smina Molecular Docking

Overview

smina is an AutoDock Vina 1.1.2 fork focused on flexible scoring and minimization. Accepts SDF/MOL2/PDB ligands directly (no manual PDBQT), autoboxes from a reference ligand, ships six built-in scoring functions plus arbitrary --custom_scoring terms, and prints per-atom score contributions. CLI-only — drive from Python via subprocess.

When to Use

• Re-scoring or locally minimizing an existing pose (--local_only, --minimize) without a full search
• Single-pose binding energy without docking (--score_only)
• Docking with a custom or empirical scoring function tuned to a target class
• SDF/MOL2/multi-ligand input without per-ligand PDBQT conversion
• Autoboxing the grid around a co-crystallized reference ligand
• Per-atom energy decomposition (--atom_term_data) for medchem analog design
• Batch virtual screening that parallelizes well across nodes (one CLI process per ligand)
• Use autodock-vina-docking instead when you need Vina Python bindings, Vinardo scoring, or Vina 1.2's expanded force field; use diffdock when the binding site is unknown

Prerequisites

• smina binary — conda-forge or SourceForge build
• Python: rdkit, openbabel-wheel (or system openbabel), prody, pandas, py3Dmol
• ADFR Suite for prepare_receptor (receptor PDBQT only — ligands handled by smina)
• Data: protein (PDB / PDB ID), ligand(s) as SMILES / SDF / MOL2

Check before installing — inside a pixi/conda env smina is usually already on PATH. If command -v smina succeeds, skip install; inside a pixi project invoke as pixi run smina ....

command -v smina || conda install -c conda-forge smina openbabel
pip install rdkit prody pandas py3Dmol
# ADFR Suite: https://ccsb.scripps.edu/adfr/downloads/

Quick Start

End-to-end docking using autobox from a reference ligand:

import subprocess

result = subprocess.run([
    "smina",
    "-r", "1hpv_receptor.pdbqt",
    "-l", "candidate.sdf",
    "--autobox_ligand", "1hpv_ref_ligand.pdb",
    "--autobox_add", "8",          # padding around reference (Å)
    "-o", "candidate_docked.sdf",
    "--exhaustiveness", "16",
    "--num_modes", "9",
    "--seed", "42",
], check=True, capture_output=True, text=True)

print(result.stdout.splitlines()[-15:])  # affinity table at stdout tail

Workflow

Step 1: Prepare the Receptor (PDBQT)

Strip waters/hetatms, then run ADFR Suite's prepare_receptor.

import subprocess, prody

pdb_id = "1HPV"
prody.fetchPDB(pdb_id, compressed=False)
protein = prody.parsePDB(f"{pdb_id}.pdb").select("protein")
prody.writePDB(f"{pdb_id}_protein.pdb", protein)

receptor_pdbqt = f"{pdb_id}_receptor.pdbqt"
subprocess.run([
    "prepare_receptor",
    "-r", f"{pdb_id}_protein.pdb",
    "-o", receptor_pdbqt,
    "-A", "hydrogens",
], check=True)
print(f"Receptor: {receptor_pdbqt} ({protein.numAtoms()} atoms)")

Step 2: Prepare the Ligand (SDF)

smina reads SDF directly. Generate 3D coords with RDKit.

from rdkit import Chem
from rdkit.Chem import AllChem

mol = Chem.MolFromSmiles("CC(C)(C)NC(=O)[C@@H]1CN(CCc2ccccc2)C[C@H]1O")
mol = Chem.AddHs(mol)
AllChem.EmbedMolecule(mol, randomSeed=42)
AllChem.MMFFOptimizeMolecule(mol)

w = Chem.SDWriter("candidate.sdf"); w.write(mol); w.close()
print(f"Ligand SDF: candidate.sdf ({mol.GetNumAtoms()} atoms)")

Step 3: Extract a Reference Ligand for Autoboxing

--autobox_ligand derives the grid from a reference structure.

import prody

ref = prody.parsePDB(f"{pdb_id}.pdb").select("hetero and not water and not ion")
if ref is None:
    raise RuntimeError("No reference ligand — supply explicit --center_x/--size_x")
prody.writePDB(f"{pdb_id}_ref_ligand.pdb", ref)
print(f"Ref ligand: {ref.numAtoms()} atoms, center {ref.getCoords().mean(axis=0).round(2)}")

Step 4: Run Docking with Autobox

Affinity table is printed to stdout — capture it.

