Determining the Helical Tilt Angle of a Transmembrane Helix in Mechanically Aligned Lipid Bilayers Using EPR Spectroscopy

This study demonstrates the feasibility of obtaining structural topology and helical tilt information of an integral transmembrane helix inserted into aligned planner-supported phospholipid bilayers (mechanically aligned bilayers) using a spin-label EPR approach. Significant changes are observed in the hyperfine splitting values at various orientations of the spin-labeled transmembrane helix with respect to the static magnetic field (B 0). The hyperfine splitting values gleaned from the orientational dependent EPR spectra allow the helical tilt of the transmembrane helix to be determined.