A solid-state nuclear magnetic resonance (NMR) study for the structural elucidation of acidic phospholipid-basic polypeptide complex powder samples is presented. C-13 cross-polarization magic angle spinning (CP/MAS) experiments of poly(L-lysine)/dipalmitoylphosphatidic acid (DPPA) complex and poly(L-arginine)/DPPA complex powders were performed. The NMR spectra suggest that poly(L-lysine) forms a beta-sheet conformation on the surface of the DPPA membrane, whereas poly(L-arginine) forms an or-helix conformation. Further, changes in the chemical shift tensors of the P-31 nucleus associated with the complex formation were observed, allowing us to depict the geometry of the DPPA headgroup.