THE INFLUENCE OF UREA ON G-QUADRUPLEX AND i-MOTIF STRUCTURES IN COMPLEMENTARY DNA SEQUENCES
DOI:
https://doi.org/10.46991/PYSU:A/2020.54.2.115Keywords:
telomeric DNA, G-quadruplex, i-motif, urea, circular dichroism, UV/Vis spectrophotometryAbstract
In the present study, the methods of circular dichroism and UV/Vis spectrophotometry were used to study the influence of urea on the structural transitions i-motif $\leftrightarrows$ unfolded single strand in cytosine-rich ${\text{d[3}^{\prime}\text{-(CCCAAT)}_{3}\text{CCC-5)}^{\prime}]}$ region of telomeric DNA (Tel22C) and G-quadruplex $\leftrightarrows$ unfolded single strand in complementary guanine-rich strand ${\text{d[5}^{\prime}\text{-A(GGGTTA)}_{3}\text{GGG-3}^{\prime}]}$ (Tel22G) at pH 5.5 and 400 mM Na+. Under these conditions, Tel22C and Tel22G were found to form stable i-motif and G-quadruplex structures. It has been shown that urea (0-8 M) destabilizes the i-motif and G-quadruplex structures, but unlike thermal denaturation, it does not destroy the structures completely. The melting processes of G-quadruplex and i-motif are separated in the temperature scale (at any concentration of urea, the melting of the G-quadruplex starts at temperatures where the melting of the i-motifs has already been completed).
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