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Ligand PDBQT writer shifts columns for four-character atom names

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
86/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
python
Domain
tooling

Research direction

Start at PreparedLigand.to_pdbqt() and reproduce with the pinned 1S63 ligand SDF and published branch bonds. Check the emitted chlorine record against the stated PDBQT column positions, add a regression for four-character atom names and explicit rejection of longer names, and verify that Vina accepts the generated ligand.

Written by the indexing model from the issue text.

Description

bug component:molsysmt

What

DockingMT's temporary ligand PDBQT writer shifts fixed-width fields when an atom name has four characters. Vina's official 1S63 ligand source contains a chlorine atom that DockingMT names Cl23; the generated record places 3 in the alternate-location column and shifts the residue and coordinates. Parsing the Y field from columns 39-46 then fails (4 131.71).

Reproduction

Convert the pinned AutoDock Vina 1S63 ligand SDF to MolSysMT, request the six published ligand branch bonds, and call PreparedLigand.to_pdbqt(). The emitted chlorine line starts ATOM 29 Cl23 LIG and has a malformed coordinate field. Source: ccsb-scripps/AutoDock-Vina commit 3c65c0b3e6c2c1d183f6a175ecb65e3c5ba91645, example/docking_with_zinc_metalloproteins/data/1s63_ligand.sdf.

Expected

PDBQT atom-name field occupies exactly columns 13-16 for one- through four-character names, coordinates stay in columns 31-54, and Vina accepts the generated ligand. Names longer than four characters fail explicitly rather than shifting fields.

DockingMT owns this temporary writer fix. General PDBQT serialization belongs to uibcdf/molsysmt#214; the 1S63 regression should inform its eventual implementation. Related matrix: uibcdf/dockingmt#17.

Dominant language
Python
Stars
1
Forks
0
Avg merge
30m
Merged PRs (30d)
1

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