Comparing the Structural Topology and Dynamic Properties of a Model Peripheral Membrane Peptide Magainin-2 Utilizing X- and Q-Band EPR Spectroscopy

Probing the structural and dynamic properties of membrane proteins poses a very difficult problem due to their hydrophobic amino-acid composition and lipid environment they are associated with. To unravel this dilemma lipid membrane mimics have been used to establish a medium by which membrane proteins can be studied. Magnetically aligned phospholipid bilayers (bicelles) coupled with magnetic resonance spectroscopy can be used to extract pertinent information related to their structural topology. This information can be obtained by aligning the samples with respect to the static magnetic field and measuring the corresponding anisotropic spectral parameters. Our lab uses both solid-state NMR and spin-label EPR spectroscopy to study membrane proteins. EPR spectroscopy offers unique advantages over NMR spectroscopy due to a higher sensitivity and a different frequency domain for probing dynamics. These facts have led us to perform EPR spectroscopic alignment studies on the surface peptide magainin-2, which has been shown to exhibit antimicrobial activity by pore formation in two different frequency domains X-Band (9 GHz) and Q-Band (34 GHz). New and unique EPR lineshapes were obtained which not only elegantly contrast integral and peripheral peptide topologies, but also have implications for further elucidating antimicrobial dynamics and their corresponding mechanisms.