FIGURE 1.

Purification of DNA substrates. DNA substrates were annealed and end-labeled as described under “Experimental Procedures.” Substrates were next purified after separation by preparative polyacrylamide gel electrophoresis. A, OX-1 (bimolecular (n-2) and tetramolecular (n-4) forms as indicated), TP-B, and V4 G4 DNA substrates are shown. Unannealed single-stranded DNA is also marked. B, G4 DNA substrates with shortened 5′ single-stranded tails are indicated. Excised are denoted by the boxes.