Fiksel, G. | bioRxiv Science

bioRxiv2025

Nighttime and daytime scenarios in Darwinian liposome evolution under UV-driven natural selection

Previously, we presented a hypothesis on Darwinian evolution of liposomes that relies solely on natural and ever-present phenomena: the day-night cycle of solar UV radiation, gravity, and the release of amphiphiles in aqueous media. We demonstrated the protective ability of certain ferric salts typical for Archean waters, notably iron trichloride and ferric ammonium citrate, against liposome destruction by short-wavelength UV by shielding the liposomes with cuvettes filled with ferric salts. In the present study, we investigate the interaction with UV for the liposomes with negative buoyancy that sink naturally in ferric salt solutions. We examined two scenarios: 1) liposomes submerged in the FeCl3 solution prior to the UV exposure, a scenario mimicking the nighttime submergence; and 2) submergence under UV exposure, a relevant daytime scenario. We use custom-designed micron-sized, negative-buoyant (heavy), UV-sensitive liposomes. The results showed that for the nighttime scenario, all liposomes were free from UV damage when given sufficient time to submerge in a protective ferric salt solution. Given that larger and heavier liposomes submerge faster, we hypothesize that simple sugar molecules, such as ribose, which is a vital component of RNA, can serve as the proposed heavy molecules in Origin of Life scenarios. Conversely, the daytime scenario results indicate that liposomes slowly submerging under UV exposure sustain some damage. The results of these experiments, which aim to simulate natural events, showed that negative buoyancy and short-wavelength UV radiation could serve as natural drivers in the novel scenario of Darwinian liposome evolution.

evolutionary biology↗

bioRxiv2024

Solutions of ferrous salts protect liposomes from UV damage: implications for Life Origin

Previously, we presented a hypothesis on the Darwinian evolution of liposomes that relies only on natural and ever-present phenomena: solar UV radiation, day/night cycle, gravity, and the formation of amphiphiles, e.g., fatty acids and phospholipids, in aqueous media. The hypothesis further suggests that liposomes, formed at the air-water interface, will be inevitably destroyed by Sun UV unless they are submerged and shielded by primordial water. The hypothesis makes two testable predictions. First, certain ingredients of the Archean waters, e.g., ferric salts, can completely attenuate UV; and second, such ferric salts solution can protect the submerged liposomes from the solar UV damage. In our previous experiments (Subbotin and Fiksel 2023a), we tested the prediction of UV attenuation by ferrous salt solutions. We have demonstrated that out of several tested iron salt solutions, two salts demonstrated very strong UV attenuation: at a concentration of 2.5 g/L of (NH4)5[Fe(C6H4O7)2] and FeCl3, the UV intensity drops by a factor of 1000 at a submersion depth of 7.4 mm and 6.3 mm, respectively. In the present study, we tested the second prediction: we investigated whether the above ferrous salt solutions can protect UV-sensitive liposomes from UV damage. The results demonstrated that 10 mm of solutions, the ferric ammonium citrate or iron trichoride, completely protected UV-sensitive liposomes from UV damage. These results supplement and reinforce the proposed hypothesis.

systems biology↗