Self-assembling tripeptide as organogelator: the role of aromatic π-stacking interactions in gel formation

Fibril formation through self-assembly of a simple glycine derivative and X-ray diffraction study

N-(N-benzoyl glycinyl)-N,N′-dicyclohexylurea was synthesised by conjugating N-benzoyl glycine and dicyclohexylcarbodiimide (DCC) using triethylamine as base catalyst. A single crystal X-ray diffraction study reveals that the compound self-assembles into a supramolecular sheet structure by intermolecular N–H · · · O, C–H · · · O hydrogen bonding and non-bonding van der Waals interactions. A high resolution transmission electronic microscopic (HR-TEM) image of the compound exhibits formation of fibrils in the solid state.

The interactions of phenylalanines in β-sheet-like structures from molecular orbital calculations using density functional theory (DFT), MP2, and CCSD(T) methods

We present density functional theory calculations designed to evaluate the importance of π-stacking interactions to the stability of in-register Phe residues within parallel β-sheets, such as amyloids. We have used a model of a parallel H-bonded tetramer of acetylPheNH2 as a model and both functionals that were specifically designed to incorporate dispersion effects (DFs), as well as, several traditional functionals which have not been so designed. None of the functionals finds a global minimum for the π-stacked conformation, although two of the DFs find this to be a local minimum. The stacked phenyls taken from the optimized geometries calculated for each functional have been evaluated using MP2 and CCSD(T) calculations for comparison. The results suggest that π-stacking does not make an important contribution to the stability of this system and (by implication) to amyloid formation.