Figure 2.

Deuterium KIE on hydroxyl radical cleavage of the SRL. (A) For 5′-radiolabeled RNA, the major cleavage product is a strand, terminated by 3′-phosphate, that is missing the nucleotide that was attacked by the hydroxyl radical. Gel bands are therefore identified by the nucleotide that was attacked, and not by the nucleotide at the strand terminus. (B) Shown are overlaid scans of gel lanes in which were separated cleavage products of SRL containing all natural nucleotides (gray), and SRL in which [5′,5″-²H₂]-adenosine had been incorporated (black). The SRL was radiolabeled at the 5′ end. Major peaks represent cleavage products terminated by 3′-phosphate. Substantial decreases in cleavage upon deuteration occur only for products of cleavage at adenine residues.