Fig. 4: Orbital occupancy and stabilization energies envince HBC in PPII helical bundles.
From: Hydrogen bonding patterns and cooperativity in polyproline II helical bundles
A Mean occupancy (q) of the corresponding σ*(NH/CαHα) orbitals and B mean stabilization energy (E(2)) of the corresponding n(O)/σ(CO)/π(CO)→σ*(NH/CαHα) electron delocalization for each CO···HN (squares), CO···HαCα front (circles), CO···HαCα inner (triangles) and CO···HαCα outer (inverted triangles) H-bond/interaction between PPII helices. The ab interface for the different systems is indicated in blue; the bc interface, in red, and the cd interface, in green. M06-2X/6-31 + G(d) level of theory.