import subprocess

proc = subprocess.run([
    "smina",
    "-r", receptor_pdbqt,
    "-l", "candidate.sdf",
    "--autobox_ligand", f"{pdb_id}_ref_ligand.pdb",
    "--autobox_add", "8",
    "-o", "candidate_docked.sdf",
    "--exhaustiveness", "16",
    "--num_modes", "9",
    "--energy_range", "3",
    "--cpu", "4",
    "--seed", "42",
], check=True, capture_output=True, text=True)

for line in proc.stdout.splitlines()[-15:]:
    print(line)

Step 5: Parse Poses and Affinities

Affinities go into the SDF <minimizedAffinity> property.

from rdkit import Chem
import pandas as pd

rows = []
for i, mol in enumerate(Chem.SDMolSupplier("candidate_docked.sdf", removeHs=False)):
    if mol is None:
        continue
    aff = float(mol.GetProp("minimizedAffinity")) if mol.HasProp("minimizedAffinity") else None
    rmsd = float(mol.GetProp("minimizedRMSD")) if mol.HasProp("minimizedRMSD") else None
    rows.append({"pose": i + 1, "affinity_kcal_mol": aff, "rmsd_to_best": rmsd})

df = pd.DataFrame(rows).sort_values("affinity_kcal_mol")
print(df.to_string(index=False))
print(f"Best: {df.iloc[0]['affinity_kcal_mol']:.2f} kcal/mol")

Step 6: Local Minimization of an Existing Pose

--local_only refines an input pose without global search.

import subprocess

subprocess.run([
    "smina",
    "-r", receptor_pdbqt,
    "-l", "candidate_pose.sdf",
    "--autobox_ligand", "candidate_pose.sdf",   # box around the pose itself
    "--autobox_add", "4",
    "-o", "candidate_min.sdf",
    "--local_only",
    "--minimize_iters", "1000",
], check=True, capture_output=True, text=True)
print("Local minimization complete: candidate_min.sdf")

Step 7: Visualize the Docked Complex

import py3Dmol

with open(f"{pdb_id}_protein.pdb") as f: rec = f.read()
with open("candidate_docked.sdf") as f: lig = f.read()

view = py3Dmol.view(width=800, height=600)
view.addModel(rec, "pdb"); view.setStyle({"model": 0}, {"cartoon": {}})
view.addModel(lig.split("$$$$")[0] + "$$$$", "sdf")
view.setStyle({"model": 1}, {"stick": {}})
view.zoomTo({"model": 1}); view.show()

Step 8: Batch Virtual Screening

One smina process per ligand parallelizes well across cores or cluster nodes.

import subprocess, pandas as pd
from rdkit import Chem
from rdkit.Chem import AllChem

library = pd.DataFrame({
    "name":   ["cpd_001", "cpd_002", "cpd_003"],
    "smiles": ["CC(=O)Oc1ccccc1C(=O)O",
               "CC(C)Cc1ccc(cc1)C(C)C(=O)O",
               "OC(=O)c1ccccc1O"],
})

results = []
for _, row in library.iterrows():
    lig_sdf, out_sdf = f"{row['name']}.sdf", f"{row['name']}_docked.sdf"
    mol = Chem.MolFromSmiles(row["smiles"]); mol = Chem.AddHs(mol)
    AllChem.EmbedMolecule(mol, randomSeed=42); AllChem.MMFFOptimizeMolecule(mol)
    w = Chem.SDWriter(lig_sdf); w.write(mol); w.close()

    proc = subprocess.run([
        "smina", "-r", receptor_pdbqt, "-l", lig_sdf,
        "--autobox_ligand", f"{pdb_id}_ref_ligand.pdb", "--autobox_add", "8",
        "-o", out_sdf, "--exhaustiveness", "8", "--num_modes", "1",
        "--cpu", "2", "--seed", "42",
    ], capture_output=True, text=True)

    if proc.returncode != 0:
        results.append({"name": row["name"], "affinity_kcal_mol": None})
        continue
    docked = next(iter(Chem.SDMolSupplier(out_sdf, removeHs=False)))
    aff = float(docked.GetProp("minimizedAffinity")) if docked and docked.HasProp("minimizedAffinity") else None
    results.append({"name": row["name"], "affinity_kcal_mol": aff})

ranked = pd.DataFrame(results).sort_values("affinity_kcal_mol")
ranked.to_csv("screening_results.csv", index=False)
print(ranked.to_string(index=False))

Key Parameters