Oligomerization of uridine phosphorimidazolides on montmorillonite: A model for the prebiotic synthesis of rna on minerals
Abstract
The 5'-phosphorimidazolide of uridine reacts on Na+-montmorillonite 22A in aqueous solution to give oligomers as long as 7 mers. The maximum chain length increases to 9 mers and the overall oligomer yield increases when 9:1 ImpU, A5' ppA mixtures react under the same conditions. The oligomer yield and maximum chain length decreases with the structure of the added pyrophosphate in the order A5' ppA>A5' ppU>U5' ppU. Structure analysis of individual oligomer fractions was performed by selective enzymatic hydrolyses followed by HPLC analysis of the products. The regioselectivity for 3',5'-bond formation is 80 90% in the 9:1 ImpU, A5' ppA reaction, a percentage comparable to that observed in the 9:1 ImpA, A5' ppA reaction. Oligomerization of ImpU is inhibited by addition of dA5' ppdA, and MeppA. No oligomers containing A5' ppU were products of the 9:1 ImpU, A5' ppA reaction, a finding consistent with the simple addition of the ImpU to the A5' ppA and not the rearrangement of an ImpU-A5' ppA adduct. Concentrations of lysine or arginine which were close to that of the ImpU did not inhibit oligomer formation. Treatment of Na+-montmorillonite with 1 M arginine yielded arginine-montmorillonite, an amino acid-mineral adduct which did not catalyze ImpU oligomerization. Neither the 4 9 mers formed in the 9:1 ImpU, A5' ppA reaction nor the 4 9 mers formed by the base hydrolysis of poly(U) served as templates for the formation of oligo(A)s.
- Publication:
-
Origins of Life and Evolution of the Biosphere
- Pub Date:
- April 1996
- DOI:
- 10.1007/BF01809853
- Bibcode:
- 1996OLEB...26..151D