What is Molecular Docking?
Molecular docking predicts how a small molecule (ligand) binds to a protein (receptor). It's a cornerstone of structure-based drug design, enabling virtual screening of millions of compounds.
The Docking Workflow
1. Protein Preparation
Download structure from PDBRemove water molecules and ionsAdd missing hydrogensAssign partial charges (Kollman for proteins)2. Ligand Preparation
Generate 3D coordinates from SMILESEnergy minimize the structureCalculate Gasteiger chargesDefine rotatable bonds3. Defining the Search Space
Identify the binding site (known or predicted)Set a grid box around the active siteEnsure sufficient margin (typically 5-10 Å)4. Running the Docking
Using AutoDock Vina:
vina --receptor protein.pdbqt --ligand ligand.pdbqt \
--center_x 10 --center_y 20 --center_z 15 \
--size_x 25 --size_y 25 --size_z 25 \
--out output.pdbqt --log log.txt
Interpreting Results
Binding affinity: More negative = stronger bindingRMSD: Measures pose reproducibilityVisual inspection: Check interactions (H-bonds, π-π stacking)Common Pitfalls
Not accounting for protein flexibilityOver-interpreting small affinity differencesIgnoring the scoring function limitationsSkipping experimental validation
