Comparative Cryo-Electron Microscopy of Noncovalent N-Dodecanoyl- (d- and l-) serine Assemblies in Vitreous Toluene and Water

Abstract

Hot solutions (>80 °C) of N-dodecanoyl- (d- or l-) serine in toluene or water were cooled to room temperature to give gels and were then vitrified for cryo-TEM investigations. Electron micrographs showed multilamellar aggregates with a repetitive density profile of 33 Å as constituents of tubules and vesicles in toluene as well as of twisted ribbons and tubules in water. In water the aggregates were about 10 times longer than those in toluene (up to 10 μm), and platinum shadowing showed inverse twists for ribbons of d- and l-enantiomers. The racemate gave planar platelets in both solvents. It is concluded that the high dielectric constant of bulk water is needed to stabilize the high surface energy of the edges in thin helical ribbons. The trace amounts of water stabilizing the reverse-micellar structures in toluene, on the other hand, do not have an ordering effect on the headgroup arrangement. Curvature is caused by chirality of the monomers (“chiral bilayer effect”) and is effective in both environments.

Unique incorporation behavior of amino acid-type surfactant into phospholipid vesicle membrane

“…The low toxicity of amino acid-type surfactants has been confirmed by in vivo experiments [21,22]. In addition, there has been interest in N-acyl amino acid surfactants with respect to their chirality [23][24][25][26][27][28][29]. We clarified the chiral effect on the Krafft temperature of N-acyl amino acid surfactants systematically [28,29].…”

Physicochemical and toxicological properties of novel amino acid-based amphiphiles and their spontaneously formed catanionic vesicles

“…The stronger hydrophobicity of 12Lys12 also explains the large surface excess (9.3 mol m −2 ), indicating the affinity of the amphiphile to adsorb at the interface, thus efficiently lowering the surface tension. In addition, the existence of groups where intermolecular hydrogen bonding can occur, namely the N-H and C O groups, can further enhance the surface adsorption [24,[48][49][50]. For instance, comparing this surfactant with a bis(quaternary ammonium) gemini surfactant with four CH 2 spacer groups [46], it can be seen that the lysine derivative attains a much lower surface tension at the cmc (12-4-12: 39.8 mN m −1 ; 12Lys12: 27.1 mN m −1 ).…”

Recognition‐Induced Polymersomes: Structure and Mechanism of Formation

“…In recent years, researchers have performed FF-TEM in organic solvents; [22] however, to the best of our knowledge, this is the first account of freeze-fracture reported in chloroform. The micrographs in Figure 2 provide a definite confirmation of the vesicular morphology; however, the shadowing process obscured the quantitative determination of the vesicle membrane thickness.…”