Dependence of acyl chain packing of phospholipids on the head group and acyl chain length.

The temperature dependencies of the factor group splitting of the infrared-active CH2-scissoring bands of a series of fully hydrated gel phase diacyl phospholipids were determined. It is shown that, in all cases, the acyl chains are packed in an orthorhombic subcell and that the degree of rigidity of the subcell increases with increasing chain length. It is also demonstrated that the subcell in 3-sn-phosphatidylcholines differs from that found in 3-sn-phosphatidylethanolamines and 3-phosphatidic acids.