Silica-Carbonate of Ba(II) and Fe²⁺/Fe³⁺ Complex as Study Models to Understand Prebiotic Chemistry

Abstract

The Precambrian era is called the first stage of the Earth history and is considered the longest stage in the geological time scale. Despite its duration, several of its environmental and chemical characteristics are still being studied. It is an era of special relevance not only for its duration but also because it is when a set of conditions gave rise to the first organism. This pioneer organism has been proposed to have been formed by a mineral and an organic part. A chemical element suggested to have been part of the structure of this cell is iron. However, what special characteristic does iron have with respect to other chemical elements to be proposed as part of this first cell? To answer this and other questions, it is indispensable to have a model that will allow extrapolating the first chemical structures of the pioneer organism formed in the Precambrian. In this context, for several decades, in vitro structures chemically formed by silica-carbonates have been synthetized, called biomorphs, because they could emulate living organisms and might resemble primitive organisms. It has been inferred that because biomorphs form structures with characteristic morphologies, they could resemble the microfossils found in the cherts of the Precambrian. Aiming at providing some insight on how iron contributed to the formation of the chemical structures of the primitive organism, we evaluated how iron contributes to the morphology and chemical–crystalline structure during the synthesis of these compounds under different conditions found in the primitive atmosphere. Experimentally, synthesis of biomorphs was performed at four different atmospheric conditions including UV light, nonionizing microwave radiation (NIR-mw), water steam (WS), and CO 2 in the presence of Fe 2+ , Fe 3+ , and Fe 2+ /Fe 3+ , obtaining 48 different conditions. The produced biomorphs were observed under scanning electron microscopy (SEM). Afterward, their chemical composition and crystalline structure were analyzed through Raman and IR spectroscopy.

New Insights on the Origin of Life: The Role of Silico-Carbonates of Ba (II) to Preserve DNA against Highly Intense UV Radiation

“…arvense presented hollow structures with flower and leaf morphology (Figure C). The morphologies of biomorphs in all assessed conditions correspond to the characteristic morphologies previously reported. − These are interesting results as they reveal that the morphology of the biomorphs was not modified by the UV light; thus, this could be considered as the first evidence that, at least in terms of morphology, biomorphs are not modified by the intense radiation to which they were exposed for 7 consecutive days. The origin of life is tied to solar light, and, in the Precambrian, without an ozone layer, the UV rays passed directly to the terrestrial atmosphere.…”

“…albicans, this is a eukaryote microorganism found in diverse habitats, from water and soil to the human host . Once biomorphs were synthesized in the different conditions, they were exposed for 7 consecutive days to UV light in two different media: air and the other was the SS-Fe (3+) (called thereafter SS-Fe only) solution, to emulate the two conditions co-existing in the Precambrian − and to evaluate whether one of the two media was most probable for the preservation of biomolecules. In this way, it would be possible to support our proposed hypothesis regarding that the biomorphs might have been one of the first inorganic structures in which protomolecules became isolated and protected from the adverse conditions prevailing in that era.…”

“…Once the microphotographs of the biomorphs had been obtained through SEM, we determined the chemical composition and the crystalline structure of the barium biomorphs through Raman spectroscopy. This method was chosen because it is a high-resolution method that provides, within seconds, both chemical and structural information of any compound, allowing the identification of the presented polymorphs. , In the Raman spectrum corresponding to the control sample exposed to UV in the SS-Fe, peaks at 139, 152, 225, and 1058 cm –1 were identified (Table ). For the control in air, peaks at 138, 154, 224, and 1059 cm –1 were found (Table ).…”

“…Our results support the idea that biomorphs are possibly one of the mineral inorganic structures that participated in the origin of life by isolating and protecting the first molecules and biomolecules of the different environments or habitats found in the primigenial era. This is supported also because biomorphs are mineral crystalline structures that present diverse biological morphologies; − biomorphs present similitude with some Apex fossils; biomorphs are proposed as one of the inorganic structures in which biomolecules formed in the Precambrian were concentrated, aligned, polymerized, and protected from the prevailing conditions in the primitive era; and it has been inferred that biomorphs are possibly the cherts of the Precambrian that were kept invisible until their discovery . These characteristics fulfilled by biomorphs led me to propose them as one of the first inorganic structures where biomolecules were isolated from the environment in the Precambrian and as the gap between the Precambrian and our current era.…”

Protection of the DNA from Selected Species of Five Kingdoms in Nature by Ba(II), Sr(II), and Ca(II) Silica–Carbonates: Implications about Biogenicity and Evolving from Prebiotic Chemistry to Biological Chemistry

“…These inorganic compounds emulate the curved, helicoidal, or conic morphologies of some organisms like radiolarians, diatoms, worms, spirals, leaves, and flowers, among others. Included in them are the silica–carbonates of Ba­(II), Ca­(II), and Sr­(II) usually called silica biomorphs. − This characteristic is especially relevant because they are structures with diverse biological morphologies that are not formed by cells, but by nanocrystals, and some of these morphologies resemble some of the microfossils found in the cherts of the Precambrian era. , Even though biomorphs are unknown structures in the geological registry, their similarity with biological forms, including some Apex fossils, could lead to considering them as the first “inorganic scaffold” where the first biomolecules concentrated, conserved, aligned, and duplicated to give rise to the pioneer cell. However, it has not been documented whether biomorphs could have been the primary structures that conserved biomolecules in the Precambrian era.…”