Absorption of Pyrimidines, Purines, and Nucleosides by Li-, Na-, Mg-, and Ca-Montmorillonite (Clay-Organic Studies XII)

Abstract

Abstract-The absorption of biologically important purines, pyrimidines, and nucleosides by Li-, N a-, Mg-, and Ca-montmorillonite has been studied in aqueous solutions over a range of pH values 2-12. The initial organic concentrations were about 1 m.molar. The ratio clay to organic compounds was such that only up to 25 per cent of the exchange capacity could be saturated by organic cations, but, depending on conditions, up to 100 per cent of the available organic material was absorbed. Of the nineteen compounds studied, only thymine, uracil, and their nucleosides were not absorbed under the experimental conditions. Absorption occurs primarily as a cation exchange reaction under acid conditions and varies with the basicity of the compounds, their aromatic or non-aromatic character, and the possible extent of their van der Waals interaction with the silicate layers. Nucleosides generally are less strongly absorbed than their purines or pyrimidines because their non-planar structure permits less van der Waals interaction; their absorption is influenced by the differences in swelling behavior of montmorillonite with mono-and divalent cations.

Adsorption of Quinoline from Aqueous Solutions by Some Clays and Oxides

“…In the first, the decrease in adsorption as the pH decreases is due to a competition between protons and cation quinoline for balancing the surface charges. This explanation has been already given by Lailach et al (1968) and Thompson and Brindley (1969) for organic cation adsorption on clays. However, this explanation does not account for the observation that between pH 6 and 2, an amount of quinoline twice the CEC of the clay is desorbed.…”

Absorption of Pyrimidines, Purines, and Nucleosides by Co-, Ni-, Cu-, and Fe(III)-Montmorillonite (Clay-Organic Studies XIII)

“…Fe(llI)-montmorillonite behaves quite differently from the other montmorillonites studied. With purines and pyrimidines, there is strong absorption from pH 3 to pH 7-8; with the nucleosides, the absorption varies considerably with the compounds considered decreasing in the order adenosine > cytidine ~> guanosine ~> inosine.INTRODUCTION THE EXPERIMENTS reported here extend those previously described on the absorption of pyrimidines, purines, and nucleosides by Li-, Na-, Mg-, and Ca-montmorillonite (Clay-Organic Studies, Part XII, Lailach et al, 1968) to montmorillonites saturated with the transition metal cations, Co, Ni, Cu, and Fe(llI). The previous work will be referred to as Part XII.…”

“…INTRODUCTION THE EXPERIMENTS reported here extend those previously described on the absorption of pyrimidines, purines, and nucleosides by Li-, Na-, Mg-, and Ca-montmorillonite (Clay-Organic Studies, Part XII, Lailach et al, 1968) to montmorillonites saturated with the transition metal cations, Co, Ni, Cu, and Fe(llI). The previous work will be referred to as Part XII.…”

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

“…It is not known whether considerable interlayer acidity can be developed in the Ca-montmorillonite particles. Basal spacings of ~12.5A were observed by Lailach et al (1968) in montmorillonite saturated by several organic molecules and suspended in water. Interlayer acidity in these aggregates is probably considerable.…”