TABLE 1.

pK_a values for functional groups related to those of an RNA phosphodiester

The three rate-determining pK_a values for spontaneous RNA degradation due to specific acid and base catalysis are as follows: pK_a1 defines protonation at the 5′-oxygen; pK_a2 is for the first NBPO; and pK_a3 relates to protonation of the 2′-oxygen from the oxyanion to a hydroxyl. The pK_a values are listed for the functional groups depicted in italics. Values in bold type were determined experimentally, whereas the remainder are estimates. W indicates adenosine or uridine.