Subtransition of multilamellar L-alpha, dibehenoyl (C-n=22) phosphatidylcholine

In multilamellar phospholipids in which the number of carbons per hydrocarb on chain (C-n) is equal to or less than 18, e.g., L-alpha, Dipalmitoyl phos phatidylcholine (DPPC) for C-n = 16 and L-alpha, Distearoyl phosphatidylcho line (DSPC) for C-n = 18, the subtransition appears only during the heating process under atmospheric pressure after the phospholipids satisfy some sp ecial conditions such as the long-term cooling storage around 0 degreesC fo r more than 72 h. However, the subtransition of multilamellar L-alpha. Dibe henoyl phosphatidylcholine with C-n = 22 (abbreviated as DBPC) appears not only during heating, but also in the subsequent cooling run without any spe cial conditions under atmospheric pressure, and it is confirmed that the su btransition of multilamellar DBPC is composed of two phenomena. X-ray scatt ering analyses indicated changes of hydrocarbon chain packing as the subtra nsition by the following two-step process, orthorhombic symmetry reversible arrow quasi-orthorhombic symmetry reversible arrow quasi-hexagonal symmetr y. These experimental results closely correspond to the phenomena under hig h pressure. which are obtained from multilamellar DPPC and DSPC conditioned by high-pressure melting above 250 MPa.