Syntheses and aggregation properties of new squalene receptors bearing open chain ligands

New squalene receptors bearing open-chain polyether ligands (SQ-diEG, SQ-triEG, SQ-tetraEG) were synthesised. The stoichiometries and association constants (K_a) for the interactions between these squalene receptors and representative alkaline earth metal ions (Mg²⁺, Ca²⁺, and Ba²⁺) were determined in solution. Fluorescence spectral studies revealed that the squalene receptors self-associate with critical vesicle concentrations at 25 °C of 2.2 × 10⁻⁵ M for SQ-diEG, 2.3 × 10⁻⁵ M for SQ-triEG, and 2.5 × 10⁻⁵ M for SQ-tetraEG. The self-assembly behaviour was probed using laser diffraction particle size-based analyses and scanning electron microscopy. A decrease in the SQ-tetraEG vesicle size was readily induced by the addition of alkaline earth metal ions, confirmed by cryogenic transmission electron microscopy.