# Capturing Carbohydrate Conformations and Hydration Interactions with a Polarizable Bond Dipole Potential

## TL;DR

A new method called PBDPC25 improves the accuracy of modeling carbohydrate structures and their interactions with water.

## Contribution

PBDPC25 is a novel polarizable bond dipole potential that outperforms existing methods in modeling carbohydrate conformations and hydration.

## Key findings

- PBDPC25 achieves an RMSE of 2.13 kcal/mol for carbohydrate monomer conformational energies, surpassing GLYCAM06 and CHARMM36.
- Hydration energies for carbohydrate–water clusters are predicted with an RMSE of 3.50 kcal/mol, significantly better than other force fields.

## Abstract

The accurate modeling of carbohydrates is challenged by conformational flexibility, hydration, and many-body electrostatics. In this work, a polarizable bond dipole potential for carbohydrates (PBDPC25) is presented, in which C–O, O–H, and C–H bonds are represented as intrinsically polarizable dipoles. Electrostatic interactions are described through bond dipole coupling, with an orbital overlap contribution introduced to account for hydrogen bonding. For carbohydrate monomers, PBDPC25 reproduces conformational energies with a root-mean-square error (RMSE) of 2.13 kcal/mol. This accuracy exceeds that of GLYCAM06 (2.87 kcal/mol) and CHARMM36 (3.74 kcal/mol). It is also slightly better than the polarizable AMOEBA force field (2.82 kcal/mol). Optimized geometries are maintained within 0.15 Å of benchmark reference structures. This level of agreement is comparable to GLYCAM06 (0.21 Å) and close to CHARMM36 and AMOEBA (both 0.14 Å). Molecular dipole moments show excellent agreement with the reference data. Correlation coefficients exceed R2 > 0.98. For carbohydrate–water clusters, hydration energies, including many-body contributions, are predicted with an RMSE of 3.50 kcal/mol. This represents a substantial improvement over GLYCAM06, CHARMM36, and AMOEBA. These results demonstrate that PBDPC25 provides a reliable framework for modeling carbohydrate conformations and local hydration effects.