title: Direct measurement of sequential folding pathway and energy landscape of human telomeric G-quadruplex structures.
abstract: Single-stranded guanine-rich sequences fold into compact G-quadruplexes. Although G-triplexes have been proposed and demonstrated as intermediates in the folding of G-quadruplexes, there is still a debate on their folding pathways. In this work, we employed magnetic tweezers to investigate the folding kinetics of single human telomeric G-quadruplexes in 100 mM Na(+) buffer. The results are consistent with a model in which the G-triplex is an in-pathway intermediate in the folding of the G-quadruplex. By finely tuning the force exerted on the G-quadruplex, we observed reversible transitions from the G-quadruplex to the G-triplex as well as from the G-triplex to the unfolded coil when the force was increased from 26 to 39 pN. The energy landscape derived from the probability distribution shows clearly that the G-quadruplex goes through an intermediate when it is unfolded, and vice versa.
authors: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China. weili007@iphy.ac.cn
authors: Wei
authors: W
authors: Li
authors: Xi-Miao
authors: XM
authors: Hou
authors: Peng-Ye
authors: PY
authors: Wang
authors: Xu-Guang
authors: XG
authors: Xi
authors: Ming
authors: M
authors: Li
mesh_terms: D002021:Buffers; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry; D004574:Electromagnetic Fields; D004735:Energy Transfer; D054856:G-Quadruplexes; D006147:Guanine / Q000737:chemistry*; D006801:Humans; D007700:Kinetics; D009690:Nucleic Acid Conformation; D016615:Telomere / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D002021:Buffers; D006147:Guanine; D004247:DNA