Synthesis and characterization of the diastereomers Λ- and Δ-[Ru(bpy)2(m-bpy-l-Arg-Gly-l-Asn-l-Ala-l-His-l-Glu-l-Arg)]Cl2

The diastereomeric complexes Λ- and Δ-[Ru(bpy)2(m-bpy-7p)]Cl2, (bpy = 2,2′-bipyridine, m-bpy-7p = 4-methyl-4′-Arg-Gly-Asn-Ala-His-Glu-Arg-CONH2-2,2′-bipyridine) were synthesized and characterized and their binding properties to the deoxynucleotide duplexes d(5′-CGCGATCGCG-3′)2 and d(5′-GCGCTTAAGCGC-3′)2 were studied by means of 1H NMR spectroscopy. 7p is part of the recognition loop of the restriction endonuclease MunI, a type II restriction enzyme from Mycoplasma unidentified which recognizes the palindromic hexanucleotide sequence C/AATTG and cleaves it as indicated by the slash. The Δ-isomer binds to the terminal CG/GC major groove of d(CGCGATCGCG)2 decanucleotide, whereas the Λ-isomer approaches the GCT/CGA sequence. On the other hand, weak binding of the Δ-isomer to the end of d(GCGCTTAAGCGC)2 into two different orientations is observed. In the case of the Λ-isomer, the bpy ligand(s) are located into the major groove of the central TT/AA sequence. The role of appended peptide sequences in sequence selectivity binding to DNA is being addressed.