Table 3.
The Tm [°C] and thermodynamic data at 298 K for the antiparallel duplexes at different NaCl concentrations, taken from UV melting curves (λ = 260 nm).a
| antiparallel duplex | NaCl (mM) | Tm (°C)b | ΔHc (kJ/mol) | TΔS (kJ/mol) | ΔG298 (kJ/mol) | |
| ON/DNA | ON1/ON20 | 25 | 19 | −430 (±20) | −400 (±20) | −30 (±28) |
| 50 | 37 | −400 (±9) | −350 (±8) | −50 (±12) | ||
| 100 | 50 | −368 (±8) | −305 (±7) | −63 (±10) | ||
| 4N+ON7/ON20 | 25 | 41 (+22.0) | −388 (±9) | −334 (±8) | −54 (±12) | |
| 50 | 44 (+7.0) | −322 (±15) | −266 (±14) | −56 (±20) | ||
| 100 | 51 (+1.0) | −320 (±8) | −260 (±7) | −60 (±10) | ||
| 4Ts-ON13/ON20 | 25 | 29 (+10.0) | −382 (±14) | −340 (±14) | −42 (±19) | |
| 50 | 34 (−3.0) | −372 (±12) | −326 (±11) | −46 (±16) | ||
| 100 | 45 (−5.0) | −354 (±7) | −297 (±7) | −57 (±10) | ||
| ON/RNA | ON1/ON19 | 25 | 44 | −390 (±10) | −332 (±9) | −58 (±13) |
| 100 | 46 | −306 (±17) | −248 (±17) | −58 (±24) | ||
| 4N+ON7/ON19 | 25 | 45 (+1.0) | −419 (±7) | −359 (±6) | −60 (±9) | |
| 100 | 55 (+9.0) | −329 (±13) | −264 (±12) | −66 (±17) | ||
| 4Ts-ON13/ON19 | 25 | 38 (−6.0) | −420 (±20) | −370 (±20) | −50 (±28) | |
| 100 | 53 (+7.0) | −407 (±13) | −337 (±12) | −70 (±17) | ||
aOne µM of each strand in 20 mM sodium cacodylate buffer (pH 7.0, supplemented with 25, 50, or 100 mM NaCl, respectively); bTm values are reported with ±0.5 °C uncertainties as determined from several experiments; values in parentheses are ΔTm values calculated as Tm (sample) − Tm (unmodified duplex) at the same salt concentration; cthermodynamic parameters are calculated as described in Supporting Information File 1 (see also Figures S9–S14) at 298 K, errors were calculated as described in reference [44].