Oriented circular dichroism of a class A amphipathic helix in aligned phospholipid multilayers

The effect of lipid phase state on the orientation and conformation of a cl ass A ex-helical peptide on aligned lipid multilayers was examined using or iented circular dichroism spectroscopy. A comparison of oriented spectra in aligned peptide-lipid multilayers with CD spectra of unaligned peptide-lip id vesicle complexes is consistent with a preferential alignment of helices parallel to the membrane surface at temperatures above and below the main acyl-chain melting transition temperature of the phospholipid. Changes are observed in the oriented CD spectra with lipid phase state which are attrib uted to a subtle conformational change of the peptide on the lipid surface. The results are compared with available experimental data on membrane-acti ve lytic and antimicrobial helical peptides. (C) 2000 Elsevier Science B.V. All rights reserved.