Exo III digestion of oligonucleotides with phosphorothioate linkages. Denaturing (7 M urea) PAGE showing: (a) Digestion of a 5′-overhang dsDNA comprising 5′-32P-labeled G*-2S-30, C*-2S-32 and the corresponding template, C-51-Temp, G-51-Temp; negative control lanes of undigested G*-2S-30 and C*-2S-32, UDG and UDC, respectively, are indicated. The 30-mer and 32mer used as a marker is the material present at t = 0 min [see also (b)]; (b) digestion of blunt-end dsDNA comprising 5′-32P-labeled G*-2S-51, C*-2S-51 and the corresponding template, C-51-Temp, G-51-Temp; negative control lanes of undigested G*-2S-51 and C*-2S-51, UDG and UDC, respectively, are indicated. Lanes 1, 2, 3 and 4 indicate 2, 5, 15 and 30 min Exo III digestion. Units/µl (2.5, 1.0, 0.5 and 0.25) above lanes indicates the concentration of Exo III used.