Structure-Directing L-Tryptophan for Supported DPPC Helices and Fractals: An Alkyl-Chain Tilt-Angle Dependence

This study reports supported one-dimensional fractals and helices of dipalmitoylphosphatidylcholine (DPPC) from interfacial and trans-membrane L-tryptophan interactions. One of the key challenges in the fabrication of phospholipid helices is unravelled using simple 2D nanotechnology techniques and the amphipathic membrane-exposed amino acid L-tryptophan. Unlike in earlier reports, in which self-assembly induced helicity exclusively to the peptide backbone in a lipid environment, this study infers the amino acid to govern the assembly of anisotropic, large-curvature lipid helices through diverse interactions such as insertion, folding, dipole reorientation, steric interactions and molecular tilt dependence, culminating in the induction of helicity in a nonhelical lipid. Molecular dynamics simulations succinctly corroborate the helix formation, implying that trans-membrane tryptophans support such segmental interactions.