FIGURE 3.

Results from typical cross-linking experiments. (A) Autoradiogram of an 8% PAGE gel for experiments performed using a 5′ end-labeled, noncleavable substrate (SdA-1s⁴U-2) and the ribozyme. The various conditions tested are indicated at the top of the gel. The positions of the xylene cyanol (XC), the bromophenol blue (BPB), and substrate (S) are indicated. The inset illustrates a longer exposition of the region including the cross-linked species. (B) Autoradiogram of a typical 10% sequencing gel performed for the NaOH mapping of the cross-linked species. Lane 1 is a partial RNase T1 hydrolysis in order to identify the guanosines, and lane 2 is the partial NaOH ladder of the ribozyme alone. Lanes 3 and 4 are partial NaOH hydrolyzes of the X1 and X2 species, respectively. The positions of the guanosines are indicated on the left, while those of the cross-links are indicated on the right.