Exploring the potential energy surfaces of association of NO with aminoacids and related organic functional groups: the role of entropy of association

Abstract

Association between NO and each of the 20 amino acids and their related organic functional groups was studied by exploring the configuration space of the potential energy of association surface by using the multiple minima hypersurface procedure. AM1 semiempirical Hamiltonian was used in order to explore such complex hypersurfaces of biological molecular interactions at finite computational times. An appropriate test with a set of NO and small molecule complexes obtained at the MP2/6-311++g(2d,2p) level of theory was also carried out. Stabilization energies of larger models were also evaluated at the conventional PBE1PBE/6-31g(d,p) DFT level. NO–aminoacid hypersurface explorations yielded that interactions of NO with NH group together with the C=O belonging to the backbone appeared predominant in all cases. Models of polar aminoacids and NO also show stable interactions with the lateral chains. Interactions with charged amino acids were found as the most stable and Lys was, undoubtedly, the preferred association. The study of these kinds of interactions must take into account the deepest and other minima because the entropy of association plays an important role.