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Effect of Mg 2+ Ions on the Stability of PolyA/2PolyU Three‐Stranded Helices in Aqueous Solutions
Author(s) -
Sorokin Victor A.,
Valeev Vladimir A.,
Gladchenko Galina O.,
Degtyar Marina V.,
Andrus Elena A.,
Blagoi Yuri P.,
Karachevtsev Victor A.
Publication year - 2002
Publication title -
macromolecular bioscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.924
H-Index - 105
eISSN - 1616-5195
pISSN - 1616-5187
DOI - 10.1002/1616-5195(20020501)2:4<155::aid-mabi155>3.0.co;2-z
Subject(s) - chemistry , aqueous solution , crystallography , ion , helix (gastropod) , phase transition , ionic strength , analytical chemistry (journal) , thermodynamics , chromatography , ecology , physics , organic chemistry , snail , biology
The influence of Mg 2+ , Na + and temperature on the conformational state of three‐stranded helical polyA/2polyU (A2U) has been studied by the thermal denaturation method. At Na + concentrations of 0.01–0.1 M , on heating the transition A2U→AU+U (the 3→2 transition) and then AU→A+U transition (the 2→1 transition) are observed. (AU is double helix polyA/polyU; A and U are single‐stranded polyA and polyU, respectively.) With 0.01 M and 0.03 M Na + these transitions occur at Mg 2+ concentrations within (0 ÷ 0.003) M . At these ionic concentrations, there is a narrow temperature region (3 ÷ 5°C) at which double‐helical AU formed by the 3→2 transition is resistant to heating. In 0.1 M Na + , a rise in the Mg 2+ concentration leads to a continuous decrease in the temperature range of this region, and above a critical concentration of Mg 2+ (ca. 3.6×10 –5 M ) cr there is only one transition (the 3→1 transition) instead of the successive transitions 3→2→1. The constants of Mg 2+ ion association with polyU, polyA and A2U were calculated using equilibrium binding theory. The data obtained helped explain the reasons for the different phase diagrams for A2U + Mg 2+ complexes in solution at high and low Na + concentrations.