The Lipids

Abstract

For many amphiphilic or neutral lipid molecules, the presence of an alkyl chain residue, linked as an ester, an amide, or an ether to the “functional” moiety, often requires the polymethylene chains to be sequestered in separate domains when these substances are crystallized or even when they are transformed to the liquid crystalline state. In the crystalline state, these isolated chain regions often form a sublattice of methylene groups, oriented at some angle to the overall layer packing for the whole molecule. This sublattice is usually called the “methylene subcell” (Abrahamsson et al., 1978). The subcell concept was originally devised by Vand and Bell (1951) to solve the x-ray crystal structure of a triglyceride. The identification of subcells is useful because there are only a few of them, with three or four being most commonly expressed in the polymethylene lattices found in lipid crystal structures.