Biochemical evolution. I. Polymerization on internal, organophilic silica surfaces of dealuminated zeolites and feldspars

Abstract

Catalysis at mineral surfaces might generate replicating biopolymers from simple chemicals supplied by meteorites, volcanic gases, and photochemical gas reactions. Many ideas are implausible in detail because the proposed mineral surfaces strongly prefer water and other ionic species to organic ones. The molecular sieve silicalite (Union Carbide; ‫؍‬ Al-free Mobil ZSM-5 zeolite) has a three-dimensional, 10-ring channel system whose electrically neutral Si-O surface strongly adsorbs organic species over water. Three -O-Si tetrahedral bonds lie in the surface, and the fourth Si-O points inwards. In contrast, the outward Si-OH of simple quartz and feldspar crystals generates their ionic organophobicity. The ZSM-5-type zeolite mutinaite occurs in Antarctica with boggsite and tschernichite (Al-analog of Mobil Beta). Archean mutinaite might have become de-aluminated toward silicalite during hot/cold/wet/dry cycles. Catalytic activity of silicalite increases linearly with Al-OH substitution for Si, and Al atoms tend to avoid each other. Adjacent organophilic and catalytic Al-OH regions in nanometer channels might have scavenged organic species for catalytic assembly into specific polymers protected from prompt photochemical destruction. Polymer migration along weathered silicic surfaces of micrometer-wide channels of feldspars might have led to assembly of replicating catalytic biomolecules and perhaps primitive cellular organisms. Silica-rich volcanic glasses should have been abundant on the early Earth, ready for crystallization into zeolites and feldspars, as in present continental basins. Abundant chert from weakly metamorphosed Archaean rocks might retain microscopic clues to the proposed mineral adsorbent/catalysts. Other framework silicas are possible, including ones with laevo/dextro one-dimensional channels. Organic molecules, transition-metal ions, and P occur inside modern feldspars.

Reactions and Surface Interactions of Saccharides in Cement Slurries

“…Such adsorption of organic species at tricalcium silicate surfaces is consistent with the delayed formation of calcium silicate hydrates in both white Portland and gray oilwell cements hydrated in the presence of small quantities (≤1% bwoc) of these different saccharides. However, as outlined by Cheung et al, 12 whether hydration inhibition is due predominantly to the adsorption (or precipitation) of organic species onto initially nonhydrated C 3 S surfaces versus that onto hydrated products (e.g., Ca(OH) 2 or calcium silicate hydrates) has remained elusive and unresolved. In the former case, organic species may adsorb on nonhydrated tricalcium silicate species in cements to slow the dissolution of ions (e.g., H 3 SiO 4 − or Ca 2+ ) from particle surfaces, thereby delaying the subsequent precipitation of hydration products.…”

“…Figure 6b shows broad (3 ppm fwhm) and very weak 29 Si signal intensity centered at −75 ppm in the region that corresponds to monomeric Q 0 29 Si species that are in close molecular proximity (<1 nm) to hydroxyl groups or adsorbed water. Such Q 0 silicate species are most likely associated with partially hydroxylated C 3 S sites (e.g., SiO(OH) 3 − or SiO 2 (OH) 2 2− ) on cement particle surfaces and may include small quantities of silicate anions precipitated from the cement slurry solution during the freeze-drying of the sample. Importantly, no Q 1 or Q 2 species associated with hydrated silicate species (e.g., C−S−H) are detected (≤0.2 wt %), even after prolonged signal averaging.…”

Impact of mineral micropores on transport and fate of organic contaminants: A review

“…Molecules sorbed in the micropores are also shielded from sunlight and thus protected from photolytic degradation. It has been hypothesized that nanometer to sub-micrometer pores with silica-rich surfaces in various materials from the zeolite, feldspar, and silica mineral groups played a key role in capturing of organic species from aqueous solutions for catalytic assembly into complex biomolecules (such as ribonucleic acids), and protected them from hydrolytic or photochemical destruction, leading to the start of biochemical evolution on Earth (Parsons et al, 1998;Smith, 1998;Smith et al, 1999).…”

The Origin of Life: Chemical Evolution of a Metabolic System in a Mineral Honeycomb?

“…Smith and his coworkers have identified feldspar as the possible honeycomb for the very first stages of biochemical evolution (Parsons et al 1998;Smith 1998;Smith et al 1999). Feldspar is by far the most abundant group of minerals in the earth's crust, forming about 60% of terrestrial rocks crystallize from magma in both intrusive and extrusive igneous rocks; K-feldspars must have been common on the surface of prebiotic Earth *3.8 Ga.…”