We have made progress toward developing a set of phosphorylated amino acid parameters for the AMBER-FB15 protein force field. We focused on three amino acids for which phosphorylation mainly occurs – phosphoserine, phosphothreonine and phosphotyrosine – in the singly and doubly deprotonated states. Geometry optimizations were performed for the target molecules at the B97-D3/6-31G* level of theory for singly deprotonated states and M06-2X/6-31+G* for doubly deprotonated states in grids that scan over the backbone phi and psi dihedral angles. A recursive scanning procedure was employed to ensure more comprehensive exploration of local minima on the potential surface. The lowest-energy geometries at each grid point are re-optimized using MP2/aug-cc-pVDZ with energies and gradients calculated at the MP2/CBS and MP2/aug-cc-pVTZ levels. The procedure was repeated for the chi1 and chi2 dihedral angles on each side chain for the target molecules. The potential energy surfaces constructed will be used with the ForceBalance program in order to refine previously published AMBER parameters.<br/>

Development of phosphorylated amino acid parameters for AMBER-FB15

255th National Meeting (2018)

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