Aggregation behavior of short-chained archaeal phospholipid analogs: Contribution of methyl branches to lipid hydrophobicity and membrane formability

Abstract The aggregation behavior of short-chained archaeal phospholipid analogs (DCn+mPCs, (n, m) = (4, 1) and (8, 2), n: number of carbon atoms in the single main chain; m: number of methyl branches in one chain. PC denotes phosphatidylcholine) in water was investigated as a function of the hydrophobic chain length and the glycerol-linkage type (ester or ether bond), using fluorescent probe method, polarized light microscopy and XRD. DC8+2PCs yielded myelin-figures in their dilute solutions at 25 °C, indicating that they tend to form vesicular structures rather than micelles. In contrast, DC4+1PCs lacked to form myelin-figures in their dilute solutions, being similar to short straight-chained PC surfactants, e.g., dioctanoyl-PC. The critical micelle concentrations of DCn+mPCs could be well interpreted on the basis of the total water contact surface area of the lipid hydrophobic chains, while the glycerol-linkage type seemed to have only a minor effect on the aggregation behavior of lipids.