Thymine Adsorption onto Cation Exchanged Montmorillonite Clay: Role of Biogenic Divalent Metal Cations in Prebiotic Processes of Chemical Evolution.

The adsorption of thymine, a key pyrimidine base of deoxyribonucleic acid (DNA) on montmorillonite clay (Mnt) exchanged with metal ions (Mnt-M 2+ , M 2+  = Fe 2+ , Co 2+ , Cu 2+ , Ca 2+ , and Mg 2+ ) over a range of concentration (7.0 × 10 -5  M to 12.0 × 10 -5  M) and pH (4.0 - 9.0) at ambient temperature has been investigated in aqueous environment spectrophotometrically (UV, FTIR, XRD, SEM-EDX). The effectiveness of various adsorbents was determined in terms of percent (%) binding and Langmuir constants (K L and X m ) using Langmuir adsorption isotherm at their respective pH of maximum adsorption. Transition metal ions incorporated Mnt, particularly Fe 2+ have shown better adsorption ability than alkaline earth metal ions. The present study reveals the significant role of divalent metal cation exchanged Mnt clay in the chemical evolution of biomolecules of genetic continuity and self-replication which might have occurred through the adsorption of thymine on and between their silicate layers to protect and achieve biocompatibility.