title: Effect of Zn2+ and temperature on the conformational equilibrium of single-stranded polyA in neutral solutions.
abstract: Effect of Zn(2+) ions on the conformation of polyA in cacodilic buffer at pH 7 was investigated by differential UV spectroscopy (DUV) and by thermal denaturation. The shapes of the DUV spectra and melting curves suggest a transition of polyA into a more ordered "metallized", possibly double-helical conformation at Zn(2+) concentrations above 3×10(-5) M. A phase diagram of polyA complexes with Zn(2+) was constructed for the temperature range from 20 °C to 95 °C and Zn(2+) concentrations between 10(-5) M and 5×10(-4) M. It was found that the transition of a single strand into the "metallized" form is possible only if the length of the disordered single-stranded region becomes larger than a certain critical value, ranging between 98% and 78% as the metal concentration increases from 3×10(-5) to 5×10(-4) M.
authors: B.I. Verkin Institute for Low Temperature Physics and Engineering, National Academy of Sciences of Ukraine, 47 Lenin Avenue, Kharkov 61103, Ukraine. Electronic address: sorokin@ilt.kharkov.u.
authors: V A
authors: VA
authors: Sorokin
authors: V A
authors: VA
authors: Valeev
authors: E L
authors: EL
authors: Usenko
authors: V V
authors: VV
authors: Andrushchenko
mesh_terms: D002021:Buffers; D006863:Hydrogen-Ion Concentration; D007477:Ions; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D011061:Poly A / Q000737:chemistry*; D012996:Solutions; D013696:Temperature; D013816:Thermodynamics; D015032:Zinc / Q000737:chemistry*
chemical_list: D002021:Buffers; D007477:Ions; D012996:Solutions; D011061:Poly A; D015032:Zinc
keywords: Differential UV spectroscopy; Metal ions; Metallized form; Phase diagram; PolyA; Thermal denaturation