Simultaneous existence of different environments in aqueous clay systems and its possible role in prebiotic synthesis

Abstract

The formation of packets of parallel oriented platelets and separating distances of several angstrom units in montmorillonite-water systems produces an intrinsic inhomogeneity with respect to the proton donating power of internal and external zones. Stable packets can be induced by both inorganic and organic molecules or ions, in suspensions or in drying-out systems. The coexistence of zones with different proton donating power was demonstrated by the pH-sensitive color reaction of benzidine, where stable packets of montmorillonite platelets were formed by the use of either paraquat or diquat. The close proximity of the two types of zones, which can be of the order of several angstroms, produces the conditions which were defined by Katchalsky as essential for the polymerization of amino acids. Since these enviromental conditions are quite common in nature, both at present and in prebiotic times, it is proposed that the inhomogeneity of clay-water systems with respect to proton donating power should be taken into account in both theoretical and experimental efforts to demonstrate the catalytic activity of clays in prebiotic synthesis.

Polymerization of alanine in the presence of a non-swelling montmorillonite

“…This latter factor is necessary for polymerization. We have used the non-swelling montmorillonite in order to supply these acid conditions, since in the interlayer space of the aggregates a considerably acidity is known to exist (Lahav, 1975). Thus another possibility for the inhibition of polymerization by the M-montmorillonite is an excess of acidity which might exist in this clay.…”

“…In these experiments Na-montmorillonite was used under experimental conditions which favored its swelling, due to the presence of Na + in the dilute solution. It was noted recently (Lahav, 1975) that under natural conditions an intrinsic heterogeneity can exist in clay-water systems where the conditions inside clay packets may be very different from those in the bulk solution, and that this heterogeneity may be important tO abiotic synthesis of organic molecules.…”

Mineral–organic interfacial processes: potential roles in the origins of life

“…Clay minerals have been favorite topics of study because they are significant components of soils (and thus are of interest for various agricultural funding sources); because they have extremely high specific surface areas (a gram of clay may have a surface area roughly equivalent to a tennis court, whereas a gram of coarse sand may have a surface area of a few cm 2 ); and clay minerals have ionic exchange sites, and are thus reminiscent of ion exchange resins. 57,[181][182][183] Organic adsorption to mineral surfaces may approximately be generalized based on functional group chemistry. Because ionic bonds are relatively strong, and many biochemicals contain ionizable functional groups, interactions between amines, phosphates or carboxylic acids are often the focus of adsorption studies.…”