Site-Specific Prebiotic Oligomerization Reactions of Glycine on the Surface of Hectorite

Abstract

Condensation reactions of the amino acid glycine on the surface of Cu(II)-exchanged hectorite are investigated using the technique of scanning force microscopy. Prebiotic conditions are simulated using alternate wetting and heating cycles. Concentration, immobilization, and subsequent polymerization resulting in glycine oligomers are seen to occur primarily at step edges or faults in the topmost layer. Condensation reactions also occur within tiny micropores or defects in the topmost layer. These reactions are facilitated by the availability of intergallery metal cations at the step edges or pores in the surface region.

Catalytic peptide hydrolysis by mineral surface: Implications for prebiotic chemistry

“…Clays and other fine grained sedimentary minerals may have provided the most likely surface for adsorption and condensation of amino acids owing to their high specific surface area (Ponnamperuma et al, 1982;Porter et al, 1998). Although many previous studies have examined the effects of minerals on peptide elongation in evaporative environments (Fox and Harada, 1958;Dose, 1983;Rode et al, 1999;Plankensteiner et al, 2004), as well in the presence of various condensing agents (Chang et al, 1969;Hawker and Oró , 1981;Hill et al, 1998;Liu and Orgel, 1998a,b;Leman et al, 2004), few studies have examined the catalytic effects of mineral surfaces on unactivated aqueous peptide oligomerization or degradation.…”

From the Prebiotic Synthesis of α-Amino Acids Towards a Primitive Translation Apparatus for the Synthesis of Peptides

“…Clay catalysis can also be combined with salt-induced peptide formation, leading to longer peptides [113]. The condensation also takes place with Cu(II) exchanged clays [114].…”

Interaction between glycine and Na-, Caand Cu-rich smectites

“…3) present considerable changes in the temperature range 200 4508C: (1) a large peak, relating to a small weight loss (~2.4% and 4.3% for beidellite and montmorillonite, respectively), occurs in Ca-exchanged smectites; (2) in Na-treated smectites, an endothermic peak at 2458C occurs in beidellite (weight loss: 4.4%), while two peaks (total weight loss: 7.8%) occur in montmorillonite, the first at 2708C (endothermic reaction) and the second at~3708C (exothermic reaction); (3) in Cu-rich beidellite a strong exothermic peak occurs at~3158C (weight loss: 9.3%) and at~3208C in Cu-rich montmorillonite (weight loss: 11.0%). In Na-and Cu-exchanged smectites, the presence of the exothermic reaction at T > 3008C might suggest the formation of glycil-glycine dymer (Porter et al, 1998;Zamaraev et al, 1997).…”