How to Add Hydrogens to a PDB Structure (and Why pH 7.4 Matters)

By BioDockify Computational Research Team · September 3, 2026 · Tutorials

Add hydrogens to any PDB file with Open Babel at pH 7.4, understand protonation states for HIS, ASP, GLU, LYS and CYS, and learn why missing hydrogens ruin docking scores.

Read the complete article with tables, code and references on BioDockify.

Key References

• O\u2019Boyle NM et al. Open Babel: an open chemical toolbox. J Cheminform. 2011;3:33. doi:10.1186/1758-2946-3-33
• Word JM et al. Visualizing and quantifying molecular lists-of-hydrogen-bonds: VALIDATE and reduce. J Mol Graph Model. 1999. doi:10.1016/s1093-3263(99)00023-6
• RCSB PDB structure downloads and format help, rcsb.org.

Scope & Limitations

Automatic protonation assigns default states; buried or special-environment residues may need manual assignment