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Ligand Binding Sites

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Proteins are dynamic macromolecules that carry out a wide variety of essential processes; however, the activities of most proteins depend on their interactions with other molecules or ions, known as ligands.
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Related Experiment Video

Updated: Aug 10, 2025

Quantitative Structure-Activity Relationship, Activity Prediction, and Molecular Dynamics of Non-nucleotide Reverse Transcriptase Inhibitors

Quantitative Structure-Activity Relationship, Activity Prediction, and Molecular Dynamics of Non-nucleotide Reverse Transcriptase Inhibitors

Published on: May 9, 2025

In situ ligand restraints from quantum-mechanical methods.

Dorothee Liebschner¹, Nigel W Moriarty¹, Billy K Poon¹

¹Molecular Biosciences and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.

Acta Crystallographica. Section D, Structural Biology

|February 10, 2023

Summary

Generating accurate geometric restraints for ligands in protein structures is challenging. The Quantum Mechanical Restraints (QMR) procedure optimizes ligand geometry in situ, improving stereochemical accuracy in crystallographic refinement.

Keywords:

Quantum Mechanical Restraints ligand restraints macromolecular crystallography quantum mechanics refinement

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Area of Science:

Structural biology
Computational chemistry
Crystallography

Background:

Ligands in macromolecular crystallography pose challenges for geometric restraint generation due to chemical variability and novel interactions.
Quantum-mechanical methods offer accurate ligand geometries but struggle with flexible molecules and multiple energy minima.

Purpose of the Study:

To develop a novel procedure for generating accurate geometric restraints for ligands during crystallographic refinement.
To account for the influence of the protein environment on ligand geometry.

Main Methods:

The Quantum Mechanical Restraints (QMR) procedure optimizes ligand geometry in situ within the protein binding pocket.
Optimized geometries are used to generate target values for crystallographic refinement restraints.

Main Results:

QMR restraints resulted in lower deviations from target stereochemistry compared to conventional restraints across >2330 ligand instances.
The QMR approach demonstrated particular accuracy in generating torsion restraints for ligands and other molecules.

Conclusions:

The QMR procedure effectively addresses challenges in ligand restraint generation for macromolecular crystallography.
This method enhances the stereochemical accuracy of refined protein-ligand models.