Primitive nucleobases @ sodium 2-Ketooctanoate vesicles with high salt resistance

Proto-single chain amphiphiles (P-SCAs) vesicles are considered to be a plausible model of the protocell on early Earth due to their primordial relevancy and membrane structure. In this work, we selected P-SCAs sodium 2-ketooctanate (SKO) and proto-nucleobases (PNBs, including cytosine, uracil, adenine, and guanine) as the building constituents of the vesicles. The PNB molecules incorporate into SKO bilayers to form PNB@SKO vesicles with a binding rate of 7% − 12%. The interactions between them increase the solubility of PNB in water obviously while decreasing the critical vesicle concentration of SKO. The morphology, size, and membrane thickness of SKO PRB@SKO vesicles are not affected by the PNB combination significantly. A binding mechanism is proposed based on the results of Fourier transform infrared and small angle X-ray scattering. The rigid planar PNB molecules orientate via hydrogen bonding in the tilted bilayers of SKO, without excessive disruption to the membrane structure. Both ribozyme-catalyzed and non-enzymatic RNA copying reactions require high concentrations of divalent ions, fortunately, the salt resistance of these PNB@SKO vesicles is surprisingly remarkable, one or two orders of magnitude greater than the other typical P-SCAs vesicles systems. We expect that this primitively relevant vesicle system can exert its potential advantages in the proto-membrane mimicry of the origin of life.