Accurate Proton Affinity and Gas-Phase Basicity Values for Molecules Important in Biocatalysis

Benchmark quantum calculations of proton affinities and gas-phase basicities of molecules relevant to biochemical processes, particularly acid/base catalysis, are presented and compared for a variety of multilevel and density functional quantum models. Included are nucleic acid bases in both keto and enol tautomeric forms, ribose in B-form and A-form sugar pucker conformations, amino acid side chains and backbone molecules, and various phosphates and phosphoranes, including thio substitutions. This work presents a high-level thermodynamic characterization of biologically relevant protonation states and provides a benchmark database for development of next-generation semiempirical and approximate density functional quantum models and parametrization of methods to predict pK a values and relative solvation energies.