADGAVLAEIAGL...     dimer
3                        7c9s__D39_Q8QWB2-R.pdb  GAQVSTQKTGAHIIHYTNINYYKDSASNSLNRQDFTQDPSKFTEPV...  receptor
4                        4v82__FA1_Q8DHA7-R.pdb                 MEVNQLGLIATALFVLVPSVFLIILYVQTESQQK  receptor
...                                         ...                                                ...       ...
3826759    4pkn__Q1_Q548M1--4pkn__T1_Q548M1.pdb  AAKDVKFGNDARVKMLRGVNVLADAVKVTLGPKGRNVVLDKSFGAP...     dimer
3826760                   3lu0__C1_P0A8V2-L.pdb  KKRIRKDFGKRPQVLDVPYLLSIQLDSFQKFIEQDPEGQYGLEAAF...    ligand
3826761    6i0o__A1_P12268--6i0o__A4_P12268.pdb  SYVPDDGLTAQQLFNCGDGLTYNDFLILPGYIDFTADQVDLTSALT...     dimer
3826762                   8fc1__N1_Q5SHQ4-R.pdb  RLTAYERRKFRVRNRIKRTGRLRLSVFRSLKHIYAQIIDDEKGVTL...  receptor
3826763                  7ebr__D28_J9Z449-R.pdb                       NFYKDSYAASASKQDFSQDPSKFTEPVV  receptor

[3826764 rows x 3 columns]
>>> seq_db.describe()
                               pdb                                           sequence pdb_kind
count                      3826764                                            3826764  3826764
unique                     3826764                                             624894        5
top     7sqc__ME1_A0A2K3DEG1-L.pdb  ASNFTQFVLVDNGGTGDVTVAPSNFANGVAEWISSNSRSQAYKVTC...    dimer
freq                             1                                              17772  2319564
>>> seq_db.dtypes
pdb           object
sequence    category
pdb_kind    category
dtype: object

Can `pinder` be used to detect steric clashes?#

Yes! For PinderSystem-level evaluation, you can use the pinder.eval.clashes.count_pinder_clashes method.

>>> from pinder.eval.clashes import count_pinder_clashes
>>> pinder_id = "2e31__A1_Q80UW2--2e31__B1_P63208"
>>> clashes = count_pinder_clashes(pinder_id)
>>> clashes
   atom_clashes  residue_clashes  min_dist  min_dist_vdw_ratio  vdw_sum  radius                                id monomer_name  holo_mask
0             0                0  2.738283            0.894864     3.06     1.2  2e31__A1_Q80UW2--2e31__B1_P63208         holo      False
1             0                0  2.513461            0.759354     3.31     1.2  2e31__A1_Q80UW2--2e31__B1_P63208          apo      False
2            15                7  0.388205            0.111233     3.49     1.2  2e31__A1_Q80UW2--2e31__B1_P63208    predicted      False
3             0                0  3.368342            0.990689     3.40     1.2  2e31__A1_Q80UW2--2e31__B1_P63208          apo       True
4             8                5  0.627183            0.206991     3.03     1.2  2e31__A1_Q80UW2--2e31__B1_P63208    predicted       True

To detect clashes in an arbitrary PDB file, use pinder.core.structure.contacts. Note: currently clash detection is enabled only between two chains

>>> from pinder.core.structure.contacts import pairwise_clashes
>>> from pinder.core.loader.structure import Structure
>>> struct = Structure(pdb_file)
>>> AB = struct.filter("chain_id", ["A", "B"])
>>> clashes = pairwise_clashes(AB.atom_array)
>>> clashes
{'atom_clashes': 0, 'residue_clashes': 0, 'min_dist': 2.7268461070070824, 'min_dist_vdw_ratio': 0.8796277764538977, 'vdw_sum': 3.0999999999999996, 'radius': 1.2}

