How to generate multiple conformers of a ligand using OpenBabel?

OpenBabel [1] offers several functions including file format conversion, generation of 3D structures from smiles, and so on. In this article, we are going to generate multiple conformers of a ligand using OpenBabel.

We will use the command-line tool of OpenBabel.

Let’s say, we have an sdf file of a ligand and we want to generate 50 conformers in the same format. Then we will use the following command:

$ obabel -i sdf input.sdf -O conformers.sdf --conformer --nconf 50 --score rmsd --writeconformers

Generating low-energy conformers

If you want to get low-energy conformers for the ligand (input.sdf), then you can use the confab argument. For this, the input file must contain one or more 3D structures. Let’s generate 50 low-energy conformers using the confab argument.

$ obabel input.sdf -O conformers.sdf --confab --conf 50

You can also generate a confab report using the confabreport argument. This argument can also compare the conformers to the reference input structure as shown below:

$ obabel conformers.sdf -oconfabreport -xf input.sdf -xr 1.0

Here, -xr defines the RMSD value within which the conformers are to be compared to the reference (input) structure.

You can generate thousands of conformers depending upon your requirement.

References

1. O’Boyle, N. M., Banck, M., James, C. A., Morley, C., Vandermeersch, T., & Hutchison, G. R. (2011). Open Babel: An open chemical toolbox. Journal of cheminformatics, 3(1), 33.