# New Generation of General AMBER Force Field for Biomedical Research

> **NIH NIH R01** · UNIVERSITY OF PITTSBURGH AT PITTSBURGH · 2022 · $346,991

## Abstract

New Generation of General AMBER Force Field for Biomedical Research
Molecular simulation plays an essential role in biochemical and biophysical research. Its major
application is to decipher molecular interactions between small molecule ligands and
biomolecules, especially protein receptors, so that highly potent agonists or antagonists can be
discovered to enhance or eradicate target functions. Despite tremendous efforts spent on
development, it is still very challenging to accurately predict protein-ligand binding. A key
element to a successful prediction is the quality of practical molecular mechanics force field
(MMFF). From the viewpoint of feasibility, the classical additive force field is in a unique position
to offer computational efficiency while maintaining robustness for accurate and automated
parametrization, which cannot be easily afforded by a polarizable force field. The other key factor
to a successful prediction is the ability of the sampling strategy to effectively sample “hidden”
events that are coupled with state transitions. The major goal of this project is to develop and
test the 3rd generation of GAFF (GAFF3) to significantly improve the quality of the general-
purpose AMBER force fields. GAFF3 will be critically evaluated in studying biomolecule-ligand
interactions using a novel GPU-accelerated 𝜆 -dynamics based orthogonal space tempering
(OST) algorithm. The advanced sampling technique will guarantee that our macromolecule-ligand
binding free energy calculations is not complicated by existing sampling issues so that GAFF3
can be objectively evaluated. We will first develop GAFF3 utilizing ABCG2, a new physical charge
model which has demonstrated its superior performance in large scale solvation free energy
calculations; New force field parameterization techniques, such as applying ANI-1x potentials to
fast detect “bad” torsional parameters, will be extensively applied in GAFF3 development. We will
then critically evaluate the GAFF3 performance in studying biomolecule-ligand interactions using
both pathway-based and endpoint free energy methods. The OST sampling method will be
developed and implemented for this evaluation effort. Last, we plan to apply a variety of strategies
to handle “difficult” molecules identified by us or our users. Those strategies will include fine atom
typing and introduction of new functional forms. We believe that those efforts will allow GAFF3 to
approach the performance limit an additive model could have. We will also expand the chemical
space of GAFF3 to cover those elements not covered by the current GAFF, but frequently
occurring in drugs and PDB ligands. Therefore, the successful pursuit of these research aims will
facilitate us to surmount the challenges in accurately modeling protein-ligand and nucleic acid-
ligand binding.

## Key facts

- **NIH application ID:** 10503886
- **Project number:** 1R01GM147673-01
- **Recipient organization:** UNIVERSITY OF PITTSBURGH AT PITTSBURGH
- **Principal Investigator:** Junmei Wang
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $346,991
- **Award type:** 1
- **Project period:** 2022-09-24 → 2026-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10503886

## Citation

> US National Institutes of Health, RePORTER application 10503886, New Generation of General AMBER Force Field for Biomedical Research (1R01GM147673-01). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10503886. Licensed CC0.

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