What do holo, apo, native, and predicted structures within `PinderSystem` mean?#

native: really its the same as holo , but in the pinder case it means the native dimer interaction as extracted from RCSB, without any coordinate transformations (except for stripping of solvent and non-protein/modified-protein atoms). It should align with the RCSB structure if you load the pinder dimer and e.g. run fetch <pdb_id> in pymol.
holo: bound conformation. Where bound in the pinder context means there are other interacting protein chains in the original RCSB crystal.
- It is generally used to refer to the individual monomer chains that compose dimers. holo-R = Receptor from native, holo-L = Ligand from native
- The only caveat is that for the test split, we transform the coordinates of the monomers using a PCA-based normalization to ensure that there are no biases introduced during evaluation from methods that may be leaky if the input proteins are pre-oriented.
- All of the train split is left un-perturbed.
- PinderSystem loads all of these for convenience, in case you need to make comparisons to the un-transformed version but tucks this into the code rather than the files on disk to ensure fair evaluation across methods.
apo: unbound conformation. A uniprot-matched pairing of a structure from a different RCSB entry that is not interacting with other proteins
predicted: structures from AF2 predictions which were uniprot-matched to the holo monomers across all systems

For some protein pairs, when I extract the apo and holo structures and align their sequence, the results don’t have the same atoms and/or sequence. How can I align monomers such that all have the same shape?#

For a more detailed example, see the example notebook (also available in the documentation).

from pinder.core import PinderSystem

pinder_id = "2gct__C1_P00766--2gct__A1_P00766"
ps = PinderSystem(pid)

# Single alternative monomer use-case without cropping
apo_RL = ps.create_apo_complex(remove_differing_atoms=False)
holo_RL = ps.aligned_holo_R + ps.aligned_holo_L

print(apo_RL.atom_array.shape[0], (holo_RL).atom_array.shape[0])
>>> (764, 758)

# With cropping such that apo only contains atom that are in holo. No guarantee that holo doesn't contain "extra" atoms not in apo.
apo_RL = ps.create_apo_complex(remove_differing_atoms=True)
print(apo_RL.atom_array.shape[0], (holo_RL).atom_array.shape[0])
>>> (756, 758)

# You can also renumber the residues in the apo structure to match the holo structure.
apo_RL = ps.create_apo_complex(remove_differing_atoms=True, renumber_residues=True)

# Pairwise cropped structure superposition: ensure ALL monomer have the same shape.
# Note: this will modify the ground-truth structure.
holo_cropped, apo_cropped, pred_cropped = ps.create_masked_bound_unbound_complexes(
  monomer_types=["apo"],
  renumber_residues=True,
)
print((
    holo_cropped.atom_array.shape[0],
    apo_cropped.atom_array.shape[0],
    pred_cropped.atom_array.shape[0],
))
>>> (756, 756, 3598)

# Pairwise including predicted monomers
holo_cropped, apo_cropped, pred_cropped = ps.create_masked_bound_unbound_complexes(
  monomer_types=["apo", "predicted"],
  renumber_residues=True,
)
print((
    holo_cropped.atom_array.shape[0],
    apo_cropped.atom_array.shape[0],
    pred_cropped.atom_array.shape[0],
))
>>> (756, 756, 756)

How can I use the evaluation harness outside of a `pinder` context?#

For a more detailed example, see the example notebook (also available in the documentation).

In short, the DockQ-related classes provided in pinder roughly follow this hierarchy:

pinder.eval.dockq.method.MethodMetrics
- For evaluating methods over many systems and producing a pinder-specific leaderboard
- Wraps BiotiteDockQ
pinder.eval.dockq.biotite_dockq.BiotiteDockQ
- The DockQ calculation interface, designed to take one native/reference and score N decoys
- Performs I/O
- Does calculations that only need to be done one (native contacts, patching canonical order, etc)
- Makes calls to DecoyDockQ in serial for list of AtomArray or vectorized over AtomArrayStack
pinder.eval.dockq.biotite_dockq.DecoyDockQ
- Takes pre-prepared models and native information and gets the metrics

For the simplest interface to calculating DockQ metrics for arbitrary inputs, say you have a ground-truth structure with 2 chains, R and L, and a list of predicted models with chains A and B.

