1 palmitoyl 2 oleoyl sn glycero 3 phosphoglycerol

Circular dichroism spectra of the analyzed compounds were obtained by means of Jasco J-815 spectropolarimeter using a quartz cell of 1 mm path length between 195–260 nm at room temperature. Peptides at final concentration of 0.13 mM were mixed with 1.31 mM POPG solution (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol, Sigma-Aldrich, St. Louis, MO, USA) in phosphate buffered saline (PBS, 10 mM phosphate buffer containing 2.7 mM potassium chloride and 137 mM sodium chloride, pH 7.4). POPG vesicle system was used as the simplified model of negatively charged lipid membrane. On the basis of the obtained spectra, alpha-helical content was determined using a CONTINLL method implemented in CDPro software using, as a reference, the database of 43 soluble and 13 membrane bound proteins (SMP56) with precisely known secondary structures [29 (link)].

Lipids, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG), 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG), 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), and 1,2dimyristoyl-sn-glycero-3-phosphocholine (DMPC), were purchased from Sigma (St. Louis, MO, USA) and used without further purification.