Alignment Studies Employing the Rigid TOAC Spin Label Utilizing Electron Paramagnetic Resonance (EPR)

For electron paramagnetic resonance (EPR) spectroscopic studies, the TOAC spin label offers the unique advantage over other conventional labels in that it reports accurate backbone motion and peptide dynamics due to its rigid nature. This label has become extremely important in EPR studies to study membrane protein topology and their associated dynamics. Additionally, some researches have also developed spectroscopic techniques using magnetically aligned (bicelles) and mechanically aligned (glass plates) lipid samples to extract additional information directly related to structural topology with respect to the membrane. Based upon the samples orientation, other anisotropic spectral parameters can also be determined. EPR spectroscopy offers a unique solution due to the fact it has a much higher sensitivity and also a different frequency domain than other conventional techniques. Thus, we have performed EPR alignment studies on two-model peptides magainin-2 and the M2δ subunit of the acetylcholine receptor. Both of these peptides have been well characterized and are 23 amino acids in length.