If you know which chains between the ground-truth and models correspond with each other, you can specify the chains via native_receptor_chains, native_ligand_chain, decoy_receptor_chain, decoy_ligand_chain. If the chains are not provided, the receptor chain will be inferred based on the larger chain in both native and decoy structures.

Note the use of a list: it is possible to specify more than one chain to assign as receptor or ligand.

native_receptor_chain = ["R"]
native_ligand_chain = ["L"]
decoy_receptor_chain = ["A"]
decoy_ligand_chain = ["B"]

from pathlib import Path
from pinder.eval import BiotiteDockQ

native = Path("./native.pdb")
models = list(Path("./models").glob("*.pdb"))

bdq = BiotiteDockQ(
    native,
    models,
    backbone_definition="dockq",
    native_receptor_chain=native_receptor_chain,
    native_ligand_chain=native_ligand_chain,
    decoy_receptor_chain=decoy_receptor_chain,
    decoy_ligand_chain=decoy_ligand_chain,
    parallel_io=True,
)
metrics = bdq.calculate()

Do I have to use the `pinder` loader? How can I write my own loader?#

No! The PinderDataset torch dataset and PPIDataset torch-geometric dataset serve as example implementations of a loader. The dataset wraps the abstract PinderLoader class under the hood, which is the primary interface for loading PinderSystem objects and applying filters and/or transforms.

While not required, it is recommended to use the PinderLoader class directly to implement your own loader.

The PinderLoader brings together filters, transforms and writers to create an optionally parallel PinderSystem iterator. It can accept either a specific split name or list of system IDs as input.

from pinder.core import PinderLoader
from pinder.core.loader import filters

base_filters = [
    filters.FilterByMissingHolo(),
    filters.FilterSubByContacts(min_contacts=5, radius=10.0, calpha_only=True),
    filters.FilterByHoloElongation(max_var_contribution=0.92),
    filters.FilterDetachedHolo(radius=12, max_components=2),
]
sub_filters = [
    filters.FilterSubByAtomTypes(min_atom_types=4),
    filters.FilterByHoloOverlap(min_overlap=5),
    filters.FilterByHoloSeqIdentity(min_sequence_identity=0.8),
    filters.FilterSubLengths(min_length=0, max_length=1000),
    filters.FilterSubRmsds(rmsd_cutoff=7.5),
    filters.FilterByElongation(max_var_contribution=0.92),
    filters.FilterDetachedSub(radius=12, max_components=2),
]

# Load a list of system IDs
systems = [
    "1df0__A1_Q07009--1df0__B1_Q64537",
    "117e__A1_P00817--117e__B1_P00817",
]

loader = PinderLoader(
    ids=systems,
    base_filters = base_filters,
    sub_filters = sub_filters
)
print(loader)
>>> PinderLoader(split=None, monomers=holo, systems=2)

# Iterate over loader to apply the filters and transforms. Systems that pass all filters will be yielded.
passing_ids = []
for item in loader:
    system, feature_complex, target_complex = item
    passing_ids.append(system.entry.id)

# Each dimer object can now be used in your own loader to access any of the properties exposed by the PinderSystem class, the monomer `Structure` objects, or the underlying `biotite.structure.AtomArray` objects.

FAQ#

Is there a sequence database available?#

Can pinder be used to detect steric clashes?#

What do holo, apo, native, and predicted structures within PinderSystem mean?#

For some protein pairs, when I extract the apo and holo structures and align their sequence, the results don’t have the same atoms and/or sequence. How can I align monomers such that all have the same shape?#

How can I use the evaluation harness outside of a pinder context?#

Do I have to use the pinder loader? How can I write my own loader?#

Can `pinder` be used to detect steric clashes?#

What do holo, apo, native, and predicted structures within `PinderSystem` mean?#

How can I use the evaluation harness outside of a `pinder` context?#

Do I have to use the `pinder` loader? How can I write my own loader?#