THE INFLUENCE OF UREA ON G-QUADRUPLEX AND i-MOTIF STRUCTURES IN COMPLEMENTARY DNA SEQUENCES

TLDR: The methods of circular dichroism and UV/Vis spectrophotometry were used to study the influence of urea on the structural transitions i-motif unfolded single strand in cytosine-rich d[3-(CCCAAT)3CCC-5)] region of telomeric DNA and G-quadruplex unfolded single stranded strand d[5-A(GGGTTA)3GGG-3] (Tel22G).

Abstract: 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 unfolded single strand in cytosine-rich d[3-(CCCAAT)3CCC-5)] region of telomeric DNA (Tel22C) and G-quadruplex unfolded single strand in complementary guanine-rich strand d[5-A(GGGTTA)3GGG-3] (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-motif has already been completed).