Abstract
A series of D-erythro (2S, 3R) sphingomyelins (SMs) was synthesized by the acylation of D-erythro-sphingosylphosphorylcholine. In this synthesis, the acyl chain was varied in length from16 to 24 carbons at intervals of 2 carbons, in contrast to a fixed length of 18 carbons for the other sphingosine chain. For all the SM aqueous dispersions, reversible and reproducible thermal behavior was observed to show the gel-to-gel and the main gel-to-liquid crystal phase transition in heating DSC scan. The main transition enthalpy (∆HM) decreased with increasing the effective chain length (N) per molecule of lipid estimated on the basis of a model structure of SM molecule, which contrasted with the generally accepted phenomenon for lipid-water systems. The decrease in ∆HM with an increase in N was discussed from the viewpoint of the effect of the inequivalent chain segment in the acyl chain on the chain-chain van der Waals interaction energy that accounts for 2/3 of ∆HM.
https://ror.org/03whvgq80 
