西亚试剂：Folding Equilibrium Constants of Telomere G-Quadruplexes in

Folding Equilibrium Constants of Telomere G-Quadruplexes in Free State or Associated with Proteins Determined by Isothermal Differential Hybridization

Quan Wang, Li Ma, Yu-hua Hao, and Zheng Tan*

Guanine rich (G-rich) nucleic acids form G-quadruplex structures that are implicated in many biological processes, pharmaceutical applications, and molecular machinery. The folding equilibrium constant (KF) of the G-quadruplex not only determines its stability and competition against duplex formation in genomic DNA but also defines its recognition by proteins and drugs and technical specifications. The KF is most conveniently derived from thermal melting analysis that has so far yielded extremely diversified results for the human telomere G-quadruplex. Melting analysis cannot be used for nucleic acids associated with proteins, thus has difficulty to study how protein association affects the folding equilibrium of G-quadruplex structure. In this work, we established an isothermal differential hybridization (IDH) method that is able to determine the KF of G-quadruplex, either alone or associated with proteins. Using this method, we studied the folding equilibrium of the core sequence G3(T2AG3)3 from vertebrate telomere in K+ and Na+ solutions and how it is affected by proteins associated at its adjacent regions. Our results show that the KF obtained for the free G-quadruplex is within 1 order of magnitude of most of those obtained by melting analysis and protein binding beside a G-quadruplex can dramatically destabilize the G-quadruplex