Solid state N-14 and P-31 MAS NMR: New tools to study electrostatic binding of peptides on biomembrane surfaces

• The effect of electrostatic peptide association via its basic residues on lipid headgroup orientation in biological lipid membranes was investigated by monitoring both 14N and 31P nuclear magnetic resonance (NMR) spectroscopy. Lipid membranes were in the liquid crystalline phase at 308K and consisted of anionic DMPG or cationic DDAB added to neutral DMPC at different ratios to but also by ternary lipid bilayers with zero nominal surface charge. The quadrupolar splitting of the 14N nucleus and the isotropic chemical shift value of the 31P nucleus shows a systematic response to changes in the surface electrostatic charge. Also by utilizing the naturally occurring spin reporters 14N and 31P both parts of the choline headgroup electric dipole P---N+(CH3)3 can be observed. This approach provides information about association between lipid bilayers and proteins but also changes in the headgroup surrounding electrostatic environment. Previous results indicate that the interaction between pentalysine, a highly basic peptide with five positive charges, and lipid membranes is purely electrostatic. By adding pentalysine to membranes at different ratios the response of the lipid headgroup to pure electrostatic peptide association could be determined.

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