Ramachandran backbone potential energy surfaces of aspartic acid and aspartate residues: implications on allosteric sites in receptor–ligand complexations

Ramachandran backbone potential energy surfaces (PES) were generated for N-acetyl-l-aspartic acid-N′-methylamide and N-acetyl-l-aspartate-N′-methylamide. Relatively few minima were observed from the Ramachandran PES of the aspartate ion while many existed for both endo and exo forms of the aspartic acid residue. By comparing the relative stabilization energies as well as the vertical and adiabetic proton affinities of the two forms the aspartic …