Metal Ion Chelates as Surrogates of Nucleobases for the Recognition of Nucleic Acid Sequences: The Pd2+ Complex of 2,6-Bis(3,5-dimethylpyrazol-1-yl)purine Riboside

Table 2

The 𝑇_𝑚 of the duplexes formed between modified (7X) or unmodified (7A) oligonucleotide and complementary 2′-O-methyl-RNA (or DNA) sequences bearing A, G, U (or T), or C nucleoside opposite to the artificial nucleoside 1 (in the case of oligonucleotide 7X) or adenosine (in the case of oligonucleotide 7A) in the presence and absence of Pd²⁺; [oligonucleotides] = 3.0 μM, [K₂PdCl₄] = 0/3.0 μM, I(NaClO₄) = 0.1 M; pH = 7.4.

Complementary oligonucleotide	Sequence	𝑇𝑚/°C, duplex with 7X		𝑇𝑚/°C, duplex with 7A
		(5′-GCGCXCCGG-3′)		(5′-GCGCACCGG-3′)
		Pd^2+		Pd^2+
		+	−	+	−
8U	3′-CGCGUGGCC-5′	60.6±0.6	61.8±0.4	73.7±0.1	75.1±0.3
8A	3′-CGCGAGGCC-5′	61.6±0.1	61.4±0.4	56.3±0.1	56.3±0.2
8G	3′-CGCGGGGCC-5′	60.1±0.6	61.6±0.3	60.4±0.1	61.2±0.3
8C	3′-CGCGCGGCC-5′	59.9±0.4	60.7±0.2	58.8±0.2	59.0±0.2
9U	3′-CGCAUAGCC-5′	60.4±0.1	60.4±0.3	27.6±0.1	26.9±0.3
9A	3′-CGCAAAGCC-5′	61.7±0.9	61.0±0.9	44.3±0.6	43.6±0.7
9G	3′-CGCAGAGCC-5′	60.1±0.2	61.8±0.4	43.5±0.9	44.3±0.3
9C	3′-CGCACAGCC-5′	61.1±0.3	60.3±0.5	43.9±0.7	45.7±0.8
10T	3′-d(CGCGTGGCC)-5′	62.6±1.3	60.8±0.2	49.5±0.5	50.0±0.1
10A	3′-d(CGCGAGGCC)-5′	59.1±0.9	60.5±0.5	43.5±0.4	45.0±0.3
10C	3′-d(CGCGCGGCC)-5′	60.7±0.2	61.6±0.1	45.5±0.1	50.3±0.2
10G	3′-d(CGCGGGGCC)-5′	58.6±0.4	60.2±0.2	40.8±0.9	43.9±0.5