Interaction of poly(X) with poly(U): Alkali metal ion specificity suggests a four-stranded helix

✍ Scribed by Kunal B. Roy; J. Frazier; H. Todd Miles

• Publisher: Wiley (John Wiley & Sons)
• Year: 1983
• Tongue: English
• Weight: 669 KB
• Volume: 22
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360220903

✦ Synopsis

Interaction of poly(X) with poly(U) to form a regular, ordered structure has been investigated by uv, CD, and ir spectroscopy. The XU complex exhibits a marked dependence of T, on the nature of the alkali metal ion present in solution. Stability of the complex is surprisingly high and increases with ionization of X residues at N3. The ir evidence shows the U residues are present as the diketo form and X residues as the 6-keto-2-enolate anion and indicates that the X and U carbonyl groups are vibrationally coupled. A mixing curve exhibits a single minimum, a t 1:1, but we conclude that the actual combining ratio is twice this value and that the formula of the complex is X2U2. We propose a model based on a four-standard helix with size-specific alkali metal complexing to X and U carbonyl oxygens in the axial channel of the helix. This model and previously suggested two-stranded structures are evaluated in terms of the physical and chemical properties of the complex.