title: Helical structure formation between complementary oligonucleotides. Minimum chain length required for the template-directed synthesis of oligonucleotides.
abstract: Helix formation between various combinations of 3'-5' linked oligoribouridylates and oligoriboadenylates from dimer to dodecamer has been studied to gain information on the chain-length requirement for the template-directed condensation of oligoribonucleotides. We have measured the helix formation under high oligoribonucleotide concentration in the presence of magnesium ion at 0-50 degrees C by UV or CD, as many model processes of oligoribonucleotides replication have been carried out under such conditions. Adenylic acid, (pA), diadenylic acid, (pA)2, or triadenylic acid, (pA)3, forms a helix with poly(U) or oligo(U) with a chain length of more than eight. On the other hand, neither uridylic acid, (pU), nor diuridylic acid. (pU)2, can form a helix with oligo(A) or poly(A). Triuridylic acid, (pU)3, or the longer oligo(U) forms a helix with oligo(A) with a chain length of over six. The results suggest that a trimer is the minimum unit as an incorporating nucleotide for conducting any set of nonenzymatic template-directed synthesis, A --> U and U --> A, as the nonenzymatic template-directed condensation of oligoribonucleotides correlates well with the results of helix formation of complementary oligoribonucleotides. We have further found the partial helix formation between 2'-5' linked decauridylate, (pU)10, and pA or 2'-5' linked (pA)2 at 0 degrees C, which indicates the possibility of the template activity of long 2'-5' linked oligonucleotides for the nonenzymatic oligonucleotide synthesis.
authors.affiliation: Department of Chemistry, Gunma University, Kiryu, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Sawai
authors.forename: S
authors.initials: S
authors.lastname: Totuka
authors.forename: K
authors.initials: K
authors.lastname: Yamamoto
mesh_terms: D019418:Evolution, Chemical; D019143:Evolution, Molecular; D006358:Hot Temperature; D008274:Magnesium; D009841:Oligonucleotides / Q000138:chemical synthesis*; D009843:Oligoribonucleotides / Q000737:chemistry*; D012313:RNA / Q000138:chemical synthesis; D013698:Templates, Genetic; D014466:Ultraviolet Rays
chemical_list: D009841:Oligonucleotides; D009843:Oligoribonucleotides; D012313:RNA; D008274:Magnesium