Oligomerization of uridine phosphorimidazolides on montmorillonite: a model for the prebiotic synthesis of RNA on minerals.
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.
Ding
P Z
PZ
Department of Chemistry, Rensselaer Polytechnic Institute, Troy, New York 12180-3590, USA.
Kawamura
K
K
Ferris
J P
JP
D000596:Amino Acids / Q000494:pharmacology; D001546:Bentonite / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D011756:Diphosphates / Q000494:pharmacology; D009841:Oligonucleotides / Q000037:antagonists & inhibitors / Q000138:chemical synthesis*; D012313:RNA / Q000138:chemical synthesis*; D014542:Uridine Monophosphate / Q000031:analogs & derivatives* / Q000737:chemistry
D000596:Amino Acids; D011756:Diphosphates; D009841:Oligonucleotides; D001546:Bentonite; C066970:uridine 5'-(phosphoimidazolate); D012313:RNA; D014542:Uridine Monophosphate