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. Author manuscript; available in PMC: 2015 Dec 29.
Published in final edited form as: J Am Chem Soc. 2003 Dec 10;125(49):15021–15027. doi: 10.1021/ja037616j

Figure 2.

Figure 2

(a) Determination of stoichiometry by gel filtration chromatography on an analytical Synchropak GPC 100 column with the elution buffer being 70 mM KCl and 20 mM potassium phosphate, pH 7, at room temperature. The known number of residues of several nucleic acid reference samples (in black) (including single-stranded oligonucleotides, duplexes, and quadruplexes) is plotted in log scale as a function of the elution time. The straight line is interpolation through these data. The elution time of U6 and U1B7 (~1 mM) is consistent with a molecular size of 24 nucleotides, corresponding to a dimer (open data point with open arrow). The elution time of heated diluted samples of U6 and U1B7 (~1 µM) is consistent with a molecular size of 12 nucleotides, corresponding to a single strand (open data point with black arrow). (b) Determination of stoichiometry by NMR titration of the equilibrium strand concentrations of the multimer structure and of the unstructured monomer. Squares and triangles represent U6 and U1B7, respectively. Lines of slope 2 are drawn through the data points. Insert: Proton spectra of U6, showing the peaks of the structured form (grey) and the peaks of the unstructured single strand (black), whose relative intensities are dependent on DNA concentration. Experimental conditions: temperature, 50 °C; 70 mM KCl; potassium phosphate, 20 mM; pH 7.