Polarized IR spectra of melittin (I) incorporated into macroscopically oriented lipid membranes are reported. From the linear dichroism of the amide I and amide II vibrational bands, the spatial orientation of I helices was detd. as being preferentially parallel to the membrane normal under exptl. condition of low water content and an ordered lipid phase. The data are in accord with an orientation of membrane-incorporated I whereby the hydrophobic part of the polypeptide either spans the bilayer in the form of 2 bent helix segments or is folded back within 1 monolayer in the form of a wedge. [on SciFinder (R)]