A versatile approach towards regioselective platinated DNA sequences

Undesired N(7) platination of 2'-deoxyguanosine residues at predetermined sites in an oligodeoxynucleotide (ODN) sequence is prevented by applying the sterically demanding diphenylcarbamoyl (DPC) as an O(6)-protecting group. The presence of a base-labile oxalyl linker between the immobilized 3'-nucleotide and controlled pore glass (CPG) allows cleavage of the protected ODN from the support and leaves DPC protection unaffected. This method provides an ODN with specifically blocked guanine-N(7) sites for platination. In the hexanucleotides prepared in this study, 5'-GGBGGT-3'(for B=T, C and A), a platinum GG adduct is introduced at G4,G5. These site-specific platinated hexamers were isolated in a yield of 65 %, and were fully characterized by using reversed-phase HPLC (high performance liquid chromotography), LCMS (liquid chromatography-mass spectrometry), MALDI-TOF MS (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry), PAGE (polyacrylamide gel electrophoresis) and Maxam-Gilbert sequencing analysis.