Table 2. Thermal Denaturation Transitions of Duplex 4:7, Recorded at 260 nm^a.

duplex 1:5				duplex 4:7
entry	[NaCl]	[MgCl2]	Tm	entry	[NaCl]	[MgCl2]	Tm	Tm2
12	10 mM		39.7 ± 0.7	19	10 mM		< 30
13	100 mM		47.6 ± 0.5	20	100 mM		42.9 ± 0.6
14	820 mM		57.2 ± 0.4	21*	700–800 mM		65.4 ± 0.9
				22*	1.1		57.2 ± 1.2	72.6 ± 0.5
15	4.3 M		58.6 ± 0.5	23	4.1 M		55.1 ± 01.5
				24	10 mM	5 mM	< 30
16	100 mM	5 mM	61.6 ± 0.5	25	100 mM	5 mM	31 ± 0.8
17	650–800 mM	5 mM	60.2 ± 0.8	26	650–800 mM	5 mM	28.2 ± 1.1
18	3.5–4.2 M	5 mM	55.2 ± 0.6	27	3.5 M	5 mM	nd

^aAll measurements were carried out in duplicate. Samples of all traces are provided within Supporting Information (Figures S27–S30); entries with a < sign did not display a clear sigmoidal shape. [RNA duplex] = 2.5 μM, [Na₃PO₄] = 10 mM, pH 7.2. Entries with a (*) indicate instances that display increased thermal stability, compared to the canonical analogue.