3.2.2. Oligonucleotide Substrates

The oligodeoxyribonucleotides were 50 -[32P]-phosphorylated with T4 polynucleotide kinase as described. Unreacted γ–[32P]-ATP was removed using MicroSpinTM G-25 column (Amersham Pharmacia Biotech, Little Chalfont, UK, and GE Healthcare, Chicago, IL, USA ). The 5 0 -[32P]-phosphorylated oligonucleotides were precipitated by 4% LiClO<sup>4</sup> in acetone and dissolved in water. Complementary oligodeoxynucleotides were annealed as described [6]. The following oligonucleotide sequences were used for the construction of DNA duplexes: whole strands 50 -(d)GGC TTC ATC GTT GTC TCA GAC CTG GTG GAT ACC G-30 ; upstream oligonucleotides 50 -(d)CGG TAT CCA CCA GGT CTG-30 with or without 50 -phosphate groups; downstream oligonucleotide 5 0 -p-(d)GAC AAC GAT GAA GCC-30 .
