Enantiomeric and Diastereomeric Self-Assembled Multivalent Nanostructures: Understanding the Effects of Chirality on Binding to Polyanionic Heparin and DNA.

A family of four self-assembling lipopeptides containing Ala-Lys peptides attached to a C16 aliphatic chain were synthesised. These compounds form two enantiomeric pairs that bear a diastereomeric relationship to one another (C16 -l-Ala-l-Lys/C16 -d-Ala-d-Lys) and (C16 -d-Ala-l-Lys/C16 -l-Ala-d-Lys). These diastereomeric pairs have very different critical micelle concentrations (CMCs). The self-assembled multivalent (SAMul) systems bind biological polyanions as a result of the cationic lysine groups on their surfaces. For heparin binding, there was no significant enantioselectivity, but there was a binding preference for the diastereomeric assemblies with lower CMCs. Conversely, for DNA binding, there was significant enantioselectivity for systems displaying d-lysine ligands, with a further slight preference for attachment to l-alanine, with the CMC being irrelevant.