Extension of the Effective Fragment Potential Method to Macromolecules

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Biophysics

Background:

• The effective fragment potential (EFP) method accurately models noncovalent interactions in extended systems.
• Current EFP formulations are limited to systems without covalent bond breaking, restricting applications to smaller molecules.
• Accurate calculation of electronic properties in complex environments like proteins requires advanced computational methods.

Purpose of the Study:

• To extend the effective fragment potential (EFP) method to handle macromolecules (mEFP).
• To benchmark different fragmentation schemes for applying mEFP to large molecules, particularly proteins.
• To evaluate the accuracy of the quantum mechanics/macromolecular effective fragment potential (QM/mEFP) scheme for electronic properties.

Main Methods:

• Developed and presented several schemes for fragmenting macromolecules for EFP calculations.
• Benchmarked mEFP schemes using model systems, including chromophores in fluorescent proteins and phenolate in T4 lysozyme.
• Calculated electronic excitation, ionization, and electron-attachment energies using the QM/mEFP polarizable embedding scheme.

Main Results:

• All tested mEFP schemes demonstrated robust performance, accurately reproducing full quantum mechanics (QM) calculations.
• Recommended fragmentation schemes (one or two cuts per amino acid) yield errors in electronic energy differences below 0.1 eV.
• QM/mEFP shows significantly smaller errors (0.01-0.06 eV) compared to QM/molecular mechanics with point charges (up to 0.3 eV).

Conclusions:

• The macromolecular effective fragment potential (mEFP) method successfully extends EFP to large biomolecules.
• QM/mEFP provides an accurate and efficient approach for calculating electronic properties of molecules in protein environments.
• The developed fragmentation strategies offer a reliable way to apply mEFP, outperforming traditional QM/MM methods.