Kinetically governed polymorphism of d(G₄T₄G₃) quadruplexes in K+ solutions.
It has been generally recognized that understanding the molecular basis of some important cellular processes is hampered by the lack of knowledge of forces that drive spontaneous formation/disruption of G-quadruplex structures in guanine-rich DNA sequences. According to numerous biophysical and structural studies G-quadruplexes may occur in the presence of K(+) and Na(+) ions as polymorphic structures formed in kinetically governed processes. The reported kinetic models suggested to describe this polymorphism should be considered inappropriate since, as a rule, they include bimolecular single-step associations characterized by negative activation energies. In contrast, our approach in studying polymorphic behavior of G-quadruplexes is based on model mechanisms that involve only elementary folding/unfolding transitions and structural conversion steps that are characterized by positive activation energies. Here, we are investigating a complex polymorphism of d(G(4)T(4)G(3)) quadruplexes in K(+) solutions. On the basis of DSC, circular dichroism and UV spectroscopy and polyacrylamide gel electrophoresis experiments we propose a kinetic model that successfully describes the observed thermally induced conformational transitions of d(G(4)T(4)G(3)) quadruplexes in terms of single-step reactions that involve besides single strands also one tetramolecular and three bimolecular quadruplex structures.
Faculty of Chemistry and Chemical Technology, Physical Chemistry, University of Ljubljana, Askerceva, Slovenia.
Iztok
I
Prislan
Jurij
J
Lah
Matija
M
Milanic
Gorazd
G
Vesnaver
D054856:G-Quadruplexes; D006147:Guanine / Q000737:chemistry; D007700:Kinetics; D008956:Models, Chemical; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D011188:Potassium / Q000737:chemistry*; D013696:Temperature; D013941:Thymine / Q000737:chemistry
D009838:Oligodeoxyribonucleotides; D006147:Guanine; D013941:Thymine; D011188:Potassium