Rowan

Protein–Ligand Interaction Diagram

Use Rowan's protein–ligand interaction diagram utility to:

  • visualize a bound pose starting from a PDB file or from any PDB ID,
  • analyze hydrogen bonding, polar and hydrophobic interactions, and
  • generate visualizations for communicating about the quality of poses.

If anything here isn't working like you expect, let us know via contact@rowansci.com. If you'd like to use structure-based drug design tools like docking, co-folding, molecular dynamics, and FEP, consider making a Rowan account.

For best results, upload a PDB that includes hydrogens; hydrogen-bond detection expects explicit hydrogen atoms.

Load a PDB to view the structure

How it works

The diagram treats the selected ligand as the center of the binding site, then scans nearby protein residues for simple geometry-based contacts. If you provide a SMILES, RDKit is used to draw the ligand; otherwise the ligand layout is inferred from the PDB coordinates.

  • The input structure should include hydrogens. Hydrogen-bond detection depends on explicit donor hydrogens in the PDB.
  • Hydrogen bonds require a donor–hydrogen–acceptor angle of 120–180°, a donor–acceptor distance of at most 3.5 Ă…, and a hydrogen–acceptor distance of at most 2.7 Ă….
  • Polar contacts are close contacts between polar heavy atoms (N, O, or S) that are not classified as hydrogen bonds.
  • Hydrophobic contacts are close contacts between neutral carbon-like ligand atoms (C or S) and hydrophobic side-chain atoms.
  • Salt bridges are detected between charged ligand atoms and nearby charged residues.
  • Gray residue labels show generic van der Waals contacts: close heavy-atom contacts that are not classified as hydrogen bonds, salt bridges, polar contacts, or hydrophobic contacts.
  • Ligand surface outlines also use nearby residues within 5 Ă…, up to 100 residues, to help show which parts of the ligand are protein-facing versus solvent-exposed.

If this interaction diagram leaves anything to be desired, we recommend checking out the following tools: