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Article

Diverse Polymorphism of G-Quadruplexes as a Kinetic Phenomenon

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Iztok Prislan, Jurij Lah* and Gorazd Vesnaver*

University of Ljubljana, Faculty of Chemistry and Chemical Technology, A

ker

eva 5, 1000 Ljubljana, Slovenia

J. Am. Chem. Soc., 2008, 130 (43), pp 14161–14169

DOI: 10.1021/ja8026604

Publication Date (Web): October 1, 2008

Abstract

Knowledge of forces that drive conformational transitions of G-quadruplexes is crucial for understanding the molecular basis of several key cellular processes. It can only be acquired by combining structural, thermodynamic and kinetic information. Existing biophysical and structural evidences on polymorphism of intermolecular G-quadruplexes have shown that the formation of a number of these structures is a kinetically controlled process. Reported kinetic models that have been used to describe the association of single strands into quadruplex structures seem to be inappropriate since the corresponding model-predicted activation energies turn out to be negative. By contrast, we propose here a novel kinetic model that successfully describes experimentally monitored folding/unfolding transitions of G-quadruplexes and gives positive activation energies for all elementary steps, including those describing association of two single strands into bimolecular quadruplex structures. It is based on a combined thermodynamic and kinetic investigation of polymorphic behavior of bimolecular G-quadruplexes formed from d(G₄T₄G₄) and d(G₄T₄G₃) strands in the presence of Na⁺ ions, monitored by spectroscopic (UV, CD) and calorimetric (DSC) techniques. According to our experiment and model analysis the topology of the measured G-quadruplexes is clearly flexible with the conformational forms that respond to the rate of temperature change at which global unfolding/folding transitions occur.

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Published In Issue October 29, 2008
Article ASAPOctober 01, 2008
Received: April 11, 2008

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Article

Diverse Polymorphism of G-Quadruplexes as a Kinetic Phenomenon