Self-complementary oligoribonucleotides: Effects of helix defects and guanylic acid-cytidylic acid base pairs

Olke C. Uhlenbeck*, Francis H. Martin, Paul doty

*Corresponding author for this work

Research output: Contribution to journalArticle

100 Scopus citations

Abstract

Oligonucleotides consisting of a sequence of adenylic acid and a sequence of uridylic acid separated by one eytidylic or guanylic acid or by a cytidilic-guanylic pair (C · G) have been synthesized and their associating properties studied. When G or C is inserted between the blocks the stability of the bimolecular, helical complex is reduced. C is the more destabilizing, reducing Tm from 10 to 17 deg. C equivalent to the removal of 2 adenylic-uridylic (A · U) pairs. Several observations suggest that, in contrast to C, the duplex rearranges to accommodate G opposite a U residue. Equimolar mixtures of oligomers differing only in that one contains C between the blocks and the other G are found to form bimolecular helices of enhanced stability. In a decamer the effect of one G · C pair replacing an A · U pair is to raise Tm by 8.5 deg. C. Double this effect is observed for the helical duplexes which are formed by (Ap)nCpG(pU)n. The stabilizing effect of G · C pairs is probably dependent on their location in the helix and nearest neighbors. In this case their effect on Tm is greater than that found for natural polymeric bihelical RNA, i.e. 0.9 deg. C per percentage increase in G + C rather than 0.75 deg. C. The greater enthalpy of formation of a G · C pair over an A · U pair can only be roughly estimated.

Original languageEnglish (US)
Pages (from-to)217-229
Number of pages13
JournalJournal of Molecular Biology
Volume57
Issue number2
DOIs
StatePublished - Apr 28 1971

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology

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