Stable Vesicles Composed of Monocarboxylic or Dicarboxylic Fatty Acids and Trimethylammonium Amphiphiles

Abstract

The self-assembly of cationic and anionic amphiphile mixtures into vesicles in aqueous media was studied using two different systems: (i) decanoic acid and trimethyldecylammonium bromide and (ii) hexadecanedioic acid (a simple bola-amphiphile) and trimethyldecylammonium bromide. The resulting vesicles with varying amphiphile ratios were characterized using parameters such as the critical vesicle concentration, pH sensitivity, and encapsulation efficiency. We also produced and observed giant vesicles from these mixtures using the electroformation method and confocal microscopy. The mixed catanionic vesicles were shown to be more stable than those formed by pure fatty acids. Those containing bola-amphiphile even showed the encapsulation of a small hydrophilic solute (8-hydroxypyrene-1,3,6-trisulfonic-acid), suggesting a denser packing of the amphiphiles. Compression and kinetics analysis of monolayers composed of these amphiphiles mixtures at the air/water interface suggests that the stabilization of the structures can be attributed to two main interactions between headgroups, predominantly the formation of hydrogen bonds between protonated and deprotonated acids and the additional electrostatic interactions between ammonium and acid headgroups.

Self-Assembly of Phosphate Amphiphiles in Mixtures of Prebiotically Plausible Surfactants

“…The balance between these three interactions or their actual contribution to the structure stabilization is a complex issue, as can be seen in previous investigations of mixed fatty acid membranes with GMD or DTAB (Maurer et al, 2009;Caschera et al, 2011).…”

“…This DTAB behavior in mixed membranes is not surprising, as even in membranes that require its presence to form, for example, hexadecanedioic acid/DTAB (Caschera et al, 2011), DTAB did not present a strong co-surfactant character, as it tended to self-assemble preferentially in micelles. Alternatively, the lack of dissociation of DTAB into its ion constituents (DTA + and Br -), which may be as low as 26% (Bales and Zana, 2002), could have significantly reduced the amount of positive charge available in the bilayer, thereby preventing the stabilization of the phosphate amphiphile in a bilayer structure.…”

The Encapsulation of Cell-free Transcription and Translation Machinery in Vesicles for the Construction of Cellular Mimics

“…The reconstitution of transcription-translation machinery from fully defined components 9 inside of vesicles 28 was particularly significant in facilitating later efforts in constructing environmentally responsive artificial cells17,18. Similarly, artificial cell studies have been used to probe evolutionary processes 4,29,30 , the mechanistic details of RNA and protein synthesis 22,31 , the influences of metabolic load32,33, and the assembly of viral particles 34 . Importantly, enough knowledge now exists that basic cellular function can be reconstituted inside of vesicles in the laboratory following these previous reports and the protocols described herein.…”

Physico-chemical interactions between compartment-forming lipids and other prebiotically relevant biomolecules

“…The authors explained these results by the fact that the neutral (protonated) fatty acids and positively charged alkyl ammonium molecules do not undergo electrostatic association with cations at low pH, whereas at high pH the EPOV 2012 05001-p. 5 negative charges of the fatty acids bind divalent cations, thereby causing aggregation to form calcium or magnesium soaps. This hypothesis was studied more thoroughly by Caschera et al [22] who analyzed monolayers composed of fatty acids, fatty dioic acids, and alkyl amines. They concluded that the stabilization can be attributed to the formation of hydrogen bonds between protonated and deprotonated acids and the electrostatic interactions between the ammonium and carboxylate head groups.…”