Table 1. Substrates used in steady-state assays.

Abbreviation	Sequence
1U	5′-GAC TAP UAA TGA CTG CG-3′
1U·A (X = A)	5′-GAC TAP UAA TGA CTG CG-3′
1U·G (X = G)	3′-CTG ATT XTT ACT GAC GC-5′
2U	5′-GAG GCP UCC ACG CTG CG-3′
2U·A (X = A)	5′-GAG GCP UCC ACG CTG CG-3′
2U·G (X=G)	3′-CTC CGC XGG TGC GAC GC-5′

Oligonucleotides were synthesised containing the fluorescent base 2-aminopurine (P), as indicated, and the double-stranded substrates were made by annealing the appropriate strands. U, 2′-deoxyuridine.