Deuterium Magic Angle Spinning NMR Used to Study the Dynamics of Peptides Adsorbed onto Polystyrene and Functionalized Polystyrene Surfaces

摘要

LKα14 is a 14 amino acid peptide with a periodic sequence of leucine and lysine residues consistent with an amphipathic α-helix. This “hydrophobic periodicity” has been found to result in an α-helical secondary structure at air-water interfaces and on both polar and non-polar solid polymer surfaces. In this paper the dynamics of LKα14 peptides, selectively deuterated at a single leucine and adsorbed onto polystyrene and carboxylated polystyrene beads, are studied using ²H Magic Angle Spinning (MAS) solid state NMR over a 100 degree temperature range. We first demonstrate the sensitivity enhancement possible with ²H MAS techniques, which in turn enables us to obtain high quality ²H NMR spectra for selectively deuterated peptides adsorbed onto solid polymer surfaces. An extensive literature shows that the dynamics of leucine side chains are sensitive to the local structural environment of the protein. Therefore the degree to which the dynamics of leucine side chains and the backbone of the peptide LKα14 are influenced by surface proximity and surface chemistry is studied as a function of temperature with ²H MAS NMR. It is found that the dynamics of the leucine side chains in LKα14 depend strongly upon the orientation of the polymer on the surface, which in turn depends on whether the LKα14 peptide adsorbs onto a polar or non-polar surface. ²H MAS line shapes therefore permit probes of surface orientation over a wide temperature range.