Nabedryk E, Gingold M P, Breton J
Biophys J. 1982 Jun;38(3):243-9. doi: 10.1016/S0006-3495(82)84555-4.
Polarized infrared spectroscopy has been used to investigate the orientation of gramicidin A incorporated in dimyristoylphosphatidylcholine liposomes. Dichroism measurements of the major lipid (C = O ester, PO2-, CH2) and peptide (amide A, I, II) bands were performed on liposomes (with or without gramicidin) oriented by air-drying. The mean orientation of the lipid groups and of the pi LD helix chain in the gramicidin has been determined. It can be inferred from infrared frequencies of gramicidin that the dominant conformation of the peptide in liposomes cannot be identified to the antiparallel double-helical dimer found in organic solution. No shift in lipid frequencies was observed upon incorporation of gramicidin in the liposomes. However, a slight reorganization of the lipid hydrocarbon chains which become oriented more closely to the normal to the bilayer is evidenced by a change in the dichroism of the CH2 vibrations. The infrared dichroism results of gramicidin imply a perpendicular orientation of the gramicidin transmembrane channel with the pi LD helix axis at less than 15 degrees with respect to the normal to the bilayer.
偏振红外光谱已被用于研究掺入二肉豆蔻酰磷脂酰胆碱脂质体中的短杆菌肽A的取向。对通过空气干燥取向的脂质体（含或不含短杆菌肽）进行了主要脂质（C=O酯、PO2-、CH2）和肽（酰胺A、I、II）谱带的二色性测量。已确定脂质基团和短杆菌肽中πLD螺旋链的平均取向。从短杆菌肽的红外频率可以推断，脂质体中肽的主要构象与有机溶液中发现的反平行双螺旋二聚体不同。将短杆菌肽掺入脂质体后，未观察到脂质频率的变化。然而，CH2振动二色性的变化表明，脂质烃链发生了轻微的重新排列，其取向更接近双层的法线方向。短杆菌肽的红外二色性结果表明，短杆菌肽跨膜通道垂直取向，πLD螺旋轴相对于双层法线的夹角小于15度。
