Insights on the supramolecular polymorphism of poly(γ-benzyl-L-glutamate) rod-like peptides from atomistic molecular dynamics simulations

This work reports an all-atom molecular dynamics study of the first stages of aggregation of poly(γ-benzyl-L-glutamate)—PBLG—polymers end-capped with C60. PBLG self-assembles in water and shows polymorphism when specific changes in the molecular structure are made. Three variants of PBLG are compared, which differ for the location of the C60 moiety: N-terminus, C-terminus, or both. The aim of the computational experiments was to rationalize the key molecular properties that are relevant to the supramolecular polymorphism. Single-peptide simulations in tetrahydrofuran and in water allowed to quantify the strength of the self-assembly driving force in terms of the overall order parameter of the phenyl rings that are “coating” the peptides. Two-peptide simulations for the singly capped peptides showed that two kinds of aggregates can be formed: one “slow” thermodynamically more stable, and one “fast” kinetically favoured. These first-stage aggregates are interpreted as the seeds leading to different self-assemblies. Graphical abstract: [Figure not available: see fulltext.]