Exceptionally slow kinetics of the intramolecular quadruplex formed by the Oxytricha telomeric repeat |
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Authors: | Brown Nicholas M Rachwal Phillip A Brown Tom Fox Keith R |
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Affiliation: | School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton, UKSO16 7PX. |
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Abstract: | We examined the stability and kinetics of folding of the Oxytricha telomeric repeat sequence (G4T4)4. Fluorescence melting experiments show that this intramolecular quadruplex, which is more stable in potassium- than sodium-containing buffers, shows considerable hysteresis between the melting and annealing profiles, even when heated at a rate of 0.05 degrees C min(-1). Quantitative analysis of this hysteresis, together with temperature-jump relaxation experiments show that the dissociation is exceptionally slow with a half-life of about 10 years at 37 degrees C in the presence of 50 mM K+. The association reaction has a half-life of a few seconds at 37 degrees C, but becomes slower at elevated temperatures consistent with the suggestion that association occurs by a nucleation-zipper mechanism. |
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