English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The apparent on and off rate constants for binding of theophylline to its RNA aptamer in the absence of Mg(2+) were determined here by 2D (1)H-(1)H ZZ-exchange NMR spectroscopy. Analysis of the buildup rate of the exchange cross peaks for several base-paired imino protons in the RNA yielded an apparent k(on) of 600 M(-1) s(-1). This small apparent k(on) results because the free RNA exist as a dynamic equilibrium of inactive states rapidly interconverting with a low population of active species. The data found here indicate that the RNA aptamer employs a conformational selection mechanism for binding theophylline in the absence of Mg(2+). The kinetic data found here also explain a very unusual property of this RNA-theophylline system: slow exchange on the NMR chemical shift time scale for a weakly binding complex. To our knowledge, it is unprecedented to have such a weakly binding complex (K(d) approximately 3.0 mM at 15 degrees C) show slow exchange on the NMR chemical shift time scale, but the results clearly demonstrate that slow exchange and weak binding are readily rationalized by a small k(on). Comparisons with other ligand-receptor interactions are presented.

NMR Chemical Exchange as a Probe for Ligand-Binding Kinetics in a Theophylline-Binding RNA Aptamer