Figure 2.

Co-precipitation experiments on carbonate minerals for RNA-binding competition. The precipitated column formed by two carbonates and containing radioactive RNA (left, see text for details) is exposed to a phosphorimager screen to observe RNA localization in the column (A). For each pair, carbonates are either prepared separately and then mixed together (“xCO₃ + yCO₃”, first column per pair), or all the ingredients are co-precipitated (“xyCO₃”, second column per pair). Subsequently (B), columns xCO₃ + yCO₃ are frozen, cut in slices, and the radioactivity in each slide plotted versus the column height in cm. Columns for the pair Ba–Mg and Sr–Ca could not be frozen and sliced due to their high lability; their autoradiograms were profiled instead for RNA localization (data not shown). Carbonate density: CaCO₃ 2.71 g/cm³ < MgCO₃ 2.96 g/cm³ < SrCO₃ 3.5 g/cm³ < BaCO₃ 4.29 g/cm³.