Substrates and standards

Nucleotides

5',3'-ApC, 3'-AMP, 2',3'-cAMP, Cytidine, 5',3'-GpC, 3'-GMP, 2',3'-cGMP were from Sigma, Deisenhofen, Germany

R/8 oligonucleotide

The 8-mer oligonucleotide was customly synthesised by NAPS, Göttingen, Germany. R/8 has the sequence